Almost free cooling with well water.

Hi
I have made a really crude Sketch of a cooling system using well water. You dont waste any water as the water just passes through the radiators and waters the plants etc.

I have a couple of problems!

1 - I do not know whether there will be enough airflow. I thought of supplementing it with solar powered cpu fans! What do you think?

2 - Mold growth due to condensation. Do you think this will happen? How can it be avoided? What is the easiest way to deal with this?

Can you foresee any other design flaws, how can it be improved?

Thanks alot

It works, but...

You have to use a fair bit of water to get noticeable cooling. Not bad if you are pumping it to the top of a swale system, but probably more water than you need for a few flowerbeds around the house.

You definitely need airflow!

Where are you? Condensation may be a problem, but if it isn't you should probably be using a swamp cooler.

R Scott wrote:It works, but...

You have to use a fair bit of water to get noticeable cooling. Not bad if you are pumping it to the top of a swale system, but probably more water than you need for a few flowerbeds around the house.

You definitely need airflow!

Where are you? Condensation may be a problem, but if it isn't you should probably be using a swamp cooler.

Could pump it into a swale or pond I guess, maybe a watering hole for animals.

I am in Cyprus, very high humidity here! The mold will be a big concern I think? Is it solvable?

So you think cpu cooler fans would be enough for airflow? Or maybe a black painted chimney on the south side of the house?

You have a good start, but I don't think your system will work very well as you have it drawn. A few questions:

1. What temperature is the well water?
2. How are you moving it from the well, through the pipes and to the garden bed?

Some observations:

1. In your drawing, you show drawing in outside air, and cooling it down. In order to do this, you will need to push some of the air in the house outside. If your cooling system is effective, the air inside the house will be cooler than outside, so you will be pushing cool air outside, where it has no value. Can you circulate cool indoor air over the water pipes? This would require a fan. While you will likely get more airflow through your system as drawn if you use a black painted chimney, this requires that you heat your cool air in order to induce airflow. If you do want to draw air in from outside, draw air from the cool side of the house.

2. Another option is to use a radiant cooling panel. This would not require any airflow. I have seen this done in a concrete floor.

3. Moisture - if you want to avoid mold issues, you need to manage condensation. In traditional air conditioning units, water that condenses on the coil is collected and then disposed of (usually there is a drain pan under the coil). With radiant cooling (as I suggest above), you would need to maintain the surface temperature of the cooling panel above the dew point temperature. You can do this by limiting the amount of moisture that gets into the building, (limit the humidity in the space), or by limiting the surface temperature of the cooling system. Do some research on dew point and relative humidity.

4. Moisture, Part 2 - one of the reasons that air conditioning feels so good in humid climates is that it removes the moisture from the air, and allows our bodies natural cooling system (sweating) to work better. If you use radiant cooling, or try NOT to remove moisture from the air, your space might be cooler than outside, but the air will still be full of moisture. You will need to do some experimentation to see what works for you.

Good Luck!

--
Karen

The way to keep mold away is to drain away the condensation, just like an air conditioner, with occasional cleaning with alcohol or vinegar.

I find that simply holding the cold water in tanks absorbs more heat out of the living space for a much simpler design. 55 gallon barrel sitting on a floor that can handle the weight with a water heater drip pan to collect condensation. Fill the cistern, let it "warm", then use it. Add a small pump if you don't want to haul buckets. Use it in the garden, use it in the toilets.

Thanks for the input guys and gals.
Ive improvised the design after listening to suggestions and a bit of thinking! http://imgur.com/IMefFT5
The radiators are not fed directly by the well, instead the cold water in the well is pumped to an underground storage tank. Then the water is pumped through the radiators with a low power DC pump (could be solar).
The reason for this is not to run the high power pump constantly, which in turn would reduce electric costs and you would use a fraction of the water to cool the radiators. The water could then be used in a drip system to water trees, plants etc.. Or could be directed to a pond or swale. If only there were was a way to pump the water in pulses? https://www.youtube.com/watch?v=igvEI13T07Y maybe this could be of use. I will research it a bit more.
Ive also added small fans infront of the radiators to induce airflow.
The well water in summer is ice cold, not sure how many degrees but it will give you brain freeze. With it being underground and all, I think it will be enough to cool the air down, especially at night. It could also work in reverse in winter as the well water is warmer than the outside air.
The only problem I see with this design is mold due to condensation on the radiators with the high humidity and all. But I am thinking of a drainage system to overcome that.
What are your thoughts?

