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  1. #31
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    Quote Originally Posted by Ariadne View Post
    Not ever enough so long as the water companies fail to deal with leaks in the main pipe system.
    !
    As an ex water company engineer, it infuriates me when ill-informed statements such as this are made. Water companies have already spent millions on leak finding and repairing. The majority of remaining leaks are below ground and not visible from the surface. The only realistic solution is a program of replacement of ageing pipelines over a period of years - starting with the oldest some of which are over a century old. The problem is that Ofwat will not grasp the nettle and endure the resulting flack from customers whose roads are dug up and water charges raised. Yes, this is going to cost a lot of money! and the cost would not be spread equally over the whole population.
    The current approach is to improve the instrumentation on service networks and identify where the flows are greater than theoretical predictions, indicating leakage as well as improved response to reported surface leaks but repair of one leak on an aged system often results in the water finding the next weak spot.
    Water is an undervalued resource and fantastically good value at under 1 per cu metre. How much would a similar amount of the bottled variety cost?
    Rant over

  2. #32
    WilliamUK is offline Registered User
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    Quote Originally Posted by outtametree View Post
    Longest short list in history!
    Well, I didn't say it's be a SHORT shortlist.



    Ghostlymoron - any particular reason water companies don't use something like the gas pig? (Assuming they don't.)
    William
    Blithe Spirit - Lark 1804.

  3. #33
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    Whatever is or was a gas-pig?!

    Ghostlymoron, as a professional, your view must be of considerable significance here...

    ...is it likely to be a worthwhile benefit, if homeowners use the contents of rain-waterbutts (or seawater if available), to flush loos?

    If dedicated cistern-tanks sat in attics, and were filled by rain (or pumped full from the sea), mightn't we reduce drinking water wastage?

  4. #34
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    Quote Originally Posted by dancrane View Post

    Even if it doesn't suit desalination, it could create power. How many kw hours are required to lift 100 tonnes through five meters?

    DC

    back to school physics

    potential energy = mgh

    100,000kg x 5 meters x g (9.8)= 4.9 Mega Joules

    assuming 100% efficency and released over 4 hours (Ignoring slack water) would only give 340Watts

  5. #35
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    Mega joules? Okay. I said at the start, I was out of my depth.

    Does your calculation imply that 340 watts would be sufficient power to elevate 100 tonnes through 5 meters, during the 6 hours of a rising tide? I'd have imagined more would be needed, and that conversely, more could be extracted, by that weight descending.

    If a platform raised 100 tonnes of water every twelve hours, and then, that water then poured back through a fairly traditional water-mill-wheel, turning a dynamo, would it only generate a third of a kw?

    Presumably the benefit would be that it needn't be limited to 100 tonnes, and wouldn't rely on any energy input, and wouldn't vary in its output, because (aside from differing neaps and springs) lunar activity isn't inconsistent in the way wind and solar are.

  6. #36
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    Quote Originally Posted by dancrane View Post
    Mega joules? Okay. I said at the start, I was out of my depth.

    Does your calculation imply that 340 watts would be sufficient power to elevate 100 tonnes through 5 meters, during the 6 hours of a rising tide? I'd have imagined more would be needed, and that conversely, more could be extracted, by that weight descending.

    If a platform raised 100 tonnes of water every twelve hours, and then, that water then poured back through a fairly traditional water-mill-wheel, turning a dynamo, would it only generate a third of a kw?

    Presumably the benefit would be that it needn't be limited to 100 tonnes, and wouldn't rely on any energy input, and wouldn't vary in its output, because (aside from differing neaps and springs) lunar activity isn't inconsistent in the way wind and solar are.
    I was quoting 100% efficency the actual power generarted would be much lower.

    Coincidently I have a 335Watt pump which quotes 140L/min at 5Mtr head
    To pump 10 tonnes would take 11 hours or approx 50% efficency which is very good .


    These things have to be scaled v large to make ecconomic sense.
    There was talk of daming the severn estuary and generating power doing exactly what you are suggesting

  7. #37
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    I hope your Severn idea wasn't a joke? I reckon it's excellent good sense!

    I suppose my earlier idea (and you've confirmed the slow thoughts I had, since) is equivalent to a 10m x 5m x 2m swimming pool being filled from a point 5 meters below...

    ...that would only require a Rule 3600gph bilge pump, running at maximum capacity for 6.5 hours. Sounds entirely possible, and as you say, not a huge amount of power is required or recoverable, for lifting/dropping that quantity.

    But presumably it would be possible, using what in effect would be a 'tidal-pump', to fill a reservoir ashore, (ideally well above ground level, for greater pressure)...

    ...not pretty, but an asset, if at a moment's notice, you can let thousands of tonnes of brine pour back to the sea, driving very big dynamos as it goes? Just like a hydro-electric dam, but without waiting for rain to fill the lake.

  8. #38
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    Quote Originally Posted by dancrane View Post
    I hope your Severn idea wasn't a joke? I reckon it's excellent good sense!
    It's been scrapped


    http://www.bbc.co.uk/news/uk-11565230

  9. #39
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    Quote Originally Posted by padge View Post
    What a poor, myopic, unadventurous, ill-fated, past-facing bunch we are. Every time something could be done that might sort out our troubles, we think better of it for silly reasons, and rely instead on systems that we had already shown to be inadequate!

    There's a windfarm-theme on the forum at the moment, about the IoW/Dorset coast site. I'd thought only of the disagreeable view, and the possible inconvenience to mariners...but right here and now, I hope it will go ahead.

  10. #40
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    Quote Originally Posted by dancrane View Post
    Whatever is or was a gas-pig?!

    Ghostlymoron, as a professional, your view must be of considerable significance here...

    ...is it likely to be a worthwhile benefit, if homeowners use the contents of rain-waterbutts (or seawater if available), to flush loos?

    If dedicated cistern-tanks sat in attics, and were filled by rain (or pumped full from the sea), mightn't we reduce drinking water wastage?
    Agree that using potable quality water for flushing toilets doesn't make sense but unfortunately we would need to duplicate the internal plumbing in everyone's house. A lot of commercial properties these days do include rainwater harvesting (B & Q for instance) and have a display showing the amount and percentage. It's a lot cheaper to install in new build than existing properties.

    Pigging (they can't touch for it) is difficult in street water mains where the majority of leaks occur due to the number of service connections. I don't know whether this technique is used by water companies.

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