Generating electricity using household water pressure

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Infamous Outfamous

It's not free. The energy extracted means that the rate of flow through your 'generator' is slightly reduced, depending on the ratio of conversion. Either way, the water company must then increase the pressure to maintain flow because of your power drain on the system - granted, this may only be a small amount, but it is a drain nonetheless. Anyway - long term view is, if everyone starts doing it the Energy the water company will need to push water will be greater, they will have to invest in stronger materials and joints to cope with the backpressure now powering everyone's generators and yes you guessed it, that fee we pay for the water will grow exponentially. We don't get free 'leccy, just a higher bill. - so you're better off building a water tower to collect rainwater and create a mini hydropower-station. Then you've also got some free water for the washing machine, garden etc.
 
Infamous,

If you read my first post, we don't have reliable water companies in here (Brazil is the country of the future for about 200 years, and it seems that we're finally getting there, just some more decades :D ), and have to ration water (tough most people just wastes it to wash the damn walkway instead of using a freaking broom, really pisses me off seeing them pushing one leaf away with water, so lazy), we don't have water from street 24/7, so every construction has it's own water tower. The pressure don't come from the company, it's from the "stock" of water every building must keep.

I know it's better that the company plans and keep a constant service, but it's an old "habit" and many people would be without water because of the old "leeches" who have to fill their stock. As well as it could use it's floodgates to generate more energy cheaper than a building.

In Robert's outdated approximation(2 years and a half ago, damn inflation), we would save $3,29 per year per house from common use.

So it's a scenario where you must keep a stock of water on top of the building, with 100+ apartments or offices for 1000+ employees (very common scenario around here), with a very suitable laundry on the basement(residential).

In a larger scale could it work?

PS. I'm not one of those "save the planet" freaks, so I know if it's not profitable, it's useless because it's wasting resources. I'm pretty skeptic about their green solutions, unfortunately most of them are composed by a huge waste of resources.
 
Look, if you have water in a hose under pressure, with a nozzle on the end of the hose and that nozzle is closed, then the pressure doesn't do anything. The only way the pressure does something is if the nozzle on the end of the hose is opened and the water flows out of the nozzle.

So, the only way to derive work from pressure is for there to be flow, and if the water is flowing through a device driving a generator then the pressure on the outlet side of the device driving the generator will be less than it was going into the device driving the generator. And, the flow must be relatively continuous to produce a reliable electric current. Think of how many minutes or hours/day that water is flowing in a typical household, and that just isn't very much.

And, because there will need to be a pressure decrease on the outlet of the device driving the generator then the water "pressure" will be much less useful. (Think of a dribbling shower or a tub that takes an hour-and-a-half to fill.)

If you keep the water flowing through the device driving the generator and dump the water down the drain (which would be a <b>huge</b> waste of water!), then all you're doing is using the water company's pump energy, transmitted through pipes, to a generator to convert the electricity driving the pump back into electricity for some other purpose. But, remember, the water company had to use energy to pressurize the system to provide the flow that people need, or even to fill the tanks on the tops of houses and buildings in many parts of the world.

Now, I'm interested in hearing much more detail about the poster who said he's using a relief valve in some kind of two-stroke motor configuration to produce power with household water pressure. But, I'm not holding my breath, either.
 
S
He said he did it without any flow, IIRC, which means it's not possible. Either he's dumping some water, or he's got the "output" interconnected to some real source of power that's illuminating a light or something and he's taking that as proof that his scheme works.
 
Looking at all of this, it gave me an idea. I'm not saying that this is cost efficient yet, but its something to think about.

I had an old 125 gallon fish tank with a decent pump that moved A LOT of water 24/7 just recycling it. IT got me thinking about an energy efficient pump that was circulating the water and collecting electricity.

A pump that requires 5Watts of electricity can move about 80GPH. A 10Watt pump will move 160GPH.

I don't know if this helps or gives anyone any ideas, but its a thought.

Here's a link to a few pumps. There might even be more energy efficient ones available. This was just a cursory glance. http://bit.ly/hE2GAX
 
R

Robert Scott

Rishard, I'm not sure what you are proposing, but it sounds like you are saying that you could move the water with the electric pump and then extract energy from that moving water. If that is what you mean, then that would violate the laws of thermodynamics and would be equivalent to a perpetual motion machine. The fact is no matter what you do, you cannot get more energy out of a system than you put into it.

