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But the ground is only 50 degrees or so. Do I need a furnace to raise the temperature to what is comfortable for me? Do I need a furnace for when it gets really cold out? No. Yes. No. It depends on your situation. It's like this: You CAN heat and cool your home with 100% geothermal. It is not difficult. It MAY, however, be much more economical to size your system to, say, 96% of your total heat load and have a back-up heat source to augment those bitter cold and windy days that happen from time to time. That way, you are running a smaller compressor and using less energy for all but 4% of the year.
But the ground is only 50 degrees. Doesn't the geo system only heat my house to 50 and a furnace raise sit from there? No, that is not true. I mean, the Earth here IS about 50 degrees. That part is true. Take a look at the Refrigeration Process page to learn more in detail how this is done but essentially, there is a compressor in your geothermal heat exchanger. The refrigerant that comes off that compressor is about 145 degrees---way too hot to touch! That hot refrigerant transfers it's heat to your home through an inside heat exchanger. After the refrigerant loses all of it's heat, it goes through a metering valve that makes it much colder---like your refrigerator or freezer. The cold part of the refrigerant cycle absorbs heat from the ground loop by the use of the ground loop heat exchanger and that heat is transferred into your home and the precess repeats.
I was told that geothermal systems would not work in this climate. It's too cold. Is that true? No. There are literally thousands of such systems in Wisconsin that perform phenomenally! Wisconsin has close to the perfect climate for year-round peak performance of ground source heat pumps. The 50 (or so) degree earth beneath our feet give us plenty of thermal energy in the winter and make a perfect heat sink to get rid of the unwanted heat in the summer!
Drilling geothermal holes in my yard is going to make an awful mess, right? Actually, that one is probably a yes. It some cases the mess is smaller but when all is said and done, your lawn can be restored to the point that no one will ever see the fact that a rig was there...until you show them the pictures. If you want to see examples, visit our geo gallery. Like every construction process, there is a mess during the project but it it better when it is all done!
I was told that an open loop system is the most efficient because the entering water temperature is warmer than from a closed loop. Is that true? No. Well, technically, the coefficient of performance can be a little bit higher but if you have (deep breath) a 1/2 HP submersible pump drawing just 6.2 amps at 250 volts running 45 minutes per hour at 13.5 cents per Kilowatt/hour, you will spend $101.25 for 30 days per month just to pump the water! That takes a real bite out of the "most efficient" argument! Then, if you factor in the accelerated cost of pump system replacement, you will find that "The Most Efficient" sales pitch may be accurate, but the question becomes, "Most Efficient for WHO?", you or the installer?
Why even bother to put in an open loop system then? Because it just may be the perfect solution for you! If not for you, then for your neighbor. There are places where an open loop system is the perfect setup. Take this example, for instance: a dairy farmer. He can heat his home with well water, pipe that same water out to his milk house where a heat exchanger can keep his milk cold, then another to keep his milk house warm, then the discharge water is sent out for the cows to drink! They were going to need the water anyway! Get more information on open loop geothermal systems here.
Which is more efficient, then. A horizontal field or vertical boreholes? Both. It depends on your specific situation. Some geologic formations will not allow a horizontal field. Some will make it cost-prohibitive for a vertical field. Sometimes it must be a hybrid or combination. In Black River Falls several years ago, there was granite ranging from 25 to 45 feet in depth but his lot was too small for a horizontal system. We put in 25 holes to the granite and his system has worked flawlessly! I call it my "sewing machine" job. On another project in Manitowoc County, the original spec was for 7 180' holes. There was a formation that I was concerned about between 85 and 105 feet that might allow the drilling process in this case to impact the neighbors wells---and not in a good way! So I put in 17 80 foot holes. This prevented the drilling process from disturbing the neighbors wells and happy neighbors are way better than unhappy neighbors, right? All things being equal, the best system is the best for you.
But on a horizontal system, doesn't the frost go down pretty deep and then your field freezes? It could. But that is why you circulate a biodegradable antifreeze solution. Typically, you will have more linear footage in a horizontal system than in a vertical field to compensate for that fact. The Earth's temperature will fluctuate seasonally down to about 20'. Even if it does freeze, though, you can still exchange heat from frozen earth. You can, theoretically, pull heat out of anything above absolute zero (-459.67F) but I don't want to be around to try that.
Vertical fields (that is what I do), in Wisconsin, will also almost always be at some point, in the static water level and wet earth transfers heat much more readily than does dry earth. The drilling in Wisconsin, because we have been graced with so many glaciers in our past, tends to be problematic in some places and terrible (read: expensive) in others. So, in some cases, even if the EFFICIENCY of the system is a little bit better, the added cost to install vertical boreholes may not be worth it. Or it may take a long time to make up the difference.
It comes back to the fact that the best choice for you is the best choice for you.
Geothermal systems are very expensive, right? That depends on how you define expensive. There is a sizable up front cost, yes, but very often, the savings to your monthly utility bills are more than the payment to service the loan. That means that, every month, you save enough on your utility bills to pay for the cost of the geothermal unit and still have some money left over!