# From ice cold to ice

Discussion in 'Geothermal Heat Pump Applications' started by NDGeo, Mar 9, 2016.

1. ### NDGeoNew Member

I'm new, so howdy to everyone. : )

Here's my idea, though I understand very little on this subject. We live next to a river. That river freezes over and is below say 40 degrees Fahrenheit for six months of the year.

The kids play ice hockey and we'd like artificial ice refrigeration to extend our season, both at the beginning and end of the year. We can't skate on the river due to access issues via steep banks and the threat of currents causing thin ice. It also cracks and heaves. Therefore, we skate on the land just next to the river with some wind shelter from the trees.

My idea is to put a large water tank in our garage, which is right next to the skating area, and pipe water to it from the river anytime the internal temperature rises above say 40 degrees Fahrenheit. The water pipe would be buried underground and would reach out into the river under the ice cover.

At the other end of the system is PEX tubing running under the ice in grids with propylene glycol at a temperature of 18-20 degrees Fahrenheit.

So, the middle of the system, where the magic happens, would be a heat pump that would take advantage of coils running in a closed loop system in the 40 degree and below water tank to pull heat out of the propylene glycol keeping it at 18-20 Fahrenheit.

Is this a terrible idea?

How do I find a heat pump that would do this?

Is my idea of having very cold water advantageous over just using a normal underground coil system where the temperature would be closer to 55 degrees? I feel like it would reduce the overall costs of operating the system, but I don't know enough to be sure...

2. ### urthbuoyWell-Known MemberIndustry ProfessionalForum Leader

I always think of just taking old refrigerator compressors and using a hyperloop to make ice for hockey and dumping the heat in the garage. Same idea as you've laid out (I think). But you have to do some number crunching and match your flows up.

3. ### docjenserWell-Known MemberIndustry ProfessionalForum Leader

That is how ice rings work. The problem is that it is not very efficient to run either 18-20 on the source or load side......so it probably gets very old very quick.

4. ### NDGeoNew Member

Do you mind elaborating on your statement? I don't understand this stuff well at all. Are you saying that even with a very cold reservoir (<40 degrees Fahrenheit) through which to disperse heat via a closed loop from the heat pump, the heat pump/chiller would have difficulty keeping proylene glycol at 18-20 degress?

5. ### docjenserWell-Known MemberIndustry ProfessionalForum Leader

The kind of refrigerant and heat pump design we are talking about here works only well with producing water down to 30F. Below 25 or 20F you are putting much stress on the compressor, and you get close to leave the working envelope of the compressor.

6. ### NDGeoNew Member

Got it. So, I need to find a chiller or similar that is designed to deal with sub-freezing temperatures. Any suggestions on where to search for that? Maybe a geothermal beer brewery chilling system?

7. ### docjenserWell-Known MemberIndustry ProfessionalForum Leader

No, but there are a few water cooled heat pumps for freezers....

9. ### urthbuoyWell-Known MemberIndustry ProfessionalForum Leader

Ammonia based system for the geo arenas around here.

10. ### Mark CustisNot soon.Industry ProfessionalForum Leader

^^^^ goes to find his bromide test kit.

^^^^Went to get an electronic library card to understand Doc a few pilsners into his schnapps.

Mark