# [ExI] Thoughts on Space based solar power (alternatives)

Paul D. Fernhout pdfernhout at kurtz-fernhout.com
Sun Nov 23 00:53:22 UTC 2008

```CORRECTION: Just for the record, this section below contains a mathematical
decimal point shift error -- I thought somehow it was a little too good to
be true. :-) It doesn't change my overall point though.

I  calculated "three hundred thousand square miles is devoted to roads" when
that should be "thirty thousand square miles" (about, using the rounded 1%
figure of about three million total square miles in the USA). In turn that
means that roadways *only* :-) provide about ten times the area we need to
produce all our power in the USA from photovoltaics, not one hundred times
as I had written. A hazard of staying up too late, sorry. In turn, the USA
would have to cover about 50% of US roadways to power the planet (perhaps
making liquid fuels and exporting it via tankers? :-)

That amount is still only 0.1% of the total USA land area.

Other related calculations:
http://www.naturestudy.org/
"If the entire state of Arizona were covered by PV facilities, enough
electricity would be produced for 110 billion people domestic electrical
use, or the equivalent of the number of people on 18 Earths! We could invite
17 other planets to come and buy our electrical energy. ... Why isn’t the
United States pursuing this kind of energy production? It a good question,
for which I have struggled to find answers. Environmental economists only
tell me that the conventional wisdom is that solar will never be more than a
minor player in the energy game. Is it just a mind-set that is holding us
back? ..."

Anyway, while the scale of the energy problem is use, so is the scale of the
benefits of doing something about it, and so is the scale of the country
itself and all the resources 300 million people in the USA can do (let alone
the rest of the world). And that potential is so huge, even a slipped
decimal point or two either way still shows it.

--Paul Fernhout

Paul D. Fernhout wrote:
> The area taken up by roadways is enough to power those systems by sunlight.
> From:
>   http://www.vtpi.org/tca/tca0507.pdf
>  "The table below shows one estimate of the total amount of land devoted
> to roads. It indicates that in the U.S. more than 13 thousand square
> miles of land is paved for roads (about 0.4% of continental U.S.), and
> more than 20 thousand square miles is devoted to road rights of way
> (about 0.7% of continental U.S.)."
>
> So, I'll be sloppy here and say 1% to make my math easier after staying
> up all night to work on this. :-) From:
>   http://quickfacts.census.gov/qfd/states/00000.html
> "Land area, 2000 (square miles)     3,537,438.44"
>
> USA.
>
> From:
> http://dotearth.blogs.nytimes.com/2008/08/14/solar-panels-by-the-square-mile-in-california/
>
> "Matthew Wald has just written a news article showing the power of a
> guaranteed market to bring about large-scale construction of energy
> technologies that currently cannot compete with the status quo. Two
> photovoltaic power plants, in essence, are going to be built in
> California, covering a total of 12.5 square miles and amounting to 800
> megawatts of generating capacity (although remember that the peak is
> only hit for a small portion of the day)."
>
> Divide by ten for the peak effect to get an average. So, that's about
> 1000 megawatts (a gigawatt) per square mile for a currently installable
> installation. So, by putting solar installations over all the roads and
> right of ways in the USA, that would produce about three hundred
> thousand gigawatts of power continuously. That is about three hundred
> terrawatts.
>
> Here it says:
>  http://en.wikipedia.org/wiki/Energy_use_in_the_United_States
> "The United States is the largest energy consumer in terms of total use,
> using 100 quadrillion BTU (105 exajoules, or 29000 TWh) in 2005,
> equivalent to an (average) consumption rate of 3.3 TW."
>
> So, we have, just from roadways, one hundred times as much land area as
> we need to be all solar. Sure it's a big task, but it's a big country.
>   http://apolloalliance.org/
>
> And I'm not even considering that something like 1% or so of the USA (I
> forget the exact figure) is also already devoted to energy production
> and fossil fuel mining and so on... :-)
>
> So then the argument will devolve into discussing batteries and other
> storage systems. But would anyone who proposes strong nanotech also then
> suggest we can't make a better battery if we try? We either get good at
> making things or we don't. And we have hundreds of years of coal to last
> us until then (not that I think we should burn anymore of it than we
> have to, for the pollution costs).
>
> Manufacturing is harder, but still possible, to figure out all the
> rooftop area. But the roadways can produce 100X what we need, so let's
> just use 1% of them for everything. In fact, if we use only 5% or so of
> the USA roadways, and had a superconducting grid, we can power the
> *planet*. Isn't sustainable energy production worth devoting at least a
> small fraction of the land we devote to transportation?
>
> However, as I said originally, maintaining a grid is expensive, so local
> solar will drive out the grid eventually.
>
> From:
>   http://en.wikipedia.org/wiki/World_energy_resources_and_consumption
> "In 2005, total worldwide energy consumption was 500 EJ (= 5 x 1020 J)
> (or 138,900 TWh) with 86.5% derived from the combustion of fossil fuels,
> although there is at least 10% uncertainty in that figure.[1] This is
> equivalent to an average energy consumption rate of 15 TW (= 1.5 x 1013
> W). ... . For the whole Earth, with a cross section of 127,400,000 km²,
> the total energy rate is 1.740×1017 W, plus or minus 3.5%. This 174 PW
> is the total rate of solar energy received by the planet; about half, 89
> PW, reaches the earth's surface."
>
> So, humanity uses 15TW (much as heat) and the sun provides 174,000TW, or
> about 10,000 times what we use now. We have to be *really* bad engineers
> if we can't make that work, even if our energy needs go up by a factor
> of ten. But chances are they won't any time soon.
>
> Maybe I made a mistake somewhere and missed a decimal or two, but over
> and over you can find people saying similar things -- there is plenty of
> energy producing potential from renewables.
>
> And my point is mainly that millions of people are working right now
> towards that end. So, regardless of whether solar space satellites go
> up, we will see enormous progress towards renewables. Even Google is
> putting a lot of money into it:
> "Clean and affordable energy is a growing need for our company, so we’re
> excited about launching RE<C, a strategic initiative whose mission is to
> develop electricity from renewable sources cheaper than electricity
> produced
> from coal. Initially, this project to create renewable energy cheaper than
> coal will focus on advanced solar thermal power, wind power technologies,
> and enhanced geothermal systems – but we’ll explore other potential
> breakthrough technologies too."
>
> And here is the deeper issue -- we are arguing here over renewable
> energy prospects, not the best way to make space habitation happen.

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