geothermal heat

metalspinner · February 07, 2007, 12:25:38 PM

Does anyone have any experience with heating their homes with geothermal heat? I guess there are two ways of gathering the heat. One is using lots of square footage with coils of tubing layed a couple feet below the ground surface. The other is drilling deep hole's and using the area of the circumfrence and depth of the hole. We had a fella out to work on our heat pump again and he mentioned they do the deep boring kind of collection. The up front $$$$$ is high. Notice how many dollar signs I have there. I would like some input from those in-the-know about your experience's with this.

Thanks, Chris

Shotgun · February 07, 2007, 01:10:19 PM

Chris,

We built a new house in 1990 in Traverse City, MI, and natural gas was about $50,000 away from the house at the time. Decided to go with a groundwater heat pump. Took water from a well, removed a little heat from it and returned it to the ground via a 100' perforated open ended pipe. We live on a sand hill so no problem getting rid of the water. It never did come out the far end. We got a special power rate for having an all-electric home, and back then there was still a tax incentive for using the geothermal unit. Used the unit for 10 years and it worked well from a heating standpoint. It was great from an effeciency standpoint. It lacked a little from a maintenance standpoint though. Had two 80 gal. water tanks to reduce pump cycling.

House is 2,400 sq. ft. Total electric cost was about $1200/year. We also have an irrigation system that comes from the same well. During the summer the unit (reversed) was a very nice air conditioner. I was more than happy with that as our total utility bill.

It's a pretty complex system and relies on the fact that it all works, including the pump in the well. Had to have it maintained about twice a year. Even with routine maintenance, it needed a little special tuning at times. Thus the downfall. It involves a pump in the well, a condensor, circulation pumps and selenoids to control the valves, and a take away pump to move the water to the dispersal line. When everything works, fine. When it doesn't, you have a problem. It had a supplemental electric heat, that seldom was used. If you turned the temp down, it didn't come up again real fast. Instructions were to set it and leave it.

Bottom line, I didn't feel that I could depend on it while we were in FL for the winter. Life changed over 10 years. Hadn't thought that far ahead, I guess. During that time the natural gas became available with someone else's $50,000. In 1999 I took it out and replaced it with a high effeciency gas furnace with an igniter. Had to install an airconditioner too--spoiled by that time, even in Traverse City.

All in all, we paid for the increased original cost. I wouldn't do it again, given the availability of natural gas. Probably wouldn't do it again even without the availibility of natural gas. It was interesting though, and I proved it worked in this far north. There are a number of them around here, and they're still installing them.

The systems might be better engineered by now. Still costly. Perhaps the confined water
type (closed system) might be more practical.

Norm (in FL for the winters)

metalspinner · February 07, 2007, 01:32:01 PM

Thanks, Norm.

My father-in-law lives in Traverse city - year around.

I'm not sure if the system I had in mind uses ground water. Maybe just the heat from the dirt? This in turn heats the water in the coils? I need to do some serious research. Our utility bill is between $400-$500 a month.

Woodcarver · February 07, 2007, 02:48:51 PM

Friend of mine put a heat pump in a new home he built about 25 years ago.
The house has six inches of insulation in the walls and is clad with another two inches under the siding. There's 12+ inches in the attic. I'm not sure of the square footage, but the house isn't huge. It's two-story with, I think, four bedrooms.

He hasn't been happy with the heat pump. It doesn't have enough output to heat the home in weather like we've had recently. His back-up is electic heat. He said the meter spins so fast at times it makes him dizzy. When he installed the pump he was projecting a seven-year payback. Instead it's costing him more than oil or propane would have (no natural gas in his area).

thurlow · February 07, 2007, 06:50:04 PM

Not gonna help you any; just a comment. There've been at least 3 threads recently about Mike Rowe; on one of his recent (may have been a re-run) shows, he was digging wells for geothermal heating/cooling.

dutchman · February 07, 2007, 07:55:46 PM

A coworker has the well type geothermal. Log home was built 10 yrs ago.
He said they drilled one extra well incase they had troubels in the future.
With they well system you could plug one bad line and not be in trouble.

submarinesailor · February 10, 2007, 08:38:40 PM

Chris,

Check out the info posted in reply 100 of the "Anyone experiment with alternative energy?" tread runing here.

Bruce

limbrat · February 10, 2007, 11:03:31 PM

You can also run the closed loop in a pond or other body of water.

Woodbender · February 23, 2007, 01:05:15 PM

Hi Chris.

I'm new and usually haunt the Timberframing and Sawmilling forums. But this one is of particular interest to me since I'm designing our next home now.

I had a conversation with a builder who was at our church a while ago - real nice guy - real down to earth knowledgeable. He actually did pretty much what you are thinking of doing Chris and it's almost all passive.

