Need info on using water well for heat pump

Greetings! I found this site by searching for info on earth-coupled heat pumps. I read the following thread with great interest:

https://terrylove.com/forums/showthread.php?t=10403

I would like to investigate the possibility of using two water wells on my property as sources for one or two heat pumps. I don't have much information on the two wells yet. One is a dug well about 3 feet in diameter and depth of about 25 feet. The other is a drilled well of (as of yet) unknown diameter and depth. We get about 40 inches of rain per year here, so the water table is fairly high. Typically a drilled well here would be 100 feet.

I am interesed in getting more detailed information about this kind of system, especially in doing calculations similar to the ones in the above thread. Can anyone suggest any forum, books, or other sources of information? I am an electrical engineer and my brother has a PhD in physics, so between the two of us we should be able to follow any well-written articles.

I would like to install my own system, but even if I had someone else to do it, I would like to know as much as possible about it just to weed out the contractors who don't know what they are doing. I have talked to a contractor and a salesman, and it was obvious that they didn't really understand how the systems worked. The salesman told me that the contractors typically just went to a seminar and learned how to install a particular system, but didn't really understand how it worked. After talking to him for a few minutes, it was obvious that he didn't understand it either.

I would appreciate any information you can provide.

Brady

If you can use both wells you can save some pumping energy because you will be able operate between the two water elevations instead of between the water elevation and the ground level where you might discharge the water. If both wells are connected to the same aquifer you will not run out of water, and you will be taking heat from (in the winter) and adding heat to (in the summer) the earth within the aquifer.

If you reinject the water you should run a closed system so there is no oxygen available for oxidizing the dissolved iron that may be in the water.

You will need to know the amount of heat you want to gain (winter) and reject (summer), the amount of water the wells can deliver, and the temperature of the water.

I suggest that you NOT try to serve household uses and irrigation with the same pump as the groundwater heat source system. The heating system requires more sustaind flow at lower pressure and to try to serve both you get lousy matching of pump to requirements. You usually waste a lot of energy with the water pump for the heat source system.

You or someone should do a complete mass and heat balance for the system to make sure it will do what you require. Also, there should be an optimization analysis to determine the most efficient flow of water and size of heat pump system.

The water must be analyzed so you can select the necessary materials for the heat exchangers. You will have to deal with corrosion that can occur with some waters.

The pump should be matched to the pressure and flow requirements of the heat exchanger that will do the evaporating in winter and condensing in summer. You want the pump to be operating at the most efficient point without having to use a control valve to throttle the flow. Control valves on the water side to deal with a pump that has too much head will waste a lot of energy.

I suggest that you talk to vendors, get the data on the various elements of the system, draw up the flow diagrams, model it in Excel or some other program, and analyze it. You will need to get heat transfer data for the heat exchangers from the vendors. The model should include all of the temperatures on both sides of the heat exchangers, the mass flow rates, and power consumption. With EE and physics qualifications it should be easy. You can treat it like a thesis for a masters degree in physics.

Most vendors will offer undersize heat exchangers to minimize cost. You can do an economic analysis to determine the most cost-effective system.

Thanks for the response.

Does anyone else have anything to add?

TIA, Brady

I would recommend getting an air to air unit and forget all about a water to air unit. The savings if any are so minute in my experience and the maintenance is so much higher that it is just not a good idea to have one.

I had one years ago and being in the pump and well business found it more than I cared to take care of.

The entire unit does nothing more than put water and Freon (or whatever they are using now) in the same insulated package to help cool or heat the Freon using the ground water temperatures. This takes out or adds heat to the water which is discharged either to waste or back down a well. And as Bob NH pointed out, oxygen and well water can produce some nasty results when putting the water back into an existing well.

bob...

The climate difference between Florida and West Virginia makes the ground-source more attractive in West Virginia than it would be in Florida. Air-to-air heat pumps are a lot less effective when it gets below freezing where you need the most heat.

http://www.geoexchange.org/

http://www.geoexchange.org/incentives/incentives.htm

http://www.energystar.gov/index.cfm?c=geo_heat.pr_crit_geo_heat_pumps

The systems can also include some water heating by using the superheat from the compressor to get higher temperatures.

The water temp here in Florida is 72°. Michigan is 56°, so I would think WV would be around 60°. The heat in the water would be beneficial to a degree, but the added equipment needed to make the system work is just more to be maintained.

We have all been through the scenario of using the house pump to also run the irrigation and the heat pump. How we have a pump that is three times the size it would have to be to just operate the home. This is where the efficiency goes all to hell and the whole thing becomes a major headache.

For my money, I'll stay with a simple system.

bob...

What about just for air conditioning in MI in the summer? I have noticed the water from our new well is extremely cold. Would bypassing the boiler and pumping it though our pex in floor do any good?

I don't know if it would or not, but in Michigan you don't need Air Conditioning, it's either cold or raining all the time. That's why I'm in Florida.

bob...

MarkHash said:

What about just for air conditioning in MI in the summer? I have noticed the water from our new well is extremely cold. Would bypassing the boiler and pumping it though our pex in floor do any good?

Click to expand...

That is not a good idea. It would condense out the humidity onto your floor. You would have soggy floors and high humidity in the house.

An air conditioner operates the evaporator at a temperature lower than the final air temperature so it condenses the water vapor from the air and drains it away.

FWIW, I had a Geothermal heating system (Water Furnace) when I lived in Indiana 10 years ago. We used the closed loop design rather than a well, which is a massive amount of piping buried about 8 feet down.

It's a cool system but IS just a heatpump. We found that the third stage supplemental electric still popped on a lot more than we liked during the very cold months when the Geo just couldnt keep up.

In my humble opinion, Geothermal is awesome IF your house is tight & very well insulated. Our's was older and leaky and I had to do a lot of insulating to get the house to the point where the Heat Pump could keep up. I wouldn't get one again in a northern climate. If I lived in the midwest or south however? Definitely.

That being said, it is a cool technology and has probably come a LONG way in the 10 years since my experience.

On the pex in the floor issue: I have built several systems for radiant heat in slabs that automatically, with just the use of a check valve, push all the incoming cold water through the floor loops before entering the water heater. When heating, this moderates the incoming water temp and when not heating, it pulls some heat from the slab before hitting the water heater. Since we have little humidity here in California, its a great system with no electronic parts to fail.

I certainly would not suggest that you can cool a house this way however, unless you enjoy laying naked on concrete floors.

If you think about it, the world is upside down for GEO. When you live in Florida, you want to cool the home 9 months out of the year. The other three you want to heat now and then. In Michigan, you have to heat the home for 9 months and cool it for a few days during the other three. To cool you need cool water to be efficient and to heat you need warm water. Problem is, the water temp in my part of Florida is 72° and where I lived in Michigan the water temp was 56°. Upside down.

bob...

speedbump said:

To cool you need cool water to be efficient and to heat you need warm water.

Click to expand...

You don't need warm water to heat, you just need a heat source that is more efficient than the outside air temperature, i.e 56 deg is a lot warmer than 10 deg.

Rancher

True, but it's still upside down.

In Florida you have all that ********, so you can install solar electric panels on your roof to run your AC exactly when you need it.

Hmmm, wonder why that got censored out, I'm guessing it was ******** s u n s h i n e ...

Terry are you censoring our light now, or just trying to keep us in the dark.

Rancher