I have a north facing chimney 6m high by 1.2m wide and want to make a solar air heater about 4m x 1.2m to mount on the face of the chimney. Air would be drawn from floor level inside, passed through the panel and returned via a standard central heating duct and register. I'm considering Trimdeck roofing with the crest riveted together to form airways about 180mm x 60mm as the absorber panel, insulated behind and covered with either Laserlite or some other light weight glazing material.
Does anyone have any experience or suggestions.
Derek
Solar air heater
(17 posts) (12 voices)-
derek ryan
MemberPosted Wednesday 18 May 2011 @ 1:50:57 pm from IP # -
ghostgum
MemberSee http://builditsolar.com/ for some ideas.
I've not built one, but I have a similar idea. I'm not sure if Laserlight is the correct solution. The stagnation temperatures in summer may be too hot. If polycarbonate is Ok, then another idea is double walled polycarbonate. Otherwise it will have to be glass.
You may need a butterfly damper to prevent your central heating system from blowing air into the solar air heater.
Posted Wednesday 18 May 2011 @ 9:31:40 pm from IP # -
Ueee
MemberIf i understand correctly your collector will be vertical? if its facing true north or somewhere close you can install an awning in colourbond etc (size dependant on your latitude) so that sun only falls on the collector in winter and morning/arvo in summer so the collector won't cook in midday summer sun. Make sure you use a high temp insulation, my experimentation with hot water collectors shows collector temps can reach 70-80 deg easily even with ambient temps around 10deg (in Canberra). A Multiwall polycarbonate will make a big difference on cold windy but sunny days as it will minimalise heat lose but can get expensive-8mm thick costs me about $50 a square meter.
Good luck!
Posted Thursday 19 May 2011 @ 10:52:34 am from IP # -
On one of the Sustainable House days I saw a house where the fellow had a box around the back of his PV panels and he fanned the air down into the house. Once the season turned he opened some panels so the Solar PV did not overheat.
The point I suppose is the air in the house on a winter morning once the sun is up may be cooler than that outside. Why heat that and return it when you can just heat the outside air and pump it into the house.
Just a different way of looking at it, but quite dependent on local conditions. Good work developing new ideas though.
Posted Saturday 21 May 2011 @ 9:32:37 am from IP # -
I am just building a solar collector with integrated heat storage for space heating. Phase change material will be stored inside evacuated glass tube collectors to store the heat collected during the day. As required, air will be blown over the top of the heat pipes during the night to warm up and heat my living room.
Posted Saturday 21 May 2011 @ 11:06:51 am from IP # -
Jeffbloggs
MemberS2S
Interesting, tell me more. What phase change material are you using and how much thermal mass can you fit into a ET in Watt hours? How do you blow air over the ET to extract heat from the stored thermal mass? How did you configure it to make to work? Sounds like a interesting concept if it can be kept compact enough.Posted Saturday 21 May 2011 @ 12:07:25 pm from IP # -
I use Erythritol with a melting point of about 120C.
The heat capacity per tube is equivalent to about 0.2kWh. This means I will need two 30 tube modules to achieve 12kWh heating capacity.
I extract the heat from the top of the heat pipe which will be covered with aluminium fins.
Temperature control by blending hot and ambient air.
Patent pending. I filed the application about 3 weeks ago.So far I have only modified a few tubes.
I should be building the full module in about 3 weeks and will show the progress on my web page.Posted Saturday 21 May 2011 @ 1:34:48 pm from IP # -
Jeffbloggs
MemberS2S sounds cool. I have some more questions if I may:
How did you get the Erythritol into the ET, how is it centered/contained? Or can you buy the tubes like that? What is the thermal capacity of Erythritol ie in comparison to water? Do you have a specification link otherwise? Do you use the ET as an "insulator" as such for your thermal mass store? Or is this thermal mass store external of the ET at the end of the heat tube, and between the alu fins?
