direct uses of geothermal resourses

7/28/2019 Direct Uses of Geothermal Resourses

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DIRECT USE OF GEOTHERMAL RESOURCES

John W . Lund

Geo-Heat CenterOregon I nsti tute of Technology

Klamath Falls, OR 97601

ABSTRACT

Geothermal energy was used by early man pri-marily for direct heat such as cooking,

and balneology. Today i t i s used for spaceconditioning, industrial processing and agri-business applications. District heat has receivedrecent interest especially i n the US. A t present,over 2,000 are util ized i n the world for directuse applications. Generally, conventional equip-ment i s used to extract the heat from geothermalfl ui ds,wi th materi sel ection ng dictated bythe water and gas chemistry. Heat exchangers andpiping have been adapted to geothermal use, alongw i t h water-to-water heat pumps. Cascading of thewater can increase the utilization efficiency asillustrated i n Japan and the USSR.

I NTRO ON

Early man probably used geothermal water thatoccurred i n natural pools and hot springs forcooking, bathing and to keep warm. We are alsoaware that the Indians of the Americas used these

pools and springs to rest and recuperate from thewounds o f battle. Recorded history shows uses byRomans,J apanese,T urks, anders,Central Europ-eans and the Maori of New Zealand for bathing,cooking and space heating. Baths i n the RomanEmpire, the middle kingdom of the Chinese, and the

Turkish baths of the Ottomans were some of theearly uses of balneology--where body health, hygieneand discussions were the social custom o fthe day.

This custom has been extended to geothermal spasi n J apan, Czechoslovakia and New Zealand, which areworld famous.

One of the older therapeutic uses of eothermalwater i s at the Ziaotangshan Sani-torium northwest of Beij i ng (Peking),China. Here

the water has been used for over 500 years (si ncethe Ming dynasty) for medical purposes and forspace heating 29,000 (312,000 Two hotsprings, 48C and 53C (118F and and 3wells provide water for bathing, showering, spray-ing and space heating, saving 800 tons of coalannual ly. Speci f ic medical problems treated arehigh blood pressure, rheumatism, s k i n diseases,diseases of the nervous system, ulcers and recup-eration af ter surgery (Lund, 1980 and Cai, 1981).

These uses throughout the world have continued tothis day; for example, over 2,200 hot spring re-sorts exist i n J apan, vi sited by 100 mil lion guestsevery year; residents and vi si tors to Rotorua, NewZealand, visit the hot tubs and pools every evening

to relax before a good night's rest; about 30 swim-ming pools i n Iceland use natural hot water, w i t ha total capacity of about 20,300 (5.4 mil li ongal lons) ; and the 200 bed Queen Elizabeth Hospitali n Rotorua uses geothermal water for the treatmentof rheumatic diseases.

District heating began i n I celand i n 1930 whenthe Reykjavik di stri ct heating system was put intooperation on a small scale. Over 80C (176F) hotwater from wells w i t h i n the ci ty was piped into ahospital , swimming hall , two school buil dings, and70 homes i n the vi ci ni ty of the hal l . I n1943 a major expansion of the Reykajavik di stri ctheating system was completed when the system wasextended to the majority of the ci ty, serving apopulation of approximately 30,000.at that time piped i n from the Reykir geothermalarea, about 16 km (9.9 miles) to the northeast ofthe city. In 1959 a modern rotary dri l l ing r i g waspurchased to help expand the system. Today thi ssystem suppl ies heat to over 115,000 people wi th acapacity of approximately 475 (Karlsson, 1381).

The water was

Early industrial appli cations include the useof the natural manifestation of steam, pools andmineral deposits i n the Larderell o region of I taly.Serious industrial activi ty began only thediscovery of boric acid i n the hot pools in 1777.

The f i rst attempt at using these minerals was madei n 1810.

in 1846, was near the ancient castle ofi .

factories were built i n the region. I nitiall y,the boric acid was extracted from the geothermalfluids by boiling and subsequent crystallizationusing wood from the neighboring forests as fuel.In 1828, dri l l i ng brought additi onal f luid to thesurface and from 1827 onward, natural thermal en-ergy was used for fuel instead o f wood. A t this

time, steam-collection devices or covered pools(1agone coperto) increased the ef f i ci ency of the

boric industry. A flouri shing chemical industrywas thus in operation by the early 1900's. Thisindustry was curtai led during the Second World War,and today i t depends upon imported raw material,but sti l l uses geothermal energy for the process.

