Waste Heat Recovery From Air Conditioners
If you live in one of the states now sweltering through heat waves; even more frequent sweltering days are in your future as a result of climate change.
But it’s not only your children’s children who will suffer heat waves more often. Your property values in these states will also sink over time as your neighborhoods heat up to unlivable levels over the next decades.
A/C will be a necessity. But adding a heat recovery system will at least cut those losses to your home values:
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Because it will save future owners half their energy costs.
Heating hot water can account 40% of your energy use. Your A/C unit makes excess heat in the process of cooling your home. Why use energy twice, if you can reuse it?
You can use your waste heat instead of the gas or electricity you now use to heat water, by putting an Enviro Pac waste heat recovery unit between the A/C and the water heater. These pick up the heat that your A/C generates as it it cools your home, and use it to heat water in your hot water tank.
Recovering ‘waste’ heat from an air conditioning unit would decrease its efficiency, make the unit under-perform when most needed and eventually require more energy to compensate for the losses than recovered.
This is another one of these greats ideas that recover energy by wasting more energy than recovered.
Same could be said for a refrigerator too, yet no one does it for the same reason Jean explained…
The water heater connection is available from some AC models now.
Problem is that it only works when the AC is on and in the heating mode the AC (heat pump) has to run additional time.
Better to just have solar hot water panels. I turned off the electric connection to the hot water tank on 1 April and will turn it on again in November. Zero power except for a very small recirc pump.
The thermodynamics support the claim of improving compressor efficiency. As long as the rate of heat removal to the 55-degree water is greater than the rate of heat removal to, say, the 90-degree air the AC was designed to dump to(which should be the case, given the relative temperatures and heat capacities of the air and water), the refrigerant will return just as cool if not cooler. It really does reclaim “waste” heat.
But I agree that solar hot water heating seems a lot simpler than intercepting the refrigerant on a central AC — and the units might also keep your roof cooler if mounted on the roof!
With regard to previous comments, first, when an A/C system has additional condenser coil surface added, the efficiency goes up not down (if the friction related pressure loss is low), secondly, refigerators do not have enough compressor horsepower to provide significant amounts of recoverable heat, thirdly there is a waste heat recovery unit that produces more hot water over a years period of time than a pumped heat recovery unit, that has no pump or electrical input whatsoever (go to http://www.olivetreeenergy.com , to see). Finally, the maintenance costs alone, make this system more cost efffective than solar (or pumped heat recovery).