|Re: Liveable temp/ geothermal||<– Date –> <– Thread –>|
|From: Tom Hammer (thammer302yahoo.com)|
|Date: Fri, 25 Jan 2008 22:24:15 -0800 (PST)|
Our family is investing in geothermal while we are waiting for Concord Ecovillage to be built, so I have some new information. I'm quoting Sharon's note below because some of what we've learned with a brand- new unit is different from the info she has supplied. Also, my background in physics teaching may help. Our system will be finished this Monday!
There are open-loop and closed-loop wells. (There are also horizontal fields, with no wells. Look up the wikipedia article for a more complete explanation and diagrams.) I believe all modern g.t. systems are closed loop now. That means no water is released into or pumped out of the ground water but instead a fluid stays in the plastic pipe. In the pipes a mixture of water and glycerol (in case it freezes) goes down 310 feet, is reheated to 55 degrees by conduction from the surrounding rock, and returns to the heat pump. The heat pump transfers the heat into your heating system, just like a refrigerator pumps heat from the inside of the box to the coils in the back (that's why the refrigerator coils in back are warm to the touch and why you are supposed to keep all the dust off them so the heat can be transferred out.)
Our well cost $4000 to dig. After the pipes were put in and pressure tested, the entire well was filled with grout, not gravel, so it's all sealed back up except for the pipes.
There is no place geographically where this system would not work, as far as I can tell, and my web searching hasn't found any geographic limitations.
I'm not sure what the best units are, but ours is a "Tranquility 27" by Climatemaster. I called 8 folks in our area who had similar units installed in their homes, and all of the homeowners raved about their system.
Another advantage I just realized is that heat pump technology doesn't have combustion occurring inside our homes. Combustion, unless installed with an outside air source, which is extremely rare, draws in huge amounts of air to burn the fuel in the typical furnace. This cold air is "sucked" in from outside through cracks in the house, and it is inevitable that it come in in order for combustion to occur. With a heat pump, there's no combustion (same with all-electric baseboard heat, but that's very expensive.) You can notice this cold air being pulled in by putting a moist hand near a closed window or an electric outlet and notice the cold draft that you can feel as soon as your combustion furnace comes on. The closer the window or outlet to the furnace, the easier you will feel the draft. There is also a threat of carbon monoxide poisoning if a combustion system malfunctions.
An extra benefit is that, during the summer, the direction of heat being pumped is reversed. We are having a pre-heat hot water tank installed, so the water going into our hot water tank will be much warmer than normal in the summer, and we won't have to heat it much to get hot water.
The research I"ve done says that at today's prices the cost per BTU is 1/10 that of heating with oil (our present system.) Not only that, but our electric company allows us to sign up to purchase electricity with wind-generated power, so we'll be heating and cooling our house without using any fossil fuels. Ironically, as soon as we tell them we are an "all electrically heated house", the price per kilowatt-hour drops significantly, too.
The payback period for g.t., which is crucial, in my opinion, is roughly 8 or 9 years if one is using oil heat, and the unit should last for about 30 years, according to users and the installer. In our area, 6 large university buildings at West Chester University are converting to g.t., digging about 20 wells per building. Wikepedia says "the U.S. Environmental Protection Agency (EPA) has called geothermal the most energy-efficient, environmentally clean, and cost- effective space conditioning systems available."
Tom Hammer Concord Ecovillage southern Chester County, PA Date: Fri, 25 Jan 2008 11:21:53 -0500 From: Sharon Villines <sharon [at] sharonvillines.com> Subject: Re: [C-L]_ Liveable temp/ geothermal To: Cohousing-L <cohousing-l [at] cohousing.org> Message-ID: <67BA1978-ED28-42BE-ADF7-D1C2FDDEFC74 [at] sharonvillines.com> Content-Type: text/plain; charset=US-ASCII; format=flowed; delsp=yes
I would love to get more information on Takoma Village's geothermal set up (and any one else who has geothermal).
Our set up was very bad. Done by a bad contractor who went bankrupt and was actually arrested on our property before installation was completed. (The developer apparently took the lowest bid.) Be sure to use a company that has been in business for a few years at least and receives good recommendations. A geothermal unit, for those who don't know, uses plastic loops filled with water that go deep into the ground in holes that are called "wells." The water circulates to HVAC units in individual homes. The circulation of the water is done by a pump on the side of the HVAC unit. The circulation needs to be adjusted so the water stays in the ground long enough to reach ground temperature. The water in our systems is about 65 degrees. Thus the HVAC unit only has to heat from 65 degrees and not the air temperature. In the summer, it just cools although there is freon and a compressor -- not sure why. It also has a back up heater in case it is very cold out. Some of our homes have disconnected theirs so their units just get colder instead of triggering the back up. Geothermal apparently only works in certain geographic areas but I'm not sure which, and I'm not sure of that information either. It came from an installer who did not know what he was doing else wise. In our system, we have an individual well for each unit. This is apparently not a good design because it means when a loop begins leaking deep in the ground, that well fails. If it is a leaking in the horizontal loop that goes from the home to the well it can be fixed in various ways. Some of our wells have failed and we have had to put two units on one loop. A better design, and the one used at Eastern Village, is to use a "manifold" that connects all the wells. It is essentially a big circular horizontal loop with various switches that control and redirect the water. (Sorry if these are not the correct names but you get the idea.) With this design when a well fails, all the units still get water. If enough of them fail, you eventually have to dig more wells but you at least have some service while you dig. The HVAC unit does not work without water. A well in DC costs $6,000 to dig. When we dig we will dig three to have back up. We are currently installing a manifold in the commonhouse basement because two wells have failed to that building. But our consultant says we had too many wells to start with so with a manifold we are fine. He is also recommending that we dig up the green and install a manifold but we are not likely to do that unless wells fail there. He recommends that at the same time we build a partially underground storage facility or something because the earth will already be removed. Our looper, Lester the Looper, says the loops he has seen fail are all factory sealed loops. He recommends that the loops be built by a looper. But now I think there are continuous loops so they shouldn't leak. The loops are sunk in a hole that is then filled with something-- I think gravel -- so theoretically they could be more easily dug out and a new loop sunk.
The best geothermal units are Water Furnace. We have Florida Heat Pumps which are sort of good, we are told. Braun has just bought the company so it will be easier to get parts and the quality will probably improve. Sharon ---- Sharon Villines Takoma Village Cohousing,Washington DC http://www.takomavillage.org
- Re: Liveable temp/ geothermal, (continued)
- Re: Liveable temp/ geothermal David Heimann, January 27 2008
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