Water Cooled Air Conditioners

[Gary A]

Many if not most of the commercial air conditioners are water cooled. I noticed these companies have a cooling tower on their roof and some times the water is steaming even when it is quite hot outside.

If water cooled home size units were available you could save money on your cooling and eliminate your hot water heater. You could size your water storage tanks to regulate the temperature. I don't like a HOT shower but I hate cold showers. What do you think?

[rishi]

Could one imagine some sort of steam engine added to the system - converting energy in the shape of heat to energy in the shape of electric power - thus reducing the powerbill even further?

[Crossy]

Could one imagine some sort of steam engine added to the system - converting energy in the shape of heat to energy in the shape of electric power - thus reducing the powerbill even further?

A Stirling engine would be more practical Obviously way too expensive otherwise someone would have already done it.

Meanwhile, back to the OP. I stayed at a resort in Malaysia where there was a notice in the room 'for hot water turn on the aircon', worked a treat. Evidently the kit you're looking for does exist, not seen it in Thailand though

[h90]

Could one imagine some sort of steam engine added to the system - converting energy in the shape of heat to energy in the shape of electric power - thus reducing the powerbill even further?

theoretic you can get back energy

after compressor the media is hot and you have a cooler surrounding so that difference in heat is a potential power source.

[stevehaigh]

Many if not most of the commercial air conditioners are water cooled. I noticed these companies have a cooling tower on their roof and some times the water is steaming even when it is quite hot outside.

If water cooled home size units were available you could save money on your cooling and eliminate your hot water heater. You could size your water storage tanks to regulate the temperature. I don't like a HOT shower but I hate cold showers. What do you think?

my local electrical shop has a system to heat water from AC. i guess they tap it into the freeon line.

[autonomous_unit]

theoretic you can get back energy

after compressor the media is hot and you have a cooler surrounding so that difference in heat is a potential power source.

Except that all you are doing is putting a parasitic load on your compressor which is busy trying to pump the heat out.

I'd suggest turning off the air-conditioner and swapping its power plug with that of the device you are trying to power, if you really want to tap into this potential power source.

[Crossy]

my local electrical shop has a system to heat water from AC. i guess they tap it into the freeon line.

Steve, I'm very interested in this type of unit. Any idea who make it, what it's called, how much it costs ???

Any and all information is welcomed with open arms

[h90]

theoretic you can get back energy

after compressor the media is hot and you have a cooler surrounding so that difference in heat is a potential power source.

Except that all you are doing is putting a parasitic load on your compressor which is busy trying to pump the heat out.

I'd suggest turning off the air-conditioner and swapping its power plug with that of the device you are trying to power, if you really want to tap into this potential power source.

no thats not true!

Think: we estimate after the compressor the gas has 70 degree. We make a closed steam engine with for example alcohol instead of water. Than this engine can generate some mechnical engergy from the heat, but is only doing the same as the fan would do (cooling/condensing the gas).

Where doyou see a parasitic load? Of course that example is very theoretic and it does not make sense to make it real.

[ando]

I don't know how the big water cooled aircons work, but I suspect you need a large commercial set up to make it economically viable for the extra hardware required.

On the subject of hot water though, there are many sites on the net that give detailed instructions on how to build your own solar powered hot water system. Could be fun building your own from scrap (and save a bit of cash too) if you have the time to spare.

I imagine it would be wise to run it thru one of those thermostatic wall mounted electrical water heaters as back up for rainy days.

PS.

I hate those early morning cold showers when upcountry too!

Edited July 4, 2006 by ando

[chownah]

A link to an internet broker that represents Guangzhou Hiseer Air Conditioning Co., Ltd. (mainland China):

http://hiseer.en.alibaba.com/

Once you are at their site do a Search for "Hot-Water Producing Air Conditioners" and the page for this company will appear....or maybe this link will take you straight there...not sure..(just tried it and it takes you right there). They make a few models that cool air and heat water.

I'm hoping someone comes up with some info on this as I'd like to learn more about the practicality of these systems.

For the do it yourselfers....I believe that when the refrigerant leaves the compressor it will be hot. Usually this hot fluid goes to am air heat exchanger which is typically a radiator with a fan. I believe that if this fluid is hot enough (I think it probably is) then if the fluid was to be directed first into a heat exchanger in a water tank (a coil in a water tank) and then to the typical radiator with fan...then you would get your hot water for free. It would require a larger amount of refrigerant...enough to fill the coil in the water tank and the tubing going to and from it. Another way would be to have a water coil wrapped around the tube carring the hot refrigerant from the compressor to the air heat exhanger....or some variant of this configuration.

One thing I'm not sure of is whether the fluid running between the compressor and the air heat exchanger is a gas or a liquid. If it is a gas, then removing heat from it will likely change it into a liquid and perhaps there is something in the design of an aircon unit that does not like the gas to be converted to a liquid in that location and only likes it to be changed to a liquid in the actual air heat exchange unit....I don't know about this but maybe you would need to design this so that when the refrigerant enters the water heat exchange unit it is a constant downslope all the way to the entrance of the air heat exchange unit so that the liquid can drain uninterrupted to the air heat exchange unit....I don't know about this.

I'm not expert in this but I'm reasonably certain that this is how its done.

