DIY Geothermal?

Bob B

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I'm starting this thread as an offshoot of the passive storage thread that was kind of getting sidetracked by geothermal discussion.
For reference, that thread is over here if you want to read some of the discussion that lead to starting this thread.

The idea would be to use a water source heat pump ... or group of small water source heat pumps and a DIY geothermal field to build a much more efficient residential heating and cooling system.
Combine this with your solar system and storage and it will be a LOT easier to run heating and cooling from solar instead of trying to operate an air cooled system .... and be TOTALLY green.
 

Bob B

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There's another article here that describes the combination of heat pumps with geothermal.

This is a huge thing now with commercial energy retrofit projects .... There is some of this being done in residential, but these can be VERY expensive systems.
Lets figure out how to DIY it and make it a lot less expensive and something your can do yourself.

If you look on YouTube, there are a LOT of videos about doing DIY geothermal and DIY wells using water pressure and even pressure washers for the drilling.

Anyone interested?
 

NwCali

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Well, atm I'm building a small cable drill rig using a 3cylinder yanmar diesel motor. It should get to 200+ feet (my goal).

If it works I can post more about it, if it doesn't...

Here is a video of me doing this years ago...

 

NwCali

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This is even a better video of a much simpler rig. Notice he uses rope. This one even uses rope around a drum as the brake for the drill bit rope.

Cable/percussion drilling is very old and done right can go thru solid rock hundreds of feet deep using far less petroleum resources in doing so. Just not "fast".

I get how cooling can benefit from geothermal, but does heating benefit as much in most (warm) climates?
 

Bob B

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Wow ... What was the goal there? Surely you can't get very deep with something that large?
Well, atm I'm building a small cable drill rig using a 3cylinder yanmar diesel motor. It should get to 200+ feet (my goal).

If it works I can post more about it, if it doesn't...

Here is a video of me doing this years ago...

 

NwCali

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Large bore wells via percussion drilling is possible at some depth. Agriculture wells mostly. But yes they are limited to hundreds of feet at some point.

Look up the deepest drilled holes though, and it might surprise you just how deep we've drilled....
 

Bob B

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This is even a better video of a much simpler rig. Notice he uses rope. This one even uses rope around a drum as the brake for the drill bit rope.

Cable/percussion drilling is very old and done right can go thru solid rock hundreds of feet deep using far less petroleum resources in doing so. Just not "fast".

I get how cooling can benefit from geothermal, but does heating benefit as much in most (warm) climates?

Very interesting .... but that pipe looks a lot bigger than what would be needed for geothermal. That has the advantage of being able to break thru rock while a water drill is not going to be able to do that.

I guess whether or not the heating side would benefit would depend on what the outdoor temperature is? A heat pump just moves heat.
It certainly would be a benefit for cooling in a warm climate since the condenser is working with 50-55 degree temperatures instead of 90-100 degree temperatures.
 

Bob B

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I was thinking a lot of more shallow geothermal points might be easier to DIY that one or 2 very deep ones.
 

curiouscarbon

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Anyone interested?
Heck yeah!

I’m not really in a position to do deep drill geothermal, but something shallow maybe.

Edit: I’m interested in potentially doing a small scale hybrid : shallow geothermal + solar thermal with an insulated tank of water for buffer.

1628477896068.png

Edit2: like the diagram above, but with another heat exchanger to interface with the geothermal source too.

Insulated water/glycol tank of 50+ gallons.

Three stacked plate stainless steel heat exchangers. (or maybe just three pumps that circulate with the center tank. Unsure about all the trade offs there)
  • One for Air source water loop. Goes to a radiator to harvest air heat.
  • One for Ground source water loop. Goes to underground length of pipe to harvest ground heat.
  • One for Solar source water loop. Goes to pipes painted black for low albedo to harvest solar irradiance heat.
Single buffer tank. Single heat pump that is water sourced to this tank. One pump loop goes serially through all three stacked plate heat exchangers to enable exchange with any of the three sources with the main tank.

