Solar Energy Perspectives - IEA

Solar Energy Perspectives: Solar thermal electricity
the demise of Luz in 1991 was in 2005: the 1-MW Saguaro solar power plant in Arizona,
where an organic fluid, pentane, replaces the usual water/steam working fluid.
Decentralised small plants might be particularly relevant for isolated or mini-grids on islands,
remote rural areas or requiring connection to weak grids with insecure supply. They could
also contribute to more developed grids in conjunction with generation of heat and/or cold
for buildings (see Chapter 4), or process heat for industries and services (see Chapter 5). Small
plants could be based on any of the CSP technologies – troughs, Fresnel, dishes and towers.
Although the smaller size may suggest dishes would have a strong position in such
applications, this is not necessarily the case as the added value of CSP, whether small or
large, rests in its hybridisation and storage capacities. For example, the 30 m-high Aora Solar
Tower in Israel uses a pressurised-air volumetric receiver and a standard jet-engine turbine to
generate 100 kW electricity and 170 kW th heat from the sun or biodiesel, natural gas or
biogas (Photo 8.5).
Photo 8.5 Small-scale solar tower in the Arava Desert, Israel
Source: Boaz Dovev/Aora Solar.
Key point
Small CSP plants can provide dependable power to isolated villages.
Non-concentrating solar thermal power
Recent improvements in non-concentrating solar collectors, whether advanced flat-plate
or evacuated tubes, make it possible to develop solar thermal electricity without
concentration (although some collectors may incorporate low-concentration-level CPC
devices). Highly efficient collectors could warm pressurised water to 130°C to 160°C
(Photo 8.6). This heat could then run a thermal engine generating electricity. Solar-toelectric
efficiencies would be low in comparison to CSP technologies, around 10% at best,
which represents the lower end of PV efficiencies, but non-concentrating solar power
could capture both direct and diffuse sunlight (like PV modules) and thus expand the
geographic areas suitable for solar thermal electricity. In particular it might be suited to
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© OECD/IEA, 2011