What's wrong with this idea?

victoriatangoman wrote:

>Usually, when we read of the SPS scenario, there is a SPS and a
>dedicated rectenna farm.
>
>To me, such a scenario negates two of the advantages of GSO, namely
>the wide footprint into which a SPS can beam power and the never
>varying power output of the SPS.
>
Yes, the solar array is fixed power, but the load on the power grid
depends on time of
day, year, and what's on TV.

>To me these limations present three different scenarios for
>increased efficiency. What are the flaws of logic or engineering
>that I may be overlooking in the descriptions below?
>
>1.) A SPS for a city is designed for below peak power rating, and
>the neighboring SPS, which would be offset by perhaps a few
>timezones, can supplement with additional power to meet the peak
>power rating. Necessary premise: Peak power demand will ebb in the
>city providing supplemental power while it is rising in the city in
>need of the power. I also, realize that the microwaves coming in
>from the SPS a few time zones away will be coming in at an acute
>angle, and thus not be as concentrated. And this might also cause
>havoc with issues like restricted airspace.
>
Yes, there's an inverse cosine law on the size of the rectenna on the
ground. As the angle varies from the vertical, the width of the rectenna
has to increase on the ground, to capture the same amount of energy.

The transmitter is much smaller than the receiver, and possibly cheaper.
The idea of moving power from, say, the east coast to the west coast,
would probaly work, but the rectenna would have to be bigger on each
side to compensate for the angles.

For east coast America to west coast, I make it about a 37.5 angle to
the vertical. Therefore the rectennas on the ground end up about 20%
bigger (you might like to check it out yourself, I may have screwed up.)

So all you need to do is switch off one transmitter and turn on the
other and you can supply extra power. I suppose in theory you could
point it just about anywhere, provided you were prepared to wait for the
antenna to swing across and lock in.

>2.) A super-sized SPS, with multiple transmitter arrays, serving
>multiple rectenna farms in a narrow longitudinal band. This could
>provide power balancing between different utilities. Also by
>extending this concept to a larger scale, could a Super-Size SPS
>serve multiple utilities across the hemispherical line, thus
>providing power to summer peak loads while the other hemispehre is
>experiencing winter?
>
Yeah, don't see why not; it looks very doable. The only question is
whether there is enough market south of the equator.

>3.) A transfer of microwave power to and from multiple orbiting SPS
>in order to take power where it is needed. This prevents designing
>SPS capacity for peak power load. Thus, a SPS orbiting above a
>longitude in the night, can beam a portion of its power across
>space, perhaps relayed by other SPSs, to a SPS above a daylight
>longitude.
>
I'm less certain this works so well. Well, it works, but the
transmitters are typically much smaller than the rectenna (actually
according to the equation I've seen the product of their areas is
related to the distance you're sending it.). So you'd end up building
huge rectennas to make this work, and you'd need them to be in space.
That's probably prohibitively expensive in launch costs right now,
although in the long run the costs are probably not an issue at all (in
the context of space settlement).

You could try having multiple repeaters though, that way the antennas
are much smaller... The issue with this is efficiency, as you'd lose
power with each hop, but also, for any significant distance you're
talking kilometer antennas. And the distances from one side of the
earth, the long way is 100,000 km or so if you have multiple hops.