Geothermal what do I need to know?

[kkcomp]

I am building my retirement home and want to be fully off grid. My property is so remote that the electric company wants 55k to run power to me so off grid just makes sense. I am considering using geothermal for heating in east Tennessee but know very little about it. House will have a walkout basement and 2 floors above. The basement will be in the side of a mountain and someone suggested that since I have to dig why not dig a bit more and use geothermal. Sounds like an idea but it can't be that simple. 

Please educate me about geothermal the plus and minus and what to pay attention to so that if I do it I do it right and only have to do it once.

[Al_Smith]

I've had two On a conventional system you will need electrical power because those system are basically a water cooled heat pump .I've had two of same but lack a supply of good mineral free water because about 7-8 years is all they've lasted before the heat exchanger failed which caused the compressor to fail .Saying that when it worked it was less expensive to operate than air to air .
There are options such as a closed ground loop with clean water using a secondary heat exchanger . However in this area of Ohio it takes approx 700 feet of ground loop per ton of capacity and mine was a 5 ton unit .Another option could be a submerged closed loop in a pond or lake .However you'd need a pond or lake to do that .Add all that up the initial cost of installation it might take 30 years to recover the expense .

[Southside]

Have you considered a wood boiler with a solar hot water collector system, combined with a large storage tank you could run that off grid, especially with some passive solar design into the house.  

[Al_Smith]

If you really want to get down to brass tacks in mountanious country if you have a stream with enough flow you could rig up a generator using a water  turbine to generate electrical power .Then again it would require an outlay of money or creativity to do it .Like they say there are no free wood piles .--just saying .  

[peakbagger]

My guess is there are better ways to heat and cool a place in TN than with geothermal. Ideally you build the house so it doesnt take that much to heat or cool. If you go with a typical 5 ton unit that seems to be popular down south, the cost to dig the trenches is going to be steep. The alternative is to drill a vertical well or wells but that would require about 1500 feet of borehole,. If you temps rarely get below 20 F, an couple of air source minisplit type heat pumps are about the most efficient, there is even a company that makes them to run off a 48 volt battery so no need for a big inverter. They even sell one that doesnt even need a battery and only runs when the sun is out (good for AC) not so good for winter. 

[Hilltop366]

I would get some "ball park" quotes and add up the cost of the geothermal system and the cost of the off grid power system to run it and everything else and compare to the power line cost before I got too far. 

[rusticretreater]

Numerous vids and websites to fill you in on the different methods.  I never liked the vertical style of geotherm systems.  You are locked into having a contractor to install it and to repair it.

Don't forget to consider a wind turbine as another source of power.  I know a fella who has one and coupled it up to a tesla battery.  And of course you could hook an exercise bike up to a generator.

[kkcomp]

Have you considered a wood boiler with a solar hot water collector system, combined with a large storage tank you could run that off grid, especially with some passive solar design into the house.  

I had thought about running pipes around the fireplace, and some sort of solar hot water. But how hot can a solar water heater system get if it's in the 20's outside?

[thecfarm]

I have no idea what's out there for windmills now.
I was looking about 40 years ago. The company that I was looking at had two styles, a free standing one, that required a pad and one that was guided wire, free standing. The one that was held up by wire was cheapy to install, no costly ground work and big pad to keep it upright.
But driving around all I see are the free standing ones.
Must be a forum out there for what you want to do. YouTube too.
I was checking into because I had to run power 2 miles at a price of $150,000. And that was more than 30 years ago.

[peakbagger]

Have you considered a wood boiler with a solar hot water collector system, combined with a large storage tank you could run that off grid, especially with some passive solar design into the house.  

I had thought about running pipes around the fireplace, and some sort of solar hot water. But how hot can a solar water heater system get if it's in the 20's outside?

