3 ms·

The book's cost estimate is for a satellite in GEO. You get steady power for all but a few hours per year, and 5.4X as much energy from sunlight in 24 hours, co

The book's cost estimate is for a satellite in GEO. You get steady power for all but a few hours per year, and 5.4X as much energy from sunlight in 24 hours, compared to the same flat area of ground. According to the book you get about 50% power loss in transmission. The satellite design uses a large area of mylar (or similar) reflectors, and a smaller area of solar cells collecting concentrated sunlight. Concentrated solar is costlier on Earth because the mirrors need to be a lot sturdier. The ground collector covers a fairly large area but it's wire antenna and cheaper than solar panels. The Falcon Heavy payload to GEO is 41% of its payload to LEO. I assumed a similar cost ratio for my estimate. Starship prices at scale aren't precisely known yet, but low enough that launch would be a relatively small portion of project cost anyway. Large-scale grid storage is still quite expensive. Most "solar+storage" projects do not have enough storage to get through the night; if they did, it would cost significantly more than 5 cents/kWh.

sandworm101 7y ago
Space mirrors beaming sunlight down to earth are far from a new idea. https://www.vice.com/en_us/article/9a3y8d/the-man-who-turned-night-into-day https://www.vice.com/en_us/article/9a3y8d/the-man-who-turned...
- DennisP 7y ago
  I'm not saying they are, I'm just describing what makes this SPS design affordable. But unlike your link, the design is to concentrate sunlight to solar panels in orbit, then beam power to Earth via microwaves.
gnramires 7y ago
Those numbers look very attractive. What was the expected lifetime of the system? Did it take increased deterioration into account from radiation/increased sunpower? What about cooling? (or are they just pricing currently available satellite panel technology?) A big issue with a project like this are unforeseen costs (being a space-based project) and engineering costs (sometimes needs government stimulus). I'm also bothered sometimes those solutions are advertised as panaceas for climate problem; while currently we have mostly a policy problem (clean energy is almost on par with carbon energy, we're just missing key incentives for the new tech and phasing out carbon plants quicker). But indeed looks like a promising avenue of exploration.
- DennisP 7y ago
  I think they figured only 20 years average lifespan, for the reason you mentioned. I don't remember about cooling. They had a pretty detailed cost breakdown. The low cost is only once you have mass production and a large plant. They assume several smaller projects first, which would be quite expensive per kWh and include more R&D cost. Those would have to serve communities with very expensive power, like remote northern communities or military installations. I wouldn't call it a climate panacea since it'll be quite some time before we can do it at scale. In the meantime we should phase out fossil energy as fast as we can with existing technology. But it looks like in 15 or 20 years we'll have a thriving industry in space anyway, and it's possible that by then we'll be running up against the practical limits of wind/solar market penetration. SPS might play an important role then.

sandworm101 7y ago

Space mirrors beaming sunlight down to earth are far from a new idea. https://www.vice.com/en_us/article/9a3y8d/the-man-who-turned-night-into-day https://www.vice.com/en_us/article/9a3y8d/the-man-who-turned...

DennisP 7y ago
I'm not saying they are, I'm just describing what makes this SPS design affordable. But unlike your link, the design is to concentrate sunlight to solar panels in orbit, then beam power to Earth via microwaves.

gnramires 7y ago

Those numbers look very attractive. What was the expected lifetime of the system? Did it take increased deterioration into account from radiation/increased sunpower? What about cooling? (or are they just pricing currently available satellite panel technology?) A big issue with a project like this are unforeseen costs (being a space-based project) and engineering costs (sometimes needs government stimulus). I'm also bothered sometimes those solutions are advertised as panaceas for climate problem; while currently we have mostly a policy problem (clean energy is almost on par with carbon energy, we're just missing key incentives for the new tech and phasing out carbon plants quicker). But indeed looks like a promising avenue of exploration.

DennisP 7y ago
I think they figured only 20 years average lifespan, for the reason you mentioned. I don't remember about cooling. They had a pretty detailed cost breakdown. The low cost is only once you have mass production and a large plant. They assume several smaller projects first, which would be quite expensive per kWh and include more R&D cost. Those would have to serve communities with very expensive power, like remote northern communities or military installations. I wouldn't call it a climate panacea since it'll be quite some time before we can do it at scale. In the meantime we should phase out fossil energy as fast as we can with existing technology. But it looks like in 15 or 20 years we'll have a thriving industry in space anyway, and it's possible that by then we'll be running up against the practical limits of wind/solar market penetration. SPS might play an important role then.