Geothermal loop

[grouper therapy]

I have been playing with the idea for a year or more so this weekend I decided to start the project. I laid a loop of 200 lf of thin wall pvc about 5 feet underground. I plan to connect the closed loop system to a 1hp titanium heat exchanger. more to come

 

[lilrobb]

Excuse my ignorance, what does it do?

 

[thewarbrd]

I've wondered if anyone has done this.. Robb, basically the underground temp being a lot cooler than surface (ever been in a nice cool cave?) acts like the compressor... Pretty much he's building a massive chiller for the price of the pump, tubing, and exchanger.

There are actually HVAC systems used to heat/cool houses and even entire schools, etc based on only huge loops of pipe run underground.

 

[cr500_af]

Yep, when I built my house I had planned to do geotherm HVAC but I ran out of funds! Basically, the temp where the loop is is about 55 degrees year round.. so your heat system is heating starting from that point, rather than the thiry-whatever the outside air is. Same with the a/c. The heat exchange is into the ground rather than the air. You can also place the loop on the bottom of a lake or pond if it's deep enough.

A side benefit of geotherm is that hot water is a by-product, which can be used to save on the cost of running a water heater. My power company had a deal where they would pay the installation and you leased the equipment from them for life... sounds like a bad deal but they guaranteed that the energy savings was larger than the lease payment, so after it was all said and done you paid less every month, plus the equipment was theirs to maintain.

 

[lilrobb]

Mhh,

INTERESTING!

 

[elfloyd]

uh-oh... Robb's thinking too hard!

 

[grouper therapy]

I had to replace the water supply line from the street to the house so I decided to go ahead and dig the diches for the loop while I had the equipment rented. I did go ahead and put down the pipe and stubbed it up to connect to in the next couple of weeks. I have to pput together a workshop for some members to build some stands hoods etc. soon.

 

[derek_s]

Wow, so finally some of your crazy, innovative ideas are coming to fruition. A few more years and you will have an inspector gadget (or frankenstein?) tank. Give me a call if you need a hand with anything. I havent seen you in a while. I have been making myself scarce as well...

 

[oldschool52]

Sounds like one of my projects/ideas. Should work as long as water doesn't flow to fast. I heated a 700gal pond in a greenhouse in a similar way. Took 100ft 1/2" copper tubing coiled in front of the gas heater used to heat greenhouse. Put a small pump in pond, one end of tubing (input) other end of tubing back into pond. Kept pond water over 70°f all winter for tropical lilies. Keep us up to date on peogress.

Great idea.

 

[chymos45]

Never got the stones to try this myself, but did a bit of research a while back. Found a system that simply piped the tank water through the loop underground without using a heat exchanger. Added quite a bit of water volume to the system and he claimed it ran incredibly stable once he got the flow rate dialed in. Also found one that simply sank a couple of 55G drums in the back yard, filled them with water, and coiled some tubing in the drums through which he ran the tank water. Same effect as above.

 

[chymos45]

oldschool52;361419 wrote: Keep us up to date on peogress.

Great idea.

Ditto. Take lots of pic's.

 

[cooper]

Nice idea Dave. Hope to see it.

 

[grouper therapy]

Chymos45;361425 wrote: Never got the stones to try this myself, but did a bit of research a while back. Found a system that simply piped the tank water through the loop underground without using a heat exchanger. Added quite a bit of water volume to the system and he claimed it ran incredibly stable once he got the flow rate dialed in. Also found one that simply sank a couple of 55G drums in the back yard, filled them with water, and coiled some tubing in the drums through which he ran the tank water. Same effect as above.

I have read several threads where tank water was ran thru the loop. That is probably the most efficient heat transfer. I was just a little nervous about that method (contamination ,stagnet water and leaks).Not to say that the titanium heat exchanger could not release loop water into the tank system but I felt it was less likely to do so. I also could inspect and /or replace the heat exchanger much easier than the entire loop. The loop water can remain without flow when not needed since stagnation is of no concern in the loop. I plan on using the temp controller from the chiller to activate a circulation pump whem temps rise above setpoint. I also plan on mounting the unit at the end of my sump so that when the unit starts up the once condenser fan now becomes an evaporator fan blowing across my sump.

