Solar power satellites or PowerSats are a theoretical space solar power renewable energy source that would involve placing satellites into orbit and using microwave power transmission to send solar power to a large antenna on Earth for distribution to the grid. The advantages of solar power satellites include exposure to light at all times unobstructed by weather or the day/night cycle, being a renewable energy source, higher light absorbtion due to being outside the atmosphere resulting in more intense light and more frequencies available, zero emissions after being launched, and no waste production outside of maintenance of the satellite and reciever.
Solar power satellite cost remains the main problem. Even with all of these benefits they are still just in a theoretical stage due mainly to cost. Construction of the satellite itself is very expensive in addition to the high cost of launching it into orbit. In order to compete with conventional energy sources the following things will need to happen. Lower launch costs such as a space elevator or magnetic track launcher. Government or industry regulations on fossil fuels which stimulate the renewable energy market. Conventional energy prices rise enough to make the costs of altnerative energy more feasible.
Not all of this needs to happen in order for solar power satellite systems to be possible but some of it does. Technology already exists in the fields of satellites, wireless power transmission, and solar power to make this work, the solar power satellite negatives are all based around cost. However, these expenses do not amount to too much more than conventional energy sources. Construction, launching, maintenance, and utilization of solar power satellites is much higher than coal power plants for example but the fuel used is free which results in a huge cost benefit in the long term. Energy prices around the globe also differ by large margins. For example, in the US the average kilowatt hour is around 5 cents compared to the UK where electricity can cost 9-22 cents per kilowatt hour on average. This means solar power satellite cost can be offset quite a bit by deploying them in areas where electricity is the most expensive.
There are different solar power satellite orbits possible. Each of these orbits has advantages and disadvantages over the others. The different orbits are Low Earth Orbit, Geosynchronous Orbit, and Sunsynchronous Orbit. Low earth orbit results in the shortest possible transmission distance, lower costs to place into orbit, and energy delivery to most of Earth. Geosynchronous has the highest transmission distance, can provide power to a specific location at all times, less risk of debris or other collisions taking place, and antennas do not need any adjustment after being setup. Sunsynchronous is about halfway to geosynchronous resulting in smaller transmitting antennas which means lower cost, just two sunsynchronous satellites could provide energy for most of Earth during peak demand, exposure to the sun is around 99% of the time except during solar eclipse, and no competition with other satellites in geosynchronous orbit.
While solar power satellites, SPS, PowerSats, or space solar power remains too expensive in the current energy economy they are certainly a possible future renewable energy source. If the energy markets change a bit or some basic or not so basic technology emerges we could be seeing them in use in the very near future. There are of course various safety and international issues that would need to be resolved as well. The most basic solar power satellite safety issue is the use of microwave transmission. However, even in theory the beam couldn’t become powerful enough to cause death or even serious injury to anything inside it even for prolonged periods. The beam could be protected on the ground by fencing around the antennas and aircraft flying through it would already be equipped with a faraday cage built in to protect from lightning or other EM disturbances. Some people have suggested locating antennas offshore but this presents extensive cost and maintenance issues.
Some international or political issues surrounding solar power satellites are defending against attack by other nations. It would be extremely cheap and easy for a country with a space program to destroy satellites at the moment but such attacks would also destroy other satellites in the same orbit. More likely attacks are based on hijacking the computers of these satellites are changing their orbits as a way to extort countries or energy companies that control them or even simply to steal the satellite.
There are a great number of issues surrounding solar power satellites but none which are particularly difficult to solve in the near future. Hopefully some technological advances will be made to satellite launching which will enable this technology to be used soon.Sponsors: