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Forum Index : Other Stuff : Air cooler experiments
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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
I did a little experiment. Its hot here in summer, and I live off grid. Cooling during the day is easy enough, I can run the air conditioner for my office and the solar system is more than up to the job. But night time is a problem, the house is insulated, meaning it likes to keep the heat in at night and can take several hours to cool after the sun sets. I can open a few screen windows to let the air change, but these hot nights are usually still and full of tiny bugs that climb through the screen and make life miserable. Now I have a water bore near the house. The water temperature from the bore is 22c, all year, all day. I have a 24vdc pump, draws about 80 watts and the flow is like a garden hose half on, see picture.  Could I use this cool water to help cool the house? Time for a experiment. I have a radiator out of my Commodore that started leaking under the header tank gasket a couple of years ago.  Fitted a couple of 13mm hose fittings, then connected up a vacuum pump, and sucked it down. Applied some gutter silicon along the leaking edges, vacuum sucked it in, and let it cure, so I now have a water tight radiator.  Found a cardboard box.  Fitted a old 200mm bathroom extraction fan to blow air out, a thermometer in the air stream, and I was ready to test.  Warm day, just over 37c. Started the bore water and the fan, and after a minute the air leaving the box was 26c! Inlet water was 22.5c, outlet water was 28c.  Now this thing is drawing 100 watts, 80 for the bore pump and 20 for the extraction fan. I can run that all night easily. So I'm thinking I should make this properly, and put it on a stand inside the house. The outlet water is fed to my water tank or garden sprinklers, which I do at night in summer anyway. I dont know the flow of the fan, but its a nice breeze coming out of the box. I dont know if it would help cool the house at night a lot, but it should help, for very little energy cost. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| M Del Senior Member  Joined: 09/04/2012 Location: AustraliaPosts: 155 |
It will work fine at night, all the way down to 22.5c if your water is 22c. edit "if you are recirculating inside air" There are some who use covered over insulated inground pools or large buried water tanks in residential suburbs. For a captive water source however it needs to have some sort of spray cooling or the water will heat up to nearly ambient temp. In your case, you have the added bonus of winter heating up to 21c without changing a thing. Mark |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Thanks Mark I'll make up something a little more sturdy and set it up in the house to try it out. The only issue is running a couple of hoses through a window and keeping the bugs out, but if it works I'll mount a couple of fittings in the floor inside a cupboard. As I write this its 9pm, 31c inside the house and 29c outside, and a million bugs at the windows looking for ways to get in. Nasty. Regards Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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Dinosaur Guru  Joined: 12/08/2011 Location: AustraliaPosts: 311 |
Hi All Did something similar in the caravan, but to heat the van using the hot water from the Gas hot water service. Mounted the radiator under the bed, and is quite good in picking up the early morning temp by about 10 degrees in 30 minutes. If you are interested in the read: http://www.caravanersforum.com/viewtopic.php?f=2&t=27305 Regards Regards Hervey Bay Qld. |
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yahoo2 Guru Joined: 05/04/2011 Location: AustraliaPosts: 1166 |
It would be interesting to know how fast the heat transfers into your house. and if that changes due to daytime radiation. for example my house blocks the radiation from getting to the walls, windows and ceiling. So my temperature change is always the same when the temperature is higher outside. my temp change is 0.47 deg C per hour (unless it is a howling north wind). I done some work on a house of similar construction to yours this year. there were several problems that needed fixing. 1. roof insulation was getting heatsoaked and retaining heat for long periods 2. All the wall cavities were circulating hot air inside the walls from the outside due to dodgy top and bottom plates. 3. cracks between the floorboards were letting the cold air out of the house and drawing in hot air down the chimney and through some faulty vents. 4. Radiation was reflecting off the ground and hitting the walls and windows to fix it we designed a simpler cheaper version of the Houston cool roof This was the hardest, there was thinking and measuring involved. caulked and sealed the top and bottom wall plates fitted a 15mm poly foam insulation sheet and taped air barrier under the floor joists. Extended the roof overhang in some spots and used shade-cloth outside blinds in others. I am still waiting for some really hot days to measure how much difference it makes and find some spots we missed with the thermal camera. Before the upgrade two of those akai a/c units would run continuously and not keep the temperature down. Now one a/c runs about 12 minutes per hour to maintain 22-23 deg on a 35-38 deg day and down to about 5-7 minutes at night. I'm confused, no wait... maybe I'm not... |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Interesting setup Dinosaur. I run a electric blanket in winter here, it only draws 50 watts and is perfect for me. Yahoo yeah I would say my house has all those problems too. To get the place certified ( it was a removal ), I had to put insulation bats on top of the ceiling, and foil under the roofing iron as they re-fitted it. I also had to put insulation bats under the floor, but no foil. I was living in the place as I was working on it, and noticed fairly quickly it tended to keep the heat in after a hot day a lot more than pre-insulation days. The walls are not enclosed, open top and bottom. I have no way to access the tops, but can access the bottoms, so might look