21-09-2008, 09:39 AM
Solar power satellite
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An artist's depiction of a solar satellite, which could send energy wirelessly to a space vessel or planetary surface.
An artist's depiction of a solar satellite, which could send energy wirelessly to a space vessel or planetary surface.
A solar power satellite, or SPS or Powersat, as originally proposed would be a satellite built in high Earth orbit that uses microwave power transmission to beam solar power to a very large antenna on Earth. Advantages of placing the solar collectors in space include the unobstructed view of the Sun, unaffected by the day/night cycle, weather, or seasons[1]. It is a renewable energy source, zero emission after putting the solar cells in orbit, and only generates waste as a product of manufacture and maintenance. However, the costs of construction are very high, and SPS will not be able to compete with conventional sources (at current energy prices) unless at least one of the following conditions is met:
* Sufficiently low launch costs can be achieved
* A determination (by governments, industry, ...) is made that the disadvantages of fossil fuel use are so large they must be substantially replaced.
* Conventional energy costs increase sufficiently to provoke serious search for alternative energy
In common with other types of renewable energy such a system could have advantages to the world in terms of energy security via reduction in levels of conflict, military spending, loss of life, and avoiding future conflict over dwindling energy sources.
History
An artist's concept of a solar power satellite, 1976. (NASA)
An artist's concept of a solar power satellite, 1976. (NASA)
The SPS concept was first described in November 1968 [2]. At first it was regarded as impractical due to the lack of a workable method of sending power collected down to the Earth's surface. This changed in 1973 when Peter Glaser was granted U.S. patent number 3,781,647 for his method of transmitting power over long distances (eg, from an SPS to the Earth's surface) using microwaves from a very large (up to one square kilometer) antenna on the satellite to a much larger one on the ground, which came to be known as a rectenna.[3]
Glaser then worked at Arthur D. Little, Inc., as a vice-president. NASA became interested and signed a contract with ADL to lead four other companies in a broader study in 1974. They found that, while the concept had several major problems -- chiefly the expense of putting the required materials in orbit and the lack of experience on projects of this scale in space, it showed enough promise to merit further investigation and research [1].
During the period from 1978 - 1981 the US Congress authorized DOE and NASA to jointly investigate. They organized the Satellite Power System Concept Development and Evaluation Program [4][5]. The study remains the most extensive performed to date. Several reports were published addressing various issues, together investigating most of the possible problems with such an engineering project.
For More Read
1.http://en.wikipediawiki/Solar_power_satellite
2.http://sciencemagcgi/reprint/162/3856/857.pdf
3.http://nsssettlement/ssp/library/1978DOESPS-InternationalAgreements(Christol).pdf
