My DIY Geothermal Heat Pump Install

[YuriyLogvin]

Hello everyone.
I'm experimenting with my own DIY Geothermal Heat Pump install and wanted to share my progress. This is my second "Geothermal heat pump" project attempt and the fourth "DIY heat pump" in general.
This time I decided to go with a fluid-based geothermal loop, because of its various benefits.
I'm making a vlog with my personal observations and conclusions. If you want to follow along and prefer watching rather than reading, I'll post my episodes in order below:

P.S. English captions available for every video

[YuriyLogvin]

Episode 1 - Introduction.

In this episode I do a quick introduction to the DIY Geothermal Heat Pump project.

https://www.youtube.com/watch?v=FR4eW30ZMKY

Episode 2 - Building geothermal loop. Angled well drilling.

In this episode you'll see how we built a ground loop for my geothermal heat pump. Folks from Green Energy helped me to drill wells at an angle to horizon.

https://www.youtube.com/watch?v=reWuZFRFTQY

Episode 3 pt.1 - Heat pump design and assembly. Pt1.

In this episode you'll see how my heat pump works, we'll look at most basic, simplified heat pump design to understand core principles of it's operation.

https://www.youtube.com/watch?v=jQrfE33BBn4

Episode 3 pt.2 - Heat pump design and assembly. Pt2.

In this episode, you'll see how I assembled the heat pump.
The results of the first test run were a little disappointing. Flow meters were a bit off, but most importantly, the geothermal loop did not provide the expected 30 watts per running meter.

https://www.youtube.com/watch?v=Sn8HlS51ZOI

Episode 4 - Filling geothermal loop with alcohol.

Alcohol has a lot of different use cases, one of which, surprisingly, is being used as a filler for geothermal loop pipes. You'll hear my thoughts on why I decided to use ethanol and not ethylene glycol.

https://www.youtube.com/watch?v=neICwgHTyhg

So, this is my progress up to date.
I still can't figure out why the geothermal loop did not provide the expected 30 watts per running meter. Maybe it's because we had 2 dry years in a row and there's not enough moisture in the soil. I'm curious to hear your thoughts on this.

[YuriyLogvin]

Hello everyone,
I think I fixed mistakes that were made in my initial geothermal heat pump design. I was wrong, and now it's apparent that the evaporator should be bigger than the condenser.

I switched them up and the picture has become noticeably better. The output now is 2.81℃. In the next season I plan to increase heat exchangers size even more to utilize the full potential of the compressor.

https://www.youtube.com/watch?v=Pcle6XhMlzQ

[Robl]

I have come across something similar. That is, I have a 600W electrical, 2.4kW thermal, ground sourced heat pump with 180metres of pipe buried in our back garden. Initially the pipe just had water in it. After a month of running, it was on the verge of freezing, so I changed to 30% glycol 70% water. This does fix the issue, however the temperature between groundloop and propane is now 3C worse; the glycol is significantly worse at transferring heat.
Some of the discrepancy may be down to the "Partial heat transfer coefficient", pic below found from here:
https://onlinelibrary.wiley.com/doi/...527621583.app2
I've heard 2kW/degC/m^2 before for the temperature drop across a BPHE, but perhaps it's more complex than that, and depends on what the fluids actually are. Water just happens to be excellent, and organics (glycol or ethanol) not so good, hence swapping your BPHE's around so that the larger one is used with the ethanol, smaller one with just water is better?

Loved your vids by the way :-)

[Zwerius]

I can understand, that by switching your heat exchangers, the supplied thermal power can be improved. But I think to improve your COP, the only way is to enlarge the surface area of your ground loop.

[Zwerius]

Originally Posted by YuriyLogvin

Episode 1 - Introduction.

In this episode I do a quick introduction to the DIY Geothermal Heat Pump project.

Episode 2 - Building geothermal loop. Angled well drilling.

In this episode you'll see how we built a ground loop for my geothermal heat pump. Folks from Green Energy helped me to drill wells at an angle to horizon.

Episode 3 pt.1 - Heat pump design and assembly. Pt1.

In this episode you'll see how my heat pump works, we'll look at most basic, simplified heat pump design to understand core principles of it's operation.

Episode 3 pt.2 - Heat pump design and assembly. Pt2.

In this episode, you'll see how I assembled the heat pump.
The results of the first test run were a little disappointing. Flow meters were a bit off, but most importantly, the geothermal loop did not provide the expected 30 watts per running meter.

Episode 4 - Filling geothermal loop with alcohol.

Alcohol has a lot of different use cases, one of which, surprisingly, is being used as a filler for geothermal loop pipes. You'll hear my thoughts on why I decided to use ethanol and not ethylene glycol.

So, this is my progress up to date.
I still can't figure out why the geothermal loop did not provide the expected 30 watts per running meter. Maybe it's because we had 2 dry years in a row and there's not enough moisture in the soil. I'm curious to hear your thoughts on this.

Did I understand it correctly that you have 30% ethanol and 70% water in your ground loop?

[YuriyLogvin]

Originally Posted by Robl

I have come across something similar. That is, I have a 600W electrical, 2.4kW thermal, ground sourced heat pump with 180metres of pipe buried in our back garden. Initially the pipe just had water in it. After a month of running, it was on the verge of freezing, so I changed to 30% glycol 70% water. This does fix the issue, however the temperature between groundloop and propane is now 3C worse; the glycol is significantly worse at transferring heat.
Some of the discrepancy may be down to the "Partial heat transfer coefficient", pic below found from here:
https://onlinelibrary.wiley.com/doi/...527621583.app2
I've heard 2kW/degC/m^2 before for the temperature drop across a BPHE, but perhaps it's more complex than that, and depends on what the fluids actually are. Water just happens to be excellent, and organics (glycol or ethanol) not so good, hence swapping your BPHE's around so that the larger one is used with the ethanol, smaller one with just water is better?

Loved your vids by the way :-)

Thanks! I hope my videos may help someone who is only starting to think about DIY geothermal and they won't make the same mistakes that I did.

[YuriyLogvin]

Originally Posted by Zwerius

I can understand, that by switching your heat exchangers, the supplied thermal power can be improved. But I think to improve your COP, the only way is to enlarge the surface area of your ground loop.

You're absolutely right. But it's a more expensive and complex thing to do.

[YuriyLogvin]

Originally Posted by Zwerius

Did I understand it correctly that you have 30% ethanol and 70% water in your ground loop?

Yes. You got it right. It works fine for now.

[a_q]

Hi Yuri,

what is the advantage of drilling the boreholes at an angle instead of straight down?

Isn't it more difficult to insert the pipe loops?