Teach me about geothermal energy

hoofinitnorth · #1 02/13/07, 04:34 PM

I've read a little on this but I am really confused. How could one harvest heat from a lake or the ground that is COOLER than the air temperature (think cooler water, cooler caves, etc.)? What am I missing here?

Apparently some people in Alaska are trying geothermal harvesting but I think they are near natural hot springs or something...??

MELOC · #2 02/13/07, 04:37 PM

a compressor is used to "extract" heat from the cooler water. the water returns even cooler than it started.

hoofinitnorth · #3 02/13/07, 04:49 PM

OK... I guess that makes sense. But how would it get enough heat to be above air temp.?

And if you are taking earth heat vs. water heat (or do they just call it earth heat but they really dig down to water)?

Explorer · #4 02/13/07, 05:05 PM

I'm going to give this a shot, hope my explanation makes sense. Ice forms from liquid water at 32° F. However, ice can get much colder. I recall some measurements recently in nature (not laboratory, where ice was -20° F. Now that is 52° difference and with the proper equipment (heat pump) that heat can be extracted and used for some other purpose, like heating your house.
Make sense?

hoofinitnorth · #5 02/13/07, 05:46 PM

Hmmm, yes I suppose. I guess I'm just missing the gap on how you get that 52°F difference to work at above ambient-water/ice-level-temps... lol Color me dense.

Steve L. · #6 02/14/07, 05:46 AM

Quote:

Originally Posted by hoofinitnorth

Hmmm, yes I suppose. I guess I'm just missing the gap on how you get that 52°F difference to work at above ambient-water/ice-level-temps... lol Color me dense.

What color is dense?

Seriously, though, how does your refrigerator cool things?

dcross · #7 02/14/07, 10:48 AM

My basic understanding:

Heat pumps are AC units that can be reversed, heat the house by pumping heat in instead of out.

They work well down to about 40 degrees F. and are popular in the South.

Further north, you need a source of "heat" that stays above 40, which the ground(below frost line) and groundwater do.

wy_white_wolf · #8 02/14/07, 11:50 AM

http://home.howstuffworks.com/question49.htm

momanto · #9 02/14/07, 04:42 PM

When Window Air. Cond. Units Go On Sale I Will Purchase An Extra One For My House. Put It In Backwards And Use It As A Heater. Way Cheaper And Safer Than Little Space Heaters Like I Have.

[will That Work?]

Runners · #10 02/14/07, 09:07 PM

Quote:

Originally Posted by hoofinitnorth

I've read a little on this but I am really confused. How could one harvest heat from a lake or the ground that is COOLER than the air temperature (think cooler water, cooler caves, etc.)? What am I missing here?

Apparently some people in Alaska are trying geothermal harvesting but I think they are near natural hot springs or something...??

Iceland
http://iga.igg.cnr.it/geoworld/geowo...ountry=iceland
How about 202megawatts of electricity and 87% of the homes heated by Geothermal energy?

Plus swimming pools, greenhouses....

How close do you live to a volcano...?

Steve L. · #11 02/15/07, 07:14 AM

Quote:

Originally Posted by Runners

REAL Geothermal energy production...
How close do you live to a volcano...?

Thanks for posting that, Runners. It irks me that people these days are confusing ground source heat pumps with REAL Geothermal energy!

hoofinitnorth · #12 02/15/07, 03:23 PM

Steve L. and Runners - see, this is what is confusing me...

And I guess if I understood how a refrigerator works I might not be asking about a heat pump! lol Still, one seems a lot different from another...??

Will check out those links, thanks!

Steve L. · #13 02/16/07, 07:20 AM

Quote:

Originally Posted by hoofinitnorth

Steve L. and Runners - see, this is what is confusing me...

And I guess if I understood how a refrigerator works I might not be asking about a heat pump! lol Still, one seems a lot different from another...??

Will check out those links, thanks!

A heat pump is just exactly that - a heat pump. It pumps heat 'uphill' - i.e. it takes heat from a place where it's dispersed (low temp) and 'concentrates' it (high temp). Your refrigerator pumps the heat 'out' of its interior into your kitchen. A ground source 'geo-thermal' heating system uses a heat pump to pump the heat that's stored in the ground around your home (soil temp is 'low', around 50°F) 'uphill' into your house, by taking a little heat out of a lot of soil and puting it in a small place (the inside of your house).

'Real' geo-thermal, on the other hand, is a lot more like using a fire. It relies on high temp water/steam (up into the hundreds of degrees F) drawn from fairly deep underground. The heat from this source flows 'down hill' into the place/substance you need to heat, just like the heat from a fire does. In Iceland/Alaska/Yellowstone this deep ground water is heated by large masses of very hot semi-molten mantle material that has worked its way close to the surface.

Metcalf · #14 02/16/07, 11:24 AM

Great technology!

Here is a great explination...

http://www.geothermalheatpump.com/how.htm

hoofinitnorth · #15 02/16/07, 12:23 PM

Thank you all! I understand it a bit more now!

perennial · #16 02/21/07, 09:58 AM

We installed a geothermal heatpump in our house we built last year - modular. It is a horizontal closed loop system. We also put in an 85 gal hot water heater - Marathon (rheem). I know - you'll all be horrified - but we like our hot water. However, this water heat is made entirely of some special plastic so it doesn't every need replacing - the tank is actually inside the the outercasing with insulation or whatever inside. It doesn't have an anode rod either and is warrantied for life.

Now the installation of our system and groundloop were o.k., but we've had ducting issues they did to the upstairs - they used flexline - which is cheesey, nasty stuff which can be squished easily like hours. Hubby has since replaced as much as possible with hardwall - another whole story.

So, our system hadn't been running as efficiently as it could and we shall now see a big difference after hubbies work.

Last summer though, we shut off our electric water heater breakers because when the system is heating or cooling we got a desuperheater thing for it that takes the extra heat and dumps it into our water heater. Last year we had water heater off for about 3 months and had plenty of hot water.
It takes excess heat when unit is cooling or heating and dumps into the water heater. Even now, we have one element off and the other one turned down and have as hot as can be showers.

We have a 3 ton e series premier water furnace unit with desuperheater.
wf has lots of info on their website.

I'll let you know when we have some real numbers for our system. The airflow/flexline was so squished in three places, that we used way more energy to make up for that so now that it's all unsquished and done proper, i'll be able to compare with last years #'s.