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    • CommentAuthorTheDoctor
    • CommentTimeDec 16th 2008
     
    OK,

    I was having a discussion with a neighbour (ahh! why does this site persist with a Yanky spellchecker!)

    their words : "we have a f*ck off water main runnung through the estate, can we not get a turbine built into it for local electricity?"

    my response:
    Scottish water wont have any of it - will laugh in your general direction
    flow isnt generated by gravity, but by use, so would be intermittent
    risk of contamination
    risks water supply for faults / maintenance
    will reduce flow - may be high pressure here, but not by the last tap on the line

    so - is there any mileage here, or is this a dafty thought?
    • CommentAuthorbillt
    • CommentTimeDec 16th 2008
     
    It's a non runner.

    The quantity of water needed to generate any amount of power is enormous. E.g. to generate 1kw with a pressure of 2 bar needs about 9litres per second or 800 cu metres a day. If you have a community large enough to use that much water 24kwhrs a day isn't going to go very far!

    The water company will have gone to some lengths and expenditure of energy to generate the pressure in the supply; they won't be happy to have it dissipated in a scheme like this.
    • CommentAuthorTheDoctor
    • CommentTimeDec 16th 2008
     
    as i thought


    hey ho
    • CommentAuthormike7
    • CommentTimeDec 16th 2008
     
    Could serve as a handy 'ground source' of heat for a heat pump, but unkind to users downstream unless they're far away....
    • CommentAuthorTheDoctor
    • CommentTimeDec 16th 2008
     
    saves them having to buy big american fridge freezers with built in ice makers though....!
    • CommentAuthorchrisc
    • CommentTimeDec 16th 2008
     
    It would make more sense to get power from the flow of sewage!

    And the archimedean screw used here:

    http://www.torrshydro.co.uk/Scheme.htm

    Is essentially the same as ones used to pump sewage up -- no reason why they could work the other way around for places with lots of hills and sewage, like Sheffield...
    •  
      CommentAuthorfostertom
    • CommentTimeDec 16th 2008
     
  1.  
    Powering a turbine with mains water is like putting an electric motor on a dynamo and expecting that the motor will turn the dynamo. Mains water doesn't just trickle through the pipes of its own accord, it's pumped through ... and a pump is often driven by an electric motor. The sewage idea has more merit as you'd effectively be recovering some of the pumping costs of the water - plus you could feed it through heat exchanges / heat pumps to recover some of the heat the sewage takes out of people's houses. I wouldn't want the job of de-sliming said heat exchangers though!

    Believe it or not, it was quite legal up until quite recently to use mains water in Montreal in water source heat pumps - the cooled water just was dumped down the drain. A friend of mine who installed his own system used this method temporarily before his ground-loop was drilled!

    At this time of year, the heat from the sewage is used to melt the snow that's removed from the streets in winter an put in large snow dumps - the melt water is then also treated in the sewage treatment plant rather than just being dumped in the river.

    Paul in Montreal.
    • CommentAuthorTheDoctor
    • CommentTimeDec 17th 2008
     
    Paul,

    not entirely true

    pumped in towns and cities and large parts of the country, but a great deal of the system is gravity fed.


    We live well up the hill from the settlement that this mains pipe (12" - 18") serves
    there is an enormous water tank higher up the hill.

    yes, water is pumped to the tank, but the feed to the community is gravity fed

    doesnt mean the flow would be as required though.
    • CommentAuthorjon
    • CommentTimeDec 17th 2008
     
    Sorry guys, the idea of using sewerage is not on

    In the trade there's an item called a houdini. A houdini is a condom that someone has tied and flushed. Said houdini then rots producing gas and expands. The existing free flowing sewerage system then just about gets the houdinis out of the system before being caught at the gratings of a sewerage works.
  2.  
    Posted By: TheDoctoryes, water is pumped to the tank, but the feed to the community is gravity fed


    The pump has to overcome gravity in the first place to get the water into the tank. You won't get more energy out than was used by the pump to put it in the tank in the beginning.

