PDA

View Full Version : powerful tap water

darryl
10-02-2011, 02:31 AM
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.

dp
10-02-2011, 03:20 AM
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.

Forrest Addy
10-02-2011, 04:33 AM
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\$?

Duffy
10-02-2011, 10:36 AM
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.

vpt
10-02-2011, 10:46 AM
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?

KiddZimaHater
10-02-2011, 11:02 AM
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.

Tony Ennis
10-02-2011, 11:25 AM
It's one of those things that are alluring, but it's probably cheaper to buy a 5kw generator for your local Home Despot.

rohart
10-02-2011, 05:00 PM
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.

gwilson
10-02-2011, 05:09 PM
A good point,kiddz. Unless you want a screaming high water bill,can't just let it run!!

Mike Burch
10-02-2011, 05:16 PM
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.

The Artful Bodger
10-02-2011, 05:18 PM
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.

Forrest Addy
10-02-2011, 07:16 PM
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?

KEJR
10-02-2011, 07:38 PM
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

Robin R
10-02-2011, 08:44 PM
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.

Bill736
10-02-2011, 11:45 PM
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.

darryl
10-03-2011, 12:19 AM
Yeah, ok. It's not powerful tap water then, it's weak tap water :)

Unless you ask the over-unity boneheads. Ok, no need to go there-

MichaelP
10-03-2011, 02:44 AM
Dentists used to have water-powered drills. They were not exactly high-hp output, but they were adjustable in speed with reasonably constant power. Duffy,
I've never heard of them. Do you happen to have any references?

Duffy
10-03-2011, 03:37 PM
Sorry Michael, I only have "anecdotal" evidence.
That is, a very close friend lived in a Campbellford Ontario, and HE new a dentist there who had one up until about 1945, (end of the war,) when he went "modern."
They apparently had been fairly common, particularly earlier in the century. Quality speed-controlled small electric motors with enough oomph to handle the"string and pulley" system on a dental drill were pretty scarce. On the other hand, 50 psi water pressure WAS pretty common, especially in towns with fire departments. Given a 1/2" inlet, 50 psi and a pretty simple impeller design and you would have a useful power output.
Remember, back in the day, water was VERY cheap, usually included in taxes.

The Artful Bodger
10-03-2011, 04:52 PM
There would have been nothing particulary unusual about using town water supply to drive mechanical devices at the turn of the 19th century.

For example, Oamaru is a small town in New Zealand where in 1882 they installed a town water system gravity fed from a line of aquiducts etc. They specified at the time that the water supply would be adequate for the town and provide so many horse power for other uses. Some traces of the system remain in the older warehouses.

Town supply water was also commonly used to drive air pumps for church organs.

Of course, in some major cities companies laid water pipes for the sole purpose of selling hydraulic power to clients. No doubt dentists would have been able to plug into these but also the first passenger elevators. IIRC an hydraulic company in London were able to eventually sell their pipes and right of way for laying fibre optic cables.

http://www.ipenz.org.nz/heritage/itemdetail.cfm?itemid=2360
also Google Schmid water motor.

The Artful Bodger
10-03-2011, 04:53 PM
Remember, back in the day, water was VERY cheap, usually included in taxes.

It still is cheap and still included in 'taxes'.

jep24601
10-12-2011, 11:52 AM
Manchester, UK, used to have a hydraulic high pressure water power system using non potable water in the area of the old city. It's main use was to power presses in the cotton mills.

Blackpool, UK, has a piped seawater system. (good for snow removal).

Paul Alciatore
10-12-2011, 12:52 PM
As others have suggested, if you do do the math, you will find that it will only produce a small trickle of electricity and cost a bundle. Harnessing an exercise wheel in a hamster cage would be better.

On the tooth brushing thing, I normally did turn the water off, but in my present situation, the bathroom sink is at the end of a very long run from the hot water heater. I usually brush my teeth and shave in the morning and I must let the water run for a couple of minutes to get hot water to shave. So, I turn the hot water on, catch a glass of the unheated water to rinse my mouth and then brush my teeth while the water gets hot. Then I shave. Again, I would normally shut the hot water off while shaving, but it gets cold quickly so I have to leave it run. I shave quickly to avoid the double waste of water and gas to heat it. And, yea I know I should install one of those instant water heaters in that line. It's on my long list.

gary350
10-12-2011, 01:05 PM
You need to do some experements to see how much power is available. This sounds like a great idea for free power. Put a brass gear motor or brass gear pump in the water line and use it to turn a generator to charge a car battery. Use the car battery and inverter to run lights or what every to see how much power is available.

This reminds me after graduating from college I got a job in another town and lived in a 2 bedroom apartment for about 1 year. One bedroom was my work shop with a welder, drill press, work bench, air compressor, tools and a large pile of stuff to build from. The air conditioner stopped working and it was 95 degrees outside the apt was hot as an oven. Management did not come check the AC for over a week the repair man said it tested good so there is nothing wrong with it. The AC unit would freeze into solid ice and no air could circulate management refused to repair it. I connected a 24"x30" x 4" thick radiator to my free apt water, I also had a brass gear pump in the water line to power a fan. I turned on the water and it worked great it cooled the apt down to 75 degrees all summer.