OT: GO SOLAR ! Was: go nuclear. Was: Detecting ETI via CO2
- From: "Rob Dekker" <rob@xxxxxxxxxxx>
- Date: Sat, 23 Jul 2005 08:14:07 GMT
Hi Matt,
Nice to meet again. Yet another conversation where we see the same world,
but we see different problems and different solutions.
I'll not respond to most of the comments you wrote, because they were mostly
about opinions and ways of life. In past discussions I have seen that we
tend to disagree sharply when it comes to opinions and way of life. So much
that it is difficult to have a constructive discussion.
Let me instead focus on solar-thermal, because you ran the numbers for that,
and I ran the numbers for it, and we came to totally different conclusions.
So lets find out if we have the same numbers. That should be easy.
Cheers
Rob
"Matt Giwer" <jull43@xxxxxxxxxxxxxxxxxxxxxxx> wrote in message
news:94iEe.22724$
[...]
> > My personal favorite is solar-thermal. At $0.10/kWh, it's now almost
> > competitive
> > with fossil fuel electric production. And it will get cheaper over time
!!
> > Check this out :
> > http://www.powerfromthesun.net/chapter1/Chapter1.htm
> > I'm really surprized there is so little attention being paid to the
> > super-clear, renewable energy generation method.
>
> I have been that route and ran the numbers. It doesn't work.
[...]
> Maximum 100% efficient solar cells can produce no more than 1kWHr per
square meter at the equator
> at noon on the equinox. Everything else is less. You can argue it for the
suburbs but not for cities
> and you haven't got a chance in hell of making power affordable for
factories because of the cost of
> real estate.
>
Well lets see how much real-estate we are talking about.
How much electricity does the US use ? Must be 250 GW or so peak power
usage.
You need 250 nuclear power plants for that.
For solar power : At 100% efficiency, 250 GW at 1000 W / m^2 requires 250
Mm^2 which is an area of about 10x10 miles.
That's nothing, especially since solar-power is best harvested in the
deserts (where nothing lives and grows any way, and land is cheap).
To harvest this energy with solar thermal into elecricity, we need to be
more practical, we need to take some efficiencies into consideration. I'm
taking some reasonable numbers :
For peak-power :
- At 35degrees lattitude (US deserts), the sun is 80 % efficiency on flat
land.
- Collecting / concentrating solar, into a high-temp liquid, to ultra-heated
steam : 80 % efficient or so (mostly due to imperfect mirrors and thermal
loss).
- Rankine turbine generator efficiency to electricity : 30 %
Overall peak-power efficiency : about 19 %
That is in line with the 25% peak-power effciency of a fossil-fuel plant,
and way better than the 5 % efficiency of solar-electric cells.
So we would only need 1/.2 = 5 times the collecting area.
That's thus now 22x22 miles.
Of course, can't always run peak power with solar.
Two more important factors come to mind :
- Sun does not always shine (cloudy days). 70% efficient.
- Sun shines only between 10 and 14 hours/day, and also rises and sets. 25 %
efficient.
That's again another 17% efficiency.
Important to understand is that storage of heat is easy (liquid salt
containers), and can be done virtually without heat loss.
Thus this 17% efficiency of the sun not always shining only affects the size
of the mirror-field. The cost of the power-train remains the same, because
with heat storage, the turbines can continue to run through the night (if
needed).
Overall collecting area, considering all these efficiencies, has now grown
to 52x52 miles.
That might seem a lot, but it's only a tiny fraction of US desert areas.
It's even only a small part of San Bernadino county for example.
And don't forget that we are talking about ALL the US electrical needs !
So collecting area is NOT the problem.
One step further, concentrated thermal energy can be used for
thermal-chemiical hydrogen production. That way, solar-thermal can even
provide clean alternative fuel.
More than enough potential for major energy generation,
No (fossil or other) fuel usage,
No waste products,
No CO2 emission,
No rotating blades that kill birds (or whatever other objections there are
against wind power)
Easy to build, easy to remove (no hazardous materials needed).
No security risk (of people stealing nuclear material)
Low maintenance (gotta clean the mirrors every now and then).
Downsides :
Inexperience with the technology makes investors scary,
Capital investment cost still high (cost of mirrors mainly),
but is comparable or lower than nuclear plants of same electric power
output.
Cooling water sometimes not easily available in desert areas.
Still, the benefits seem to far outweight the disadvantages.
So I wonder why there is so little attention paid to this.
One more thing about distribution : a solar power plant in the desert
will cause more losses on the power grid than a nuclear plant
inside a city. But who wants a nuclear plant in their city any way ?
For example in France, they put almost all their nuclear power
plants on the borders with Belgium and Germany. So that IF
something goes wrong, Paris remains standing.....;o)
Any way, at 10% increase in distribution losses, electricity
would cost less that 0.1 of a penny more per kWh.
An easy price to pay.
So what are your numbers, because I am greatly surprized
how you can conclude anything different than me....
Rob
.
- References:
- Detecting ETI via CO2
- From: Rob Dekker
- Re: Detecting ETI via CO2
- From: Matt Giwer
- OT: go nuclear. Was: Detecting ETI via CO2
- From: Rob Dekker
- Detecting ETI via CO2
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