On Mon, Mar 3, 2014 at 11:00 AM,  Ellen S. <zoo...@hotmail.com>> wrote:

snip

> Solar energy beamed down from outer space? I don't know anything about that.

Try  http://nextbigfuture.com/2013/09/propulsion-lasers-for-large-scale.html

The big objection to solar and other forms of renewable energy is the
cost.  It's 10-20 times what we need for a vibrant economy.  Gail
Tverberg makes a case that is $30-50 dollar a bbl oil.  Over that and
the economy can't grow enough to cover past commitments.  Energy is
fungible if you can afford the conversion cost.  For making synthetic
oil out of CO2, water and electric power, the power has to be in the
1-2 cents per kWh to make oil in that range.

Power satellites will do that _if_ we can get the transport cost to
GEO down to $100/kg.  That's about a hundred fold reduction from the
current price we pay to lift communication satellites to GEO.  It is
also ~100 times more than the minimum energy cost if you had something
like a moving cable space elevator.

Between the Skylon rocket plane and a big propulsion laser, the math
works out that at half a million tons per year or more we can get the
price down that low.

It would be trivial to get humanity off fossil fuels if there was a
less expensive energy source.

So why space?  Five times the sunlight as the best places on earth and
more like 10-20 in cloudy places.  Materials cost, 1% of what it takes
on the ground because no wind and no gravity.  In GEO, the sun shines
99% of the time so there is no need for storage.

Energy payback time?  Under two months.  Time to displace fossil fuels
is a bit over two decades from the start.  "Start" might have happened
last July with the Skylon engine development being funded.

Sounds hopeful?  Would you like to help on the technical issues?  Even
more we need people to spread the idea that there is at least one
solution to the economic, energy, carbon and climate problems.

Keith

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