Someone please give me a quick education in geothermal

[Skidmore]

energy for residential use. How does it work? Can you convert a natural gas furnace or do you have to start from scratch? How costly are these systems? Can they be used anywhere or do you need to be living in certain areas for them to work best?

[FSogol]

1. They save on your electric bill, but

your installation costs will be double since you will need ground loops. No, a standard furnace probably could not be used. You would need a ground source heat pump (similar to a water source heat pump). The thing that makes it different than a standard heat pump is that instead of an outdoor condensing unit, you would have loops going into the earth (horizontally or vertically) to reject the heat from the system. You also need a small pump to circulate the alcohol thru the loops. Nice system if you can afford the initial cost.

[EST]

2. What you are describing is not geothermal.

It is merely a heat pump, using the ground or water in a pond, instead of air.
They work best in areas of moderate temperatures, not North Dakota or south Texas.
A heat pump is just a sophisticated air conditioner, running backwards in the winter.
True geothermal consists of gaining access to the hot interior of the earth, easy in some places, impossible in others. and using that heat to heat a building.

[FSogol]

4. True, but he mentioned for residential use

Ground source equipment often gets lumped under the term Geothermal.

[phantom power]

3. How it works:

a "geothermal" system is, first of all, not like the geothermal energy we are used to hearing about.

A residential "geothermal" system is really just a larger version of your air conditioner: it's a heat pump. In this case, it pumps heat out of the ground to warm your house, or it can also pump heat from your house back into the ground, to cool it.

They require either a fair amount of area to run the heat-exchange tubing, or being able to drill down about 50 feet. A friend of mine had one installed when he built his new house. I believe it cost around $15K, but I've heard other people say $10K.

[MuseRider]

5. We are putting one in

but have not started yet. It is for a new house so I don't know any answers about converting. I will be happy to share any information as we go along.

We are sinking the coils (I do not know the terminology yet) in our pond but if you don't have that I think they can either sink in deep trenches or be sunk in deep holes.

Sorry, my husband is working on this part and he is not home for me to ask questions. I do know the initial cost is quite steep but you can recoup it fairly quickly. I think ours figured out to be even in 3-6 years.

The one thing I am disturbed about is that in order for it to really save you money, our system must run all the time. We are going to have to compromise quite a lot on that because I refuse to live with the windows closed all year long. I hate air conditioning but am going to have to learn to live with it more than I do now. They told me it would be much more expensive if we opened windows and shut off the system. We will have a lot to learn.

[skids]

7. Hrm that last bit sounds like backwards thinking.

...The part about not using it when you don't need it, that is. Just because the payback period is shorter that way doesn't mean you spend less money overall by not turning it off when the temperature outside is good for opening the windows. Better to take a longer payback period and spend less money.

Unless I'm missing something...

[MuseRider]

8. I am still trying to figure that out.

But, that is what we were told. ???

[Ready4Change]

6. More expensive than standard furnace/ac systems.

Better regarding energy costs, in my understanding.

Based on the fact that temperatures deep under the ground are very consistent year round. (57 degrees F?) The ground can handle huge amounts of heat transfer without changing that temperature much. (That's what the term "heat sink" means.) So, when you house needs heat it can pull it from the ground, and when your house needs to shed heat it can pump it into the ground.

To get at that underground heat sink one or more deep holes are drilled into the ground. I've heard of them as shallow as 40 feet and as deep as several hundred. Into these are are dropped loops of piping through which the heat pumps fluid is circulated.

In summer your houses air is cooled by transfering its heat into the pumps fluid. That fluid is sent underground, where it is cooled and returned back to the house to cool more air.

In the winter that process is reversed. Cold air is warmed by the fluid, which is pumped underground to pick up more heat.

I recently visited a house that uses a 2 ton geo heat pump system powered by a bank of solar cells. The people said it worked great. Better than their previous furnace/AC system. Temps at the time of the visit were moderate, so I can't verify their claims.

[dcfirefighter]

9. 'free' hot water during summer

The waste heat, normally dumped into the earth, is first used to heat your water tank.

In almost every case, it's better to turn HVAC off when no one's using it. Letting your house get warm/cold and having to pump it out is less costly than maintaining it warm/cold all the time.

[bananas]

10. Here's a post by someone who has one

There are also some good links in the thread.
http://www.democraticunderground.com/discuss/duboard.php?az=show_mesg&forum=115&topic_id=30284&mesg_id=30287
corkhead Donating Member (353 posts) Tue Sep-06-05 09:53 AM
3. I've got one
I have a Waterfurnace that cost about an extra $3000 over a regular one. I live in Michigan and keep my thermostat at 70 degrees year around, and my largest electric bill was about $100, in a dead of winter cold month. I highly recommend. Cheap to operate, and cleaner than burning fossil fuels. I would buy another in a heartbeat

[s-cubed]

11. ground source heat pump systems

BE SURE YOU HAVE A VERY EXPERIENCED INSTALLER. THE SYSTEMS CAN BE SCREWED UP ROYALLY BY AMATEURS. They can be expensive to install, depending on your situation. Some of the most cost effective installations have been at schools, where they had lots of land to put the loops in. Before you go to this expense, check out all the other ways you can reduce energy: windows, weatherstripping, insulation. These are often much more cost effective. Also, consider a condensing furnace: very efficient.

Go to aceee.org & look for links. National Renewal energy lab in CO, for example.