Using swimming pool as water source for heat pump AC?

[treepog]

Ok so this may be a VERY silly question but I do not know the answer so please bare with me.

I had a conversation the other day with a friend. He said it was possible to use the water in an in-ground swimming pool as a water source for a heat pump air conditioner? is this in fact possible?

I am sorry if this is a off the wall question but I'd really like to know.

Thanks in advance for any replies

[beenthere]

Moved to geo forum

[treepog]

Sorry about that, I realized I posted it in the wrong section after I had posted. Thanks


Moved to geo forum

[bwalley]

Ok so this may be a VERY silly question but I do not know the answer so please bare with me.

I had a conversation the other day with a friend. He said it was possible to use the water in an in-ground swimming pool as a water source for a heat pump air conditioner? is this in fact possible?

I am sorry if this is a off the wall question but I'd really like to know.

Thanks in advance for any replies

The pool will not have enough capacity, you will overheat the pool, by law a spa or pool can only be 104 degree's F max.

[Vinpadalino]

Try a septic tank lol.:patriot:

[fxb80]

Went to a house once where the owner had avoided the considerable trouble and expense of drilling a well (couldn't do a ground loop) for his water source heat pump by using the swimming pool. . It was during the winter and the heat pump wasn't heating well. The swimming pool was a sheet of ice. After my "Here's your problem!" he insisted that it couldn't be the problem because there was still water in the pool. Out of curiosity I chipped through a couple inches of ice, found water, and of course it measured 32F. I suggested he contact the manufacturer and ask them how much heat the unit would produce using 32F water as a heat source. He got the expected response from them and ended up paying us to install 20KW of electric backup heat. He later paid us to install an air-to-air heat pump, after a winter of high electric bills.

[deux]

In a warmer climate, with solar pool heaters........ You might have hit a niche market here Buck O ......... think about it. You have to be able to switch over to another source.... maybe.

[ACFIXR]

Currently being done by a contractor in phoenix. I am not privy to details but it is a big hit and performs well according to their installers that I have talked to. Here it is

http://www.dialcomfort.com/blu-eq-geothermal-heating-cooling-system/

[treepog]

Thanks for the responses.

Is there a way to calculate how much water would be needed per hour of running the AC? The reason this topic came up for me is that I am looking for an inexpensive way to occasionally cool my shed/workshop not my home. I have a 30'x30' with 8' ceiling workshop at my home and I only use the workshop a couple hours at a time on the weekends.

Is there a way to calculate how much water you need? Or is it such a huge amount that it would heat a 15''x30' pool to over 100 degrees in two hours?? Just trying to get an idea exactly how ridiculous this idea is I guess :)

[treepog]

Wasn't able to edit that last post...it's a 15' x 30' in ground pool.

[beenthere]

Currently being done by a contractor in phoenix. I am not privy to details but it is a big hit and performs well according to their installers that I have talked to. Here it is

http://www.dialcomfort.com/blu-eq-geothermal-heating-cooling-system/


How many years have they been installing them?

[ACFIXR]

dont know but these guys get bug eyed and start drooling when talking about these systems. My take is that thay are a combination type set-up say pool and chiller and an aerator.

[CoolQuest]

Ok so this may be a VERY silly question but I do not know the answer so please bare with me.

I had a conversation the other day with a friend. He said it was possible to use the water in an in-ground swimming pool as a water source for a heat pump air conditioner? is this in fact possible?

I am sorry if this is a off the wall question but I'd really like to know.

Thanks in advance for any replies

__________________________________________________ ______________________

Hmm very interesting. If this person installed a long enough loop between the unit and the pool it might work. Lets say he installed an underground loop long enough to do the job but only used the pool for the water source and not for heat exchange. He would need 2 loops. 1 before the pool in the series so the ground would do the heat exchange without changing the temp of the pool. The 2nd would be after the pool in the series so the water temp could reach ground temp before entering the heat pump. With a couple of tweaks that might work.

[teeball57]

My take is that they are a combination type set-up say pool and chiller and an aerator.

Pretty much right there. No chiller but need heat xchanger so you don't run pool water through GEO unit. The heating is done with separate ground xchanger or loop if you will.

[watercop]

Depends on loads, climate, ground temp, etc. Also must consider aggressive corrosion by pool water.

