Many people associate solar energy directly with photovoltaics and not with solar thermal power generation. Nevertheless, large commercial concentrating solar thermal power plants have been generating electricity at a reasonable cost for more than 15 years and some new solar thermal power plants are soon to be erected. This paper compares the two technologies, providing a short description of how they work, areas in which they operate and cost-developments. 1 Principles About one percent of the surface of the Sahara desert would be sufficient to supply the entire worldwide electricity demand from solar thermal power plants. For that reason, many people hope solar thermal power will be implanted in sun-belt countries. In contrast to photovoltaic plants, solar thermal power plants are not based on the photo effect, but generate electricity from the heat produced by sunlight. 1.1 Photovoltaics Semiconductor materials such as silicon are used in photovoltaic solar cells. In the cells incoming photons separate positive and negative charge carriers. This produces an electrical voltage and the electrical current can drive a load. Since solar cells are modular, they can be assembled in units of any size (Figure 1). An inverter converts DC voltage to AC and feeds the solar power into the grid…

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