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  • powerful tap water

    Talking about water pressure, etc, reminded me of this idea- and I'm sure I'm not the only one who has thought of it. Why not add a generator to the water line coming in to the house- every time water runs, the generator turns via a positive displacement rotary device. This would cause a resistance to water flow, so you open the tap a bit more to get the flow rate you want. Presumably you have more than enough pressure from the city water system . Meanwhile, the generator supplements any other electricity you may be getting from solar, etc.

    If you lose power for long enough, this may be your only source. Everybody has a back-up generator of course- or maybe not. I'm just thinking that it's another way to keep a deep cycle battery charged- the one you use for led lighting and communications devices, not to mention keeping your natural gas furnace running when power is out.

    Doing some math would determine how much power could be expected from the normal flows of water- doing dishes, having a shower, flushing the terlet, etc.

    My brain is cramping a bit trying to determine power levels, and how and where the energy goes. Simply by opening a tap, you are releasing energy, but where does it go? Some obviously goes into heat when the water flows downhill to make it to the drain. I'm thinking that some must be lost right at the tap because it's acting as a restriction. Only when some water flows does some energy dissipate, so if you had a generator on the incoming line, the tap would not have to dissipate as much energy to stem the flow. You could almost open the tap wide and control the amount of flow by reflecting to the loading on the generator. The actual quantity of water that you use wouldn't change, so essentially you would be reflecting normal losses back to the generator, which would recover some of it for you.

    Another idea which has been brewing lately is recovering heat from shower water. As it flows down the drain, the heat in it transfers into the pipe carrying it. A sensor determines when the pipe is warmer than the bathroom, and automatically starts a fan. The fan cycles bathroom air around the drain/heat exchanger and warms the bathroom. Any hot water going down the drain would pass through this device, and the heat would go into the bathroom. Everybody likes the bathroom to be a bit warm- nice when you step out of the shower.
    Last edited by darryl; 10-02-2011, 02:42 AM.
    I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

  • #2
    Why not? Bonneville Power does it, and there are several dams on the Columbia river that do this. Why not convert your local water district pump energy to electricy? Very effective when running the irrigation. All that is happening is you are exchanging head pressure to electricity. If it takes your wife an hour to take a shower just let her know it's for the good of mankind.

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    • #3
      Might be a great idea for "gotta have" emergency power but not for a routine lights out. City water is thousands of times more expensive than surface water in situ. Consider water treatment, pumping, system maintenence, expansion, bond retirement, etc. The economics are ferocious. Do the math. 15 gpm @ 45 PSI x 50% efficiency aint much power - about 250 watts. That's about 120 cu ft per hour. Figure $1 per 100 cu ft city rate and you spend about $5 per KwHr. Not a price you'd pay for long. Adjust for local rates.

      But if you have a medical emergency and need strong light or run to an iron lung, who counts cost$?
      Last edited by Forrest Addy; 10-02-2011, 04:49 AM.

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      • #4
        There is nothing new, Daryl, but that which is forgotten. Dentists used to have water-powered drills. They were not exactly high-hp output, but they were adjustable in speed with reasonably constant power.
        Here in Quebec, Quebec Hydro or Gazifere, I forget which, is offering a rebate on home installed waste water energy recovery systems. These are "professionally" installed by approved contractors, and the price after rebate is about $500.00. I just saw them offered in my billing propaganda last week.
        FWIW, the biggest unclaimed bargain in your community, is the waste heat from the shower drains in the Recreation Center. If you think about it, those places operate almost 24 hours per day, and the showers hardly stop. Since shower water is not very "lumpy," a titanium plate exchanger works very well. The water can then be used as preheat to the hot water heaters, (THAT makes the local Medical Officer of Health shudder!) or simply melt the Zamboni shavings.
        Duffy, Gatineau, Quebec

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        • #5
          What I would like to do is set up the recycled water for flushing the toilet deal. I can't figure out though how you would make it work to fill up on recycled water but if there isn't enough gray water to flush how do you make it automatically resort to a fresh water supply for the flush?
          Andy

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          • #6
            Only problem that I see is that your household water never really runs much.
            99% of the day it just sits idle in the pipe.
            Get a drink of water = 5 seconds running.
            Flushing the toilet = 1 minute to refill the tank.
            Taking a shower = 15 minutes
            The actual time that your household water is running is probably not very long.

