3 ms·

It's expensive to launch stuff, and it's difficult to get power down from orbit without frying birds or creating a weapon.

lawlessone 8y ago
>without frying birds or creating a weapon. The weapons part would probably be bonus for some..
Johnny555 8y ago
With a large enough collector, you don't fry birds. https://dothemath.ucsd.edu/2012/03/space-based-solar-power/ https://dothemath.ucsd.edu/2012/03/space-based-solar-power/ The recommended transmission strength would be 230 W/m² in the center of the beam. This is about a quarter the strength of full sunlight, and is thought to be a safe level through which aircraft and birds can fly. At this level, our 3.6 km diameter collecting area would generate about 40 GWh of energy in a day, at an assumed reception/conversion efficiency of 70%. By comparison, a flat array of 15%-efficient PV panels occupying the same area in the Mojave Desert would generate about a fourth as much energy averaged over the year
- deftnerd 8y ago
  Does the 30% lost efficiency bleed into the environment as heat energy? While it's not as damaging as greenhouse gases, we should try to avoid adding more heat to our environment if possible. Especially when considering planetary-scale space power production and transmission. I remember reading about a way to radiate heat energy from AC units directly to space. "The panels do this by emitting heat at infrared wavelengths between 8 and 13 micrometers. To these waves, the Earth’s atmosphere is transparent. What’s more, the panels reflect nearly all the sunlight falling on them." [1] Perhaps the same general concept could be used to transmit energy from space to earth while lowering interaction with the atmosphere. [1] https://spectrum.ieee.org/energywise/green-tech/solar/efficient-airconditioning-by-beaming-heat-into-space https://spectrum.ieee.org/energywise/green-tech/solar/effici...
  - tomp 8y ago
    You can probably balance things out a bit. I don't think that "30% efficiency/loss" is the best way to think about this. Instead, think of it as "extra amount of sunlight reaching Earth" (and subtract the extra amount of radiation, which would probably be a second-order effect). If you've a 100m mirror illuminating the night-side of the planet, you'll need a k \* 100m size mirror shading the day-side part... And you'll probably need to calibrate this depending on the region you illuminate/shade as different parts of the Earth reflect/absorb different amounts of sunlight ("efficiency loss" I guess). All in all, a very interesting problem indeed! I can't wait until humanity can "afford" such large-scale geo-engineering.

lawlessone 8y ago

>without frying birds or creating a weapon. The weapons part would probably be bonus for some..

Johnny555 8y ago

With a large enough collector, you don't fry birds. https://dothemath.ucsd.edu/2012/03/space-based-solar-power/ https://dothemath.ucsd.edu/2012/03/space-based-solar-power/ The recommended transmission strength would be 230 W/m² in the center of the beam. This is about a quarter the strength of full sunlight, and is thought to be a safe level through which aircraft and birds can fly. At this level, our 3.6 km diameter collecting area would generate about 40 GWh of energy in a day, at an assumed reception/conversion efficiency of 70%. By comparison, a flat array of 15%-efficient PV panels occupying the same area in the Mojave Desert would generate about a fourth as much energy averaged over the year

deftnerd 8y ago
Does the 30% lost efficiency bleed into the environment as heat energy? While it's not as damaging as greenhouse gases, we should try to avoid adding more heat to our environment if possible. Especially when considering planetary-scale space power production and transmission. I remember reading about a way to radiate heat energy from AC units directly to space. "The panels do this by emitting heat at infrared wavelengths between 8 and 13 micrometers. To these waves, the Earth’s atmosphere is transparent. What’s more, the panels reflect nearly all the sunlight falling on them." [1] Perhaps the same general concept could be used to transmit energy from space to earth while lowering interaction with the atmosphere. [1] https://spectrum.ieee.org/energywise/green-tech/solar/efficient-airconditioning-by-beaming-heat-into-space https://spectrum.ieee.org/energywise/green-tech/solar/effici...
- tomp 8y ago
  You can probably balance things out a bit. I don't think that "30% efficiency/loss" is the best way to think about this. Instead, think of it as "extra amount of sunlight reaching Earth" (and subtract the extra amount of radiation, which would probably be a second-order effect). If you've a 100m mirror illuminating the night-side of the planet, you'll need a k \* 100m size mirror shading the day-side part... And you'll probably need to calibrate this depending on the region you illuminate/shade as different parts of the Earth reflect/absorb different amounts of sunlight ("efficiency loss" I guess). All in all, a very interesting problem indeed! I can't wait until humanity can "afford" such large-scale geo-engineering.