This is probably the worst-case comparison for space solar, since it assumes you’re just going to pack a bunch of terrestrial systems onto a rocket and shoot them into space, where they will (just like terrestrial systems) only work at a fraction of capacity due to clouds, bad sun angles, getting dirty, and night-time.
In practice they would provide a lot more power per unit mass by at least one order of magnitude and possibly two. Mirrors in space can be relatively flimsy thin things and still work since they don’t need to withstand winds and other loads, giving relatively lightweight concentrated solar power options at much lower masses than terrestrial systems.
The conclusion is the same though: space launched solar is still not worth it for us now. It could be in the future or with some alternative history.
In practice they would provide a lot more power per unit mass by at least one order of magnitude and possibly two.
Can you elaborate more on that? It was clear to me that in space PV in space can give much more energy/mass than in Earth, but close to 2 orders of magnitudes is huge! Is this “only” due to temperatures losses + constantly running at full capacity + concentration?
Almost all of the mass of solar panels on Earth is structural strength to deal with various types of weather (mostly wind). That alone would increase power per unit mass by a factor of 5-10, though some of that would be eaten by beamed power equipment that isn’t necessary on Earth.
Permanent cloudless daylight with the light coming from an essentially fixed direction increases average power by a factor of about 4-6, while not affecting mass.
Using thin-film mirrors for concentration could enable even more power for given mass.
I am not really sure about that. There is not only a huge money cost but also a huge energy cost when sending something into orbit, would the panels even make back the fuel spent to send them? Even if the rocket hardware is reused 100% with no serious maintenance costs (reusing costs more fuel) would the panel even make back that fuel energy alone? I did not do the math but maybe not even that. If we could put them in orbit with a space elevator almost for free the tune would be way different though.
Oh yes, there is no question at all that they would make back the fuel energy cost. In money terms the fuel is a tiny fraction of launch costs (less than 1%). In fuel energy terms it costs about 400 MJ/kg to get payload into orbit via Falcon-9.
With fairly standard terrestrial designs you can get about 5 W/kg rated power (mass including support electronics), which in space would be available nearly continuously. That gives a energy payback time of about 2.5 years. With solar power designs more suited to space use, I would be very surprised if that couldn’t be reduced to weeks.
This is probably the worst-case comparison for space solar, since it assumes you’re just going to pack a bunch of terrestrial systems onto a rocket and shoot them into space, where they will (just like terrestrial systems) only work at a fraction of capacity due to clouds, bad sun angles, getting dirty, and night-time.
In practice they would provide a lot more power per unit mass by at least one order of magnitude and possibly two. Mirrors in space can be relatively flimsy thin things and still work since they don’t need to withstand winds and other loads, giving relatively lightweight concentrated solar power options at much lower masses than terrestrial systems.
The conclusion is the same though: space launched solar is still not worth it for us now. It could be in the future or with some alternative history.
Can you elaborate more on that? It was clear to me that in space PV in space can give much more energy/mass than in Earth, but close to 2 orders of magnitudes is huge! Is this “only” due to temperatures losses + constantly running at full capacity + concentration?
Almost all of the mass of solar panels on Earth is structural strength to deal with various types of weather (mostly wind). That alone would increase power per unit mass by a factor of 5-10, though some of that would be eaten by beamed power equipment that isn’t necessary on Earth.
Permanent cloudless daylight with the light coming from an essentially fixed direction increases average power by a factor of about 4-6, while not affecting mass.
Using thin-film mirrors for concentration could enable even more power for given mass.
Ahhh! What I was missing is the structure part. I was thinking in E/surface not on E/mass. Thanks.
I am not really sure about that. There is not only a huge money cost but also a huge energy cost when sending something into orbit, would the panels even make back the fuel spent to send them? Even if the rocket hardware is reused 100% with no serious maintenance costs (reusing costs more fuel) would the panel even make back that fuel energy alone? I did not do the math but maybe not even that. If we could put them in orbit with a space elevator almost for free the tune would be way different though.
Oh yes, there is no question at all that they would make back the fuel energy cost. In money terms the fuel is a tiny fraction of launch costs (less than 1%). In fuel energy terms it costs about 400 MJ/kg to get payload into orbit via Falcon-9.
With fairly standard terrestrial designs you can get about 5 W/kg rated power (mass including support electronics), which in space would be available nearly continuously. That gives a energy payback time of about 2.5 years. With solar power designs more suited to space use, I would be very surprised if that couldn’t be reduced to weeks.