[ExI] pentagon wants orbiting solar power stations

[Eugen Leitl]

On Sun, Oct 14, 2007 at 07:06:29PM -0400, Jordan Hazen wrote:

> Have you watched your PV system's activity during sudden changes in

I don't have one yet -- I'm first exhausting all other easy-ROI options,
such as lighting, wood/coal oven, insulation, power saving. I'm planning a pilot
in a couple of years to run the computers and the LED lighting off
it.

> cloudcover?  Mine will drop to 10% of full-sun production as a heavy

Sounds like monocrystalline cells.

> cloud rolls in, going from net energy export to import within about
> five seconds, and reversing just as quickly as the sun breaks through.

Yeah, you need a buffer. Also, long-term there's no weather nor night
in space.
 
> This extreme variability is fine so long as solar amounts to only a
> small fraction of total grid generation, as it is now.  Spinning

Don't think the grid, think in terms of powering your home with it.
You can buffer local demand spikes by trading with your neighbours,
which is a very local, power microgrid.

> reserves at nearby power plants instantly make up any sudden
> shortfalls, keeping frequency and voltage within spec.  But, there are

What's wrong with DC?

> limits as to how much non-dispatchable generation existing grids can
> accomodate.  Getting beyond about 20% renewables (still room for 5-10x

I agree that current grids are already overloaded with variability
of the renewables. We need to get rid of them. Make the power where
you consume it, buffer slightly, and do conventional large-scale
stuff (which has 2-3 days of thermal inertia, anyway) during the 
night, for time being. 

> growth), or trying to use PV & Wind for baseload generation will
> require very large-scale energy storage-- something better than pumped
> hydro and lead-acid batteries (even today, PbA is still the best

Yes, I'm planning to run my computers off it. I already have everything
on UPS, so that won't be much of a difference. Properly recycled
lead-acid aren't that bad.

> option for off-grid sites, sadly).

A chicken in every pot, a hybrid/EV in every garage.
 
> At least one US utility has been experimenting with large,
> megawatt-sized NaS batteries, deployed to substations for
> peak-shaving.  These could form part of the solution, perhaps
> supplemented by super-cap banks and intellient load shedding, but a
> stable grid will probably always need at least a few large,

I don't see it happening. What I could see happening is that PV
becomes effectively free, and people can afford doing things like
water electrolysis/fuel cell, which are currently not cost effective.

> traditional baseload plants.  In Europe, France's existing fleet of
> nukes might fill this role for a while.  Areas with a lot of existing
> hydro (northwestern US & Canada, Quebec...) may be able to go 100%
> renewable early on.
> 
> > Remember, 1/10000th of terrestrial insolation is enough to
> > keep current humanity in business indefinitely.
> 
> At 100% collection efficiency?  Or the 14% (minus weather effects,

Solar thermal has nearly quantitative efficiency.

> shading, and conversion losses) of current-tech PV?

I presume it's 100% of what hits the bottom of the gravity well,
with weather factored in. But whether it's 0.0001 or 0.0002, that's
not one heck of a difference. 

-- 
Eugen* Leitl <a href="http://leitl.org">leitl</a> http://leitl.org
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