As for the fish tank pump, the amount of water it circulates might sound impressive, but the pump is only capable of circulating that much water because there is little or no back pressure to the flow. To extract energy from a stream of water you need to create more back pressure.
 
On a somewhat related topic, I had an idea for using water pressure as an energy storage medium. Imagine an off-grid residence with solar and/or wind power and a well for water. When The panels or wind turbine produce electricity in excess of what the house is using, a pump in the well turns on to pump water up into a cistern. When the load from the house exceeds the output from the wind and solar sources, a valve in the cistern opens, allowing the water to drain back down to the well, flowing past a water turbine to produce more electricity in the process.

Naturally, there is no free energy there, and you would actually lose some energy due to the inefficiencies of all of the components involved. Basically, the whole cistern / water pump system would be a replacement for a battery system. Any ideas on how big the cistern would need to be?
 
S
"Any ideas on how big the cistern would need to be?"

BIG! One KWH is equivalent to 2.65 million ft-lbs, so you would need to raise 2.65MM lbs of water one foot, one lb 2.65MM feet, or some combination.

Lets assume your cistern is 100 feet above the well water level. You'll need to move 26500 lbs or 3200 gallons of water to store 1 KWH. And you probably use 30-100KWH at your house in a typical day.

You seem to have a much better grasp of where energy comes from and when you're storing it vs making it than the others who've posted.
 
Google Pumped storage....

Haven't fried my brain reading the entire thread, but power in water is just like power with electricity.

power = flow X pressure
power = amps X volts

Since most here deal with electricity I'll ask this question. Can you run a pump and move water using household voltage for free? Why can't you just use the voltage to spin the pump motor and not use any current?
 
Z

Zacharia, Tomy

Regarding the energy storage model. Also look at the efficiency of the motor-pump combination. In the 5 KW range, it can be 20-25%. (roughly 30% for the centrifugal single volute pump and 80+ % for the motor). Higher sizes definitely have higher efficiencies. Then cost of high efficiency systems is an issue.

Regards,

Tomy Zacharia
 
why couldn't the city or electrical company put micro turbines in the water pipes for each block or neighborhood, if there is one branch of the water pipe that serves 20 houses the water flow for 1 year would be 20x and instead of 60 years to make up the $200 turbine it would be 3. This would barely lower water pressure at all. also no water is wasted because all water that flows through the pipes is going to someone's house.
 
B
Because it would be more efficient, if they don't need the pressure, not to develop it in the first place.

Power in W = pressure drop in Pa x volume flow in m^3/s = .05 x drop in psi x flow in ft^3/s

Or perhaps we can run a pump to push water up to the top of a hill, stick a turbine in a line, and use the turbine output to power the pump.

Bruce
 
Regarding the pumped water energy storage post, this is actually already done on a grid size scale in many places. Here in Colorado, we have at least one location run by the XCEL Electric utility up in the mountains where 2 reservoirs, probably about a square mile each, are linked with a turbine/pump arrangement. During off-peak load times, energy is used from the grid to pump water up into the upper reservoir from the lower reservoir. During peak load times, water is allowed to flow down through the turbine to generate peak power. This makes economic sense because even though there are energy losses in the system, the peak power generated is financially worth enough to offset the financial cost of pumping the water up using off-peak energy.

I don't know if the same economics could apply to an individual sized installation unless your peak power costs were extremely high, or you were completely off the grid and needed energy storage, in which case it would have to somehow beat batteries in cost and performance. Batteries are pretty hard to beat, but maybe in some cases with natural geography working to reduce capital costs and no regulation problems it might be feasible.
 
G

Get A Grip People

I highlighted your mistake. In order to get useful energy you need either a large flow or a large pressure drop or both. Arguments about "I only want 100Watts" are spurious because that's quite a lot of energy.

This discussion refuses to go away but really it's quite simple ...

<b>You cannot get something for nothing</b>. Any energy you try to get from household water must be the excess energy that the water company left in there to keep the system working reliably. Even if there is plenty of excess energy, its still not very useful if you want to run more than a couple of LED's. On top of this, you typically have to pay for the water you use.

You will also notice that the only people who keep asking this question also profess their complete ignorance of the science involved. EVERYONE who understands the basic school physics tells you its possible but is a total waste of time, effort and money.

Can we please stop trolling this question every few months and go do something useful instead.
 
