Heat Transfer Fluids and Thermal Energy Storage for CSP. Pr Xavier Py PROMES laboratory UPR 8521 CNRS University of Perpigan Via Domitia

Transcription

1 Heat Transfer Fluids and Thermal Energy Storage for CSP Pr Xavier Py PROMES laboratory UPR 8521 CNRS University of Perpigan Via Domitia SFERA II , Summer School, June

2 Interest for TES in CSP Thermal Energy Storage : one of the major distinctive advantage of CSP before other Renewable Energies MW Backup or storage Toward storage Solar direct storage Allows: - ditpatchability - process optimization -process protection To resume: HTF and TES are the interface between the solar E input and the PB

3 HTF and TES : some of the current worldwide key priorities for CSP

4 HTF and TES : some of the current worldwide key priorities for CSP

5 Financial issues Effects of TES on financial issues: Increase in investment costs by the added TES and the increased size of the solar field The whole energy cost changes only marginally. The main merit of the TES: Not to reduce the cost ofelectricity But increase in plant capacity factor and yearly electrical output Supply of base-load power competing with fossil-fuel plants! Herrmann MW Andasol CSP Oil / molten salt

6 Environmental issues Green House Gaz Emissions Water consumptions Cumulative Energy demand 21% 27% GHG HTF 5.36 (20.6%) TES 5.01 (19.3%) 23% % 0.19 CED HTF (23%) TES (18%) 8% 38% % 36% ANDASOL like Trough CSP 103 MW 22% 1% 10 23% 9.4% 0.17 HTF: Therminol VP1 Solutia 15% 14% 6.3 h TES : Mined nitrate salt 1.6% % % 2.5% % 89.8% J. J. Burkhardt, G. a Heath, and C. S. Turchi, Life cycle assessment of a parabolic trough concentrating solar power plant and the impacts of key design alternatives. Environmental science & technology, vol. 45, no. 6, pp , Mar

7 Raw materials availability About 60% of the solar salt are from mined nitrates from Chile, others are from chemical industry Use of synthetic salt only increases the TES GHG content by 52% Phil E., Kushnir D., Sanden B., Johnsson F. Material constraints for concentrating solar thermal power. Energy 44 (2012) Burkhardt J.J., Heath G.A., Turchi C.S. Life Cycle Assessment of a Parabolic Trough Concentrating Solar Power Plant and the Impacts of Key Design Alternatives. Env. Sci&Tech. 45 (2011)

8 Needs in analysis of the State of the art HTF and TES for identification of bottlenecks and possible innovative approaches. LETS go Through Historical HTF and TES in CSP Some illustrative exemples.

9 History : first French Tower-CSP pilot First Historical CSP molten salt techno. : Thémis France Targasonne France MWe 560 C 550tons of molten salt as HTS and TESM 40 MWh 5h Captage Tour Direct and active TES 40%NaNO 2 7% NaNO 3 53% KNO 3 T m 142 C Cp 1300 J/(kg K) r 1900 kg m -3 Stockage Molten Salt: Atm pressure Highly stable High operating T Afordable Mature techno but rather high solid. T Bloc électrique 100 m 80 m heliostats 53.7 m² 4 4 3,5 110 m² kwth Te 250 C Ts 450 C Héliostats Bac chaud Bac froid Générateur de vapeur kw 28% Tv 430 C Pv 40 bars

10 History : first USA Tower-CSP pilot Solar One USA: direct steam generation DSG tower CSP Steam as primary HTF TES using oil as HTF and a natural filler (rocks) TESM in the tank Thermocline approach: One unique stratified tank instead of two 30% in cost reduction before two-tank salt Extensively studied by Sandia lab. TES mode : indirect and passive Heat exchanger steam/oil In the thermocline TES unit: thermal oil 4230 m tons granit particles 2060 tons sand 244 C-304 C Discharge through a steam producing unit gives steam at 274 C Major failures at the receiver due to DSG

11 History : first USA Tower-CSP pilot, second step SOLAR TWO 12.4 Mwel From Solar One Barstow Californie Molten salt : NaNO 3 /KNO 3 Higher solid. T TES mode : Direct and active Efficiencies : receiver : 88% storage: 97% steam cycle: 34% whole efficiency: 13.5% 42 MWth 430 kw/m 2 24 panels of 32 tubes Tubes : 316 stainless steel 2.1 cm diam 1.2 mm wall Pyromark paint 95%abs