The use of the local f luid for i t s boric contenti s no l onger economical, as el ectri c power gener-ation i s more profitable ( E N E L , 1976).

The first factory, bu i l t by Francesco

Between 1818 and 1835 ei gh t addition-

PRESENT USE

Geothermal di rect use has evolved from thesimple bathing and theraputic use to the more


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LUN

sophisticated space conditioning and industrialprocess appl cations. Today these appl i cationsrepresent a worldwide ut i 1izati on of about 2,000megawatts thermal which are summarized i n

Table 1 below (Lund, 1979; Peterson, et al , 1979;Gudmundsson, et al , 1981; and Lienau, 1982).ct heating i s receiving the greatest emphasis:

wi th many new projects either i n the planning stageor under construction. T h i s i s especially true i nthe US where approximately 40 projects are underconsideration (Fornes, 1981). Space cooling i sanother popular appl i cati on wi th several projectsusing lithium bromide absorption now i n operationand one using ammonia - water under constructioni n India.

TABLE 1

Worldwide Direct Use of Geothermal Energy

Space

Heating/ Agriculture/ IndustrialCool i ng Aquaculture ProcessesCountry

France 25.2Hungary 34.6 316.9 14.5

and 580.0 34.2 13.6

China 38.4 112.9

Italy 49.0 3.5 20.0Japan 23.0 21.2New Zealand 2.0 2 150.0USA 40.4 55.9USSR 300.0 55.0Others 44.0 10.0 5

1,136.6 498.7 313.6

Heat exchangers are also becoming more ef-f i ci ent and better adapted to geothermal use, al-lowing the use of lower-temperature water and highlysaline f luids. Heat pumps uti l i zi ng low temperaturef l uids , are extending geothermal development intotraditionally non-geothermal areas such as Franceand A ustria, as well as many areas i n the US.unique appli cation of the heat pumps i s the EphrataGeothermal Energy Project i n Washington that wi l luse energy from the ci ty 's domestic water supplywhich i s geothermally heated. The system wi l l bethe f i rst US application of heat pumps to municipalwater mains for space heating.of the project, a large central heat exchanger willextract approximately 6C (10F) from (600gpm) of 29C (84F) geothermal water i n the ci tymain. The energy wil l be used to heat the Grant

County Courthouse during the winter and cool i tduring the summer.

A

In the f i rst phase

Agri ture-related uses of geothermal energygenerally requi re the lowest temperatures, wi thvalues from 25C to 80C (77F to 176F) beingtypi cal . The amount and types of chemicals anddissolved gases, such as boron and arsenic, are amajor problem for plants and animals. Heat ex-changers and proper venting of gases may be neces-sary in come cases to solve thi s problem.sive agri ated energy u t i 1ization occursi n Hungary and the Soviet Union.requires temperatures in the range of 65C to 100C(149F to wi th 40C being used i n

Space heating

some marginal cases and heat pumps extending thisrange down tothermal energy for space heating is Iceland whereover 75%of population enjoys geothermal heat

i n thei r homes. There are now about 50 geothermaldi stri ct heating systems operating i n towns, vi 11agesand smal l er communiti es. Geothermal cool ing exam-ples are limited, w i t h the I nternational Hotel i nRotorua, New Zealand, and the Oregon I nsti tute of

Technology Campus being the prime examples.tr i al processing typi call y requires the highesttemperature, using both steam and high temperaturewater. Temperatures above (302F) are oftendesi red; however, lower temperatures can be usedi n some cases, especiall y for drying of variousagri tural products. Though there are relativelyfew examples of industrial processing use of geo-thermal energy, they represent a wide range of ap-plications from drying of wool, fish, earth, timberand vegetables to pulp and paper processing, andchemical extraction. The two largest industrialusers are the diatomaceous earth drying plant i nIceland and the paper and wood processing plant i nNew Zealand.hydration plant at Brady Hot Springs, Nevada; theethanol plants at Wabuska, Nevada and Hot Lake,Oregon;and mi 1k pasteurization at amath 1 ,Oregon.

