h a l f b a k e r y"This may be bollocks, but it's lovely bollocks."
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Turn stagnant bodies of water (public reservoirs, lakes too polluted to suport life, etc.) into solar collectors, either by using the the water itself to absorb the energy, or by floating a net of connected solar collectors across the surface.
After all, the water's just sitting there.
OTEC
http://www.mrtc.org/~mist/ote.html
Ocean Thermal Energy Conversion [reensure, Feb 26 2001]
Thermoelectric Power Generation
http://www.epa.gov/...er_with_america.htm
47% of the demand for water in the U.S. [reensure, Feb 26 2001]
Hydrodynamics of a pump
http://www.thepump.org/pumpoperation.htm
technobadger--this is cool speculation. [reensure, Feb 26 2001]
Solar Pond
http://en.wikipedia.org/wiki/Solar_pond
[afinehowdoyoudo, Dec 11 2009]
[link]
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The OTEC site link to the left is a fine example of heat exchange technology. Some of the evaporation and fluid pressure dynamics support a bizarre theory of why there are a series of empty chambers under Gaza's great pyramids, but that is another story. |
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Forgive my ignorance as to the nature of reserviors. I thought hydroelectric dams were powered by water as it flowed over turbines. But still, for polluted bodies of water that are sitting out in the open a floating net of collectors might be useful. |
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reensure- Giza pyramids(?) |
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sure thing, ravenswood. let me know when you've got (based off of degroof's figures) $1,672,704,000,000 laying around. :) |
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You wouldn't use photovoltaic cells for large-scale solar power production. You'd use an array of concentrators. The land requirement is about 5 acres/megawatt. When you consider the mining requirements for fossil fuel plants, the land usage is about the same. |
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7% efficiency is pretty bad for modern photovoltaic cells. Most of the producers targeting the home market shoot for around 15%-20%. |
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This thread has been quiet for a month or so and I have just discovered the site. Could anyone confirm this discussion thread is still extant? |
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Hmmm... So if I buy the solar
array, it'll pay for itself
within my mortgage's lifetime. |
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One plus point to floating solar panels on the surface of reservoirs is that you would cut down on water wasted through evaporation. The reduced oxygen interchange would probably kill the fishies though. Still, if you actually wanted to produce hydrogen rather than electric current, an integrated modular solar panel/electrolytic cracker would be worth investigating. |
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Better yet, have the sun heat the water, making some of it evaporate. Then, as the water rises, it condenses into large vapourous masses. After that, have differences in air pressure push these masses up against mountain ranges or to higher elevations. This would make the water condense even more, making it heavier leading to its fall to the ground. Collect this water in a big tub, then use its new potential energy to turn a turbine attached to a generator! |
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So... do I have a Nobel Prize or what? |
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Rough numbers, 11% effeciency is not unheard of.
And the planet uses about 10 terrawatts annually. |
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I can't remember the geographical location, but some people proposed making a hydroelectric dam in a certain area some time back (before they had computers that could simulate all the fluid and structural dynamics, etc) and so they built a scaled down model of all the geography to test it. They discovered that the rate of evaporation would make the whole idea impossible. But using this idea to prevent evaporation and harness some extra power to boot just might be a good idea in this situation. |
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Even if the solar cells weren't efficient enough in and of themselves to be worth the overhead, they would eliminate the obstacle to harnessing a great deal more energy in this particular case. And maybe in others. |
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Solar power is an underdeveloped technology. with research I'm sure efficiency could be improved. As for floating solar panels on unused bodies of water, why not; as mentioned it's not being used any other way. |
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[funcrusher]i think the idea is really good. although the discussion has been diverted to solar cells etc, if i have understood correctly, i support & augment your ideas as:a) floating collectors would help avoid occupation of land for equal energy collection, b)as you have mentioned about water bodies heavily polluted to support life,there would be no possibility for fishing etc. so these can be converted to solar ponds-a very old & proven concept.details of solar pond can be obtained easily on the net. |
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And further, add an air pumping
system to the bottom of the lake.
This will oxygenate the water to
compensate for the loss of
exposed surface. |
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However the lack of light will kill
any plant life in the water, so
you'll probably still have a dead
lake. |
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OTOH no-one ever said this thing
has to cover the whole lake. If it
was only a portion, vegetation
would still grow elsewhere, and
the panels would
provide a shady spot for stressed
fishies to hide out on a hot day. |
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And integrated water cooling will
keep the efficiency of those panels
up nearer their rated max. |
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//You wouldn't use photovoltaic cells for large-scale solar power production. You'd use an array of concentrators. The land requirement is about 5 acres/megawatt. When you consider the mining requirements for fossil fuel plants, the land usage is about the same.// |
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Say what now? Did the voices tell you that? |
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...This is a big idea about making incredibly low "quality" power. Thermodynamics tells us that changing a body of water's temperature by a few single degrees might well take a great deal of energy - but you're only ever going to be able to use a tiny little fraction of that energy in any useful way. "entropy is a harsh mistress" as they say. |
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Yes, thermodynamics rules with an iron fist, without
even a velvet glove to soften the grip. But the
challenge of solar power is not about efficiency... all
that energy ends up as heat anyway. The real
challenge is cost, and it may be that a huge, cheap,
inefficient collector is the best deal, at least in the
short term. Say a salt pond developed a delta-T of
40C, that puts the max efficiency at about 10% or
better.. |
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