19-04-2012, 03:46 PM
High temperature storage - Solar thermal application
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Need for Storage
• Output management tool to prolong operation after
sunset, to shift energy sales from low revenue offpeak
hours to high revenue peak demand hours, and
to contribute to guaranteed output
• internal plant buffer, smoothing out insolation
changes and provide freeze protection
• A surge capacity of thermal energy is also required to
protect the steam generator section from receiver
transients due to cloud cover.
Thermal energy can be stored as
• Latent heat in Phase Change
Phenomenon
• sensible heat
– In SOLIDS require use of charge discharge fluid
– In LIQUIDS can be stored in the heat transport
fluid itself
• Heat of reaction
• A combination of above methods
Nitrates and Nitrites salt systems
• NaNO3 (307oC) KNO3 (335oC) NaNO2 (282oC)
• K-Na-Ca Nitrate Mixture eutectic mixture (46:24:30) has
a melting point of 160oC
• K-Na-Li Nitrate Mixture melting points as low as 120oC.
More expensive than K-Na-Ca nitrates.
• HiTEC 7% NaNO3,53%KNO3 and 40%
NaNO2(142oC-480oC)