Find a hot water to air coil that is used for heating. Install it into the the supply plenum of your furnace if you have forced air or make a plenum out of sheet metal and put a good sized fan in it. Install a condensate pan in the bottom of the coil (coil should be vertical). The condensate will form and run down the coil even with air blowing over it. If you are using a well you should try to run a two pipe system, one to the bottom of the well as the intake water and one dumping back into the top of the well for your discharge water. By the time the water gets sucked to the bottom of the well it should be cooled back down, a poor man's geothermal setup. The average ground Temp 8' below grade in the NE at least is 50-55*F. Your average discharge temp on an AC system is in the 50's with room temp at 70*F. Definitely worth the experimentation.

It's time to start using numbers and stuff.


Some background:
In America Heating and cooling is measured in BTU. British Thermal Units. ( http://en.wikipedia.org/wiki/British_thermal_unit ) 1 BTU is the energy required to raise a pound of liquid water 1 degree F in temperature.

A room sized wall mounted air conditioning system is can move about 12,000 btu of heat out of the space every hour. Sometimes AC units are labled in tons, a ton of AC is about 12,000 BTU/ hour ( http://www.energyvanguard.com/blog-building-science-HERS-BPI/bid/55629/Why-Is-Air-Conditioner-Capacity-Measured-in-Tons ). A standard full home AC unit might be able to extract 50k BTU/hour out of the home.


Now for the fun parts.

The amount of cooling you can get out of the water is the difference in temperature between the thing being cooled and the initial water temperature. The amount of cooling you done is the differenece between water temperature before and after the heat exchangers ( it'll be less than 100% efficient ).

The amount of cooling you can get is also dependent on water flow rate. At 1 Gallon per minute (a rather sad little well), or 60 gallons / hour the mass flow rate would be 8.23 (lbs/gallon) * 60 ( gallons / hour) = ~ 500 lbs / hour. If the source water is at 60 degrees f, and the discharge water is at 70 degrees f the total heat gained by the water and lost by the space is 10 ( degree ) * 500 (lbs) * 1 ( degree * lbs ^-1)= 5000 btu per hour in cooling.


If there was 10 gpm rather than 1 gpm, you'd get a full house AC solution of 50,000 btu / hour (and 14,400 gallons pumped per day ) . The tricky part is getting the heat exchanger sized correctly. It could be as simple an old car radiator in a plenum or as complex as a custom built copper heat exchanger.


use this handy calculator to get a rough idea of the interplay between the amount of air run across the exchanger vs the water. ( these are not the exchangers I woudl recomend for this application, they seem costly )

( http://www.exergyllc.com/calculator.php )
( http://www.exergyllc.com/products_sanitaryshelltube.php )
With a 01708-04 ( 17 series sanitary double tubesheet HX, 16 tube bundle)... ignore that for a while.
Values:
Tube side : air
flow Rate : 100 gal / sec ( not a small fan, but not too big )
inlet temperature : 80 degrees F
inlet pressure : 1 atm

Shell side : water
flow rate : 1 gal / min
inlet temperature : 60 F
inlet pressure : 1 atm

Results :

English Units
Heat Exchanger Model 01708-04

Tube Side Shell Side
Fluid Air Water
Temperature In 80 60
Temperature Out 74.14 69.77
Mass Flow 3484.05 499.45
Heat Transfer 4884 BTU/hr
Effectiveness 0.488


Almost 5000 BTU, awesome. It's about 1/2 efficient. For moderate cooling needs in a well insulated place this would be enough (assuming the water


Different exchangers will give different efficiencies. This is however a place to start getting a feel for the tradeoffs. I'd look for other exchanger calculators and cheaper solutions such as simply coiling some copper pipes in a plenum and testing out if there is enough flow for everything to be happy.

The solution gets better with colder source water and hotter air to cool. At 55 F inlett temp and 90 degree air temp, 8400 btu are removed and the outlet air temp is ~ 72 degrees.


Good luck!