Chownah

Edited July 4, 2006 by chownah

[Gary A]

Parasitic ? The more efficiently you can cool your air conditioner unit condenser the more efficiently it will run. All the heat going out of the condenser is lost. If you stand in front of the condenser you will feel all the heat that is extracted from your home or condo. Why throw away all that heat?

theoretic you can get back energy

after compressor the media is hot and you have a cooler surrounding so that difference in heat is a potential power source.

Except that all you are doing is putting a parasitic load on your compressor which is busy trying to pump the heat out.

I'd suggest turning off the air-conditioner and swapping its power plug with that of the device you are trying to power, if you really want to tap into this potential power source.

[autonomous_unit]

Your stirling engine, or whatever is trying to extract work from the air-conditioner, will only be acting as an insulator on the radiator! This will make the air-conditioner work harder to try to pump the heat out of the room, since it has to pump the heat through your engine.

Thinking in terms of a closed system, the only way to recover all of the compressor's work would be to dump the heat right back into the room (of course this requires idealized 100% efficient heat pumps and stirling engines). The only useful work being done is to put enough order into the system to move the heat outside the room, and you can see that order as a kind of potential energy accessible by reversing the heat flow.

The use of an air-conditioner to heat household water is not violating this principle, because it is not a closed system. You have to consider the cool water source and the hot water drain as all being part of the heat exchange. In practice, the compressor does less work because the cool water reduces the temperature required in the radiator... the water is often cooler than the air and also conducts heat so much better that a lower gradient is required. If you didn't have a cool water source and a need for hot water, this would cease to be effective. The water would get too hot and require higher and higher temperatures at the radiator to keep pumping heat from the refrigerant, again requiring more work from the compressor.

In a closed system such as originally mentioned in this thread, the water tank is not bringing a fresh supply of cool water, but only forming part of a larger heat-sink and radiator system. It has more specific heat than air, so can temporarily store or buffer the thermal energy during the peak load period. It also conducts well, so you can for example have a smaller radiator between the compressed coolant and the water system, and then much larger radiators between the water system and air. Also, some of these systems use evaporative cooling to help transfer heat from water to air, which gets us back to the household water heating model, where new cool water is entering and hot water is "draining".

[Crossy]

Of course, we could try the absorbtion type aircon (no compressor) and use solar power.

http://www.solarserver.de/solarmagazin/art...juni2002-e.html

Never seen a DOMESTIC unit though

[h90]

Your stirling engine, or whatever is trying to extract work from the air-conditioner, will only be acting as an insulator on the radiator! This will make the air-conditioner work harder to try to pump the heat out of the room, since it has to pump the heat through your engine.

Thinking in terms of a closed system,

no you thinking complete wrong here!

If you put an heat exchanger between compressor and radiator, you improve cooling. The pressures will be exactly the same/or a bit lower. The end temperature of the liquid will be a bit lower. So you even improve the situation for the compressor.

Think like it would be a small coal powerplant, but instead coal you use the heat of the compressor, instead of water you use alcohol (lower boiling temp). For the media alcohol it is a closed system but not for the heat as it needs a large condensor/heat exchanger to get rid of the heat and condense the alc steam again.

The compressor only cares about the two pressures (sucking side is not changed, and on the pressure side you have only an additional heat exchanger). So no parasitic load.

But of course that is only theoretic because it would be a hugh investment to get a few Watt back.

[Swelters]

If overall energy efficiency is what you are after, I'd think of several things before hybrid aircon water heating systems (which by the way I think are available, try the next Thai annual air con convention). My suggestions would be:

-reduce volume of air to be conditioned, ie small room or room-within-room.

-seal the room to prevent moisture infiltration. Most of the energy is spent condensing water not cooling air, which is what you want anyway, ie air at 40 percent rel hum instead of 70 percent so you can effectively use your own evaporative cooling system (perspiration). Cold air, ie 25 C or lower, isn't really all that great. Get used to say 28 C and 50 percent RH.

-shade walls exposed to sun, especially concrete walls which will bleed heat well into the evening, you will be solar heating walls uselessly, then paying to cool them at night. Insulation is a second choice.

-dont oversize the aircon unit and then run it on "energy saving mode." It will cycle on and off and do a bad job of dehumidfying and deliver air that is too cold for comfort. 9000 btu/hr units should be fine for small rooms. A "heat pipe" addon to you aircon which precools and reheats conditioned air may be beneficial.

Swelters

[otherstuff1957]

The efficiency of cooling towers is directly related to the ambient humidity. In Thailand the average humidity varies from about 70% to 90% - so evaportive systems don't work very well here. :-(

Also, evaporative systems, by definition, lose water with every cycle. Unless you have a source of free or very cheap water, you might wind up spending the money you save on electricity on the extra water that you are using.

Ammonia cycle refrigeration was fairly common 80 years ago, but the standard compression style refrigerator is much more efficient so it has become the standard.

I like the idea of using the waste heat from your AC to heat water! I don't see how it would effect the efficiency of your AC at all, unless it actually improved it by cooling the refrigerant more quickly.

Some people have made combination evaporative/compression AC units by adding a panal of some moist absorbant material in front of the intake side of their standard AC unit. They add water to some sort of drip system in the panel whenever the AC is running and the evaportive action cools the air going into the system and improves the efficiency of the unit.

[edd]

I think that this is the answer to your question.

Copy and paste

http://www.energystar.gov/ia/partners/bldr...lderGuide3E.pdf