moving forward towards low cost, dispatchable and ... · moving forward towards low cost,...

Moving forward towards low cost, dispatchable and competitive STE

by

Manuel Collares Pereira(Renewable Energies Chair-REC)

Solar Thermal Electricity (STE): the role of storage

• Quick review of present day technologies for STE

• R&D goals ,drivers and constraints to be faced

• Thermal Energy Storage -dispatchability

• PV and complementarity

• Linear concentrators : PT and LFR

• Advanced Optics (N.I.O.) is an essential part of a final solution

• Some recent solutions and specific proposals

• Final remarks

2

Main STE technologies

2D- linear concentrationtechnologies, PT anf LFR

3D- towertechnology

PT

LFR

2 x50 MW, 7 h St.

Parabolic Trough Technology (PT) - 50MW Plants

~7,7 hours of storage –molten salts

5

HTF- Dowtherm A (393ºC) and a two tank molten saltsstorage system

Required value of a 25 years PPA for a 150 MW, 4 hours storage, without any public financial aids and no escalation

2100

Stars corresponds to “normalized” PPAs or FiTs at their respective locations in Spain, India, Morocco , Israel and South Africa

STE costs are still not the same as those of PV, ( market ~4,2 GW vs ~400 GW of PV), but getting there…

Hypothesis: 10-30 GW will be built at that time.Some breakthroughs might accelerate this trend.

Source: ESTELA Position Paper

Storage value (NREL) 3-5 c/kWh

Storing Energy: electricity, heat…

• In batteries

• Today: 300-600 euro/kWhe stored

• Soon (2-3 years) (?!) – 150 a 200 euro/kWhe

• Duration: 10 years ?

• As heat:

• Today : 20 a 40 euro/kWhe

• Within 2-3 anos: 10 a 15 euro/kWhe– Duration: 20 years ?

Out. 2016| Manuel Collares Pereira7

Factor 10-20 X of diference in cost, today(and in thefuture?!!)

…and so…

• PV, no batteries : the cheapest solar electricitytoday-grid parity on “roof top”- autoconsumo; centralized production costs for grid injectionalready at or below fossil fuel production

• STE- CSP with storage (7 to 15h at nominal power); dispatchable electricity, muchcheaper than PV with batteries; also closer to being competitive by itself…

Out. 2016| Manuel Collares Pereira8

PV versus STE?

• Not in competition!

• Complementarity is clear

PV – decentralized (roof top, etc) and centralizedproduction during the day

STE- centralized dispatchable production

Abril 2016| Manuel Collares Pereira9

The Challenge for STE

Low cost electricity:

1) -increase efficiency in solar to electricity conversion

2) -reduce number of components and system cost + O&M costs

add storage (to add value: dispatchability)

1) This really means going up in temperature (today : 565ºC!)

2) Reduce costs: the three main technological options havediferent costs: LFR, perhaps, has the lowest potential cost , but, today still also the lowest efficiency!

11

12

PT Field size (50MWe)

7.7 hr storage : 2*A 2*A= 520 000m2

Receiver lenght= 86,7 KmTotal tube volume= (0.22l/m -70mm pipe) = 19m3

6m

Can the number oflines, components, pipe lenght bereduced?

13

Storage size: molten salts mixture

ΔT for sensible heat storage- 100ºC

Cp : 1.6-1.7 kJ/kg50MWe*7.7h= 385MWhE=M*Cp* ΔT*ƞeM = 385 * 10^6 * 3.6*10^6 / 1600/100/0.33 (kg)

M= 26 250 ton !

Binary mixture:NaNO3-KNO3 (60-40%); (T fusion= 223ºC)

Storage – sensible heat ; 290ºC<T<390ºC

14

Increasing operating temperature; effect on storage volume

www.uevora.pt

Simplified plant scheme: Linear concentrator field and a 2 tank molten storage concept

550°C

292°C

540°C

… a need for higher concentration!?

