[Discuss] Eclipses Re: Great talks last night, however...

[richard.pieri at gmail.com (Richard Pieri)]

> OK, so here you're saying that instead of a <10% charge/discharge
> efficiency, batteries actually have a 75%-80% charge/discharge efficiency?

No. I'm saying that chemical batteries have *at best* a charge
efficiency of around 75-80% in the real world.


> Agreed!  And Utah, and Arizona, and New Mexico, and large parts of
> Colorado, Wyoming, Idaho, Oregon, and Washington by your map.  And don't
> forget Great Plains states like Texas, Montana, North Dakota, South
> Dakota... hey, I think we're over 0.15%!

There are three problems that I would consider breakers for these regions:

First, you just described the heart of Tornado Alley.

Second, you can't charge Li-ion batteries when they are below freezing
(0C) which makes much of these areas useless for Musk's storage systems
for significant portions of the year.

And third, high temperatures (above about 25C) reduces efficiency, and
it causes batteries to wear out faster than their published ratings
which means you'll be replacing them that much more frequently if you
set up your stations in the non-freezing areas.


> Right - as in my prior email, when you do the math it comes out to a factor
> of pi (and 24/pi is 7.64 hours, within the range you give).

No. It's significantly more than that because a geostationary station is
always at "noon" when it's exposed to the sun while a ground station's
noon is only a fraction of it's exposure period.


> FWIW, on that last non-technical bit, I and I wager many others on this
> mailing list see very many places in all the named locales which have good
> potential for solar.  And that's one of the great things about solar power:

Maybe good on small scales like homes and offices. Not so good for large
scale like replacing global dependence on fossil fuels.

-- 
Rich P.