Solar Energy Perspectives - IEA

Chapter 8: Solar thermal electricity
cooling towers – of several-hundred-metre height. This concept, derived from the concept
of “solar chimney” (see below), creates an up draft through the temperature difference
between the air heated by the CSP plant, and the cold air at higher altitude. Originally
thought as an independent means of generating electricity (the updraft would have flown
through turbines), solar chimneys could simply cool solar plants, suppressing the need and
costs of both air turbines and fans – and the parasitic electricity consumption of the latter
(Bonnelle et al., 2010).
Storage in CSP plants
Technologies for heat storage are described in Chapter 7. The current dominant technology
for CSP plants is based on sensible heat in molten salts, whether for trough plants or solar
towers. Increasing the overall working temperatures of plants is the best means of
reducing storage costs. Adding nanoparticles to increase the heat capacity of molten salts
or other liquid storage medium is another option (mentioned above), while phase change
materials (PCMs) could be fixed inside the storage tanks with the same purpose. A third
possibility is to use thermocline separation (change in temperate with depth) between hot
and cold molten salts in a single tank, but leakage risks are more difficult to manage in
this case.
Photo 8.3 Dry cooling of the integrated solar combined cycle plant
at Ain Beni Mathar, Morocco
Key point
Dry cooling is a mature technology for steam plants in arid climates.
Storing the heat collected from the sun before generating electricity is much more efficient,
with a round-trip efficiency in the 95% to 98% range, than storing electricity, for which the
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