geothermal convertion and economic

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I

ENERGY CONVERSION AN D ECONOMICS FOR

GEOTHERM AL POWER GENERA TION AT

HEBER, CA LIFO RNIA , VAL LES CA LDERA , NEW MEXICO,

A N D R A F T R IV E R , I D A H O - CASE STUDIES

EPRl ER-301

(Research Project 580)

Topical Report

2

November 1976

Prepared by c \ g 3 y

HO

T/PROCON

(A Joint Venture of The Ben Hol t Co. and Procon Incorporated)

201 South Lake Avenue

\



LEGAL NOTI CE

Thi s r epor t was pr epar ed by Hol t / Pr ocon (a J oi nt Vent ure of The Ben

Hol t

Co.

& Pr ocon I ncor por at ed) as an account

of

wor k s ponsor ed by

t he El ect r i c Power Resear ch I nst i t ut e , I nc . (EPRI ) . Nei t her EPRI ,

members of EPRI , Hol t / Pr ocon, nor any pers on act i ng on behal f of

e i t her : (a) makes any warr ant y or r epr esent ati on, expr ess or i mpl i ed,

wi t h r espect t o t he accur acy, compl eteness, or usef ul ness

of

t he

i nf ormati on cont ai ned i n t hi s r epor t , or t hat t he use of any i nf ormati on,

apparat us, method, or pr ocess di sc l osed i n t hi s r eport may not i nf r i nge

pr i vat el y owned r i ght s; or

(b)

assumes any l i abi l i t i es wi t h r espect t o

t he use

o f ,

or f or damages r esul t i ng f r omt he use of , any i nf ormat i on,

apparat us, method, or pr ocess di sc l osed i n th i s r eport .



ABSTRACT

This

repor t presents a porti on of t he re su lt s from a one-year study

sponsored by th e El ec tr ic Power Research In s t i t u t e

( E P RI )

to a ssess

the fea s ib i l i ty of cons truc ting a 25-50

MWe

geothermal power plant

using low-salinity hydrothermal fluids

as

the energy source.

The ove ral l objectiv e of the proj ect w a s t o assess th e tech nical , geo-

te ch ni ca l, environmental and economic f e a s i b il i ty of producing

el ec tr ic i t y from hydrothermal resources l ik e those known t o e xi st in

the Uni ted 'Sta tes . The object ive of th is repor t

w a s

to inves t iga te the

compat ib i l i ty

of

the di ff er en t power conversion options with re a l

geothermal re se rv oi rs and t o analy ze th e economics of power

generation.

Three sets of conversion technology are considered for the near term:

flashed steam, bina ry, and hybrid (flash ed steam/binary). Reservoir

and geothermal f lu i d cha ra ct er is tic s have a very s tro ng influ ence on

(1) th e choice of conversion technology, ( 2 ) performance and l i f e of

mate r ia l s and components,

( 3 )

necessary environmental co nt ro ls , and

(4) the ult im ate co st of generating power.

A l l

of th ese fac to rs are

in te rr el at ed , and th e decisio n logic fo r optimum choice has not ye t

been developed.

This re po rt di scus ses nine cases which were chosen t o yi el d f ur th er

i n s i g h t i n t o t he e f f e c t of res erv oir temperature on the choice of

convers ion technology and power co s ts . These ca se s examine fl as he d

steam, binary cycle and hybrid conversion for R a f t River, Idaho;

Heber, California; and Valles Caldera, N e w Mexico t h a t have bottom-

hol e temp eratu res of approximately 150

C , 180 C

and 260

C

res pe cti ve ly. Conceptual layo uts of th e power conversion proc esse s,



"Comparison of Hydrothermal Reservoirs in the Western United

Sta tes

"Reserv oir Engineer ing and Aspec ts of G eothermal Si te Select ion

at He ber , Cal i fornia and Val les C aldera , New Mexico ''

"Energy Conversion and Economics for Geothermal Po wer

Generat ion

at

Heber, California; V a l l e s Cald era, New Mexico;

and Raf t Riv er , Idaho

-

Case Studies ' '

"P re l im inar y Env i ronmenta l Ass essm ent of Geo thermal Power

Generat ion at Heber , California and V a l l e s Caldera, New Mexico"

"Geotechnical E nvironmenta l Aspec ts of Geothe rmal Power

Generat ion at Heber , Cali fornia"

I 'Socioeconomic Environmental Aspects of Geothermal Power

Generat ion

at

Heber

,

California"



c3

TABLE O F CONTENTS

S

UMMAR Y

Table 1 - Ene rgy Convers ion Study

INTRODUCTION

METHOD O F APPROACH

DESIGN CRITER IA

POW ER CONVERSION OPTIONS

SELECTION O F PLANT SIZE

HEAT REJE CTION OPTIONS

FLASHED STEAM PROCESS

THE BINARY PROCESS

THE HYBRID PROCESS

P a g e

1

8

9

11

13

16

18

20

25

27

HEBER CONVERSION PLA NT S 28

Draw ing No. 7523-D-3204B, Fla sh ed

Steam

P o w e r P l a n t 4 1

Draw in g No. 7523-D-3205A,

Binary Power P lan t 42

Dr aw ing No. 7523-D-3241A, Binary Powe r P lan t 43

Dr aw ing No. 7523-D-3208B,

Hybr id Powe r P lan t 44



P a g e

74

Table

3 -

Case Study Sum ma ry, Heber Res erv oir 76

Table 4 - Case S tudy Sum mar y , Val les Ca ldera Rese rvo i r 77

Table

2

-

Computer Sample Pr in tou t

Table

5 -

Case S tudy Sum mar y ,

Raf t R iver Reservo i r

ECONOMIC FEASIBILITY

Figure 5

-

E s t ima te S ummary , B ina ry

F igu re

6

- E s t i m a t e S u m m a r y , F l a s h

Figure 7 - E s t im a te S ummary , H ybr id

Figure 8 - Est im ate Sum mar y , B inary , P roduc t ion &

Injection

Table

6 -

Est imated Power P lan t and Transmiss ion

Table 7

-

Est im ated In i t ia l F ie ld Capi ta l Cos ts

Table 8

-

Est im ated F ie ld S taf f Cos t

Table 9

-

Est im ated F ie ld Operat ing and Main tenance

Table 10 - E s t ima ted P ow er P lan t L abo r C os t

Table 11 - Estimated Plant Operat ing and Maintenance

Table 12

-

Computer Pr in tou t

-

G eo the rma l P ro jec t

Table 13

-

E s t ima ted G eo the rma l P ow er C os t

-

Base

Table 14 - Sensi t iv i ty Analysis

-

G eo the rma l P ow er

Capi ta l Cos ts

c o s t

c o s t

E conomics

C a s e

78

79

94

95

96

97

98

99

100

101

102

103

104

106

107



SUMMARY

SUMMARY

O F

RECOMMENDATIONS

On the strength of this study, the Heber g eoth erm al f ield in California

i s r ecommended a s the bes t s i te fo r a low-sa l in i ty hydro the rm al

demon stra t ion plant .

power conversion sy st em should be based on the binar y cy cle, and the

cap aci ty of the pla nt should be in the 50 MWe range.

If a dem onstra t ion plant i s cons t ruct ed , the

SUMMARY O F CONCLUSIONS

1 .

2.

3 .

I t i s feasible to proceed with the des ign, construction and

operation of a 50 MWe hydroth erm al power plant with r easo nabl e

expectation of su cc es s, but not without som e tec hnica l and

e c on o mic r i s k s .

normal ly t ake

,

but i s acceptable as a "f i r s t -of-a-kind" re se ar ch

and development undertaking.

The risk is greater than what a uti l i ty might

Of the geo the rmal re se r vo i r s s tud ied in de ta il , demons t ra t ion

plants appe ar to be technically and environmentally feasible at

Heb er , Cal i fornia ; Val les Ca ldera , New Mexico and Raft Ri ver ,

Idaho; and economically feasible at Heber and Valles C ald era .

Heber i s the bes t a l l -around choice for the demonstra t ion s i te ,

because the character is t ics of the geothermal f lu id contained i n



7.

8 .

9 .

There ap pear to be no overr id ing environmenta l const ra in ts ;

however , pres ent data and analyt ica l techniques a r e not adequate

to fully evaluate sei sm ici ty, subsidenc e and hydrogeology

.

The

impact in each cas e is es t imated to be sma l l , and the es t im ate s

a r e thought to be conservat ive .

A comm erc ia l s i ze demons t ra t ion p lan t with a r es ea rc h and

development or ienta t ion dur ing the ear ly l ife

of

the plant, followed

by com me rcia l opera t ion af ter debugging is complete , i s needed to

reso lve the p rob lems of technology adaptation and optimization,

heat exchanger and turbine scale -up, ma ter ia l s , and scale control .

I t i s a l so needed to ve r i fy res e rv o i r pe r fo rmance mode ling

techniques and to study geotechnical environ mental a spe cts of

geot herm al product ion

.

Dry cooling and wet-dry cooling would impose a severe cost

penalty

i f

used .

S UMMAR Y OF

RESULTS

In October 1975, the Ele ct r ic P ower R ese arc h Ins t itu te author ized

Hol t /Pro con to make a feas ib i li ty s tudy for a low-sal in i ty hydrothermal

demonstra t ion plant .

economic and environmenta l feas ib i li ty in the 1980 t im e f ra m e and, i f

supported by the f indings, to recom me nd a si te for the construction

of

a 25 MWe to

50

MWe g eot her ma l power plant and a p ro ce ss upon which

to base the des ign.

The objective

of

the study was

to

a s s e s s t e c h n ic a l ,



power p lant pe r kw inc r eas es a t l eas t 50% over the cost

of

a plant

employing wet cooling.

It is concluded that a 50 MWe plant should be buil t, just ifie d on the

ba si s that the c ost of power fr om a s m al le r plant would probably not

be comp eti t i ve. The cost of power fro m a

2 5

MWe plant is expected

t o be 20% higher than the co st for a 50 MWe plant, resu lt ing in an

uneconomic installat ion.

The approach in determining technical and economic feasibil i ty was to

exam ine the th re e con version options at the thre e si te s (a total of nine

ca se s) a t a net power output level of

50

MWe, using wet cooling to w er s.

Net power i s the genera tor output le ss the paras i t ic power r equ ired

for pum ps and cooling tow ers , but excluding the power req uir ed to

pump and re i n jec t the geotherm al flu ids .

Conceptual engineering design work was ca rr ie d out - for each of the

n ine base c ase s as a bas i s upon which to p repare rea l i s t i c e s t i ma tes

of the capital cost for eac h ca se , for the power plant, the field

ins ta l l at ion and the t r ans mi ss io n l ines .

In th is s tudy deta i led capi tal cos t es t im ate s were prep ared for the fie ld

p lan t and t ran sm iss io n cos t s a t Heber .

adjus ted for the Val les Cald era and Raf t River ca ses to ref lec t d i f ferences

in des ign and locat ion.

opera t in g and maintenance cost es t im ate s for f ie ld , p lant and t r an s-

mi s s i o n l i n e s .

These es t im a tes were then

This work was followed by the preparation of



Brin e flow at the s ta r t

is

in the ran ge of 1. 2 M k g/h r to 1 . 8 M kg /hr

( 2 . 6 to 4 .0 M lb s / h r ) a t Va l les Ca ld e ra depend ing upon the p roc ess .

The flows a t Heber vary f r om 3. 1 M k g / h r t o 4 .5 M k g / h r

( 6 . 9

to

10 M lb s / hr ) , while a t Raft River the f lows vary f ro m 5 M kg/hr to

7 . 4 M k g / h r ( 1 1 .

0

to 16. 3 M l b s / h r ) .

The lea s t number of producing and injec tion wel ls a r e re quire d a t

Valles Cald era (13 -17) , fo l lowed by Heber (18-24) and by Raft R iver

(25-37) .

Brine consumption is lowes t fo r the b ina ry p roce ss a t a l l th ree

re se rv o i r s . Br ine flow i s lowes t

at

Valles Caldera , 24 kg/kwh

(52 lbs /kwh ) , inc reas ing to 63. 2 kg/kwh (139 lbs /k wh ) at Heber and to

100 kg/kwh ( 2 2 0 lbs /kwh ) a t Raf t R iver .

b ina ry and s team f lash b r ine consumpt ion inc re ases a s the re se rv o i r

t e m p e r a t u r e d e c r e a s e s .

The difference between

Pa ra s i t i c power consumpt ion fo r thk s team f lash ca ses v a r ies f ro m

670 to 12% of net power output a s com pare d to

a

range of 27% to 3570 fo r

the b inary cycle .

Fie ld development cos ts for the b ina ry and f lashed s t eam plants

( including wel ls , pumps and surfa ce ins ta l la t ion s) a r e lowest a t Heber

($236 /kw and $287/kw ) reflecti ng the relat ively high fluid production

p e r wel l and re la t ively low wel l cos t .

Cor respond ing cos t s

at

Valles

Ca lde ra a r e $336/kw and $406/kw and at Raft Riv er $590/kw and

$845/kw. The bina ry f ie ld cost s ar e consis tent ly lower than the

f lashed s team cos t s .



1.

2.

3 .

4.

5.

6 .

7.

8.

9.

P r o j e c t l i f e - 25 y e a r s .

D C F ra te of re tu rn to the produ cer , based on the c ost of f ie ld

development - 1570.

Depletion (22700)and write-o ff of intangible dri l l ing c os ts taken into

a ccount.

Royalty. - 12. 570of fuel cost.

Ad v a l o r e m t a x es - 10. 070of pro du cer 's fuel cos t and 2.

570

of

ut i l i ty 's capi ta l cos t .

Ut il i ty r e t ur n on investm ent

-

1270.

Fif ty-f i f ty u t i l i ty debt /equi ty ra t io .

Ut il ity in te res t r a t e

-

970.

Inves tment tax c red i t of 1070.

The projec ted co st of power at Valles Caldera i s probably unders ta ted

because we as sum ed , l ack ing spec i f i c in fo rmat ion to the con t ra r y ,

that cool ing wa ter could be made avai lable a t a min imal cos t , tha t the

noncondensable content of the res er vo ir f luid wa s nominal, and that

the cor r os io n and sca ling ch arac te r i s t i c s of the b rine ' we re s imi la r to

Heber .



Near t e r m al te rnat iv e new power avai lable in the Southwest wi l l

probably be based on e i ther coal- f i red o r o i l - f i red power p lants and

will c ost in the ra nge of 30-35 mil l s /kw h. I t appe ars that a 5 0 MWe

bina ry cycle p lant can be bui l t a t Heb er to supply power at

a

cos t

within this range.

T h e r ma l e f f ic i e nc i es ,

i. e. ,

he ra tio of ne t heat conve rted to el ec-

t r i c i ty t o h e a t e x t r a c t e d f r o m t h e b r i n e ,

do no t v a r y f r o m c a s e t o c a s e

n e a r l y a s much a s bri ne consumption.

Heber binary to 14.

86'30

fo r the Va l les Ca lde ra f l a sh case .

cas es the hybr id and f l a sh p ro ces ses a r e s l igh tly mor e e f fi c ien t than

t h e b i n a r y p r o c e s s .

at

a l o we r t e mp e r a t u r e t h a n t he f l a s h p r o c e s s , t h e r e b y mo r e t ha n

compensat ing for the los s in ef f ic iency.

The range i s 9.867' fo r the

In a l l

However , the b ina ry p ro ces s re je c t s spen t b r ine

Techn ica l weakn esses a r e a ssoc ia ted wi th the b ina ry cyc le and include

the l ack of exper ience in the des ign and opera t ion of la rg e hydrocarbon

expa nder s , pro ble ms asso cia te d wi th down-hole pumping which have

not been fully resolve d, and la ck of lon g-ra nge bri ne scalin g and

co rro s io n data. None of t h e s e c o n s t r a i nt s a p p e a r t o be of sufficient

magni tude to wa rr an t delay of des ign and constru ct ion of the power

plant.

T h e He b e r r e s e r v o i r me e t s a l l th e c r i t e r i a f o r f ea s ib i l it y .

good match fo r the re prese n ta t iv e low sa l in i ty re se rv o i r

a s

developed

in Geonomics ' work.

f o r

3 0

ye ar s o r more . The re a r e su f fic ien t da ta upon which to base

re l i ab le e s t im a tes of r e s e r vo i r s i z e and p roduc t ion charac te r i s t i c s .

I t i s a

It

is

la rg e enough to suppor t

a

200

MWe operation



The binary cycle p lant produces power

at

a lower cos t than the s tea m

f las h cyc le

at

Heber . Mo reove r , our s tudies show that the d i f ference

i n c r e a s e s a s r e s e r v o i r t e m p e r a t u re d e c r e a s e s .

The success fu l

dem onstr a t ion of a b inary cycle pr oc es s a t Heber wi l l be widely

a p pl ic a bl e t o t h e l a r g e me d i um t e mp e r a t u r e g e o t h e r ma l r e s o u r c e b a s e .

Th ere for e , we a lso recomm end that the conceptual des ign s tudies be

base d upon the b ina ry cyc le r a th e r than the f l a shed s te am cyc le.



THE RESERVOIR

R e s e r v o i r T e m p e r a t u r e , F

Producing Well Capaci ty ,

K

l b s l h r

No. of Wells , S tar t of Produc t ion

Injec t ion Well Capaci ty , K l h s l h r

No. of Wells , S tar t of Produc t ion

Product ion and Injec t ion Well Cos t . K

To ta l F i e ld C a p i t a l Co s t , M

O &M C o s t , F i e ld ,

K

/ y r

TH E PO W ER PLA N T

W e t B u lb Te mp e ra tu re , F

B r in e C o n s u mpt io n , M Ib s l h r , s t a r t

Ib s lk w h

B r i n e T e m p e r a t u r e , O u t, 'F

T h e r m a l E f f i c i en c y , 7

G e n e ra to r O u tp u t, k w

Pu mp in g W o rk , k w

Cooling Tow er Work, kw

N e t Po w e r , k w

Pla n t C o s t , M

Pla n t O &M C o s t .

K

/y r

TRANSMISSION COST, M

OVERALL COSTS

Fie ld D e v e lop me n t , / k w

P o w e r P l a n t , / k w

T r a n s m i s s i o n ,

1

kw

F u e l C o s t s , m i l l s / k w h

P l a n t F i x e d C h a r g e s , m i l l s l k w h

Pla n t O &M, mi l l s / k wh

T r a n s m i s s i o n C o s t , n , i l l s/ k w h

TOTAL POWER COST, mil l s /kwh

BINARY

360

650

12

1 , 3 0 0

6

300

1 1. 8

1,973

80

6. 942

139

154

11.75

64. 3

9 . 5

4 . 8

50 . 0

28. 5

1 , 2 0 0

0. 500

236

570

10

1 6 . 6 9

15.03

3.22

0. 28

3 5 . 2 2

TA B LE 1

ENERG Y CONVERSION STUDY SUMMARY

H EB ER

FLASH HYBRID

VALLES CALDERA

BINARY FLASH HYBRID

Isopentane

R A FT R IV ER

FLASH HYBRID

INARY

300

650

19

1.300

9

600

29. 5

2.953

65

11.00

220

145

9. 86

67 . 5

15. 9

1.

