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Space Heating and Cooling with Home and Irrigation Water Usage

Ken Peavey

Joined: Dec 21, 2009
Posts: 2523
Location: FL
I've been thinking about this one for a while, but the old house had city water and with that, a city sewer bill.  The new place has a well and septic.  I can pump water until the ground caves in and the only bill would be the electric to run the pump.  This makes my idea a little more practical...

In northern Florida, water from the well comes out of the ground at about 65 degrees, even in the summer.  If the water can be directed to flow through a radiator with a fan moving air though the radiator, the air temperature would change to be closer to the temperature of the water, offering heat or cooling to whatever space into which the air is then directed.

Air temperatures reach some gawdawful highs in the summer, 93 is the average daily high for 3 months a year.  I'm a tightwad, so I keep the AC set at 80 degrees and only turn the thing on when I'm home and inside.  With a system in place as described above, the cooling effect would not be sufficient for more than a couple of small rooms.  Air humidity often is in the 80-90% range every day.  A significant amount of condensation can be expected on the radiator coils.  This would have to be addressed to prevent property damage.

Water demand of crops in the summer is high.  With a sandy soil that drains rapidly and an unrelenting sun directly overhead, irrigation is often required to support crops.

Although I have yet to see snow in the winter after 11 years in North Florida, I hear tell from those that know that it is not unheard of, occurring with slightly more frequency than Loch Ness Monster sightings.  Nonetheless, January will see nighttime temperatures dip into the 30s and even the 20s.  We get a few frosts each year.

I like to be warm.  I have proven this to my satisfaction.  65 degree water as a heat source will not be sufficient to heat my home to my level of comfort, but it would go a long way toward heating a garage, barn, greenhouse or workshop to an acceptable level.  Since the air moving through the radiator will be cooler than the radiator, considerably less condensation is expected.

Water demand of crops in winter is still high.  Crops can be grown all year in this climate, but winter is the dry season.  Rainfall is light.  Even with rain, the soil does not hold water. 

Lets put some math behind the idea and see how effective such a rig can be.
Drip irrigation tips generally operate with a flow rate of 1-2 GPH and a head pressure of 25 PSI.  A typical well around here can offer up 50 PSI at a flow rate of 3-4 GPM.  My water pressure is awful, but it is possible to do some tweaking to improve that situation.  Assuming I am handy enough to get the job done, an ultimate flow rate of 250 Gallons Per Hour is not unreasonable. 

Water weighs 8 pounds per gallon. 
250 gallons per hour moves 2000 pounds per hour.
If the device described above is able to transfer just a 10 degree difference in temperature, the amount of energy transferred would be about 20k BTU/hour. 

A fair sized window air conditioner would have about the same amount of cooling ability.
A couple of small electric space heaters would have about the same heating ability.

More extreme temperature difference between the air and the water would result in greater effectiveness.  The system would have to be big enough to handle the water flow.  Air flow could also be adjusted.  The system can be expanded in complexity to include whatever automatic parts are needed: sensors, thermostats, sequencers, even zones could be setup if there is sufficient water and/or airflow.  There are 2 moving parts: well pump and air fan.  The whole thing could be run on solar PV.

Next thing to consider is what to do with the 250 gallons per hour moving through the rig.  This is 6000 gallons/day if running wide open 24/7.  If 1 gallon of water can service a 4'x4' area of bed (double dug raised, hugelkulture, or even the equivalent area of containers), the capacity of the system would service 96000 sqft per day.  Man, tha'ts a lot of celery.  If the cultivated area is 50% of the total field, 4' beds with 4' paths, the field would be 4.4 acres.

This 6000 gallons is what comes out of the well.  Some is used for washing dishes, some for bathing, cooking, using the john, watering the chickens and pigs.  Also, the system does not need to run when its raining.  There are plenty of things that can be added, for example, holding tanks-let the water cool down or warm back up before heading to the field, as well as provide a buffer for use today and distribution tomorrow.

The technology required for this system exists and is readily available for reasonable (but surely not free) costs. 