I'm not saying it can't be done, in fact its on my to-do list of things to try some day, but it isn't necessarily a slam-dunk

[bwalley]

Depends on loads, climate, ground temp, etc. Also must consider aggressive corrosion by pool water.

I'm not saying it can't be done, in fact its on my to-do list of things to try some day, but it isn't necessarily a slam-dunk

In Florida I can put a heat pump on a pool, run it for 24-48 hours on a 15 x 30pool, and it will be 104 degree's, that is a 3 1/2 ton heat pump, the guys at the pool supply house call them 3 /12 HP heat pumps though.

On pools we figure the heat gan/loss by the total surface area, it doesn't matter how deep it is.

So if you have a house with a 3 1/2 ton heat pump and run it using the water in the pool to cool the condenser, after a few days the pool will have reached the maximum temperature, then what are you going to do?

Pools do not have enough capacity, otherwise they would have already been using them.

[kdocsr05]

I agree with all the post regarding pool water capacity, just not there.

How about the chemical treatments used in a swimming pool? Standard heat pump equipment would not tolerate the chemicals in the pool water.

[bwalley]

I agree with all the post regarding pool water capacity, just not there.

How about the chemical treatments used in a swimming pool? Standard heat pump equipment would not tolerate the chemicals in the pool water.

It would have to use an heat exchanger, the pool heat pumps I sell and install have either a titanium heat exchanger or a coated exchanger, I prefer the titanium heat exchangers.

If pool chemistry is properly maintained (which they seldom are) it is not a concern though.

[teeball57]

They use an aerator to "cool the pool".

[bwalley]

They use an aerator to "cool the pool".

How much heat can you dump aerating a pool?

This as well as the increased heat will cause water loss and increased chemical cost, not to mention making the pool too hot to use.

[teeball57]

You will have to talk to Shasta Pools about that. Their idea, not mine.

[Joe Harper]

I think with the heating load in Miami, there wouldnt be much of a problem..

[JWB]

I have to admit I have laughed when I am working on an air to air and the swimmming pool pump is roaring away next to it in the spring. House wants ac and the pool wants heat.

[ACFIXR]

I have to admit I have laughed when I am working on an air to air and the swimmming pool pump is roaring away next to it in the spring. House wants ac and the pool wants heat.

Thats funny!

[Carnak]

In Florida I can put a heat pump on a pool, run it for 24-48 hours on a 15 x 30pool, and it will be 104 degree's, that is a 3 1/2 ton heat pump, the guys at the pool supply house call them 3 /12 HP heat pumps though.

On pools we figure the heat gan/loss by the total surface area, it doesn't matter how deep it is.

So if you have a house with a 3 1/2 ton heat pump and run it using the water in the pool to cool the condenser, after a few days the pool will have reached the maximum temperature, then what are you going to do?

Pools do not have enough capacity, otherwise they would have already been using them.the reason for the surface area is because the biggest heat loss from a pool is evaporation. I think the pool would have to be covered to hit the 104 myself

[Carnak]

How much heat can you dump aerating a pool?

This as well as the increased heat will cause water loss and increased chemical cost, not to mention making the pool too hot to use.architects get creative sometimes and put a fountain in a pond to mimic a cooling tower

[Heatranger]

the reason for the surface area is because the biggest heat loss from a pool is evaporation. I think the pool would have to be covered to hit the 104 myself
Anything will soon reach a point where it can not absorb more than phisically possible. That is why the excess must be dumped.
As for too much heat it is best to let it be absorbed back into the biggest heat sink in the universe. And that would be the UNIVERSE. "Nocturnal Radiation" is a passive method. It let's the black night sky cool the water. As with any heat exchange the more surface area exposed to the night sky the better. Then you add evaporation techniques. Coupled with venturi methods.
Smart building is the first step. Making stupid buildings livable is much more difficult than designing a smart building to begin with!

[Carnak]

1000 btu/lb as it evaporates,pretty hard to top that, 1 btu/lb as it heats up.