The leading user of geo-

Indus-

Notable US examples are the onion de-

UT I L IZATION EQUIPMENT

Generally, conventi onal equi pment directl yoff-the-shelf or slightly modified i s used i ndirect-use projects to extract the heat from thegeothermal water.proper allowances must be made for corrosion andscaling caused by the unique chemistry of the water.

Since unmixed geothermal water has l i tt l e or nodissolved oxygen, care must be taken to prevent theaddition of oxygen to the system, especially i n thepresence of certai n metals. Dissolved gases suchas ammonia and hydrogen sul f ide can also cause cor-rosion problems. The isol ation of the geothermalwater from the system by a heat exchanger may beal l that i s necessary to solve the problem.clean secondary f luid i s then circulated through theuser side of the system.

In the case of geothermal water,

A

Figures 1 and 2 i l l ustrate the primary compon-ents of any di rect-use geothermal system. In thef i rst case, the geothermal water i s benign enoughto use di rectly i n the heat recovery system, andin the second a heat exchanger i s used. In bothsystems the common components are pi pel ines, ci r-cul ation pumps, peaking or backup systems and usersystems. Disposal i s either surface or subsurface(reinjection). A peaking system may be necessaryor economical ( i n the case of large systems) tomeet peak demands by increasi ng the temperature orproviding storage, resulting i n a decrease i n thenumber of 1 required.systems where the geothermal f l ui d i s below about

a heat pump would be considered.

In low-temperature

*An additional 335 are used i n Wyoming forenhanced oi 1 recovery.


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Use System Without Heat

FIGURE 2

Direct Use System With Heat Exchanger

Heat Exchangers. Geothermal systems have used sev-eral types o f heat exchangers success fully. Themain types include shell-and-tube (water-to-water),pl ate and downhole. Other less common types aredir ec t contact, fluidized-bed and pl as tic tube(Lienau, e t a l, i n Anderson and Lund, 1979).

The l-and-tube and plate heat exchangersare placed above ground either a t the well head orat a central location.c ons is t o f tubes i ns ide a c yl in dr ic al she ll

with primary fluid (geothermal ) flowing inside thetubes.se ries o f s teel plates (commonly stainl ess) withgaskets he ld i n a rack by rods, allowing the p ri -mary and secondary fluid to counterflow across theplates. The gasket material w i l l l i m i t the maximumtemperature tha t can be used. The plate heat ex-changer has an advantage i n that it i s more effic-ie nt, requires smaller space, and i s more accessible

The shell-and-tube types

The pl ate heat exchanger cons ists o f a

D

to 3 mi l l i on (3 mi l l ion from a s inglewel l using three downhole heat exchangers (PonderosaSchool i n Klamath F alls , Oregon). They are generallynot e ff ec tive wi th wel l temperatures below 60C(140F).

hole heat exchangers requi res spec i 1 completiontechniques to produce a verti cal convection ce ll o fheat i n the well. I n addition, it may be necessaryto provide electrical isolation to the pipes at thesurface to reduce downhole electrolysis problems.Downhol e heat exchangers have been used successfullyi n K lamath F al ls , Oregon and Reno, Nevada and areunder tes tin g i n New Zealand (Culver, e t al , 1978;A l l i s , 1981, Shannon, 1982; and Pan, e t al , 1982th i s volume).

It should be noted that the use o f down-

Piping.used i n geothermal transmission l ines . Carbonstee l i s the most widely used meta ll ic pipe.o f al lo y pipe i s li mite d due t o cost, and copperand aluminum piping are affected by dissolved gases

such as hydrogen su l fide and ammonia. The non-metal li c pipes are i ne rt t o the normal chemical con-s t i tuents i n geothermal fl ui ds ; however, temperaturemay l i m i t the use o f these materia ls . The temper-ature li mitati ons are shown i n F igure 3 (Ryan, 1981).

