Solar power satellite

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Space-based solar power (SBSP), or historically space solar power (SSP) is a system for the collection of solar power in space, for use on Earth. SBSP differs from the usual method of solar power collection in that the solar panels used to collect the energy would reside on a satellite in orbit, often referred to as a solar power satellite (SPS), rather than on Earth's surface. In space, collection of the Sun's energy is unaffected by the various obstructions which reduce efficiency or capacities of Earth surface solar power collection.

The World Radiation Centre's 1985 standard extraterrestrial level for mean solar irradiance at one astronomical unit from the Sun is 1367 W/m2.[1] The integrated total terrestrial solar irradiance is 950 W/m2.[2] Extraterrestrial solar irradiance is thus 144% of the maximum terrestrial irradiance, and has a different radiation profile, including wavelengths blocked by the atmosphere. A major interest in SBSP stems from the length of time the solar collection panels can be exposed to a consistently high amount of solar radiation. For most of the year, a satellite-based solar panel can collect power 24 hours per day, whereas a terrestrial station can collect for at most 12 hours per day, unless at the poles, but then only for 6 months of the year, if weather permits, and only during peak hours—irradiance under the best of conditions is quite reduced near sunset and sunrise.

Collection of solar energy in space for use on Earth introduces two new problems and can alleviate an existing one. First, installation of the collection satellites, and second transmitting energy from them to the surface for use. The first requires upgrading and extension of existing solar panel technologies. Since wires extending from Earth's surface to an orbiting satellite are neither practical nor currently possible, many SBSP designs have proposed the use of microwave beams for wireless power transmission. The collecting satellite would convert solar energy into electrical energy, powering a microwave emitter oriented toward a collector on the Earth's surface. Dynamic solar thermal power systems on satellites are also being investigated. Since the beam can be steered, it can be directed as needed to accommodate periods of high power use in particular locations (e.g., during the hottest part of the day in summer, or cold spells in winter). As well, one of the current problems of electricity use is long distance transmission from generating sites to usage sites. Because at least one type of receiving antenna, the rectenna, is relatively inexpensive, it may be possible to reduce the need for electricity transmission lines by sensible siting of receiving antennas, potentially reducing costs and grid interconnect failures, such as the blackouts of 1965 and 2003.

Some problems normally associated with terrestrial solar power collection would be entirely avoided by such a design, e.g., dependence on weather conditions, contamination or corrosion, damage by wildlife or plant encroachment, etc. Other problems will likely be encountered, such as more rapid radiation damage or micrometeoroid impacts.

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