Post on 24-Jul-2020
transcript
Thermal storage options for CSP
Thomas Roos
Overview
• Introduction: Why Energy storage?
• Options, TES concept and TES classification
• Different CSP systems: different TES
• HTF = oil, steam, molten salt and air
• Conclusion
Why energy storage?
• Mismatch in supply & demand
• Constant supply, variable demand
• Coal-fired baseload & peaked grid: pumped storage
• Domestic hot water geyser
• Intermittent supply
• Cellphone & laptop: charger & battery
• Household scale solar: PV and batteries
• Grid-scale wind or solar?
Energy storage options
• Electrical – batteries, capacitors
• Chemical – reversible chemical reactions
• Potential – clock weights, pumped storage
• Kinetic – flywheels
and
• Thermal – ice, hot water bottles, geysers and thermal storage for CSP
• Heat cheaper than electricity to store!
© OECD/IEA
2010
Source:
SolarMillennium
Thermal energy storage (TES) concept
• Oversize solar field and store excess heat
• Operate in cloud transients and at night
• Increase capacity factor
4 TES concepts, same field
Load Type
Storage
Turb
ine
Production Start
End
Ho
urs
Intermediate S M 08 19 11
Delayed M M 12 23 11
Baseload L S 00 24 24
Peak load L L 11 15 4
© OECD/IEA, 2010
Source: J Octobre & F Guihard, Systèmes Solaires, 2009
TES classification
• Sensible heat
• HTF itself: Steam, oil, molten salt, liquid Na (fire)
• Separate medium: concrete, molten salt, ceramic
• Mixtures: Fe, rocks, sand in conjunction with oil
• Latent heat
• Phase Change Materials (PCM: eg nitrate salts)
• Thermo-chemical storage (not yet)
© RENAC, 2009
Different CSP systems: different TES
• No one single TES type for all CSP systems
Config. HTF TES
Trough Oil MS: 2-tank, or 1-tank thermocline
Solid material (concrete)
Steam Concrete, PCM, Ruths storage
Molten Salt MS: 2-tank, or 1-tank thermocline
Tower Steam PCM, Ruths storage
Molten Salt MS: 2-tank, or 1-tank thermocline
Air Packed bed, solid matrix © RENAC, 2009
HTF = oil, TES = 2-tank molten salt
• Andasol 1 (50 MWel):
• D = 38.5 m, H = 14 m, Vol = 28 000m3, tstore = 7.5h
• Tcold = 292 °C, Thot = 386 °C (Oil T limited)
• 3 pumps in hot tank, 4 pumps in cold tank
© OECD/IEA 2010 Source: SolarMillennium © DLR, RENAC 2009
HTF = oil, TES = Concrete
• Metallic tubes 65 – 75% of cost
• Not yet commercially operational
©DLR, Tamme
HTF = steam, TES = PCM
• Meant for evaporation part of DSG plant
• Advantage: Const. T and ΔT during evaporation
©DLR, Tamme
HTF = steam, TES = PCM
• TPCM must match Tevap
• PCM: Salts >200 °C © DLR, RENAC 2009
Steam HTF, PCM TES
• kPCM controls heat transfer
• But ksalts are poor, so:
• PCM/graphite composite (h = 5-10 W/mK)
• Finned tube sandwich (h > 10 W/mK) © DLR,
RENAC 2009
HTF = steam, TES = PCM & concrete
• Pilot
• PCM evaporator (right)
• concrete superheater (left)
• Litoral power station
• Carboneras, Spain
© DLR 2011
HTF & TES = steam: Ruths storage
PS10: 40bar sat. steam pressure vessel
• Sliding pressure during discharge
• Thermal capacity is proportional to ΔT
• High CAPEX cost due to pressure vessel
• Not for large scale / high P applications
© DLR, RENAC 2009
HTF = MS, TES = 2-tank MS
• No HTF/TES heat exchangers
• Higher ΔT than MS/oil, so:
• smaller volume reqd.
• More efficient cycle
Trough Tower
Name Archimede Gemasolar
Site Sicily Spain
Turb. 5 MW 19.9 MW
Tcold 290 °C 290 °C
Thot 550 °C 565 °C
tstore 8h 15h
HTF = air, TES = solid media
• TSA used 1 MWh packed bed of spherical Al2O3 ceramic pebbles
• KAM use ceramic regenerator storage material at Jülich, 680 °C/120 °C
• Sand receivers and storage, and rock beds are receiving attention due to potential low costs
SUPSI, Switzerland
HTF = air, TES = solid media
• SUNSPOT concept (Stellenbosch University)
HTF = air, TES = solid media
• TES for solar gas turbines (≥800 °C, >4atm)
• Currently no published solutions exist
• DLR have published a simulation of a pressurised packed bed of steel pebbles
• Wilson SolarPower: SolarBatteryTM “dry storage medium”
• CSIR are building a CSP research facility, including storage:
• 100kWel gas turbine
• 500kWth heliostat field
• 3 hours high temperature storage
Conclusion
• Reiner Tamme of DLR says: The question is not
• “What is the best thermal storage technology?”
• but
• “What is the best CSP concept including storage?”
• The TES solution must match the CSP technology (no “one size fits all”)
Thank you for your attention!