50 . 0

32. 3

1 , 3 3 1

3.600

590

646

72

32 .80

16.83

3.57

1.97

55.17

Note: M

=

mi l l i o n s a n d

K =

thousands



INTRODUCTION

This repor t

i s

one of the documents which has bee n pre par ed a s a pa r t

of the feas ibili ty study fo r

a

low sa l in i ty hydrotherm al dem onstra t ion

plant.

P a r t A of the study consist s of the as se ss m en t of the technical ,

econom ic and env ironmen tal feasib il i ty of

a

25

to

50

MWe plant in the

Heber a re a of the Im per ia l Valley and the Val les Cald era ar ea of New

Mexico, using state-of - t he -a rt technology.

Also inc luded in P a r t A i s a pa ra l l e l t echn ica l and economic (no t

envi ronm enta l) study of the Raft Riv er, Idaho, re se rv oi r , which we have

taken to be representa t ive of a low temperature 149

C

( 3 0 0 F ) r e s e r v o i r .

By se lec t ing Raft Rive r a s a r epre sent a t ive s i te in addi tion to the o ther

si tes, we have accomplished another objective:

i.

e. , the development

of the cap i ta l and opera t ing co sts associa ted wi th three d i f ferent

p r o c e s s e s at t h r e e r e s e r v o i r t e m p e r a t u r e s .

to be the ho tte s t r e s e rvo i r :

2 6 0

C (500 F ) , followed by He ber: 182 C

(360 F ) and then by Raft Rive r:

149

C (300

F).

Valles Caldera i s thought

The economic analys is resul t ing f r o m this work provides ins ight as to

the re la t iv e m er i t s of f lashed s te am and binary cycles wi th varying

res e rv o i r t em pera tu res and p rov ides use fu l in fo rmat ion re la t ing power

g e n e ra t io n c o s t s t o r e s e r v o i r t e mp e r a t u r e .



c

ASK 3 SYSTEM REQUIREMENTS

The response to

this

t a s k

i s

contained in

a

sepa ra t e H ol t /P rocon r e po r t

entitled "Plant Requirements Manual".

TASK

4


The response to this t a s k

is

contained in th is report .

TASK 5 - ENVIRONMENTAL FEASIBILITY

The response to this t a s k i s contained in a sepa ra t e r epo r t p repa red by

Pr oc on (with input by Geonomics, Inc. , en t i t led "Pre l iminary

Environmenta l As s

e

s srnent"

.

TASK

6

- RESERVOIR SE LECTION

A l l of the foregoing r ep or ts including this one pres en t data which affect

the selec tion of

a

r e s e r v o i r .

per t inen t fac to r s a f fec ting re ser vo i r se lec tion , toge ther with a

recommended reservo i r se lec t ion .

T h i s r epo r t p re sen t s an ana ly s i s

of

the

TASK 7 - IDENTIF ICATION O F TECHNOLOGY WEAKNESSES



M E T H O D O F A P P R O A C H

The method of appr oach in conducting the en erg y convers ion s tudy i s

a s fo llows:

1.

Avai lab le da ta we re as sem bled fo r each s i te and , when not

ava i lab le , reasonable es t imates w er e made. Such data included:

a.

b.

R ese rvo i r t em pe ra tu re and chemica l compos it ion .

Noncondensable content and anal ysi s of re se rv oi r f luid .

c.

d. Well prod uctiv ity, depth, spacing and cost.

Corr os ion and sca l ing cha rac te r i s t i cs of the res e r vo i r f lu id .

e.

Me teo ro logica l da t a , p r i ma r i ly w e t and d ry bu lb t em pe ra t u re

of air.

f .

Pl an t locat ion and elevat ion.

g. Soil conditions.

h. Applicable bui lding code s, including envi ronm ental controls .

i.

Availability and cost of util i t i es.



Plo t p lan

Major equipment specif ica t ions

Electr ica l s ingle- l ine drawings

This w as done both fo r the f ield and the plant instal lat ions.

4. Vendors ' quota t ions w er e sought fo r

all

m aj or equipment. We

evaluated the offer ings and made equipment se lec t io ns which w er e

incorpora ted on the P& I d iagrams . The cos t quota tions we re used

in es t imat ing.

5.

The foregoing documents wer e turned over to the es t i ma tor s who

prepared ins ta l l ed cos t e s t ima tes .

supplemented by our es t im ate s of opera t ing costs , we re used in the

est im ate of the c ost of power d elive red to a load center .

The cap i ta l cos t e s t im a tes ,

6.

Next a c om pute r pr o gr am was developed, the output of which was

t he cos t

of

ge o t h e r m a l pow e r d e l i ve r e d t o a loa d c e n t e r .

pr og ra m computed the se l l ing pr ic e of ener gy to the u t i l ity u t il iz ing

the cos t-o f - se rv ice approach in accordan ce with genera l ly accep ted

pra ct i ce in the o i l industry . The cost of conv ers ion was ca lcula ted

employing the methods genera l ly used by the investor-owned publ ic

ut il i ty . The cost of power wa s es t im ated for all nine cases ,

and a

sensi t iv i ty ana lys is pe rfo rm ed to evaluate the effec t of changing

key variables.

T h e



POWER

CONVERSION OP TIONS

The con vers ion of hydr o ther mal energy f r om a l iqu id-dominated

geo the rma l r e so u rc e in to e l ec t r i c pow er can be accompl i shed by the

fol lowing meth ods:

T he f l a s he d s t e a m p r o c e s s - in which a pa rt of the geo the rm al f lu id

i s

f l a shed into s t eam in one o r m or e s t ages .

duce e lec t r ic power by mea ns of a tu rb ine and gene ra tor .

T he s t e a m

i s

u s e d t o p r o -

T he b i n a r y p r o c e s s

-

i n w hich the the rm a l ene rgy in the b r ine

i s

t r a n s fe r r ed in to a p re s su r i ze d in t e rmed ia t e f lu id , such a s i sobu tane ,

which

i s

expanded through a turb ine to prod uce power.

then condensed and pumped up to i€ s in i t ia l p re ss ur e

s o

that

it

can be

recyc led th rough the sys tem.

The fluid

i s

T he hybr id p ro ces s

-

in which

a

pa r t of the b r ine i s f lashed in to s tea m

which

i s

used to d r ive

a

s t e am tu rb ine. T he r e s idua l hea t i n the b r ine

i s t hen t r an s fe r r e d to a n in t e rmed ia t e f luid w h ich i s u sed to d r ive a

second tu rb ine us ing the b inary p ro ces s .

T o ta l f low p ro ces se s S eve ra l

of

t he se p roc es s e s a r e under deve lop -



c

h e ma j o r t e c hn i c al p r o b l e ms a s s o c i a te d wit h t he s t e a m f l a s h p r o c e s s

have to do with c or ro si on and H2S disposal .

successful ly control led by providing sui table ma ter ia l s of construct ion

fo r the turbines , cond ense rs and re la te d equipment . H2S control has

of ten been a p rob lem because the e a r l i e r p lant s have used ba r om et r ic

condense rs ra the r than su r face condense rs . In the fo rm er cas e much

of the H2S i s abso rbed in the cool ing wat er and re lea sed to the a tmo s-

ph er e in the cooling tower.

be achieved by using s urfac e c ondensers , in which ca se the H2S app ear s

in the d i sch arge

gases

f r o m t h e v a c uu mp u mp s a n d m a y b e r e mo v ed c o m-

plete ly by es tabli shed technology.

Cor ros ion has been

However, comp lete con trol of the H2S m ay

Th ere se em s to be no s ignif icant technical r is k involved in des igning

a

f l a shed s team p lan t , and we cons ide r the f l a shed s team proc ess to be a

prov en one.

T h e r e i s nothing new in the co ncept of emplo ying an org an ic fluid in a

clos ed Rankine cycle. Over

1 , 0 0 0

so-cal led "naphtha launches" were

bui l t in the la te 19th and ear ly 20th centur i es us ing petroleu m naphthas

a s a workin g fluid. The R.ussians a r e r e p o r t e d to have a smal l

750

kw

geotherm al un it in opera t ion employ ing Fr eo n a s a working fluid.

J a p a n a plant has been in opera t ion s ince 1967, recover ing was te heat

f r o m a pe t rochem ica l p lan t and genera t ing 3 . 8 MW of sh af t w or k by

expanding Fre on in a rad ia l inflow turbine .

te s t loop wil l soon be i n opera t ion in the Im per ia l Val ley.

In

A nominal

10

MW isobutane

Hydrocarbon expansion tu rb ines up to 10,000 hp have been in su cces s -

ful opera t ion worldwide, and the re ap pear to be no ser io us technical



expander and others) req u i re the p rac t ica l so lu t ion to many d i f ficu lt

p ro b le ms asso c ia ted wi th sca ling , cor ros i on and e ros io n of m eta l

p a r t s .

a r e l ike ly to be ready fo r c omm erc ia l iz a t ion wi thin the next two year s .

C lear ly , none of the tota l f low options a r e s ta t e-of - the -ar t o r

A modif ica tion of the b inary p r oc es s . in which a direc t -con tac t exchanger

i s subst i tu ted for the tubular exchanger

i s

under development by sev era l

f i rms

including The B en Holt

Go.

el iminat ing the prob lem of sca le bui ldup on tubular excha ngers and in

reducing capi ta l cos t by subst i tu t ing a re la t ive ly inexpens ive d i rec t -

contact exchanger for the tubular exchanger .

and economic feas ib i l i ty wi l l be demo ns t ra ted wi th in the next two year s .

This modif ica tion shows promi se i n

We expect that tec hni cal

Another modif icat ion of the binar y pr oc es s i s incorp ora ted in the des ign

of the Niland Te st Fac ilit y. Scaling of the hea t exc han ger s

i s

minimized

by f lash ing the b r in e

at

fou r succes s ive ly low er p re s su re s ,

scrubbing

the par t icu la te s f ro m the f lashed s tea m and hea ting the i sobutane

working fluid by condensing the f la sh s t ea m in tubular excha ngers .

The

m e r i t s of t h i s s cheme a r e planned fo r dem ons trat ion by the end of 1976.

We have l imi te d our s tud ies i n

this

r ep o r t t o the s t a t e -o f - the -a r t

options.



SELECTION O F PLANT SIZE

f

It

i s

c le ar tha t geo thermal power p lan ts come in re la t ive ly

small

s i z e s

a s compared w ith fo s s i l f ue l o r nuc lea r p l ant s .

ins tance , a module

i s

110 MWe and a t Ce r r o Pr ie to the in i t ia l ins ta l -

la t ion

i s

75 MWe (two 37.5 MWe s te am turb ine s).

t h i s

i s

an econom ic one.

col lect ion and re inject ion of the f luids incr ea se s

a s

mo re w e l l s (bo th

production and re inject ion) a r e required.

ene rgy lo s se s become g rea te r .

At The Geysers , fo r

T he ma in r ea s on fo r

A s single plants get la rg er , the co st of

A lso the f lu id t r an sm is s ion

Another reason

i s

a tech nical /econ om ic one. F o r example, no hydro-

carb on expansion turbin es have been buil t even in the 60-70 MWe range,

a l though the re a ppea r to be no se r io us techn ica l p rob lems assoc ia ted

with scaling up existing designs.

O r f o r t ha t m a t t e r ,

i f

capaci ty should

rea l ly t u rn ou t to be a l imi t ing fac tor , m ul tip le un i ts ma y be ins ta l led on

a c omm on shaft a t so me economic penalty .

In e i ther the

25

MWe or

50

MWe sizes of

a

binary cyc le p lant , we a r e

alr ead y deal ing with mult iple uni ts of m aj or equipment . F o r example,

the p re l im inary equ ipment se lec t ion

a t

Heber p rov ides fo r e ight ho t

wate r /wo rking f luid exchanger bundles , e ight condenser bundles , e ight

hydrocarbon pum ps, thr ee cooling water pumps and 10 to 12 cel ls in

the cooling tower.

A

25 MWe un it would have abou t one-half of the

numbe r of these units . Since individual exchangers , cond ense rs ,

pumps and cooling tower cel ls

a r e

a l r eady

as

l a r g e a s a r e r ea d il y



viab i li ty of power p roduct ion f r om low sa l in i ty medium tem per a tur e

hot w a te r r e se rvo i r s . Moreove r,

i f

the de mo nstr atio n plant could not

genera te e lec t r ic i ty economical ly , the re would be l i t t le incent ive to

keep it operat i ng beyond a rea son able te s t per io d without subsidizing

the operat ion. By con tras t , an economic operat i on would be self

support ing, would provide re al i s t i c co st data and would encourage

rap id development, not only of the res e r vo i r on which the p lan t i s

l oca ted bu t a l so o the r r e se r vo i r s .

Based on da ta p resen t ed in our economic ana lys is , we have es t im ated

the c ost of power fr om a

25

MWe binary plant a t Heber as compared to

a 50 MWe plant.

i s

about 35 .2 m i l l s /kw h.

42 .3 mil l s /kw h ,

an

i n c r e a s e of about 2070.

making

this

ca lcu la t ion a r e a s fol lows:

O ur ba se ca se e s t im a te fo r t he cos t of pow er a t H ebe r

The corresponding f igure fo r 25 MWe is

The assumptions used in

1.

2.

3.

4.

5.

6 .

Powe r p lan t cap i ta l cos t

i s

61% of

a 50

MWe plant.

Powe r p lant labor

i s

constant.

Power p lan t main tenance i s p ropor t iona l to cap i ta l.

P ow er p lan t, w a te r , chemica l s and misce l laneous cos t s a r e

propo rt ional to capi ta l .

T ransm is s ion cos t s a r e cons tan t.

One-half

as

many wel ls a r e d r i lled .



HEAT REJECTION OPTIONS

Heat re jec t ion pe r kwh f r om a geoth erma l power plant is higher than

tha t f rom a fos s i l fue l o r nuc lear power p lan t because the the rm al

eff ic iency is low er.

F o r example, the the rm al eff ic iency of the Heber

binar y cycle plant is about 1370, a s compared with a typical fo ss i l fuel

plant of 347'0,

and heat re ject ion p er kwh from the geo thermal uni t is

about 3 .44 t im es that of the fo ssi l fueled plant .

appa rent that the method and cos t of heat re ject ion is re la t ive ly a more

important considerat ion in the design of geotherm al power plants than

in

e i ther f oss i l fue led

o r

nuc lear p lan ts .

Moreover , because the hea t

s o u r c e is i t se l f a t a low temp era tur e ,

the efficiency

is

very sens i t ive

to the heat re ject ion tem per atu re . In the range of t empe ra tu re

of

in t ere st , the net work produced is roughly proport ional to the

tem per a tu re d i f fe rence be tween the hea t source and the hea t s ink .

Th ere a re thr ee proven heat re ject ion options avai lable:

w e t

cooling,

a i r cooling and a com bination.

Thus, it becomes

Typical ly , wet cooling towe rs can reduce the temp era tur e of the

rec i rc u la ted coo ling w ate r to wi thin

6

C (10

F )

of the pre vai lin g wet

bu lb tempera ture ,

which

is

typ ica lly a t le as t 11

C 2 0 F )

l e s s t ha n

the p reva i ling d ry bu lb tem pera tu re .

Dry coo ling sys tem s fo r hea t re jec t ion use f inned

heat

exchanger tubes

to t ransf e r the hea t f rom the p roce ss f lu id to the a tm osphe re . The

min imu m temp era tu re a t w hich the se sy s t ems can di s s ipa te hea t is



about $13, 000 ,000 .

para s i t i c power requ i reme nts in c rea se about 5 MWe.

given plant siz e, power output

i s

reduced about

20%

and cos t s inc rease d

about 20oJ0.

Thus, if the plant costs $500/kw with wet cooling,

i t

wil l cos t a t l eas t

$750/kw with d ry cooling.

The los s in cycle ef f ic iency i s about l o%, and the

Thus , fo r a

The net effect i s a 50% inc rea se i n the uni t cos t per kwh.

A s im i la r ana lys i s was made fo r a fl a shed s t eam sys tem .

a

c i rcu la t ing wa te r sys tem

i s

requ i red to t r ans f e r h ea t f ro m the con-

de ns er to the a i r cooler . The num bers come out about the sam e

- -

a reduct ion in cycle ef f ic iency, an incr eas e in pa ras i t i c power con-

sumpt ion and a sha r p inc re ase i n ins ta l l ed cos t pe r kw.

In th i s case ,

We did not continue o ur analy sis fur th er becaus e it app ears obvious

tha t a i r cooling i s

not a viable al tern ativ e to wet cooling, and neither

a r e combina tion coo le rs s ince they a r e even m or e cos t ly than a i r

coo lers. Mo reov er, we suspe ct that a definit ive study would show an

e v en g r e a t e r c o s t in c r e a s e .

The re i s one a l ternat ive which we did not examine because of t ime

l imita t ions .

t e mp e r a t u r e s a r e l ow.

say, 28

C (50

F ) and then examine the dai ly and se aso nal var ia t ion s in

power output which might result .

output would be gr ea te r than des ign and dur ing the s um m er months

le ss than des ign.

At Va l les Ca lde ra , fo r example , fo r much of the ye a r a i r

One migh t des ign fo r an a i r t em pera tu re o f,

During the winter months, power

The over a l l r esu l t might not be too bad.



FLASHED STEAM PROCESS

GENERAL

Thre e fac to rs s t rong ly a f fec t the p ro ces s des ign of f l a shed s tea m

geotherm al p lan ts .

They a r e a s fo llows:

1.

The tem pe rat ure and composi t ion of the geo ther ma l br in e .

2.

The cha ra ct er is t i cs of the avai lable heat s ink.

3 .

The s ize and the ch ara c te r i s t i c s of the tu rb ines ava i lab le fo r us e

wi th g e o t h e r m a l s t e a m.

The ini t ia l t em pera tu re of the re se rv o i r flu id de te rmin es both the

quant ity of s te am which can be f las hed f r o m

i t

and the tem pe rat ur e of

the resu l t ing s team.

f lashed. Our f l a sh calcula t ions a r e done with a c o mp ut e r p r o g r a m

which take s th is ef fec t in to account . Of the th re e geot her ma l f ie lds

under cons ide ra t ion in th i s r epo r t , the mos t concen t ra ted b r ine e x i s t s

a t Heber , abou t

15,000

p a r t s p e r mi ll io n .

f l a s h is reduced approx imate ly 39 0 by the d issolved sol ids .

Dissolved sol ids a l so affec t the amount of s t ea m

I n t h i s c a s e , t h e s t e a m

It

is

ususa l ly p rac t i c a l to f l a sh the reduced l iqu id

a

second t im e, us ing

the secondary s t eam in lower s tages of the tu rb ine .

i s poss ib le to f l a sh the b r ine a n in f in it e number of t im es ex t rac t ing

Theore t i ca l ly , it



the des ign we t bu lb t em per a tu re in each a rea .

The ov era l l e f f ic iency

of th e pla nt i s significantly improved

if

the tem pe ra tu re of the cooling

w a t e r i s low.

In a l l cas es we have ass ume d tha t adequa te makeup wa te r wi l l be

available to pe rm it the ope ratio n of wet cooling towers .

The f lashed

st ea m plant produc es ad equate quanti t ies of condensa te which can be

used f or cooling tower makeup water .

th i s condensate is a valuable commodity which would pe rm it a f l a shed

s t e a m p la n t t o o p e r a t e wh e r e

other

types

of

plants could not.

