Educate me on geothermal

[bandit86]

if you have a 55degree source, how do you get to have a room thats 76 degrees warm? I understand the cooling part.

i thought the whole point in geo thermal is to drill down couple hundred feet where the earth is warm and tap into that

 

[Xcusme]

Re: ducate me on geothermal

Re: ducate me on geothermal

if you have a 55degree source, how do you get to have a room thats 76 degrees warm?

You don't...without help from a boiler-furnace. The point is since you're starting at 55 degrees, it takes just a little bit more to reach the target 76 degrees and that's the cost savings.

 

[roscoe]

Re: ducate me on geothermal

Re: ducate me on geothermal

http://en.wikipedia.org/wiki/Geothermal_heat_pump

http://www.toolbase.org/Technology-Inventory/HVAC/geothermal-heat-pumps

Heat or cool for a couple bucks a day, no boiler needed.

Several co-workers are doing it in their new homes, and one relative retro fitted his house.

Will put this in my house if I ever build new or move to a different home.

 

[roscoe]

Re: ducate me on geothermal

Re: ducate me on geothermal

Components



An installed liquid pump pack
Geothermal systems require a length of buried tubing on the property, a liquid pump or a multi-pump-pack and a water-source GT (GeoThermal) heat pump. It is generally unnecessary for use with any Expansion tank, as most applications with a reservoir of 3-5gallons about 4 ft above the little 200 watt pump(s) need no pressure nor pressure relief valves. The tubing can be installed horizontally as a loop field or vertically as a series of long U-shapes (see below)in a continuous single plastic pipe or multiple for building with an in-ground, OR in-building header, much like exhaust-pipe headering. The purpose of the tubing is to transfer fluid for natural physics to therewith exchange heat to and from the ground. The size of the loop field depends on the size of the building being conditioned. in 55-52 degree damp conductive ground temperatures -Typically, one loop (400 to 600 feet) has the capacity of one ton or 12,000 British thermal units per hour (BTU/h) or 3.4 kilowatts. An average house will range from 2 to 6 Compressor-tons (7 to 20 kW) of capacity (to ~4400 sq.ft. homes over half-insulated basements, or well-insulated slab foundations).The second component is a liquid pump or multi-pump-pack, which sends the water through the tubing and the GT water-source heat pump.Some are built right inside the GT unit for ease of imstallation and are accessible.Earth-Coupled GT heat pumps are the units that replace existing furnace or boiler units. The ECL (Earth Coupled Loop) GT(GeoThermal) Heat Pump is to where the usually 70% "FREE" heat from the tubing is transferred from the Earth or to it for to heat/ heat Hot Water by PRIORITY DEMAND (instantly) or to Cool the structure.Heat pumps have the ability to move refrigerant through a piping system in-to/out-of tempered-(different-temparature) reservoirs/spaces/media and EXCHANGE thermal energy it to another location via the refrigerant and or in conjunction with fluid or air as a media to another space/ reservoir/floor-heating distribution system, etc. In "Air Conditioning 'A/C' as Cooling- sometimes not much of the heat energy, noted by as an increased temperature- from the Cooling mode- remains in a localized GT ECL after ~ 30 days/ residentially if the ECL is in good wet conductive soil.Some of even heated ECL's to 103-degrees f have been found near the origional 52-degree starting point within 40 days after being off-line on 20-ton GT A/C -an office Cooling system -loaded ! (on-line---over heated a little) Loaded- for 3-weeks delivering ~22 'TONS' of heat to the ECL of vertical boreholes (like wells) while running through 3100 ft of 3/4" piping.
Another example of a heat pump is a refrigerator;
heat is removed from the refrigerator's compartments
and transferred to the outside.

 

[bandit86]

Re: ducate me on geothermal

Re: ducate me on geothermal

Why not dig down where its warmer? Then it would be 100 % free

 

[OldePharte]

Re: educate me on geothermal

Re: educate me on geothermal

Why not dig down where its warmer? Then it would be 100 % free

Considering the "average" thermal gradient is 1 degree per 60 feet of depth, and given that at 3 feet, depending on your location and lack of a near-surface geothermal heat source, the temperature does not get below 32 degrees, to get to a 72 degree source, you would need to drill down 2,400 feet; that is raise the temp from 32 to 72 degrees or a 40 degree rise.

