[zootjeff]

I have been looking into geo thermal heat pumps and the options with vertical vs horizontal loops. If the ground is always 55 degrees F, then in theory you have 55 degree water coming in from the ground, and 68-80 degree water coming from inside the house, depending on how warm it is.. Assuming that you size the loop to have enough heat transfer with the ground to actually cool the water to 55 degrees F, it should work, right?

So,
1. would it be possible to put in several bore holes, or some long horizontal loops in the ground.
2. Run High Density Poly Urethane tubing in them.
3. Add grout, or don't add grout..
4. Cascade the loops together back near the forced air gas furnace into one big loop.
5. Construct or modify an evaporator heat exchanger for the forced air system so that it circulates not refrigerant, but just water with antifreeze in the geo tubing loops.
6. Put a pump in the middle.

So now you have a cooling only Geothermal system that only costs the amount of energy to run the pump.

Seems like it would work just fine?

What are your thoughts?

In a typical geothermal system, I've been seeing them recommend one 150-200 foot bore hole per Ton of cooling. A 2.5 ton system like my house would require might take 3 bore holes 150 feet each if I was using a compressor system.

In a compressor system, what is the temperature of the water going into the ground measured right after the compressor, and what is the temperature coming out of the ground after going through the geo loop? I assume it doesn't get all the way down to 55 degrees F..


I assume in my method, I might need twice the bore holes to get the same performance of cooling, but even still, it should be more efficient, because you're not running a compressor..

-Jeff

 

[JBM1000]

I suppose it might work rather well, but in my humble opinion why spend a huge amount of $ just to find out? I guess you could opt for going comp after the fact tho!!

 

[Special-K]

This is an interesting concept that I'm seen brought up many times. While it is theoretically possible to cool your house this way, you don't really have enough temperature difference with 55* water to dehumidify or to easily reach air temperatures of the lower 70*.

I think you would need to use a huge coil with a counterflow design to get a TD worth fooling with.

 

[renaissanse man]

This is an interesting concept that I'm seen brought up many times. While it is theoretically possible to cool your house this way, you don't really have enough temperature difference with 55* water to dehumidify or to easily reach air temperatures of the lower 70*.

I think you would need to use a huge coil with a counterflow design to get a TD worth fooling with.

What he said. In a normal a/c system, you need a 40 degree evaporator. The load in the space would raise the loop water temp, so if their was any load at all, the incoming water would be above 55 degrees. I don't have a psyc chart in front of me , but a 55 degree dew point at 75 degrees is pretty humid.

 

[thoglow]

This is an interesting concept that I'm seen brought up many times. While it is theoretically possible to cool your house this way, you don't really have enough temperature difference with 55* water to dehumidify or to easily reach air temperatures of the lower 70*.

I think you would need to use a huge coil with a counterflow design to get a TD worth fooling with.

Bingo.You can't dehumidify.

 

[Special-K]

As an experiment, seems like you could use a 55* water source on a system with a water cooled condenser and then also use the cool water as a pre-cooler in the air flow before the evap. Seems like you could use an oversized coil...say a 4 ton coil on a two ton condenser and set the evap up for a lower TD.

I would think you could get about double the normal BTU rating from your compressor this way.

Somebody try it, just remember me when you make millions from it. My name is Navin Johnson.

 

[Mstrav]

you could use it for cooling to a point, you would have no humidity control and for the heat you would need a re-heat coil. lots of the high rise systems dump tempered air through the trunk and then temper that to what the space wants. His idea is nothing new, just not practical and he would still need a boiler to re-heat the air and temper it. fan would have to run continous and so would the pump(s).

just go with a water furnace, hydron module, climate master, carrier or whatever brand you want, all you are saving is a few bucks on electricity and you would need gas and more up front costs for sure. you would still have to buy an air-handler, a coil (for heat), coil for cooling( need some kind of water to air exchanger), a boiler, more pumps and some type of controls.

just buy a water source heat pump and be done, you dont have the budget of a high rise building.

matt

 

[jayhawker]

I know on lake Taneycomo the water is a consistent 45 deg. it is comming off the bottom of Tablerock lake thru the power plant discharge. People used to pump the water thru AHU's with water coils to AC the homes on the lake (more of a river that leads to Bull Shoals lake than a lake) the Corp of Engineers made all the people take them out, claimed it was causing "thermal polution"

 

[karsthuntr]

The water in a geothermal unit will get to 90 degrees by the end of the cooling season. In order for your system to work efficiently the amount of piping needed would cost more than the HP. IMO

 

[hvaccolo]

I used to do work for the water department, and at some of their remote pumping stations, where they have underground storage tanks, they would use exactly the setup you are talking about. Tanks that hold several million gallons of cool water, a pump and a fan coil unit. From the size of the ahu, I would guess it was probably about 25 tons ( if using chilled water), and the space temp in the summer would get to about 80 deg, w/ only about >10 def td. The funny thing is they used a Metasys to control this set up...talk about serious overkill.

 

[a0128958]

I just had a GSHP system installed a few weeks ago - Dallas, TX area.

The recommendation was one vertical hole per ton, at 300 feet deep each. This is what was done.

I have 8 tons, and thus that's almost a mile of pipe in the ground.

You can see a real time display of my system performance at http://www.welserver.com/WEL0043 - include historical graphs after real time display. (Temperature sensors are not thermally expoxy attached yet so effect of attic heat is excessive on temperature measurements at the moment. Power consumption monitoring will be added next week.)

Best regards,

Bill Neukranz

 

[aircooled53]

Water temperature /without compressor????

If you have a coil or heat exchanger with 75 degree are blowing across it with water flowing through the coil, it will heat water 8-10 degree's.

Now you could install your loops and have an air handler with variable drive and pipe to geo-thermal split with de-superheater and compressor and your amp draw would be about 5-7 amps total on compressor and motor. The amount of humidity removal would be better as variable drive would keep indoor coil very frosty or cold . The amount of energy used would be about 54% below what a normal air-to-air machine would cost to operate at same design temperatures indoor.Also your domestic hot water would also be heated by the same geo-split system. I have about 12 systems in Fort Worth area I installed and maintained for many years with little or no problems and customers love them.

 

[bmac]

I'm not sure about the ground loop, but I have a few customers with an open loop system where in the cooling mode all it does is run the domestic water through a coil and out to a pond or well. They all work fine. The only energy they use is the pump on their well. In the heat mode it runs the water through a heat exchanger like a typical geo.