The price per KW of SPS

Dear B,

The following old posting from Usenet addresses more of the quesitons
and points you raise
so I am cross-posting it here.

power
satellite)
Date: Sat, 08 Nov 1997 22:14:06 GMT

>: With SPS', on the other hand, the technology is well in hand. We have the solar
>: cells and the beaming technology, and they have been well tested over more
>: than a decade. The primary question of one of economics.
>
>: Abou 5 years ago, at a Space Frontier Federation conference, a paper was
>: presented by a power company showing an analysis of the profitibility of small
>: SPS systems, 10 MW or so. The analysis showed that they could be economically
>: viable, with power costs on the order of that produced by nuclear reactors -
>: and that without major advances in launch technology.
>
>Not every one is convinced they are economically viable. At the NSS Space
>Summit, Robert Zubrin said that he thought the ideas of Gerard O'Neill
>were absurd, since space solar power presently cost a thousand times more
>than any other type.
>
>Karen

Karen, my guess is solar power satellites could compete with
alternate sources of energy on cost, if the US followed the proper
development path.

Found at: http://pages.nyu.edu/~potter/thin-film-sps.html

"The SPS [Solar Power Satellite] designs mentioned above [NASA/DOE
baseline studies] have masses of about 50,000 metric
tons and generate 5 GW (gigawatts, or thousands of megawatts) of
electricity. Recently, therefore, another strategy for reducing SPS
launch costs has been considered. Work at the NASA Lewis Research
Center has shown that it may be possible to use thin-film solar cells
deposited on a lightweight substrate along with solid state microwave
transmitters. Since the entire area of the substrate can be covered
with microwave transmitters as well as solar cells, large effective
transmitting antenna diameters become feasible. Due to the physics of
power beaming, the larger the transmitting antenna, the less the
microwave power beam will spread as it reaches the Earth. Since the
rectifying antenna (rectenna) at the Earth's surface can now be made
correspondingly smaller, the SPS need not supply as much power as a
conventional SPS in order to be economical. (Indeed, it ought not to
supply as much power, or else the microwave beam will become too
intense.) With smaller SPS's having a lower mass per kilowatt of power
generated, the system becomes easier to build and finance.

Current research at New York University, supported by SSI [Space
Studies Institute], aims to achieve the best of both approaches to
launch cost reduction by using thin films and lightweight substrates
built from lunar materials. The first step in the study was to
consider two lightweight SPS designs suggested by Geoffrey Landis and
Ronald Cull of the NASA Lewis Research Center: the "bicycle wheel"and
the "inflatable sphere."

"A bicycle wheel SPS using thin-film technology will have a diameter
of just over 4 kilometers for a power beam frequency of 2.45 gigaherz
(this is the frequency of the NASA/DoE reference design). It will
supply about 450 megawatts of power to consumers. The mass of the
solar cell/transmitter array (including the substrate, but not the
support structure) is just over 200 metric tons if Kapton is used for
the substrate (terrestrial materials), and just under 800 tons if
steel foil is used (lunar materials). The effect of increasing the
frequency was also considered. A 10 GHz power beam yields a bicycle
wheel SPS that has half the diameter, and thus one-fourth of the array
mass and power level as the 2.45 GHz design; i.e., roughly 2 km, 50
tons (terrestrial) or 190 tons (lunar), and 110 MW. A bicycle wheel
with a mirror, or an inflatable sphere will be 8.5% smaller in
diameter and supply 19% more power than a conventional bicycle wheel,
due to th e elimination of the tracking loss. Higher frequencies will
yield even smaller, more easily constructed SPS's, but the amount of
power for their size will be lower, since higher frequencies are
subject to rain and air attenuation, and solid state microwave
transmitters are less efficient at higher frequencies.

Using thin-film technology, an SPS in low Earth orbit may be light
enough to be launched by a single Space Shuttle mission. For a bicycle
wheel SPS orbiting at an altitude of 1200 kilometers, beaming power at
a frequency of 10 GHz, the diameter would be 340 meters, the power
available to consumers would be 3 MW, and the array mass would be an
amazingly low 1430 kilograms (though the support structure would
increase the mass). The full capacity of such an SPS can be exploited
if a series of SPS's and equatorial rectennas are spaced such as to
enable a given rectenna to lock onto the next SPS after the previous
one has disappeared from view. The previous SPS would then lock onto
another rectenna, further east."

Two other good links:

http://pages.nyu.edu/~potter/sps.html

http://web.mit.edu/techreview/www/articles/oct97/hoffert.html

Now, let's compare the cost of construction of three nuclear
powerplants with using thin-film solar power satellites. As an
example, I believe the Tennessee Valley Authority at one time planned
on costructing (now cancelled) three nuclear powerplants at a cost of
$9 billion and each powerplant was rated at about 800 Megawatts output
or 2,400 MW total.

If we wanted to supply 2,400 megawatts using thin-film solar power
satellites, what would it cost? Let's use the 10 GHz bicycle wheel
SPS with a mass of 50 tons and an output of 110 MW, which means we
need to put 22 thin-film SPS in geosynchronous orbit (GEO) to equal
the output of the three nuclear powerplants.

We don't have a launch vehicle capable of putting 50 tons in GEO in
one launch so we need to develop one. Estimates for a shuttle-derived
heavy-lift vehicle (Shuttle-C) of this capacity are around $3 billion
in development costs, and George H estimates his Big Dumb Booster
(BDB) at about the same development cost.

George thinks he can launch his BDB for about $50 million per launch
and I think a Shuttle-C can be launched for about the same, so I'll
use $50 million as the launch cost for each SPS.

Heavy-lift vehicle development= $3 billion

Cost to launch 22 SPS= $1.1 billion

Now, if the SPS materials costs, ground facilities and receiving
antenna costs are around $5 billion, then thin-film SPS look superior
to nuclear powerplants, especially when you consider that the costs of
nuclear cleanup have not been calculated into the cost comparison,
and, for the future, the next 22 SPS put in orbit will not incur the
$3 billion development cost for the heavy-lift launch vehicle since
it's already developed.

There's no doubt we can build a heavy-lift vehicle to perform this
task. All it takes is a small addition to space policy authorizing a
heavy-lift vehicle. In fact, NASA seems to be working fairly steadily
towards that goal right now, in conjuction with manned Mars missions.

The only questions I see are the state of the thin-film technology and
that would seem to be easily surmountable if it became US government
policy to get serious about SPS. Maybe Geoffrey Landis can bring us
up to date on the status of developments in this area (the reports I
excerpted above were done in 1994).

China is currently building a dam across the Yangtze River that will
inundate and desecrate some of the most beautful and historic places
on Earth and will drown thousands of archeological sites, not to
mention dislocating 1.2 million Chinese people and thousands of acres
of farmland. This dam will produce18,000 megawatts of electricity and
will cost about $25 billion.

We could launch 166 thin-film SPS into orbit for $8.25 billion in
launch costs (sounds like a good project for USA:) and these 166 SPS
would supply as much power as the Yangtze dam; without the ecolgical
and social consequences.

I think Solar Power Satellites deserve another, serious look, Now.
Especially now. We're talking TRILLIONS of dollars in future power
production revenues, and we're talking about the very survival of many
species on Earth and the quality of life of the rest. The solution
seems to be right before our eyes, and within our grasp.

Tom Abbott