Three pumps on other side. Air source water loop pump, Ground source water loop pump, Solar source water loop pump.

This is the scale of pump I'm going to start with: https://coldandcolder.com/collections/featured-products/products/12v-micro-water-pump

What do you think? Sorry to mention non-geothermal. Maybe I'll start a separate solar source heat pump thread to keep everything in order...

I can only realistically dig 1-2 feet at this time, and for a very small area. So I wonder about how to calculate the thermal exchange rate or what have you. Wonder if people use PEX tubing for that... hmm.
 
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Mike 604

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Have build several homes with ground source geothermal systems.
Two types of systems, horizontal loop field and bore holes.
After the installs I have stayed in touch with the clients.
First geo I did was back in 2005, then in 2008 and lastly in 2012.
If that is the route one wants to go then it should be what is called a balanced loop field.
What I mean is that during the heating system heat is being pulled out of the ground and when cooling is required
the heat gain is put back into the ground.
Special transfer fluid should be used and also the grout used to encase the pipe in the pore holes, a special heat transfer type of grout should be used.
All the systems we installed operated at or over 300 percent efficiency.
Haven't done water source so cannot comment but would it would be the efficient in cost and performance/
Seeing what is available now I wouldn't use Geothermal.
 

Bob B

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Haven't done water source so cannot comment but would it would be the efficient in cost and performance/
Seeing what is available now I wouldn't use Geothermal.
The term water source is from the perspective of the heat pump only ..... it is using the water / fluid cycled thru the geothermal loop.

Not sure I understand the last sentence .... why wouldn't you recommend using geothermal? Maybe because things are pretty efficient without using it?
 

curiouscarbon

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This research paper caught my eye at least to peruse:

Operational Response of a Soil-Borehole Thermal Energy Storage System​

This study focuses on an evaluation of the subsurface ground temperature distribution during operation of a soil-borehole thermal energy storage (SBTES) system. The system consists of an array of five 9 m-deep geothermal heat exchangers, configured as a central heat exchanger surrounded by four other heat exchangers at a radial spacing of 2.5 m.
In addition to monitoring the temperature of the fluid entering and exiting each heat exchanger, 5 thermistor strings were embedded in boreholes inside and outside of the array to monitor changes in ground temperature with depth. After 75 days of heat injection at a constant rate of 20 W=m, corresponding to 11.5 GJ of thermal energy, the average ground temperature in the array increased by 7°C
1628479100907.png
 

Attachments

  • Operational Response of a Soil-Borehole Thermal Energy Storage System.pdf
    2.9 MB · Views: 1

curiouscarbon

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Consumer Off The Shelf approach, this is what I'm trying to work with.

These parts are what I'm going to try to start with..
Copper tube for tank thermal conduction. Coiled to go in a 5gal bucket. Serial connect to add capacity..
Adhesive backed neoprene foam applied to outside of bucket.
All buckets stored in an enclosure made from vacuum insulated panels R20/inch.
Shelter the outside radiator from rain.
Burying the buckets and insulating them isn't exactly geothermal, but it's ground based thermal storage 😅
copper tubing three eight.jpgbucket 5 gal.pngcopper bucket coil.jpgneoprene.jpg1628482247506.png


inline air blower.jpgcopper radiator.jpgstacked plate stainless steel.jpg

edit: single 5 gallon bucket of water should be able to buffer 80kJ per degree C change.. wow!
5 gallon * 3.7854 liter/gallon * 1000 gramsH2O/liter * 4.183 Joule/(grams•Kelvin) = 79171 Joule/Kelvin
 
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JoeHam

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If you have a decent sized pond on your property an underwater closed system can be an easy solution. See the pond/lake section in this document :


We looked at this when we built our very energy efficient home but the water space is a small marina and needs dredging every decade or two so we went with a simple heat pump.
 

toms

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Keenly following this thread, i’ve been watching what others have been doing for a very long time. So far i’ve seen plenty of very interesting and innovative systems, but nothing cost effective.
 

