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No, it doesn't need to be--that's only one potential architecture.
The benefit of GEO is that you can get continuous service from a
single satellite, whereas lower altitudes require a constellation of
them. However, the latter would be easier to demonstrate with a
part-time system, which would be a proof of concept for the whole
constellation.

Powersats in LEO to me doesn't seem to be much better than just building
the thing on the ground. At night, a powersat visible from the ground
will probably also be in the Earth's shadow. So why bother putting it
in orbit? Getting something that big in orbit is way too expensive
anyway, and if the thing is built on the ground, you can skip the
conversion of the power to microwaves, and skip the rectennas. That
would cut losses by something like 40% or more. And doing repairs and so
on would be way easier with it on the ground. Of course it would only
generate power during the daytime, but that's when electricity usage
peaks anyway. And of course we'll need other power plants at night, but
we'd want multiple methods of power generation anyway. Windmills,
nukes, and so on.

On Tue, 05 Jun 2007 19:47:18 GMT, in a place far, far away, robert
casey made the phosphor on my monitor glow in
such a way as to indicate that:



No, it doesn't need to be--that's only one potential architecture.
The benefit of GEO is that you can get continuous service from a
single satellite, whereas lower altitudes require a constellation of
them. However, the latter would be easier to demonstrate with a
part-time system, which would be a proof of concept for the whole
constellation.

Powersats in LEO to me doesn't seem to be much better than just building
the thing on the ground.

I didn't say LEO. Just an orbit much closer to earth to reduce the
size of the transmitting antenna. Satellites that are eclipsed would
be supplemented by others from the constellation, with split beams.

(Henry Spencer) wrote:

In article ,
Paul F. Dietz wrote:
And to the degree that electricity can better become a substitute for
petroleum (for example, by improvements in batteries for vehicles)
then SSP isn't needed, or even particularly helpful. Huge numbers of
PHEVs could be charged on the US power grid with existing capacity
(mostly during off-peak times) before they would require new capacity
additions.

With one small caveat: some of the generating capacity now used only for
peak loads, which would have to run 24x7 if some new big off-peak energy
use appeared, is not suited to providing base-load power -- too expensive,
too polluting, etc. (Some utilities use older plants, or inefficient but
low-capital-cost technologies like gas turbines, to help meet peak loads.)
It would have to be replaced with new base-load generating capacity in
this scenario.

Two small caveats: some of the power currently sold East-to-West (and
vice versa) will instead be used locally during off peak hours.

That's a detail, though; Paul is still basically correct.

Agreed.

D.
--
Touch-twice life. Eat. Drink. Laugh.

-Resolved: To be more temperate in my postings.
Oct 5th, 2004 JDL

Re : Space Solar Panels replacing petrol in cars.

People forget that in the USA, a signififant percentage of electricity
is produced with polluting coal. This is a major source of pollution for
the planet. So if you can get alternative sources of electricity, it
will alleviate this very nasty source of pollution. It may not fir the
car problem, it helps fix another problem.

On Jun 5, 10:47 pm, robert casey wrote:
No, it doesn't need to be--that's only one potential architecture.
The benefit of GEO is that you can get continuous service from a
single satellite, whereas lower altitudes require a constellation of
them. However, the latter would be easier to demonstrate with a
part-time system, which would be a proof of concept for the whole
constellation.

Powersats in LEO to me doesn't seem to be much better than just building
the thing on the ground. At night, a powersat visible from the ground
will probably also be in the Earth's shadow.

In shadow only twice a year during equinoxes, and only for an hour or
so per day.

So why bother putting it in orbit? Getting something that big in orbit is way too expensive
anyway, and if the thing is built on the ground, you can skip the
conversion of the power to microwaves, and skip the rectennas. That
would cut losses by something like 40% or more. And doing repairs and so
on would be way easier with it on the ground. Of course it would only
generate power during the daytime, but that's when electricity usage
peaks anyway. And of course we'll need other power plants at night, but
we'd want multiple methods of power generation anyway. Windmills,
nukes, and so on.

