[jmpman]

Will orbiting solar panels ever work? Now that starship is viable, payload cost to orbit will dramatically drop. Is it cheaper to have orbiting solar plants than solar/battery(or whatever long term energy storage)? It’s that baseload problem which makes the manmade fusion/fission attractive.

[mr_toad]

For a space based solution you have all the costs of solar, plus launch costs, plus the receivers are very large and costly themselves.

It’s never going to be cheaper than solar, but it does have the advantage of working at night and through cloud cover.

In the very long run it might make more sense to launch whatever’s using the power into space as well, saving on the cost of the transmission and receiving infrastructure, but also removing further sources of pollution from Earth.

[ComputerGuru]

No heat dissipation is a huge con.

[SoftTalker]

So you have orbiting panels that will do what? Beam the energy back to earth? Isn't the sun beaming energy to earth directly? What problems do orbiting panels solve?

[choilive]

I actually don't think space based solar to beam it back to Earth will ever really be practical short of a space-elevator style tether to transmit the electricity down. But some of the pros would be as follows.

* Capable of 100% capacity - power generation can be 24/7/365 if in orbits around the sun or stationed at the Earth-Sun Lagrange points.

* Greater panel efficiency - less energy lost to the atmosphere that can be captured by the panels, closer orbits will increase efficiency even more due to more power/area

* Surface area - minimum 1x10^20 square kilometers of area you can build panels

There are of course many cons - but it could be a vital part to a space based industry - you need a lot of fuel or power to really do anything in space, and the power from space based solar could to be used to kickstart a fuel production facility off Earth. Fun stuff but not very terrestrially relevant.

EDIT: Some more numbers: You get about 40% more power/area in space vs on the ground. You need about ~22 TW to "power" humanity. So you need about 70,000 km^2 of space based solar assuming 25% end to end efficiency, which might be a generous estimate. So lets round it to 100,000 km^2. But thats a significantly smaller area than the terrestrial equivalent of about 500,000 km^2. Right now it costs about $1B installed for a square kilometer solar installation, so we if can build solar panels on the Moon or something anywhere close to the same cost as on Earth (very very BIG if), potentially a difference of $400T dollars at todays terrestrial prices.

[Someone]

> You get about 40% more power/area in space vs on the ground. You need about ~22 TW to "power" humanity. So you need about 70,000 km^2 of space […]. So lets round it to 100,000 km^2. But thats a significantly smaller area than the terrestrial equivalent of about 500,000 km^2.

Those number are inconsistent with each other. Seems you calculated with 400% more power/area in space vs on the ground. That seems incorrect to me, as it would make space solar convert close to 100% of incident solar energy to electricity.

[choilive]

Ground based solar has a capacity factor of about ~25% depending on location, while a space based installation would have nearly a 100% capacity factor. So to generate the same amount of energy per year you need about 4x as many panels on the ground. I probably should not have said power but instead something like exajoules/year.

[pfdietz]

Another important issue is that in space, PV can be extremely thin. The actual active layer of semiconductor can be maybe 50 microns (for silicon) or less than 1 micron (for CdTe). This also suggests solar-powered electric propulsion in space can have high acceleration, limited by heat dissipation in the engine.