Both metallic and nonmetallic piping are

Use

WLYETUYLENE

NORMAL

ASB ESTOS

FIBERGLASS

REINFORCED

STEEL

FIGURE 3 Maximum Temperatures-Piping Materials

I n general, the higher the temperature l i m i t -atio n the more expensive the pi ping material. Onthe other hand, the nonmetall ic pipes, having tem-perature re stric tion, are l ig hte r and thus easierto handle and in s tal l. J oining the individual

sections of the nonmetallic pipi ng i s als o eas ieras they can be welded with so lvents o r heat fused.

Temperature approaches (d if fe rence betweenprimary and outgoing secondary fl ui d) o f 3C (5F)are e as il y obtained, as compared to about 11(20F) f o r the conventional shell-and-tube. Theplate heat exchanger i s about 60% of the cost ofthe shell-and-tube when compared a t the same sur-

face area (Ryan, 1981). Both types o f heat exchan-gers would require disposal o f the geothermal f l u i daf ter it has passed through the primary side.

The downhole heat exchanger avoids the problemo f disposal o f the geothermal fl ui d s ince only heati s ''pumped" from the well. It has the disadvantageo f extr ac ting less heat than the other types; how-ever, i ni t i a l costs are less. From 30 to 90 m(100-300 fe et) o f5 cm (2 inch) diameter pipe belowthe water surface i s needed to heat an average re-sidence. A rough r ul e o f thumb i s to use 0.3 m(1 fo ot) o f double pipe below the water surface fo reach 1,500 to 2,000 (1,500 - 2,000peak heating load. In sta lla tions have produced up

i c piping requires expansion provisions,ei the r by a bellows arrangement o r by loops. Atypical meta l l i c p iping insta l la tion havefi xed points and expansion po ints about every 100meters (300 feet). I n addition, the piping wouldhave to be placed on r ol le rs o r s l i p plates betweenpoints

.

1ic pipe general l y has 1ower ex-pansion co eff ic ien ts and can handle the expansionwithi n the f ibers o f the material, thus doesrequire expansion points .when buried, can be subjected t o external corrosionfrom ground water and el ec tro ly s is and thus mustbe protected by coatings and wrappings.tunnels and trenches have been used to protectstee l pipe such as i n I celand and Klamath F alls ,Oregon; however, th is may double the cost o f theinstal lation.o f future expansion and access fo r maintenance.Other u ti l i ti e s can als o be lo cated i n the sametunnel. I n Iceland and Klamath F alls , i t also

F inally, metallic piping,

Concrete

The advantage o f the tunnel i s ease


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used as a heated sidewalk i n the winter.

For short piping distances, insulation willprobably not be necessary as the temperature loss

will be minimal. Depending upon the temperatureof the fluid, the flow i n the pipe and the toler-able loss i n temperature, longer transmission dis-tances may require insulation. In addition tominimizing the heat l oss of the f luid, the insu-lation must be waterproof and water tight. Groundwater can destroy the value o f any insulation.Above ground and overhead pipel i ne instal 1ati onscan be considered i n special cases; however, i n-sulation wil l probably be necessary as they willbe exposed to wind which can remove considerableheat. Considerable insulation i s achieved by bury-ing the pipe. Burying bare steel pipe results i n areduction i n heat loss of about one thi rd as compar-ed to above ground i n s t i l l air. I f the soi l aroundthe buried pipe can be kept dry then the insulationvalue can be retained. The direct buried,ated system has been used successful ly i n Icelandover a distance of 60 km (37 miles). Piping can beinsulated w i t h polyurethane foam and fi ass.Below ground this should be protected wi th a PVCjacket and above ground aluminum can be used. Gen-eral l y 2.5 to 7.5 cm (1 - 3 inches) of insulationis adequate.

A t flowing ful l conditions the temperatureloss i s around 0.1 to (0.05 tofeet) for insulated pipelines, and about 10 timesthat for uninsulated, buried pipe. Pipe materialdoes not have a significant effect on heat loss;however, the flow rate does have a si gni f icant ef-fect. A t low flows (of f peak), the temperaturedrop is large, which must be taken into account in

the design of the system.

Heat Pumps. Heat pumps have been commercially avail-able since the but until recently were viewedmerely as an ai r conditioning uni t w i th the addedabil ity to provide space heating where the heatingrequirements were small.the heat pump has become a alternative toother conventional heating systems.

