Solar mirror

A solar mirror is a viable means to collect fairly dispersed solar radiation and re-direct it to a point of ultimate use. A fair amount of investigation has gone into the concept for two reasons.

Solar radiation at the surface of the earth is fairly diffuse, containing only about 1 kilowatt of energy per square meter of area normal to the direction of the sun. To use this energy for anything from cooking to powering a turbine-electrical generator, this energy must be concentrated, a task normally assigned to flat or parabolic arrays of solar mirrors. Some examples of solar mirrors used to concentrate heat are discussed at Overview, being the large PowerTower design developed by Sandia National Labs, the Solar Dish Engine which uses a stirling engine heated by a solar mirror concentrator, and the Trough System.

Photovoltaic cells which can convert solar radiation directly into electricity are quite expensive per unit area, and, if cooled, are capable of converting efficiently up to 250 times as much radiation as is normally provided by simple exposure to direct sunlight. In tests done by Sewang Yoon, Vahan Garboushian and titled "Reduced Temperature Dependence of High-Concentration Photovoltaic Solar Cell Open-Circuit Voltage (Voc) at High Concentration Levels" available January 3 2005 at Yoon for Amonix Corp., the authors state that photocell percent conversion efficiency actually increases at higher levels of concentration, often by significant amounts, provided external cooling is available to the photocells. For this reason, particularly for Space Solar Power designs now being considered, Solar Mirrors can reduce photocell costs and launch costs since they are expected to be both lighter and cheaper than equivalent large areas of photocells.

A good overview of options possible for space-based solar power systems is this study supported by Boeing corporation, authors Seth D. Potter, Harvey J. Willenberg, Mark W. Henley, and Steven R. Kent and titled "Architecture Options for Space Solar Power" available January 3 2005 at Potter (PDF). In Fig. 4. captioned "Architecture 4. GEO Harris Wheel", the authors describe a system of solar mirrors used to augment the power of some nearby solar collectors, from which the power is then transmitted to receiver stations on earth.

Len Gould has made available an article titled "Tension Stabilized Steerable Orbiting Mirror" available January 3 2005 at TSSOM in which is described one interesting method to construct such an orbiting Solar Mirror.