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

[rlk at alum.mit.edu (Robert Krawitz)]

On Fri, 21 Jul 2017 17:59:52 -0400, Richard Pieri wrote:
> On 7/21/2017 4:57 PM, Robert Krawitz wrote:
>> I question your claim that there isn't enough surface area with
>> sufficient solar exposure to power the world.  Your calculations,
>> please?
>
> http://blogs.ucl.ac.uk/energy/2015/05/21/fact-checking-elon-musks-blue-square-how-much-solar-to-power-the-us/
>
> "Fact checking Elon Musk?s Blue Square: How much solar to power the US?"
>
> Problem is -- and the article points this out -- Musk isn't selling
> solar power. He's selling batteries. His numbers ignore the
> inefficiencies of charging that storage. To actually supply the entire
> US, solar power + battery would need to be at least 10 times the area
> that Musk presents. In reality it would be much more than that because
> solar efficiency drops off as you move north and northern states
> generally have much less flat land for solar farms than Texas. As you
> move north into Canada the efficiency of solar PV drops even further.

10x?  Battery charging isn't that inefficient -- 85% for lead-acid
batteries, for example
(http://www.solar-facts.com/batteries/battery-charging.php).

And even if it were, there's plenty of land in the deserts.  We'd need
a lot more transmission infrastructure, but there's still a good bit
of land elsewhere at reasonable latitudes that could be filled with
panels.  It doesn't need especially high efficiency.

> It might work if the world's nations could build enough equatorial solar
> farms to supply the entire world. I don't foresee that happening any
> time soon.
>
>> So you still have the problem of getting it through the atmosphere,
>> and you still have conversion loss.  How do you propose to get it
>> through the atmosphere without the same kinds of losses (if not more)
>> than ground-based solar power?  Since land area is a concern you
>
> I don't care about that because space-based solar generation capacity is
> at least an order of magnitude greater than equatorial ground-based
> solar. Transmission and storage losses become acceptable when you have
> that much of a potential surplus.

That's the least of the problems.  You have to keep it in orbit, the
beam has to keep station (that kind of concentrated beam had better
not leak), and a geosync orbit is still eclipsed part of the time.

> Yes, SBSP has problems. I wrote as much. And they've been well-documented.

Care to discuss what you see as the problems and how to go about
addressing them?
-- 
Robert Krawitz                                     <rlk at alum.mit.edu>

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