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Forum Index : Solar : Deciding if I should build this solar heater
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| rogerdw Guru  Joined: 22/10/2019 Location: AustraliaPosts: 852 |
Thanks Tony I appreciate that. It is pretty rough and really didn't take long to throw together once I decided to stop thinking about it and start doing something. And I did get some help too (see pix below) ... told him it was an adults meccano set. Yes, after Dave mentioned them I remembered your work with cooling your treadmill motor generator and spent some time looking on eBay. I found a fairly gaudy looking one for just over $40 which can log the data which then can be downloaded via a USB connection. "This meter is a digital anemometer for measuring the ambient temperature, humidity, dew point temperature, wet bulb temperature, wind speed, and air volume." Thank you for that suggestion, I'll grab a wattmeter as well. I reckon I should be able to do that and will be handy to know an actual output figure. This morning before measuring anything, I pulled the tubes out and retrieved the one that fell through. I drilled through near the top of each tube and once I pushed them all into the manifold again, I fed a 1mm copper wire through them all so they cant slide through. I doubt I'd get away with dropping a tube into the glass too often.  Forecast is for 19 today with some rain ... and it is overcast 100% cloud and quite dark ... and has rained a little. 12:19pm temp inside manifold with no fan yet = 33.3 ... Ambient = 16 Fan on ... 12:20 ... 44.6 ... took a minute to climb to this 12.22 ... 38.6 12:27 ... 34.2 12:31 ... 32.4 12:43 ... 28.7 12:47 ... 27.8 1:10 ... 26.5 1:53 ... 22.9 It's still quite dark and gloomy with clouds in front of the sun. The temperature inside our house is 19.6 at the moment ... so I don't know if a breeze of 22 degrees would help very much ... but there was a really useful amount of heat earlier for probably an hour. And on top of it, there are only 6 tubes plugged in ... and for my first working unit I want to fill the rack with 18 tubes. Can I assume that I should get 3 x the heat energy from 3 x the number of tubes? Lots of clouds blocking my heat!!!  Looking into the air outlet  Managed to drag him off his screens for half an hour. Such a mean dad.  Cheers, Roger |
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| Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1578 |
Another Brilliant Idea! Might be good to enclose the element and put it in front of the tube fan so there was a positive airflow through it to make sure it didn't overheat. Unless it was more or less enclosed, I perceive the air might try to go around the element and not cool it sufficiently. It's a bloody good and clever way of working it out Tony. I have one of those AC power meters built into a box with a 4 KW Rated PWM. This allows me to plug things in and ajust the power output and see exactly what something is doing. It's been Bloody handy with a whole bunch of things. Because they are cumulative you can see power used over a time period. was handy to plug the old bar fridge in and see it was using shiploads of power for whatever reason. Sorry to get rid of it, thing was at least 50 Yo but.... was using more power than replacing it cost. Meter This is the type but have a look around for pricing. I think I got mine for about $15 and they can't have gone up that much. Also the ones with the CT clamps are good because then you don't have to run the power through the meter. Those invariably too small power terminals on the meter make getting anything larger than 1.5mm cable in a chore if not impossible so for mine the CT pickup type is much better. I have one just on it's own as well just for metering but I use the one with the PWM a lot more. I can run a 3.6KW water heater off a normal power point just by turning the power down to 2 KW or whatever to keep the draw at a safe level. I like the anemometers with the built in thermometer. Think I'll order one of those. Perfect for testing my own heating ideas. Edited 2021-05-03 15:09 by Davo99 |
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| Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1578 |
I'm impressed you could get any heat rise at all under those conditions. I would have thought that cloud shading would have killed them completely.... Like it does PV pretty much. All things being equal, I would suspect you may possibly get more than 3 times potentially. The inefficiency should be the same but shared over more tubes might give a net total gain. If you could insulate your ( longer) outlet manifold to stop heat loss there, I think you might pick up some heat. What a good Looking and happy young man. Big smile on his face out there getting his hands dirty with Dad. Brilliant! Treasure every Moment Mate, they grow up in the blink of an eye. My boy loved his Video games as well but I never tried to stop him from having them, I just made sure he had a Balance of other things. He did play a LOT of sport which took him off the computer/ games and a few times I did a bit of a time and motion study and found his screen hours were much less than his outdoor ones even though they seemed a lot so all good. He also