Penny a kWh

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Penny a kWh electricity

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

This has to do with price elasticity of demand.

Some 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 cents 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.
  • 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 from power sales (the power satellites could also be sold) at 4 cents per kWh 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. This would raise the effective amount of oil since current extraction/upgrades burn one barrel for each 3 produced.

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

Cost of Space Based Solar Power

The rough cost of energy from pace is based on:

1. 8000 hr/year (90% on time)

2. payback of capital in ten years (ten percent of cost per year in revenue).

So the entire production cost is to be paid by 80,000 hours of revenue.

A power sat production cost per kW is $/kW for the rectenna plus $/kW cost for the power sat parts, plus kg/kW x $/kg to GEO

This ignores production labor even at GEO. If the construction rate is a million kW/day, a labor cost of a million dollars a day is only a dollar/kW. At around $1000 per installed kW, that's about 0.1%

The key here is that kg/kW is just as important as lift cost.

Energy cost (in cents/kWh) would be production cost in $/kW divided by 800.

To get penny a kWh, the production cost of the power satellite cannot be more then $800 per installed kW. (Compare with current estimates for nuclear power of about $8000 per kW.) The target here will be 2 cents per kWh with off peak power eventually being sold for 1 cent per kWh to make hydrogen.

(Because power satellites at $1600/kg and no fuel cost are the least expensive source of power, they will eventually be built out to peak demand. The difference between peak demand and baseload will be fed to hydrogen electrolizers.)

The rectenna cost estimate is $200/kW based on inverters costing $60/kW (same as PC power supplies which have the same parts). We can spend $1400 per kW on parts, lifting them to GEO and assembly.

Allocating $200/kW to the rectenna, $900/kW ($450/kW before 50% transmission loss) to buying power sat parts and $500/kW for lift to GEO, then the lift cost cannot exceed $100/kg for 5kg/kW power sats.

Thermal alternative to PV

Most power satellite work has assumed PV cells because they are already well proved in space. Having no moving parts helps for communication satellite that cannot be serviced at all. For 10 GW scale power satellites thermal turbines may be attractive. They would probably need to be installed in counter rotating pairs to minimize angular momentum problems. The Excel file here [radiator_temperature_extended.xls‎] shows minimum mass at ~130 deg C.

Next: Hundred dollars a kg (cost to GEO)