
Portland's water pipes are the newest source of clean energy - prostoalex
http://inhabitat.com/portlands-water-pipes-are-the-newest-source-of-clean-energy/
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viraptor
I have to admit, I know very little about city-wide water systems, but since
they cannot be realistically based on gravity there have to be pumps that add
the pressure to the pipes providing drinking water. Doesn't that just mean
they're making water companies spend more electricity to pump the water and
get back tiny bits at customer's site?

The flushing part seems more interesting, but apart from single homes doesn't
that have the same effect as partially blocking the toilets? I know that too
much pressure difference in apartment buildings can have very bad results...

So does it really make sense, or is it just "stealing" the power from water
company?

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m_t
From what I read on reddit some time ago when this was posted. With completely
false number.

In our example city, you need to pump water on high ground, and then let it
flow down. The high ground is at 30 unit. The water will be at the right
pressure between 30 and 20.

But when it will reach 20 and below, there is too much pressure for the pipes!
What is currently used is some kind of pressure relieving system that will
release a bit of the pressure. The water can now come down between 20 and 10.

But then again, there's too much pressure for the water to go from 10 to 0
without damaging the pipes. Another valve is there to take care of this.

So, for now, energy is used to pump the water up, and then we have to waste
that energy when the water goes down in order to maintain acceptable pressure.
With the new system, a part of the energy that was used can be harvested
again.

This is the same idea behind harvesting the braking energy on hybrid cars.

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viraptor
Makes a lot of sense, thank you!