When he initially built his home he laid 4 8"(?) pipes in the ground about 6 feet down below grade - well below frost anyway. (we're in G.R. Michigan) The intake on these pipes was well above ground and protected from rain and water infiltration, critters etc. These pipes bring in new air pretty much by thermalconvection (is that a word?) His house also is extremely air-tight. His wood stove would exhaust out the flue of course and these 4 underground pipes would bring in new ground-buffered air just from the draw on the flue. The air temperature coming in from these pipes was cool yes but not near as cool as the outside air. Mind you the pipes were about 100' long and had a while to warm up the air before it came into the basement.

Even if the new air was 50°(f) he had to heat it only 20°(f) to make things comfortable. Not bad when it's 15° outside. He said in winter (with only his rather small woodstove going) they were "forced" to walk around in shorts.

And in summer just the reverse would happen. Since the ground would buffer the temperature of the air in the pipes coming into the house it was much cooler. The home's hot air would exhaust out through some upper clerestory windows and draw the cooler buffered air into the house.

A downfall to this obviously is whatever the humidity levels are outside you will have inside. (to some extent).

I'm going to have to call Don and get some particulars on exactly what he did and how he set it up.

No moving parts.

beenthere · February 23, 2007, 01:55:52 PM

Not clear to me if this air is coming into the house proper, or just coming in as combustion air to the wood stove, or other furnace. And is it just gravity flow, or fan-induced (moved) ?

Incoming air in the winter would have very little moisture (high humidity at low temps, but very low humidity when that air warms up). In the summer, the air would have a lot of moisture, and when cooled, would condense the moisture out when above the dew point. Seems this air if dumped into the home, would raise the humidty above the comfort level.

Speaking of comfort level, I wouldn't want a heating system that went above the set-point (comfort level) such that I would have to take clothes off to be comfortable. There would be some changes made to such a system in a hurry.

A good system will keep the temp at ±1° about the setpoint.

Woodbender · February 23, 2007, 05:04:08 PM

I guess you pay your money and make your choice. It was more a brag that they COULD walk around in shorts if they wanted. More often than not he'd just turn the intake down on the woodstove and regulate heat that way.

The air I believe was coming into the basement not directly into the woodstove. In effect I guess that would turn the basement into a supply plenum? I am not sure if he had forced air bringing this air in - I don't think so.

Humidity in the summer would often not be a problem now that I think about it. He had a reverse slope (away from the house) so any condensing moisture would drain back down the 100' pipes to a gravel cistern. Cooler ground temps condensed out a lot of the humidity.

I don't know of many systems that keep living spaces within 1°±. Not that are justifiably affordable anyway. However I am also looking at radiant floor heating which may have that capability.

If I have the option to inexpensively buffer the air that I have to heat - you bet I'm going to. He's got a fantastic system that seems to do what he want's it to do.

Thanks for the reply.

PineNut · February 24, 2007, 09:27:44 PM

I have an outdoor boiler (hot water furnace) and forced air distribution system in the house. A simple thermostat keeps the temperature within about one degree F in the vicinity of the thermostat. However due to varying heat requirements, the temperature in the other parts of the house varies a bit more. I have thought about letting the blower run continuously and controlling the water circulation pump with the thermostat.

I have thought about using the underground pipes to cool the air here in the summer but with the mean temperature abound 67 degrees F, I don't think it would be sufficient for cooling. And with that high of temperature, would probably have humidity problems also.

Wood_Niche · March 19, 2007, 09:18:03 PM

It's all in what you want. My wife and I just built a new house out of SIP (Structual Insulated Panels)and we put in Geothermal Heat. We have Radiant Heat in the basement and garage, and forced air in the House. Our house is 100% electric. Its about 2200 SqF and our complete electic bill is $50-$150 depending on the month. All the research I did said the pay-back was 7-10 yrs. Your up-front cost is more, but in the long run your better off!!! I'm a firm believer of Geo and would reccomend it to anyone. I am fortunate to have eonough room to put in trenches, I bought a used backhoe(big boy toy) and did all the trenching myself. I figure I paid at least half of it off by the money I saved not having to pay for excavation and now I have a backhoe around the house. The trenches needed to be at least 5' deep. If you need to put in a well for your house you might want to go with wells. Either way works good. The other good point is in the summer you have free A/C!!! beacuse the ground temp is 50F I would be more then happy to answer any other questions if I can.

olyman · March 21, 2007, 10:01:25 PM

well--my brother already had the well--which couldnt drink--so--he now has geothermal on a well--its costing him 35 dollars a month to heat his new house--6 inch walls---well insulated---all electric house--hes very happy---and second season on it--and has done nothing--hes thinking hes likes it a lot---compared to the old house--and the propane bill!!!!!!!!!! now to get the generator hooked up!!!!! for emergencys

scsmith42 · March 21, 2007, 10:21:00 PM

Wood_niche - I've already got the backhoe - as well as a pond, and my utility bills are terrible. Any information or advice that you can share would be most welcome.

Scott

Radar67 · March 21, 2007, 10:23:03 PM

Scott, have you checked out waterfurnace.com? Some good info there on the theory and setup.