Where wa te r supp lies a r e shor t ,

STEAM TURBINES

A survey was made of four dom es t ic and two Japanese companies

thought ca pable of providing turbi nes fo r

this

se rv ice .

companies only one , Genera l E le c t r i c Company, expr esse d in t e re s t in

producing geothermal steam turbines in the 25-50

M W e

r a n g e . Of the

two Japanes e compa nies , Mitsubishi and Kawasaki , the long l ines

of

communica t ions to the i r eng ineering depar tments made it i mp r a c t i c a l

t o c a r r y o ut a cooperative study.

we re conducted maingly with the Ge neral Ele ct r ic Company.

Of the do me sti c

Accordingly , our turbine s tudies

Geoth ermal tur bine s o pera te under d i f ferent condit ions f r o m convent ional

power p lant turbines .

ind ica tes tha t depos i t s fo r m on the tu rb ine bucke ts ,

subject ing the

mach in es to m or e v ib ra t ion than those in convent ional se rv ice .

According ly , Genera l E le c t r i c uses ex t ra r ig id bucket s which a r e no t

Exper ience with The Ge yser s geo the rmal p lan t s



were done at a n u mb e r of p r i m a r y a n d s e c on d a r y s t e a m p r e s s u r e s

c h o s en i n r e l a ti o n t o th e i n i t i a l b r i n e t e mp e r a t u r e ,

m at r i x giving the amount of pr im ar y and the amount of second ary

st ea m produced a t ea ch combinat ion of f i r s t and second-s tage

p r e s s u r e s .

The resu l t was a

The second s tep was to ca lcu la te the approx imate s tea m f lows to

produce 55 MWe gr os s f r o m each of the s tea m f lash ca lcu la t ions

derived above.

s te am r a t es f o r each expans ion f r om a range of in i t i a l s t ea m condi tions

t o s e v e r a l c o nd en si ng p r e s s u r e s .

This w as done by

f i r s t

ca lcula t ing the theore t i ca l

The se w ere conver ted to "actual"

s te am ra t es by d ividing them by e s t ima te d tu rb ine e f f i c ienc ies .

It

then poss ib le to c a lcula te for each in i t ia l and f inal condi t ion, the

p r i m a r y a n d s e co n da r y s t e a m f lo w s f r o m

1000

pounds of brine and

resu l tan t e lec t r i ca l gene ra t ion .

Finally, by dividing

55

MWe by this l a st f igu re, we obtain

a

f a c t o r

bo th b r ine and s tea m flows.

wa s

the

f o r

F o r each p lan t, th i s ca lcula t ion was pe r fo rme d i n t abu la r f o r m f o r a

l a r g e ma t r i x of p r i m a r y s t e a m, s e c o n da r y s t e a m a n d c o nd en si ng

p r e s s u r es.

TURBINE SELECTION

Using the pre l im ina ry ca lcula t ions a s a guide, GE turbine sp ecia l is ts



Th is was done with the coo pera tion of th e Ingersoll-R.and Company

which

has

fu rn ished most of the s t ea m condensers a t The Geysers

plant.

Befo re p re l im ina ry condenser des igns could begin , however , some

in i t i al dec i s ions had to be ma de , pa r t i c u la r ly w i th r e s pec t t o ma te r i a l s .

Be cau se of the expected CO and

H2S

content of the candidate

br in es and in defe rence to exper ience a t The Ge ysers , the fo llowing

s e l ec t io n s w e r e m a d e f o r a l l c a s e s :

Shell

Non-welded inte rn al s Type 316

Welded int ern als Type 316

L

Tube shee ts

Tube s Type 316

Type 3 16 L cla d

Type 316 clad on s te am s ide only

The des ig ner s we re g iven the op tion of tube d iam ete rs f ro m 14

mm

( 3 / 4 ” ) t o

25 .4 mm

(1” ) with

a

tube wa ll thi ckn ess of

0. 7 mm (22

BWG).

F o r s ta in less tubes of these d im ens ions , wate r ve loc i t ies of seven to

n ine fee t p er second

a r e

usual ly us ed in public ut i li ty power plants .

We s e lec te d an average va lue of e igh t fee t pe r second. Assuming tha t

an Am er t ap cont inuous m echanica l c lean ing sy s te m would be used wi th

the cooling water ,

a

condenser

c l ean l ine s s f ac to r

of 0.85

w as u sed fo r

a l l c a s e s .

A co ld-wate r t em per a tu re compat ib le wi th the hea t - s ink cha rac te r i s t i cs



o r d e r

of

magni tude l ar ge r than i n convent ional publ ic u t i l i ty power

p lant s . Fu r th e r , the poor in i t i a l s t e am condi tions make s team je t

e je c to rs uneconomical in these appl ica t ions . Vacuum pumps we re

s ized to accommodate the expected gas f low fr o m the br ine p lus the

amount of a i r normal ly accumulated through leakage. Where cold

wat e r t emp era tu res a r e su f f icien tly low, the use of p re -condense rs was

investigated.



THE BINARY PROCESS

GENERAL PROCESS DESCR.IPTION

T h e b i n a r y p r o c e s s f o r p r od uc in g e l e c t r i c e n e r g y f r o m g e o th e r ma l

re se rv oi r f lu id involves the t ra ns fe r of heat to a second ary , in-plant

working fluid.

produce power .

shel l and tube cond ensers .

The working fluid

i s

expanded through

a

turbine to

The expanded gas

is

then condensed in a bat ter y of

The working fluid i s cont inual ly rec i rc u la ted f r om the tu rb ine to the

hea t source .

and tube exchangers a t an e leva ted p ress ure .

f lu id f lows f r o m the product ion wel ls through the tubes .

fe r r ed f ro m the res e rv o i r f luid to the work ing f luid.

e i the r in the sub cr i t i ca l o r supe r -c r i t i ca l r egion.

fluid

i s

pumped f r om the p lant to in jec t ion wel ls .

The fluid i s pumped to the s hell s id e of a bat te ry of sh ell

Hy d r o t he r ma l r e s e r v o i r

Heat i s t r a n s -

Opera t ion ma y be

The spen t r e s e rv o i r

CONVERSION STUDY BASIS

T h e b a s i s u s e d in develop ing the b ina ry p roc ess des ign fo r the th r ee

p lan t s i t e s

i s

defined below:

1.

E a c h p la n t i s s i z e d f o r a net output of 50 MWe.

be s ize d wi th suff icient capaci ty to provide fo r in-plant e l ec t r ic

The genera to r wi l l



The pr i m ar y purpos e of the above condi tions and assump tions was to

es tab l i sh a un i fo rm base of comp ar i son fo r a l l th ree p lan t s i t e s .

Select ion of the opera t ing f lu id and opera t ing condit ions was d et er -

mined fo r each s i t e by a compute r p rog ram , evaluat ing the the r mo -

dynamic p ro per t i e s of va r ious sys tem s .

mi ze the re se r vo i r f luid f low requ i reme nts .

The emphas i s was to m in i -

SELECTION O F WORKING FLU ID

Ligh t a l ipha t ic hydrocarbons ( such a s p ropane, i sobu tane and i so -

pen tane) appear to be the b es t cand ida te work ing f lu ids fo r mo s t

geo the rm al app l ica t ions .

p r o p e r t i e s , a r e t h e r ma l l y s t a b le , n o n c o rr o s iv e , a nd a v ai l ab l e i n l a r g e

quant i t ies at reasonab le p r ic es (abou t

50

cen ts /ga l lon) .

They have fa vorab le the rmodynamic

T h e F r e o n s m a y a l s o b e u s e d.

the rmodynamic p rop er t i e s , a r e expensive (about $5 /ga llon) , and a r e

the r ma l ly uns tab le .

f l a mma b l e.

However, they offer no advantage in

The ir only advantage i s that they

a r e

non-

A num ber of ot he r candidate f luids have bee n suggested , including

all

of the obvious ga se s such as am mon ia ,

sulf ur d ioxide , carb on dioxide

and l ight a l ip hat ic o lef ins .

l ight a l iphat ic hydrocarb ons .

None appe ar to offer advantages over the

Another v i r tu e of the a l iphat ic s i s tha t the i r the rm odynamic and



THE HYBRID PROCESS

GENERAL

A hybrid power plant i s a combination of two pr oc es se s, the f lash ed

s te am pro ces s and the b ina ry power cycle p rocess .

f lashed to produce s tea m at a re la t ively high pr es su re , which i s used

to dr ive a turbine-genera tor .

the working fluid which driv es a second turb ine-g enera tor.

Rese rvo i r f lu id is

The res e rv o i r f luid i s then used to heat

THE FLASHED STEAM SECTION

The desig n of a hybrid plant s ta rt s with f ixing the pr es su re a t which the

s t e a m i s f l as h e d f r o m t h e r e s e r v o i r flu id .

des i r able because the high pre ss ur e wi l l improve turbine efficiency and

reduce the turbine s ize and cost. T he p r e s s u r e t h a t i s chosen affects

the rel at ive si ze s of the two pa rt s of the plant, a s well a s the quanti ty

of r es er vo ir f lu id requir ed by the plant .

d i f fe rent s t eam -f lash p re ss ur es wer e inves tiga ted to de te rmine the

mo st efficient generating condit ion fo r the plant.

High p r e s s u r e s t e a m i s

F o r e a c h p la nt , s e v e r a l

THE BINARY SECTION

The f lashing of the s te am fr om the re se rv oi r f luid resu l ts in cooling the



HEBER CONVERSION PLANTS

Detailed data relat ive t o the s i te , the geology, the reservoir , the

environm ent, plant facil i t ies and field facil i t ies a r e contained in

companion volum es.

of th is sec t ion and succeeding sect ions a r e repeate d in th is volum e.

Only the data n ec es sa ry to fulf il l the objectives

THE RESERVOIR

/

The Heber geo thermal re ser voi r i s located in the southern par t of the

Im pe r ia l Val ley a t an e levat ion that i s c lose to sea leve l .

S u mme r t ime t e mp e r a t u r e s v a r y up

t o

49

C

(120

F);

one percent of the

t i me d ur in g t he s u m e r mo n t hs , th e wet b ul b t e mp e r a t u r e r e a c h e s

o r

exceeds 2 7 C (80 F) . This wet bulb tem per atu re was used for des ign.

T he a r e a i s l e ve l a nd de vo te d m a i n l y

t o

a g r i c u l t u r e .

bounded by irr ig at io n ditches which

will

supply makeup w ater to the

plant.

T he p la n t s i t e i s

Roads and power l in es ar e close to the si te .

The res er vo ir f lu id has a to ta l d issolved sol ids content of 15,000 ppm.

The bottom hole t em pe rat ure is 182

C (360

F ) .

i f

t h e r e i s no h e a t r e c h a r g e , t he t e mp e r a t u r e

of

t h e r e s e r v o i r wil l

decline about

20

C

(35

F )

over a 25-year per iod a t a sus ta ined pro-

duct ion ra te

of 200

MWe.

This t empera tu re d rop of the reservoir f lu id

Analysis indicates that



T e m p e r a t u r e ,

C

T e m p e r a t u r e , F Fouling Fa c to r

176 to 132 350 to 270

O O O l

132 to 80

270 to 176 O O l l

80 to 65 176 to 148 .00 33

These fa c to rs a r e t enta t ive in tha t the re su l t s of

a

22-day t es t have

been ex t rapo la ted to p red ic t

a

foul ing fac to r sui table for one yea r ' s

opera t ion.

months to conf i rm these f igures .

Fu r t he r te s ts should be conducted over

a

per io d of s eve ra l

The exchanger te s t s wer e conducted us ing ti tanium, 90% cupro nickel

and mild s te e l exchanger tubes .

t i t an ium tubes a f te r 560 hou rs ' exposure ; some c or ro s ion occur r ed to

the cupro nickel tubes af ter

200

ho urs ' test in g; and sl ight pit t ing and

sur fa ce decarbon iza t ion wer e ob se rved on the ca r bon s tee l tubes a f t e r

560 ho ur s of test in g.

t u b e s ha d o c c u r r e d p r i o r t o t he t e s t p r o g r a m.

that cor ros ion during thei r t es t work was negl ig ible. Accordingly, we

have spe cified the use of st ee l in all equipment exposed to br in e or

f l a shed s team , excep t s t ea m tu rb ines and su r face condense rs a s no ted

in the p rev ious sec t ion . Fu r th e r co r ro s ion t e s t s wi th the Heber b r ine

should be conducted befo re a f inal dec ision i s made on p lan t ma te r ia l s .

No

cor ro s ion was o bse rved on the

It i s possible that the s l ight corr os i on of the s tee l

Chevron has indicated

FLASHED STEAM

P U N T

A pr oc es s f low she et of the f lashed s te am plant i s shown in drawing



T he seconda ry f l a sh d ru ms f loa t on the l ine , t he i r p r e s su re va ry ing

wi th tu rb ine- s tage p r es su re and with demand .

The f lashed l iqu id f lows f ro m the secon d-s tage f lash d ru ms to the

suc t ion of the in jec t ion pumps which re t u r n the l iqu id to the re se rv o i r .

L iquid leve l

i s

main ta ined in the seco nd-s tage f lash d ru ms by a con t ro l

va lve on the pump d ischarge .

The turbine- .generator

is

ope ra t ed as

a

base-load unit under load

contro l . The opera tor ass i gns a load to the gener a tor , and the tu rb ine

mu st a ccep t tha t load a t cons tan t speed .

de tec ts changes in load and ad jus ts adm iss ion va lves on bo th the

p r im ar y and seconda ry s t e am l ine s to s a t i s fy the a s s ignmen t .

s epa r a t e emergency t r i p mechan i sm on the tu rb ine sha f t w i l l c lo se

emergency s top va lve s on bo th p r im ar y and seconda ry s t e am l ine s i f

tu rb ine speed exceeds

3,600

r p m b y

a

given perce n tage .

The turbine governor

A

E xhaus t s t e a m f r om the tu rb ine pa s s e s d i r ec t ly into a su r f ace condense r ,

w h e r e a b ac k p r e s s u r e

of

13.5 k P a

(4

n. Hg)

i s

obtained under design

cooling-water conditions.

the in jec t ion pumps .

mak e the rep len ishment vo lume subs tan tia l ly equa l to

the

volume

of

f r e s h b r ine de l ive red to the p lan t.

103

C (217 F).

The c onde ns a t e i s pumped

to

t he suct ion of

The condensate is added to the reduced br ine to

Ave rage tem pe ra tu re of th is flow

is

Cool ing wate r f ro m an induced dra f t cool ing tower en te rs the co ndenser

at

35

C (95

F )

and r e tu rn s to the tow er

at

49

C (120

F) .

The hot cooling

w a te r t em pe ra tu re g ive s a min imum condense r app roach

of

2.7 C

(5 F).



A su m m ar y of per t inent des ign data i s a s follows:

Rese rvo i r f lu id

Ge ne rat or output 55.0 MWe

Pum ping work 3.2 MWe

Cooling tow er wo rk

1 .1

MWe

Net output 50 .7 MWe

Res ervo i r f lu id /ne t kwh

4 .54 M k g / h r ( 10 .0 1 M l b s / h r )

90 kg (200 lb s)

When res e r vo i r t emp era tu res dec i ine wi th deple tion, in i t i a l e lec t r i ca l

output can be maintained by inc rea sin g hot wat er f low.

Theore t i ca l ly , a plant des igned for th e depletion condit ion of 163 C

(325 F) would re qui re 37% m or e hot wa ter than one des igned for the

ini t ia l condition.

(325

F )

hot wa ter would req uir e a l t ere d s t ea m condit ions to mainta in

propor t ion a l flows th rough the tu rb ine s tages .

63% in cr ea se d flow of hot water .

a r e comp ared be low:

How ever, opera tion of the ba se -c as e plant with 163 C

This would re su l t in a

Init ial and final operating condit ions

In i t i a l F ina l

Reservoir Fluid

4 .54 M kg /h r

(10. 01 M lb s /h r )

7 .39 M kg /h r

( 1 6 . 3 M l b s / h r )



BINARY PLANT

A pr oc es s f low she et of th e b inary plant

i s

shown on drawing number

7523-D-3205.

fo r the in i t ia l re se rv oi r condit ions.

Th is f low shee t p resen t s the hea t and m ate r ia l ba lances

Liquid isobutane i s preh eated and vapor ized by exchange with the br i ne

to a pr es s ur e of 4137 kP a (600 ps ia ) and a te m pe ra tu re of 149 C (300 F).

The super - c r i t i c a l vapor d r ive s an expansion tu rbine .

vapor f ro m the tu rb ine condense r f lows to an accumula to r and

i s

pumped

back through the bri ne ex changer com pleting the circ uit .

The effluent

A sum ma ry of the per t inent des ign data is a s fo llows:

Rese rvo i r f lu id

Isobutane

Ge ner ato r output 64.28 MWe

Pumping work 9.48 MWe

Cooling to w er wo rk 4.83 MWe

50.00 MWe

63 kg (139 lb s)

3 .149 M kg/ hr (6.942 M lb s / h r)

3 .702 M kg /h r (8.161 M l b s / h r )

Rese rvo i r f lu id lne t kwh

The magnitude of th e above flow requ ire me nts ma kes the us e of

pa r a l l e l f low pa ths ne ces sa r y o r de s i rab l e in va r ious sec t ions of the



r e s u l t s i n

a

signif icant reduct ion in the c ost of heat t ra ns fe r equipment

f o r t h i s s e r v i c e a s c o m p a r ed t o o u r f o r m e r e s t i m a t e s .

It i s

an t ic ipa ted tha t the exchangers wi l l be c leaned e i ther mechanica l ly

o r chemica l ly once pe r y ea r dur ing an annua l tu rnaround .

v is ion has been m ade fo r perm anen t ins ta l la t ion fo r c leaning.

No p r o -

E xpande r quo ta tions w e r e r ece ived f ro m fou r vendo r s . T h ree w e re fo r

axi al f low designs, and one (Rotoflow) pr ep ar ed a ra di al in-f low design.

The Rotoflow offer ing was u sed in th is s tudy, but fur t he r evaluat ions

of expander o f fe r ings a r e nec es sa ry before a f ina l se lec t ion

i s

made.

The e igh t isobutane pumps a r e mul t i - s tage ve r t ic a l cen t r i fuga l pumps ,

1 ,750 hp each . These pumps ,

a s

well a s cooling tower pum ps and the

cool ing tower fans a r e e lec t r ica l l y d r iven .

P r i m a r y p r o c e s s c on tr ol

i s

based on the p r em ise tha t p lan t ou tput wi l l

v ar y with demand. Consequently,

a

load con t ro l w i th manua l se t po int

i s

i ncluded fo r t he gene ra to r ,

control l ing the iso butane f low ra te t o the

turb ine . Res erv o i r f lu id f low ra te

is

control led by the tem pe ra tu re of

the isobutane vapor. Adjustme nt of isobutane and re se rv oi r flu id f low

ra t e s to each pa ra l l e l t r a i n of h yd ro ca rbo n / r e se rvo i r f lu id hea t

exchangers

i s

manual .

f low ra t e s to each condense r i s a ls o manual.

em erg enc y over spe ed shutdown of the turbin e.