With improved efficiency,

The types of heat pumps that are adaptable togeothermal energy are the water- to-air and thewater-to-water. Ground water i s the source of theenergy and has the advantage that the temperaturevaries l i t t l e w i t h the seasonal weather changes: i ti s warmer than the ai r in winter, and cooler than

the ai r i n summer. Therefore, the heat pump outputi s relatively constant year round. Ground wateroccurs at temperatures from 4" to 27C (40" to 80F)throughout most of the continental US and in manyplaces i n the world, making i t possible to use aheat pump almost anywhere. Air source heat pumpsdo not have these advantages, and must use supple-mental energy during extremely cold or hot weather.

Heat pumps are available wi th heating capacit-ies of less than 10,000 (10,000 toover 5 mi ll ion (5 million and areessenti l y i Dual servi ceunits, those that both heat and cool. can operatewi th a geothermal source of 15" to 35C (60" to

whereas wit h a u n i t used solely for heating,the storage water temperature can vary from to49C tobe done directl y without the use of a heat pump

(Ryan, 1980).

Above 49C (120F) heating can

Water-to-water heat pumps can boost geothermalwater temperatures eff ici entl y approximately 33" to

to giving a range of service watertemperature of 38" to to for re-source temperatures from 4" to 49C to 120F).

Larger temperature boosts will reduce the COPbelow 3 as seen i n Figure 4 (Ryan, 1980). Largecapacity custom design water-to-water heat pumpsare also available to rai se temperature as high as

(230F). These are compressorunits w i t h special refrigerants. The COP will dropoff to about 2 for these units.

4. 5

4.0

3.5

3.0

2.5

STORAGE WATER TEMPERATURE

FIGURE 4

Heat Pump COP Water Temperature

An example of heat pump use f or cool ing andheating i s the off i ce building for the Church ofJ esus Christ of Latter-day Saints i n Sal t Lake Ci ty,Utah. Four low-temperature wells, ranging from13" to 24C to 75F) supplying up to(4,000 gpm), provide energy to a heat pump systemheating and cooli ng 63,400 (683,000 square feet)of off ice space. Three 9.5 (750 ton) liquid

systems (Freon. 12 and water) powered by600 kw hp) motors are used. A t times, in thefall and spring, the cooling and heat loads balance;

however, in winter and summer the wel ls are used asheat sinks to absorb excess heat or provide heat tothe system.

CASCADING

Geothermal resources can be used for many pur-poses such as power generation, space heating,greenhouses, industrial processing and bathing, toname a few. Cons dered i ndi v i dual l y,however,manyof these uses may have di f f i cul ty i n providing anattracti ve return on investment due to the high i n-i ti al capital cost.using a geothermal f lui d i n several stages o f u t i l -ization to maximize benefi ts.

T hus, we may have to consider

T hi s multistaged


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u t i1ization, where lower and lower water temperaturesare used i n successive steps, i s called cascadingo r waste heat ut i l izat ion.

Geothermal cascading has been proposed and at-

tempted successfully on a limited scale throughoutthe world. I n Rotorua, New Zealand, fo r example,a f t e r geothermal water and steam i s used fo r homeheating, the homeowner w i l l often use the wasteheat fo r a backyard pool and steam cooker(Lund, 1976). A t the Otake geothermal power planti n J apan, about 165 o f hot water i s furnishedt o downstream communities fo r space heating, green-houses, baths and cooking.the waste water from the pavement snow melting systemi s retained a t 65C (150F) and reused fo r bathingpurposes. (J apan Geothermal Energy Assoc. ,1974).Numerous other cascaded uses from power plants i nJ apan are either underway or being proposed a tMatsukawa, Kakkonda, Onikobe and Hatchobaru f o rspace heating, greenhouses and bathing (Minohara andSekioka, 1980).

I n Sapporo, Hokkaido,

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D

I n J apan, the Siramizu-gawa geothermal areaexists near Sounkyo, Hokkaido.geothermal potential fo r the area i s 500 to 600 tonsper hour with a steam temperature o f 140C (284F)and a hot water temperature o f (198F). Threenearby communit ies o f kawa City, Kamikawa Townand Sounkyo Spa expect to use the energy. I n addi-t ion to power generation, space heating, snow melting,greenhouse heating, f i sh breeding, poultry farmingand bathing are the main uses. To optimize the useo f geothermal energy a l inear programming method wasdeveloped f o r cascading. The primary ut i l izaton wasfo r power generation and to heat water. Secondaryuses were fo r space heating, snow melting and green-houses, with the f inal use for bathing. Fixed costs,

maintenance expenses and the temperature and flow o fsteam and hot water were optimized by this methodf o r the goethermal area (Yuhara and Sekioka, 1975).

