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Solar Power From Space

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Pacific Gas & Electric (PG&E) has signed with Solaren to take space-based solar energy from orbit via a microwave link. The agreement is to take 200 megawatts of power over a 15-year period. Solaren, a San Francisco based company, is looking for private investors to raise billions of dollars.

Solaren have people with space experience and have been talking to Lockheed-Martin and Boeing about the solar generation plant and the four rockets needed to send it into orbit. PG&E aren’t giving any money up front for this risky venture but will agree to buy the energy at an agreed price. This could allow Solaren to leverage some funding for what will be a monumental engineering feat that will cost billions of dollars. Each monster launch vehicle is going to cost around $250million a piece and Solaren say they need four of them which will cost an estimated one billion dollars.

Solaren expects to have a system up and running by 2016, and has a target of generating up to 1000 megawatts of energy. The sun shines almost continuously in space, so according to Solaren, they would generate an average of 850 gigawatt hours in the first year with 1,700 gigawatt hours coming online the following year. It seems that Solaren is planning on putting this power plant in geo-synchronous orbit (at low earth orbits the spacecraft moves around the planet so it cannot beam back the energy to one location) which means their assumption of launching 28 tons into orbit actually drops to about 8-10 tons for geo-synchronous. They may need a few more rockets.

All the geo-synchronous communications satellites already in orbit, and it is getting very crowded in this orbit, will likely not be pleased to have such a monster emitting microwave energy so close to them with interference as a distinct possibility. If anything should go wrong with the orbit control then this monster satellite would push many communications satellites out of orbit and probably take-out a few along the way.

There aren’t any technical details available for the solar power plant but it is going to take a lot of fuel, even using ion engines, to keep this beast in orbit. It would be interesting to see the details of the design trade-off studies that show this is a feasible design.

Solaren make the analogy of generating space based solar power and beaming it back to Earth like that of television broadcasting from suppliers such as Direct TV, who broadcast television radio-frequency energy to the planet. The only flaw in this argument is that the Direct TV energy is broadcast over thousands of square kilometers whereas this microwave energy is concentrated in a few tens of metres across, maybe a a tenth of a kilometre square. The Direct TV energy output is kilowatts and not megawatts so it is thousands of times less powerful in terms of signal strength. The Solaren energy level is going to be much higher.

The environmental issues are potentially enormous. For instance, does anyone know what the effect on birds, bats and insect life will be when these creatures have to pass through this microwave energy field? It can hardly be very healthy for them. The moon-glow is also likely to attract birds, bats, insects and animals, right to the microwave ‘frying-pan’.

PG&E and Solaren point out that US Department of Defense and NASA studies have given credence to space based solar power but while it is theoretically possible, it is still in the realms of science fiction, and maybe B-movie at best. It still seems better to accept the fact that solar power generated on the planet may have lower efficiency but at least it doesn’t have so many environmental and technical drawbacks as trying to put a solar power station in orbit, and you can stick them exactly where you need them – on your own roof.


Read Solar Satellite Reality Check
PG&E: http://www.pge.com/