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# Passive Electrical Generator

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Sorry...:)

I have to wonder about the economics and practicality of it though, googleing thermosiphon generators doesn't seem to turn up much (besides patent applications)...

I have no delussions of setting up my own power company/cooperative using this design. ;) However, I think i can build the system for a relatively cheap investment and from there it will continuously produce electricity. It won't power my house, but it will supplement my energy consumption and save me money.

Cold water doesn't want to rise. If you intentionally cool water below the level where you're heating it then you're loosing potential - certainly not gaining any.

~modest

I thought about that. I was trying to figure out if the pressure change in a closed loop would help mitigate the loss of potential. For every amount of water is rising at one point in the system an equal mass of water is also being pulled down at another point. This causes me to believe, although I admittedly have a novice grasp of the concepts I am delving into, that the gravity from one side of the system pulling down water will cancel out the gravity being fought at the other side of the system. Is this correct?

The idea of going into the ground was to create a heat sink so that water could be cooled in order to store more solar energy. If the difference between the temperature of the water entering the heating assembly and leaving the heat assembly is only 2 degrees Celsius, that will not produce as much energy as if the difference were 10-20 degrees Celsius.

Also, the hose on your diagram labeled #2 would need to have a one-way valve since the generator would offer resistance. Otherwise it would just use the one hose to try and reach equilibrium.

~modest

I figured a one way valve might need to be added there. That would create drag and cost potential energy, but it may not be able to be helped.;)

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I thought about that. I was trying to figure out if the pressure change in a closed loop would help mitigate the loss of potential. For every amount of water is rising at one point in the system an equal mass of water is also being pulled down at another point.

Yeah, I see where you're coming from. I think the problem you might find is that making it rise on one side will not automatically make it fall on the other side. A system like this would be perfectly happy heating the water at the top and never circulating that water back down.

As a convection system - it's completely open to pressure changes. If the pressure changes on the left side, that pressure difference is immediately felt on the right side. Something like a steam engine or an air conditioning coil or heat pump that uses pressure differentials has to completely seal half of the loop off from the other half at any given time which is different from a convection flow like you're going for. It might be best to think of water floating and sinking rather than pushing.

This causes me to believe, although I admittedly have a novice grasp of the concepts I am delving into, that the gravity from one side of the system pulling down water will cancel out the gravity being fought at the other side of the system. Is this correct?

I'm not exactly sure what you mean. Gravity will make the heavier water sink and the lighter water float which as you know happens because of temperature differences.

The idea of going into the ground was to create a heat sink so that water could be cooled in order to store more solar energy. If the difference between the temperature of the water entering the heating assembly and leaving the heat assembly is only 2 degrees Celsius, that will not produce as much energy as if the difference were 10-20 degrees Celsius.

Yes, it can. Absolutely. As your design has it:

The blue tank below the brown line I added (the ground level) is quite a bit colder than the water that's above the brown line. This means it will be relatively easy to heat water and make it want to float above point one. However, this also means it will be more difficult to cool water and make it want to sink below point two. As your system must circulate from point one back to point one in order to generate power, the colder temperature below point one and two cancel out.

In fact, it will work against you when the temperature at A and B start to equalize. You'll run into the situation where everything above the brown line is significantly warmer than everything below the brown line. In other words, the warm stuff is at the top where it wants to be and the cold stuff is at the bottom where it wants to be. The temperature difference above one and below one will be a lot as you say - but unless water wants to sink out of B, the system won't circulate.

Generally speaking, I think the following is a safe bet.

Starting with this setup (where a valve forces the water to move clockwise) [don't forget to consider gravity]:

This would be an improvement to efficiency:

And this would hinder circulation:

This was my thinking. But, I do think there are a lot of variables and what-not, I'm very open to seeing things differently.

~modest

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• 1 year later...

this is called an absorption refrigerator look it up on Wikipedia, there are no moving parts only a heat source. actually there is Einstein helped design one of these called the Einstein refrigerator. It is a simply system that is very efficient but is really limited on how cold u can make things.

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• 9 months later...

The design is fine, I question the output though. Consider 'potential energy' it can be expressed by a certain weight at a certain height. This energy can do work on your generator. A large tank water tank can receive passive water above the height of the water in the tank (just drop in). Then, The weight of say 1000 gallons in this elevated tank will produce a 'hydraulic head' at the bottom of the tank. this hydraulic head will produce the pressure you need to drive the generator. At this point you need to consider how much water is leaving the tank and how much is coming into the tank. With increased pressure comes increased flow. Obviously diameter of pipe is important, resistance by the generator and so on. My point is is that they'll need to be equal, if not you'll overflow or you'll lose some of your hydraulic head.

I'm upset no one could answer this before me, I had to make an account to comment- i don't like coming out of hiding! Good luck though!!

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The design is fine, I question the output though. Consider 'potential energy' it can be expressed by a certain weight at a certain height. This energy can do work on your generator. A large tank water tank can receive passive water above the height of the water in the tank (just drop in). Then, The weight of say 1000 gallons in this elevated tank will produce a 'hydraulic head' at the bottom of the tank. this hydraulic head will produce the pressure you need to drive the generator. At this point you need to consider how much water is leaving the tank and how much is coming into the tank. With increased pressure comes increased flow. Obviously diameter of pipe is important, resistance by the generator and so on. My point is is that they'll need to be equal, if not you'll overflow or you'll lose some of your hydraulic head.

I'm upset no one could answer this before me, I had to make an account to comment- i don't like coming out of hiding! Good luck though!!

Thanks for the input! Although, in the time between when this was dreamed up and now I have had two children and finding the time to tinker with this design and build a prototype has disappeared. Maybe when they are a little older :(

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