cool a building or to provide input for thermal industrial processes like processing food. The cooling would be performed with an absorption chiller. Rohr proposed that the system would be “more reliable and more cost-effective per square meter of reflective area” than large solar power tower plants, in part because it would not be sacrificing 80 percent of the power collected in the process of converting it to electricity. Design Heliostat costs represent 30-50% of the initial capital investment for solar power tower power plants depending on the energy policy and economic framework in the location country. It is of interest to design less expensive heliostats for large-scale manufacturing, so that solar power tower power plants may produce electricity at costs more competitive to conventional coal or nuclear power plants costs. Besides cost, percent solar reflectivity (i.e. albedo) and environmental durability are factors that should be considered when comparing heliostat designs. One way that engineers and researchers are attempting to lower the costs of heliostats is by replacing the conventional heliostat design with one that uses fewer, lighter materials. A conventional design for the heliostat's reflective components utilizes a second surface mirror. The sandwich-like mirror structure generally consists of a steel structural support, an adhesive layer, a protective copper layer, a layer of reflective silver, and a top protective layer of thick glass. This conventional heliostat is often referred to as a glass/metal heliostat. Alternative designs incorporate recent adhesive, composite, and thin film research to bring about materials costs and weight reduction. Some examples of alternative reflector designs are silvered polymer reflectors, glass fiber reinforced polyester sandwiches (GFRPS), and aluminized reflectors. Problems with these more recent designs include delamination of the protective coatings, reduction in percent solar reflectivity over long periods of sun exposure, and high manufacturing costs. Tracking alternatives The movement of most modern heliostats employs a two-axis motorized system, controlled by computer as outlined at the start of this article. Almost always, the primary rotation axis is vertical and the secondary horizontal, so the mirror is on an alt-azimuth mount. One simple alternative is for the mirror to rotate around a polar aligned primary axis, driven by a mechanical, often clockwork, mechanism at 15 degrees per hour, compensating for the earth's rotation relative to the sun. The mirror is aligned to reflect sunlight along the same polar axis in the direction of one of the celestial poles. There