as a teenager got interested in graphic design and used to design posters for school events and covers for the school mag and did a few education department publication covers and illustrations. That was all off his own back. I bought him a very expensive book on Photoshop when he was about 12 which I thought was over his head but he treasured that book and certainly made the most of it. It was money very well spent. He went into an apprenticeship as a Builder even though the hands on interest came on in the later years of high school but he picked that ball up and ran with it real well. I honestly think the Tradies have enormous potential in the future world. There are a lot of academics out there but no matter how well off they become, they still are going to need someone to build, renovate or maintain their house, Fix their sh*tter, do their electrical etc. I used to tell my son to do his time and then work on the business, not in it. Lot of potential to run ones onwn company and have others do the grunt work. You need to be smart about it but the potential rewards are Huge. Any number of people you can go to to make a web site, fix or program a computer, sort your taxes etc but see how long it takes you to get someone to Fix the plumbing, give you a quote on renovations, lay concrete or any other trade job AND, tradies can go anywhere and have work, they are not limited to being in the city. Looks to me like you are doing a fine job with that Boy Rodger and what a happy, bright young fella he looks too. |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
Probably better to add extra heat after the tube fan and solar, that way it doesn't effect how the solar functions on a cold day. The heating element should be totally enclosed, it does not matter if some air sneaks past. Once the air is mixed in a decent length of pipe, all the heating power will go into the air, and it should be possible to get a reliable repeatable result. Another use for the fan heater might be to just run it as a fan heater for a while, and judge how effective 2.4Kw of hot air warms up the living space. Then you have some basic numbers to judge the effectiveness of the whole thing before you go to the trouble to build it all properly. Cheers, Tony. |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
It would also be rather interesting to compare your results to just running an equivalent bunch of normal solar panels driving an air heater electrically.... Cheers, Tony. |
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Murphy's friend Guru Joined: 04/10/2019 Location: AustraliaPosts: 648 |
Davo99, I would not recommend this particular meter, its only rated for 260v Ac. I had two of them blow up inside my inverter, causing a nuisance. Those type of meters are available with a 300V Ac rating, well worthwhile to search for them. |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
I bought a couple of these a few years ago, and they both still work fine. https://www.ebay.com.au/itm/124610649363?hash=item1d035f9d13:g:940AAOSwPzhgQFAx Edited 2021-05-03 20:03 by Warpspeed Cheers, Tony. |
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| rogerdw Guru Joined: 22/10/2019 Location: AustraliaPosts: 852 |
Yep, I'm going to have to start paying consultancy fees soon.  I've often thought of buying one but never got around to it. I have several variacs to choose from so that will solve my variable power supply issue. I might need to grab one of those too eventually. I put in a few orders this arvo on eBay for one of these ... Anemometer The datalogging function sold me on this one. As well as a wattmeter, and a pair of temperature dataloggers ... temperature dataloggers ... and an additional battery for my Hitachi cordless stuff. Yeah I think that was what excited me so much this morning. That despite the rain and the dark gloomy conditions, there was still heat to harvest. That would be nice ... and I can see what you mean that with a small number of tubes it must be harder to get through the initial temperature barriers ... but once you're through them ... the rest is gravy. I agree too that insulation is going to help a lot. Whatever way I end up building my manifolds ... the hot one is going to have to be insulated well ... and preferably on the inside rather than outside ... otherwise I'm going to have to deal with trying to keep the insulation dry on top of everything else. Cheers, Roger |
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| rogerdw Guru Joined: 22/10/2019 Location: AustraliaPosts: 852 |
