Low info on geothermal. Basic questions?

[Dunkopf]

I have heard of geothermal and discussed it a little with an engineer that I was talking to. He said that basically it is a duct system if you will that is placed in the ground at a depth where the temperature stays around 68 degrees. The air is then circulated through your house during the summer to act as AC, or in the winter it is circulated as heat.

The postings I'm seeing are talking about water.

My neighbor had a system put in and they dug a trench in a U shape that is approximately 200' out and then 200' back. Is this a geothermal system? Where does the water come in to play. I have also heard of solar water heating systems where they run water pipes on your roof and it supplements your hot water or warms your floor.

Can someone give a basic description of how all this works.

 

[SKR8PN]

Here is a pretty good link that shows a simple system layout.

http://www.groundswellgeo.ca/geothermal_how.php

 

[tortoise]

The loop field piping is filled with either chemical-treated water, propylene glycol or ethylene glycol, depending on what local plumbing code and groundwater rules are. The piping comes into the home where it connects to a heat pump, which runs on electricity.

 

[SKR8PN]

A friend of ours has an open loop system. It takes the water from his well, extracts the heat in the heat exchanger, then just dumps the water back out onto the ground. He must have a darn good well to be able to do that!!

 

[tortoise]

Open loop systems are tightly regulated and not allowed in many areas, FYI.

 

[Trucker Bob]

My Girlfriend is a plumber with a Geothermal company and has explained it to me very well.

Basically you are looking at a heat exchange system. Pipes are either drilled down to a depth of 150 feet (more costly) or laid down in a trench that is about 1200 feet long (much less costly). The pipes are filled with antifreeze and absorb the heat of the earth and then are run through a heat exchanging furnace (the largest cost other than Drilling) and you have heat.

The trench method is so much cheaper because you can rent the backhoe and do most of the work yourself. You will need to dig 10 feet down for the trench.

Two ways that the furnace is used are forced air, which is much cheaper if you are doing a retrofit, or in floor heating which should only be done with a new build.

Please do not quote me on all of the specs... She's the plumber, I'm just the truck driving mad man she fell in love with

 

[Marianne]

Hi Bob, and welcome!

The depth of the piping will be vary in different locations. Where we live, ambient temp (56 deg F) is at 4', but loops are put in at 6'.

We were going water geothermal originally, but in the end, cost factors nixed it. We had all the pipe installed, ductwork installed, etc etc. The only thing thing the company had to do was bring the unit out and hook it up - $10K. Eek.

The neighbor behind us has one. He has two deep wells, one to draw water, the other for return water - that one is pressurized. If I remember correctly, the system that we were looking at would go through 100K gallons in a short period of time (like a day??). None of that water could be exposed to air at any time.

Some people have done earth tubes using PVC pipe, for cooling and low grade heating. Condensation and mold were a problem..I always thought I'd still like to try it and put some heavy cord through it so I could pull a bleach/water soaked towel through it occasionally. But alas..

http://builditsolar.com has a lot of different passive solar water heating ideas for you to check out. Great site with tons of ideas, some cheap, some not so cheap.

 

[merlinraj]

geothermal energy can be extracted without burning a fossil fuel such as coal, gas, or oil. Geothermal fields produce only about one-sixth of the carbon dioxide that a relatively clean natural-gas-fueled power plant produces. Binary plants release essentially no emissions. Unlike solar and wind energy, geothermal energy is always available, 365 days a year. It's also relatively inexpensive; savings from direct use can be as much as 80 percent over fossil fuels.