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jacee

Power from the pipes!

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The water system depends on the potential energy stored in the towers. That potential energy is used to pressurize the pipes. Letting the water simply drop out of the tower would be a waste of valuable energy. Using the energy to spin turbines would also be a waste of valuable energy.

A turbine in a tower does not change the pressure the column of water exerts on the system below. A turbine in the system itself does act as resistance, thus excess pressure is required. In this situation Lucid claims one pipe can generate 100 kwh of electricity from 5 psi of excess pressure.

Edited by Mighty AC

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A turbine in a tower does not change the pressure the column of water exerts on the system below.

It most certainly does.

Google "head loss" to learn about pressure drop in piping systems. Then google "head loss turbine" to learn about how it applies to turbines. This kind of stuff is usually taught in 2nd year fluid dynamics courses so people on this forum not being aware of these details is forgivable.

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In this situation Lucid claims one pipe can generate 100 kwh of electricity from 5 psi of excess pressure.

Yes, if there are systems with available excess pressure, then the potential energy associated with that pressure drop could be harnessed. That being said, if such systems are artificial (such as a tower), it would be more energy efficient to simply redesign the system to eliminate the majority of the excess (you want to keep a small amount of safety factor). It takes energy to get the water up into the tower, and while some of the excess energy could be harnessed with a turbine, more energy could be saved by simply not pumping the water as high in the first place. In areas where the excess pressure is available due to a natural (or dammed) reservoir at a higher elevation, the energy can obviously be harnessed, as is done all the time in conventional/small hydro systems.

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Google "head loss" to learn about pressure drop in piping systems. Then google "head loss turbine" to learn about how it applies to turbines. This kind of stuff is usually taught in 2nd year fluid dynamics courses so people on this forum not being aware of these details is forgivable.

A high school understanding of energy conservation of should be enough to understand that you can't get something for nothing. Simple deduction should tell anyone that any excess capacity is there to ensure system will reliably operate within design parameters. Attempting to divert this excess capacity would only compromise system reliability.

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It most certainly does.

Google "head loss" to learn about pressure drop in piping systems. Then google "head loss turbine" to learn about how it applies to turbines. This kind of stuff is usually taught in 2nd year fluid dynamics courses so people on this forum not being aware of these details is forgivable.

This is true, but the pressure loss associated with the turbine could be mitigated by installing said turbine on a bypass off the mainline, followed by an additional booster pump on said bypass prior to returning to the mainline. Of course, to prevent this from becoming a self-licking ice cream cone, the booster pump would need less of an electrical requirement then what is generated by the turbine……..

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A high school understanding of energy conservation of should be enough to understand that you can't get something for nothing. Simple deduction should tell anyone that any excess capacity is there to ensure system will reliably operate within design parameters. Attempting to divert this excess capacity would only compromise system reliability.

Simple high school understanding should show you that there is excess built into the supply system because demand changes hour to hour This system seems to just use up the excess and put it to good use..

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Simple high school understanding should show you that there is excess built into the supply system because demand changes hour to hour This system seems to just use up the excess and put it to good use..

So you are arguing that water that people don't need should be let out of the tower just to drive these turbines? Or do you know of some magic where you access this "excess" without releasing water that people don't need?

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Simple high school understanding should show you that there is excess built into the supply system because demand changes hour to hour This system seems to just use up the excess and put it to good use..

It doesn't work like that, during peak usage of the water system, as usage is increased, pressure is either reduced throughout the system (decreasing volume/flow rates) or requires additional pumps/compressors within the system to keep up with demand.....Once you start reducing any built in excess pressure, you not only limit future growth, but the ability to respond to one-off stresses to the system, like burst water lines or the need to fight fires....As Tim says, there is no free lunch.

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It doesn't work like that, during peak usage of the water system, as usage is increased, pressure is either reduced throughout the system (decreasing volume/flow rates) or requires additional pumps/compressors within the system to keep up with demand.....Once you start reducing any built in excess pressure, you not only limit future growth, but the ability to respond to one-off stresses to the system, like burst water lines or the need to fight fires....As Tim says, there is no free lunch.

Nothing to do with a free lunch. Just availing the available potential in the system designed to deal with fluctuations when the fluctuations trend downward.

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Nothing to do with a free lunch. Just availing the available potential in the system designed to deal with fluctuations when the fluctuations trend downward.

You're missing the concept.......when less water is used, less power is generated, at such a time pressure increases system wide.

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It most certainly does.

Google "head loss" to learn about pressure drop in piping systems. Then google "head loss turbine" to learn about how it applies to turbines. This kind of stuff is usually taught in 2nd year fluid dynamics courses so people on this forum not being aware of these details is forgivable.

Hmmm, maybe you can help me understand this a little better then.

I understand the concept of head loss, however not how the head loss in a vertical tower pipe would reduce the pressure the tower exerts on the water main below it. My understanding is that head pressure is only related to the height of the water not the volume in the tank. This is why towers use that ball on a stick design as more column height and therefor head pressure is maintained as the tower empties to replace volume during peak hours. At these times pressure in the horizontal water main line drops below the head pressure of the tower and the tower empties until the pressure in the main line at least matches the new head pressure of the tower. So are you saying that head loss in the vertical tower pipe actually lowers the head pressure of the vertical water column?

