Geothermal Cooling

[Stonefinger]

As a result of my location, I would like to propose the following space cooling scenario and would welcome any input or feedback.

The proposal in summation is this: To utilize existing groundwater @ 52 degrees (Constant and Abundant) in lieu of conventional refrigerant dx system @ 38 degrees for space cooling purposes.

The water would be pumped from underground, (Grade to ground water = 6') circulated through a heat exchanger, and the return "well" would be a 250,000 gal open pond on premises. A conventional air handler with associated ductwork would be utililized to force and distribute the air. I am not interested in a heat pump for 2 reasons:

1) No space heating is required
2) Initial cost of the heat pump

The system described, an open loop, could become a closed one with proper justification. The heat gain for the building has been calculated @ 58,898 btu/hr or 5 tons. Based upon this, the following questions are presented for thought:

1) Calculate material, type and size of the heat exchanger.
2) Calculate blower size and cfm.
3) Calculate the gpm flow through the heat exchanger and type of pump.
4) Determine the feasibilty of such a system due to the delta T (52 versus 38 degrees)
5) Determine the efficiency or SEER rating of such a system

While not exhaustive, these are some the questions that come to mind as I begin to design and fabricate this system. Any comment or suggestion from those in this field would be greatly appreciated.

 

[EdStainless]

http://www.nickelinstitute.org/index.cfm/ci_id/13091.htm

Do you mean like this?
Since the water isn't as cold as a refirig system would be you won't get as much heat transfer and your air volume will need to be greater.
You also need to consider that you won't get the same degree of dehumidification.

The eff is a good question. Since the only power input is your pumps and blowers it should look very nice.

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Corrosion never sleeps, but it can be managed.

http://www.trenttube.com/Trent/tech_form.htm

 

[ClydeMule]

Keep in mind that the temp comparison will not be between 38 and 52. SInce you are proposing pumping the 52F well water into a heat exchanger, the water on the fan coil side of the heat exchanger will be XYZ temp above the well water temp. Something like 5-10 F. So the comparision is between 57-62 F. Like ED said you will have to make modifications to you Air Handler to handle the warmer water, and make sacrifices on humidity control.

By using a heat exchanger, you have made it a closed loop. The open loop is on the well water side.

Why don't you use a 5HP water cooled condensing unit? Pump the well water into the condenser directly, or do your heat exchanger idea. That would be better bacuase the hard well water (assumption) with the hot tubes of the condenser could lead to some serious fouling.

If you go to swep.net check out their MINEX. It is a hybrid between a brazed plate and a plate and frame. It is a nice solution if you want a cleanable, economical, small, and corrosion resistant heat exchnager.

If you go to a dairy equipment wholesaler, you might be able to find a water cooled 5 HP condensing unit that uses a cleanable condenser. You won't find that from a regualar reefer wholesaler. I know I have seen one by Boumatic, but I dunno if they make them anymore. They do direct well water condensing all the time.

Clyde

 

[StoneCold]

Stonefinger
I hate to be the pessimist here but we are talking about 5 tons of refrigeration. I have that much at my house, costs about $70/month. Just go with a standard unit. I you were talking millions of BTU/hr then I would say go for it but just put in a little Trane unit and worry about big problems. You will be happier in the long run.

StoneCold

 

[Stonefinger]

EdStainless-
This is exactly what I am talking about. I had read about this and other cold water cooling systems after I began to question the need for a heat pump in my space cooling application. There must be a reason why they are taking suction so deep in these lakes (colder water, 40 degree F). I am going to find out the effciency loss for every degree over 40.
I had read just to get past enviromental, the Toronto project was 10+ years in planning and development. Here was one such concern: Since there is little to no light at these depths, lights had to be installed at the intake of suction pipe to discourage certain marine species living at these depths from getting too close to the intake and being sucked up by the pumps.

ClydeMule-

Humidity concerns are certainly an issue. The thought was to try and maintain a dry bulb temperature of 70,(dew point of 50) and relative humidity of 55%.

StoneCold-

Here is a four letter word you can add to your vocabulary: LIPA. That stands for Long Island Power Authority. This "not-for-profit" orginazation works vehemently to have it rates set at or near the highest in the country.

Pardon my green (pun intended) but my reasons for this are three-fold:

1) The average (3 estimates) for conventional central air with duct work was $23,400.

2) LIPA, courtesy of Governor George Pataki, offers a $800 per ton rebate for geothermal systems.

3) Provide an alternative to conventional refrigerant based systems.

 

[EdStainless]

Look hard at geothermal cooled heat pumps. You could run the well water closed loop. A loop of pipe down into the well and back out. That way you would have no well draw-down or water discharge concerns.
I have seen diagrams of systems that used some direct cooling and then a heat pump to finish the job.
The direct heat exchangers are usually modified plate units. The water is carried between pairs of plates, and there is a large gap for air flow between the water cooled sections.

= = = = = = = = = = = = = = = = = = = =
Corrosion never sleeps, but it can be managed.

http://www.trenttube.com/Trent/tech_form.htm