My guess it would be prohibitive given the rate of return would be in multiple decades.

The problem I have with geothermal, is the cost. Where I would use it is all rock, so water-based would be the option. The payback, again, is in decades. Only the rich or young can do it in my area.

 

[ED21]

Re: ducate me on geothermal

Re: ducate me on geothermal

The heat pump that you would use with a geothermal system only has to convert 55 degrees to 70, rather than down to freezing or below. And when the temp get much below freezing you need a backup heat source which is often electric resistance heat strips in the air handler, which can really made your electric meter spin.
The same for the a/c side of the heat pump. Instead of trying to convert 90 degrees outside to something comfortable, you are using a lower ambient temp to run the system.
The bottom line is that the whole system is more efficient and cheaper to run.
In Md. the payback for the system is usually 7 or 8 years. The big cost is drilling the wells. A ballpark around here is 1 ton of cooling per well. Ground loop systems just bury the line in the yard & take a lot of trenching. I don't know much about that method.
At least backup heat isn't needed. I also wonder about the longevity of the below grade components, but with the well systems at least the well isn't going anywhere unless the water table realy drops.

 

[bandit86]

Re: ducate me on geothermal

Re: ducate me on geothermal

You don't...without help from a boiler-furnace. The point is since you're starting at 55 degrees, it takes just a little bit more to reach the target 76 degrees and that's the cost savings.

so why not just reheat the air in the room, it's already at 74 degrees

 

[Xcusme]

Re: ducate me on geothermal

Re: ducate me on geothermal

so why not just reheat the air in the room, it's already at 74 degrees

Reheat the air...sure why not, that's what everyone does now...There's only one small problem. Heat loss, every structure has some amount of heat loss, even super insulated homes. Since there is no perfect insulator, you'll have heat loss or heat gain. The less the insulation, the greater the heat loss....well..that's not entirely true. Better put, the greater the temperature differential between the inside and outside , the greater the heat transfer, either in or out. Insulation slows this transfer. If both sides of the wall are at the same temperature, then no energy moves in or out.

Any heat source, furnace, boiler replaces the lost heat. The greater the loss the more often the furnace fires to replace the lost BTU's.

 

[mscher]

Re: Educate me on geothermal

if you have a 55degree source, how do you get to have a room thats 76 degrees warm? I understand the cooling part.

i thought the whole point in geo thermal is to drill down couple hundred feet where the earth is warm and tap into that

Geothermal is not a 1 for 1 energy exchange.

The 55 degree water is only used to help create a "heat exchange" in the geothermal heat pump compressor.

The compressor then heats it's own refridgerant to a much higher temprature, often over 100 degrees. This is where the hotter air is drawn off to heat the home.

In very cold weather, separate electric heat strips may be need to utilized to assist in heating the house, as other have stated.

 

[v1_0]

Re: Educate me on geothermal

if you have a 55degree source, how do you get to have a room thats 76 degrees warm? I understand the cooling part.

If we are talking about a "heat pump" then the heating and cooling part is pretty much the same.

What we have going on is based on the principle that a gas will 'give off' heat when it is compressed, and 'take heat' when it is expanded.

So, inside the heat pump there is some sort of gas (freon substitute, etc.)

If we want to heat a house, we compress (give heat) the gas inside the house, then allow it to expand outside of the house (take heat).
If we want to cool the house, we allow the gas to expand (take heat) inside the house, and compress it (give heat) outside of the house.

In (currently) normal systems, the outside unit of the heat pump has a fan, compressor, and radiator. It's either 'giving' or 'taking' heat from the surrounding air - then pumping the freon (substitute) into the house where the other half of the transaction takes place.

If you understand that, then it just becomes a matter of understanding that a geothermal heat pump uses the ground to cool/heat some liquid to around 50 degrees. That liquid replaces the outside 'air'. This is a tremendous advantage (20 degrees worth) on a cold day, when the outside air is 30 degrees.

Standard heatpumps will switch over to heat strips when the outside temperature drops below a certain point - the system will use less energy to heat with the strips than with the pump.

