Re: Lunar Solar Power Stations vs. The O'Neill Proposal
- From: henry@xxxxxxxxxxxxx (Henry Spencer)
- Date: Mon, 26 Jun 2006 02:10:15 GMT
In article <1njp92p9mfu074f5c4r9ehr52teqh1balp@xxxxxxx>,
Fred J. McCall <fmccall@xxxxxxxxxxxxx> wrote:
:> Total distribution losses in the United States amount to 7.2%...
:Power is often distributed to places near the power plant. So, even if
:your figure is correct, that doesn't demonstrate the efficiency of long
:distance power lines.
But I would be surprised if it doesn't. 'Local' distribution uses
lower voltages (and hence has higher relative I2R loses).
Only for a definition of "relative" that includes "other things being
equal", which they are not. The reason why a lot of local distribution
uses somewhat lower voltages is that distances are short enough that
losses are inherently low and the higher voltages are not required. If
local distribution took a big hit due to low voltages, it would switch to
higher voltages; instead, all the pressure for really high voltages is in
the long-haul work.
Personally,
I'd think it was all the voltage changes (as you distribute) and such
that would be the greatest loss.
There is no fundamental reason for the voltage changes to involve losses;
indeed, if memory serves, large transformers approach 100% efficiency.
:Even so, long haul power lines can lose a third of the power they start
:out with (see Henry Spencer's reply to your post).
I'd like to see a source for his numbers.
Note carefully that I said "I'm told", indicating that I have not checked
the issue out in detail myself. :-) I believe the number is roughly right,
but am not prepared to swear to it.
there are some 80,000 miles of HV transition lines in the US system
and if they were typically that lossy I would expect system losses a
lot higher than 7.2%, given that most power flows over those lines at
one time or another.
Uh, no, most power never goes over the *long-haul* lines that we are
talking about. "High voltage" and "long haul" are not synonymous; high
voltage is used for large-scale local distribution too, since it makes
distribution cheaper and more efficient. Most power is generated quite
close to its customers.
You'd have the same sorts of problems, though. You have to put your
rectennas someplace and you then need to get power from there to the
users (who aren't going to want to live near your rectenna).
There's no particular reason to avoid the neighborhood of a rectenna; it
won't be smoky or noisy, and the microwave exposure will be no worse than
people get now by living near an airport radar. Indeed, the land under
the rectenna will most likely be farmed -- it'll be a large area of crop
land with a sort of chicken-wire awning over it. A lot of major cities do
have suitable areas not that far away.
True, the paranoid and superstitious won't want to live close. If the
land is incorrectly perceived as undesirable, its price will be lower than
similar land equally near the city, and there will be people who will buy.
Mind you, rectenna siting and transmission from rectenna to users *will*
need attention, especially in parts of the world that are more crowded
than North America. Japan is a major potential customer, since they are
entirely dependent on imported fuels and have major pollution problems,
but I'd guess that rectennas there will have to be offshore.
--
spsystems.net is temporarily off the air; | Henry Spencer
mail to henry at zoo.utoronto.ca instead. | henry@xxxxxxxxxxxxx
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