M
I find this message thread very interesting. I recollect a couple of items from my past. A book was written about me and a few other people that changed the world of lighting. Whenever somebody told me something could not be done I made a point to prove them wrong.

I was confronted by some very senior scientists in the world of physics and told that what I wanted to do could not be done - I found it funny to be sitting in front of the person at the Department of Energy 6 years later that was in charge of creating a USA testing system to qualify "what could not be done". I also remember sitting in front of the man from California Energy Commission who told me that what we wanted to do could not be done - now it is on every Home Depot and Lowes shelf.

I love the challenge you all present here. I get excited about working with a bunch of smart folks to solve these type of questions. I have not failed yet.

The world was once flat folks, but not anymore...but boy did it take a few brave people to brave the train of thought.

Arsenic killed everything, but not anymore, Nasa showed us how things on earth live off it.

The gentleman from Brazil makes some good points - there is a much bigger world than just the USA folks - I lived in New Zealand this past year and while energy prices where only $0.12 KWHour - relative to a person's income it was equivalent to $0.40 KWHour in the USA. I also heard constant stories about parents teaching their kids to take 2 minute showers.

I also think the gentleman creating the 2 stroke motor idea is not a bad one - you all are just focusing on available pressure of water and on water waste.

Take a step back folks and re-read this whole post. The answer for how this can be easily done is right here in all the words.

Would be fun to show you all in the coming year how we will do this.

Last night at an event in Las Vegas we introduced our LED light tube that replaces fluorescent tubes, it pays for itself in 3 months...
 
N

Namatimangan08

First of all you find the average of the stream flow (Q_avg). Next determine firm stream, i.e. stream flow (Q_firm) that has exceedance probability of 98%.

Then you have to find optimal pressure gradient line. Normally we should be looking for the highest pressure gradient between two points along the stream path, such as water fall.

I think I will let you to calculate the cost to install it. I will show how to calculate the return. I will show you how to determine the firm and the average return.


1. Firm return, E_f(kWh/annum)

E_f =0.80*0.90*Q_firm*H*density *g*365*24*3600 J

Note that 3.6million Joule =1kWh

2. Average return

Same as 1 above except that Q_firm shall be replaced by Q_avg

The first and second constants, 0.80 and 0.90 represent overall conversion efficiency from potential to electricity and availability factor of the proposed turbine generator. H should be in m and the others are in m-k-s

Over long run you can expect to get E_avg but you shall anticipate to get only E_firm for at most 3 consecutive years. E_avg always greater than or equal to E_firm.

I hope this post is helpful.
 
In reply to Manuel Lynch: With regards to water driven piston engines (as opposed to turbines), that isn't a new idea. They were widely used in Europe for industrial power in high head applications in the 19th century but were eventually replaced by turbines (and electric power) due to the better efficiency and reliability of turbines.

As for the person who in January said he was using this, I think a bit of skepticism about his claims is in order. He said he was running this 24/7 without wasting water, but didn't provide any details as to how he did this. Where did the water to run the engine go when he wasn't using it for anything else?

He also said he as using "a small bike generator" to run "a pc, tv and a refrigerator". A typical bike generator outputs about 5 watts. As to how you run "a pc, tv and a refrigerator" on 5 watts would be something that I'm sure we would all like to know. Without any details on that, I'm a bit skeptical.

Here's some typical electric power usage figures as an example (in kw-hours): PC (1248), television (350), refrigerator (2700). The total for those would be: 4298 kwh.

A 5 w bike generator running 24/7 could produce: 5 x 24 x 365 / 1000 = 43.8 kwh. That's 2 orders of magnitude less than what the appliances consume before we even account for the losses involved in converting 5 VDC to 120 (or 240) VAC. It's possible to quibble about actual consumption patterns or appliance sizes, but I doubt those would amount to 2 orders of magnitude of difference.

So, when someone tells us he can generate useful amounts of power from his kitchen faucets, I think we are entitled to say "show me the numbers!"
 
N

Namatimangan08

> I would like to know, if a house used the water that went down its drains in a
> year, to turn a generator...how much electricity would it produce? enough to
> power the house?? thanks for your time..

Look in bigger perspective. Probably there is an opportunity to set a power plant.

Assuming your township is located 100m above sea level. It is possible to collect used water and natural drainage and channel them to a man made reservoir. Then you can use this water to run a conventional hydro power plant.

This approach is the most likely hood to success.
 
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