The issue is power transmission. Wireless transmission has repeatedly been shown to be highly energy intensive and prone to severe loss the further you’re sending it, plus you still have to have a way to pick it up and convert it to electricity at a useful rate on the ground.
Solar irradiance above the atmosphere (i.e., in orbit) is 1360 W/m^2. At ground level, it’s 1120, so a loss of ~18% due to the atmosphere.
If transmission losses plus the massive costs of launch, keeping the panels cool (no conduction/convection in space), and maintenance add up to greater than 18%, it’s more efficient on the ground.
First, the best place for them is GEO. In that orbit, they’re only in the earth’s shadow for small chunks of time throughout the whole year. The extra delta-v to go from LEO to GEO is generally worth it.
Second, never have to worry about cloud cover.
Third, 1120 W/m^2 is an average that changes substantially depending on where and when you’re talking about. The 1360 W/m^2 in GEO is constant.
The issue is power transmission. Wireless transmission has repeatedly been shown to be highly energy intensive and prone to severe loss the further you’re sending it, plus you still have to have a way to pick it up and convert it to electricity at a useful rate on the ground.
Solar irradiance above the atmosphere (i.e., in orbit) is 1360 W/m^2. At ground level, it’s 1120, so a loss of ~18% due to the atmosphere.
If transmission losses plus the massive costs of launch, keeping the panels cool (no conduction/convection in space), and maintenance add up to greater than 18%, it’s more efficient on the ground.
It’s a lot more than that.
First, the best place for them is GEO. In that orbit, they’re only in the earth’s shadow for small chunks of time throughout the whole year. The extra delta-v to go from LEO to GEO is generally worth it.
Second, never have to worry about cloud cover.
Third, 1120 W/m^2 is an average that changes substantially depending on where and when you’re talking about. The 1360 W/m^2 in GEO is constant.
The basic practicality of a microwave-based system was demonstrated in 2023, and it does work. However, they are suspiciously mum about efficiency.
https://www.caltech.edu/about/news/in-a-first-caltechs-space-solar-power-demonstrator-wirelessly-transmits-power-in-space