Figure 22.11: A solar thermal electric power system.
The mechanical energy can be further used to drive an electrical generator. The
collectors are built as concentrator systems in order to reach the high temperatures of
several hundreds of degrees Celsius, which are required to operate the heat engine.
One problem of CSP systems is that the efficiency of the collector diminishes as its
operating temperature rises, while the efficiency of the engine increases with temperature
as we have already seen when discussing the thermodynamic efficiency limit in Section
10.1. Hence, a compromise between the two has to be found when choosing the operating
temperature. Current systems have efficiencies up to about 30% [187],
Now we will take a closer look at the solar concentrator system, illustrated in Figure
22.12. First concepts were developed by the ancient scientist Archimedes (287 BC–212
BC); Leonardo da Vinci (1452–1519) later designed some concentrators. Different types
of concentrators produce different peak temperatures and hence thermodynamic
efficiencies, due to the different ways of tracking the sun and focussing light. Innovations
in this field are leading to more energy efficient and cost effective systems.