Adjus tment

of

isobutane vapor and cooling water

P lan t de s ign p rov ides fo r

P re l im ina ry f i e ld s tud ie s ind ica t e tha t t he w e ll fl u id t empe ra tu re a t



Base Case Depleted Case

586 kP a (85 ps i a )

896 kPa (130 ps i a )

orking fluid accum ulato r

ope ra t ing p re s su re

The inc rease in requ i red f low ra t es fo r res e rv o i r f lu id and work ing

fluid wil l nec ess i ta t e futur e changes t o the plant equipment .

numb er of br in e /working f luid exch ange rs , hydrocarbon co nden sers ,

work ing f lu id c i rcu la tion pumps , coo ling wate r c i rcu la tion p u p s , and

cooling tower cel ls m ay inc rea se. The turbine -expander

is

designed

to ope rate und er the conditions of the depleted ca se with a mi nim um

change in pa r t s .

The

The req u i red des ign pre ss ur e fo r accu mula tors , work ing f lu id s ide of

the working f luid con dens ers and the c as e of the turbine

w i l l

i nc rea se .

The des ign pre ss ur es fo r the equ ipment fu rn ished in the base case

have been up- ra t ed t o m ee t this condition.

Piping

as

shown for the ba se case (m ajo r l in es ) wi l l handle the

i n c r e a s e d f l o w

req uir em ent s . Additional piping, instrumentat ion and

e l e c t ri c a l m a t e r i a l

i .

e . , sw i tch gea r ) w i l l be r equ i r ed fo r

the

new

equipment .

Thus, the plant

is

somew hat ove rsize d fo r the beginning condit ions

but m ay be e conomic al ly expanded to accommo date the depleted

re s e rv o i r cond i tions .



Res ervo i r f lu id /ne t kwh

6 5

kg (145 lb s)

These condit ions we re chosen af te r having considered f lashing

tem pera tu re s be tween 160 C (320

F )

and 171 C (340 F) in combination

with isobutane expander in le t condi tions ranging f ro m 400 t o 600 p s i a

a t t em pera tu re s be tween 127

C

(260 F ) and

149

C (300 F).

operat ing condit ions opt imize the power gen era te d pe r w el l f lu id flow

ra te .

The se lec ted

Wa te r - s ea l vacuum pumps wer e se lec ted to rem ove noncondensab le

g a s e s f r o m t h e s u r f a c e c o n d e n s e r s b e c a u s e t he s e a l - wa t e r c o nd e ns e s

a

l a r ge pa r t of the en t ra ined wa te r vapor .

blow down will be u sed a s

sea l wa te r . The noncondensab le gase s wi l l

be pumped in to the f l a re sys tem .

d i s p e r s a l of the hydrogen sulfide pre sen t. The blowdown and se al

wat er w i l l be pumped in to the eff luent re se rv oi r f lu id to avoid contami-

nating the environment.

Most of the cooling tow er

T h e f l a r e s t a c k i s des igned fo r

The bas ic p ro ces s con t ro l s a r e the manua l se t po in t load con tro l s a t

the two turbine-genera tor uni ts .

o the r .

bu t have d i f fe ren t r e sponse l ags , the over r ide wi l l p reven t both

con t ro l s f ro m f igh ting each o the r .

One of the two co ntr ols will re se t the

Since both uni ts depend on the sam e s ou rce of re se rv oi r f lu id

An i sobu tane vapor t empe ra tu re con t ro l r egu la tes the f low of r ese rvo i r

f lu id through the isobutane exchange rs .

con trol regu la tes the f low of r es er vo ir f lu id to the p lant .

A s t e a m s e p a r a t o r l e v e l

All the



RESERVOIR FAC ILITIES

The sys tem s developed in th is s tudy for the production

of

geo thermal

hot wa te r , and the d i sposa l of the spen t wa te r , a r e based on p re mi ses

se t for th by Chevron Oil Company,

dev elop ers of the He ber field.

pr oc es s base s es tabl ished by Chevron include:

The

Product ion

1.

2.

3.

4.

Direct ional dr i l l ing of a l l product ion wel ls required fo r a

50

MWe

power p lant wi l l be concentra ted in an a re a of about one acr e .

Produc tion wells will be pumped a t a r at e of about 295 m 3 /h r

(1,300 gpm).

Two a l t e rna te sand s epa ra t o rs wi ll be p rov ided , each s ized fo r a

one-m inute resi den ce of the tota l f low.

An au tomat ic bypass of the power p lant wi l l be provide d sending hot

geother mal water d i rec t ly to the in ject ion sys tem.

Injection

1.

Spent water in jec t ion

i s

made through wel ls dr i l led at th ree i s l ands

uniformly spaced on one quadrant

of

the c i rcumference

of

the

re se rv oi r having a r adiu s of about 3 ,048 m (10,000 fee t )

i t s

c e n t e r



Produc t ion Sys tem s

The des ign of the production piping s ys te m s

i s

i l lus t ra ted i n the f l a shed

st ea m s yst em shown in drawing numb er 7523-D-3223.

s ized to accommodate the l a rg e r f low a t t end ing opera t ion when the

g e o t h e r ma l wa t e r t e mp e r a t u r e d e c l in e s t o 163 C (325 F) .

provided with a down-hole pump ra t ed at 295 m3/hr (1300 gpm) and

2,069 kP a (300 ps i ) head.

pipe in the s ys te m, per t inent d imensions of p ipe runs a r e g iven in the

drawing.

T he l i n es a r e

E a c h we l l

i s

To facil i ta te the e st i ma tio n of the co st of the

Down-hole pumps a r e ve r t i c a l sha f t -d r iven cen t r i fuga l s a s o f fe red by

P e e r l e s s P u m p Co.

The bear ings

wil l be a spe cia l te f lon type sui table fo r h igh tem pera ture .

The pump

tubing wil l be f lushed with f i l te r ed product for lubr ica t ion of l ine-shaf t

bea r ings .

Bowl sett ing will be about

400

feet .

To mainta in a check on the opera t ion, each wel l

i s

provided with

t e m p e r a t u r e , p r e s s u r e a nd fl ow r e c o r d e r s . D i sc h ar g e p r e s s u r e

i s

control led by

a

pr es su re con t ro l va lve on a l ine which recyc les ho t

wa ter ba ck to the well .

The to ta l ho t wa te r p roduced

i s

al te rnate ly pass ed through one of two

sand sep ara to r s , each s ized to p rov ide one minu te res idence and a

velocity of about seven feet/ seco nd.

g e o t h e r ma l wa t e r f r o m t h e we l l s

is

expec ted to d rop ou t in the

s e p a r a t o r .

Any sand en t ra ined in the

The efficiency of sa nd sepa rat ion

i s

moni to red by



F l a s h e d S t e a m

B i n a r y

Hybrid

Inj

e

c t ion Sys tem s

Field Condit ions

Required Flow Wells Require d

Endnitial End Init ial

4 .5 M k g / h r

7 .4 M kg /h r

(10.0 M lbs /h r ) (16 .3 M l b s / h r )

4 .5

M

k g / h r

.1 M k g / h r

(6 .942 M lbs /h r ) (9 .9 M l b s / h r )

5 .81 M kg /h r.288

M

k g / h r

(7. 249 M lbs/hr) (12. 8 M lb s/ h r)

16

21

12 1 9

13 21

The geo the rm al wa te r f r o m the power p lant

is

p u mp - d b a c k

t

re se rv o i r th rough in jec t ion we l l s . The inject ion piping s ys te m for the

f las hed s te am pro ce ss a t Heber , shown in drawing 7523-D-3224,

i l lus t ra tes

the g e n e r a l

f e a t u r e s

of s u c h s y s t e ms . T w o n j e c t i on pumps

a r e p ro v id e d f o r t h e t o t a l fl ow whi ch , f o r t h e f la s h e d s t e a m p r o c e s s ,

va r i es f r om about 4 .5 M kg /h r (10. 0

M

l b s / h r ) in i t ia l ly t o 7 .4 M k g / h r

(16. 3

M

l b s / h r ) whe n th e g e o t h e r ma l ho t wa t e r t e mp e r a t u r e d e c l i n e s t o

163 C (325 F). The injection pumps have

a

discharge p re ss ur e of abou t

1 ,620 kPa (235 ps ia ) and de l ive r the spen t wa te r t o the fa r the s t in jec tion

wel l i s l and

at

about 1,48 2 kP a (215 psia).

c a n b e u s e d t o r a i s e t h e p r e s s u r e t o t h e ma x i mu m 2 ,8 6 1 k P a (4 15 p s i a )

at

the we l l head f o r in jec t ion at 590 m3 /h r (2 ,600 gpm).

the

At each i s l and

a

boos te r pump

Under init ial



P r o c e s s

F lashed s team

Binary

Hybrid

Wells Required

Initi al Fie ld Condition End Fi eld Condition

10

9

10

GENERAL FACILITIES

The following facil i t i es a r e provided for ea ch of the convers ion plants:

B u ild ng

s

The m a in con trol building is 15 by 23 m (50 by 75 fee t) and contains the

control room,

s w i t c h

gear , l abora to ry and shop. The com pres sor

building

is

7 . 5 by 7. 5

m

(25 by 25 fee t) and contains the

a i r

c o m p r e s s o r s

and dr ye rs . The cooling tower t rea tm ent build ing is 4. by 7. 5 m

(15 by 25 fee t) and contains the chem ical mixing ve sse ls and injection

pumps.

F i r e P r o te c t io n

The binary and hybr id p lants use the cooling tower bas in a s a f i r e-



provided with a dat a logging sy st em which w i l l moni to r and record all

per t inen t va r iab les .

date when mul t ip le p lants have been ins ta l led a t the r es er vo ir , a

s ingle computer can be in s ta l led to control a l l the p lants .

The sys tem

w i l l

be installed s o tha t a t a l a te r

Blow -down Dis pos al

A l l plants ar e des igned to d ispose of contaminated pro ce ss wat er s uch

a s cooling towe r blow down by disc harg ing the f luid into the ag ric ul tur al

d r a i n s .

No

t r ea tme nt fac i l i t i e s fo r the was tewate r a re p lanned.



v

V-3

v-4

PRIMARY

FLASH VE55EI-S

SECONDARY

F U 5 H

UE533-5

T I €

T U R ~ N E SURFACE

ONDENSER

G- I

GEN=TOR

STREAM PROPERTIES

N6T OUFWT K W

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COOL ING T O W E R

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ONDEN~TE

UMP

VACUUM PUMP

2 1 1 1

PM

KW.

153

W C F M

LW

THE

BEN

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G l

nnl~r /u .cEXCUANGER

EXPANDER

GENERATOR

H SURGE DRUM

COOLING TOWER

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H.C.

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E NE RATO R

v- l

C SUUY W U M

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STREAM PROPERTIES

THE

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u

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BINARY PO W ER PANT

s u a o F OP E . S T , ~ T E UP OW

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CLIFORNIA

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R E F E R E N C E DR WING

WMGW T , U

CT I

COOLING TOWER

CONOENIATE PUMP

345

GPM

k i

BLOWDOWN PUMP

63 GPM



VALLES CALDERA CONVERSION PLANTS

THE RESERVOIR

The Valles Ca ldera hydro thermal re se rv o i r i s loca ted in the nor th -

ea st er n co rn er of Sandoval County, New Mexico. The re se rv oi r i s

loca ted in mountainous te r ra in at an elevation of about 2 ,750 m et er s

( 9 , 0 0 0

f ee t ) . A t th i s e levat ion , a tm osphe r i c p r e s su re

i s

7 2 .4 k P a

(10.

5

ps ia ) .

A i r t e m p e r a t u r e s a t th e

s i te

range f r om 32 C

( 9 0 F )

i n s u m m e r t i m e t o

a s

l ow a s -40 C

( -40 F )

in the winter t ime. One per cen t of the t im e

dur ing the s um me r months , the wet bulb tem per a tu re in the a r ea

exceeds a temperature of

17

C

( 6 2 F).

T his t empe ra tu re w as u sed

f o r

de sign.

T he a r e a

i s

quite rough, with the geo therm al wells located along the

val leys cr ea te d by Sulfur Cree k and Redondo Creek.

a r ea i s r e s t r i c t e d , and roads to the s i t e a r e indica ted to be d i r t .

Acc ess to the

The avai labi l i ty of w ate r a t t he s i t e i s re st r ic te d by regulat ions of

w a te r r igh t s a s de sc ribed in the P re l im ina ry E nv i ronmen ta l

A s s e s s m e n t .

f ro m Santa C la r a Cr eek loca ted in the nor thwes t co rne r of Sandova l

County,

a

dis tan ce of appro xim ately 18

miles.

e lec t r i c pow er in the a r ea ,

and

it

would be necessary to br ing the

The ass es sm en t sugges ts tha t wate r migh t be ob tainab le

T he re a r e no roads no r



Wells a r e self-producing, providing well head f luid at the following

conditions:

T em pera tu re 182 C

(360 F)

P r e s s u r e 1 , 0 3 4 k P a (150 p s i )

F lo w r a t e

113 ,400 kg /hr (250 ,000 lb s / h r )

T h e s e d a t a . w e re us e d a s a des ign ba s i s .

No

in format ion

i s

ava i lab le on the cor r os i ve chara c te r i s t ics of th is

fluid.

to fluid f r om the H ebe r r e se rvo i r .

su i tab le ma te r i a l fo r p iping and ves se l s .

T he re fo re ,

it

w a s a s s u m e d t h a t

i ts

prope r t i e s w ou ld be s imi l a r

C a rbon s t ee l i s as sum ed to be

a

The S iOz pre sen t in the f lu id may caus e s ca l e to fo r m on the hea t

exchanger tu bes of the bina ry and hybrid plants .

fo rm ed to de te rmine the t em pe ra tu re l eve l a t w hich sca l e fo rma t ion

occu r s . If s ca l e fo rma t ion

i s

shown

to

occu r , then the b inary and

hybr i d p l a n t s c ou ld be de s i gne d to u s e f l a s he d s t e a m for heat ing.

Beca use the fou ling ch ara c te r i s t ics of the re se rv o i r flu id we re

not

known, the Heber fou l ing fa c to rs wer e used fo r the Val les Ca ldera

b ina ry and hybrid p lan ts .

T es t s should be pe r -

Some noncondensable gas es oc cur in the f lashed s team , but the con-

cen t r a t ion of ga s in the r e s e r vo i r f lu id

i s

not known.

t ra t io n of noncondensab le gases n ecess i ta tes

a

maj o r inves tmen t in

vacuum pumps fo r t he f l a shed s t e am and hyb r id p l an ts .

A

high concen-

It

w a s a s s u m e d



f low which cor re spon ds to a dec rea se i n the down-hole te mp era tur e of

20 C (35 F).

FLASHED STEAM PLAN T

Drawing number 7523-D-3203 i s a pro ce ss f low diag ra m of the Valles

Cald era f lashed s tea m p lan t . The ho t re se rv o i r f lu id en te rs the p lan t

at

a flow ra t e of 1. 8

M

kg/hr (3 . 9 6

M

l b s / h r ) .

pa s s into tw o pa ra l l e l f i r s t - s t a ge f l a sh d rum s a t a p r e s su re o f 1, 055 kP a

(153 p s i a ) . T he f i r s t - s t age d rum p roduces 324 ,770 kg /h r (716 ,000 lb s / h r )

of p r im ar y s t ea m w h ich pa s se s th rough a s t e am sepa ra to r be fo re

reach ing the tu rb ine -gene ra to r a t a p r e s su re of 1, 055 kPa (153 psia and

a te m pe ra tu re of 182 C (360 F ) .

T he b r ine and s t ea m

T he l iquid f r om the f i r s t - s t age f l a sh d ru ms f low s to the s econd - s tage

f l a s h d r u m s w h e re

i ts

p r e s s u r e

i s

reduced to 232 kPa (33.7 psia) .

resu l tan t f las h p roduces 169 , 192 kg / hr (373 ,000 lb s / h r ) of secondary

s te am which f lows th rough

a

s te am s epa ra to r to a lower s tage of the

turb in e-gen era to r th rough a s epa ra te s e t of a dmi ss ion va lves .

s t ea m rea che s the tu rb ine a t a p r es su re of 228 kP a (33 .0 ps ia ) and a

t e m p e r a t u r e

of

125

C

(257

F).

l i ne , t he i r p re s s u r e va rying w i th tu rb ine s t age p r e s su re and w i th

dem a nd.

The

The

The s econdary f lash d rum s f loa t on the

T he f l a shed liquid flows f ro m the s econd - s tage f l a sh d rum s to the

suct ion of the inject ion pumps which re tu rn the l iquid to the re se rv oi r .

L iquid leve l i s m ain ta ined in

the

second - s tage f l a sh d rum s by a con t ro l



Noncondensab le gas es f ro m

the

r e s e rv o i r f lu id and

a i r

l ea k ag e a r e

removed f ro m the condenser by tw o l a r ge vacuum pumps in pa ra l l e l .

The exhaust

g a s

i s

discharged in to a ver t i ca l s tack which

i s

designed

to di sp er se the hydrogen sulf ide contaminant .

A sum ma ry of per t inen t des ign da ta fo r the f lashed s te am p lan t i s

a s

follows:

R ese r vo i r fluid r a t e

1 . 8

M kg /h r (3. 96 M lb s / h r )

5 5 . 0

MWeenerator output

Pum ping wo rk 1.9 MWe

Cooling tower w ork .1 MWe

Net output 5 2 . 0 MWe

Re se rv oi r f lu id/n et kwh 34 kg

(76

l b s )

BINARY P L A N T

T he r e s e rvo i r f lu id a t V a l le s C a lde ra f lows na tu ra lly f ro m the w el l ,

p roduc ing two ph ases a t the sur face in the fo llowing propor t ions :

S t e a m

15.

3’7’0 (by we ight)

Hot wat e r

84.

770

by weight)



The heated isopentane in a s ubc ri t i cal condition

is

used to dr ive the

expansion turbine.

A

generator output of approximately 56 MWe

i s

requ i red to p rov ide fo r in -p lan t

e lec t r i c

power consumption and produce

a net output of 50 MWe.

Te s t s ru n on geo thermal re se rv o i r f lu ids a t so me loca t ions have shown

an inc re as e in deposi t ion of sol ids when the f luid

i s

cooled. In the

absence of speci f ic tes t da ta on the r es e rv o i r f lu id a t Val les Ca ldera ,

the fou l ing fac tor s observed with the Heber re se rv o i r f lu id wer e used.

The hydr ocarb on/ res ervo i r f luid hea t exchangers a r e des igned wi th

four un i t s i n s e r ie s to fac i l i ta te c lean ing .

A

su mm ar y of the pert inen t design data for the binary plant i s a s

follows:

R ese r vo i r f lu id

Isopentane

Ge ner ato r output 56 .3 MWe

Pumping work

3 . 6

MWe

2 .7 MWeooling tower work

Net output 5 0 . 0 MWe

Res erv o i r f lu id /ne t kwh

1. 19 M kg /h r 2. 6 2 M l b s / h r )

2 . 10

M

kg /h r (4 . 62 M lb s /h r )

24 kg (52 l b s )

HYBRID PLANT



Wastewater w il l be pumped into the eff luent re ser vo ir f lu id to avoid

contaminating the environment.