Agree on smart building is the first step, except I would call it "not a stupid building"

[Heatranger]

Went to a house once where the owner had avoided the considerable trouble and expense of drilling a well (couldn't do a ground loop) for his water source heat pump by using the swimming pool. . It was during the winter and the heat pump wasn't heating well. The swimming pool was a sheet of ice. After my "Here's your problem!" he insisted that it couldn't be the problem because there was still water in the pool. Out of curiosity I chipped through a couple inches of ice, found water, and of course it measured 32F. I suggested he contact the manufacturer and ask them how much heat the unit would produce using 32F water as a heat source. He got the expected response from them and ended up paying us to install 20KW of electric backup heat. He later paid us to install an air-to-air heat pump, after a winter of high electric bills.
I don't know where this pool was located but I would guess a solar cover coupled with a low watt pump/heat exchanger would have made a big difference in that water. And some of the heated air generated in the bubble thru the day could have been pumped to his air/air heat pump.

[Heatranger]

1000 btu/lb as it evaporates,pretty hard to top that, 1 btu/lb as it heats up.

Agree on smart building is the first step, except I would call it "not a stupid building"
Evaporation is hard to beat. I just think that the less water that has to be replaced the more stable and less maintenance is required.
Here in central NC we have a few real cold and a few real hot days. Therefore we try to focus on the normal "very cool" and "very warm, humid" days.
We flip the swith just like everyone else when it comes to the extremes. But saving energy dollars day in and day out requires a system that only needs to knock off a few degrees one way or the other.
I am working on a project involving an abandoned pool that I want to bury a coil into and top the pool area with a greenhouse/shadehouse.
This will allow me to collect heat in the winter and coolth in the summer.
I will "wrap" a coil beehive around a traditional heat pump and it will work with the tempered air.
What do you think?

[beenthere]

I am working on a project involving an abandoned pool that I want to bury a coil into and top the pool area with a greenhouse/shadehouse.
This will allow me to collect heat in the winter and coolth in the summer.
I will "wrap" a coil beehive around a traditional heat pump and it will work with the tempered air.
What do you think?

Won't get enough heat transfer from the beehive coil.

Probably freeze the water in the beehive coil in winter.

[Heatranger]

It won't have 'water' in it. It will be well protected from freezing by having an additive. This anti-freeze will increase it's ability to absorb heat and resist freezing. Constant circulation will make it act just like atmospheric air. Changing constantly to provide move btu differential.
What do you think?

[beenthere]

Antifreeze generally decreases BTU output.

Condenser coils are finned to get a 15 to 20° delta across them.

Can't see how just a beehive coil of copper that is letting 750 to 1250 CFM(if it doesn't let enough air go through you have no performance increase, and may decrease it) per ton of the heat pump go through it is going to have enough heat transfer ability.

[ACFIXR]

Anything will soon reach a point where it can not absorb more than phisically possible. That is why the excess must be dumped.
As for too much heat it is best to let it be absorbed back into the biggest heat sink in the universe. And that would be the UNIVERSE. "Nocturnal Radiation" is a passive method. It let's the black night sky cool the water. As with any heat exchange the more surface area exposed to the night sky the better. Then you add evaporation techniques. Coupled with venturi methods.
Smart building is the first step. Making stupid buildings livable is much more difficult than designing a smart building to begin with!


What a statement!

[drsmith012]

Try a septic tank lol.:patriot:

Been done (http://www.regjeringen.no/en/sub/framtidensbyer/the-participating-cities-/oslo/heat-from-oslo-sewer.html?id=548202)


Being done (http://greenlineblog.com/2007/12/2010-olympic-village-using-sewage-heat-recovery/)

[larobj63]

To the OP:

It is entirely possible to reject heat from a living space into a pool. I would strongly advise using a heat exchanger - do not run pool water through teh source side of a heat pump directly.

If you didn't use the space that often, you would likely be fine with the pool as a heat sink, capacity wise. That being said, the cost of the system would be quite a bit more (3x ?) than a traditional split DX system, that would only cost marginally more to operate. In other words - no payback here...

[tedkidd]

Been done (http://www.regjeringen.no/en/sub/framtidensbyer/the-participating-cities-/oslo/heat-from-oslo-sewer.html?id=548202)


Being done (http://greenlineblog.com/2007/12/2010-olympic-village-using-sewage-heat-recovery/)

COOL!

WRT pools. Wouldn't a lot depend on climate and ground temp?

WRT Payback. What solution for $3000 pool heating bill? I'm thinking this would probably be a separate part tied to dx or geo via plate xchng.