Further research- Molten salts

• High operating temperature is achievable withconcentrators, but:

- problems: materials corrosion at hightemperatures

- Mixture stability/degradation- Cost!- Operational problems ( we need operating

experience): start up, cloudy periods, turnoff/drain or keep warm

- (…)

16

NEWSOL (H2020)

A systematic tackling of the following problems:

• - molten salts for sensible liquid heat storage

• - high temperature performance: can concretebe used? … structural concrete…

• -concrete based high temperature thermalinsulation

• -slag materials for solid sensible heat storage

• -PCMs latent heat storage



Horizon 2020

1 (Coord) University of EVORA Portugal

2 ACCIONA Spain (Industry)

3 CSIC Spain (R&D)

4 SECIL Portugal (Industry)

5 DLR Germany (R&D)

6 LNEG Portugal (R&D)

7 YARA Norway (Industry)

8 SINTEF Norway (R&D)

9 AIMEN Spain (R&D)

10 SSensor Italy (SME)

11 ACCIONA Ingeniería Spain (Industry)

12 ApEHR Denmark (SME)13 ETH Switzerland (R&D)

Salts: the low temperature end

• Solidification/Fusion at 223ºC: is it too high?

• Come as close to ambient as possible

Find other salts and mixtures:

• Ternary, quaternary mixtures , (…)

19

Examples of possible molten saltmixtures with lower fusion points

20

Environmental Issue with heavy metals

21

Melchsee-Frutt, 04th March 2015

• Leakage of heavy metals into the soil and ground water

• High emissions due to Acidic Mine Drainage (PH 1,5 – 2,5 in superficial groundwater)

• Possible aquifer contamination

e)

22

SSA8/12

SCA6/12

SCA0/6

SSA0/4

SSA4/8

Calcium Aluminate Cement w/ slag incorporation (CAC+)

Two different concrete dosages were considered, maintaining the same type and content of binder but varying the type of aggregate:

CAC mix (w/c=0,5) refers to CAC concrete prepared with 100% siliceous aggregatesCAC+ mix (w/c=0,57) refers to CAC concrete prepared with a mix of 75% siliceous aggregates+ 25% SlagAdjustment of aggregates dosage for the concrete was made following Bolomey calculations

Experimentation

• T: 565ºC?

• High Concentration is necessary!

• Thermal losses are proportional to receiver area (A receiver) • C= A aperture/A receiver

• Iow thermal losses means a smaller receiver and that means higher C

• This has already been already proposed and achieved with 3D- towertechnology

23

Higher efficiency…

efficiency

25

Central Receiver (CR) technology – 19MW

TORRESOL: 19MWe + 15 hours ofstorage

2D- Linear concentrators?

• Tube diameter is a constraint…

• The choice of (evacuated) receiver tubes for high temperature performance is more or less“fixed” on the market!

• Diameter: 70 mm! (perhaps 80mm, 90mm…)

26

• Higher concentration means a larger aperture size• And that- in itself- has a very positive (cost reduction!)

side: • 2D- high concentration means that there will be less

collector rows, for the same power capacity, thus there willbe

• less piping• less HTF as well• less pumping losses and other parasitics• less O&M

• But how wide can the aperture be?

27

Higher concentration PT – 565ºC

28

http://www.google.pt/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=0CAcQjRw&url=http://www.worldfutureenergysummit.com/Portal/exhibitors/products/flabeg-holding-gmbh/solar-mirrors-engineering-services-for-solar-trough-collector-ultimate-trough.aspx&ei=IEjWVJjaBo3PaIyngegB&bvm=bv.85464276,d.cWc&psig=AFQjCNEoZ5MqTrsF-vSjbxjbCKxsQCEzvw&ust=1423415688037434

Concentration for a parabola with a tubular receiver

• C=a/2πr= 1/sin (θ) * sin(φ)/π

29

φ

a

mirror

+θ -θ(2ϴsun=0.52º)

ϴ=2.5xϴsun

C= 27 (φ=90)

2r=70mm

a= 5.93m

Are there limits to a?“Etendue”- a reminder

• Etendue is a geometrical quantity that measures the amount of “room” available for light to pass through

dU= dA*cos θ *dΩ• Spatial “room”: dA * cos θ (light is crossing dA in a direction θ) • Angular “room” (the solid angle) : dΩ

High efficiency Conservation of“Etendue”

Etendue through AB (fromthree identical flashlights) with an angular spread αassociated …

…is the sameas …

… Etendue (same threeflashlights!) through thesmaller area CD but nowhas a larger angular spreadβ

Maximal Concentration ?

