Farm heat pump design

Paul Pollets

Eugene, I've a friend who owns and runs one of the largest organic farms in Wa. state, near Tonasket, on the E. side of the cascades. He grows heirloom tomatoes, berries, fruit and vegetables. He has been running Pex through the tomatoe greenhouse with huge success, using  several propane fired boilers.

He'd like to install  ground source heat pumps with 3 million Btu capacity. He has many acres to utilize for the piping. He'd like to run a biodiesel co-generator to offset the costs...any advice for a sensible "green" system design?

Eugene_Silberstein

Heating Options

Hi Paul,

I hope all is going well with you in your corner of the country.

There are a number of issues that need to be considered with what your friend is trying to accomplish. The number one issue is the cost of the electricity to run the system. If he is looking at a 3 million btu system, you are looking at massive elecric power consumptio, given the power factor on the equipment will likely be in the 0.6 range. Off the top of my head, I do not know the cost of electricity out there, so that needs to be taken into account.

You mentioned that he has a lot of land for pipe burying. Is he planning on planting in this area after the pipes are buried? This might very well be a consideration as well, depending on the depth of the pipes. The temperature of the ground will affect crop yields. I have heard of farmers burying pipes to heat the crop fields and have done so with success.

I am a big fan of geothermal, but am concerned about the scope of the project. A lot of number crunching has to be done to determine what the return on investment will be.

Has he considered a hybrid heat pump/solar setup? This might be a perfect option.

Let me sleep on this one for a while and see if something comes to mind.

Paul Pollets

costs

Electricity costs $.04 Kw/hr in the farm's area. Still, a co-generator fired from biodiesel may be the best bet for electrical load. I've seen equipment in Europe that provides both electrical and HW heat from cooling the generator.

tim smith

Hey Paul, interesting project

That would take a lot of pipe in the ground. hows the digging over there. Is it not pretty rocky down at say 6-10 feet deep there.  250tons x say 200 ft long trench/ton,  Wow thats almost 10 miles.   Just thinking out loud. Man would that be a chore. Sounds interesting although. 

tim smith

Hey Paul, interesting project

That would take a lot of pipe in the ground. hows the digging over there. Is it not pretty rocky down at say 6-10 feet deep there.  250tons x say 400 ft long trench/ton,  Wow thats almost 19 miles.   Just thinking out loud. Man would that be a chore. Sounds interesting although. 

Mark Eatherton

Trench???

With that much land, I'm thinking large open excavation pit with slinky loops installed.



http://www.google.com/imgres?imgurl=http://www.rockymountaingeothermal.com/graphics/gallery/services/slinky_pit_loops.jpg&imgrefurl=http://www.rockymountaingeothermal.com/services.htm&usg=__vFWOW6FXVHBdXapoOMHryoR9VoU=&h=300&w=400&sz=45&hl=en&start=13&zoom=1&um=1&itbs=1&tbnid=_ZsmVbniKtVJ-M:&tbnh=93&tbnw=124&prev=/images%3Fq%3Dgeo%2Bpit%26um%3D1%26hl%3Den%26client%3Dsafari%26sa%3DN%26rls%3Den-us%26tbs%3Disch:1



I'd also strongly recommend that if there is a possibility of drought, that perforated water lines be laid in the trench to allow for the re-introduction of moisture. Without moisture, soil conductivity drops significantly and then you lose contact with good ol' mother Earth and your system flails.



Instead of all ground source, why not a hybrid system that uses AIR source for the primary loads, and maybe a large GSHP pump and dump for back up during peak load conditions.



Or is true volacanic geothermal a possibility?



Or maybe a combination solar thermal with long term Earth storage, and GSHP extraction. Kind of like Drake Landing...



The aquifer would need to be static instead of dynamic, but it is proven doable.



And don't forget the possibility of waste heat recovery from vegetable washing facilities.



Think outside of the dirt box Grasshopper :-)



ME

Mark Eatherton

Geothermal potential map

http://geoheat.oit.edu/images/usmap1.gif



ME