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jacee

Power from the pipes!

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The power inefficiency isn't deliberate, it"s a product of the need to deliver water.

You are imagining things. If the inefficiency existed then it would take a lot of energy to keep a water system running even if there was no demand. This is not the case. When demand is low energy consumption by the system drops to near zero. This is definitive proof that the "excess" that you imagine does not exist.

The energy is contained in the water in the reservoir that you don't need to maintain that pressure. It's there whether you like it or not. Reservoirs store energy as well as water.

And the only way to convert that energy to electricity is to remove water from the reservoir.

Whatever, all those cities going to this system and the companies building the components are idiots wasting their money because such a system can't work. Tim says so.

I never said it won't work. What I said is it would consume more energy that it produces if it is used with reservoirs that store pumped water. The engineers at the company are likely aware of this but the marketing people don't care - all they care about is duping a sufficient number of local politicians into believing that it saves them money by ignoring the cost of pumping water into the reservoir. And if your dogmatic rejection of the law of energy conservation is representative they will have no problems finding dupes. Edited by TimG

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All those cities have engineering departments but I guess they are all just stupid. I do concede that the usefullness of this system will vary with the characteristics of the water system involved and in some cases, not usefull at all.

You still don't seem to understand that reservoir size is dictated by the amount of water required by th community, not the energy contained within the stored water.

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I do concede that the usefullness of this system will vary with the characteristics of the water system involved and in some cases, not useful at all.

And this is the only point I wanted to make. When a city has a rain filled reservoir at high elevation then this system would work like any hydro electric installation. I personally believe that this is what the company means when it says 'gravity fed system'. The debate has been because you claim that a 'gravity fed system' includes water towers even though there is nothing in the online brochures to suggest that the company believes this is a valid interpretation.

You still don't seem to understand that reservoir size is dictated by the amount of water required by the community, not the energy contained within the stored water.

And what does that have to do with anything? Reservoirs store water/energy. If you want to access the water or the energy you need to remove water but you have decide whether you want the water or the energy. If you want the water you can't get energy from the system. If you want the energy you can't get water from the system. If you want both then the output has to increase to match the water and the energy demand.

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All those cities have engineering departments but I guess they are all just stupid. I do concede that the usefullness of this system will vary with the characteristics of the water system involved and in some cases, not usefull at all.

You still don't seem to understand that reservoir size is dictated by the amount of water required by th community, not the energy contained within the stored water.

Seems hes never gona get it.

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And this is the only point I wanted to make. When a city has a rain filled reservoir at high elevation then this system would work like any hydro electric installation. I personally believe that this is what the company means when it says 'gravity fed system'. The debate has been because you claim that a 'gravity fed system' includes water towers even though there is nothing in the online brochures to suggest that the company believes this is a valid interpretation.

I agree that this is more suited to a natural reservoir but it has more to do with the size of the reservoir than how it is filled. The pressure difference is a result of the difference in size required between maximum use and normal use. If the difference is not that great, there is a minimal amount to be gained.

And what does that have to do with anything? Reservoirs store water/energy. If you want to access the water or the energy you need to remove water but you have decide whether you want the water or the energy. If you want the water you can't get energy from the system. If you want the energy you can't get water from the system. If you want both then the output has to increase to match the water and the energy demand.

Because all motors operate on differential pressure. If you have a difference in pressure between head pressure and required line pressure you can use that differential to produce power. A foot of water exerts a pressure of .43 lbs per square inch. If you have a reservoir that has 1 ft more than the level required to maintain pressure in the mains, you have a .43 psi differential to exploit. That doesn't sound like much but if the reservoir is 10 sq miles you have 280 million cubic feet of water to back up that differential. That is a lot of stored energy. If the level of your reservoir varies by 50 feet but even at the lowest level it can maintain adequate main pressure, for much of he year you have a whole shit load of differential you can exploit.

Edited by Wilber

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If you have a difference in pressure between head pressure and required line pressure you can use that differential to produce power.

A pressure difference does not transfer energy. All it can do is facilitate the transfer of energy. In a pipe the transfer of energy is done with water motion and water motion requires that water be removed from reservoir. In the case of a natural reservoir we don't care about the energy required to fill so releasing some extra water to drive the turbines is not a big deal. In a pumped reservoir even a small incremental release of water requires energy to replace it - energy that will exceed any electrical energy produced.

