OU Pool heater?

[Steven Dufresne]

This is what I'm talking about, I guess it is powered by the sun.

http://www.heat-perfector.fr/

Check out their pump, and heat exchanger. These things put out a lot of KW. and the 30KW (37-6) is only 3 cubed. If something could only convert the heat to KW efficiently.. even 10 or 20% efficient.

The heat energy does come from the sun, but in an indirect way. The air around the unit is heated by the sun. This hot air is sucked into the unit and compressed. If you increase the pressure of a gas you also increase it's temperature. So the result of the compression is even hotter air. This hotter air is then run through a heat exchanger to transfer the heat to the pool water. There's a very good diagram of this on the above webpage.

This idea has been talked about for years in OU forums. The principle is much like using energy to pump oil from the ground. The oil contains potential energy in its chemical bonds. When you burn that oil you can get more energy out than you used to pump it out of the ground. In fact you can use some of the oil run the pump while selling the remaining oil. You're not creating new energy. The energy came from the sun to grow the plants, which eventually got buried and then compressed by gravitational energy to create the oil in the first place.

In the case of this heat pump, the sun heats the air and the air acts much like a fluid that stores this heat energy. The purpose of the pump is just to move the heat energy containing hot air from one place to another. So the amount of heat energy in the air can be greater than the energy used to run the pump.

The reason for compressing the air, to the best of my knowledge, is to increase the temperature so that the heat transfer is more efficient. The greater the temperature difference between the pool water and the hot air, the more efficient the heat energy transfer (someone correct me if I'm wrong.) There is no energy gain in this step. Work is done by the compressor.

A ground source heat pump uses the heat in the ground to heat a fluid which is circulated by pipes underground, or just takes water from a well. The ground is heated by the sun. The advantage here is that here in southern Canada, around 2 meters down, the ground is a constant 12 degrees celsius (54 fahrenheit) all year round. This constant temperature is true everywhere, although just what the constant temperature is will differ. The ground acts as a heat storage medium.

So potentially this could work. My understanding is it's the losses in converting that heat energy into a form of energy that can run the pump and then the losses in the pumping itself that have prevented people from making self-running versions.

And before stirling engines are brought up, a coffee cup stirling engine doesn't require much temperature difference but also isn't very powerful. More powerful stirling engines require a greater temperature difference to work which means the compressor will have to do a lot of work to create that temperature difference. But don't let that stop anyone from innovating. I'd love to see someone make this work.
-Steve
http://rimstar.org

[buzneg]

I guess the evaporation is cooling down the pool, or the pool cools at night, there must be a temperature difference for this to happen. Evaporation does create a temperature difference as well as carry vapour up against gravity.

[Steven Dufresne]

@buzneg,
Typically the solar pool heating systems heat the pool up to 100F. That's usually the maximum setting on their automatic control systems. Assuming that's the case then I'd guess that the temperature of the refrigerant coming out of the compressor in the heat pump system is significantly more than 100F, giving you your temperature difference.
-Steve
http://rimstar.org

[pauljohn]

Hi yucca,can you tell me the length of tubing used in your pool heating coil ?

[tadejstenta]

yucca

I have similar system at my home, but i´m not content with it. Somehow i get the air in the tubes (i think through pool water pump) and due the close loop of the PVC tube (aprox. 80 meters) there is almost no way to get it out of the tube.

I will made my self similar sun heater, but this time with old radiator for house heating. Hot water from radiator will heating up water boiler with clean water from pool inside. I had this system already set up past year, but due to poor performance (leaking radiator, sthiropor for back insulation-it melted, ...) i decided to rebuilt it. It was a good system and for comparison with other systems: radiators had 4 square meters - closed in wooden box, sthiropor insulation on back - down side, in upper side it was covered with clearness PVC foil. hen i pump water from house pipe in it in one side, on the otlet side water was almost to hot for shower. In the time outside was arround 28 deg.C.
Just want to share,
tadej