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Concentrated Solar Power Course - Session 4 - Thermal Storage and Hybridization


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Thermal storage for CSP plants:

* concept
* functions of the thermal energy storage system (tes)
* classification of tes systems
* state of the art
* future developments

Hybridisation of CSP plants:

* concept
* solar – gas hybrid csp plants
* hybridisation with biomass

Published in: Technology
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Concentrated Solar Power Course - Session 4 - Thermal Storage and Hybridization

  1. 1. Concentrated Solar Thermal PowerTechnnology TrainingSession 4 – THERMAL STORAGE AND HYBRIDIZATION<br />By Manuel A. Silva Pé<br />April 27, 2010<br /> <br />
  2. 2. ThermalStorageandHybridization<br />Manuel A. Silva Pérez<br />Group of Thermodynamics and Renewable Energy<br />ETSI – University of Seville<br /><br />
  3. 3. CSP Markets<br /><ul><li>Utility (centralized)
  4. 4. Capacity > 10 MW
  5. 5. Typesofutilitygenerators:
  6. 6. Base load (nuclear, coal)
  7. 7. Dispatchable (gas, CSP)
  8. 8. Intermittent (wind, PV)
  9. 9. Dispatchability: Theabilitytodispatchpower. Dispatchablegenerationreferstosourcesofelectricitythat can be dispatched at therequestofpowergridoperators; thatis, it can be turnedonor off upondemand</li></ul><br />
  10. 10. CSP Markets<br />Distributed generation<br />Capacity: 3 kW to 10 MW<br />Close to consumer<br />Reduces transmission losses<br />Reduces investment in transmission infrastructure<br />Stand-alone applications<br />Modularity, avaliablity, reliability<br /><br />
  11. 11. ThermalstorageandHybrization<br />CSP unique features within the RE technologies:<br />Thermal energy storage. Thermal energy produced by the solar field can be stored, thus decoupling power generation from solar resource.<br />Hybridization. Ability to hybridize with an alternative energy source –fossil or renewable fuel.<br />Thermal energy storage and/or hybridization provide the basis for CSP to be:<br />Dispatchable<br />Stable<br />Reliable<br /><br />
  12. 12. Why Energy Storage?<br />Increase operational stability <br />Reduce intermittence.<br />Increase plant utilization and capacity factor<br />Provides “peak-shaving” ability (time-shifted operation)<br />Reduce generation cost (as long as storage is cheaper than increasing rated power!)<br /><br />
  13. 13. Profile of the electricity demand<br /><br />
  14. 14. Solar-only electricity generation<br /><br />
  15. 15. Solar + Thermal Storage<br /><br />
  16. 16. Thermal energy storage<br />A fraction of the thermal energy produced at the solar field is stored, increasing the internal energy of the storage medium. <br />Sensible heat<br />Latent heat<br />(Thermochemical)<br /><br />
  17. 17. Types of thermal storage<br />By utilization<br />Short term<br />Provide operational stability<br />Medium term<br />Increase capacity factor<br />Shift electrical generation hours<br />By type<br />Direct (same substance as working fluid, does not require HX)<br />Indirect (different substance, requires HX)<br /><br />
  18. 18. Technical Requirements for TES materials<br />High energy density (per-unit mass or per-unit volume)<br />Good heat conductivity<br />Good heat transfer between heat transfer fluid (HTF) and the storage medium<br />Mechanical and chemical stability<br />Chemical compatibility between HTF, heat exchanger and/or storage medium<br />Reversibility for a large number of charging/discharging cycles<br />Low thermal losses<br />Easy to control<br /><br />
  19. 19. Thermal storage options<br />Source: Survey of thermal storage for parabolic trough power plants, Pilkington Solar Int. (2000)<br /><br />
  20. 20. Thermal storage past experiences<br />Source: Survey of thermal storage for parabolic trough power plants, Pilkington Solar Int. (2000)<br />
  21. 21. TES – STP commercial installations<br />Short term: pressurized water<br />PS10 and PS20<br />Mid term: Molten salt, 2 tank<br />Direct (CRS) – Gema Solar (Solar Tres)<br />Indirect (PT) – Andasol I<br /><br />
  22. 22. Short term TES<br />PS10 / PS20<br />Pressurized water<br />Sliding pressure during discharge<br />Pressure vessel<br />PS10 TES main characteristics<br /><ul><li>Max. pressure: 40 bar
  23. 23. Thermal capacity: 20 MWh (50 min at 50% load)
  24. 24. Total Volume: 600 m3
  25. 25. 4 tanks, sequentially operated</li></ul><br />
  26. 26. Molten salt storage, 2 tank, direct<br />Solar Two (Barstow, CA)<br />Thermal capacity proportional to ΔT<br />Hot – cold tank design<br />Commercial (salt widely used in process industry)<br /><ul><li>High operation T limited (salt decomposition)
  27. 27. Need for heat – tracing (risk of freezing)
  28. 28. Costly equipment (pumps, valves…</li></ul><br />
  29. 29. Molten salt storage, 2 tank, indirect<br />Andasol (Granada, Spain)<br /><ul><li>Provides high storage capacity to PT power plants (Thermal oil)
  30. 30. Intermediate oil-to-salt HX
  31. 31. Freezing Temp = 220 oC
  32. 32. High temp. limited by HTF
  33. 33. Large volumes
  34. 34. Higher investment costs</li></ul><br />
  35. 35. Andasol storage -Technical characteristics<br />Type: 2-Tank Molten Salt Storage<br />Fluid: Nitrate salt mixture (60% NaNO3 and 40% KNO3)<br />Melting Point: 223°C <br />Storage Capacity: 1,010 MWh (~7.5 hrs full load operation)<br />Storage Tank Size: 14 m height 37 m diameter <br />Salt Mass: 27,500 tons <br />Flow Rate: 953 kg/s<br />Cold Tank Temperature: 292° C<br />Hot Tank Temperature: 386°C<br /><br />
  36. 36. ANDASOL, Moltensalt 2-tank TES <br /><br />
  37. 37. TES – advanced experiences<br /><br />
  38. 38. TES – advanced experiences<br /><br />
  39. 39. TES costsandbenefits<br />Improves plant controlability and operability, expanding de range of possible operating strategies<br />Facilitates Dispatchability<br />If adequately designed, can improve<br />The efficiency of the plant<br />The profitability of the project<br />Extends lifetime of equipment (reduces the number of strat-stop cycles)<br />Increases investment<br />Oversized solar field<br />Tanks, HX, molten salt management equipment, heat tracing, safety<br />Increases O&M costs<br /><br />
  40. 40. Hybrid solar thermal power plants<br /><ul><li>Two energy sources:
  41. 41. Solar energy
  42. 42. Fossil or renewable fuel
  43. 43. Hybridisation of STP plant
  44. 44. Eases plant operation during transients
  45. 45. Eases turbine startup
  46. 46. Reduces number of turbine stops
  47. 47. Increases full-load operation time
  48. 48. Can be used to maintain temperature of HTF or storage medium</li></ul><br />
  49. 49. Hybridization options<br /><br />
  50. 50. SEGS 30 MW<br /><br />
  52. 52. ISCCS<br />3 projects in North Africa (Morocco, Algeria, Egypt)<br /><br />
  53. 53. HybridizationCostsandbenefits<br />Improves controlability and operability<br />Faciltates dispatchability<br />Improves plant overall efficiency<br />Improves capacity factor<br />Improves profitability of the plant<br />Extends equipment lifetime<br />Increases investment and O&M costs<br />CO2 emmissions<br /><br />
  54. 54. Thanksforyourattention!<br /><br />