Seed the Mind, Harvest Ideas.
Ken Peavey

Joined: Dec 21, 2009
Posts: 2523
Location: FL
If you had access to flowing surface water, a hydraulic ram pump could move the water without the need for electricity.  The water would be available in whatever volume needed, and unneeded water could be returned to the source.  This would be an ideal situation.  All you would need to do is run an air fan. 

A running stream with enough ram pumps should be able to provide all the cooling a home could need, and some pretty good heating of outbuildings in the cold season.

As a bonus, groundwater is not depleted.


Joined: May 26, 2010
Posts: 278
Location: Iowa, border of regions 5 and 6
First, you need to figure out some form of de-humidification.  RH at 80 to 90%?!!!

if you have a "radiator" system in your house with the cold water flowing through it, if the temperature of the water (and thus the radiator fins) is below the dew point, then water will condense.  This is good!  In order to keep mold and other nasty things from growing, you need to keep the humidity inside of your house between 30 and 50%.  If you can get the humidity down to 50%, then that 80 degrees might feel downright comfy.

I'm wondering if you could cannibalize an old window AC unit to get the radiator fins and tubing.  It should be a simple matter then to get the resulting condensate to drip/flow into a tube or a bucket.
Ken Peavey

Joined: Dec 21, 2009
Posts: 2523
Location: FL
Current home air conditioning units have an air handler inside the house which blows air through a radiator.  The radiator had cool refrigerant which cycles to an outdoor compressor unit.  The bottom of a standard indoor air handler is built with a plenum to catch and drain condensation.  This is then plumbed outside. 
Dehumidifaction should not be a problem.

I'm thinking cannibalizing an indoor and outdoor unit.  These would have refrigerant in the guts which would need addressed.  Used units can be had for cheap-I know an AC guy, he replaces old and busted units regularly.  A new unit could be ordered without refrigerant, perhaps for a surcharge, but this would be a purchase on the order of $5-8K.  These would come with everything.  Coils, valves, blower, standard duct outlets,  all the bells and whistles.

I'm no where near ready for this investment.  Solar PV is higher on the list.  Paying for this place is above that.

Looking at different potential parts may also be needed.  The AC/refrigerant systems operate with the refrigerant in gas and liquid.  Some of the plumbing gets pretty small in there.  Also, the water is kinda hard.  Running it through a new device designed for something else is not exactly the best idea.  Scale buildup can stop the thing dead, there goes my time, effort and hard earned money.  If I'm going to come up with a freaky simple idea, it really needs to work to keep me out of the lunatic fringe.

Auto/truck radiators are designed to handle water as the internal conductive fluid in conjunction with blown air.  Its the same sort of jig, coils with fins, and don't have environmentally incorrect refrigerant residues.  Antifreeze will rinse off real easy in my brothers driveway when he's at work.   Fittings can be fabricated fairly easily.  The things can handle the pressures and temperatures involved.  There are a couple of junkyards in town.  If need be, I could build the system with multiple radiators.  A drip pan is easy enough to build, even with a drain fitting. 

I'm thinking if I were to build an experimental model, the garage would be the place.  I can screw it up but good to get the details and bugs worked out before I put one in the house. 

My objective is to use the water which would already be flowing as a heat source/sink to heat/cool a space with no significant additional energy consumption.  Caveat: gotta use a fan.

What I need here is for you good people to rip the idea to shreds.

Jonathan 'yukkuri' Kame

Joined: May 23, 2010
Posts: 488
Location: Foothills north of L.A., zone 9ish mediterranean
If you are going to be pumping 6000 gallons a day, you might as well do some serious aquaculture. 

As for full florida sun, I figure everything except trees should be grown in partial shade - cattle included.  Something like moringa can be grown as an annual or pruned aggressively in late fall, letting in sun for winter, but then a good canopy will be in place by may to protect veggies that otherwise wouldn't survive the summer.

I like the auto radiator idea... fan is already there.  I guess those fans run on DC, which would be advantageous if you want to run an off-grid 12 volt DC photovoltaic system.  More efficient than using an inverter - though the range of applications is more limited. 

Heating the house, I think you will do far better with some of those hot air collectors made with soda cans.  Solar energy here is abundant - just need a cheap way to harvest it.  And it is actually fun to wear a sweater a few times a year. 

subject: Space Heating and Cooling with Home and Irrigation Water Usage