Lastly do you expect to sell them, if so how much? I might have a few customers
Posted Saturday 21 May 2011 @ 5:00:03 pm from IP # -
Johnnojack
MemberDerek is the chimney no longer used? You said air will be returned using a duct, so I presume that will be inside the chimney rather than dangling down the side. Also why not use the chimney itself as the absorber? Then the bricks warm up and hold the heat to be used later. Sealing to the chimney would need to be good. To avoid over heating in summer you could make a small vent at the top which could be operated from the ground by a cable or rod. You could then use it in summer to ventilate the house. Would need another vent into the chimney at ceiling height, that could be a bit of a challenge. Sounds like a good project.
Posted Sunday 22 May 2011 @ 5:46:38 am from IP # -
derek ryan
MemberJohnnojack, The ducts will be purpose built for the panel only, with a cross-sctional area of about .004 sqm (200x200mm). This matches the area of the flow path through the panel. I think Ghostgum and Ueee are on the right track with their suggestion of double skin polycarbonate as I intend to have a double pass flow,ie. the incoming air will rise between the glazing and the metal to be preheated before entering the airways at the top (within the Trimdeck absorber panel) where it is drawn down by the suction from a fan within the return air duct. Without a double skin polycarbonate the heat losses through the glazing may be excessive. Being on a vertical north facing wall in winter gives excellent solar exposure while in summer the exposure is minimal and easily shaded. I will need a differential thermostat to control the fan, similar to the systems used in split solar water heaters.
Posted Tuesday 24 May 2011 @ 12:54:40 pm from IP # -
For solar heater or solar roof fans i would like to recomend that west lake solar . it is a real proforssional manufacture ! their solar heater was originally desinged and completed in Europe . a very mature product !
Posted Wednesday 25 May 2011 @ 6:55:36 am from IP # -
Benny
MemberI don't think you need to bother with a differential controller Derek. I just use a simple LCD display /electronic thermostat in mine and just use a set temp of about 30deg. I figured its only worth turning on the fans if the temp in the collector is up to 30C before fans come on. I use this one from Jaycar http://www.jaycar.com.au/productView.asp?ID=QT7200&keywords=thermostat&form=KEYWORD It was $40 but now about $48. You need to remove the thermistor temp sensor from the internal circuit board and extend it on wires up in to the collector, but that works fine just with a twisted pair from CAT8 cable.
The beauty of this one is that the contacts can drive 240V direct and it runs on 2 x AAA batteries. Sadly it doesn't work with re-chargeables though.Posted Wednesday 25 May 2011 @ 9:17:41 am from IP # -
mladen
MemberThere is interesting user manual on building solar air heater : http://solar.freeonplate.com/solar_panel_DIY.htm
for this amount of money you can get plenty of heat even if you don't build unit for heat storage. Great idea. Just go on...
Posted Monday 18 Jul 2011 @ 12:08:54 pm from IP # -
mladen
MemberYou are right about more work is needed, but:
1. cans are extra thin, so absorbing and emission of heat is quicker
2. cans are made of aluminum, which has great heat capacity, better than other metals
3. you are collecting heat on top side of cans (sun facing), but heat is distributed on whole wall of can, so air flowing through it, has much bigger surface to collect more heat.
4. when drilling/cutting bottoms and tops of cans you are making barriers which make air go in more turbulent manner, so it can spend more time hitting against can walls and collect more heat. In single row, you have 15-16 barriers just to allow air to collect more heat.
5. it is more fun if you have to drink 200 beers and "actively" participate in this project and recycle aluminum cans.best regards,
Posted Monday 18 Jul 2011 @ 1:56:33 pm from IP # -
For heating water in homes through electricity or gas takes up a large portion of your energy bill. With Solar water heaters, you won’t just be having substantial energy savings but you will also be playing your part in the green house gas reductions. This may qualify you for various government renewable energy rebates.
Posted Tuesday 19 Jul 2011 @ 5:38:07 am from IP #