[GoofBall]

I want to do this. As someone else pointed out above, it is slightly ridiculous to have a 3 ton heat pump roaring away, 2 feet from an also-roaring 100,000BTU natural-gas-fired pool heater.

The benefits would be:
- The condensor fan could be turned off - would save about 1HP of electricity, which is not insignificant $$$;
- No burning of natural gas at all. Also $$$$
- alot quieter (the only thing making noise would be the pool's waterpump, and the refrigerant pump, wherever that is).


My plan is to splice in a heat exchanger just before the heatpump's condensor coils.

I have a liquid-liquid copper heat exchanger good for 300psi. R410 (or whatever) passes through one side of the exchanger, and poolwater through the other. There is obviously no mixing of the two fluids.

I want to leave the existing condensor coils intact, in case I decide to turn off the pool pump. This just means the R410 travels though an extra couple of feet of pipe before getting to the coils - I can't see this being a problem.


Overheating the pool: We're in a northern climate; I absolutely cannot see this happening, especially if the pool cover is left off overnight. In fact, I'll probably leave the gas-fired plumbed in, just in case.

Can anyone else see any other potential problems?
Any good hints on how to splice in the heat exchanger? I think this would involve recovering/draining all the refrigerant, soldering in the exchanger, and refilling.

[dbooksta]

Overheating the pool: We're in a northern climate; I absolutely cannot see this happening, especially if the pool cover is left off overnight. In fact, I'll probably leave the gas-fired plumbed in, just in case.

Exactly: I'm also in the NE, where we generally have cool nights and no shortage of water, so if the pool ever did get too hot all I'd have to do is turn on an aerator or water feature to increase evaporation and dissipate the excess heat.

(Obviously this is only for spring through autumn use; wouldn't try to run the pool loop in the winter with a frozen pool as heat source.)

[motoguy128]

I'm pretty sure you don't want to mix copper with pool chemicals. I'd use a standard water source heatpump, but have a closed water loop to a stainless steel heat exchanger designed for pool water use. Make sure you get the pump sized correctly for the required flow rate on the heat pump.

The only problem is that water temps will get into the 80's in the summer on the pool. Your effciency and capacity will be reduced a little by late summer.

The energy required to operate the pool feature for added evaporative cooling will consume a fair amount of electricity.

[dbooksta]

The only problem is that water temps will get into the 80's in the summer on the pool. Your effciency and capacity will be reduced a little by late summer.

Let's assume it gets as bad as some have suggested: Isn't it still more efficient to heat exchange with 100F water than with 80F air?


The energy required to operate the pool feature for added evaporative cooling will consume a fair amount of electricity.

The "evaporative feature" can just be a redirect of the filter pump returns to spray water through the air instead of under the surface. Pools have to run that pump for hours a day regardless of how it discharges.

[GoofBall]

I'm pretty sure you don't want to mix copper with pool chemicals.
This is a fresh-water (not salt) pool. Yes, there will be green copper problems if the pH gets too low (acidic), but only if the pool is neglected and falls far from the proper pH range. Other than that, what is the issue? Does chlorine attack copper?



I'd use a standard water source heatpump, but have a closed water loop to a stainless steel heat exchanger designed for pool water use. Make sure you get the pump sized correctly for the required flow rate on the heat pump.
Alas, buying a new heatpump is not in the budget :(


The only problem is that water temps will get into the 80's in the summer on the pool. Your effciency and capacity will be reduced a little by late summer.
In the middle of the day the air temperature will often far exceed 90F, and heatpumps don't complain about that. So using 80F poolwater instead of 90F air will help the heatpump's COP, right at the time when the AC is on the most.



The energy required to operate the pool feature for added evaporative cooling will consume a fair amount of electricity.
Like I said, I'm pretty sure overheating the pool is not in the cards for my climate.
And like dbooksta says, the waterpump is gonna be running anyway; if aeration is needed, you can build a nice waterfall or something into your pool.

3 Tons of AC: produces about 13kW of heat output.
200,000BTU pool heater: produces about 58kW. (4.5x more).
Obviously neither the AC nor the pool heater will have 100% duty cycle.

[beenthere]

Let's assume it gets as bad as some have suggested: Isn't it still more efficient to heat exchange with 100F water than with 80F air?


No, its not.

