Solar Light and Solar Lighting

Solar Energy in the form of light waves and related invisible waves reaches Earth after a journey of 93 million miles taking just over 10 minutes. The photovoltaic cell was first invented in 1972 and for many years its use was limited to space technology. It has long been the major source of power on satellites and the International Space Station. However, along with other technology that was first highly secret and used mainly by NASA, the "photo-electric" cell eventually became available to the general public, and over the last few years we have seen an accelerated use of the technology in many everyday products. One of these uses is lighting. 

There are probably more solar powered lighting products on the market than any other solar application. All of these products operate on the same principle. Solar energy falls upon a solar panel containing a number of photovoltaic cells - a photovoltaic cell is a silicon-based semiconductor  that has the property of being able to convert light into electricity. The amount of power produced depends on both the total area of cells exposed to sunlight as well as to the insolation (the amount of energy falling on a square meter at that latitude - greater at the equator than at higher latitudes) and is used in most cases to charge a battery, which in turn powers a light.

As recently as August 2005 saw the unveiling of a new type of solar light - Hybrid Solar Lighting. HSL was researched at Oak Ridge National Laboratory in Tennessee and is in the process of being marketed by a company named Sunlight Direct, which plans a product launch in 2007. Sunlight is collected by rooftop collectors - 4ft diameter mirrored dishes that track the sun automatically. The light is focused onto a bundle of optical fibers, which are connected to special light fixtures within the building. One collector powers eight such fixtures, which can be in the form of strip or spot  lighting and can illuminate a total of 10,000 square feet. At present the installation is very costly, approximately US $40,000  but the group hopes to get this figure down to $3,000 within just a few years. HSL has an efficiency of about 50% as opposed to photovoltaic panels, which are about 12% efficient. I predict that this latest technical breakthrough will be a major player ten years from now.