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            • #7
              It's one of those things that are alluring, but it's probably cheaper to buy a 5kw generator for your local Home Despot.

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              • #8
                Slightly OT, but does anyone really turn off the tap while they are brushing their teeth ?

                I would save a lot of water if I had a foot switch that turned on the cold tap when I stood on it. Especially now my teeth are so poor that my dentist makes me work on them for five minutes - this brush in, that brush out, and so on.
                Richard - SW London, UK, EU.

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                • #9
                  A good point,kiddz. Unless you want a screaming high water bill,can't just let it run!!

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                  • #10
                    Yes, Richard, I do turn the tap off while cleaning my teeth – but I spent five years living on a yacht, and can't seem to break the habit!
                    I now live out in the country, where the water comes from the rain via the roof, so it's still not a bad habit to have.

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                    • #11
                      There are some houses in this country with a passenger lift (i.e. 'elevator') between floors and some of these are powered by the pressure of the city water supply. The requirement is that the water is not wasted so once the water has been through the 20' hydraulic ram it passes to a roof tank for use in the house.

                      In the past, garages used to have a similar thing for their vehicle hoist but I am sure they are all gone now.

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                      • #12
                        Speaking of, my water bill run $100+. About $15 for actual water the balance for wastewater, storm water etc. What's ironic is my loy pitches towards saltwater so no stormwater flows from my lot to the storm drains. Makes no diff according to City Hall.

                        I am a profti center. Why do I even ask?
                        Last edited by Forrest Addy; 10-02-2011, 07:22 PM.

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                        • #13
                          The bottom line is that you can't get something for nothing. This has been an ongoing question for decades and you can't do it.

                          You can recover [some of] your shower water though. They sell systems for shower drains. Ideally you need a good vertical run from the shower to the sewer pipe exiting your house so that it has a while to travel to have time to transfer heat. The way it works usually is to bring in outside cold water (say, 50degF) and preheat it to something like 55-65degF before it goes into your hot water heater. If I were to do a new house I would install one.

                          Even better is to install a solar hot water heating system. Up north they aren't ideal, but you can still do water from late spring to parts of Fall season.

                          KEJR

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                          • #14
                            Originally posted by KEJR
                            The bottom line is that you can't get something for nothing. This has been an ongoing question for decades and you can't do it.

                            You can recover [some of] your shower water though. They sell systems for shower drains. Ideally you need a good vertical run from the shower to the sewer pipe exiting your house so that it has a while to travel to have time to transfer heat. The way it works usually is to bring in outside cold water (say, 50degF) and preheat it to something like 55-65degF before it goes into your hot water heater. If I were to do a new house I would install one.

                            Even better is to install a solar hot water heating system. Up north they aren't ideal, but you can still do water from late spring to parts of Fall season.

                            KEJR
                            The current solar water heater technology uses vacuum tubes to house the collector pipes, so the air temperature isn't as much of an issue. Here the winters involve lots of rain, so the amount of sunlight is much reduced, but apparently you can still get enough hot water for household use.

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                            • #15
                              In answer to the original post about installing a generator in your water line, the amount of energy you can extract from a flowing liquid is called PV work, which stands for Pressure times Volume. You can't get something for nothing, so if you extract energy from the flowing water to power your generator, you will have less PV energy available. Since the volume of water to your home is fairly fixed, your only option to extract energy for your generator is to make use of the pressure drop across the generator, which will only work if you have water pressure to spare. I think a better scheme would be to recover energy from water draining down from the second floor, where it has potential energy from its height, and also thermal energy if it was warm water. Of course, the practicalities of this scheme are about equal to a hamster on a generator wheel design. If, however, you were able to install a generator in the waste water line of, say, a 15 storey building, then there might indeed be some substantial potential energy available to recover.
                              Last edited by Bill736; 10-02-2011, 11:53 PM.

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