Envisioned power loss (due to atm.) about 5%.
Advantages:
1. roughly double efficiency - no atm.;
2. +30% approx. depends on location of equivalent Earth based array -
no weather;
3. double that again for 24/7 operation - no night life :-))

Disadvantage: requires *really* cheap launches. IIRC, $100/kg would
just about do it, for Moon produced arrays.

IMHO, nukes are the only reasonable way to cut CO2. They would replace
the worst source of pollution - coal. Incidentally, nukes would also
*diminish* radioactive waste released into the atm.
FYI http://www.ornl.gov/info/ornlreview/...t/colmain.html

In article k.net,
robert casey wrote:

Powersats in LEO to me doesn't seem to be much better than just building
the thing on the ground.

That's OK; this is no doubt just because you haven't looked into them
very deeply.

At night, a powersat visible from the ground
will probably also be in the Earth's shadow.

Incorrect. A satellite in GEO is in sunlight 24 hours a day, except for
a brief eclipse for about 20 minutes (IIRC) twice a year.

and if the thing is built on the ground, you can skip the
conversion of the power to microwaves, and skip the rectennas. That
would cut losses by something like 40% or more.

Wrong again. Conversion to microwaves and back is extremely efficient
-- around 90% is reasonable to expect.

Of course it would only generate power during the daytime, but that's
when electricity usage peaks anyway.

We need to serve baseline power, not just peak power. And as Henry
points out, the daytime peaks may well smooth out as we start
substituting other energy sources for transportation. (Cars will be
charged and synthetic fuels will be generated whenever power is
cheapest.)

Best,
- Joe

In article .com,
Hyper wrote:

IMHO, nukes are the only reasonable way to cut CO2. They would replace
the worst source of pollution - coal. Incidentally, nukes would also
*diminish* radioactive waste released into the atm.
FYI http://www.ornl.gov/info/ornlreview/...t/colmain.html

Unless, of course, Bussard's approach to fusion can be made to work. It
certainly looks promising from the preliminary data -- it's appalling
that it's not getting a drop of funding.

http://www.strout.net/info/science/polywell/

(Incidentally, I've donated $50 to this research; if you see any merit
in it, I encourage you to donate whatever you can as well. Waiting for
government or angels to step in doesn't seem to be working.)

Best,
- Joe

:: Powersats in LEO to me doesn't seem to be much better than just
:: building the thing on the ground. At night, a powersat visible from
:: the ground will probably also be in the Earth's shadow.

: Joe Strout
: Incorrect. A satellite in GEO is in sunlight 24 hours a day, except
: for a brief eclipse for about 20 minutes (IIRC) twice a year.

OK, but how does what happens to a satellite in GEO make that claim
about LEO incorrect?

Mind you, nobody was proposing a LEO SPS upthread, but if anybody had,
I'd agree there are quite a few problems with the notion.


Wayne Throop http://sheol.org/throopw

In article ,
Joe Strout wrote:

In article k.net,
robert casey wrote:

Powersats in LEO to me doesn't seem to be much better than just building
the thing on the ground.

That's OK; this is no doubt just because you haven't looked into them
very deeply.

At night, a powersat visible from the ground
will probably also be in the Earth's shadow.

Oops -- sorry, you said LEO, and my brain read it as GEO.

You're right, a LEO powersat doesn't make too much sense, though one in
a somewhat higher (even if below GEO) satellite might. That's one of
those continuous engineering trade-offs, that would require running some
real numbers (and detailed other assumptions) to find an optimum.

Best,
- Joe

On Tue, 05 Jun 2007 14:32:08 -0700, in a place far, far away, Hyper
made the phosphor on my monitor glow in such a
way as to indicate that:

On Jun 5, 10:47 pm, robert casey wrote:
No, it doesn't need to be--that's only one potential architecture.
The benefit of GEO is that you can get continuous service from a
single satellite, whereas lower altitudes require a constellation of
them. However, the latter would be easier to demonstrate with a
part-time system, which would be a proof of concept for the whole
constellation.

Powersats in LEO to me doesn't seem to be much better than just building
the thing on the ground. At night, a powersat visible from the ground
will probably also be in the Earth's shadow.

In shadow only twice a year during equinoxes, and only for an hour or
so per day.

That's the case only for GEO. We were talking about LEO.