[ExI] Direct solar electrolysis - decentralised fuel infrastructure, is it viable?

Keith Henson hkeithhenson at gmail.com
Wed Oct 15 01:17:51 UTC 2008

On Mon, Oct 13, 2008 at 8:28 PM, Emlyn <emlynoregan at gmail.com> wrote:
> Keith's evangelism of solar power satellites is very interesting, but
> the extreme centralisation of the power production has to make you
> nervous; at best, it's business as usual big capital monopoly on
> power. I think we should probably do it, actually, but the barriers
> seem so large.

I don't see why you worry about centralization.  Bechtel builds a huge
number of power plants and controls none of them.

> On a related note, I recently watched the talk "Energy Literacy" by
> Saul Griffith (http://etech.blip.tv/file/1018152/), and was of course
> daunted by the scale of terrestrial plant we'd need to construct (and
> the amount of land it would require) to do anything serious about
> greening world energy production.
> It got me to thinking, is there a way to decentralise this? Could we
> think of a way that, instead of requiring mega engineering, mobilised
> thousands (millions?) of "mom and pop" operations to do the work?

Unfortunately with the current level of technology, no.

It's not hard to calculate.

> Also, I'm based in South Australia, one of the great early losers of
> the climate change debacle. The feeder river into the state (there is
> only one of any consequence), the River Murray, is just about dead,
> and it's just not really raining any more. So, the northern part of
> the state which is unusable for agriculture (think red desert) is
> marching south at speed, the ability to provide enough water for the
> state capital Adelaide is in doubt, and farmers are no longer allowed
> to irrigate in many places, ie: are sooo screwed.
> So what we have here is:
> - Sunshine (not much ozone layer to worry about way down south here, either)
> - Land (unusable)
> So I think solar power is probably a go.

It's not an economic go in Arizona where there is a hell of a demand
for power in the summer, in the daytime.

> What we should really do here is create some godawfully huge solar
> power farms, cover masses of that desert, produce massive amounts of
> power, use it to run lots of desalination plants, and away we go. The
> city isn't landlocked, after all. If we threw money at it on a large
> enough scale, we could set up serious world leading research
> facilities, boost the unis, and eventually maybe have something of
> interest to export.  But I digress.

> I'm thinking, what can small amounts of capital do here? You could set
> up a little solar farm, presumably, for thousands rather than
> millions, on cheap land (you can buy ghost towns for less than a
> modest house in the city), but then what? I get the impression it is
> expensive to be a traditional power plant; you can just pump the
> output of your small solar farm into the grid and expect that to be ok
> or make you money.

The ROI is terrible.  The only reason it makes any sense at all is
huge government subsidies.

> Or you could make hydrogen, I'm thinking. Pump the solar generated
> electricity into hydrogen electrolysis equipment, voila lots of
> hydrogen.

At 100% efficiency it takes 30 kWh to make a kg of hydrogen.  In
practice current cells take 48 kWh.  A kg of H provides roughly the
same energy as a gallon of gasoline.  If the energy costs you upwards
of 50 cents a kWh (and it may be more like a dollar per kWh) then
until gasoline goes to $24 a gallon, you are not going to make money
on your desert filling station.  Sorry.

> You need water, problematic potentially, but do you need
> much? Anyway, suddenly you are making fuel. That fuel can now be
> trucked around, or you could sell it directly if you were next to a
> decent road, just put a fuel station ("gas" station) on the front of
> your farm.

Hydrogen doesn't truck around fer beans.  Big problem, so bad that
using carbon to carry it is a good idea in spite of the cost.

> And that turns out already to be being done in California, apparently.
> I can't find a link to anything direct about that, but apparently
> there is such a station there. Can someone link something more
> specific?
> So... could you turn this into something commercially viable for a mom
> & pop operation, such that they lay down their dollars, a solar farm +
> hydrolysis equipment + storage facilities + commercial gas station is
> constructed, and they then operate this, selling their gas? I don't
> have numbers, and am struggling to put any together, just not my
> expertise I'm afraid. With 25 year lifespan on the kinds of solar
> cells you'd use, you don't have the problem of replacing cells all the
> time, but it could possibly be scuttled by a poor hydrolysis
> efficiency compared to centralised large facilities. Also it assumes
> people actually start wanting hydrogen in the future; right now no one
> wants it, certainly not at the price of electrolysis (see here:
> http://www.iags.org/n032805t2.htm).
> I also can't get a feel for how much land you'd need to produce a via
> amount of hydrogen. I have access to a nanosolar solar cell sample
> here, with peak output of about 0.33 watts for a piece about 0.01m^2 ,
> so thats 33 watts for 1m^2, or 1kW for 30m^2. It's not a high
> efficiency type of cell (20% I think), but flexible printed stuff,
> cheap apparently, no numbers available though sorry.

Sunlight comes down at more like a kW/m^2.  so 33 watts would be 3.3%

If you wanted to do something wild, consider putting a long pipe with
osmotic membranes on it into the ocean, down more than 5000 feet.  You
can pump fresh water out of it.  The lift is only a few hundred feet.

> --
> Emlyn
> http://emlynoregan.com - my home
> http://point7.wordpress.com - downshifting and ranting
> http://speakingoffreedom.blogspot.com - video link feed of great talks
> on eCulture
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