[ExI] Step at a time was economic parable

hkhenson hkhenson at rogers.com
Thu Oct 9 16:13:11 UTC 2008

Why is it so critical to get the lift to GEO for power sat parts down 
under $100/kg?

For a first pass analysis, power plant capital should be repaid in 10 
years by power sales.

The capital cost per kW is rectenna cost plus power sat parts cost 
plus (mass of power sat parts in kg/kW x lift cost in dollars/kg)

The main cost of rectennas is the inverters.  PC power supplies are 
about 1/3 kW and cost around $20.

So a first pass estimate of the rectenna per kW is $60 plus $140 for 
the antenna, poles to hold it up and wiring to collect the power.

Most of the mass of a power sat is the structure to keep it facing 
the sun.  Being agnostic about PV vs rotating machines, we have $$600 
to spend for parts and lift cost.  4kg/kW is fairly close to the 
estimates people have been using.  So if the lift cost is $100.kg, 
$400 is used to get the parts to GEO.  That leaves $200/kW to buy the parts.

At this resolution, a year is considered 8000 hours, 80,000 hours for 
ten years.

So a penny a kWh would generate $800 income over ten years--paying 
for the capital equipment.

It is worth considering what power cost as you raise the lift cost.

For example, at the current cost to GEO of about $20,000/kg, an 
installed kW would cost about $80,000 and the cost per kWh would be a 
dollar to pay this off in ten years.

Zero lift cost only cuts the price of power in half compared to $100/kg.


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