Thanks for the kind words and the sentiment Dave. He is an absolute delight and we are really proud of him ... and he always amazes me with what he comes out with. I'll send you a pm. Yeah, I think that is all we can do. To cut them off altogether would probably feel excessively harsh to them ... but as long as there is a balance of other activities and interests, it's still so much better than what some kids go through. That is awesome. It's amazing what talents pop up in some kids and makes me wonder where they come from. One of our girls was always good at art too ... and we bought her a graphics tablet system so she could also do digital art. She's just had a four page comic published in a marketing magazine in the US and all sorts of work offers are starting to filter in. Yes, I agree. And once he has the skills from his trade he can still decide to carry on using them ... or take the next step and run his own business or manage someone elses. At least he has a choice. We have a friend who is a great mechanic and when his boss retired, he helped him to take over the business. He probably would have been able to run it well being a manager ... but it would have been a terrible waste dropping his mechanical skills ... so he employed a manager to do a lot of the day to day stuff and he stayed on the tools doing what he is excellent at. Been doing that for 6 or 7 years already and still going strong. Thank you again Dave. I showed him his picture above and read out what you wrote and he really beamed. Thank you. Cheers, Roger |
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| rogerdw Guru Joined: 22/10/2019 Location: AustraliaPosts: 852 |
Can you expand a bit more on that please Tony, I'n trying to picture just how enclosed the element might be ... and with what. Yes, makes sense. I do need to find a fan heater and play around with it a bit to see just what volume of air it displaces and what actual temperature come out of it. I've been going to ring an aircon tech to ask a few questions as well. Must do that tomorrow. That's exactly what I ordered today. I nearly bought two, but decided I would look into the ones with CT clamps and buy one of those as well. Cheers, Roger |
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| rogerdw Guru Joined: 22/10/2019 Location: AustraliaPosts: 852 |
I thought I might add some more details to the figures I posted at lunch time today. I'll include the ones already posted so it's easier to see the whole picture. Forecast is for 19 today with some rain ... and it is overcast 100% cloud and quite dark ... and has rained a little. 12:19pm temp inside manifold with no fan yet = 33.3 ... Ambient = 16 Fan on ... 12:20 ... 44.6 ... took a minute to climb to this 12.22 ... 38.6 12:27 ... 34.2 12:31 ... 32.4 12:43 ... 28.7 12:47 ... 27.8 1:10 ... 26.5 1:53 ... 22.9 2:55 ... 26.5 ... cloud is dispersing slowly 3:10 ... 29.8 ... few more breaks in the cloud at times 3:30 ... 24.5 ... ambient 17.2 3:42 ... 18.3 ... big thick clouds covering sun .. see photo 3:54 ... 23.4 ... clouds just about clear of sun .. see photo 3:57 ... 24.2 ... full sun at last 4:10 ... 24.2 ... 4:30 ... 22.6 ... ambient 15.1 and full sun ... tho' <45 degrees to side 5:40 ... 15.7 ... ambient 15.0 and sun gone! The figures show the obvious of course ... that when the sun is missing or clouded the temperature drops accordingly. I went in to grab a coffee at 3:42 and there were thick clouds covering the sun again ... and I was surprised to see it as low as 18.3 degrees ... see photo of clouds. When I came back out with my cuppa 12 mins later, the clouds had moved and sun breaking through ... again see photo. It was encouraging to see the temp back up at 23.4 A few mins later it was full sun which added .8 straight away. I have to admit I was a little surprised to see the sun so far around to the west already by that time ... so really only hitting the array at less than 45 degrees. I think I walk around with my eyes shut most of the time. 3:42pm ... 18.3 degrees ... big thick cloud  3:54 ... 23.4 ... clouds almost clear  3:57 ... 24.2 ... Clear at last  Cheers, Roger |
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| rogerdw Guru Joined: 22/10/2019 Location: AustraliaPosts: 852 |
Yes, that would be interesting, though when you say an equivalent amount do you mean equivalent area? Because an equivalent area to the 6 tubes would be only one panel ... so at most say 400 watts if a latest type panel and in ideal conditions. Will be interesting once I know the equivalent electrical output of the tubes. Cheers, Roger |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
If you pull the guts out of a fan heater, you usually end up with something that looks pretty much like this:  If the motor and rotor are removed, and the whole blower housing cut away, you end up with just a metal frame containing just the heating element. The whole thing needs to be totally enclosed by your pipe somehow, so all of the heat is transferred to the moving air. None of your heater should be exposed directly to outside air. So basically your big plastic pipe going into a rectangular box of some kind, containing the heating element, with another short length of plastic pipe down stream to mix the heated air so you can read the overall final averaged air temperature. Some air will go through the heating element, and some may leak around it, but that does not matter. The heater box could be made from just about anything, plywood and duct tape might be the simplest. You are not likely to be running the full 2.4Kw initially, and if you ever need that much power, there should be enough airflow to prevent the whole thing from catching fire or melting down. Fan heaters do not blow huge volumes of air, and you should have enough airflow to prevent the element burning out. These heater elements have a built in bi-mettalic over temperature cut out anyway in case the airflow gets blocked. So it should be able to protect itself if you keep the existing cutout switch connected in series with the element. Edited 2021-05-04 09:00 by Warpspeed Cheers, Tony. |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