into closing them off. The walls contain no insulation, and they are old school fibro so I wont be disturbing them. The house is 96m2. I have lots of windows, but on a "bug night", I cant open them unless I turn all the lights off, the bugs craw straight through the bug screens and quickly make life miserable. This year I fitted shade cloth over the east and west facing windows. The cloth is attached under the eves at the gutter, about 400mm away from the windows. I dont have a whirly bird on the roof, would that help or just let in water during a storm? Be interested to see if your changes made a difference once summer hits. Last night I let the air-cond run till 9pm. Only my office is air conditioned, so after 6pm I opened the office door and placed a pedestal fan to blow the cool air into the lounge room. It took the edge off, but was still 28c at 9pm. The unit is rated at 2.5kW cooling, and I kept an eye on the battery bank. The battery voltage dropped to 48.8 at 9pm, under 800 to 1200 watts load. This morning it took a lot longer to boost charge, to be expected. If I were to build a house from scratch I would certainly put cooling and heating as a priority in the design. When I drive through the suburbs, I really notice the houses with dark fashionable roofs, small eve's, and high fences, and think it must cost them a fortune to just make the place livable. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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Tinker Guru Joined: 07/11/2007 Location: AustraliaPosts: 1904 |
But you have a newish looking whirlybird box for your radiator housing?  .My house is of similar size and construction as yours and it too has the roof insulation heat trapping problem. But its only a problem on the few days when the sea breeze does not blow strong here in Perth WA. For that reason I have left the eaves open as originally built so the breeze can clear the hot under roof air out. The whirly bird on the roof has never let water in, it tends to spin furiously when stormy and flings any water off it. These thing are quite durable, I'm on my second one now, the first lasted 10 years or so. Its the plastic bearings that eventually wear out and their racket at night is not helping one to fall asleep. I mounted the whirly bird at the second row of tiles down from the ridge so it catches the wind even if it blows from the other side of the roof. Klaus |
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| Boppa Guru Joined: 08/11/2016 Location: AustraliaPosts: 814 |
I got a friend who rents one of those, they have 3 aircon units and basicaly have to run1 all day (lounge/kitchen) and the other from dusk till dawn (master bedroom) they dont run the third anymore since the kids grew up and moved out, but they used to run it dusk to dawn as well They are happy their electric bill has dropped- to $1200 plus a quarter!!!! Scary... We got our last one here- down from $400 to $177, but looking at changing supplier, one has a $.20 feed tarriff, where we currently are only getting $0.07- I ran the figures and they would have actually owed us $30 if we had been with them...  |
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| Dinosaur Guru Joined: 12/08/2011 Location: AustraliaPosts: 311 |
Hi All I am impressed with the Temp stability of the houses here in Arkansas. The walls are plaster on the inside, then the timber frame, then particle board with plastic moisture sheet on the outside and then finally the brickwork.No vents in the brickwork. The roof is timber frame with plastic particle board, then plastic sheet and finally these Tar sheets looking like shingles.A whirly bird on the roof. However the roofs are steeper (12 ft from ceiling to ridge) Currently it is getting down to 2 or 3 C outside and inside it never gets below 20 C. More sustained lower temps outside will eventually mean I have to put the heater on, but by then I will be on my way back to Hervey Bay for the annual 6 week break. Well I think 2 amps at 12 vdc + gas is pretty good considering the diesel heaters some are using. And anyway you can't stay in bed all morning waiting for the van to heat up.(guess that depends who is bed with you )Regards Regards Hervey Bay Qld. |
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| yahoo2 Guru Joined: 05/04/2011 Location: AustraliaPosts: 1166 |
Using a whirlybird or venting the ridge can be great providing you control where the air is coming into the roof. if it creates a low pressure area that sucks air through cracks in the ceiling or comes in from one end swirling in a vortex across the hot iron then past the ceiling insulation on its way out then it can be worse. they work well with roof spaces that air can enter under the iron along the gutter or through soffit vents. This keeps the pressure positive and the air flow slow and controlled. I prefer a ridge-cap that is not fully sealed. I think the water cooler would work BUT if the aircon is not coping with its 2650 watts of cooling power, or whatever it is, I dont think the energy absorption of the water can match that. Off the top of my head you would be trying to remove 9500 kj per hour to match the A/C, that seems like a lot of heat getting in for a compact house. that is a lot more heat that a fridge and computer running, body heat and the odd cuppa. With no wind putting air pressure on the outside surfaces the only thing I can think is that the house is maybe leaking and drawing quite a lot. I'm confused, no wait... maybe I'm not... |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Yeah I wondered if anyone noticed that. I put that whirlybird on the shed last week, I think its helping a little. The shed houses my solar controller and inverter, and it goes over 50c in there on hot days. When its really hot I open the roller doors away from the sun and set up a pedistal fan to blow air over the inverter/controller, that keeps it under 45c. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
