Re: SPSs and the candidates

From: Christopher M. Jones (christopher.m.jones_at_gmail.com)
Date: 11/04/04 

Date: Wed, 03 Nov 2004 23:24:06 -0600

Bill Bogen wrote:
> "Christopher M. Jones" <christopher.m.jones@gmail.com> wrote in message news:<AfWdnbdneMrCZhncRVn-ow@comcast.com>...
>>Current energy usage world-wide runs at around 400 EtaJoules
>>per year, or an average of roughly 13 teraWatts continuously.
>>Even at 100% conversion efficiency of the ~1400 W/m^2 of
>>insolation at Earth this corresponds to over 9,000 km^2 of
>>area in solar power systems. This is a lower bound, a more
>>realistic estimate would be at least a factor of 4 larger
>>due to inefficiencies in each step of the process.
>
> So, using a factor of 4, we need 36,000 km^2 of solar panels or of
> mirrors reflecting into heat engines. By an amazing coincidence, this
> is almost exactly the amount of aluminum foil made in Europe in 2003.
> So if we can make 4% as much as that in space (as well as heat engine
> parts, microwave components, etc) using lunar materials, then in 25
> years we could provide all the Earth's current energy needs.

This is not an encouraging statistic. It indicates how
far we have to go not how easy it will be. It indicates
that we need to be able to make solar panels and related
systems nearly as abundantly as we make aluminum foil
today in order for SPS to be feasible with today's, let
alone tomorrow's, energy needs. Worse yet, according to
some we need to make factories in space or on the Moon
which can process local materials and make PV arrays as
cheap and abundantly as we make foil. The last time I
checked PV arrays were just slightly more complex and
costly to manufacture than foil.

>>Even very low estimates of the mass of SPS systems and of the
>>launch costs yield values of tens of thousands of tonnes of
>>material put into orbit at a cost of hundreds of billions
>>of dollars.
>
> "hundred billion dollars" / "ten thousand tonnes" = $10,000/kg
> You consider this to be a "very low estimate of launch costs"? Good
> grief, how would you launch the materials, on the Shuttle? Any person
> seriously considering SPS on a large scale assumes the use of lunar or
> asteroidal material, with much lower launch costs.

My apologies, those estimates are not necessarily
linked. I used slightly more realistic estimates of
the mass to determine launch costs, while keeping
the lower mass estimate. I used a launch cost of
less than $1,000/kg to determine the cost and did not
include development or manufacturing costs. For
what it's worth, the Shuttle's cost is more like $20k/kg
(note: kg vs. lb). The cost of a Soyuz launch is
roughly $5k/kg.

>>This ain't gonna happen overnight.
>
> True. What source of power would?

None. That's the point. SPS is not an instant panacea.
Nothing is an instant panacea for power production.