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You're missing the concept.......when less water is used, less power is generated, at such a time pressure increases system wide.

So when less water is used, less power is generated. Thats good, we all get that. When ore water is used, more power is generated. Pretty simple.

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So when less water is used, less power is generated. Thats good, we all get that. When ore water is used, more power is generated. Pretty simple.

So you do understand the concept, it didn't seem like that when you stated:

Just availing the available potential in the system designed to deal with fluctuations when the fluctuations trend downward.

Now do you understand that as more water is used, system wide pressure is also reduced, and would be reduced even further (or require additional energy to maintain pressure) when the electrical turbine is in use?

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So you do understand the concept, it didn't seem like that when you stated:

Now do you understand that as more water is used, system wide pressure is also reduced, and would be reduced even further (or require additional energy to maintain pressure) when the electrical turbine is in use?

Once again, there is a pressure differential between mainline and your tap. That differential is there to provide for demand changes. In between there is an excess which can be siphoned off and used to generate kws.

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So are you saying that head loss in the vertical tower pipe actually lowers the head pressure of the vertical water column?

Yes, definitely.

Consider what's actually going on. If you let a water droplet drop through air (or more precisely vacuum) from a reservoir from a certain height, all of its kinetic energy (mgh) will be converted to kinetic energy (0.5 mv^2). Now, imagine if you let that water droplet instead slide down a very long skinny pipe (which has high head loss). The water droplet will drop out of the bottom of that pipe very slowly compared to the droplet that fell freely, because it lost a lot of energy to friction against the pipe walls. You can easily try this experiment yourself with a thin tube of some sort. The effect is visually noticeable with a drinking straw but more obvious with a longer/skinnier tube. And pressure is nothing more than the force of particles moving at a certain velocity hitting a wall (or a control surface under analysis). Pipes are designed to minimize these friction losses, primarily by increasing diameter, reducing length, and making the walls smooth. However, no pipe is perfect, and the head loss even in a typical vertical pipe in a water tower is measurable.

But the head loss in a pipe is tiny compared to what would be produced by a turbine.

Consider again the idea of one water droplet falling. Imagine without the turbine it falls a height h, turning its energy into 0.5mv^2 as before. Now imagine that half way down the drop, it instead hits a turbine blade, essentially bringing the water to rest as the kinetic energy is transferred to the turbine (this is a decent approximation for how a turbine works). Then the water droplet falls out the bottom of the turbine and falls the rest of the way, from height 1/2 h, ending up hitting the bottom with only half as much energy.

Edited by Bonam

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Now do you understand that as more water is used, system wide pressure is also reduced, and would be reduced even further (or require additional energy to maintain pressure) when the electrical turbine is in use?

It is common for reservoirs to sit at a higher elevation than treatment plants. That water is gravity fed to the plant thus any excess pressure used to turn a turbine provides free electricity from previously untapped energy. This would occur prior to any pumping and pressurization for the water system.

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Once again, there is a pressure differential between mainline and your tap. That differential is there to provide for demand changes. In between there is an excess which can be siphoned off and used to generate kws.

Now you're babbling nonsense.......if you use every fixture within your home there is a significant drop in your domestic system......likewise if there is high demand on an entire city water system, pressure also is reduced citywide. :rolleyes:

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It is common for reservoirs to sit at a higher elevation than treatment plants. That water is gravity fed to the plant thus any excess pressure used to turn a turbine provides free electricity from previously untapped energy. This would occur prior to any pumping and pressurization for the water system.

Define "common".......how would such system work in a (near) flat elevation? In cases such as those you highlighted, or a gravity storm sewer, such system may have merit, but why not just build a hydro dam as mentioned?

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Now you're babbling nonsense.......if you use every fixture within your home there is a significant drop in your domestic system......likewise if there is high demand on an entire city water system, pressure also is reduced citywide. :rolleyes:

Talk about babbling nonsense! Anyway, before you make a fool of yourself again, why not wait to see the outcome of the Portland test phase.

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Talk about babbling nonsense! Anyway, before you make a fool of yourself again, why not wait to see the outcome of the Portland test phase.

By all means explain how your magical "pressure differential" works in a domestic plumbing system... :lol:

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It spins a flywheel hooked to a generator and makes electricity. But guess what, its not magic. Unless you want it to be.

You're describing a turbine, I'm asking you to describe this post:

there is a pressure differential between mainline and your tap. That differential is there to provide for demand changes. In between there is an excess which can be siphoned off and used to generate kws.

Explain how said "pressure differential" provides for demand changes........

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You're describing a turbine, I'm asking you to describe this post:

Explain how said "pressure differential" provides for demand changes........

Pressure on the mains is maintained at a level well above what eventually goes into your house to be ready for demand changes such as when everybody is in the shower in the am, or when they are sleeping at night. When you are not using your shower that unused flow could spin a wheel to make power.

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