A s um ma ry of the pert inent design data fo r the hybrid plant i s a s

follows:

R ese rv o i r f luid r a t e

Gen erat or output 56.0 MWe

Pum ping wor k 4.6 MWe

1.4 MWeooling tow er wor k

Net power 50.0 MWe

1.36 M kg/hr (3 .0 M l b s / h r )

Res erv o i r f lu id /ne t kwh

27. 2 kg

60

l b s )

RESERVOIR FACILITIES

The s y s t e m s de ve loped

for

produc t ion and in j ec t i on of g e o t h e r m a l f l u i d

a t Valles Caldera , New Mexico, a r e based on conventional ver t ical

dr i l l ing of the wells a t a spacing of 30 ac r es p e r well.

Based on

squ are p lo ts , the d is tance be tween wel l s

is

approx imate ly 349 m et er s

(1 ,145 fee t ) .

The production wells in this f ie ld a r e self-f lowing, and

the fluid at the well head i s a mix ture of s te am and geo ther mal wate r .

The preceding descrip t ion of the production sch em e at Heber , California

appl ies fo r the mos t pa r t to Val les Ca ldera ,

except that s pecial f low



The sch em e fo r in jec t ion of spent geothe rm al f lu id

a t

Val les Ca lde ra

i s

b a s i c a l l y t h e s a m e a s t h a t a t He b er . Ho we v er , t h e d i s ta n c e f r o m

the power p lant to the ne ar es t edge of the in jec t ion f ie ld is

1 ,524

m e t e r s

( 5 , 0 0 0 fee t ) ins tead of 3 , 0 48 m e t e r s (10 ,000 fee t used by Chevron a t

He b e r , a nd th e we l l s a r e s p a c e d a t

3 0

a c r e s p e r w ell .

r equ i rem ents a r e sum ma r ize d in the fo llowing tab le :

Injection well

No.

of We lls R.eq uired

P ro c e ss In i t ia l F i e ld Condit ion Fina l Condi t ion

F l a s h e d s t e a m

4 4

B i n a r y 3 3

Hybrid 3 3



VA V-5

E- T- E l

R E F E R E N C E DR W ING

W N ~

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P RCO NO E NS L

k

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GEZSATO

COOLlClG TO WE R

p l VP-I

CONDEk5KE

W P

V A C U ~MP

2 \ 09

IPH

5 3

CW

4900 CW

194

W

V A L E S

CALDERA

I

E P R

1



V

E l E 2

1 1

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STW ZNEWIUTOR STEAM YTEXCUWGER

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C C U H V U T ~

C O O C IU G T O W E R

P

C I R C U L A T I O N P U M P

P 2

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C I R C U L A T I O N

PUMP

STREAM PROPCRllES



V

I E V - 2 G

B R I N E / S T ~ EPARATOR

M I N E -

W C-CHANGER

~ T MRUBBER

SURFACE CWMNSER

TURBINE

k

E - 4

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SUCTlOLl

CWDENYR

V

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AUFULATOR

24bMmv? M~0R

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I6

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V A C W M PUMP

WL INSW UMP

54

GPr



RA FT R.IVER CONVERSION PL AN TS

THE R.ESERVOIR

The Raf t R iver hydro the rmal rese rvo i r is located in south-centra l

Idaho, approx imately 40 m il es sou theast of Burley.

T he a r e a l i e s

a long the Raf t River Val ley a t an e levat ion of about 1 ,400 me te rs

(4 ,800 fee t ) . At th i s e leva t ion the a tmos pher ic p r es su re i s 82 kPa

( 1 2

psia) .

A i r t e m p e r a t u r e s

at

the s i te range f ro m 38 C (100 F ) i n s u m m e r t i m e t o

a s lo w a s -34 C ( - 3 0 F ) in the wi nter t im e. The wet bulb tempe'rature in

the a r ea re ach es o r exceeds a maxim um of 18

C

(65

F )

one per ce nt of

t h e t i me d u r in g t h e s u m me r

months. Th is t em per a tu r e was used fo r

de sign.

T h e a r e a

i s

rugged with mountains reachin g

to

a bo u t 3 ,00 0 me t e r s

(9 ,800 fe e t ) e levation.

com es c lose to the geo the rmal p lan t s i t e .

U.

S. Highway 30

is a

three-lane highway which

Water f or m akeup to the cooling tower w i l l be taken f r o m the Raf t River

o r f r o m s u r f a c e wel ls .

Produ ct ion wel ls and in jec t ion we l ls have been a l located 30 ac re s of

g round a r ea pe r we l l.

a re as of the geothermal anomaly.

In ject ion wel ls wi l l be located on the cooler



The ge o the rm al p roducing we l l s m us t be pumped to ach ieve h igh p ro -

duct ion r a tes . It h a s b e e n a s s u m e d t h a t th e d i f f e r en t i al p r e s s u r e

requ i red to p roduce the we l l s

i s

2,068 kP a (300 ps ia) and that the

p r e s s u r e r e q u i r e d to i n j e c t th e b r i n e wi ll i n c r e a s e to 2 ,7 5 8 k P a

(400 psi a) a t the wel l head. We have used the sa m e pumping ra te of

295 m3/ hr (1 ,300 gpm/wel l ) a s

a t

Heber .

/-

The cor ros i on and fou ling ch arac te r i s t i c s of the Raf t R iver re s e rv o i r

fluid a r e not known.

T h e r e f o r e , it was as sum ed that the f lu id would

h av e t he s a m e c h a r a c t e r i s t i c s a s the Heb er rese rv oi r f luid . We have

specif ied the use of s te e l in a l l equipment exposed to the re se rv oi r

f lu id o r f l a shed s team , excep t the s t ea m tu rb ines and su r fa ce con-

d e n s e r s w h e r e s t a i n le s s s t e e l i s used.

FLASHED STEAM PLANT

A pro ce ss f low d iagra m of the f l a shed-s te am p lan t i s shown in d rawing

number 7523-D-3207.

f l ow r a t e of 7. 39 M

kg/hr

(16 .3 M l b s / h r ) .

f i r s t - s ta g e f l a s h d r u ms

at

a p r e s s u r e of 290 kP a (42 psia ) . The

f i r s t -

s t a g e f l a s h p ro d u c e s 2 4 1 ,0 0 0 k g / h r ( 53 2 ,0 0 0 l b s / h r ) of p r i m a r y s t e a m

which pa sse s th rough a s te am sep ara to r be fo re reach ing the tu rb ine -

gen era t or a t a pr es su re of 284 kPA (41. 2 p s i a ) an d a t e mp e r a t u r e

of

132 C (270

F).

The ho t r e s e r vo i r f lu id en te r s the p lan t a t a

T he

brine

f lows

into

the

L iq u id f r o m t h e f i r s t - s t a g e f l a s h d r u ms f l ows t o t h e s e c o n d- s t ag e f l a s h

d r u m s w h e re

i ts

p r e s s u r e

i s

reduced to 114 kP a (16.6 ps ia) . The



tower a pproach and resu l t s in an expens ive tower.

me t r i c s tudy in which cold wa te r t em pera tu re was ra i sed s l igh t ly 1. 7

C

(3 F) inc rea sed the co st of the condenser m or e than it reduced the

co st of th e cooling tow er.

dens ing p re ss ur e was ra i sed s l igh t ly to

15

kPa (2.2 in. Hg) prod uced a

lo ss of ef f iciency and an in cr ea se in br i ne consumption. The pros pec-

t ive cooling tower capi ta l cos t saving was mo re than offse t by inc rea sed

br ine cos t s and inc re ased coo ling tower fa n horsepower .

However,

a

p a r a -

Sim ilar ly , another s tudy in which the con-

Turbine se lec t ion was di f ficult for the p lant .

bucket s i ze ment ioned e a r l i e r ,

55

MWe of output could be obt aine d only

with a four-flow , two -case m achine.

with a two-flow tur bin e was abo ut 38 MWe.

With the l imitations on

The ma xim um output a t ta inable

Noncondensable gas f low has been es t im ated a t 405 kg/ hr (893 lb s /h r)

base d on a b r ine ana lys i s .

den ser wi th vacuum pumps.

13 .8 kPa (2 in. Hg) , two s tages a r e required .

f i r s t - s ta ge pumps and two medium-s ize second-s tage pumps .

i s

provided for the d isp ers a l of the noncondensable gase s .

T h e s e g a s e s a r e r e mo v ed f r o m t h e c o n-

T h e r e a r e fo u r l a r g e

Bec ause of the low condensing pr es su re

A

s tack

A sum ma ry of per t inen t des ign data for the p lant

i s

a s fo llows:

R .ese rvo i r f lu id ra te

Gen erato r output

55.0

MWe

Pumping work

3 .7

MWe

7 .4 k g / h r ( 16 .3 M l b s / h r )



c

r e needed to me e t the p r oc es s f low requ i rements .

the p lan t i s s im i la r to the Heber b in a ry p lant .

In o the r re s pec t s ,

A su mm ary of per t inen t des ign data for the p lant i s a s fo llows:

R .ese rvo i r f lu id ra t e

Hydrocarbon f lu id ra te

Ge ner ato r output 67.5 MWe

Pum ping wo rk 15.9 MWe

Cooling tow er wo rk 1.6 MWe

50 .0 MWe

et power

Re ser vo ir f lu id /net kwh 100 kg (220 lb s)

5.0 M k g / h r ( 11 .0 M l b s / h r )

4 .8 M kg/hr (10.6 M l b s / h r )

HYBRID PLANT

A mixture

of

5 0 m o l

70

propane and 5070 sobutane was chosen as the

working fluid in the bina ry power cycle of the hy brid plant beca use of

the low temper a tu re of the r es e r vo i r f lu id.

des igned to gener a te 57 MWe, and the s te am f las h unit wi l l genera t e

9 MWe.

pe r we l l f luid f low ra te .

The b ina ry sec t ion i s

The se lec ted des ig n condi t ions opt imize the power gene ra ted

The pr oc es s flow dia gra m, drawing number 7523-D-3254B, shows the

plant operating condition. Th is p lan t , l ike the b ina ry p lan t , i s ch a rac -



but down-hole pumps a r e used to boost the f low to the des ign r a t e of

1 ,300 gpm pe r we ll .

g e n e r a l l y t he s a m e

a s

at Val les Caldera . At Raf t Rive r only in i t ia l

f i e ld condi tions a r e cons ide red ,

s ince any dec line in the res e rv o i r

t em pera tu re would resu l t in an excess ive in c rea se in p lan t and opera t ing

cos t s .

table.

The product ion and in jec t ion piping s chem es a r e

F lows and wel l r eq u i remen ts a r e sum mar ized in the fol lowing

No. of Wells Require d

P r o c e s s R.equired Flow of Well Flui d Prod uctio n Injection

F l a s h e d s t e a m 7 . 4 M kg/hr (16 .3 M l b s / h r ) 2 7 13

Binary 5 .0 M k g / h r

(11.0 M

l b s / h r ) 1 9 9

Hybr id 5 .4 M k g / h r ( 1 1 .9 M l b s / h r ) 20 10



V

PRIMARY FLASH VESSELS

6

CT

OOLING

T O W E R

P 2

OOLING W TER PUMP

I35 Doo

PH

z ms

L W

Vp I

P

FIRST

ST

PM

VACLIUM D U M P S

,

ib

US0

GFM

5 - 0

KW

COOLING TOWER

T

R E F E R E N C E D R A W I N G

on.wWGm 787L



P-l

H

C IR GTIOU

UMP

S T R E A M PROPERTIES

THE

BEN HOLT

CO

- ' L '

BINARV

AFT

RIVER

OWER

D HLANT

OPTIMIZED

CA 5E

-7

F Q I

K

A

s ,=w

13buLD FOE HTIHITE

0

WVJY#

c

0

U L



REFERENCE DRAWING

O CO nT c

V 4

W TER

TR P

SILENCER

T I

C O ~ L ~ T ~ W E

V CUUM

W P

W W

THE BEN HOLT CO



THERMODYNAMIC B1NAR.Y CYCLE ANALYSIS

In the deve lopment of the bas e b inary ca se s fo r the th ree s i te s , p r e -

l imi nary op t imiza t ion s tud ies we re mad e , and on the bas is of these

f ind ings the p r oc es s des ign fo r the base ca se was es tab l i shed .

Subsequently , a s creen ing s tudy was m ade to dete rm ine which f luids

and cyc le chara c te r i s t ics appe ared to be op t imal fo r ea ch of the

re se rv o i rs be ing stud ied . The re su l t s of th is s tudy a r e p re sen ted in

th is sec t ion .

The cyc le under cons idera t ion i s a s imple Rankine cyc le

as

shown in

Fi gu re 1. The working f luid i s a l ight a l iphat ic hydrocarbon. The

liquid working fluid

is

pumped to the opera t ing pres su re .

It i s

then

vapo rized by hea t exchange with the ge oth erm al f lu id .

gen era ted by passin g the working f luid through an expansion turbine.

The cycle

i s

com pleted by condens ation of the working fluid.

P ow er

i s

S eve ra l a s sumpt ions have been made in o r de r to min imize the ca s e

s tud ie s and ensu r e tha t t he c a s e s a r e comparab le .

tem per a tu re d i f fe rence (LMTD) for the condenser was 8 C (14 .4

F )

i n

a l l c a se s ; t h i s co r r e sponds to a 6 C (10

F )

cool ing wate r tempera ture

r i s e a n d 6 C (10 F ) appro ach for a pur e hydrocarbon . The min imu m

hydroca rbon exchange r app roach t emp e ra tu r e w as s e t a t

8

C (15

F )

fo r

all

case s .

No

working flu id condens ing pr es su re s be low loca l a tm os-

p h e r i c p r e s s u r e w e r e a ll ow ed .

The log mean

T he me teo ro log ica l va r i ab le s w e re



T he geo the rm a l f lu id r a t e

is

de te r min ed by

a

graph ical technique

uti l izing the tem per atu re- ent hal py plot of the R.ankine cycle .

known wel l flu id tem per a tu re and approach in the hea t exchanger , the

geo the rma l fluid r e j e c t t em pe ra tu re can be de termined .

ba lance

wil l

then prov ide the f low ra t es and thermodynamic s ta te o f

all

t he s t r ea m s in the cycle.

Exam ples of tem pera ture -en tha lpy p lo ts fo r

a s u p e r - c r i t i c a l a nd s u b c r i ti c a l c y c le a r e i l l u s tr a t e d i n F i g u r e s 2 and 3 .

With

a

A

hea t

The var ious cyc le permuta t ions we re op t imized wi th respe c t to geo-

the rm al f lu id consumpt ion .

t e m p e r a t u r e , p r e s s u r e a n d f lu id c o m po s it io n w e r e v a r i e d i n s e a r c h of

the lowes t well f lu id ra te .

mixed f luid cyc les , the condenser LMTD was he ld cons tan t . Seve ra l

gen era l s ta tements can be mad e about the op t imum cyc le fo r

a

given

case .

F o r e a c h r e s e r v o i r c a se ,

the cycle

In o r de r to p rope r ly compare pu re and

1.

2.

3 .

4.

A s th e r e s e r v o i r t e m p e r a t u r e i n c r e a s e s ,

a heavie r molecu la r

weigh t f lu id i s p re fe ra b le .

A s the m olecu la r weigh t

of

the work ing flu id incr ea se s ,

the

o p ti m a l s y s t e m p r e s s u r e w il l d e c r e a s e .

A mixed f lu id wi l l genera l ly re su l t in

a

lower condens ing pressure

s ince

i t

does not have a constant condensing temperature .

a l lows a cl os er ap proac h to the cooling wat er enthalpy curve.

This

The op t imum opera ting condi tions wi l l genera l ly res u l t in

a

min i -

m um amoun t

of

supe rhea t in the tu rb ine exhaus t .

. . . . . . . . . . . .. . . . . . . . . - .. -- __.



in the desig n cr i t er ia and knowledge of loc al condit ions. It i s t h e r e f o r e

not f ea s ib l e f ro m a

t ime

and expense s tandpoin t to t r y to c a r r y the op t i -

miza t ion

t o

too f ine

a

degree .

c y c le s we s h a l l r e f e r t o a s p r e f e r r e d w i l l b e c lo s e t o t he t r u e o p t h u m

condi tion . The ma jor var iab les a r e : opera t ing tem per a tu re , opera t ing

pr es su re and work ing f lu id . A s between different ca se s tudies , the

t emp era tu r e w i l l not be va r i ed by l e s s than

3 C

(5

F )

i n s ea rc h of an

op t imum; the p r e s s u r e w i l l not be v a r i ed l e s s than 70 kP a (10 p s i ) ; and

the com posit ion of a mi xt ur e will not be va ri ed l e s s than 10% of one

component.

It can, however, be expected tha t the

The res ul ts of the Hebe r

s tud ies a r e tabu la ted in Table

3

.

Twenty

d i f fe ren t simple binary cyc les wer e eva lua ted

f o r

the Heber des ign

condit ions. Since much of th is inform ation was usable fo r the other

f ie lds , fewer case s wer e requ i r ed in the la t e r s tud ies . In it ial ly, a

bas e ca se w as s e l ec t ed to s e rve a s a s t a r t ing poin t.

cycle a t 4 , 137 kP a (600 ps ia ) and 149

C (300 F )

was se lec ted , based on

our p rev ious exper ience a s being

a

r ea sonab le ca se f ro m wh ich to

optimize.

The bas e c as e prod uced 7.203 MWe p er mi llio n pounds of we ll fluid.

A s u m m a r y

i s

l isted below:

A

pure isobutane

All c as es we re s iz ed fo r a net e l ec tr i ca l output of 50 MWe.

Well fluid

Shaft work 87,966 BHP

3 ,148 ,000 kg /h r (6 , 940 ,000 lb s /h r )



The power product ion f r om the cycles des igned fo r th is s i te ranged

fr om 7. 52 MWe/m ill ion pounds well f luid fo r the be st cycle to 6.38

MW e/mill ion pounds well fluid for the le as t efficient .

DE PLE TED RESERVOIR

Pre l im ina ry f ie ld s tudies indicate that the well f lu id tem pera ture wi l l

dec rea se ove r a per iod of t im e f ro m 182

C

(360 F ) to 163 C (325 F) . In

ord er to p rov ide fo r th i s even tua li ty , a s e r ie s of cas es were run a t th i s

lower t empera tu re .

hydrocarbon cycle a s the bas e cas e for the 182 C (360

F )

r e s e r v o i r ;

only the amount of well f luid requ ire d to produce

50

MWe net was

changed.

(11. 3 M l b s / h r ) .

The bas e c ase fo r th is s i tua t ion ut i l ized the sa me

The well f luid consumption i ncr eas ed by 63% to 5. 13 M k g / h r

Seve ra l o ther cycles we re invest igated in or de r to improv e on th is , and

it was found that

a

m ix tu re of 3570 pro pa ne and 65% isob utan e w ith a

turb ine inl et condition of 4, 137 kP a (600 ps ia ) and 129 C (265

F )

provided a s ignif icant de cre ase in br ine consumption.

t h i s c a s e i s shown:

A s um m ar y of

Well f luid

Shaf t work 92,255 BHP

G en er al output 67.42 MWe

Pum ping wor k 12.24 MWe

4 ,51 3 ,0 0 0 k g / h r ( 9 ,95 0 ,0 00 l b s / h r )



Ge nera l output

6 2 . 6 9

MWe

Pum ping work 8.10 MWe

Cooling tower work

Net product ion

4.59 MWe

50 .00 MWe

Se ve ral cycles us ing m ixtu res of i sobutane and isopentane we re s tudied,

but the op tim um cycle was found to be a m ixt ure of 90% isopenta ne and

1070 no rm al hexane.

and 174 C (345 F) .

