Solar

From dKosopedia

Solar power is a source of renewable energy that produces little or not pollution in its operations (although producing the equipment may pollute), that is attractive because it protects the Environment, reduces production of greenhouse gases, and mitigates the energy supply concerns associated with a potential Peak Oil problem. It also lacks the concerns about long term waste disposal associated with Nuclear power.

All but a tiny fraction of our energy comes from the Sun. Name any kind of power source, trace back how that powersource came to be and chances are you're either talking about energy absorbed by the Earth from the Sun or elements that were here from before our solar system was even formed. See generally this Wikipedia Article.

Total incoming energy from the Sun to the surface of Earth is on the order of 10,000 times more than what we use as a civilization - but it's widely dispersed across the planet, and difficult to harness. Direct use of solar energy relies on two distinct technologies: thermal, or concentrating sunlight to heat things up, and photovoltaic (PV), converting sunlight to electricity using semiconductor devices.

Thermal technology is widely used today to heat swimming pools, reduce water heating costs, and heat space in buildings, though most require some form of backup power for cloudy days. Thermal approaches can also generate electricity by heating a working fluid that then turns a turbine. One of the latest innovations is the Solar Tower, a structure invented by German structural engineer Professor Jörg Schlaich. The concept is that hot air rises, and if you heat air under a sloped piece of glass, the air will move up. Put that sloped glass in a circle, with a tower in the middle to create the temperature differential and you've got electricity being generated from turbines at the bottom of the tower. One of these could provide 250MW of power, enough for 200,000 homes. An Australian company called Enviromission is currently doing the final studies and plans necessary to build one.

Most public interest in solar energy, however, is focused on PV applications. Historically, the main barrier has been the cost to power ratio. The cells themselves can be manufactured now for about $2.50 per peak Watt; installation costs tend to bump that up to $5-10/Watt at the consumer level. These prices are still something like a factor of 10 too high to provide practical utility-scale energy, but worldwide demand has been growing at 20-30% per year. In 2004 total production was about 1000 MW, demonstrating expansion beyond the space and remote-location niche markets photovoltaics had occupied until recently. The US Energy Information Administration has historical tables showing the modest improvement in solar module and cell pricing over the years; the most dramatic improvements happened with the large solar R&D budgets of the Carter administration in the late 1970s.

The US government continues to modestly fund solar PV research through the Department of Energy Energy Efficiency and Renewable Energy program. Eighty million dollars was allocated for this in the 2005 budget request. Much of this goes to research in exotic materials that can have very high conversion efficiencies; however these tend to be expensive and of questionable net environmental benefit with the toxic chemicals needed for their production. Actual sales of PV are almost entirely silicon cells, either in crystalline or thin-film (amorphous) form, with conversion efficiencies from 5 to 20 percent. Crystalline silicon cells are typically made from silicon materials discarded from semiconductor manufacturing processes. A variety of final module forms have been adopted to try to enhance adoption - roofing shingles, for example, can now be purchased with built-in solar photovoltaics.

The worldwide market is changing rapidly, and recently very much driven by government subsidies for purchases of PV. Japan now has the largest internal market for solar cells, and its production capacity has been expanding rapidly to keep up, thanks to strong government incentives. German subsidies have greatly expanded the rooftop solar electric market in that country.

A major disadvantage of solar energy systems is the night. PV can produce no energy when the sun is down, or hidden by clouds and weather. This means expensive auxiliary energy storage components or attachment to the electric grid is needed. It also means that the energy output of a 1 Watt cell is actually only 20-30% of a Watt, when averaged over a day, and this years installed capacity of about 1 GW is actually only supplying 20-30% of the electric energy of a typical GW-size nuclear power plant, exacerbating the cost issue for solar PV.

Solar panels in Outer Space can be in full sunlight all the time and provide continuous power; this provides one of the major proposed advantages for utility-scale production by Solar Power Satellites.

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Technical Overview