We have a house style here called "Queenslander", basically a big roof, wide veranda's, house in the middle, and the whole thing up on posts to let air pass underneath. It worked well in the summer before air conditioning became available. But with air conditioning, we needed insulation to keep the power costs down, and I think thats half the problem. My place was definitely cooler in summer before I insulated it, but I had to fit the insulation to get the house certified. I also find in winter the house stays cold when its nice and warm outside. I think you either need a lot of insulation, or none. My place is somewhere in the middle, and its just not working very well. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Yahoo yeah my roof space has the air gaps under the iron at the gutters and the ridge caps. My ceiling is sealed reasonable well, lots of no more gaps and everything was repainted. I could seal up some light fittings though to help. So a whirly bird could help, but what effect would it have in Winter? Should I get something I can close in winter to keep the heat in. The water cooler was able to cool the area around it, but not much more. It would be ok to cool a bedroom. I think your comment about saturated insulation in the roof has merit. After I turned off the water cooler and air conditioner after 9pm, the temperature in the house started to rise again! Today its only 13c outside, and windy, a bit of a change from 36c yesterday. In side the house it still 20c, heat from yesterday. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| yahoo2 Guru Joined: 05/04/2011 Location: AustraliaPosts: 1166 |
I will try and find my camera and take a photo of some of the stuff we used! I'm confused, no wait... maybe I'm not... |
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| Dinosaur Guru Joined: 12/08/2011 Location: AustraliaPosts: 311 |
Hi All I think the "modern" thermally efficient homes are "Active" not passive. Literally allowing air flow from different directions to achieve the desired temperature. With that in mind some of the whirly birds have louvres under them that can be temperature controlled or manually closed in winter. Why would you allow the heat to escape when it is so badly needed down below.? Don't know how you would draw the warmth from the roof down into the home without all the associated dust and smells. Regards Regards Hervey Bay Qld. |
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| yahoo2 Guru Joined: 05/04/2011 Location: AustraliaPosts: 1166 |
 its called kingspan aircell we had no room to install it under the timbers so we placed it on top, glued the bottom edge to the fascia, aluminum taped all the joins. Then we put a 18mm fairing strip on top to create an air gap under the iron for the air to flow to the pitch of the roof then out. its not perfect or by the book but it works. There is a second larger air-gap over the insulation. the house has vaulted ceilings so no roof space at all. There was no condensation in the insulation over winter, I thought we would have to install a small section/strip of vapour permeable membrane just under the pitch of the roof to let the water vapour out. I'm confused, no wait... maybe I'm not... |
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| M Del Senior Member Joined: 09/04/2012 Location: AustraliaPosts: 155 |
To actively ventilate your roof space you can use a car fan, solar panel, temp sensor and timer/switch. Or any fan linked into your house wiring. Your roof is tin if I have read correctly, do you have any gables? If so, set the fan as high up in gable as the frame allows and fit a weighted flap in a tube to seal it when the fan is not in use. Think draft stopper https://ecomasterstore.com.au/products/draftstoppa?utm_source=Click&utm_medium=Channel&utm_campaign=Google_AU&ref=SFDR_2 15392623&variant=808829707&ptcid=18048_389_267160622&gclid=EAIaIQobChMIuMme1q7Y3gIVhRuPCh2tDAKGEAQYBCABEgJGgfD_BwE Vents under the eaves can be fitted to allow sufficient air flow. If no gables, then a wirly bird with an active fan under it close to the peak will do the same. I have a tiled rof with no sarking, the wirly bird alone cooled the roof space by at least 10-20c, adding the fan dropped my roof space temp by 20c extra. Room ceilings now rarely hit above 40c against the 70-80c plus before fitting. note to self, add more insulation to R4.5 Mark |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
I've fitted a wirly bird to the house roof. I noticed late yesterday afternoon when it was perfectly calm, the wirly bird was still spinning, so I guess than means the heat in the roof space is escaping. Today its predicted to reach 40c, so after dark I'll venture into the ceiling space with a thermometer and see if its cooling. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| Tinker Guru Joined: 07/11/2007 Location: AustraliaPosts: 1904 |
The whirly bird on my roof always seems to be spinning, I can't recall seeing it stationary during the many years the thing has been up there. It might be still hot up there under your roof for a while, on a 40 degree day. At my place the old concrete roof tiles and the ceiling insulation batts trap the heat. I had an old radial fan which I mounted right under the whirly bird to extract more ail. Its connected to a N/O thermostat switch that closes at 40 degrees. So far it has not been hot enough here to trip it but for tomorrow they forecast 36 degrees so I might get a chance to see if this makes a difference. Klaus |
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| Boppa Guru Joined: 08/11/2016 Location: AustraliaPosts: 814 |
We got two on the roof, and yeah, on a perfectly still day they are both spinning if its hot I found it interesting we use the aircon now a lot more since we got the solar on hot days, and if is a lot more effective in cooling the house if we leave the kitchen and bathroom vent fans on as well, it cools the house a lot faster and allows the lounge mounted aircon to cool right down into the bedrooms, while leaving them off means the bedrooms stay noticeably hotter (the lounge is at one end, with the aircon on the furthest end from the bedrooms which are literally at the other end of the house) I assume that they are extracting the hotter air and pulling it with cooler air I know that aircon is supposed to be most efficient with a sealed house, but in practice, those extractor fans seem to make a big difference |
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