Standard solar hot water collectors at best will raise the temperature of the water about 80 degrees F over the daytime temperature. So 20F might give 100 F water so you would need a backup. I have had SHW for 25 years and its great spring summer and fall but in the winter it needs a backup. I have a wood boiler for winter heat (and minisplit for spring/fall and use the excess heat from the wood boiler to boost up the solar hot water temp in winter. Note, that is fine for domestic hot water, but to heat a house with it requires a roof full of SHW panels whihc are not cheap unless you buy them used. If built right and installed properly they last for a long time (30 plus years), but the controls and check valves can fail at some point and many people abandon them as there are few qualified contractors that work on them.Eventually when someone needs a roof done they get taken down. I can usually find several people selling old panels on Craigslist for cheap. 
There are evacuated tube collectors that can get a lot hotter but they trade off heat for quantity. They are also notoriously unreliable, many of the manufacturers went out of business dealing with warranty claims. If I use my thermal camera on most evac tube arrays. a quarter to a third of the tubes are usually dead. 
if you have the firewood available and do not mind the exercise, hard to beat an indoor wood gasifier with adequately sized storage with a couple of mini splits fed from a PV system. With the new LiPO based batteries, and hybrid inverters off gird power with couple of days of storage is getting practical. The trade off is a wood based heating system with storage is $20K, mini splits are 3K a piece and a solar power system with 3 days of storage is $40 to 50K. 

[Southside]

100F water would be just right for radiant heating.  If you are going to build it, do it right the first time. 

[mike dee]

I am building my retirement home and want to be fully off grid. My property is so remote that the electric company wants 55k to run power to me so off grid just makes sense. I am considering using geothermal for heating in east Tennessee but know very little about it. House will have a walkout basement and 2 floors above. The basement will be in the side of a mountain and someone suggested that since I have to dig why not dig a bit more and use geothermal. Sounds like an idea but it can't be that simple.

Please educate me about geothermal the plus and minus and what to pay attention to so that if I do it I do it right and only have to do it once.

Geothermal works good, is very efficient, and very expensive. You will need a ducted air handling system which will add to your costs. Cold climate air sourced heat pumps are cheaper, easier to install, and require no duct, only a drain at the internal unit for running A/C. My cold climate mini-splits run down to -30oC.
A comment on "off-the-grid". My neighbour has a 1km long driveway and decided to go off the grid using solar, wind and a backup propane powered generator. Problem is that we don't get enough sunlight in southern Ontario to keep the batteries charged. He also saved money by not mounting the wind turbine high enough and we don't have enough steady wind for the unit to spin up to generate effective power. Off the grid living requires a major lifestyle change. My neighbour and family wasn't up for it and ended up filling their 2,000L propane tank on a weekly basis to supply enough heat and power the backup generator which ran most of the time.  
After a few years he ended up spending north of $100K installing a 1km long underground power line to run the house before selling the place. Turns out buyers didn't want to buy an off the grid home that didn't have access to relatively cheap and reliable power from the grid.

[Al_Smith]

I suppose if you wanted to live where the hoot owls romance the chickens you've got about two choices .Either make your own  electrical power or live like the  Amish .On the generator with no natural gas profane --er rather propane would be logical choice .It's not going to be inexpensive no matter how it's done .
Some time ago a person on one of the forums liked to do things the old fashion way .Bless his heart but I asked him if he wanted to do that how does he expect to get on the internet ? No reply to that  :D I've never heard of a wood fired computer but they say anything is possible .

[kkcomp]

To clarify and probably important  I was thinking of looking at water to water Geo for radiant heating. I have a lake but I saw somewhere that loops should only be 300 feet and the lake will be further away than that.

[Al_Smith]

I suppose it would depend on the capacity of the loop circulation pump which can be connected in tandom .My situation it was 54 degree well water with a half HP pump that took 4.5-5 gallon per minute of water .If in doubt most likely Google can find the flow charts .I've got them some place from both Water Furnace and Hydra -Delta .Exactly where I have no idea .However that doesn't solve the problem of no electrical power except perhaps a generator of some kind . 

[Al_Smith]

Here's another option if the electrical situation is met .I have an old 3 ton "Tetco " unit,one of the first geo systems .It used a water A coil thing for AC and the refrigeration part  for heat .However if you had propane plus perhaps firewood that should do it for the  heat .

[kkcomp]

I suppose it would depend on the capacity of the loop circulation pump which can be connected in tandom .My situation it was 54 degree well water with a half HP pump that took 4.5-5 gallon per minute of water .If in doubt most likely Google can find the flow charts .I've got them some place from both Water Furnace and Hydra -Delta .Exactly where I have no idea .However that doesn't solve the problem of no electrical power except perhaps a generator of some kind .

