I just read a little about water source heat pumps and am looking for more "real-life" info. What are the pros and cons? I live in N Mississippi where cooling is more of a concern than heating. We only have 3 months of winter, 1 of them the coldest it will get being say 10 degrees. The summers are REAL hot and muggy, humid. Advice? We haven't dug a well yet but I believe some around our property are running 200ft down, but we do have a 12 acre pond, say about 15ft deep in the middle if that could be an alternative source of water?

-- Sonya (clb@watervalley.net), March 21, 2001

Answers

Subject water sorce heatpumps

Sonya

There is an article this issue of Mother Earth. Haven't read it all yet but seems to have some good pictures. I've been installing ground source heat pumps for over 40 years and still think after the installation cost they are the most economical to operate. I?ll be glad to answer any specific questions you have. Below is a good explanation of a water source heat pump written by I Hank The physics involved is that all matter above absolute zero (-425 F approximately.) contains heat energy. By using materials with boiling points compatible with physics, refrigeration and heating systems can be constructed. R-12 or 22 freon, propane, anhydrous ammonia, and other coolant materials will work.

What happens is a compressor is used to cause the refrigerant gas to give up the heat and take on a liquid state in one heat exchanger coil. On the other side of the system the liquid is allowed to expand and take up heat, making things around it cold, and transporting the heat energy to the other coil for disposal.

An analogy is using a sponge to wipe up a water spill on the kitchen floor, then wringing it out in the sink.

By electric control of the valving to control the refrigerant the heat energy can be "pumped" outside in the summer and inside in the winter. Hence, the term "heat pump".

If you put the outdoor heat exchanger coil in a place that is relatively cool in summer and warm in winter, big system operating efficiencies can be realized. The constant ground temperature in the fifties accomplishes this.

The out door heat exchanger coil can be submerged in well water, running water or whatever natural source is available, or lately, simply buried five or six feet down in the yard. Whatever, the earth acts like a giant heat energy flywheel, making things level out if it is utilized properly.

Ponder the efficiency matters, of a system dumping heat into 100 degree air in A/C mode, or trying to soak up some heat from 10 degree air in heat mode...

Charles

-- charles gentry (cbgentry@mlec.net), March 21, 2001.

Sonya, I put a Water Furnace into my new house three and a half years ago. I love it. I installed it primarily for air con, also. Surprisingly, my house is so well insulated, that I have only had to use the heat pump for air con a total of five or six hours per summer (we have the advantage here in Oregon of having very cool summer nights, even when the days are hot, and I also installed a whole house fan, which enables us to start the day with a very cool house)

My unit has NO outdoor heat exchanger, as it takes its cooling and heating straight from fifty four degree groundwater. It's a three ton unit, and only costs 18 cents per hour to run. I've had no problems whatsoever. I'd recommend a copper nickel inside heat exchanger, especially for a place in Missouri, assuming that you have very hard water there. If you use well water directly, you may have to do an occassional acid rinse, and this type of exchanger will hold up to that better.

There are also heat exchange loops which can be used down inside a well, but don't need to actually extract well water. Also buried pipes are the most popular outside heat exchange method around here, but not as efficient as an open loop such as well water.

Your pond would likely be an excellent source for the water source heat pump, if it's that deep. Be aware, though, that the return water going back into the pond will be very hot in the air conditioning mode (very cold in the heating mode). You might want to spray it over the pond in a very fine mist to allow it to cool some, or your fish might get annoyed. Also, the return water might be ok for some crops. Might even make hot weather crops grow faster?

Initial cost was high, but my unit is almost 400% efficient, which means I'm using one forth as much power as I would be using if I were using resistance heating.

JOJ

-- jumpoff joe (jumpoff@ecoweb.net), March 22, 2001.

The reverse cycle airconditioner is a heat pump. The heat pump is a device commonly used for heating and cooling, that works by pumping heat from one place to another. This works by utalizing several effects of thermodynamics. In the the heat pump a voatile liquid called a refrigrant is pumped into the area to be cooled through a heat exchanger (usally a coil of pipes). The liquid experiences a change in pressure and exaporates, and absorbing energy.The liquid must absorb energy in order to become a gas and so sucks energy out of its surroundings and cools down.

This gas is then compressed back into a liquid. As this happens, and the gas is forced to become a liquid, it heats up. A gas has a much greater potential energy content than a liquid, and so as it becomes a liquid it realeases this potential energy and heats up. Effectivly the heat that was absorbed from the room has been now forced back out.

The refrigerant then looses this heat in another heat exchanger of coils of pipes, out side the area. In your case the exchanger would be imersed in your pond and you will use this to absorb the heat, from your house i presume.

The refrigerant once it has cooled back down, is then pumped back into area to be cooled, and experiences that same pressure change, through a expansion valve.

this cycle continues on and on.

I hope you have found this decription of the pysics involved use ful.

i am a yr 11 pysics high school student from Australia and i am doing a research assignment on the reverse cycle airconditioner at the moment, focusing on the pysics involved.

-- Wehner Von Braun (anonomous@fakeadresses.com), August 25, 2001.