On 11/07/2011 10:41 AM, Sylvia Else wrote:
The Australian Government has, for reasons that have much to do with
politics, and little to do with the environment, decided to throw $Au 10
billion into the bottomless pit that is renewable energy.

Lest it all get turned into yet more solar panels and windfarms, I
invite all comers to submit their plans for orbital power satellites. At
least then we might get some technological advance for our money, even
though I doubt we'd actually see any orbital power.

Sylvia.

How can a SSPS be more efficient than PV on roofs? Also, it will help
the environment - I'm studying sustainability at the moment for a future
career.

PV isn't the only way of generating electricity. Queensland (an
Australian state) is going to get several 250mW solar thermal power
plants - small by coal standards, but it helps. ST (Solar Thermal)
could also be installed on factory and warehouse roofs for power
production (look up SEGS - Solar Electricity Generating System) for
about half the cost per kW of PV (solar cells); ST is just not as pretty
as PV, especially if the PV is BIPV (Building-Integrated Photo Voltaic).

Also, there is TDP (my favourite subject; that I first learned about on
one of the sci.space groups in 2003) that can economically turn
agriculture and forestry waste into liquid fuels for transport; gas for
heating/electricity production and carbon-rich solids (commonly known as
'bio-char') for soil improvement. A TDP plant can pay for itself in
less than three years - with just the sale of oil at $60/bbl - petrol
(gasoline to Americans) would cost about $0.80 per litre compared to the
current price of $1.30ish.

Now, what's the payback period for an SSPS and how many do we need?

How do we economically get the power down to the users on Earth?

What are the environmental risks of getting the power down to the users
on Earth?

Someone a couple of months ago suggested using laser-powered LV's for
payload to LEO - fine, until you try to find the electricity to power
those HUGE lasers! Those three questions above have never been answered
adequately; please try.