The estimate o f

Another example o f cascading i s i n the Mostovskiregion o f the Kransnodar province o f the northernCaucasus i n the USSR (Dvorov, 1982).and limited greenhouse heating started i n 1976.1980 12 ha (30 acres) o f plast ic f i l m greenhouses and6 ha (15 acres) o f glass greenhouses producing 2,262tons o f ve etables were being heated geothermallywith 75C water.45C i s then used to heat catt le breed-i n g units, two cow sheds, one c a l f shed, a pigstyand a poultry yard. I n the f a l l and spring somewastewater i s also used fo r space heating and domestic

drinking water as well as fo r forage preparation.The wastewater a t 20" to 30C from thisstep i s then used fo r a 30 ha (74 acre) f i sh farmoperation producing 1,500 tons per year. I n thespring and summer some o f this water i s also usedto rrigate crops to increase agricultural growth.

A second cascaded loop from the wells i s used fo rspace heating of residential and industrial buildingsi n Mostovski.feet) o f f l oo r space fo r 10,000 people. The waste-water a t 40" t o 45C i s then used to

swimming pools, showers and laundries. Thewastewater at t o 30C also i s usedi n furniture shops for drying wood and to heat co-

Well d r i l l i n g

By

The wastewater a t 40" to

This covers 200,000 (2,150,000 sq.

oper's shops at timber mill s .(taking advantage o f the alkal ine nature o f thewater) , animal space heating and food enrichment,and concrete block curing i s also ca rrie d out.Work i s also being undertaken to use the fluids

for balneological purposes.process i s shown i n F igure 5.

Some wool washing

The entire cascaded

FIGURE 5 Geothermal Energy Usei n the Mostovski Region o f the

Krasnodar P rovince

A f inal point should be made about cascading.Load balancing and the capabil ity o f end usersmust be considered to make the process eff ic ient .Seasonal operations w i l l res t r i c t the use o f thewaste heat. For example, food processing o r al-fa l fa pelletizing plant would normally operateonly during the warmer months o f the growing sea-

son. A greenhouse operation, using the waste heatfrom these plants, would only need heat during thecolder months.from greenhouses might be considered for crop ir-rigation.crops are not being grown and when crops are beinggrown, the greenhouses do no t need heat. Yearround operations are thus, obviously easier tomatch i n a cascaded situation (Higbee, 1981).

I n a simi lar manner, the waste heat

However, when the greenhouses need heat,

SUMMARY

The enti re projec t fo r a di re ct use appl ic atio ni s made o f various components, whichwere discussed i n th is paper.develop and use a geothermal resource must bestudied thoroughly from both a technical and eco-nomic viewpoint. The technical (geologic and en-gineering) issues and the economic issues are i n-terrela ted to the extent that a potential user ordeveloper must continue analyzing the merits o f thedi rec t use projec t as additional data become ava il-able from the development acti viti es . F ifteenmajor areas o f consideration have been i de nti fi edtha t should be reviewed (Schul tz and Hanny, 1981).

These are:

The dec is ion to

1. Site selection - it must be near the re-source.

2. Geophysics - what can be afforded.


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LUWD

3.

4.

5.

6.

7.

8.

9.

10.

11.

13.

14.

15.

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Resource depth and cost.

Resource production.

Engineering what must be altered to ac-

commodate the geothermal fl d.Uti li zation factor (load factor) - ratioof average to peak load.

Use temperature including the minimum tem-perature that can be used and the temper-ature difference (AT).

Pumping costs.

F l u i d transmission.

Water quali ty - corrosion and scaling pot-ential.

Disposal.

Heat exchangers.

I nsti tutional considerations.

Environmental .Investment - financi and economical con-siderati ons.

