Using solar panels in space to power spacecraft may seem like science fiction but in fact the first commercial use for solar cells, in 1958,was on a satellite. Photovoltaic solar panels, which convert the sun’s energy into electricity, are mounted on a range of spacecraft operating in the inner solar system (but not the outer solar system, where the sun’s rays are not powerful enough), to run the sensors, active heating and cooling and telemetry, and to provide the energy needed for propulsion.
How Spacecraft Use Solar Power
Most spacecraft are entirely reliant on solar panels to provide them with the energy they need to run their equipment, so large solar panel arrays are designed to turn so that they constantly face the sun even as the spacecraft moves. A tracking system is often integrated into the arrays to ensure they are always in the direct path of the sun. If a satellite’s batteries are fully charged or the amount of electricity generated is larger than the amount needed, operators on Earth can purposefully point the panels away from the sun.
Types of Solar Cells Used
Most solar cells used on panels in space are manufactured from gallium arsenide rather than silicon, which is the more common material utilised in solar panels on Earth. Although more expensive, gallium arsenide cells can absorb photons in the sun’s rays with up to 10,000 times greater efficiency than silicon. Spacecraft also tend to be equipped with solar concentrators, which are far more efficient than the average solar panel on Earth. Solar concentrators do just that – they concentrate the sun’s rays using a lens to maximise the amount absorbed and therefore also maximise the amount of electricity that can be produced. Although some large-scale solar power operations on Earth now also use solar concentrators, they are ideal in space as they work best when there is a single light sourcefor the concentrator to focus on. Many solar panels used on spacecraft are fitted with tightly-packed solar cell rectangles rather than the solar wafer circles typically used on solar panels on Earth, allowing them to cover close to 100% of the sun-exposed surface as opposed to the 90% on Earth-bound panels.
The Future of Space-based Solar Power
Like solar technology on Earth, solar panels used in space will become more effective as efficiency improves, i.e. by reducing the number of solar panels needed whilst increasing the power generated per cell. The most exciting development in space-based solar power is the concept of collecting solar power in space and beaming it back to Earth for use right here on our planet. The potential of this is enormous as the solar energy available in space is billions of times greater than that which we can capture on Earth. Using solar power satellites, solar cells could collect photons for 24 hours a day, without issues with incremental weather, rather than the 12 on Earth, and the intensity of that energy is far greater. There are currently issues regarding cost and the method by which the energy is transmitted back to Earth but, ultimately, space-based solar power could significantly help to solve our energy problems.
Emily Buckley is journalist and copywriter & passionate about heralding in a future powered by renewable energies such as solar powerand is currently writing a series of articles on the subject.