An interesting way to generate hydro power

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The Masked Marauder
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An interesting way to generate hydro power

Post by The Masked Marauder » Thu Oct 25, 2007 3:20 am

Rentricity, a start-up in New York City, has come up with a hydroelectric generator that lets municipal water facilities generate power. Pressurized water from the facility passes through a turbine, and the turbine produces water. The water subsequently comes out of your faucet.

http://www.news.com/Pint-size-hydro-pow ... 15142.html

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chewey
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Post by chewey » Thu Oct 25, 2007 2:34 pm

Sorry, there's no power generation involved here. It's a clever way to transport electric power without a wire,
but all the electric energy that comes out of the generator (and even more than that, energy conversion is never 100%
efficient) has to be put into the water in form of additional pressurisation - probably using electric powered
compressors in flat land.

Neat idea to power remote water treatment facilities that don't have another way to get electricity: Yes. (how many of those are there?)
Green energy: Not at all.

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Post by The Masked Marauder » Thu Oct 25, 2007 5:24 pm

The article should have said "power reclamation" instead of "power generation". At least the water treatment plants can recover some of the power that they used to pressurize the water. It's better than just throwing it away when they bleed off excess pressure.

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Post by chewey » Sat Oct 27, 2007 1:27 am

The Masked Marauder wrote:The article should have said "power reclamation" instead of "power generation"
Yup :-)
At least the water treatment plants can recover some of the power that they used to pressurize the water. It's better than just throwing it away when they bleed off excess pressure.
I'm not sure I understand what is meant by that: Water is not compressible (at least not at the pressures we talk about
here), so decompressing by volume increase is out of the question. And usually, the rpm of a liquid powered turbine only
depends on the flow rate (i.e. volume/time), regardless the liquid's pressure. If we now assume water is not pressurised
more than necessary in pumping stations (everything else would be a waste of money, and we all know corporations
tend not to do that if it affects their pocket), the only way to get power out of such a device without interfering
with the water system's function would be to increase the pipe pressure to maintain the same flow as without that
turbine - the flow now just has to overcome the additional "resistance" of the turbine. Still a net loss of energy.

And even if water is pressurised more than would be neccessary, the easiest way to reduce the power bill would be
to turn down the compression instead of trying to recuperate that power at another place with a loss.

If of course the pressurising is paid by someone other than the one using the device, it is a neat way to tap someone else's
power bill - but that sounds very much like a very successful lawsuit for the one being tapped.

This whole thing looks like a solution in search for a problem to me.

I however am no water treatment engineer (just a physicist ;-) ), so there might very well be something I'm not aware of
in the water treatment process making the device useful - I guess I'll have to talk to someone in the business.

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