• The problem is: given radiation incident on an aperture awithin a certain angular range (±) , how much can it be

concentrated- Cmax?

• Conservation of “Etendue” applied to the problem of maximal concentration (2D)

32

?

C=Cmax=a/b=1/sin (θ)

Non Imaging Optics (Ideal Optics)

A parabola is not an ideal concentrator!

• It is very far from the limit , just like anyfocussing type optics!!!

• C=1/sin (θ) * sin(φ)/π

33

φ

Cmax

CAP: a useful definition

• Cmax=1/sin (θ)

• sin (θ)*C= CAP <=1

• CAP is the Concentration Acceptance-Product θ is the half-acceptance angle of the concentrator with concentration C

• For a PT, CAP is <= 1/π ~ 0.3


Larger trough : go from ~6m to ~8m

35

~8m trough, same tubeIt means a smaller θ, i.e. highermechanical manufacturing and tracking accuracies !

Larger θ and higher C: second stage CXX-SMS solution

36

XX-SMS solution

• Comparison with Conventional PT

Tel Aviv February 201337

.[.

ηopt0 Cg CAP φ (deg) Aspect ratio

(Height/Width)

Aperture

Width (m)

Mirror

length (m)

PT 0.81 26.24 0.32 80.3 0.30 5.77 6.40

XX SMS 0.72 50.38 0.61 55 0.51 11.08 11.71[.

Alternative : Linear Fresnel Technology?

20-30 m6m

PSE Gmbh

But conventional Linear Fresnel is alsofar from the n.i.o. limits…

• CAP=C*sin(θ) < 0.45 (<0.3 for tubes)

39

Incident light with aperture 2*θ

C=a/R

C/Cmax=0.45 for the best case

ψ=40.4º (rim angle)

a

Besides…

• … etendue is not conserved

• i.e. less light goes towardthe receiver than is incidenton the reflectors (shadingand blocking)

• Large room for improvement

September18, 2009

Improvements• CLFR (concept proposed by

D. Mills et al.)

• it is a multiple receiverconcept

• Improves on EM- etendue matching, but does notachieve the highest possibleefficiency

• Does not use ideal secondstage optics

Improvements

• Solutions with second stageconcentrator: they improve the optical performance byusing non-imaging optics

• They do not (attempt) maximize EM yet, and thenature of the optics used, limits collector width, i.e., forces the absorber to be atconsiderable height

• (Picture from NOVATEC)

42

Advanced LFR technology : high concentration

can be more easily obtained…Evolution of (C )LFR technology:

-Enhancing average anual efficiency: new optics(seek“Etendue Conservation”)

-Enhancing concentration (seek maximal concentration)

-Keeping solar field costs low, as with theconventional LFR technologies (“flat” mirrors)

-the receiver is fixed (…)

Go further: advanced solution

• A multiple receiver solution

• It nearly matches etendue (highest collectionefficiency)

• It approaches ideal maximal concentration, through the use of a secondary; optimizationof primary and secondary toghether

September18, 2009

Possible solutions for A-LFR

Heliostats on an etendue conserving curve

A first prototype proposal

• C=66x

• Operatingtemperature 565ºC

• Receiver height~7m

• Module width(30m)

• Primary mirrorarea: ~750m2

Linear Fresnel Etendue matched

47

LFR XX-SMSC=74x(CAP~0.57)

70mm tube

acceptanceangle=0.88 deg(~3 suns)

20.11 m

SolarPACES 2014, Beijing

Latest proposal – MSALFR“…brings it all together”

48

Latest proposal – MSALFR“…bringing it all together”

49

L~24m

PrimaryTot

width (m)

Total mirror

aperture width (m)

Receiver

Height (m)

