Penny a kWh

Penny a kWh electricity

Why try to get space based solar power (SBSP) down to a penny a kWh.

http://en.wikipedia.org/wiki/Price_elasticity_of_demand

For points on the curve:

At a dollar a kWh, the demand is near zero, a small number of military camps that would draw a few MW.

At ten cent's a kWh, SBSP could pick up Hawaii's electrical demand of a GW or two except that SBSP power doesn't easily come in small blocks.

For the rest of this analysis see http://www.coal2nuclear.com/energy_overviews.htm (and ignoring the small difference between a Quad and an EJ)

At four cents SBSP gets most of the electrical power of the US, about 400 GW plus the rest of the world for another 1600 GW. (Half average price for power. Distributing electricity costs too.) Building 2000 GW (four hundred 5 GW power sats) takes 4-5 years. Gross income at 4 cents would be would be 2,000 GW x 4 x $80 M/yr/GW or $640 B a year, though some of this would have to be sold for less as off peak power.

In the early years, extra rectennas will allow a premium for switching blocks of peaking power around. Later North American off peak power in excess of base load can be switched to Canada to make hydrogen to upgrade tar sands oil.

As the cost of power declines to a penny a kW, space based power picks up the entire oil and gas markets. The only source that competes is installed hydro.

Cost of power sats

Penny a kWh power sells for $80/kW/year. Using a simple payoff in ten years, that requires building power sats for $800 a kW or less. The rectenna estimate is $100-200/kW based on inverters costing $60/kW (same as PC power suppies). We can spend $600-700 per kW on parts, lifting them to GEO and assembly.

If you assume 2kg/kW power sats, then we can spend $300-350 a kg to buy parts, lift them to GEO and install them. At 4kg per kW, (the upper end of the power sat mass range) we can spend $175 per kg for parts and transport. Assuming 4kg/kw $75 for parts (perhaps solar cells) and installation. That leaves $100/kg for transport.

Four hundred GW of power sats requires 800,000 tons per year lifted to GEO. At least we have economy of scale.

Extra terrestrial resources are a better idea, but there isn't time to develop the space industry to tap them. The economic effects (including famines) of the developing energy crisis are so bad that production of SBSP needs to come on line by 2015 to avoid economic collapse. I expect ET resources be exploited by 2025 with this much activity in space.

This works out to lifting 100 tons per hour. The choices examined here are among rockets, lasers or some combination of them.

Synthetic fuels take 2500 GW for the US and 10,000 GW for the rest of the world. (50% conversion efficiency.)

Coal fired plants (particularly mine mouth plants near an existing crude oil pipeline) could be converted from making power to using power to convert coal and water to syngas (an endothermic reaction). The syngas would be converted to synthetic crude oil by the Fischer-Tropsch process and sent to refineries. Municipal waste (supplemented with coal for a better water balance) would also be sources of syngas. This technology is fairly well developed. See http://www.plascoenergygroup.com/. Eventually biomass or even air could be used as a source of carbon for liquid fuels.

Replacing natural gas and making hydrogen takes 3500 GW. (Some gas already displaced from being used to generate electricity)

18,000 GW at 500 GW a year takes 36 years to build. Gross income would be 18,000 x $80 M/yr/GW, about $1,440 B a year.

It may be desirable to build power sats quicker and supplement oil faster, particularly as the energy demand picks up in China and India. There are massive economic multipliers that flow from inexpensive energy, for example desalinated water in amounts large and cheap enough to use for irrigation largely solves the food production problems.

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.

http://htyp.org/Dollar_a_gallon_gasoline

http://htyp.org/Penny_a_kW

http://htyp.org/Hundred_dollars_a_kg