12 TES is not only a TESM but also : Tanks Pumps Tubings Heating elements Insulations Fundations Insulation : 30 cm rockwool fibers + 5 cm glass fibers + Alu covers Insulation : 46 cm rockwool fibers + 5 cm glass fibers + Alu covers 897 m m kwe soaked heating elements

13 History : first USA Tower-CSP pilot, second step Molten salt inventory TES is also concerned by material Handling and pretreatments 16 days needed for first melting

14 History : in USA Trough-CSP industrial Plant Oil as heat transfer fluid and TESM SEGS I-II 1999 at SEGS I II Oil: High operating P Limiting highest T Flammable SEGS I Daggett California 14 MWe 1985 Trough CSP with mineral oil Caloria TES : 3h direct and active mode Two-Tank, oil only cold 240 C 4160 m 3 /hot 307 C 4540 m 3 Invest. cost 25 USD/kWhth (24% tanks, 42%oil) Major fire and the end of oil based TES

15 Today : in solar trough CSP ANDASOL Granada Spain 2009 : today s «standard» for trough CSP 50 MWe h storage ( t molten salt binary nitrate) 625 collectors (12m lenght, 6m aperture) HTF solar oil A mix between SEGS and Themis/Solar Two 50 MWe 625 collecteurs (12m long, 6m ouverture) 260 millions euros 195 hectares tonnes CO 2 /an TES mode: indirect and active 15/12/2009 Oil: High operating P Limiting highest T Flammable

16 Today : the first industrial Solar CSP Tower PS10 (Sevilla) Steam buffer storage kwh/m /kwh PS10 Sevilla 11 MWe TES mode: Direct and active Mature but low capacity expensive Storage capacity 50 mn at 50% : 25 MWh steam 40 bars 250 C

17 Gemasolar 2011: 15h of TES 20 Mwe T max 565 C Next Crescent Dune USA 110 MWe Today : the first industrial 24h/day Solar CSP Tower

18 Limitations, alternatives and perspectives For both HTF and TESM Increasing T limits in both low and high T Maximizing heat transfer properties Enhancing compatibility between HTF/TESM and containing materials Increasing life time expectency under thermal cycling Reducing LCA impacts Reducing investment costs NEEDS in NEW HTF Low vapor pressure avoiding expensive pressure-rated tanks Exploring new fluid approaches (with nanoparticles, dense gas/particle suspensions, ) NEEDS in NEW TESM Exploring other TES technos. (Latent heat, thermochemical, compressed air) Reducing investment costs Reducing LCA impacts NUMEROUS issues only some illustrative exemples for today in the following slides

19 Alternative fluids : Water steam in SF Eco-friendly oil (organic) Other molten salt Gaz (hot air, CO 2 ) Enhanced molten salt (nanoparticles, ) Dense gaz-particle suspensions DLR air/sand concept Air-sand heat exchanger for high-t storage. ES Proceeding of ES2009 July 19-23, 2009, San Francisco, California USA/ J.F. Hoffmann AQYLON PROMES

20 The Natural Nitrates from Chile to keep as HTF but not as TESM Raw Material availability : the nitrate salt About 800 /t today 0.8 Mt 133 Mm 3 wastes 417 km² polluted surface > 100 ghost plants (P. Marr 2007) Before CSP needs : 9 to 21 Mt/year of nitrates!

21 Alternative TESM: rocks as TESM ETH Zurich, plant Morroco Air as HTF in solar trough CSP and TES on packed bed of rocks

22 deshydratation hematite deshydroxylation Thermal behaviour of natural minerals Needs in stabilization Thermal Analysis (DSC): Setsys Cetaram Si 2 O 5 Al 2 (OH) 4 Kaolinite C Al 2 O 3.2 SiO 2 MetaKaolonite 980 C Al 2 O 4 Si Spinel 3Al 2 O 3.2 SiO 2 Mullite 1400 C Melting

23 Sensible heat TES over solid media: concrete for CSP Developped by the DLR Advantages Low cost of the TESM, Easy manufacturing, High availability, Modular and simple system, High potential with PCM for DSG plants Drawbacks Limited operating temperature Life time expectency First heating step (water departure) Embodied Heat Transfer Exchanger

24 Sensible heat TES over solid media: concrete for CSP

25 Sensible heat TES over solid media: concrete for CSP Simulation ANDASOL 50 MWe ~ 300 m storage unit storage unit storage unit storage unit ~ 100 m Photo: Solar Millenium AG