Number

of

mirrors

Mirror

width

(m)

φ (°) C (X) θ (°) CAP ηopt0

MSALFR

Optic

25.7 22 10.8 22 1 48.57 45 0.745 0.58 0.70

A- LFR plant: some operating detailsand storage integration

50

Expected results

50MW plant in Faro

565ºC: molten salts as HTF and 7 hours storage

Steam 540ºC- 110bar

(if LFR installed cost: 100-150 euro/m2 )

< 8-10eurocent/kWh

51

Location DNI (kWh/m2) Total average yearly

efficiency

Faro – Portugal (37ºN) 2200 0.147

Hurghada : Egypt (27ºN) 3000 0.163

April 2018| Manuel Collares Pereira52

T<580 ° C; with energy storage andsteam generation (540°C, 100bar)- 3.2 MWth - TSK- Flagsol- 1.0MWth - ALFR Ematched

University of Evora+ DLRYARA Industrial GmbHTSK Flagsol Engineering GmbHSteinmüller Engineering GmbHLeoni Kerpen GmbHEskom Holding SOC - South Africa

| Évora Molten Salt Platform - EMSP

April 2018| Manuel Collares Pereira53

| Solar Concentrators Testing Platform- PECS

54

N.I. Optics + Advanced LFR: a fair shot at low cost dispatchableelectrictyHigh concentration enhances efficiency (lower thermal losses) and substantially reduces:

Number of rowsFluid volumeParasitic power consumption

Fixed receiver substantially facilitates engineering, O&M

Many other possible configurations to be evaluated and demonstrated (Ex: mirrors on an Etendue Matching curve, diferent mirror widths, etc)

In conclusion

55

PV and STE are not competitors

PV- decentralized production + some centralized production(during the day)

STE- centralized production with storage (4-15 hours?)(coming into the grid , while the sun goes down, or when thereis no sun!)

Thermal Energy Storage is key!

25-40 euro/kWh, today, going to 10-15 euro/kWh in the nearfuture….

In conclusion

Thank you for your attention!

How far can we go ?The importance of storage

• How far can we go?

• A concept proposed by

David Mills ,Robert Morgan [ISES Beijing paper(2007)]

“Big Solar” i.e. solar for full power? Including thesupply of base load on a large scale?

56

34

US Solar Resources

100% US Power147x147 km2 park

BIG SOLAR!!!

Big Solar (a concept with storage on a daily scale)

California Electricity Grid (CAISO) hourly data for 2006

Turbogenerator capacity matched to peak California load

Collector: CLFR (2007)

Calculation hour by hour for whole yearSM1 means array produces at peak exactly the energy required by the turbine at peak;

SMX array has X times the area of SM1


92% correlation with SM3, no costly peaking plant needed!!!; peak turbine /peak load 50GW

Texas- Grid


63GW turbine/peakload; again ~92% correlation

California and Texas grid combined: ~96% correlation with 16 hours storage, SM3

US grid (scaled to 103GW peak) fed from California and Texas ; 96% correlation

30

Maturing the concepts…

• “Big Solar” + storage renders obsolete the concern with solar (Renewables?) not being for “base load”

• STE has useful daily and seasonal correlations with load; coal and nuclear do not.

• Little or no costly peaking plant is required (can use existing Hydro)

• Is this the time to start thinking that solar energy can be a MAJOR electricity provider on a par with conventionalsources?? !

• New Molten salt solutions and higher efficiencies…

• Energy STORAGE: a very hot topic!!!!

Maio 2016| Manuel Collares Pereira67

T<580ºC; c/ armazenamento de energia e produção de vapor (540ºC, 100bar)

- 3.2 MWth - TSK- Flagsol- 1.0MWth - LFR Ematched

(MSALFR – financ. CCDRA)

| Évora Molten Salt Platform - EMSPUniversity of Evora+

DLRYARA Industrial GmbHTSK Flagsol Engineering GmbHSteinmüller Engineering GmbHLeoni Kerpen GmbHEskom Holding SOC - South Africa

moving forward towards low cost, dispatchable and ... · moving forward towards low cost,...

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