After the couple of plumbing related threads I wonder how plausible this would be...
Attach a waterpump to the mains supply, running a generator, and run the water as fast as you can...
How many kWh per day would this be able to make?
Not that I'd wantonly waste potable water like that of course.. ;-)
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Not sure but I guess someone who's good at sums will be along shortly!
Funnily enough though, and even before I'd heard of Dick Strawbridge, a related thought did come to my mind. In our last house we had a little stream running alongside our garden. Only small but fast-ish flowing.
I did sometimes think about trying to harness the power of the flowing water. Never got around to it though. Maybe should've. We've got a canal here now but that just sort of sits there being brown.
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The power you're using is given by the pressure drop multiplied by the volumetric flow rate.
Lets say the pressure is 3 Bar above atmospheric -> 3*101325 ~= 300000 Pa
A reasonable flow rate might be 1 litre per second = 0.001 cubic metres per second
So, that's 300 W
Here's the problem though, you need to estimate the efficiency of your wheel, generator, switching, and control. If you actually saw 10W output, I would be surprised.
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>>So, that's 300 W
Thinking about it a bit more, owing to the internal resistance of the pipework, it's unlikely that you would get the full supply pressure and the maximum flow together, so, 300W, for the figures I began with represents very much a theoretical maximum power available from the supply.
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>> How many kWh per day would this be able to make?
Not enough to offset the cost of the metered water, is my guess.
Otherwise you'd have mains water-powered power stations.
Last edited by: Dave_TDCi on Tue 21 Jun 11 at 22:25
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You could though, run some water into a header tank, best of all using a hose attached to your next door neighbour's outside tap when he's out.
Then you run a pipe from the header tank in your loft down to a catcher tank in your cellar. In between you have your little generator. This is then free power once you have amortised the costs of the tanks, piping and the generator.
The only downside I can see is the difficulty and possible considerable expense of the procurement of a slave to hand pump the water back up to the header tank.
Last edited by: Humph D'Bout on Tue 21 Jun 11 at 22:33
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Re N/C's calculations - I reckon the mains supply will feed more than a litre/second - run all your cold taps at once and see how long it takes to flood all your sinks ;-)
I also assume you meant 100W rather than 10W - 3% efficiency seems a bit cack for a pump/dynamo set-up.
Oh and no water meter.. and in Scotland so no shortage of H2O either!
Last edited by: Lygonos on Tue 21 Jun 11 at 22:39
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>>seems a bit cack for a pump/dynamo set-up.
But realistic perhaps?
It's not easy making small hydraulic devices which are efficient. You aren't going to have enough flow rate to use the dynamics of the water efficiently, so, you would need to rely upon sealing the water in the vanes or gears of your hydraulic motor. Not easy.
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Hmm.. maybe more efficient to use a big header tank then and run it intermittently like a hydro-electric generator. Got 3 big plastic tanks in the attic from when the house was a hotel - looks like each can hold a ton of water or so (roughly 1m cubes)
Wonder how long the elctricity savings would take to pay for new rafters when they came crashing into the bedrooms!
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"Oh and no water meter.. and in Scotland so no shortage of H2O either!"
It is actually against the law to fit a device that wastes water even in Scotland.
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We have a very small stream running through our garden, at one point there is a waterfall with a drop of about 30". I once tried fixing some blades onto an old bike wheel with a dyno-hub and holding it under the water. In the dark it was just about possible to see a cycle bulb flickering faintly.
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I knew of somebody who resurrected an old water mill to generate electricity from a stream.
The waterboard were soon along to demand their pound of flesh.
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You can get around 60% efficiency from a water wheel.
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You are so lucky to have a small stream running through your garden.
How could you?
Rusty old bike wheel?
Pat:)
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>> You are so lucky to have a small stream running through your garden.
>>
>> How could you?
>>
>>
I dug it myself. The ground slopes, and there is a spring in the top corner, previously flowing through the bank into a ditch by the road. I dug a long trench all the way down to the bottom gate, where the stream rejoins the ditch. On the way it feeds a series of ponds and passes under bridges and down cascades and waterfalls.
Pure fantasy on a very small scale. Most summers the stream dries up, but the ponds stay full.
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I was greatly impressed by this power station on a visit to Pugs part of the world ...
Electric Mountain at Dinorwig , same principle only bigger....
The basic idea behind Dinorwig is quite simple. The power station consists of two lakes, Marchlyn Mawr, high in the hills behind Elidir Fawr, and Llyn Peris on the valley floor. The lakes are one-and-a-half kilometres from the other, with a height drop of 500 metres separating them. The two are connected by a series of pipelines. Inside the mountain between the two lakes is the largest man-made cave in Europe, the inside of which looks remarkably like the set for a James Bond movie. Inside this cavern are the turbines.
When there is a need for power, water is allowed to flow out of the upper lake, down through the pipes into the turbines, at immense pressures. Gravity acting on the water forces the turbines round and once the water has passed through, it drains down into the lower lake. This in itself is an excellent system, but can only be used once; if the top lake is empty then no more power can be produced. The solution is simple. During the night when there is an excess of power in the National Grid, the turbines are reversed and are used to pump water from the lower lake back to the top lake, ready for the next peak in demand.
Simple ideas are sometimes the best. Worth a visit.....
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>> The solution is simple. During the night when there is an excess of power
>> in the National Grid, the turbines are reversed and are used to pump water from
>> the lower lake back to the top lake, ready for the next peak in demand.
Presumably any rain helps, although only by a very small precentage?
Been there some years ago, and yes, very impressive. And it turned the control is in a building just down the road from us (just outside Reading) - I'd been cycling past it on the way to work.
Last edited by: Focus on Thu 23 Jun 11 at 15:35
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Solutions like the Dinorwig power station are needed. The problem with renewables like wind and tidal is you cannot depend on them to produce power when needed. If it's not windy for the wind turbine you're out of luck. At least gas fired power stations can be ready to increase production.
Some wind farms are deliberately off because they are producing energy that is either not needed or the wind farm owners are getting paid to leave them off.
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Some wind farms are not even connected to the National Grid. It's called an Energy Policy...for numpties...
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>>If you really want home power, a garden installed heat pump?
www.energysavingtrust.org.uk/Generate-your-own-energy/Ground-source-heat-pumps<<
Interesting & thorough article mad f, having read and digested it in it's entirety, the system wouldn't be one I'd choose.
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Home "power station" - Runfer D'Hills