[GoofBall]

Quote:
Let's assume it gets as bad as some have suggested: Isn't it still more efficient to heat exchange with 100F water than with 80F air?

No, its not.

Aye, the COP (efficiency) depends on the "lift" - the temperature difference between indoors and outdoors. If you want 75F indoors: 80F outdoors requires only 5R(Rankin) of lift. But 100F outdoors requires 25R of lift, with a corresponding drop in efficiency.

[Six]

Man what Geo guys wont do to find a water source.

No in ground, above ground pool, septic system, bird bath or muddy puddle is safe.

Sooner or later someone's going to run a stick of copper through it and yell " EFFECIENCY " !

I was thinking about the pool side of the experiment. We have a lot down here in Houston.

They can go south quick AND everyone is installing salt now anyway. What if you happens when you have to respray the thing ? Or just clean the bottom ?

[Juan Madera]

Add a desuperheater between the compressor and condenser on the gas side of an air-to-air HP or A/C, and let it dump heat into the pool when the circ pump is running. Nice in cooler climates, but in desert southwest may overheat the pool, so a way to bypass if high temps are reached might be a necessity.

[GoofBall]

Has anyone actually witnessed a residential pool-sourced A/C overheat an average 16x32x8' pool? I have no facts, but I just can't see it happening - too many square feet of dissipation area, and too few kW injected into the pool. Plus you guys in the hottest driest Arizona desert have the most evaporative cooling effect.

Maybe you guys are Olympic-Michael-Phelps-types and any pool over 68F is too bloody hot....

[GoofBall]

What if you happens when you have to respray the thing ? Or just clean the bottom ?

I assume your question is "what happens when you turn off the pool waterpump?"
In my proposal the original condensor is still installed and ready for action - just flick on the power switch to the condensor fan, and you're back to the original old-fashioned low-efficiency setup.

[GoofBall]

Add a desuperheater between the compressor and condenser on the gas side of an air-to-air HP or A/C, and let it dump heat into the pool when the circ pump is running.

Excuse my ignorance, can you explain a desuperheater? I googled, but all I found was a rudimentary/obvious setup for injecting cold water into a steam line.

[steveoo]

A pond or stream would work.

[motoguy128]

Chlorine and copper at the levels used in a pool do not mix. It will undergo slow corrosion... meaning those thin wall tubes won't last long.

[Juan Madera]

Excuse my ignorance, can you explain a desuperheater? I googled, but all I found was a rudimentary/obvious setup for injecting cold water into a steam line.

A desuperheater takes the hi temp, hi pressure gas directly from the compressor and uses the heat to (typically) heat domestic hot water in a commercial refrigeration rack system. As the water temp is generally 140F or more, the refrigerant does not condense, just lose superheat and increase the efficiency of the condenser. Win-win all the way round. In a pool application the refrigerant would condense and do so at a lower temp than an air side condenser. Might even have to worry about too low of a head pressure!

Grocery stores with a meat department tend to use a lot of hot water and this is essentially free heat from the refrigeration and A/C system, so you will generally see a desuperheater water tank there.

Nordyne was selling a system for residential installations a few years back that did the same thing on a smaller scale. Some of the GSHP manufacturers like Water Furnace offer this an an option as well.

Found a link for you at: http://www.energysavers.gov/your_home/water_heating/index.cfm/mytopic=12840

and the paragraph follows:

Homeowners primarily install geothermal heat pumps—which draw heat from the ground during the winter and from the indoor air during the summer—for heating and cooling their homes. For water heating, you can add a desuperheater to a geothermal heat pump system. A desuperheater is a small, auxiliary heat exchanger that uses superheated gases from the heat pump's compressor to heat water. This hot water then circulates through a pipe to the home's storage water heater tank.

Hope this helps!

[Six]

I assume your question is "what happens when you turn off the pool waterpump?"
In my proposal the original condensor is still installed and ready for action - just flick on the power switch to the condensor fan, and you're back to the original old-fashioned low-efficiency setup.

lol...you must work for or rep a geo company.

The addition of a condenser fan does not make a AC unit low effeciency. Plenty of high seer air source units that are far cheaper to install and much more practical in some parts of the Country.

It reminds me of the guys that push heat pumps in my neck of the woods when natuaral gas is practically given away.

[BigBlock]

Old post but I thought I'd put some numbers to the question....