Stew

scsmith42 · March 21, 2007, 10:35:36 PM

Stew - thanks for the link - I'll check it out.

Scott

Wood_Niche · March 22, 2007, 09:14:10 PM

Scott,

If it's time to up-grade your furnace I would put in a geothermal unit.
I had to dig 6 trenches 2-3' wide by 100' long and them a main line to the house
all deeper then 5'. then hook them up to the system.
I had bought the unit from the contractor and they purged the lines and hooked up.

Marshal

metalspinner · March 22, 2007, 09:27:19 PM

Are trenches more cost effective than drilling wells. It seems they should be. Probably less mess as well. Why isn't this heating and cooling source more main stream? I can see entire tracks of housing using this. Can branches off the main line to other buildings (workshop) be used? Other than the initial investment, I can't think of a reason not to go this route.

Is the depth of the trenches determined by the frost line? And the length of total feet determined by cubic footage of heated space?

QuoteI had bought the unit from the contractor and they purged the lines and hooked up.

Marshal,
Can you give us the name of the unit you are using?

Furby · March 22, 2007, 09:51:17 PM

Dirty Jobs did a show with Mike helping out drilling wells for geo heating/cooling in a retirement community being built.
Lots and lots of wells.
Main reason it's not main stream, is indeed the cost.
However, it isn't a 100% perfect means to heat/cool every situation out there.

scsmith42 · March 22, 2007, 10:02:12 PM

This is all great info.

My electric bills are averaging about 5K per year (excludes barn), and propane adds another 2K or so. I'd like to see what I can do to significantly reduce these bills, and HVAC is high on the list.

I have a backhoe and a lot of clay soil, so digging trenches is not a problem (or significant cost) for me. I also have a pond; the closest portion is about 4' deep and about 400' from the house; the deepest portion is about 18' deep and 700' or so from the house.

I will probably stay away from the well concept, since that would not be cost-effective for me.

I've been wondering about what the most cost effective way to heat/cool the house, barn, and shops will be. On the one hand, I can recirculate water from deep in the pond up to the house, and in addition to using it for geothermal, could also use it for a pre-cooling heat exchanger where I am using the cool pond water to cool the house air (thus reducing the amount of time that the AC needs to run). However, I don't know if the cost to recirculate the water 24/7 will exceed the energy cost for the conventional AC. Also don't know if the geothermal units are already so efficient that I won't gain much from this concept.

This may prove to be the best cocept for cooling the shop though, as I doubt that I'll want to spend the $ to operate an AC unit in there. I'm thinking of an outdoor wood boiler for the shop heat. Since the boiler will be about 500' away from the house, it may not be cost effective to try to recirculate the hot water from it to the house and back...

Also am wondering if it's more cost effective to take the geothermal loops to the deep portion of the pond, or to bring the cold pond water up to the geothermal unit.

Advice / input from y'all is welcome. I really enjoyed the link that Stew posted.

Thanks.

Scott

Wood_Niche · March 25, 2007, 08:53:15 PM

My Geo Thermal unit is a Climatemaster.
Genesis Series GSW060 Water to water heat pump.
Pumping modules are Flow Controller 2.
I was going to post some pictures, but I can't quite do it yet. (computer illiterate...have to read more)
So, I posted pictures in my gallery.
The ground loop connects to the pump and them to the heat pump.
These's a bonus the two lines coming out on the lower right side go to the hot water tank.
So, when the pump is working there is excess hot water, which helps the hot water tank.

metalspinner · March 25, 2007, 09:13:42 PM

Thanks for the pics in your gallery.

You have done all the work to post the pic. Now all you need to do is get the glory. :D
Just four more clicks and you have it done.

Click on the pic you want to post from your gallery. Then click the "Click to insert...." caption under the pic. This copies it into your "edit" in the tool bar at the top of the screen. Then go back to your post and click the curser where you want the pic to be. Go to the "edit" in the tool bar and click "paste". That's it. You can double check the position when you preview your post.

scsmith42 · March 25, 2007, 09:17:05 PM

Wood_niche - thanks for the info. I'll add Climatemaster to my evaluation list.

Regards,

Scott

slowzuki · March 26, 2007, 09:05:23 AM

Some info for people planning:

Modern water-water heat pumps are hermaticly sealed at the factory like a fridge or window AC. Older units were built on site and required recharging and had more frequent problems.

Loops are cheaper than wells, if you have the right type of ground. This needs to be calculated based on heat pump size or the system will suck. The best grounds are clays, wet soils, muddy ground, ponds, etc. Sandy dry ground isn't great as it doesn't have as much heat capacity.

After the compressor, the water circulation pumps use the next most amount of power. There are a number of ways to arrange the pumping so you don't use as much power. For example, if you are using an open loop getting water from below your house, taking the discharge line to below the source will reduce your pumping requirments if you can keep the line primed. A good designer can take care of these issues for you. Closed loop is a bit easier to design, using large diameter piping and parallel coil setups.