[ExI] More ranting on power sats
Keith Henson
hkeithhenson at gmail.com
Sun Aug 12 16:16:16 UTC 2012
Shame to put a good rant in only one place. :-) I will try to keep
these down to once a week. This is in response to an article in the
Washington Post by Hansen.
This might have changed recently, but (as far as I know) none of these
people who make noise about anthropological global warming actually
want to do anything about it.
If we were suddenly able to switch to a non-carbon energy source,
people like Hansen would be out of a role. Ideally, a switch should
have a price tag lower than the current cost of energy.
Do people like Hansen ask engineers to design an energy supply at such
a low cost that people will just quit using fossil fuels? Are they
even interested in new low cost energy?
These are not hypothetical questions. Solar energy is as renewable as
you can get, but the way we convert it is expensive because sunlight
is dilute and thus takes huge areas, often as not, located far from
demand. In addition, there is the storage problem.
If you can go into space, where there is no wind or gravity,
structures can be light and last for decades to centuries. How light?
Ground based takes around 500 kg per kW, space about 5 kg/kW, so one
percent. It is well understood how to get the power back via
microwaves and because the sun shines almost full time on that orbit,
there is no need for storage.
The reason this has not already been done is the high cost of getting
500,000 tons per year or more to geosynchronous orbit. The high cost
is due to infrequent flights and small payload fraction. Flying a few
times an hour will get the cost down to around $500/kg but that's too
much for power satellites.
We know that if we could heat hydrogen with external energy the
payload fraction would go up by a factor of about ten and the cost
down by the same factor. Big lasers related to the tiny ones in CD
players can do that.
Propulsion lasers are very expensive, but if you run them full time,
the cost to lift parts to GEO goes down to under $100/kg. At that
price, power satellites cost $1600/kW and for that much capital
investment, the power can be made at 2 cents per kWh.
That's less than half the cost of the next least expensive source of
power and down by a full factor of ten from the projected cost of
ground solar. It's so low, synthetic carbon neutral fuels can be made
for around a dollar a gallon.
The energy payback is a couple of months, and the growth potential is
high enough to displace all fossil fuels in a couple of decade from
the start.
We have to so something about energy or die in famines and resource
wars. The start up cost is probably over $100 B, but that's a deal
considering what it solves.
Know anyone who wants to actually solve the energy problem as opposed
to getting attention by incessantly going on about global warming?
This low cost transport proposal has not been peer reviewed. If any
of you would like to do that, let me know.
The previous iteration can be found here: http://www.theoildrum.com/node/7898
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