Solar Thermal is the answer to the sector that may not be adequately catered to by Solar PV. In Solar Thermal, Sunlight is concentrated by reflectors at a point or line, and the circulating medium that can be air, water or salt is heated to relative high temperatures varying between 70deg C to 500degC.Initially only solar water heaters were developed in this sector and remains to be the mainstay of it. However large Power Plants have been built for more than a decade now. Once water or any other liquid is heated at sufficiently high temperatures of 300-500 deg C, the rest is standard steam turbine electricity generation. All one may have to do is to replace the coal or oil or gas fired boiler with a Solar Heating/boiler system. For a variety of reasons, however, integration with combined cycle plants has been found to be more feasible, and implemented under the term ISCC(Integrated Solar Combined Cycle). Cost of a complete system producing electricity is high but competitive generally with Solar PV. There is another advantage to this system .Thermal energy can be stored much more economically and large volumes than electricity produced in PV. Five hours of storage at full load has become a common feature of large scale utility plants of 50-100 MW.
Technology differentiation within Solar thermal.
There are four technologies within Solar Thermal, largely depending on what kind of concentrating system is employed. That is the reason, it is also called Concentrated Solar Power (CSP), although CSP systems have been used in Solar PV as well. The four technologies are;
3)Linear reflectors 4)Solar dish
Essentially the difference is whether one focuses sunlight on a point like a furnace or a boiler or one does it in on a line or tube carrying a fluid. Parabolic troughs have been more popular, cheaper and are now an established technology. Parabolic troughs are more prone to indigenization, as it is mostly sheet metal work and structures and framing made out of steel. There is some glass work or plastic for reflectors requiring electroplating. Considerable know-how both in formal and informal sector exists in
Building a Solar Thermal (parabolic trough) Power Plant
According to the figures released by US Energy Information Administration, in January 2010,a solar thermal power plant to come on stream in 2012 would cost 4798 USD per kW. It takes three years to implement a 100 MW solar thermal power plant. If one deducts 1798 USD per KW for conventional power component, the solar component cost would be 3000 USD per KW i.e. more than 60% of the total project cost. It requires 25000 tons of steel, 12000 tons of glass and 20,000 cubic meters of concrete among major inputs. It is not round bar construction steel, although some of it is, but mostly it is steel fabrication supporting my argument that we can do it, and we will have comparative advantage in it. Over the years cost s and steel consumption would come down, but the nature of steel construction may not change. By comparison, a large coal power plant of600-1000 MW would require steel structures of 5000 tons, which in itself is a large number. Recently an ISCC plant built in
Solar thermal in the Middle East
Admittedly, there is more solar insolation in countries around Sahara than in