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A pressure difference does not transfer energy. All it can do is facilitate the transfer of energy. In a pipe the transfer of energy is done with water motion and water motion requires that water be removed from reservoir. In the case of a natural reservoir we don't care about the energy required to fill so releasing some extra water to drive the turbines is not a big deal. In a pumped reservoir even a small incremental release of water requires energy to replace it - energy that will exceed any electrical energy produced.

The pressure difference is the reason you can transfer energy. Call it psi, ft/lbs or volts. Of course you remove water from the reservoir, that is why it is there and of course in a pumped reservoir you can't recapture all the energy you expended to put it there, you are just trying to recover some of the energy by using the differential between what is being used and the level required in the reservoir. There will always be a net loss, you are just trying to minimize it. Back to the regenerative baking. You put the energy into the vehicle when you accelerated it to speed, now you are trying to recover some of that energy by using the load of a generator to slow it down. Same thing.

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There will always be a net loss, you are just trying to minimize it. Back to the regenerative baking. You put the energy into the vehicle when you accelerated it to speed, now you are trying to recover some of that energy by using the load of a generator to slow it down. Same thing.

So tell me how much energy is required to keep a water system running if there is no demand for water? If you think it is greater than zero please explain why.

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So tell me how much energy is required to keep a water system running if there is no demand for water? If you think it is greater than zero please explain why.

None of course but why would you have a water system if there was no demand for water?

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None of course but why would you have a water system if there was no demand for water?

You misunderstood. How much energy would you have to put into a pumped reservoir water system that normally supplies a city if the demand dropped to zero (a hypothetical scenario but relevant). Edited by TimG

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You misunderstood. How much energy would you have to put into a pumped reservoir water system that normally supplies a city if the demand dropped to zero (a hypothetical scenario but relevant).

Relevant to what? How much gas does your car consume if it never leaves the garage?

Edited by Wilber

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Relevant to what? How much gas does your car consume if it never leaves the garage?

You are the one arguing that a pressure differential can produce energy. A water system with no demand has the same pressure differential. So how much "excess" energy can be harvested?

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You are the one arguing that a pressure differential can produce energy. A water system with no demand has the same pressure differential. So how much "excess" energy can be harvested?

No I'm not but exactly how do you think a hydro electric system works?

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No I'm not but exactly how do you think a hydro electric system works?

I know how a hydro electric system works. I am just trying to get you to see the logical inconsistency in your arguments. You probably realize that if there is no demand then no energy needs to be put into the system which means no energy can be taken out. Yet you seem to think if a little demand exists there is suddenly a bunch of energy available to be recaptured. That is not how it works. A little demand means only a little energy needs to be added to the system which means there little or no "excess" to recapture. Edited by TimG

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I know how a hydro electric system works. I am just trying to get you to see the logical inconsistency in your arguments. You probably realize that if there is no demand then no energy needs to be put into the system which means no energy can be taken out. Yet you seem to think if a little demand exists there is suddenly a bunch of energy available to be recaptured. That is not how it works. A little demand means only a little energy needs to be added to the system which means there little or no "excess" to recapture.

There is always demand from a water system but it varies and so wiil the amount of energy you can take out of it. In many if not most pumped systems, the amount of extra water in the resevoirs might not make it worthwhile but there many variables and every system will be different. How high is the source compared to the destination? Many systems are partial gravity where the source is higher than the destination but not high enough to provide adequate pressure so you still need pumps and reservoirs or towers. What then? All I know is that it will take some pretty smart people doing some pretty fancy calculations to figure out whether an energy recovery system makes sense for their water supply system.

Edited by Wilber

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There is always demand from a water system but it varies and so wiil the amount of energy you can take out of it.

The amount of energy put into the system depends on the amount of energy/water taken out the system. In a purely pumped system 'excess' at any given time is minimal no matter what the load. In a system where some or all of the water has been raised to elevation by weather/rain there will be some 'extra' energy that can be tapped but the amount depends on a lot of variables.

In many if not most pumped systems, the amount of extra water in the resevoirs might not make it worthwhile but there many variables and every system will be different.

I think we now agree.

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