Just for the geothermal loop, we are trying to get an idea of the costs for vertical wells.
Are you looking at $/linear foot, per ton of cooling, or number of wells & depth per well?
We have a site that may be well over 1,000 tons; would there be any savings from installing more or less wells?
There are significant differences in the heat exchange rate for earth coupled condensers. This size project you should drill a test well and measure the rate of heat exchange.
drill a test well?
Should you get soil samples first, test the soil properties and then make calculations? or are you saying to make a field test with one well?
Originally Posted by Texasgrand
Please clearify, I have GREAT interest in this subject. :)
From another post
multiply dollar amts by 1.6 to correct for inflation.
Drill test well?
If this is a commercial development the civil engineer has probably already drilled geo test holes to determine subsurface soil types for structural design. You are looking for geology that has ground water passing through it to dissipate the heat. If there is no ground water I would drill a test well, install a pump and logging equipment to determine the rate of heat transfer. The risk is the ground will become saturated with heat in a few years. If you are in an area where you have a balanced input and removal of heat, you are probably OK. In Texas we put in more heat than we take out in winter. I have also installed a couple of geo refrigeration jobs where we never take out the heat. I would only attempt this if there is substantial ground water like an old riverbed. In northern climates you could put in ice melting pipes under the parking lot to dissipate heat saturation. If in doubt install taps in the header for a future dry cooler.
Contact the staff at Oklahoma State University. They know more about ground heat exchangers than anyone.
Texas hit it
Texas hit it on the head. We are in South west Kansas where we have almost a perfect match for annual heat removal vs storage, however every job is different. What climate are you in? How much internal heat gain are you dealing with? How does your annual heat loss compare to your heat gain?
Keep in mind that you do not want a perfect balance here. You have to both add and subtract the energy your machinery is using.
1000 tons, you should look at retention ponds or lakes.
Alot of schools and places go that route, as there are other bennies to have them on site.
A lot of Engineers I deal with prefer a hybrid system and use a fluid cooler or cooling tower with the geo field. They usually come back and add one after 10 yrs or so if they didn't have one in the first place. So like Texas said at least have the headers installed for future.
Yep, that was what I thought too! OP asks for generalizations on a system that will run $100/hr for electric bill alone, and wants to do rule of thumb? HP equivalent of burning over a ton of coal an hour, etc....
Originally Posted by zachhvac
e.g. "we are trying to get an idea of the costs for vertical wells"
OP needs not just AN engineer, but a relatively good sized team.
Jobs I've worked that size need a geologist part time at least also.
Absolutley no place for that size of project to "try..to get an idea of the cost"
Would have thought 'troll' except the OP does have over 250 posts, time for pro upgrade?? Then we can talk the $$millions needed for this system.
Maybe I am missing the point here but why don't you just consider a cooling tower and boiler reheat? Is the ground loop ultimately more cost effective? I have never looked at the cost comparison. We have a mix of system in our area. There is one downtown here that has an intake well and a discharge well for a plate heat exchanger. It is a LEED building so it must be pretty efficient. I have done some comparisons between a WSHP loop with a tower and a boiler against rooftop units. The WSHP loop kicked ass on teh RTU building. The annual energy use was way low on the loop building and the RTU building is about 20 years newer with better insulation and windows of course.