Everything about Solar Panels On Spacecraft totally explained
Spacecraft operating in the inner
solar system usually rely on the use of
photovoltaic solar panels to derive electricity from
sunlight. In the outer solar system, where the sunlight is too weak to produce sufficient power,
radioisotope thermal generators (RTGs) are used as a power source.
History
The first spacecraft to use solar panels was the
Vanguard 1 satellite, launched by the US in 1958.
Implementation
Solar panels need to have a lot of surface area that can be pointed towards the Sun as the spacecraft moves. More exposed surface area means more electricity can be converted from light energy from the Sun. Since spacecraft have to be small, this limits the amount of power that can be produced
Spacecraft that have used solar power
To date, solar power, other than for propulsion, has been practical for spacecraft operating no farther from the
sun than the orbit of
Mars. For example,
Magellan,
Mars Global Surveyor, and
Mars Observer used solar power as does the Earth-orbiting,
Hubble Space Telescope. The
Rosetta space probe, launched
March 2,
2004, will use solar panels as far as the orbit of
Jupiter (5.25
AU); previously the furthest use was the
Stardust spacecraft at 2 AU. Solar power for propulsion was also used on the European lunar mission
SMART-1 with a
Hall effect thruster.
The upcoming
Juno mission will be the first mission to Jupiter to use solar panels instead of the traditional RTGs that are used by previous outer solar system missions.
Power Available
In 2005 Rigid-Panel Stretched Lens Arrays were producing 7 kW per wing. Solar arrays producing 300 W/kg and 300 W/m² from the sun's 1366 W/m² energy near the Earth are available. Entech Inc. hopes to develop 100 kW panels by 2010 and 1 MW panels by 2015.
Future Uses
For future missions, it's desirable to reduce solar array mass, and to increase the power generated per unit area. This will reduce overall spacecraft mass, and may make the operation of solar-powered spacecraft feasible at larger distances from the sun. Solar array mass could be reduced with thin-film photovoltaic cells, flexible blanket substrates, and composite support structures. Solar array efficiency could be improved by using new photovoltaic cell materials and solar concentrators that intensify the incident sunlight. Photovoltaic concentrator solar arrays for primary spacecraft power are devices which intensify the sunlight on the photovoltaics. This design uses a flat lens, called a
Fresnel lens, which takes a large area of sunlight and concentrates it onto a smaller spot. The same principle is used to start fires with a
magnifying glass on a sunny day.
Solar concentrators put one of these lenses over every solar cell. This focuses light from the large concentrator area down to the smaller cell area. This allows the quantity of expensive solar cells to be reduced by the amount of concentration. Concentrators work best when there's a single source of light and the concentrator can be pointed right at it. This is ideal in space, where the Sun is a single light source. Solar cells are the most expensive part of solar arrays, and arrays are often a very expensive part of the spacecraft. This technology may allow costs to be cut significantly due to the utilization of less material.
It has been proposed that it may be possible to develop space-based solar plants —
solar power satellites with large arrays of photovoltaic cells-- that would beam the energy they produce to Earth using
microwaves or lasers. This could, in principle, be a significant source of electrical power generated using non-fossil fuel sources. Japanese and
European space agencies, among others, are analyzing the possibility of developing such power plants in the 21st century.
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