Assume the hp is rejecting 3 tons of heat into a medium sized inground pool of 20,000 gallons.

Heat into pool 36,000 btu/hr
Specific heat of water 1 Btu/lbm-°F
Pool water volume 20,000 gal (167,000 lbs)

=167,000 lbs / (36,000 btu/hr / 1 Btu/lbm-°F)
=4.63 hrs/°F

So for about every 4.6 hrs of run time on the heat pump, the pool water temp would increase 1 degree.

This is assuming no other heat transfer to the air/ground/eveaporation/solar which there obviously will be. During the summer months I think it is safe to say that the pool temp would hit the 100F mark without much trouble after a couple of weeks. I live in upstate NY and even without the solar cover my inground pool maintains 80F+ during july and august (especially this summer). From a more practicle point of view, any pool warmer than 85 starts to feel like bathwater to me.

[waterpirate]

The whole concept is reffered to as a " geo battery " and all the math I have seen on operateing it, the pool/or burried tank is allways followed by how much btu replenishment of the battery in fresh water in and hot or cold water is needed opposed to hours of operation for the heat pump. The one that was built and works was a coil of copper pipe put into a tank that was fed continuously by a natural spring at a slow rate and then piped to waste in the nearby creek. It enjoys being a closed, open loop/ with continuous replenishment. I think the load was around 3 tons or so.
Eric

[motoguy128]

Old post but I thought I'd put some numbers to the question....

Assume the hp is rejecting 3 tons of heat into a medium sized inground pool of 20,000 gallons.

Heat into pool 36,000 btu/hr
Specific heat of water 1 Btu/lbm-°F
Pool water volume 20,000 gal (167,000 lbs)

=167,000 lbs / (36,000 btu/hr / 1 Btu/lbm-°F)
=4.63 hrs/°F

So for about every 4.6 hrs of run time on the heat pump, the pool water temp would increase 1 degree.

This is assuming no other heat transfer to the air/ground/eveaporation/solar which there obviously will be. During the summer months I think it is safe to say that the pool temp would hit the 100F mark without much trouble after a couple of weeks. I live in upstate NY and even without the solar cover my inground pool maintains 80F+ during july and august (especially this summer). From a more practicle point of view, any pool warmer than 85 starts to feel like bathwater to me.

But it won't evaporation is pretty significant and the warmer the water is, the higher the evaporation rate. Plus it will reject more heat into the ground as well. But yes, it would raise the pool temp. 5-7F wouldn't suprise me. I don't think that's enough heat to hold much over 90F. But it might make the pool less enjoyable mid-summer.

[Phrancis]

To OP - Not to over-simplify, but wouldn't it cheaper and simpler - if you are just trying to cool a relatively small space for a couple hours at a time - to install a small ductless AC or, heck, even window units? I'm not a tech but this whole pool setup seems like overkill!!

[Aqua Del Sol]

I built a system such as the one that is in question here and it is in its sixth year of operation. The WSHP is a Climate Master 5 ton that was designed/intended for geothermal application. The only water the WSHP has ever seen is the water from a 18x36x6 vinyl ig pool, location being Long Island,NY.

I am a professional pool builder by trade, not HVAC. The system works flawlessly and is part of a pool system that creates more energy than it consumes. ( No this is not over-unity nonsense), but relies on the fact that the pool is idle for 5 months of the year.

Should anyone need free advice on how to heat your pool for free, do not hesitate to contact me.

[terawatt]

Old post but I thought I'd put some numbers to the question....

Assume the hp is rejecting 3 tons of heat into a medium sized inground pool of 20,000 gallons.

Heat into pool 36,000 btu/hr
Specific heat of water 1 Btu/lbm-°F
Pool water volume 20,000 gal (167,000 lbs)

=167,000 lbs / (36,000 btu/hr / 1 Btu/lbm-°F)
=4.63 hrs/°F



Actually, a 36000 BTU unit will have to reject at least 15000BTU per ton or total 45000BTU/h for 3 tons including superheat etc. So in a 8 hour day of running AC you would get somewhere around 360,000BTU, which is equal to about 7 of the extra large solar water heating panels from somewhere like aquatherm. That's enough to maintain heat in most pools. There are some products on the market that heat pools with air conditioners, not sure if they work with heat pumps. Google hotspot pool heater to see an example.