Harnessing Energy from Water: Is it Possible?

[richie9648]

How much energy can you get from water? For example can you use a water mains safely to turn into energy? i.e. harness the energy somehow from the water in a pipe? Is it possible? Would you get much energy out of it?

 

[DaveC426913]

How much energy can you get from water? For example can you use a water mains safely to turn into energy? i.e. harness the energy somehow from the water in a pipe? Is it possible? Would you get much energy out of it?

I assume you mean the potential energy from falling water, like a hydroelectric dam, not like chemical or nuclear.

You could extract a little bit of energy on a small scale but you'd be tapping into the city's mains to extract it where a pipe went vertical. They'd frown on that. Especially since it would (by the nature of extracting potential energy) slow the progress of the water. Which they'd definitely frown on.

 

[rbj]

I assume you mean the potential energy from falling water, like a hydroelectric dam, not like chemical or nuclear.

i don't know of any chemical energy that can be had from water, but i s'pose a plant that extracts H₂O from some large body (like an ocean or Lake Michigan or something) and centrifuges for H₂O with one or both hydrogen atoms being heavy, and from that running some nuclear fusion reactor, that might be in the cards with acheivable technology someday. i don't think it is now.

 

[RonL]

In most cases a city has a water tower, they buy electric power to run the pump that fills the tower in order for you to have pressure on your main, pressure alone would leave you far in the hole.
Now if you talk the city, into a system where pressure, and heat would be used, then in a closed loop system using both forms of energy might be worth a look? ( a micro-geothermal system)

 

[richie9648]

What about the mains and pipe that run underneath a road - is there a sufficient temperature difference for thermoelectric energy or a turbine in the main or any other types of ways to harness some sort of energy...

 

[RonL]

Well i didn't think about how much i'd pay to heat the ice cold water that comes into the hot water heater

 

[K.J.Healey]

Richie any energy you could pull from the moving water in a pipe leads to it slowing down, which means the city has to put more energy into it to keep the pressure up.

Is there free energy to be had? Yes for the first few who do it, but it is a small amount anyway. And as soon as the city sees the drop they'll just increase the cost of water to be able to pay to increase the energy of the main.

 

[richie9648]

I have good links with the water company - so if i had access to the main and the pressure was sustained to the customers at the same time - i could do something with flow/pressure?

 

[allanworks]

it is un feasible to split h2o into its componets just to burn h2 for energy it takes twice as much energy to split the h2o into its componets that's why all water to hydrogen fuiling stations run on solar power if they were conected to the power grid electric prices would skyrocket

 

[K.J.Healey]

I think he's talking about stealing energy from the pressure in your water lines, not electrolysis.

But richie, let me stress, while in theory you WOULD get energy out of the system, it would be minimal. Look at these points:
1. To get the energy water would have to be constantly flowing == money.
2. The small time you do run water consider this:
How much energy do you think is required to push water through your pipes at the rate it comes out at? I figure I can get an electric pump that's quite small to do the job, and only run it at a medium pace. Thats not much energy requirement to do the work. Then look at it backward, that's the maximum energy you could ever possibly get out. Enough to charge a a couple of D batteries most likely. Not enough to consider building anything to harness.

 

[richie9648]

Lol - i am not talking about stealing energy or doing anything illegal! It is just a science project we are doing and one idea I came up with was around using the flow of water in pipes - e.g. use a turbine in the pipe to create some type of energy output - yes it would reduce the pressure but if the main was 12" or bigger it would not affect customers especially if its a mini turbine.

 

[russ_watters]

It doesn't matter how small it is, it is still stealing energy from the water company. Water companies have enormous electric bills due to the energy it requires to pump that water.

Now if you wanted to do it in your own home, sure, you could, but I suspect the electricity you got would cost more than from the wall socket due to the cost of the water that you are pouring down the drain.

 

[Dale]

You can easily get enough energy to wind up your garden hose!

http://www.no-crank.com/

Energy is pressure times volume, and you can build devices that are reasonably efficient at converting the energy in the water into mechanical work. As russ mentioned it is a net energy loser and a net money loser as well since most of the hydrodynamic energy in the water was added by electric pumps.