Power is the easy one. A combination of Solar, Wind and Hydro

[Ianab]

To clarify and probably important I was thinking of looking at water to water Geo for radiant heating. I have a lake but I saw somewhere that loops should only be 300 feet and the lake will be further away than that.

Distance shouldn't be a huge problem, height difference might be. If I understand the system you would be pumping lake water to a heat exchanger at the house, extracting some heat from it, and then discharging the now chilled water back into the lake. No laws of physics being broken here.
it probably just down to efficiency of the whole system. A longer pipe would need to be buried deep or insulated so the water arrives at the house with some heat remaining, even in the coldest expected weather. If you have to lift the water too high, that's going to take a bigger pump, and so you lose efficiency. You also mention some sort of micro-hydro? If you can gravity feed water though the system that has to up your efficiency, especially if the hydro generates enough to run the heat pump.
Also might need some fancy control stuff to stop the system icing up, if you got the heat exchanger chilled below 0 C. 

I also think you want some sort of wood burner in the equation as well. That can help out with the hot water as well as house heat, and those are the 2 biggest items on the average power budget. 

[Sod saw]

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If you are building a new home I am going to assume that you will have running domestic water for a kitchen and perhaps bathroom.  Where will that waste water (etc) go?  Most building codes would require a septic system with proper size leach field.

Before you install the leach field pipes etc, you can probably use the same foot print to install pipes in the ground for your geothermal heat source.  Some one suggested that about 300 feet of pipe for each ton of load.  Good idea and 300 feet is about the limit for each run of pipe.  You can, however, run multiple runs of pipe under (6 to 8 feet deep) your leach system.  The bacteria in your leach field will help keep the ground a few degrees warmer (not frozen) and you can save money by not having to find another yard just for the heat source pipes.  Yes they use special pipes.

Start by over insulating your design.  Insulate under your basement floor as well as the basement walls underground (some folks think that I am nuts for worrying about basements).   Then have an engineer (architect) figure out your heat load in BTU's.  Convert that to tons of heating equipment.  You may need the help of someone who installs these kinds of machines locally to help with the math for your neck of the woods.

These heating systems use electricity so you will also need a constant supply being generated some how.  If you go with wind, remember that the lowest part of the blade path should be 30 to 50 feet above the highest tree or building within a couple hundred feet.  The larger the diameter of the blades will produce more power at less cost per watt.  The larger blades will also require taller tower to keep above surrounding items.

Solar has come a long way in lowering the cost per watt and will decrease more in the future but don't let that future decrease prevent you from installing it now.  If you Wait for the perfect time, it will never get done and you can lose the enjoyment of living in your new home.

Where we live, I don't worry about air conditioning, but, you are somewhat warmer in Tenn.

have fun with your project


.

[kkcomp]

.


If you are building a new home I am going to assume that you will have running domestic water for a kitchen and perhaps bathroom.  Where will that waste water (etc) go?  Most building codes would require a septic system with proper size leach field.

Before you install the leach field pipes etc, you can probably use the same foot print to install pipes in the ground for your geothermal heat source.  Some one suggested that about 300 feet of pipe for each ton of load.  Good idea and 300 feet is about the limit for each run of pipe.  You can, however, run multiple runs of pipe under (6 to 8 feet deep) your leach system.  The bacteria in your leach field will help keep the ground a few degrees warmer (not frozen) and you can save money by not having to find another yard just for the heat source pipes.  Yes they use special pipes.

Start by over insulating your design.  Insulate under your basement floor as well as the basement walls underground (some folks think that I am nuts for worrying about basements).   Then have an engineer (architect) figure out your heat load in BTU's.  Convert that to tons of heating equipment.  You may need the help of someone who installs these kinds of machines locally to help with the math for your neck of the woods.

These heating systems use electricity so you will also need a constant supply being generated some how.  If you go with wind, remember that the lowest part of the blade path should be 30 to 50 feet above the highest tree or building within a couple hundred feet.  The larger the diameter of the blades will produce more power at less cost per watt.  The larger blades will also require taller tower to keep above surrounding items.

Solar has come a long way in lowering the cost per watt and will decrease more in the future but don't let that future decrease prevent you from installing it now.  If you Wait for the perfect time, it will never get done and you can lose the enjoyment of living in your new home.