Mike 604

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The reason that I wouldn't recommend a Geothermal system is for a the following reasons.

1. 'Vertical" bore holes that we have installed to a depth of 220 to 285ft are drilled at a slight angles away from each other to allow more distance at the bottom of the bore hole depth. More room allows better efficiency.
Trucking the sludge/spoil from the bore holes is messy and not cheap. All the builds are on city lots, not on acreage.
2. The upfront and operating cost are more than installing an air to air or air to water heat pump.
The heat pumps that are now available are very cost effective compared to Geothermal.
If choosing this type of heat pump please pay attention to their effectiveness as there is no unified method of testing for manufactures. Many cannot work well in the northern cold climates
3. The Geothermal pump systems tend to be noisy so the slab on which the pumps are sitting on should be isolated from the main structure of the house. Pumps installed on vibration pads tuned for the frequency that they hum at.
Excavating, drilling, install vertical pipes, insulated manifolds leading into the house are extremely expensive.
Supply and return lines( Uponor) were $70 lin ft 9 years ago. Bore holes to pumps in our case was 120 ft.
4. Cost of natural gas vs electricity is almost 1 to 3 for a btu of energy. Electrical energy being more expensive than Natural Gas.
5. The homes that we build are typically hot water priority with hydronic in floor heating systems.
Meaning domestic hotwater tank get satisfied first then switch to heating.
Family of 5 uses water for showers and one takes a bath. The recovery of Geothermal to fill the 80g hotwater tank takes about 6 hours. It takes forever, so on one house we installed the Geothermal along with a IBC natural gas boiler so the slow recovery can be overcome by the boiler.
This particular house we found that the utility bill to heat the house with Geo vs Boiler is cheaper with boiler.
Boiler is rated at 95% AFUE and Geo tested to be 324% efficient. But because of cost ratio NG boiler cheaper then the Geo Syst.

We just finished an airtight house similar to a Passive House, where a blower door test was done to see how airtight the house is.
Test result at mid stage and after completion of house was less than .8 .
Roof was an inverted system R30 vaulted ceilings, 2x6 stud cavity insulated with R22 Roxul and we used 2" of Roxul comfort board around the perimeter of the house. Another words a big blanket around the house. Air barrier was Siga products.
The client after a year phoned to to update me on level of comfort when we had the "Heat Dome".
Temps reached over 109F for over a week and he said it is only during this time that he had to turn on his AC in the last year.
His Utility bills for Electricity and Natural Gas for a 1 year average is $34 per month.

In my opinion (building for homes for 34 years) make the house airtight, insulate insulate insulate and then you can heat your house with 2 light bubs and a fart....
 

toms

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We just finished an airtight house similar to a Passive House, where a blower door test was done to see how airtight the house is.
Test result at mid stage and after completion of house was less than .8 .
Roof was an inverted system R30 vaulted ceilings, 2x6 stud cavity insulated with R22 Roxul and we used 2" of Roxul comfort board around the perimeter of the house. Another words a big blanket around the house. Air barrier was Siga products.
The client after a year phoned to to update me on level of comfort when we had the "Heat Dome".
Temps reached over 109F for over a week and he said it is only during this time that he had to turn on his AC in the last year.
His Utility bills for Electricity and Natural Gas for a 1 year average is $34 per month.

Still will be significantly more expensive than a conventional build and reverse cycle aircon to achieve the same internal climate.
 

labeeman

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I have been on a ground source heat pump for 25+ years I have 700 feet of vertical loop in 4 wells and a 36K BTU heat pump. You will need 9 gals per minute which will give you a 10-degree rise in your water temp. I live in the deep south near the gulf coast and the humidity is the real killer here dewpoints this year have been in the mid-70s to the high-70s even a super-insulated tight house will need AC to control the humidity.

Screenshot from 2021-08-10 03-15-38.png
 
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