 

[allanworks]

Sorry About My Earler Post Read Rbj's Post About H20 And Wanted To Throw My 2 Cents In Well About The Subject Cant You Take A 12 In Main Put Let's Say A 1 In Fitting On It Wich Would Make The Speed And Pressure Far Grater Hook Up A Small Water Pump Backwords Like You See On Old Well Pumps Then Reverse The Power Connection On The Moter So That It Feeds Power To The System Instead Of Taking Away That Should Produce Quit A Bit Of Power Or Just Hook Up A Small Turbin
On Another Not Woudent The Pressure Be Able To Cut A Man In Two

 

[russ_watters]

Capitalizing the first letter of every word makes your post extremely difficult to read. Just fyi, this isn't like other forums - we prefer people to speak proper english.

Anway, no the pressure in a city water main isn't so high that it could cut into you. That's something that can happen with high pressure boilers, but they run at a good 10x the pressure of a city supply main.

 

[DaveC426913]

Lol - i am not talking about stealing energy or doing anything illegal! It is just a science project we are doing and one idea I came up with was around using the flow of water in pipes - e.g. use a turbine in the pipe to create some type of energy output - yes it would reduce the pressure but if the main was 12" or bigger it would not affect customers especially if its a mini turbine.

Keep in mind that this is not waste energy you are collecting. The purpose of these water lines is to keep water moving efficiently, which would be directly counterposed by your system. It's not quite the same as taking energy of a source that is otherwise being wasted, such as a lake or river at altitude.

 

[allanworks]

sory about the capitalizing and misspelling i did not graduate high school but don't forget that you are forcing the pressure and mass for a 12in pipe main threw a 1 in hole which would give it a lot of force

 

[russ_watters]

No, pressure is pressure - the size of the hole doesn't affect that.

 

[allanworks]

think of it like your garden hose when you close the tip almost all the way you get a jet stream that is more powerfull that can blast dirt away with the right tip on a garden hose you can pierce skin i now i got a skar on my back because of one

 

[DaveC426913]

think of it like your garden hose when you close the tip almost all the way you get a jet stream that is more powerfull that can blast dirt away with the right tip on a garden hose you can pierce skin i now i got a skar on my back because of one

You cannot extract more energy from a garden hose with a small hole than you can from a garden hose with a large hole. You will not fill your swimming pool faster with a smaller hole.

Nor can you extract more energy from a water pipe regardless of how big or small a hole you make in it.

I can't break your skin using my thumb but if I tape a thumbtack to my thumb I can break your skin. I've have not used any more energy, I have merely concentrated what energy I have available on a smaller point.

 

[allanworks]

i wasnt saying it right but you got what i ment dave thank you

 

[RonL]

I believe what allenworks is trying to say is the same as what i do several times a year, with a bird bath in the yard. My water pressure is right at 50 PSI (static) and on the water hose there is a pistol style sprayer, when adjusted to a small high speed stream, will blast the water out of the bird bath in a shorter time than it takes to refill the bath after removing the pistol nozzel, and letting the water flow at full open thru the 5/8" hose.
I have never checked with gauges to see what pressure is in the hose end during each condition, but it can't be more than 50 PSI.

 

[DaveC426913]

I have never checked with gauges to see what pressure is in the hose end during each condition, but it can't be more than 50 PSI.

Exactly.

 

[DaveC426913]

i wasnt saying it right but you got what i ment dave thank you

?

But I refuted what you said.

 

[allanworks]

i was agreeing with your analagy .thats what i was trying to say but my adhd screws me up when i try to explain things pushing that same pressure threw a smaller fitting would produce a smaller but faster and more powerful streem which can cut a man in two

 

[russ_watters]

I'm not sure if he was quite clear there. There is a maximum pressure in the pipe. When the pipe is open, the pressure drops through the pipe to make the water flow. Putting your thumb over it creates a restriction to make the pressure in the pipe uniform at its maximum. Creating a smaller restriction won't increase the pressure above the pressure generated by the pump.

So you can't cut a man in two unless you have a pump that is generating an enormous pressure. You can't do it by putting a restriction on a garden hose.

 

[W3pcq]

This basic hydrolics isn't it. This is why you can use water to lift cars and stuff. Bigger piper to smaller pipe means more pressure per square inch. This is why you can push a lever down pressing a piston into a cylinder full of water with a reducer equiped with a piston and a man can lift a 2000 lb car. Right?

 

[RonL]

Basic hydraulics is right. as stated my (static) pressure is about 50 PSI, and from past experience i know that with an open hose, about 5 gallons per minute will flow at a much lower pressure (30 PSI ?).

