[ExI] More ranting on power sats

[Eugen Leitl]

On Wed, Aug 15, 2012 at 01:24:47PM -0400, John Clark wrote:
> On Tue, Aug 14, 2012 at 2:19 PM, Keith Henson <hkeithhenson at gmail.com>wrote:
> 
> > It does as well per area as PV does in the brightest part of a clear day,
> > but a rectenna produces that level of power virtually all the time.
> >
> 
> Considering the vast effort involved I'd really expect it to do better than
> that. One of the main problems with solar is the vast amount of land

The vast amount of land already covered with roofs, buildings and other
structures, you mean?

> required due to the dilute nature of sunlight, and power satellites do not

You say dilute, I say Goldilocks. Houses can be self-powering, and no
roof has melted down into a puddle of corium yet.

> solve that problem.

That's because that is not the problem they're trying to solve. 
The problem they're trying to power PW scale cultures.
 
> 
> > > The worst rain storm on record was analyzed back in the 70s for power
> > sats.  It does take some energy out of the beam, but it's a relatively
> > small fraction.  I don't remember the exact numbers but it is nothing to
> > worry about.
> >
> 
> It depends on the microwave frequency, below about 4 GHZ rain doesn't
> hinder communication satellites much but we're talking about power
> satellites; if the power of the signal from a communications satellite
> suddenly drops in half it's hardly noticed,  but if the output from a big
> power plant suddenly drops in half it would cause havoc.  And for
> frequencies higher than 4 GHZ or so rain starts to cause problems even for
> communication.
> 
> >>> and if you have a grid, then we can "cross the beams" to keep the grid
> >>> fed from power sats out of the shadow.
> >>>
> >>
> >> > > This problem like all problems is solvable, but it's going to take
> >> even more money
> >>
> >
> > > This trick has no cost.
> >
> 
> Directional antennas that are adjustable cost more than the non-adjustable
> type, and 2 power satellites cost more than one.
> 
> > Do you have a number on how long the thorium will last?  I be it isn't
> > very long if you try to use it as the primary energy source.
> >
> 
> In the Earth's crust Thorium is about 4 times as abundant as Uranium which
> makes it about as common as lead. And today all commercial Uranium reactors
> are non-breeders, that means they only use U235 which is about one part in
> 143 of natural uranium, the remainder being U238 which can be used to breed
> Plutonium for power but for several very good reasons it usually isn't, and
> so nearly all of natural Uranium is just dead weight. By contrast natural
> Thorium comes in only one isotope and reactors burn up 100% of it,  not
> just .7% of the Uranium as in existing reactors; so the human race can
> expect to get 4*143= 572 times as much energy from Thorium as they get from
> Uranium.  And Uranium reactors have many problems but acute uranium
> shortage is not near the top of the list.
> 
>   John K Clark

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