    Paul in Montreal.
    • CommentAuthorTerry
    • CommentTimeDec 23rd 2008 edited
     
    well, guess that means you dont tell the water company what you are doing :bigsmile::bigsmile:
    Reminds me of those stories of people in Africa clipping some wires on to the overhead power lines to nick a bit of lecky.
  3.  
    It does depend on where you live. I was born and brought up in pennine west yorkshire. The reservoirs are several hundred feet up in the hills (typically maybe 1000 ft ASL), filled by rainfall. The water pressure was very good. You could in theory extract some power from the outlet flow to the punters, but I suspect that when you look at the overall picture, the benefits would be very small.
    • CommentAuthorCWatters
    • CommentTimeDec 24th 2008 edited
     
    Water powered appliances were available in early 1900s...

    http://www.dself.dsl.pipex.com/MUSEUM/POWER/watermotor/watermotor.htm

    For info: 40psi is about 2.8 bar
  4.  
    Many cities "in the old days" had networks of hydraulic power that people (i.e. companies) could use. Not very efficient though. Some cities also had networks of steam that buildings could use for heating - I remember when I was at UMIST in the 1980s seeing a statement showing how many million kg of steam had been bought from nearby Bloom Street Power Station (not a cooling tower in sight - it was a pure CHP setup). Sad how quickly things like that are forgotten and how many times a wheel has to be reinvented.

    Paul in Montreal
  5.  
    If someone were to extract energy from flow of water in a pipe which you got to flow you would probably be right in saying that they were stealing the energy which you put in to make it flow.
    • CommentAuthorbiffvernon
    • CommentTimeMar 10th 2009
     
    It's like that daft idea of speed bumps generating electricity. It's theft of your energy.
    •  
      CommentAuthorfostertom
    • CommentTimeMar 10th 2009
     
    Or forums creating friction
    • CommentAuthorcookie
    • CommentTimeMar 11th 2009
     
    Its been against water by-laws in the UK since the 1st or 2nd world war to use mains water to generate electricity (i think it covers driving any device from the pressure) after people were running stuff from it.

    Cookie
    •  
      CommentAuthorfostertom
    • CommentTimeMar 11th 2009
     
    And to take heat out of it?
    • CommentAuthormike7
    • CommentTimeMar 11th 2009
     
    Posted By: mike7Could serve as a handy 'ground source' of heat for a heat pump, but unkind to users downstream unless they're far away....


    The idea was to have a pipe in the ground close but not connected to the main, so the main would indirectly help provide the ground array.
  6.  
    ...but say for the purposes my mains pressure was far in excess of what I needed at the taps, could I slow it down a bit with a turbine and get anything useful...?

    J
    • CommentAuthorEd Davies
    • CommentTimeMar 4th 2012 edited
     
    The energy available in joules from a given amount of water is the pressure difference in pascals times the volume in metres cubed.

    1 m of head is approx 10 kPa (because a 1 m cube of water has a mass of 1000 kg so a weight of about 10'000 N, well 9'810 N if you want to be a bit more precise).

    Convert joules to kWh by dividing by 3'600'000 (i.e., 1 kWh = 3.6 MJ).
  7.  
    I have been onto both our local water utility companies to put turbines on there river compensation flow outlets and have been refused by both. The excuse was "were into water supply not power generation". How stupid is that.
    • CommentAuthorJoiner
    • CommentTimeMar 5th 2012
     
    Why not try and get funding for a feasibility study and circumvent the indifference of the utility's local management? Give them something to consider other than a vague idea?

    It's happening elsewhere... http://www.energyshare.com/shrewsbury-hydro/

    LEAF is only a couple of months old, so probably still money in there... http://www.localunited.net/?q=node/79
    •  
      CommentAuthorSteamyTea
    • CommentTimeMar 5th 2012
     
    Posted By: renewablejohnwere into water supply not power generation

    Not stupid at all. They are legislated to discharge at a minimum quality, the last thing they need is a conflict of interests (and a physical restriction) that may upset the flow rates and cause lagooning above a river. One heavy spell of rain and the effluent may well have to be discharged rapidly into a river.
    Happens here a lot, why we have the most expensive water in the country, we do not have the geography to allow a safe distance between the centres of population and the sea (most towns are on the coast). One down poor and Portreath has a brown river running across the beach, mind you it smells there anyway.
    • CommentAuthorJoiner
    • CommentTimeMar 5th 2012
     
    Nick...

    "river compensation flow outlets"

    :wink:
  8.  
    Posted By: TheDoctorOK,

    I was having a discussion with a neighbour (ahh! why does this site persist with a Yanky spellchecker!)

    their words : "we have a f*ck off water main runnung through the estate, can we not get a turbine built into it for local electricity?"

    my response:
    Scottish water wont have any of it - will laugh in your general direction
    flow isnt generated by gravity, but by use, so would be intermittent
    risk of contamination
    risks water supply for faults / maintenance
    will reduce flow - may be high pressure here, but not by the last tap on the line

    so - is there any mileage here, or is this a dafty thought?


    I knew I read about this the other day:

    http://www.scottishwater.co.uk/about-us/press-releases/latest-press-releases/scottish-water-starts-ambitious-hydro-scheme

    Scottish Water are at it themselves just for their own treatment plants, must have stolen the idea from here a few years ago :bigsmile:
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