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Forum Index : Solar : Water heater improvement.
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Madness Guru  Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
There are panels that circulate water through the back. No doubt they are not cheap compared to new conventional panels and most of us on here are looking at cheap secondhand panels. To gain any additional efficiency from the PV you would also need to be running water through that is sufficiently cool enough to keep the temperature down near 25 degrees. However, a home could be built to take advantage of the extra heat via air circulation and in some climates that may be beneficial. I think a few extra panels and a reverse cycle AC would be a better option. There are only 10 types of people in the world: those who understand binary, and those who don't. |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
Can you trickle water over the top of the panel ? The darned things are supposed to be left out in the rain anyway. We would get some evaporative cooling as well as keep the panels much cleaner. The warm and rather dirty water could go through a heat exchanger. Cheers, Tony. |
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yahoo2 Guru Joined: 05/04/2011 Location: AustraliaPosts: 1166 |
I have found a guy that has done it. https://resystech.com/solar-heat-pump-system1.html edit: need a photo!  youtube DIY solar heat pump system he has gone even more hardcore and built his own panels.  I haven't quite followed all the ducting not sure if it can be ventilated in summer but the temperature differential is impressive.that is the problem I have, 55 days when I could run a heater and I have been not home for half of them pretty consistently for the last 30 years, it is very hard to justify this kind of complexity. Maybe I need a sauna for some bikram yoga!  I'm confused, no wait... maybe I'm not... |
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| George65 Guru Joined: 18/09/2017 Location: AustraliaPosts: 308 |
That's a pretty clever system. Only skimmed the page but I didn't see an explaination that heat pumps have a curve of efficenty and will only work down to a certain temp before they become useless. As I see snow in the pic, that's well below what a reverse cycle AC would heat at. Pulling air that was heated from behind the panels however would make that temp a lot warmer and get the AC where it could operate. It's a good soloution to the problem of getting the heat inside. You'd only want to operate it in winter though because in summer it would go the otehr way and feeding it hot air at the temps I imagine it would see would make it go the other way and it wouldn't cool for Jack. I just got up in the roof for a look around for the first time which was interesting. it wasn't nearly as warm up there as I expected despite it being a warm sunny day. there is sarking under the tin and batts on the ceiling. I replaced a lot of them as well. Someone had pulled whole areas between the battons out to get it away from the halogen lights. Having put in LED's now, I sat the transformer back on top and replaced the batts. Also the ducted AC has been an afterthought and where the ducts come through the ceiling, the whole baton area with those was uncovered as well. Put the batt back in around them so covered a lot of area there too. Might actually make a difference in here now. Maybe 10% or so of the ceiling are was uninsulated as it were. As for the air quality, I was coughing every 60 sec up there from the dust. Air smells Ok but the dust had me coughing the whole while from the time I got up till the time I got down. Haven't hacked once since I got out. I thought it would have been a lot warmer up there but at a guess i'd say 5-10o above ambient. I notice the roof does seem to have a ventilated effect. The insulation is just back from the ridge capping and you can see daylight clearly through the corrugations. Putting my hand up there, I can feel the draft of the air escaping. Probably not a bad thing all in all. Due to the pitch of the roof, there isn't much space to put a duct through the eaves. I was thinking of doing that to bring fresh outside air in when it was warm out or to push the hot air out in summer where there is a temp drop outside. Does not look easily feasible. I would give that solar panel box a crack along this back wall but there are a lot of floor to almost ceiling windows so again not practical. It does illustrate how many simple improvements could be made to houses that had some actual thought put into their energy efficiency and employed a few ideas for better heating and Cooling from the design rather than just add on stage. |
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| Phil23 Guru Joined: 27/03/2016 Location: AustraliaPosts: 1664 |
Quite a bit different to what I've done, that is detailed in the thread from 2 years back. The fan draws 105 Watts on high & displaces 840 cubic metres of air per hour. The main living area, plus adjoining Office/Spare bedroom have a total volume for 215m³, so air turnover is about 4 times per hour.  There's a few more pics in the original thread & it's evolved a bit more now with a better control board; 8 relay etc & now runs 2 fans & 3 damper valves. Phil. |
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| George65 Guru Joined: 18/09/2017 Location: AustraliaPosts: 308 |
You'd certainly pull some heat out of that roof space with the tin being uninsulated! I know how much heat my uninsulated Shed roof radiates when I'm standing on the floor and it's fully ventilated and covered in panels as well! Do you have any filtering of the air you pull from the roof? I'd like to have a filtered air supply Running into the house to try to pressurise it a bit to push the air out of windows and doors so the dusty air was not as easy to get in. Cleaned the return air Filters yesterday and was horrified at how dirty they had got in the 3 months since I did them last. No wonder the furniture is dusty in a week. |
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| Boppa Guru Joined: 08/11/2016 Location: AustraliaPosts: 814 |
It was relatively common for old queenslander houses to have shuttable vents up near the ceiling, and some had a floor vent as well, you opened both during summer and the floor vent (usually set well in towards the center of the house) would draw in the cooler air from under the house and vent the warmer air outset through the high vents. Worked surprisingly well I found, between those and the high ceilings, almost made aircon unnecessary (the wide allround verandas helped a lot too) One place I rented actually had a big (approx meter across) floorvent in a corner of the loungeroom that opened/shut with a slider, it also held the pole in the corner of the room you used to open the high roofvents, all done in brass... lovely piece of workmanship |
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| George65 Guru Joined: 18/09/2017 Location: AustraliaPosts: 308 |
There were a couple of pieces of floorboard Missing in my old house. Well, they kind of broke through when we moved some furniture. We did this in summer and I immediately noticed the cool air rushing up from under the house. I had a tube fan like in phils pic above I used to sit over the gap and pull the cool air up. My mate that did aircon came over one day and asked who put in the new AC and where was it the front half of the house was that cool. I improved it the next summer and got some of those Micro mist sprinklers for watering gardens and put them in a wide circle around the hole. They didn't use much water but the cooling effect was incredible. used that on real hot days and others ran without the water which dried the area under the house out anyway. People would ask when were we going to fix the floor properly and the answer was NEVER! I did get a couple of board to fill the hole in winter and we sealed it with a rug till the heat came again. Never heard of the vent holes before but I can sure believe how effective they would be! |
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| Phil23 Guru Joined: 27/03/2016 Location: AustraliaPosts: 1664 |
The filter is a 1200mm length of decorative perforated flue tube wrapped in Dacron type material, so static electricity comes into play. You can't quite see it in any of the pics as it is still on the Work-in-progress shelf, 20m away in the shed. |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
A filter would also keep out the assorted beasties. Anything from mosquito size to possum size could be a problem ! Cheers, Tony. |
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| George65 Guru Joined: 18/09/2017 Location: AustraliaPosts: 308 |
Been thinking a bit more about the heater and realised I completely missed the obvious. The soloution to making it more passively efficient is not to paint it or insulate it, it's to do both! What it needs is to be insulated in a box of something like coolroom panels. The tank and inside of the box needs to be painted black and the side facing the sun needs to be glass or polycarbonate to let the sun in and hold the no doubt considerable heat it trapped. Maybe I could plumb a heat exchanger in the spare top and bottom ports of the tank and add a thermostat that opened valves and operated a fan when the air temp exceeded the Water temp. Would certainly work for a pre heater tank feeding to the main one! Brother in law had a heap of coolroom panels I could have got about a year ago. Probably take me another 3 years to find any at the right price now. Always the way! |
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