-V

 

[bandit86]

Re: Educate me on geothermal

ok, starting to see the light. I know how air conditioners work, wasnt sure how that principle could be used to heat the house when used with geo thermal.

does soeone haver a draving of how the air exchanger is set up, what's poutside, what's inside?

 

[ED21]

Re: Educate me on geothermal

A heat pump is just an air conditioner that can operate in reverse. The geothermal part just makes the heat pump work with more efficiency since the the temperature of the earth is a constant 55 degrees more or less.
The outdoor unit and the indoor air handler look the same as an air conditioner without the furnace.

 

[mscher]

Re: Educate me on geothermal

A heat pump is just an air conditioner that can operate in reverse. The geothermal part just makes the heat pump work with more efficiency since the the temperature of the earth is a constant 55 degrees more or less.
The outdoor unit and the indoor air handler look the same as an air conditioner without the furnace.

Most geothermal units replace or install where a current furnace would be. They are attached to a verticle/horizontal ground water loop, or pump-and-dump water well. There are no other outdoor units.

 

[ED21]

Re: Educate me on geothermal

I stand corrected, their is no outside unit on geothermal. I was thinking of a standard heat pump.

 

[gonefishie]

Re: Educate me on geothermal

I'm planning on having a good size pond at my next house and am planning on using geothermal via the pond. What is/are the advantages of this set up versus other geothermal methods other then having a fishin hole in my backyard?

 

[aspeck]

Re: Educate me on geothermal

I have geothermal and would never have anything but! Built new and priced conventional oil heat ... $6,000 for the package (duct work and all), but no A/C. $9,000 for an air-to-air heat pump giving me A/C. Or $13,000 for the geothermal unit. Additional cost was in the 3 100 foot wells that were dug to be the home of the vertical closed loop system.

2400 sq. ft home, 2 refrigerators, 1 freezer, electric washer/dryer, family of 3, we do lots of entertaining, electric hot water heater, neighborhood requires dusk to dawn external lighting, basement needs dehumidifier running constantly, aquarium requires constant electricity, keep hours at 70 in winter and 74 in summer, electric (including heating/cooling) averages about $125 per month.

As already said, it is a refrigeration unit that runs in reverse for heating (think of the bottom of your refrigerator where the hot air is blow from the condenser coils - that is where the heat comes from). But you are drawing the heat from a constant source. The "hot air" blow from the registers is about 35 degrees warmer than the interior temp. It is not a "quick recovery" heat source - if you want that you need to use the electric back-up coils.

It is one of the least expensive to operate heat and A/C sources there is available. Definitely a great way to go and I probably recouped the cost of the unit already (5 years) when looking at the cost of heating oil last year. I would do it again in a heartbeat.

BTW, we also have geothermal in our church ... in the main church building that was built in 81 we installed it ... older models but work great still, very little maintenance. Put it in our 20,000 sq ft multi-purpose building in 94. Very little maintenance and average cost of electric per month is $500 (large walk in freezer, large walk in refrigerator, gym lights on every day, 3 offices in use each day, person in building 24/7, 2 electric ranges, electric washer/dryer, etc).

 

[aspeck]

Re: Educate me on geothermal

gonefishie, you will be burying the pipes in the bottom of the pond ... what is the average water temp at the pond bottom ... the colder it gets, the less efficient the pump will be. Verticle closed loop is the most efficient, followed by horizontal, if the ground temp (or water temp) is warm enough. Water makes a better conductor than dirt, so a wet soil will conduct the heat to and from the pipe better than a dry sandy soil, and of course, water is best, if the water is warm enough.

 

[mscher]

Re: Educate me on geothermal

I'm planning on having a good size pond at my next house and am planning on using geothermal via the pond. What is/are the advantages of this set up versus other geothermal methods other then having a fishin hole in my backyard?

Geothermal can also use a pump-and-dump setup, where well water is utilized in the unit, then dumped, usually into a pond.

It will keep a pond full year round, of relatively clear water.

 

[gonefishie]

Re: Educate me on geothermal

Well, I read up on it. The pond temp wouldn't be as high as the ground temp in winter time but less cost on install and there is a pond.