 

[krb]

grouper therapy;361323 wrote: I have been playing with the idea for a year or more so this weekend I decided to start the project. I laid a loop of 200 lf of thin wall pvc about 5 feet underground. I plan to connect the closed loop system to a 1hp titanium heat exchanger. more to come

I have dealt with geothermal systems in my line of work and I suggest two things:

use copper pipe for the loop to maximize heat transfer

bury it as deep as possible to be the most efficient. Geothermal HVAC units are drilled way down into the earth. (although, it is a different system than what you are doing)

 

[grouper therapy]

KRB;361443 wrote: I have dealt with geothermal systems in my line of work and I suggest two things:

use copper pipe for the loop to maximize heat transfer

bury it as deep as possible to be the most efficient. Geothermal HVAC units are drilled way down into the earth. (although, it is a different system than what you are doing)

I used the thin wall pvc which I'm sure is no where as efficient as copper but the price difference was huge. Take the labor out of the equation and I could put down 2000' of pvc for the price of 200' of copper. I think I read that the groud temp stabilizies at around 5 feet in this area but please correct me if I'm wrong. Most drill the deep holes for two reasons constant temp and limited space for horizontal loops once again correct me if I'm wrong. I may have more ?s for you(KRB). I did design the loop so that I could add 300 lf more to it. I may use copper then if the budget allows. An engineer on rc said that the polyethylene pipe was just as efficient as copper in the geo loops because only so much would be transferred into the ground anyway Have you ever heard that?
Please if anyone has experience or IDEAS for this chime in. That is how we learn and advance.

 

[savingnemo754]

They use a poly pipe when doing HVAC systems. So I would say that you will be fine with the thin wall PVC. I'm not a fan of the thin wall cuz it tends to leak/break very easily. Make sure there are no rocks up against the pipe and you should be alright.

 

[grouper therapy]

I have considered the following to install in the loop.
Water supply to the loop
Bleed off valve for trapped air
Drain valve
Temp sensor one in, one out
Flow meter
Any Ides??? for other items

 

[grouper therapy]

savingnemo754;361451 wrote: They use a poly pipe when doing HVAC systems. So I would say that you will be fine with the thin wall PVC. I'm not a fan of the thin wall cuz it tends to leak/break very easily. Make sure there are no rocks up against the pipe and you should be alright.

Thanks for the info

 

[sailfish]

Sounds like fun.

Now all you need is to use solar panels to run your MH and you could be the a example of a green tank.

Joe

 

[krb]

grouper therapy;361449 wrote: I used the thin wall pvc which I'm sure is no where as efficient as copper but the price difference was huge. Take the labor out of the equation and I could put down 2000' of pvc for the price of 200' of copper. I think I read that the groud temp stabilizies at around 5 feet in this area but please correct me if I'm wrong. Most drill the deep holes for two reasons constant temp and limited space for horizontal loops once again correct me if I'm wrong. I may have more ?s for you(KRB). I did design the loop so that I could add 300 lf more to it. I may use copper then if the budget allows. An engineer on rc said that the polyethylene pipe was just as efficient as copper in the geo loops because only so much would be transferred into the ground anyway Have you ever heard that?
Please if anyone has experience or IDEAS for this chime in. That is how we learn and advance.

The systems I have dealt with are a bit different from what you are doing in that they use a compressor and a type of antifreeze/coolant that is piped way down. The temp is regulated by how much compression is added to the liquid. For what you are doing, obviously cost is the limiting factor. Go with what you got and see how it works. I am interested in this as well. Another note, maybe try a different liquid that has better thermal absorbing properties. I probably would try coolant with thin wall pvc, but maybe there is a different solution.