One Horsepower is equal to a flow rate and pressure of 1GPM@1500 PSI. ( 745.7 watts for electric )

You can mix and match anyway you like. To get 1500 Psi, you need 50 times more piston area, but you have to cut delivery rate by 50. Finding the right type of water pump, will let you turn the motor( DC ), and produce a (very) small amount of electricty.

 

[Dale]

Bigger piper to smaller pipe means more pressure per square inch. This is why you can push a lever down pressing a piston into a cylinder full of water with a reducer equiped with a piston and a man can lift a 2000 lb car. Right?

It is the same pressure (force/area), but since it is delivered over a different area the force is different. If you push on a 1" piston with 20 lbs of force then you have 20 psi. If your piston is hydraulically linked to a 100" piston then 100" * 20 psi = 2000 lbs and you can lift the car.

This is a force multiplier, not an energy or power multiplier. If you move your piston 10" then the car will move no more than 0.1". That results in the same work, just split differently between force and distance.

 

[russ_watters]

This basic hydrolics isn't it. This is why you can use water to lift cars and stuff. Bigger piper to smaller pipe means more pressure per square inch. This is why you can push a lever down pressing a piston into a cylinder full of water with a reducer equiped with a piston and a man can lift a 2000 lb car. Right?

No, no, no, no, no, no, no, no, NO!.

Please read what is being said. I'll say it again: pressure is pressure. If a pump generates 50psi of pressure, then the maximum you can get out of its pipe is 50 psi of pressure. Creating a restriction does not increase the pressure above the pressure generated by the pump!

Hydraulics uses area to generate a large force with a relatively small pressure. Force is pressure times area. So to lift a 2000 lb car with a pump that generates 50psi, you need a cylinder with 2000/50= 40 square inches of area. Yet with 50 psi in a garden hose, you can probably completely close-off the hose by squeezing your thumb onto it.

 

[DaveC426913]

The issue here is that PSI is NOT the basic unit of force that will power your device. i.e. PSI is IRRELEVENT.

A 50PSI garden hose is 50PSI whether the hole is 1 square inch in area or 0.01 square inch in area. (Do the math). No matter how large or small a hole you put it through, it will still only do the wsame amount of work. And THAT is what is going to power your turbine.

Look at it this way. Say, your turbine has blades that are 1 inch in area. We apply 50 pounds of pressure to it to get it to move. If we apply that 50 pounds across the WHOLE blade (i.e. with the garden hose wide open) or if we apply it to the blade in a tiny area (i.e. fast moving stream that could give you a nasty blister), it will still push your turbine just as fast.

 

[uart]

I'd like to get back to the original question.

How much energy can you get from water? For example can you use a water mains safely to turn into energy? i.e. harness the energy somehow from the water in a pipe? Is it possible? Would you get much energy out of it?

If you are prepared to suffer some loss of pressure then yes you could extract some energy from your home water supply. Let's work out how much.

Typical domestic water mains pressure is 50 to 75 psi, so let's assume you are willing to suffer a 25 psi drop in delivery pressure. The theoretical work that can be done with that is equal to the pressure drop times the total volume of water passing (using SI units).

For the sake of a "ball park" calculation let's assume that your daily water consumption is 700L (0.7 m^3) then the available energy at 25 psi (approx 170 kPa) is 0.7 * 170k which is approx 120 kJ (kilo Joules). I don't know the overall efficiency of conversion (turbine plus generator) but I doubt it would be more than about 30%, so for the sake of having a numerical solution let me take a conversion efficiency of 1/3 (btw if this figure is way off target then hopefully someone can pitch in with better info). So in this example you could expect to extract maybe 40kJ of energy per day.

To put that into perspective divide by 3600 to get about 11 Watt-hours per day, that is a 24hr average of just under half a Watt continuous (0.46 Watts). Now your energy company probably sells you power at about 20 cents a kW-Hr but if you produce surplus energy and sell it back to them they'll probably pay you about 5 cents a kW hour. At this rate you would make a whole 5 cents every 3 months of generation. Hardly very impressive, especially if you consider that the turbine and associated plumbing would probably have a high upfront cost and the adverse effect on your water pressure making your bath tub fill slower and your hose spray weaker etc etc.

BTW. A cheap 10cm x 10cm solar panel would produce more energy per day in most geographical locations and it would probably cost between 10 and 100 times less to implement.