h a l f b a k e r y
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Humans live in a ridiculously narrow temperature range. We abhor the hot, sweaty places, like tropical jungles and we abhor the frigid, breezy places, like polar ice caps. In fact, we routinely inhabit an area slightly greater than 4% of the earth's surface, after we take out snowfields, deserts, oceans,
lakes, rivers, steep mountains and jungles.
The bit we do inhabit we also change, by airconditioning and heating; by producing hot water for ourselves; creating artificial wind, blocking wind, etc.
The use of airconditioning is on a rapid rise, as we try to make ourselves more comfortable. We extract heat from the air, by extracting warm water vapour, venting waste heat into the atmosphere.
Meanwhile, on the other side of the house, we heat water, using fossil fuels, or electricity generated from fossil fuels, to heat water for ourselves.
The idea is simple: Use airconditioning to cool the air in our homes, then feed the waste heat to a heat pump, to heat water for ourselves, for bathing and cooking. Heatpumps vent cool air to the atmosphere, which can be used for cooling our homes.
There is no free energy, but I see little point in just throwing it away.
It may not be much but it has to help.
One example.
http://toad.net/~jsmeenen/recovery.html
I was offered a similar system with my solar heating panel. [Ling, Mar 11 2005]
Second example
http://www.gru.com/...es/heatrecovery.jsp
still a good idea though. [Basepair, Mar 11 2005]
along similar lines...
Pool_20Heat_20Sink
[RayfordSteele, Mar 15 2005]
Annotation:
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Thanks for the link, [Ling]. I have been looking into installing a heatpump and could not understand why this isn't readily available. |
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Seems like an excellent idea, especially since using the waste heat for something would actually make the air conditioner more efficient. For wall-mounted units, a small electrical water pump to dump condensate on the condensor coils would probably also improve efficiency. |
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Another thing that might improve efficiency would be to replace the "constriction point" with a piston motor which would reclaim some of the energy spent in the compressor. Since the energy reclaimed would be--prior to reclamation--worse than useless, such a piston motor would almost certainly improve efficiency. |
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No problem. In my case, I did not install the waste heat capture system, since I would only use the air conditioning on hot days, and that is when my solar heating system is working well.
The system, that was offered to me, was an intrinsic part of the air con condenser. |
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This would certainly work well in hot climate. You may need a secondary method of heat rejection for days when you don't use much hot water but do use air conditioning. |
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It seems to me that the most efficient setup would be to have a small hot and chilled water plant designed for homes. The chilled water loop would serve your refrigerator and air conditioning. The hot water loop would serve heating, domestic hot water, and potentially a pool or hot tub. The chilled water and hot water sources could then be located at the same place and work together. |
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This is all often done in commercial buildings - seems logical to scale this down to houses. |
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BC knows all about coolers. |
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I've just installed two fairly large reverse cycle aircons, in the same enclosed space as the heat pump units that we've installed for pool heating and domestic hot water. The electrician, the plumber and the aircon guy were very impressed at the efficiency of the concept. |
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Use the frigid outside air (when it's
around at least) to cool the
refrigerator, via insulated duct,
small fan and a thermostat to
know when to do it; A lot cheaper
than running the compressor to
cool the air you just spent so
much money heating up. No
harder to install than a clothes
dryer vent (assuming the fridge is
properly equipped at the factory) |
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small cold box inside a large warm
box: (fridge in a house) |
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tiny warm box inside a small cold
box inside a large warm box:
(butter warmer) |
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[UB] i really appreciate that you posted this idea. it has been in my mind for quite some time but i always thought it to be obvious enough (baked) not to post it. (+). |
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[oc], you'd lose a lot of cool air through that duct in the summer. Instead, use the chilled-water-plant concept and include a water-side economizer. This could just be a coil that goes outside. Water could be routed there when it's cold outside and the compressor could be turned off. |
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[UB], unfortunately this idea is widely known to exist. Heat recovery is now an increasingly popular concept. |
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I was consulting on a YMCA project in Aurora, Colorado, that was sharing facilities with the Front Range Hockey Association (Ice hockey). We used the waste heat from the ice making process to heat showers, and the pool. |
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By dumping heat to a water source, you are sometimes making your airconditioning more efficient. Heat pumps are often used in facilties that have a cooling & heating need for precisely this reason. |
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Heat recovery is widely known to exist, but home-sized systems are rare or non-existant. |
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Home sized systems may be rare, but they're becoming more common in the form of ground-loop heat pumps. |
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By running several hundred feet of tubing through the ground several feet down, you can tie into a very large thermal mass. By connecting any heatpump device (airconditioner, refrigerator, central heater, etc...) to the relatively constant temperature water in the groundloop, efficiency gains typically on the order of 25-40% can be achieved immediately. |
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Given the vast quantities of energy being consumed by users in developed countries, this would seem to be a no-brainer. To my knowledge there is no-one doing anything similar in this country. Australians are the world's 2nd-most profligate energy consumers. |
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[World], you wouldn't lose
anything if you had an insulated
baffle to shut the duct in the
summer. Could be the same valve
that opens to let in the cold air. |
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I still see issues (it's takes less energy to move water than air, bugs, wind), but not a bad idea. Post it as an idea, and we can discuss it further. |
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[world] - if it exists, but is rare, then that would make this idea baked, and more like advocacy - right? |
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[eg] Pretty much, though I'd disagree with the advocacy viewpoint. |
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a direct application of [UB's] idea can be preheating material from air conditioner's hot exhaust air before putting it in oven for cooking. this may not extend to microwave oven since it has timer based operation. |
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[+] I've always felt aircon to be a staggeringly wasteful system - admittedly it's not particularly necessary in the UK, which means I've never really been viscerally introduced to the benefits, either. |
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Connections for this sort of system should be standard on all aircon units. Now that you can get domestic-size CHP units, how long before we see this sort of thing? |
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It surely has to be coming. The aircon tech guys tell me that aircons are not optimised for working in conditions where the air is hot. They work harder. |
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That means that any heat we directed to the HP would then need to be recycled directly back to the HP, or vented. It shouldn't be dumped back into the space from which the AC draws air. |
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That should mean that the heat feed needs to be contained and directed from one to the other. |
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As [World] has stated, commercial designs often include such a heat recovery system (particularly to preheat 'domestic' hot water systems via heat rejection from Chilled Water generation (and anything else cooling wise that will generate/reject heat!)). There is an issue in the cost and size of an installation for domestic use depending on your heat exchanger (water to air, fridge gas to air etc). Having said that, the payback is not necessarily financial but also resourceful as the author implies. |
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