26 French approach developed at PROMES Sensible heat TES Solid media ASBESTOS Containing Wastes (ACW) : 174 Mt of Asbestos used during the XX century worldwide MUNICIPAL SOLID WASTES INCINERATORS FLY ASHE EU(15) : 1.6 Mt/year COAL-FIRED POWER PLANTS FLY ASHE 750 Mt/y World EU(15) 42 Mt/year METALURGIC SLAGS Steel > 411 Mt/y World Copper > 25 Mt/y

27 Asbestos Containing Wastes (ACW) and Fly Ashes Wastes (FAW) Sensible heat TES Solid media glass Asbestos Containing Wastes 1400 C ceramics Fly Ashe Wastes glass Possible moulding ceramics Cost of treatment : 1200 euros/t paid by the ACW owner Landfill disposal : 150 to 750 euros/t Embodied E & GHG payback: one year of new use in CSP Commercial price : 8-10 euros/tonne

28 THERMAL BEHAVIOURS ACW (same for CFA) from glass from ceramics 70% pyroxènes 30% Wollastonite - Akermanite

29 Cp (J/kg K) Cp (J(Kg K) STORAGE CAPACITIES ACW ceramics r = 3100 kg/m T ( C) 1200 r = 2975 kg/m FAW ceramics T ( C)

30 lambda (W/(m K)) Lambda (W/m K) 2,5 THERMAL CONDUCTIVITIES 2 1,5 1 0,5 ACW ceramics l 1.5 W/(m K) 0 2, T ( C) 2 1,5 FAW ceramics 1 0, T ( C)

31 EMBODIED ENERGY PAY-BACK TIME J/g from electricity consumption to electricty production) Mass yield: 14-26% E efficiency: 35-56% DH ind = 33.5 MJ/kg Process Lowest T C Highest T C Daily cycle Nb E e /E m ratio Payback Nb cycle CSP trough CSP air tower A CAES PB efficiency: 33% Pay-back time: 2 months to 2 years

32 Sensible Heat Thermal Energy Storage Materials for CSP

33 Temperature ( C) Temperature ( C) 1000 Thermal fatigue and thermal shocks under air C C/min 2 kw dt/dt = 100 C/min Fatigue tests Thermal shocks a measurements d= 25 mm L= 200 mm Surface T 10 mm 25 mm 40 mm dt/dt = 300 C/min Time (min) dt/dt = 2500 C/min Time (min)

34 REFRACTORY BEHAVIOR : Ultrasonic echography study GEMH Limoges ACW Ceramique

35 Compatibility with CSP HTF Thermal cycling under air 30 bars 610 C, 2500h On ACW ceramic and CFA ceramic In molten salts: High compatibility of all recycled ceramics and nitrate No compatibility with other salt (sulfate, carbonate, phosphate)

36 TES based on Latent Heat (PCM) T ( C) Sensible heat L Latent heat L/S domain S W = 2 Variance W = 1 W = 2 t (s) Phase rule : w = C r + 2 j C number of components, r number of reaction, j nomber of involved phases

37 Numerous PCMs In the T Range of CSP TES based on Latent Heat (PCM)

38 TES based on Latent Heat (PCM) Main advantages Q W/g (1) High storage capacity (2) Self regulated temperature (3) Modular system (4) Wide possible working temperature range Main disavantages (1) Subcooling phenomena (2) Thermal conductivity (3) Corrosion (4) Thermique and chemical stability (5) Toxicity Cp solid melting solidification Sub cooling T melting T solidification Cp liquid t (s) T ( C) (6) Inflammability (7) Price (8) Disponibility End of melting Thermal effect delayed by thermal diffusion

39 Thermal conductivity (W m -1 K -1 ) TES based on Latent Heat (PCM) MWe 100 kw/m 2 < 400 C (oil) Stockage chaleur Latente L/S - Inorganic PCM - graphite /salt composites? kwh/m 3 (DT 0 C! ) ~ 30 /kwh h th-el ~ 30-40% NaNO 3 /KNO C targuet raw salt graphite content (%wt)

40 TES based on Latent Heat (PCM)

41 HTF and TES for CSP Conclusions Numerous innovative approaches but few mature ones High potential of CSP enhancement High potential of research and business T C But : Costly R&D tasks Few involved people Difficulties to find funding for large scale pilot

42 HTF and TES for CSP A wide and wonderful research and industrial world with still so much work to achieve!!! Then, PhD students, we need you! SFERA II , Summer School, June