Since the f ield i s a t an elevation of

9 , 0 0 0

feet ,

th i s i s sa fe ly above

a t m o s p he r i c p r e s s u r e .

Th is cyc le was opera ted a t 2 ,482 kPa (360 ps ia )

The condens ing p re ss ur e

i s

102 kPa ( 14 .8 ps ia ) .

A su m m ar y of this cycle

i s

shown below:

W e l l f luid

Shaf t work 76,544 BHP

Ge ne ral output 55.94 MWe

Pum ping wo rk 3. 13 MWe

Cooling tow er wo rk 2.81 MWe

1 ,1 8 5 ,0 0 0 k g / h r ( 2 ,6 12 ,0 0 0 l b s / h r )

Net product ion

50.00

MWe

This cycle shows a 1970 impro veme nt ov er the bas e case .

noted that the working f lu id in th is ca se i s not much dif ferent f r om pur e

isopentane.

would no t be ve r y in fe r io r to th i s cyc le . Th is i s , in fac t , the case .

It shou ld be

It

might be exp ected that a c ycle using isopentane alone



Gene ral output

Pumping w

or

k

Cooling tower work

Net production

61.78 MWe

6.38 MWe

5.40 MWe

50.00 MWe

/-

Sev eral mix tur es of propane and isobutane we re found to be m or e

eff ic ient than the bas e c ase .

isobutane opera ted a t 4 ,137 k Pa (600 ps i a) and 121 C (250

F).

sum ma ry of th is cycle

i s

shown below:

The b es t one w as 5070 prop ane and 5070

A

Well fluid

5 ,006 ,800 kg /h r (1 1 ,0 4 0 ,0 0 0 l b s / h r )

Shaft work

Ge nera l output

Pumping work

Cooling tower work

N e t product ion

92 ,466 BHP

67.58 MWe

11.93 MWe

5.65 MWe

50 .00

MWe

The power product ion of the va r iou s cy cles s tudied ranged f r o m 3.412

to 4. 528 MW e/m illio n pounds of w ell fluid.

COMPOUND CYCLES



e lec t r i c i ty is low.

a t a h igh t em pera tu re to main ta in the t t in - l ine t ' h a rac te r i s t i c of the

p r o c e s s .

in the pr im ar y cycle, and the overa l l e f fic iency of the cycle

i s

general ly l e ss than that of the s imple cycle.

This i s because the p r i m ary cycle mu s t r e jec t hea t

The h igh re jec t t emp era t u re c auses

a

low Car not efficiency

The th i rd poss ib le cycle avoids th is problem.

F i g u r e 4.

the given geothermal f luid.

f r o m the pr im ar y cycle , be low the p inch point, and used to heat a

secondary cycle .

The effective geo ther ma l f luid heating cur ve then

conform s m ore c losely wi th the shape of the hydrocarbon heat ing curve .

If des ired , the sa m e pr inciple can be appl ied to the seco ndary cycle

resul t ing in a three-cyc le proc ess . When evaluat ing the des i rabi l i ty

of a compound cycle,

a s ignif icant inc rea se in perf orm anc e over the

s imple cycle should be observed i n ord er to jus t i fy the addi tional

expens e of equipm ent f o r the s econda ry cycle.

It i s i l l u s t r at e d i n

The p r imary cyc le

i s

se lec ted to be the opt imum cycle for

A s ide s t re am of ge otherm al f lu id i s taken

Two compound c ycles we re s tudied using the bes t s impl e cycle a s a

bas i s ( s ee Tab le

3

). The res ul t s a r e shown below:

Simple Cycle

3.041 MWe/M kg

(7.

518 MW e/M lb s) of well flu id

Dual Cycle

3.341 MWe/M kg (7.381 MWe/M l bs ) of we ll f luid

Treb le Cycle

3. 392 MWe/M kg (7.478 MWe/M lb s) of well f luid

Since fo r a reasonably wel l opt imized ca se the compound cycles fa i led



CON O NS U

COQLIUG

CIZ CULATING

PUMP

F I G UR

SUPERCRITICAL BINARY CYCLE TEMPERATURE-ENTHALPY DIAGRAM



2

4

6 8 1 12 14 16 18

HEAT CONTENT BTU/ WORKING FLUID



FL UID

V PORIZER

OOLlhiG

W TER

CIRCUL TING

TURBO GENERATOR

kl=m

SECOND RY CYCLE

\ /

C O O L 1

NG

._ .

I

WATER

1

CIRCULATING

PUMP

FIGURE

4

THE BEN HOLT CO

'

OMPOUUD

BINARY C Y C L e

DUAL)

<

CPR I

CYCLE POIHTS

T A B L E

2



COND. TEFlP.= 1 0 4 . 4 COND. PRESS.=

57.8

CONDENSEE DUTY= 14i. 'E. 48ETU /=

VAP.

IftLET TEMP.= 103.5 PUMP D I S C H . P =

550 .0

EXP. TEMP.= 31 0 . 0 OP.

PRESS.=

500 .0

EXP OUTLET-

T

= 137.0 P = 59 . s

H

= 146 . 648

V= 1.472355

TC = 786.410 PC = 5 3 1 . 4 7 0 MOL. UT. = 65.14

COMPl X = 0.500 COFlP2

x

= 0.500

C-W

T E M P . = 9 0 . 0 C-W DT 2 6 . 5

CCND. A F ' F E O A C t i

= 14.4

COND. DP 2 . 0

VAP.

HPPEOHCH

= 1 5 . 0 VAP. DP

= 5 0 . 0

EXP. EFF.= 0.650 P u w E F F . = 0 . 8 0 0

H.P. ENTR=

1.1563

L.P. ENTF:=

1.1599

T A B L E

2

( C o n t i n u e d )

HEf i l1

lG C VF 'VE

T 1 = lOS.5

I 1

=

3 237

v

1 =

0.028Z0.1



1 2 = 120.0 t i E =

9.%4

v 2 = 0 . 0 8 y 2

v

3

=

0.0,>.?292

3 =

140:o

H 3

=

21.894

T 4 =

160.6 H

4

=

34.189

v

4 = 0.03nnz.?

T

5

=

180 .0

tl

5

= 46 .903 V

5

=

0. 031 Ciijc.

1 6 =

200 .0

H 6 = 60.114

\

6 E

o.fJ::>rJg;.

1 7 =

220 .0

H 7 =

73.450

V

7 = 0.0?3414

1 8

=

2 4 0 . 0

H 8 =

b3 . 631

v 8 =

0.025136

T 9 =

2 6 0 . 0

t i 3

=

104.618

$/ 9 =

0.037544

T i 0

=

23u.0

H I 0

=

123.

n

,410

=

o.[l41:::Zo

1 1 1

= 290.0

H11

=

134.152

v11

[ I ( lJf583

T i 2 =

316.0

H l Z =

188.0:X V12 = 0.11:+1245

T 1 3 =

317.0 H13 = 190 .155

V 1 3

= 0. 104'335

114

=

315.0 H14 191.476 V14 0.108160

f l 5

= 319.0 H15

=

143.62'3 L'15 = 6.111059

1 1 6 = 320.0 H16

=

195.170 V16

=

0. 113751

1 1 7

=

3 21 .0 H 1 i

=

146.574 4 1 7

=

0.116130

718 = 322.0 4 1 9

=

197.929 v10: = 0 . 1 1 8 4 3

v 1 9

=

0.12(?;24

1 9 = 323.0 H13 = 199. 193

fZO =

324.0 H20 = 200.421 V20

=

O.l i2 .556

721 = 325 .0 921 = 201.553 ' 21

=

0.124551

T22 = 326.6 H2:,>

=

2 0 2 . i S l v2,>

t.&:;G

T 2 3 =

3 2 6 . 7

u >3

;1:14.6:5

;?Is

Ij.12152:

f 2 4 326.; u.24

=

2 0 4 . 6 4 1 . i t 4 =

o

1315.33

. . ~ O

~ 0 ~ ~ ~ . 0 0 0 . . . 0 ~ 0 0 0 0 0 ~ ~

I -

TABLE 3



Operat ing

W o r k in g F l u i d P r es su r e

Composi t ion psia

B ase C ase I so bu t ane

Isobutane

80 iC4-20 iC5

80 iC4-20 iC5

80 iC4-20 iC5

80 iC4-20 iC5

20 C3-80 iC4

20 C3 -80 iC4

50 C3-50 iC4

50 C3-50 iC4

80 iC4-20 iC5

50 iC4-50 iC5

50 iC4-50 iC5

50 iC4-50 iC5

50 iC4-50 iC5

50 iC4-50 iC5

50 iC4-50 iC5

30 iC4-70 k iC5

65 iC4-35 iC5

80 iC4-20 iC5

Dual Compound Cycle

Treb le Compound Cycle

D E P L E T E D

B a s e C a s e

-

Isobu tane

2070 C3-80'70 iC4

2070 C3 -80 iC4

20 C3 -80 iC4

80 iC4-20 i C 5

80 iC3-20 iC4

20 C3 -80 iC4

50 C3-50 iC4

50

C3 -50 iC4

35 C3-65 iC4

35 C3-65 iC4

35 C3 -6570 iC4

THERMODYNAMIC ANALYSIS OF BINARY GEOTHERMAL POWER CYCLES

CASE STUDY SUMMARY

HEBER RESERVOIR

Operat ing Condensing

T e m p e r a t u r e T e m p e r a t u r e

F

Geothermal F lu id

In let Out let

M

I b s I h r T emp er a t u r e T emp er a t u r e

W o r k ~ n g G e n e r a t o r

Fluid Output

M lbs /h r MWe

u mp ~ n g C o ol i ng T o wer

Work Work

MWe MWe



T AB L E 4

THERMODYNAMIC ANALYSIS OF BINARY GEOTHERMAL POWER C YCLE S

CASE STUDY SUMMARY

VALLES CALDERA RESERVOIR

Op er a t i n g Op er a ti n g C o n d en s i n g Geo t h e r ma l F l u i d W o r k i n g Gen er a t o r

P u mp i n g

Cool ing Tower

W o r k i n g F l u i d P r e s su r e T emp er a t u r e T emp e r a t u r e I n l e t Ou t l e t F l u i d Ou t pu t W o r k W o r k

C o mp o s i t i o n p s i a F F M l b s / h r T e m p e r a t u r e T e m p e r a t u r e M lbs /h r MWe MWe MWe

B as e C ase I sob u t an e 6 0 0

80% iC4-10% iC5 600

50% iC4-50% iC5 600

20% iC4-80% iC5 500

80% iC5-20% C6 350

70% iC5-30% C6 320

90% iC5-10% C6 360

I so p en t an e 4 0 0



TABLE 5

THERMODYNAMIC ANALYSIS OF BINARY GEOTHERMAL POWER CY CLES

CASE STUDY SUMMARY

RAFT RIVER RESERVOIR

Operating Operating Condensing Geothermal Fluid Working Gene rato r Pumpin g Cooling Tower

Work ing F lu id Pre s s u r e T e mpe ra tu r e T e mpe ra tu r e In let Ou t le t F lu id Ou t~ u t Work Work

Composit ion ps ia F F M lbs hr Tempera ture Temp eratu re M lbs /hr MWe MWe MWe

B a s e C a s e I s obu tane

Propa ne

50 C3-50 iC4

50 C3 -50 iC4

50 C3-50 iC4

50 C3-50 iC4

35 C3-65 iC4

60 C3-40 iC4

60 C3 -40 iC4




In o rde r to a ss e ss economic feas ib i li ty fo r the th r ee s i t e s , the fol lowing

s t e p s a r e n e c e s s ar y :

Pr ep ar e es t im a tes fo r bo th p lan t and fi e ld ins ta l l a tions fo r each

p r o c e s s at each si te , a tot al of 18 est im ate s.

P r ep ar e opera t ing and main tenance (O&M)cos t e s t im a tes fo r bo th

p lan t and f i e ld ins ta ll a t ion fo r each p roc ess

at

each s i te .

Bas ed on the foregoing es t im ate s , ca lcula te the se l l ing pr ic e of

energy by the p roducer to the u t i li ty fo r each p ro ces s a t each s i t e .

F ina l ly , e s t ima te convers ion and t rans mis s ion cos t s fo r ea ch

p r o c e s s at each s i te .

P re p ar e sensi t iv i ty analys es in ord e r to examine the effec t of

var ious fuel pr ic ing s t r a te gie s on energy and power co sts .

CAP ITAL COSTS

Capi ta l co s t e s t im a tes fo r the th re e Heber convers ion op tions and fo r

one Heber f i e ld ins tal l at ion a r e p resen ted in F i gur es

5 ,

6 ,

7

and

8.

T h e po wer p l a nt c o s t s f o r e a c h p r o c e s s a t He b e r a r e a s f o ll ows :



Million Dollars

F l a s h e d s t e a m

2 6 .

8

B i n a r y 28. 5

Hybrid

36. 6

The se cost s exclude the c ost of land and any cos ts inc urr ed by the

owner ass ocia ted with des ign and construct ion.

The cost of the surfa ce ins ta l la t ion for the b inary plant a t Heber is

es t ima te d to be

$7,800,000.

the injection pum ps, productio n piping, injection piping and relat ed

installat ions.

excluded.

somewhat h igher than would ac tua l ly be incu r red a t the s ta r t .

This co s t inc ludes the down-hole pump s,

The c ost of comp leted productio n and injection we lls i s

The cost is based on end-of-run condit ions and

i s

the re fo re

Tab le 6

ins ta l l a tions a t each s i t e .

cos t e s t im a tes by p ro ra t ing the cos t d i f fe rences in each ca tegory of

wo rk and each piece of equipment.

T h e s e d i f f e re n c e s we r e f u r t h e r

adjus ted to ref le c t loca l condit ions.

T h e e s t i ma t e s

of

t r a n s m i s s i o n

c o s t s a s s u me t h a t a t He b e r , t h e p o wer

i s

t r an smi t ted to a load cen te r

a t

El

Centro;

at

Val les Ca lde ra , the power i s t r ansm i t ted to

Los

Alamos (about

20

mil es ) ; and a t Raf t R iver the power

i s

t r a n s m i t t e d t o

pres en t s cap i ta l cos t s fo r the power p lan ts and t ran sm iss io n

T he p l a n t c o s t s we r e e s t i ma t e d f r o m He b er

dri l l ing condit ions (young volcanic form at ion s , deep wel ls , rem ote



locations).

gue sse s , s ince we have no actua l data.

of

$600,000

i s

c lose to ac tua l pub l ished d r i ll ing cos t s fo r the a re a .

In th is cas e the wel l co s ts a r e nothing m or e than educated

The co st of R aft Riv er wel ls

In each case, we have as sum ed that about 20% of the deve lopmen t we lls

wil l be d ry holes.

eas i ly be low fo r a young volcanic form at ion l ike V al les Ca ldera .

Again , th is f igur e i s an educated gue ss and could

T o t al we ll c o s t s v a r y f r o m a low of $5. 9 mil l ion for the Heber b inary

p r o c e s s t o a hi gh of $24. 2 mil l ion for the Raf t River f lash plant.

The surfa ce ins ta l la t ion co sts ( including down-hole pumps fo r Heb er

and Raft Ri ve r) var y f r om a low of $5. 9 mil l ion

at

Heber

to

a high of

$18 mill ion a t Raft River.

FI EL D O PERATING AND MAINTENANCE COSTS

Table

9

pr es en ts es t im ate s of f ie ld opera t ing and maintenance cos ts

fo r the n ine cases .

Table 8.

f ield office burden and G&A i s est im ate d to be $253,000.

cons ide red th i s cos t to be a constant for a l l cases .

The es tim at e of the f ield staff portion

is

shown in

The annual cost of the f ield staff including s al ar ie s, benefits ,

We have

Produc ing we l l ma intenance co s t s a r e e s t im a ted f ro m suggest ions

made by Chevron fo r Heber a s fo llows :

2.

Ma j or r e me d i a l we l l wo r k

is

done once eve ry two ye ar s for each



wel l

at a

co s t of $80,000.

3 .

One injection well will be abandoned by the end of the p roj ec t

at

a

co st of $50,000.

C o s t s f o r all o t h e r cases we re p ro ra ted by the number

of wells.

Annual surface- ins ta l la t ion maintenance ( labor and mater ia ls)

i s

calcu-

la ted at four perc ent of the in i t ia l capi ta l cos t fo r Heber and Raf t

R i v e r, w h e re th e w e ll s a r e p u l p e d ,

and two percent a t Val les Ca ldera

wh ere they a r e not.

Down-hole su rveys a r e f igured a t $1,000 pe r ye a r pe r we l l.

The c ost of pumping e lec t r ic i t y was f igur ed a t 2. 0 cents /kwh.

the pumped wel l s th i s cos t r ep r ese n t s abou t one- th i rd of the to ta l

opera t ing and maintenance expense .

F o r

Tota l f i e ld operat ing and main tenance expense va r i es f ro m $ 1 ,2 6 3 ,0 0 0

p e r y e a r f o r t h e Va ll e s C a l d e r a b i n a r y pl a nt t o

a

high

of

$4,181,000

fo r the Raf t R iver f l a sh p lan t.

The monthly opera t ing and maintenance co sts (excluding pow er) p e r

wel l a r e in the range o f $6,000, near ly twice a s h igh a s would be

e x p e c te d f o r

a typical

oil w ell .

COST

O F

GEOTHERMAL POWER



In es t im at ing the cost of geoth erm al power de l ivered to a uti l i ty load,

we a s s u me t h a t

a

pr iva te ly owned p roducer wi l l se l l the rm al energy

to an investor-owned publ ic u t i l i ty who wil l own and ope ra te the power

p lan t and t ransm iss io n l ines .

Thus , the r e a r e th r ee e lements of cos t

to be considere d.

1.

Pr od uce r ' s se l ling p r i ce of the rm al energy to the u ti li ty

2. The ut i l i ty 's cos t of genera t ing e lec t r i c i ty

3 .

The u t i l i ty ' s t r ans mi ss io n cos t to

a

load cen te r

T h e r e i s

a

minim um sel l ing pr ic e below which

a

producer would not

rece ive an adequa te re t u rn on h i s inves tment an d /o r an adequate

incent ive to continue an explora t ion pro gr am and theref ore would not

en te r in to

a

c o n t r a c t t o s e l l t h e r ma l e n er gy .

T h e r e

i s

a l s o

a

maximum p r ic e which

a

ut i l i ty can afford to pay for the

the rmal energy .

T h e P r o b l e m

The p rob lem to be add ress ed in th i s s tudy

i s

two-fold in scope.

f i r s t a s p e c t i s to e s t ima te the cos t o f geo the rma l power fo r th re e

p r o c e s s e s

at

the th re e s i t e s . The es t im a tes mu s t be made on a

The

1.

The geological and geophysical metho ds used successfully in oil



2.

3 .

4.

5.

and gas exp lo rat ion a r e not nec essa r i ly use fu l o r may requ i re

som e adapta tion to be useful in a geotherm al environment.

Drilling technology i s abou t the sa me ,

except f or the effect of

tem pera tu re and the p rob lems assoc ia ted with d r i ll ing th rough

rock ra the r than sed imenta ry fo rmat ion .

