[ExI] pentagon wants orbiting solar power stations

Gary Miller aiguy at comcast.net
Sun Oct 14 23:54:45 UTC 2007


-----Original Message-----
From: extropy-chat-bounces at lists.extropy.org
[mailto:extropy-chat-bounces at lists.extropy.org] On Behalf Of Jordan Hazen
Sent: Sunday, October 14, 2007 7:06 PM
To: ExI chat list
Subject: Re: [ExI] pentagon wants orbiting solar power stations

On Sun, Oct 14, 2007 at 10:19:00PM +0200, Eugen Leitl wrote:
> I'm using fusion right now. It's called PV and solar.

Have you watched your PV system's activity during sudden changes in
cloudcover?  Mine will drop to 10% of full-sun production as a heavy cloud
rolls in, going from net energy export to import within about five seconds,
and reversing just as quickly as the sun breaks through.

This extreme variability is fine so long as solar amounts to only a small
fraction of total grid generation, as it is now.  Spinning reserves at
nearby power plants instantly make up any sudden shortfalls, keeping
frequency and voltage within spec.  But, there are limits as to how much
non-dispatchable generation existing grids can accomodate.  Getting beyond
about 20% renewables (still room for 5-10x 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 option for off-grid sites, sadly).

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, 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

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

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