Solar Thermal

At the present stage of technology development the major applications for utilising solar thermal energy are for heating swimming pools, heating water for domestic use, and heating of buildings. In general the collectors used are flat-plate solar-energy collectors in a fixed position. In order to achieve the highest heat collection efficiency the collector (in the southern hemisphere) should face as close to north as possible, angled at a slope roughly equal to the latitude plus or minus about 15 degrees.

Solar collectors fall into two general categories: nonconcentrating and concentrating.

In the nonconcentrating type, the area collecting the solar energy is the same as the area absorbing the energy. Whereas in concentrating collectors, the area collecting the solar energy is greater, sometimes hundreds of times greater, than the absorber area. Concentrating collectors are generally used where greater energy conversion efficiencies are needed, as, for example, when the heat generation is to be very high, as in the production of steam.

The flat-plate collector design is a relatively simple one consisting of:

  • flat-plate absorber, which intercepts and absorbs the solar energy,
  • a transparent cover(s) that allows solar energy to pass through but reduces heat loss from the absorber,
  • a heat-transport fluid (air or water) flowing through tubes to remove heat from the absorber, and
  • a heat insulating backing.

Solar Thermal Electricity Generation

Solar Concentrator

Solar thermal power plants use the sun's rays to heat a fluid, for the production of high pressure, high temperature steam. The steam, in turn, is converted into mechanical energy in a turbine and into electricity from a conventional generator coupled to the turbine. Solar thermal power generation uses the same conventional technologies of power generation except for the fuel source providing the heat energy for steam production. Solar thermal technologies for electricity generation use concentrator systems due to the high temperatures needed. Currently there are three types of solar-thermal power systems in use or under development: the solar dish, solar power tower and parabolic trough. The parabolic trough is the most advanced of the these systems to date with the technology used in California on a relatively large scale. Australia has some exciting development in the area of solar trough.

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