How Energy Is Produced - The Renaissance of Renewable Energy - page 122

Coping with Intermittency
CSP technology is already capable of producing electricity at an industrial scale. As with
PV and wind, the main problem is intermittency. Moreover, CSP plants can only operate in
hot, bright, cloudless conditions. This makes them viable in only a narrow band of climatic
zones,andeventhereonlyduringtheday.Thermalstorageoffersawayaroundthisproblem.
During the day, some of the heat generated by the CSP plant is used for power production,
while some is diverted to a storage material, usually molten salts in insulated tanks (see
Figure4.38 ) .Thesesaltsfulfilthesamefunctionasthefluidthatrunsthroughalineartrough
concentrator, except that their main function is to store rather than to transport heat. Because
salts can be heated to far higher temperatures than oils (up to 550°C), they are more suitable
for stationary storage, though less suitable for pumping through pipes (IEA 2010b ; JRC
2011 ) . At night, the heat stored in the molten salts can be used to produce steam and thus
electricity.
Figure 4.38. Insulated storage tanks of molten salts at Andasol Power Station (Spain).
Source: Solar Millennium.
The Benefits and Costs of CSP
CSP can provide carbon-free renewable energy in countries or regions with strong sunshine
and clear skies. It can produce significant amounts of high-temperature heat for industrial