Generating electricity by turning on a tap

I can't watch the video as its blocked at work but, surely the water is pumped to our taps. If you put a turbine in the pipes you would increase the pressure loss in the pipes increasing the load on the pumps which use electricity. Are they not then claiming to make electricity using electricity?
 
If they are taking energy out then it will reduce the pressure. This may be viable for areas with an excess of pressure due to the local geography.
 
The company said the design of the turbines does not interrupt water flow and allows for power generation at low pressure levels.
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This is BS. The only way to generate electricity is to use the water pressure, so every turbine will cause a small pressure loss. The amount of pressure lost is determined by the design, but it definitely has an effect, namely that the pressure at your house will be lower. Dropping this a bit will probably not be an issue, unless you are already in a low pressure area.

In most areas water is pumped into towers to maintain a reasonably constant pressure in the system. These guys are just recovering some of that energy, at the expense of pressure for the end users.

I'm not saying this is a bad idea, but they cannot just drop in as many turbines as they want. The pipe that brings water from Katse Dam in Lesotho to South Africa also has turbines in it to generate electricity for Lesotho. I think they generate about 3 MW, but they are powered purely by gravity due to rainfall.
 
I said to my SO about 2 years back - "Theres so much energy to be gained by the flow of water through our pipes". If only I put my ideas to paper :cry:
 
furpile said:
This is BS. The only way to generate electricity is to use the water pressure, so every turbine will cause a small pressure loss. The amount of pressure lost is determined by the design, but it definitely has an effect, namely that the pressure at your house will be lower. .
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This doesnt really make sense to me. If I have a little thing slowing down water being released in my house, I would think that would increase the overall pressure as there is more resistance.
 
ghoti said:
This doesnt really make sense to me. If I have a little thing slowing down water being released in my house, I would think that would increase the overall pressure as there is more resistance.
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The water tower supplies the system pressure (generally speaking). This is determined by gravity and cannot go higher. The max flow you can get out of the tower is if you open the bottom of the tower to atmosphere so that all the water flows out. This is because there is almost no resistance to water flow. Now add a few kilometers of pipe to the tower and have the water run out the end of this pipe, the flow will be less because the pipe adds resistance to water flow (smaller pipes have higher resistance and faster flow also results in higher losses). Now add a turbine in this pipe which will add more resistance and the maximum flow from the tower drops more. As you move further down the system the pressure keeps dropping, and you will see a small drop over this turbine. The end result is that at your house the pressure will be lower and your water flow will drop.
 
furpile said:
The water tower supplies the system pressure (generally speaking). This is determined by gravity and cannot go higher. The max flow you can get out of the tower is if you open the bottom of the tower to atmosphere so that all the water flows out. This is because there is almost no resistance to water flow. Now add a few kilometers of pipe to the tower and have the water run out the end of this pipe, the flow will be less because the pipe adds resistance to water flow (smaller pipes have higher resistance and faster flow also results in higher losses). Now add a turbine in this pipe which will add more resistance and the maximum flow from the tower drops more. As you move further down the system the pressure keeps dropping, and you will see a small drop over this turbine. The end result is that at your house the pressure will be lower and your water flow will drop.
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But if a tap is closed its at max resistance already. So its not like its being put into a state that has not already existed before.
 
EtienneK said:
Article says that it doesn't:
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Of course it does, don't fall for marketing BS. It's simple physics. Those turbines remove kinetic energy from the water and turn it into electricity.

The way they mitigate this effect is installing these turbines in piping that goes downhill. From their site:

Harvesting renewable, low-cost electricity from gravity-fed water pipes
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http://www.lucidenergy.com/
 
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I assume that they'll have variable vanes in the turbine to minimise resistance and lower the power output at times when the pressure is low. When usage is high the pressure will be lower, like what you see when your tap is running and you flush the toilet.
 
Do yourself a favour and go to Sea Point in Cape Town, during winter time...

All the rain water run off from the Mountain and from Sea Point, pours down the roads, gutters and drains and then jets out of wide openings, dotted along the promenade, into the sea.

You have massive amounts of perfectly good fresh water and equally massive amounts of potential energy, uselessly going to waste. Just putting water pipe gravity turbines, would harness a lot of energy.

Why this has never been implemented is beyond me.
 
A few of these along the way from the Lesotho Highlands Water Project could generate quite a bit of electricity but they will have to increase the size of those pipes quite substantially. Gravity from the Highland push water to Guateng.
 
nictron said:
A few of these along the way from the Lesotho Highlands Water Project could generate quite a bit of electricity but they will have to increase the size of those pipes quite substantially. Gravity from the Highland push water to Guateng.
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If you read my first post, they are already doing this.
 
ghoti said:
But if a tap is closed its at max resistance already. So its not like its being put into a state that has not already existed before.
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The problem is you need water flow for the turbine to work. If everybody has their taps closed there will be no flow and no pwer generated. Thus these generators need to be on fairly large supply pipes to ensure sufficient flow at most times to keep the turbine running.
 
furpile said:
The problem is you need water flow for the turbine to work. If everybody has their taps closed there will be no flow and no pwer generated. Thus these generators need to be on fairly large supply pipes to ensure sufficient flow at most times to keep the turbine running.
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I really dont think the idea was to run your taps all the time....
 
ghoti said:
I really dont think the idea was to run your taps all the time....
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No, that's not what I meant. I meant if the pipe is supplying a small neighborhood there will not be sufficient flow in the pipe for most of the day the generate electricity. Thus it needs to be a supply pipe supplying a large area to ensure that the normal water usage results in sufficient flow to make the turbines worthwhile.

Anyway, it's an interesting idea and has some benefits but it's definitely not something that we can install on every pipe available.
 
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