Page 260 - Alternative Energy Systems in Building Design

236 PASSIVE SOLAR HEATING TECHNOLOGIES

Figure 6.10 A passive solar tower concentrator. Courtesy of Solar Reserve.

referred to as heliostats, that reflect the sun’s rays onto the tower. Figure 6.10 shows a
passive solar tower concentrator.
The receiver contains a fluid that, once heated by a method similar to that of the
parabolic system, transfers the absorbed heat in the heat exchanger to produce steam
that then drives a turbine to produce electricity.
This technology produces up to 400 MW of electricity. The HTF, usually a molten
liquid salt, can be raised to 550°F. The HTF is stored in an insulated storage tank and
used in the absence of solar-ray harvesting.
Recently, a solar pilot plant located in southern California that uses nitrate salt tech-
nology, Solar Two, has been producing 10 MW of grid-connected electricity with a
sufficient thermal storage tank to maintain power production for 3 hours. This has
rendered the technology viable for commercial use.

Solar Cooling and Air-Conditioning

Most of us associate cooling, refrigeration, and air-conditioning with self-contained
electromechanical devices connected to an electric power source. These provide con-
ditioned air for the spaces in which we live as well as for refrigerating our food stuffs
and groceries.
Technically speaking, the technology that makes refrigeration possible is based on
a fundamental concept of physics: heat transfer. Cold is essentially the absence of heat.
Likewise, darkness is the absence of light.