Oi l and gas ma y be t r a nspo r ted to mar ke t and both a r e so ld in

nat ional and in ternat ional m ar ke ts through wel l es tabl ishe d

marke t ing channe ls , whe reas g eo the rma l energy mus t be so ld to

a uti l i ty who will build the power plant in the producing field.

Thus , the producer can ge t no i n co me f r o m a g e o t h e r ma l

res e rv o i r un ti l the power p lan t

i s

buil t and operating.

The ut i li ty must have conf idence that the re se rv oi r wi l l furni sh

the rm al energy for an extended per io d of t im e (normal ly

30

y e a r s ) .

T i t l e to the geo the rm al wa te r

i s

not wel l es tabl ished , unlike oil

a nd ga s r e s e r v o i r s wh e r e t h e r e i s se ldom the p rob lem

of

owner -

ship.

Thus , the r i sk fa c to rs a r e d i f fe ren t be tween exp lora t ion and deve lop-

ment of o i l and gas on the one hand and geot herm al res er vo ir s on the

o the r hand , bu t the sam e cos t -o f - se rv ic e approach used in the o i l

indus t ry may be used fo r e s t ima t ing the cos t

of

fuel.

W e

have developed

a

compu ter pr og ra m which calcula tes the cost of

f luid requ i r ed a t a given si te . A knowledge of the reservoir



c h a r a c t e r i s t i c s wil l indicate the nec ess ary num ber of product ion

and in jec tion wel ls , the f ie ld layout and the r eq uir ed col lec t ion

and d istr i buti on piping. With th is informat ion, the var iou s costs

involved with br inging the f ie ld in to product ion can then be

es t ima ted .

2. Capita l Inve s me n t

The cap i ta l inves tment fo r a g e o t h e r ma l p r o j e c t is the money

requ i red by the p ro jec t fo r which a r e tu rn on inves tment is

expected.

that none of the se funds a r e obtained by borrowing.

ponents of th e c api ta l investment a r e a s fo llows:

F o r the pur pos es of th is invest igat ion,

it

i s a s s u m e d

The com-

a.

Ex do ra t i on and Land Acau is it ion Cos t s

This rep res ent s the money spent in geological and geophysical

re se a r ch , exp lo ra to ry d r i l l ing , bonus payments and o the r

cos t s invo lved with es tab l i sh ing the p re senc e of an exploitable

g e o t h e r ma l r e s e r v o i r . S in ce t h e r e s e r v o i r wil l t y pi c al ly b e

suff ic iently lar ge to supply m or e than one power p lant , only

a p ropo rtion al a mou nt of

this

c h a r g e

i s

ass igned to the

pro ject under considera t ion.

to the f ie ld development phase .

T h e s e c o s t s a r e i n c u r r e d p r i o r

b. Well Dril l in g Cos ts

The cap i ta l investments l i s t ed above a r e expected to r e tu rn

a



prof i t com mens ura te wi th the r i s ks invo lved in a geo the rm al

venture .

cash-f low method i s used to de te rmine the annua l r evenue re qu i r e -

ments .

To account fo r the t ime value of m oney, the discounted-

3 .

Expenses

Se ve ra l types of expens es a r e inc urr ed dur ing the opera t ion of

a

producing geo the rm al f i e ld . These fa l l in to two c las ses : cash

exp ense s and book expenses. The book expen ses a r e not deducted

f r om the revenues bu t a r e used in de te rmin ing the t axab le income

for fe dera l and s ta te income taxes .

a . Cash Expenses

(1) Royal ty Pay men t

Royal ty payme nts

a r e

typical ly

12.

57 0

of

t h e g r o s s

revenues .

(2) Opera t ing Expen ses

Annual opera t ing expenses include labo r , maintenance,

suppl ies , u t i l i t ies , e tc .

b. Book Exp ense s

3 )

Depletion Allowance



Thi s deduct ib le expense ,

s imi la r

to deprecia t ion, we

a s s u me t o be

2 2 %

of gr os s revenue.

been rule d appl icable to geot herm al in genera l .

However,

i t

has not

4. Taxes

Fe der a l , s t a te and loca l t axes wi l l be pa id by the p ro jec t .

f ede ra l and s ta te income taxes a r e pa id accord ing to the ne t

taxable income.

deduc ted f ro m the f ede ra l income tax .

tangible,

deprecia ble as se ts of the pro ject . The s ta te and loca l

re a l p rope r ty t axes a r e genera l ly charged accord ing to the va lue

of the r ea l proper ty .

revenues produced by that proper ty .

The

A f e d e r a l i n v e st me n t tax cred i t of ten perce nt i s

The c red i t i s based on the

This

i s

judged to be

a

func tion of the

T h u s, t h e s e t a x e s a r e us u al ly

a

percentag e of the gr os s revenues .

They a r e t r ea te d as an ad va lo re m tax of t e n pe rcen t in th i s s tudy .

5. Annual Cash Flow

The cas h flow i s the s a les revenues minus t axes and expenses not

including depreciation.

addit ion, this

i s

a l so sub t rac ted f ro m the cash flow.

flow i s then discounted

at

the des i red ra te of r e t u rn to

a

p r e s e n t

wor th

at

the beginning of power plant ope ratio ns. The annual

Since there i s a l so an annual cap i ta l

The cash

1.

Re tu rn on Inves tment



2.

3 .

4.

5.

C u r r e n t c ap i t al r e q u ir e me n t s a r e i n the range of 11 to

1 3

percen t .

Income Tax

The method used take s the expected annual taxes ove r the l i fe of

the power p lant inc luding provis ions f or in vestm ent tax cred i t and

in t e re s t deduc tions and conver t s them to a un i form annua l

"levelized" expense.

a 5 0 - 5 0 deb t /equ i ty ra t io .

A n i n t e r e s t r a t e of nine pe rcen t i s used with

DeDreciation

The deprecia t ion expense

i s

often ca lcula ted by the s t ra ight- l in e

method, but for economic ana lys is the s inking-fund method

i s

general ly used.

ca se use s the s inking-fund method (a t the ra te of re tu rn) .

The p r og ra m can use e i the r me thod , bu t the base

Ad Va l o r e m Tax

T h i s a c c o u n t s f o r t h e v a r i o u s p r o p e r t y a n d a d v a l o r e m t a x e s .

typical value

i s

2. 5% of ca pita l cost .

A

Admin is t ra t ive and G enera l Expense

This

i s

typical ly one pe rce nt of capi ta l cos t .

or de r to obta in good re la t iv e values but ma y not rep res en t bes t

absolute values.

These cas es a r e based on the fo llowing assumptions:



Pr oje ct l i fe 25

Explora t ion cost , K

$

800

Le ase bonus payment none

P r o d u c e r ' s

D C F

ra te of retu rn ,

70

15

Util i ty rat e of re tur n,

7 0

12

Depletion,

70

2 2

W rite -off of intangib le dr ill ing exp ens e,

70 7 0

Wr ite -off of dry- ho les exp ens e, 70 100

The pro du cer 's capi ta l c os ts and opera t ing and maintenance (O &M)

c o s t s ,

togethe r wi th the u t i l i ty 's capi ta l cos ts and

O&M

cos t s , were

taken fo r each case f rom Tab les 6 , 7, 9 and 11.

taken as the typical values repor te d in the preceding sect ion. The

resu l t s a re t abu la ted in Table 13.

Other input data we re

The Heber b inary case shows the lowest fuel cos t of the three Heber

cases (16 .

6 9

mil ls /k wh ) and the lowest power cost (35.

22

mi l l s / k wh ) .

T h e s e i n c r e a s e s a r e o f f s e t t o

a

l a rge ex ten t by the dec rease d b r ine

requirements of 1 . 19 M kg / h r ve rs us

3 .

1 M k g / h r ( 2 . 6 2 M l b s / h r

f



v e r s u s 6 . 9 M l b s / h r ) .

Raft River cos ts a re h igh in a l l counts , ref lec t ing the low tem per atu re

of the re se rv oi r as compared to the o the rs .

Ut il i ty f ixed ch arge s p lus O&M expenses vary f ro m a l i t t le ov er 18

mills

(Heber b ina ry ) to a l i t t l e over

20 mills

(Raf t R iver b ina ry ) .

var ia t ion is not nea r ly

as

grea t a s the va r ia t ion in fue l cos t fo r the

best cases , 16 . 0 mills to

3 2 .

8 mil ls .

This

F u e l c o s t e x p r e s s e d as cen ts /M Btu ex t rac ted is in the ra ng e of 6 0

cen ts /M Btu a t Heber , inc reas ing to about

80

cen ts /M Btu a t Val les

C a l d e r a , o r o v e r $ 1.OO/M Btu a t Raft Ri ve r.

We e l imina ted hybr id sy s tem s f r om fu r the r cons ide ra t ion s ince hybr id

cos t s wer e h igher than the o the r s .

al though the hybrid fuel c ost w as low at the th ree s i t e s ,

the power

plant w a s the m os t expensive . One reas on for the h igh c os t power

plant

is

tha t we have provided s epa ra t e turbine -gen era t or ins ta l la t ions

for both the s t eam -f l ash and binary sect ions of the p lant , If it we r e

poss ible to put both tur bine s and a single ge ner ato r on one shaft , the

capi ta l cos t would be reduced considera bly . This pros pect requ ire s

fu r th e r s tudy .

It should be noted in pass ing that ,

Raf t River cos ts a r e impo rtant as an indicat ion of cos t s whic hm ay be

expec ted in developing low - tem pera tu re res e rv o i r s .

It

is

c lea r tha t

Sensit ivity Analysis



W e have p rev ious ly s ta ted tha t the power cos t s p res en ted i n Tab le

13

a r e expec ted to g ive good re la t ive va lues be tween re se rv o i r s and

be tween p ro ces ses , bu t a r e no t necessa r i ly val id in abso lu te sense .

Accord ingly, we have ma de a stu dy of the effect of ch ange s in key

var iab les enter ing in to the economic model.

W e

have l imi ted these

com paris ons to the Heber b ina ry plant .

in Table 14.

These res u l t s a re t abu la ted

C a s e

2

as su m es that we have ov eres t ima ted f i e ld cap i ta l and

operat ing co sts by

20 .

16. 7 mil ls to 13. 5 mills and the power c o s t f r o m

35.

2 mil l s t o 32 .

0

m i l l s .

The effect

i s

t o r e d u c e t he f u e l c o s t f r o m

C a s e 3 assumes that we have underes t imated f ie ld

capital

and operating

cos t s by

20010,

in which case fuel cos t and power cost in cr ea se by

3 . 2

mil l s .

In ca se 4 , we as su m e that no wel ls wi l l be d r i l led dur ing the l i fe of

the project , there by reducing fuel cos t by 0. 8 mill

In cases 5 and 6 , we have var ie d the pr od uc er 's ra te of r e t ur n down

to 10% and up 200/0.

and the h igher ra te of r e t ur n in cr ea se s fuel cos t by 3 .5 m il l s .

T he l o we r r a t e o f r e t u r n r e d u c e s f u e l c o st 3 m i l l s ,

In case 7, the effect of el iminatin g both depletion and intangible wri te -

off i s to inc rea se fuel cos t by 4. 1 mi l l s .

F r o m t h e f o r eg o in g , it

i s

app aren t tha t the predic t io n of power cos ts

m ay va ry widely depend ing on the pa r t i c u la r se t of a ssumpt ions



ente ring into the calculation.

The anal yse s do not take in to account that only pre l im ina ry opt i-

mizat ion of the plant des ign ha s been made.

im por tant point , s inc e we did not have producing cos ts available

when the p re l im inar y op t imiza tion s tud ies w ere made ,

p re sen t judgment

i s

tha t the opt imum design wil l be in the

dire ctio n of hig her power plant c ost s and lower brin e consumption.

We think that the co st red uctions ass oc iat ed with optimizatio n of

the b inary cycle wi l l be g re at er than by opt imizat ion of the f lash

cycle.

Th is

i s

a pa r t i cu la r ly

Ou r

No

recogni t ion i s given to the economies which may resu l t f r om a

fu l l development of the r ese rvo i r .

expenses in pa r t i cu l a r wi l l be sp read over a wider base .

Overhead and maintenance

No a l lowance i s made fo r inc r ease d p lan t cap i ta l and opera t ing

c o s t s

which

m a y

be

i n c u r r e d

a t

t he

end

of

t he

p ro jec t

due

t o

t empera tu re dec l ine .

sav ings resu l t ing f ro m fu l l f i e ld deve lopment .

This fa c tor w i l l be offse t somewhat by the

We cannot hope to know a s much about a pro du ce r 's o r

a

ut i l i ty 's

b u s i n es s p r a c t i c e s a n d c o s ts a s t h e s e f i r m s do themselves .

Th eir m ethods of economic analys es may provide s ignif icant ly

d i f fe ren t number s

while the b inar y p r oc es s can a l te r i t s opera t ing condit ions to min im ize

the increa se . The e f fec t of decre as ing temp era tur e can be se en in the



com par iso n of the pro ce ss es a t Raft Riv er where the c os t of power by

t he f l a sh e d s t e a m p r o c e s s

i s

1 5

m i l l s o r

22

higher than the binary

p r o c e s s .

r ecomm end tha t t he b ina ry p r oce s s shou ld be in s t a l l ed a t t he H ebe r

si te .

On the ba si s of th is difference in the cost

of

power, we

F u e l Pr i ci n g S t r a t e m

A

cont ract fo r the sa le of fu el by a produce r to a uti l i ty i s l ike a

m a r r i a g e w h e r e d i vo r c e

i s

imposs ib le .

option of changing to a new se ll er o r a new buye r.

different busin ess object ives and philosophies .

to gove rnment act i ons of one kind o r another .

a ma jo r e f fec t on the i r respec t ive cos ts .

t h e p r o d u c e r ' s c o s t s a r e a f fe c te d i n a maj or way by government

regu lat ion s with res pe ct to deplet ion, wri te-off of in tangible dr i l l i ng

cos t s , f ede ra l and s t a t e income t ax r a t e s , p rope r ty t ax r a t e s and

income tax c red i t s . U t il ity cos ts a r e a f fec ted by

all

of the for ego ing

(except those re la t ing to deplet ion and intangible dr i l l in g co st s) , and

the i r inco me i s con t ro l led by the publ ic u t i l ity com miss ion .

a f fec ted in d i f fe ren t ways by many o ther agenc ies respons ib le fo r

enforc ing env i ronmenta l , sa fe ty and hea l th s tandards .

N e i the r pa r ty ha s the p rac t i c a l

E a c h p a r t y h a s

E a c h p a r t y

i s

subject

Thes e regu la t ions have

As

we have a l rea dy observed ,

B oth a r e

In our view the app roach to

a

contr act begins with a good-fai th

negotia t ion as to the s ta r t i ng fue l se l l ing pr ic e between the par t ie s ,

FIGURE 5



E S T I M A T E S U M M A R Y S H E E T

CUSTOMER

DATE

4/Z2/76

TOTAL

LOCATION Heber, Celifo:

ACCOUNT

ia

Materials

REV. NO.

0

Labor

ubcontract

I100

I200

1300

I400

IS00

I600

I700

I800

I900

2800

Columns (incl. trays)

Pressure Vessels

Heat Exchangers

F urnace/Heaters

Pumps

Boilers

Cooling Towers

Turbine

&

Generator

Tanks

Other

Labor

213,000

2,700,000

213,000

2,700,000

i ,132,000

1,132,000

1,800,000

155,000

200,00000,000

7 900 000

200,000

1,640,000

360,000

400,000

TOTAL MAJOR EQUIPMENT

3100 Concrete

3200 Pipe, Valves, Fit tings

3300 Structural Steel

3400 Instruments

3500 Painting

3600 Electrical

3700 Insulation

3800 Paving, Roads, Fences &

3900 Buildings

200,000

210,000

1 000 000

200,000

40, 000

9 900

7

000

410 000

2,700,000

600,

50,000

460,000

1,875,000

255 030

200,000

200,000

60,000

60 000

50,

ooo

650,000

255

,

00

80 000

200 000

1,225,000

.sc .

20,000

100 000

FIGURE 6



E S T I M A T E S U M M A R Y S H E . E T

CUSTOMER

LOCATION

Heber,

Cal i f (

ACCOUNT

I100 Columns (incl. trays)

I200 Pressure Vessels

1300 Heat Exchangers

1400 Furnace/Heaters

1500

Pumps

1600 Boilers

1700 Cooling Towers

1800

Turbine

&

Generator

I900

Tanks

2800 Other

-

Vacuum

Equip

and

etc.

Labor


3100 Concrete

3200 Pipe, Valves, Fit tings


3400 Instruments

3500 Painting

3600 E:ectrical

3700

Insulation

3800 Paving, Roads, Fences

&

3900 Buildings

i a

Materials

283,000

1,280,000

451,000

6

80,000

406

, 00

9 30°

J

Oo0

200,000

750

,

00

200,000

300

, oo

sc .

10,000

subcontract

1,600,000

200,000

1, aoo, ooo

10,000

100 000

50,

00

425,000

200,000

100, 00

200,000

XEV.NO. 0

Labor

400,000

400

,

350,000

400,000

100,000

30

, 00

90,000

D A T E 4 22 76

TOTAL

283,000

1,280,000

451,000

1,600,000

7 080 000

406,000

400,000

11, 500,000

550,000

1,160,000

300,

b30 ooo

50,

coo

1,375,000

200,000

200,000

200,000

F I G U R E 7



L O C A T ~ O N

Heber, California

ACCOUNT

I100 Columns (incl. trays)

1300 Heat Exchangers

1400 Furnace/Heaters

IS00 Pumps

1600 Boilers

1800 Turbines

&

Generators

1900 Tanks

2800 Other - Vacuum

Equip.

1200 Pressure Ve ssels

1700

Cooling Towers

and etc.

Labor


3100 Concrete

3200

Pipe. Valves, Fittings


3400 Instruments

3500 Painting

3600

Electrical

3800 Paving, Roads, Fences

8c

3700 Insulation

3900

Buildings


Materials Subcontract

272,000

2,i15,000

1,135

,

00

1,600,000

5,OOO,OOO

498,000 50,000

9,020,000 1,650,000

200 000

2,160,000 59, 00

562,000

425,000

171,000

50,000

1,317,000 701,000

h ’ i SC . 300,

oo

3332

00

324,000

REV.NO. 0

Labor

271,000

271,000

440,000

2,206,000

354,000

41,000

-==qOTAL

272,000

2,115,000

1

35

000

1,600,000

5,000,000

548,000

271,000

10,941,000

640

00

4,425, 00

916,000

637,000

50,

00

2,018,000

333,000

300,000

324,000

FIGURE 8




I O 8

NO. 7523

CUSTOMER EPR1

' LANT

REV.NO. n DATE

4/22/76

Productior. L I n j e c t i o n

LOCATION Heber , Ca l i fo

ACCOUNT

ia

Materials

Labor

TO TAL

ubcontract

I100

I 200

1300

1400

I500

1600

I700

I800

I900

2 8 0 0

Columns ( inc l . t rays)

Pressure Vessels

Heat Exchangers

Furnace/Heaters

Pumps

Bo i le rs

Cool ing Towers

Compressors

Tanks

Other

Labor

70,000

1,411,000

70 000

1,411,000

1,000

1 000

53 000

3 000

1,482,000

13,000

884,000

1,535,000

51,000

1,581,000

53 000

18,000

677,000

T O T A L M A JO R E Q U I P M E NT

3 100 Concrete

3200 Pipe, Valves, F i t t i ngs

3300 Structu ral Steel

3400 Instruments

3500 Paint ing

3600 E lec t r i ca l

3700

I nsu la t i on

3800

Pav ing, Roads , Fen ces&

3900 Bui ld ings

20,000

149,000

440,000

10,000

217,000

281,000

455, 00

5,000

630,000

10 000

217,000

190,000

sc:.