I nteracti ve planning and analysis throughoutthe complete sequence of geothermal proj ect devel-opment, using the factors outlined above, will pro-vide a developer or user a basis for making de-ci si ons.

REFERENCES

Al l is , R.G., 1981; A Study of the Use of Downhole

Higbee, C.V. and G.P. Ryan, 1981; Greenhouse HeatingWith Low Temperature Geothermal Water, Transact-ions, Vol. 5, GRC, Davis, CA.

Japan Geothermal Energy Assoc., 1974; GeothermalEnergy Utilization i n J apan, Tokyo.

Karlsson, T., 1981; Geothermal Di strict Heating - TheIceland Experience, Univ. of I celand, Reykjavik.

Lienau, P.J., 1982; Geothermal Direct Use, GHC,Klamath Falls. OR.

Lund, J.W., 1976; Nonelectric Uses of GeothermalEnergy i n New Zealand, GHC Quarterly Bulletin,Vol. 1, Nos. 3 and 4, Klamath Fall s, OR.

Lund, J . W . ,1979;Worldwi de Di rect Appl cation Re-view, A Symposium of Geothermal Energy and I tsDirect Uses i n the Eastern US, Special Rept.5, Davis, CA .

Lund, J . W. , 1980; Direct U ti l ization of GeothermalEnergy in the People's of China, Exhib-ition Mgmnt. I nternational, I nc., Dall as, TX.

Minohara, Y . and M . Sekioka, 1980; Non-ElectricUtilization of Geothermal Water and Steam fromProduction 1 of Geothermal Power Stationsi n J apan, GHC Quarterly Bulletin, Vol. 5, No. 2 ,Klamath Falls, OR.

Peterson, E.A. and M. Reed, 1979; Direct Use of Geo-thermal Enerqy - An I nternational Review, Renew-

e Energy Sources for Developing Nations,UNESCO, iotechni c Press, London, England.

Ryan, G.P., 1980; Heat Pumps-

Space Heatingcations, GHC, Klamath Fall s, OR.

Heat Exchangers i n the-Moana Hot Water Area, Reno,GHC, amath Falls, OR (May).

Anderson, D.N. and J.W. L und, (Editors), 1979, Dir-ect ization of Geothermal Energy: A Technical

GRC Special Technical 7, , Equipment Used i n Direct HeatProjects, Proceeding of the F i rst

Cai , Y ihan, 1981;Present Status of the Utilizationo f Geothermal Energy i n the People's Republic o fChina, Energy Sources Laboratory, Tianjin Univ-ersi ty, j i n, PRC.

Culver, G.G. and G.M. Reistad, 1978; EvaluationDesign of Downhole Heat Exchangers for Di rectApplications, GHC, Klamath Falls, OR.

Dvorov, I.M. and V.I. Dvorov, 1982; USSR GeothermalResources and Their Complex Use, GHC Quarterly

Bulletin, Vol. 7, No. 1, K lamath Fall s,OR.

ENEL, 1976; Geothermoelectric Power ants ofderel lo and Monte Amiata, Serie Grandi ImpiantiENEL (Ente Nazionale Per Elettr ica) ,Rome, I tal y.

Fornes, A.O., 1981;Direct Use Geothermal DistrictHeating Projects i n the U.S.. .A Summary, GHCQuarterly Bull etin, Vol. 6, No. 3, Klamath Falls,OR.

Gudmundsson, J .S. and Gudmundur, P. , 7981; WorldSurvey of Low Temperature Geothermal EnergyUti l i zation, Nat'l Energy Authority, Iceland.

Geothermal Resource; Conference, GHC, amathFalls, OR.

Schultz, R.J. and J.A. Hanny, 1981; Industrial Pro-cessing Using Thermal Energy from GeothermalResources; Proceedings of the FirstGeothermal Resources Conference, GHC, amathFalls, OR .

Shannon, R. J ., 1982;Uti 1 Moderate-TemperatureHydrothermal Resources i n New Zeal and, Proceed-ings, Internati onal Conference on GeothermalEnergy (Florence, I taly) , BHRA ui d Engineering,Bedford, England.

Yuhara, K . and M . Sekioka, 1975; Application ofL inear Programming to t i purpose Util izationof Geothermal Resources, Japan Geothermal EnergyAssociation, Tokyo.

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