Solar Energy Perspectives - IEA

Chapter 8: Solar thermal electricity
equatorial humid climates and sunny islands, where global irradiance is good but direct
sunlight not so good.
Photo 8.6 Experimental generation of electricity from non-concentrating evacuated tubes
Source: SAED.
Key point
Non-concentrating solar thermal electricity uses diffuse and direct light.
Relatively low-cost thermal storage and fuel back-up could make this technology a useful
complement to PV, which is likely to remain less expensive for electricity generation in the
sunniest locations. Another option would be to design systems integrating production of
heat, possibly cold, and electricity, either altogether or with different outputs at
different times of the year. Current experimental designs are based on turbines or microturbines
using an organic mixture as heat transfer fuel, more appropriate than water for
relatively low working temperatures. Engines with pistons and valves like the Ericsson
motor could also be good candidates in this temperature range, but they are not
manufactured on an industrial scale yet.
Another possibility is to use non-concentrating solar collectors to pre-heat feedwater of coal
plants – as with concentrating systems though by necessity at a lower temperature. Here
again, the advantage would be to save some fuel while using solar heat to produce electricity
efficiently, with an investment limited to the solar field.
As mentioned above, solar chimneys or “up draft towers” could be used to create valuable
air circulation through a tall chimney (one kilometre height or more) from a large greenhouse.
The air flow would run turbines (Figure 8.8). The concept was tested small-scale in
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© OECD/IEA, 2011