TABLE 6

ESTIMATED POWER PLANT AND TRANSMISSION CAPITAL COSTS

(AL L FIGURES IN

$

K)

HEBER

BINARY

FLASHED STEAM

HYBRID

VALLES CALDERA

BINARY

PLANT

2 8 , 5 0 0

2 6 , 8 0 0

3 6 , 6 0 0

2 6 , 5 0 0

TRANSMISSION

5 0 0

500

5 0 0

1 , 9 0 0

I T E M

T ABL E

7

E S T I M AT E D I NI T I AL F I E L D CAP I T AL COS T S

ALL COSTS IN K

HE BE R VAL L E S CAL DE RA

R A F T R I V E R

BINARY FLASH HYBRID BINARY FLASH HYBRID BINARY F LASH HYBRID



P RODUCING WE L L S

No. o f Wel l s Co s t / W el l

C o s t

I NJE CT I ON WE L L S

No . o f Wel l s Co s t / We l l

C o s t

DRY HOL E S

No. o f Wel l s Co s t I W el l

C o s t

W E L L C O ST

T O T A L F I E L D C O ST 11 800 14 350 12.200

1.

I n c l u d es d o wh -h o l e p u m p s a t Heb er an d Raf t R i v er

TABLE 8



POSITION

FIEL D OPERATORS

ESTIMATED FIEL D STA FF COST

(ALL FIELDS)

R.OUS TA BOU T

E L E

C TR.IC-N

INSTRUMENT SPECIA LIST

MECHANIC

FOREMAN

OF FIC E MANAGER

NO. O F RATE RATE

HIRES $/MONTH

$/MONTH

4

1 ,000 4,000

1 1,000 1,000

2 1 ,200 2,400

1 1,500

1,500

1

1,000 1 ,000

T A B L E 9

ESTIMATED F IEL D OPERATI NG AND MAINTENANCE COSTS

(A LL FI GUR ES IN YEAR)



I T E M

HE B E R VAL L E S C ALDE RA R AF T R IVER

BINARY FLASH HYBRID

FLASH HYBRID

INARY FLAS H HYBRID BINARY

FIE L D L ABOR

(INCLUDING OVERHEAD G A)

2 5 3 2 5 3 2 5 3 2 5 3 2 5 3 2 5 3 2 5 3 2 5 3 2 5 3

PRODUCING WELL MAINTENANCE 3 6 8 4 9 1 3 9 8 3 3 7 42 8 3 68 5 2 1 7 6 7 6 7 5

INJ E C T ION W E L L M AINT E NANC E

3

93

5 2 4 3 9 3

SURFACE INSTALLATION MAINTENANCE

2 3 6 2 5 6 2 4 0

DOWN HOLE S URVEYS 1 8 24 1 9

M ISC E LL ANE OUS SUPPL IE S

4 0 5 3 4 5

PURCHASED POWER 6 6 5 8 8 5 7 0 2

T OT AL S

1 973 2 . 4 8 6 2 , 0 5 0

TABLE 10



POSITION

ESTIMATED POWER PLANT LABOR COST

OPERATORS

LABORER

ELECTRICIAN

INSTRUMENT SPECIALIST

MECHANIC

OFFICE MANAGER

SUPERINTENDENT

NO. O F RATE RATE

HIRES $/MONTH $/MONTH

9 1,000 9 , 0 0 0

1 750 750

2

1

1

1 ,200

1,000

2,000

2,400

1 ,000

2,000



T A B L E

12



INPUT URTR

T A B L E 1 2 ( C o n t i n u e d )



PA Y OUT E 1 Y E A P I :

TABLE 13

ESTIM ATED GEOTH ERMAL POWER COST BASE CASES

B r ine Fue l Cos t Power Cos t (mi l s lkwh)



Rate

d

pe r pe r F ixed Operat ing

C a s e

Heber

K / h r

K

Br ine M Btu Fue l Charges Main tenance T ransm is s ion To ta l

B inary


Hybrid

n Val les Caldera

Binary


Hybr id

Raf t R iver

B inary


Hybr id

TABLE 14

SENSITIVITY ANALYSIS - GEOTHERMAL POWER COST

BASIS: HE BE R BINARY



Conditions

Power Cos t

-

m i l s l k w h

Fixed Operat ing

F u e l

Charg es Main tenance T ra nsm iss io n To ta l

Ba se Case includes deplet ion 16. 7 15 . 0 3 . 2

and intangibles wr i t e -of f )

Lower Field Capi tal and

13 . 5

15.

0 3 . 2

Overhead Maintenance -

207 0

Higher Fie ld Capi tal and 19 . 9 15 . 0 3 . 2

Overhead Maintenance - 207 0

Fiel d Decl ine - 070

15.

9 15 . 0

3 . 2

Fiel d Rate of Re turn - 1070 13. 7 15. 0

3 . 2

Fiel d Rate of Retu rn -

2070

2 0 . 2 1 5. 0 3 . 2 0 . 3 3 8. 7

No Deple tion Intangib les

20.8 15. 0 3 . 2

Depletion Only

17. 6

15 .

0 3 . 2

Intangibles Only

19. 9 15 . 0 3 . 2

Pro je c t L i fe

- 2 0

Y e a r s

17. 1

15.

2

3 . 2 0 . 3 35 . 8

Pro jec t L i f e

- 3 0

Y e a r s

1 6 . 5 15 . 0 3 . 2 0 . 3 35 . 0

Powe r Plant Rate of Retu rn - 1070

16 . 7 12 . 3 . 2

Powe r Plant Rate of Return - 147 0 16 . 7 17. 6 3.2

IDENTIFICATION OF TECHNOLOGY WEAKNESSES



The re app ear to be no se r io us t echnology weaknesses a ssoc ia ted wi th

the design of st ea m- fla sh cycles.

opera t ion for a num ber of y ea rs i n New Zealand, Japan and Mexico.

Es tab l i shed steam tu rb ine manufac tu re r s o f fe r

two

tage, double-entry

s te am tu rb ines on a guaran teed pe r fo rm ance bas i s . Cor ros io n and

eros ion have been a pro blem but not a se r io us h indrance .

Such plants have been in succ essf ul

No bina ry cycle p lants have be en bui lt in

this

country. The Rus sian s

a r e r e p o r t e d t o ha v e

a

small plan t in geo the rmal se rv ice , and the

Japane se have

a

3 .8 MWe p lan t r ecover ing energy f ro m was te hea t

and employ ing Fre on a s

a

working fluid.

soon be in opera t ion in the Im pe r ia l Valley .

nominal 10 MWe isobu tane te s t loop but no expansion turbine.

the except ion of the expansion turbine , the m ajo r equipment

i s

avai lable

l ines .

The Niland te s t fac i l i ty wi l l

This plant contains a

With

. f r o m e s t ab l i sh e d ma n u f a c t u r e r s

as a

p a r t of the i r s t andard p roduc t

HYDROCARBON TU RBINES

Both axial and rad ia l tu rb ines have been p roposed fo r th i s p ro jec t .

Bo th types of tu rb ines have been used in indus t ry fo r m any yea rs and

a r e consider ed to be safe and re l iable . However , ne i ther type of

The Radia l Turbine

The Rotoflow Co rpo ratio n ha s pro pos ed to supply a 6 5 MWe turbine



ins ta l la t ion mad e up

of

th ree rad ia l tu rb ine e lements .

would c on si st of a single-flow turbine in one casing and a dual-flow

turbine in a second cas ing, all mounted on a single shaft .

The assem bly

Rotoflow i s exper ien ced in the des ign of radia l turbines in hydrocarbon

s e r v i c e .

capa ble of deli veri ng 7 MWe of e le ct ri c powe r.

would cons ist of th re e turb ine wheels

e a c h r a t e d a t 22 MWe. Thu s, the

scale -up of the turbine e lemen t

i s

about 3 /1 . This degr ee of sca l e-up

does not app ear to rep re se nt a ma jor change in turbine des ign. How-

e v e r , it does re pr es en t an extension of the pr es en t s ta t e of the a r t and

wil l require fur ther engineer ing development .

The la rg es t unit they have bui lt i s a single-flow turb ine

The proposed unit

An independent design effort by qualif ied consultants, comp aring the

two types of tu rbin es and evaluat ing f inal prop osal s , app ear s to be

justif ied.

Speed Control

Al l the tu rb ines p roposed by vendors a r e des igned to opera te a t 3600

rpm and wil l not need a speed -reducing gear . The turbi nes wi l l be

brought up to speed before the ge nera tor i s connected to the e lec t r i ca l

t r a n s m i s s i o n s y st em .

After it i s connected, i t wil l cont inue to ro ta te

at rpm,

the s tea m tu rb ine con t ro l sys tem to a hydrocarbon tu rb ine may be

encountered. While th is pro blem i s not in our judgment a s e r i o u s

con stra int , a study by qualif ied consulta nts ma y be justif ied.



DOWN-HOLE

P U MP S

The pumps

so

f a r u s e d t o p r o d uc e g e o t h e r ma l fl ui d f r o m i n t e r me d i a t e

tem pera tu re we l l s a r e modi fied deep-well pumps which cons i s t of a n

e l e c t r i c mo t o r d r i v e l o c a te d

at

the w el l head,

a

long shaft s tabil ized

by bear in gs loca ted a long its length, and

a

mult i -s tage centr i fugal

pump located

at

the ba se of the shaft. Th is type of pum p ha s been

used success ful ly in Ice land in supplying hot wate r to the Ci ty of

Reykjavik.

f i l t e red wa te r f ro m the su r face down the bea r ing tub ing , the reby p ro -

tec t ing the bea r ing s f ro m contact wi th the wel l fluid.

m ate r ia l s a r e ava ilab le fo r f ab r ica t ion of the bowls, imp e l le r s and

pump bear ings .

Heber us ing the same type of pump and solved more o r l e s s successful ly .

Shaf t -bear ing wear ha s been minim ized by pumping

Suitable

Various d i f f icul t ies w er e exper ien ced by Chevron a t

We regard this type of pump as the on ly s ta te -o f - the -a r t pump

avai lable but recognize that succ essf ul low maintenance opera t ion may

not be rea l i z ed fo r som e time .

Othe r pumps have b een proposed w hich would e l iminate the shaft

lubr ica t ion problem.

follows:

T h e d i f f er e n t t e c h ni c a l a p p r oa c h e s a r e a s

. .

-

. . .

-

. . .

.

. . .

. .. .

.

-. . .

.

SCALE

DEPOSITION

The deposit ion of sca le on hea t exchanger tube s occ ur s when geo-

the rm al f lu ids a r e coo led to the i r sa tu ra t ion point .

A

se r i es of te s ts



we re pe r fo rmed a t the Heber re se r vo i r in 1976 to mea sur e the ef fec t

of s cal e deposit ion on heat exchanger perfo rma nce. The res ul ts of

the se te s t s indicated that sca le deposi t ion does occu r on the tubes .

The amount of sca le fo rmed dur ing the t e s t s was sma l l , bu t it was

suffi cient to show that the ra te of format ion inc rea sed a s the

tem per atu re of the br in e was reduced.

the longe st one was 22 days , and the da ta f r om th i s r e la t ive ly shor t -

range t e s t was ex t rapo la ted to p red ic t pe r fo rmance over a ye a r .

Fu r th e r ex tended dura t ion hea t exchanger t e s t s appear jus t if i ed to

est abl ish the ra te of deposit ion of sca le

as

a function of t e mp e r a t u r e

and t ime.

The te s t s var ied in length , but

CORROSION

Eac h of the geoth erm al f lu ids d i f fer f r om one another in sa l in i ty , pH

and concentration of anions and cations. Eve n different we lls in the

sam e re se rv o i r can p roduce f lu ids with d i ffe ren t chemica l p roper t i e s .

The cor ros ive chara c te r i s t i c s of each rese r vo i r should be es tab l i shed

before the f inal materia ls se lec t ion fo r the p lant take s p lace .

should be conducted for

a

sufficient leng th of t im e to identify

if

oxi-

dat ion, s t re s s corros ion, o r p it t ing could be expected in the p lant.

Different m at er ia ls should be te s te d to es tab l ish what degre e of

cor ros ion protect ion would be needed. Corr os io n work could mo st

T e s t s

SELECTION O F

THE

RESERVOIR



The se le c t ion of H eber o r Val les C alde ra fo r the s i te of the demon-

s t ra t ion p lan t

i s

base d on the ra t ing of approp r ia te cr i t er ia

as

s e t f o r t h

in Table 15, which su m m ar iz es the f indings developed dur ing the

cou rse of this study.

bi l i ty of re se rv oi r development and the socioeconomic imp act of

geo the rm al deve lopment in the Im per i a l Val ley. P ro con has m ade

a

pre l imi nary env i ronmenta l a ss ess m en t of Heber and Va l les Ca ld e ra

(with se i sm ic , subsidence and geological input by Geonomics). Holt in

this re po r t has developed the technical feas ib i l i ty of the convers ion

op tions and , wi th ass i s tanc e f ro m Proco n in cap i tal cos t e s t ima t ing ,

has ma de a n economic analys is of the conve rs ion opt ions of each s i te .

Geonomics has repor ted on the t echn ica l f eas i -

Table

15

s e t s f o r t h te n c r i t e r i a f o r r e s e r v o i r s e l e ct i o n a nd th e n r a t e s

each c r i t e r i a ( somewhat sub jec tive ly ) on

a

sc al e of 10 to

0.

r e s e r v o i r

r a t e s

ve ry we l l on al l c r i t e r i a

f o r

a n over a l l ra t ing of 92.

Va l le s C a l d e r a ' s o v e r a l l r a t in g

i s

63.

The Heber

One ma j o r p r o b l e m at Val les Ca lde ra

is

that t h e r e

i s

l i t t l e h a r d d a t a

avai lable on which to base a r e s e r v o i r e va lu at io n o r t o ma k e t e c h ni c a l

and econom ic evalu ations (rat i ng of 2). Cooling wa ter avai labi l i ty i s a

s e r i o u s c o n s t r a i n t

at

Val les Ca lde ra and ra te s a

2.

Val les Ca lde ra

d o e s not ma t c h th e r e p r e s e n t a t i v e r e s e r v o i r as we l l a s He b e r a n d

ra te s 4 in th i s ca tegory . Well p roduct iv ity i s low and we l l cos t

i s

CRITERIA

R e s e r vo i r s hou ld s uppor t 200 MWe fo r 30 ye a rs .

T AB L E 15

CRITERIA FOR RESERVOIR SELECTION

HE B E R

COMMENTS RATING

R e s e r v o i r m o r e t h a n a d e qu a t e .

VALLES CALDERA

C OM M E NT S

R e s e rv o i r p roba b ly mor e tha n a de qua te .

R AT ING

10



R e l l a b l e d at a s h o u l d b e a v a ~ l a b l e o define s ize

a n d c h a r a c t e r i s t i c s of r e s e r v o i r .

R e s e r v o i r c h a r a c t e r i s t i c s , s h o u l d b e c l o s e t o

r e p r e s e n t at i v e r e s e r v o i r .

We l l s s hou ld be p roduc t ive , a nd s uc c e s s fu l

re in je c t ion s hou ld ha ve be e n p ra c t i c e d .

B r ine s hou ld be nonc or ros ive a nd nons ca l lng ,

o r

well demons tra t ed metho ds of combatt i ng both

should be available

T he r e s hou ld be a de ma nd fo r e l e c t r i c power

wi th in a re a s ona b le d i s t a nc e .

The co s t of power should be compet i t ive with

a l t e rna te s ou rc e s o f ne w powe r

T he re s hou ld be a n a s s u r e d s upp ly o f c oo l lng

wa te r a va i l a b le .

T he r e s hou ld be no overriding environmental

c ons t ra in t s .

T he re s hou ld be no ove r r id ing s oc ioe c onon~ ic

c ons t ra in t s .

G oo d da t a a r e a v a ~ l a b l e .

He be r i s good ma tc h . I t i s l ow

s a l in i ty 15 ,000 ppm) a nd me d iu m

t e m p e r a t u r e 1 8 2 C 360 F .

He be r i s OK on bo th c oun t s .

Good da ta a va i l a b le on bo th c oun t s .

B r ine i s re l a t ive ly be n lgn

50 MWe can supply loc al needs .

F u l l f i e l d d e v e l o p m en t r e q u l r e s

ne w t ra ns mis s i on l ine to Sa n

Diego.

A p p e a r s t o b e competitive.

O K o n s h o r t t e r m . P r o b l e m s ,

p roba b ly s u rmoun ta b le , on long

t e r m .

M i n i ma l p r ob l e m s a s s o c i a te d w ~ t h

a l r qua l i ty , wa te r qua l i ty ,

s u b s i d e n ce a n d s e i s m i c e f f e c t s .

M i n i m a l i m p a c t a f t e r c o n s tr u c t io n .

W i ll i n c r e a s e e m p l o y m e n t a n d

Improve t a x ba s e .

Ve ry l i t t l e da ta a va i l a b le .

Va l l e s C a lde ra I S fa l r match. It 1s low

s a l lmty 5, 000 ppm) bu t fa i r ly h igh

te mpe ra tu r e 260 C 500

F .

We l l p roduc t iv i ty p roba b ly low; re in je c t io n

ha s be e n c a r r i e d ou t bu t no da ta a va il a b le .

No ha r d da ta a va i l a b le . I f c o r ro s ion a nd

s c a l e a r e p r o b l e m s , m e t h o d s a r e a v a i l ab l e

to c omba t the m.

N e w M e x ~ c o u b l i c S e r v i c e c a n t a k e o u t pu t ,

b u t n e e d i s l e s s t h a n a t H e b e r .

No t qu i t e s o c ompe t i t ive .

Proba b ly no t a va i l a b le e xc e p t a t h igh c os t .

M i n i m a l p r o b l e m s e x c e p t f o r p o w e r

c o r r i d o r s .

M in lma l impa c t a f t e r c ons t ruc t ion wi l l

i n c r e a s e e m p l o y m e n t a n d I m p r o v e t a x

ba s e .

2

8

TOTALS



RE COMMENDATION

On the s tre ng th of this study, the Heber geo therm al field in Californ ia

i s recommended a s the bes t s i te

f o r

a low-salinity hy drotherm al

dem onstrat ion plant .

If

a dem onstration plant is' con struc ted, the

power co nversion sy stem should be based on the binary cy cle, and the

capacity of the plant should be in the 50 MWe range.



A P P E N D I X

TEMPER TURE ENTH LPY DI GR M

TWO PH SE ENVELOPES OF TY PI C L BIN RY CYCLE F LU ID S

PROP NE ISOBUT NE



TEMPERATURE ENTHALPY DIA GRAM

TWO P H A SE E N V E LO P ES O F T Y P I C A L B I N A R Y C Y C L E F L U I D S

ISOBUTANE ISOPENTANE



- . . . .

.

\ / 80 IS O B UTA NE 2 0 IS O P E NTA NE / 41.

geothermal convertion and economic

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