Subject:
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Pelton wheels, photovoltaics, hydro, biomas and marine current [not the "war"]
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Newsgroups:
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lugnet.off-topic.debate
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Date:
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Wed, 26 Mar 2003 10:23:40 GMT
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Viewed:
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3683 times
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> > I wonder how well that would really work,
>
> Good modern photovoltaics pay for themselves in ~13 years and last ~20 years.
> Because they're modular, you can scale your installation easily to provide far
> in excess of the power you need. Or am I misunderstanding your meaning?
>
> > or do you mean I should have
> > my own generator for the winter months when solar is unlikely to provide
> > the power I need.
>
> You just have to angle them differently and keep the snow off. You can easily
> plan for a system that gives enough in the winter and big surplus in the summer.
Not in Scotland; here photovoltaics & wind power are predictably unpredictable.
We are taking a centralised broad-spectrum approach to renewables: hydro,
biomas, wind and marine current power. Right now about 10% of our power needs
come from hydro. However, due to our fantastic geography, marine current [not
tidal] power is now very interesting. See:
http://www.itpower.co.uk/technologies/marine.htm
>
> > I think electric plants are far more efficient than a
> > generator could be (and of course hydro plants are relatively low impact
> > [not zero since they do take energy out of the water and do disrupt fish
> > migrations, and require flooding areas for resevoirs]).
1. Generators
I agree. However: I visited a WWTW [wastewater treatment works] a couple of
weeks ago. It generated half its power needs from a 200kw [2,000,000 light
bulbs] unit which runs on sewage derived methane [the WWTW is power hungry as
the flat site means heavy pumping is req.]. It takes the rest of its power from
the grid. However, at peak times it is cheaper [not more efficient] to use the
emergency diesel generator onsite!
The WWTW [best effluent standard in the world outside Sweden]:
http://www.civ.hw.ac.uk/research/sysgeo/sa_files/site_vists/wwtw/wwtw.htm
2. Hydro
a. The great thing about hydro is that it can be used to store "surplus"
electricity; the extra power is used to pump the water from a lower reservoir
to a higher one.
b. Taking energy from the flow is not normally problem – setting compensations
flows can be.
c. Well run impoundment structures can reduce the risk of downstream flooding
significantly.
>
> Agreed. But remember that the flooded area will be habitat for something else
> too.
The flooding is only part of the problem. Ensuring safety is another. In the
UK, most now have to be designed to cope with the PMF [probable maximum flood];
quite a hurdle. I doubt any will be built for some time [decades].
> The only thing we do routinely that is a real ecological wasteland is
> care for our silly lawns -- most of the steps of which seriously harm the local
> biodiversity.
Think about how much energy is invested in 1st treating and then disposing of
the water you flush down your WC. Why treat water to potable standards; only to
flush it away? Why not use rainwater? Further, why flush so much of it? Flush
volumes as low as 2 litres [~4 pints] have been shown to work fine when many
use >> 4 times that.
>
> Those above mentioned "good" PVs are pretty low efficiency (~9-17% is sticking
> in my mind but it's been a while since I did the reading). There are military
> controlled PVs that are >70% efficient over pretty tight fequency bands and
> > 40% efficient over the solar spectrum. If these were readily available
> (assuming that the cost to produce is not exorbitant -- which I don't know) our
> ability to farm the sun would be much better.
...and a good Pelton wheel [high head] turbine will run at >95% efficiency.
Amazing when you think about it.
>
> Something typically forgotten when discussing the ecological impact of the PVs
> is that they are plastic with toxic heavy metals layered in there. They're no
> cake-walk to dispose of properly and that stuff has to be pulled from the Earth.
>
> Overall, I think that our lack of research funding for alternative energy in
> general and PVs specifically has been disgraceful, but I also recognize that
> there is no reason to expect these technologies to be the energy panacea.
I agree; the nuclear and fossil fuel based interest groups have a lot to answer
for… as do a gullible public. We were told nuclear power would offer
electricity “too cheap to meter”. Instead we [UK] have a legacy of plants
which will take >100 years to decommission, 70,000 kg of weapons grade
plutonium to protect [I think less than 10kg is req for a nuke] and an awful
very long term waste problem.
Scott A
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