Penny a kWh

Penny a kWh electricity

For 40 years, people have talked about solar power satellites. Based on an entire industry in space, it looks like they could deliver power for a penny a kWh or less. However, the complication of building up the industry and the long lead times are discouraging.

Done via a huge fleet of rockets hauling nearly a million tons a year to geosynchronous orbit, recent studies make a case for 5 cent per kWh, highly dependent on the cost of transportation into space at around $500/kg. The energy in rocket fuel is paid back in 40 days. It's the high cost of aerospace hardware that makes it expensive, not the energy.

A moving cable space elevator gets very close to the minimum energy to lift a kg, 14.6 kWh. The energy payback time is just over a day (30 hours). Alas, we don't have the nanotube cable yet, though progress is being made.

Laser propulsion isn't as well developed as rockets, and does not develop a lot of thrust but it is very efficient on propulsion mass while using a lot of laser power.

If we were willing to build an 8 GW laser (cost estimate $80 billion) we could use it and a low performance "pop up" rocket to 250 miles to push close to a million tons of construction materials out to GEO at a cost well under $100/kg. (The laser takes 15 minutes to accelerate the payload into orbit from a sub orbital trajectory.) The energy pay back is about two weeks.

This allows building power satellites for under $800/kW. The electricity could be sold for a penny a kWh or less and synthetic gasoline from the electricity sold for about a dollar a gallon.

On a crash program, we could be adding upwards of 500 GW of new power per year, in as little as seven years. That would be more than enough to compensate for the fall off in oil. Or as the military study concluded last year: