A Live Green, Live SmartTM Briefing 
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The sun is mankind's original energy source. As long as the sun continues to shine we can turn to it for heat, light, and electrical power. The technology is rapidly improving for harnessing and controlling solar energy as a source of stored energy for some of the same applications for which fossil fuels have been employed. There is special appeal for solar energy in locales that are remote from the energy grid, without recourse to other means of electrical generation: solar energy is plentiful and has the highest power density of any energy source; it is also pollution free after its technolgical apparatus has been manufactured, and its harnessing technologies require little maintenance.
Solar heating is the most obvious use for harnessing the sun’s power. Solar heating of the home, as a replacement for traditional furnaces, relies on collection of sunlight, storage of this energy, and a system for dispersion. Heating water with solar can reduce the need for a conventional system by 2/3 in the average household. Households with swimming pools can install either passive or active systems for heating the hundreds of gallons of water they contain.
Solar heating systems employ three basic elements: thermal collectors, a storage tank, and a circulation loop. An active system uses a pump to circulate water, or another heat transfer liquid; a passive system, or a thermo siphon system, uses natural circulation to move water or a heat transfer fluid. These systems are the least expensive, and the most widely used. The manufacture of the systems and transport of them to end-users requires, at this writing, conventional energy sources. But once in place, solar heat and storage provide clean, safe, non-polluting energy with easily updatable entry-level technology.
As sunlight travels through the Earth’s atmosphere, the atmosphere absorbs 16% percent of it, and 6% becomes “insolation,” surface radiation available for storage as power. Current technology allows conversion of 15% of insolation into electrical power, through the use of photovoltaic cells that collect and convert sunlight directly into electricity using semiconductors, solids able to conduct electricity between diodes. A familiar instrument that relies on photovoltaic cells is the hand-held calculator. According to the International Energy Agency, 10 or 12 of today’s average photovoltaic (PV) modules of forty half-inch to four-inch PV cells can provide enough power for a single household.
One large-scale solar thermal technology, concentrated solar power, uses configurations of mirrors to concentrate solar heat and then convert this captured energy to generate electricity in a steam generator. These are relatively low in cost compared to their potential for energy production. These systems can deliver power in areas or during times of relatively low sunlight, and, though not currently the most widely used systems, are the most efficient solar systems now available.
Another option available for fairly widespread use is the solar pond. These are simple and inexpensive; they are just sealed pools of water that collect and store energy from the sun using different layers of concentrated salt. The top layer is made with low salt content, the middle layer is made with a salt gradient that prevents heat exchange through the water, and the bottom layer contains a high salt content designed to reach temperatures of 90 degrees Celsius. The system then uses the heat that is trapped in this bottom layer either to circulate warm air and water, or to drive a generator to produce electricity – this electricity can be used for cooling in climates where too much solar heat is an issue.