Mains pressure - > Electricity

coolemon

I have been looking at 'ram pumps' on youtube. They pump purely on the force of water coming from the other end - http://www.youtube.com/watch?v=wIuab-xc_KI&feature=related

So I was just thinking, could a device be constructed using the force of mains water from, say, an outside tap be used as a kind of mini hydro generator or a ram type system which can convert the water pressure into electrical energy?

A sort of adapter which plugs onto an outside tap like a hose does.

Kind of 'parasiting' off the pumping station/gravity which supplies mains water.

mawk

it wouldnt be crazy to built a system to spin a dyno from a tap. buuuuuut when do you have running water but not electricity?

I just played some rough guesswork calculations for it and assuming about 200 ml/s which is what my tap does; I get 5.8 watts, assuming a total generator efficiency of 10%. at such small size the friction losses will be a killer.

so even assuming im an order of magnetude off and its closer to 50w.. thats still not much. not even enough to charge my laptop. enough to charge a phone I guess, but pv cells already do a less wasteful job of that. and with the incomming water metering, esb will be cheaper

i wouldnt hurry to dragons den

Bruthal

mawk wrote: »

it wouldnt be crazy to built a system to spin a dyno from a tap. buuuuuut when do you have running water but not electricity?

I just played some rough guesswork calculations for it and assuming about 200 ml/s which is what my tap does; I get 5.8 watts, assuming a total generator efficiency of 10%. at such small size the friction losses will be a killer.

so even assuming im an order of magnetude off and its closer to 50w.. thats still not much. not even enough to charge my laptop. enough to charge a phone I guess, but pv cells already do a less wasteful job of that. and with the incomming water metering, esb will be cheaper

i wouldnt hurry to dragons den

I wouldn`t think them calculations would be too far out, all you would manage is to light a few led`s probably.

Even if a pump house itself had a turbine generator at its water output, the extra power the pumps would need to power the turbine as well as the normal water pumping function would be more than the generator would output.

And exactly as said, imagine the cost of the water when the metering comes in, just to get a few watts.

bnt

Just to clarify something in the OP, assumed in the other posts: you're not going to get anything from pressure alone, since no Work is done that way. It would be like static electricity: lots of voltage but no current. The water would have to flow, and you'd be aiming to capture some of the energy released that way.

Rough calcs: say the water had a pressure head of 10m* at the tap, and you use all of that for generation, then you can use the potential energy formula (E = mgh) to calculate the theoretical energy released: for 0.2 kg/sec you have 0.2 * 9.81 * 10 = 39.24 W (J/sec). Maybe you could do a bit better than 10% efficiency, but it's still not much to show for 17,280 litres of water a day ...

* Dublin City Council says their mains are at 12-15m pressure head, and I assume some is lost on the way to the tap.

Bruthal

bnt wrote: »

Just to clarify something in the OP, assumed in the other posts: you're not going to get anything from pressure alone, since no Work is done that way. It would be like static electricity: lots of voltage but no current. The water would have to flow, and you'd be aiming to capture some of the energy released that way.

Rough calcs: say the water had a pressure head of 10m* at the tap, and you use all of that for generation, then you can use the potential energy formula (E = mgh) to calculate the theoretical energy released: for 0.2 kg/sec you have 0.2 * 9.81 * 10 = 39.24 W (J/sec). Maybe you could do a bit better than 10% efficiency, but it's still not much to show for 17,280 litres of water a day ...

* Dublin City Council says their mains are at 12-15m pressure head, and I assume some is lost on the way to the tap.

Also a 2 or 3 meter head of water could do far more work than a 15 meter head once there is a high volume, such as through a 1 meter wide pipe. There wont be a very high volume from a tap even if the static pressure is nice and high.

Dardania

the fundamental problem is that the water needs to flow...so unless you have a use for that water you're at nothing...maybe use it as chilled water in an office AC system?

WHat you really want to do is use the power available down a PSTN telephone line...

mawk

Dardania wrote: »

the fundamental problem is that the water needs to flow...so unless you have a use for that water you're at nothing...maybe use it as chilled water in an office AC system?

WHat you really want to do is use the power available down a PSTN telephone line...

google kip kay on that one.

you could also use the cold water on hot days to run a stirling engine and run some sort of generator/dc motor off that