Where we live, I don't worry about air conditioning, but, you are somewhat warmer in Tenn.

have fun with your project


.

Very good info and ideas, thanks

[Joe Hillmann]

An air to water heat pump can be 300% efficient.  Which means one watt of power used in the pump can give you 3 watts of heat energy.  Which is really good. But even at 300% efficiency it could easily take 7,000 to 10,000watt hours per day to heat a modest, well insulated home in Tennessee. 

In the winter(when you need heat) you can plan on 3 sun hours per day.  So you need 2000 to 4000 watts of solar to run your heat pump on an average day(on cold  or cloudy days you will run out of power and need a back up system)

But your system also needs to run at night so you you also need some way to store 6000 to 9000 watts of power in a battery or in thermal mass so you can heat your home when the sun isn't shining.

One way to reduce your needs is to build small, insulate well and take advantage of passive solar design.  That way you can get by with less need of the heat pump and less solar to power it.




There are several other types of geothermal heating as well.

The simplest is just earth sheltered, it helps keep the house warmer in winter and cooler in summer.  It has down sides though, you have to plan in advance to prevent damp and mold and it feels like living in a basement.

Another option is to bury air tubes in the ground then all summer pump hot air from a green house through them and warm up the ground as a battery.  Then in the winter blow house air through them and back into the house.  The air picks up heat from the ground and returns brings  it into the house.   Here is a video on the system used in a greenhouse Nebraska retiree uses earths's heat to grow oranges in snow - YouTube

[Sod saw]

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WOW !   

This is great.  Thanks for the posing of the video.  You (they) have given me ideas (dangerous for me to have ideas) for my daughters place (greenhouse, not home).

We were thinking about geothermal to provide the heat for her home but the math did not work out since the smallest compressor would have been too big (provide more BTU's than her house required) for both heating loads as well as air conditioning.

She therefore has settled upon air to air heat pump that can be sized more closely to her needs.

.

[Al_Smith]

Depends on how much money  
you want to spend on a geo system .Water to air are or can be  made just about like variable compresser air to air  .Just keep in mind the more bells and whistles they have the more likley more trouble you might have .You might save some money long term if everything works but it might take half a life time to realize any savings .

[backwoodsboy]

A few thoughts:
If you plan to berm your basement inside a hill, if you can, aim it south for solar gain. Jim Carter gave us a $4,000 tax credit for doing that, which is what we were going to do anyway. That credit isn't available any longer, but there are more government incentivised renewable energy programs. Super insulate each story. You can build your own stress skin panels using rigid foam glued together and wrap the entire structure without stud breaks every 16" OC.
Buy an old Mercedes diesel, or just a plain diesel generator. With a conversion kit run either of  them to produce usable electricity from biodiesel.  
Find a source of cheap wood (pallets) and burn it in a high efficiency wood stove with a catalytic combustor as backup.

[backwoodsboy]

Have you considered a wood boiler with a solar hot water collector system, combined with a large storage tank you could run that off grid, especially with some passive solar design into the house.  

I had thought about running pipes around the fireplace, and some sort of solar hot water. But how hot can a solar water heater system get if it's in the 20's outside?

Use a passive solar water heater as long as you get a net gain. Then, turn it off, or run the lines into whatever you will be using during the coldest times. Just storing inside will raise its temp from the 40s to the 60s and or the 70s (room temp). That saves you the cost of raising the temp 20 to 30 degrees before you have to begin to heat it. On clear sunny days when it is in the 20s, you may get more temp increase than that. Cover your "box" when the sun sets with insulation. *Use a light censor to detect dark/light to open/close insulating cover. Build the box stuffed with insulation. Build a wood run outdoor furnace (with rocks) to heat water and the structure simultaneously.
Watch Richard Proenneke, a former diesel mechanic and, "an American self-educated naturalist, conservationist, writer, and wildlife photographer who, from the age of about 51, lived alone for nearly thirty years (1968–1998) in the mountains of Alaska in a log cabin that he constructed by hand near the shore of Twin Lakes. Proenneke hunted, fished, raised and gathered much of his own food, and also had supplies flown in occasionally. He documented his activities in journals and on film, and also recorded valuable meteorological and natural data."
Moving story. Inspirational.