[ExI] More ranting on power sats

[John Clark]

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
required due to the dilute nature of sunlight, and power satellites do not
solve that problem.


> > 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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