Yes equivalent occupied roof area. Cheers, Tony. |
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| Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1578 |
The figures are impressive Roger. I spose it will depend though on the output as far as the total heating you get. That will be very interesting to see. One thing seems certain, you will be ahead with these over solar PV in the same space. I have a Car radiator Fan directly hooked to a couple of solar panels to cool my inverters at the back of the house not far away from where I sit here in my cave....errrr, Office. Although the fan rans flat out most of the time, It's amazing the variations you can hear in it's output from changing weather/ light conditions. You can look out the window and not really see anything but can hear the roar of the fan change significantly. When outside you can sometimes look up and see a wisp of Cloud or haze that you would not have noticed otherwise but the sound of the fan changes enough to be a very definite indication. I spose those with detailed solar Logging would see the same variations in output but I don't have that. The fan sound is my indicator. Not much sound today, Seems you sent your Gloomy weather up here. Annoying Drizzle that stops anything being done outside but isn't going to provide any worth while water we could use with everything having Dried out from the floods we had 6 weeks ago or so already. This is the sort of days that combustion heating will win out over anything solar.... although I think the solar is a looooong way ahead in the cooler weather so far. Speaking of which, although it's a bit ahead, have you come up with any thermal storage Ideas Roger or just looking to heat soak the house? An insulated Drum or old hot water heater with a Circ Pump going to an intercooler/ Car heater core might be workable. Run the warm air though the core to heat it through the day and reverse the airflow ( or put an AC Diverter duct in) to vent the heat into the house though the evening.... if you need it. Heating and cooling would be the same only instead of ducting the cooled air when heating to atmosphere, the fan still blows through the core and the diverter duct goes to the other output and pushes the warm air to the house. During the day the diverter would be the same way and the pump could be turned off so the heat was going straight into the house. The heated core may provide a little " capacitance" for short interruptions from cloud etc. My house certainly needs reserve heating at night with it's crappy insulation and far too many Thermal Mistakes.... I mean windows. I'm well up on the solar generation atm so I'll be just putting a couple of fan heaters on low to stop the place Chilling over the next few days of predicted gloom and rain. Not complaining, things are getting dry here again and hard enough to stop the lawn going brown in winter. Seeing what you get in the less than wonderful weather may be the real ace in the hole with the tubes as it's easy for things to work when it's ideal, the test is when it's not. |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
A big difference between say 12C and 18C, still neither exactly toasty warm, but it does not take very much to knock the edge off the early morning chill, especially on the shady side of the house. The whole key to this might be the different parts of the light spectrum being used between direct solar thermal, and solar photovoltaic. I expect they will behave very differently to each other in varying sky conditions. But exactly how I have absolutely no idea. Fascinating stuff. Cheers, Tony. |
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| Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1578 |
That is a very interesting observation. Perhaps using both would make the most of the ( less than perfect) conditions at any given time? When conditions are good, then they would both be delivering well. |
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| Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1578 |
From what was said here ( or on another thread) earlier, the Tubes should be much more efficient at producing heat. Another of my baseless and unfounded guesses is the Tubes are likley to produce more heating power than the panels will produce electrical power under Cloudy and less than perfect skies... when you are most likely to need the heat. Several fan heaters I have are just Fans with an element sat in front. They can be had for $20 in many places, Kmart seems to have really cheap electrical stuff or you could try the bargain shops. Might be possible just to remove the fan blades and put the rest in line or take out the element. Must have some Heat resistant support. You are certainly Correct about airflow Tony. Those fan type upright style units would barely blow out a candle from 10 Cm away. Having measured mine the other day, I noticed it is marked 2400W but only does High 1800's flat out. The ones with a blower seem to be the better units and the fan ones are more like a spiralled element spread out to the approx size of the fan blades. I think these may be easier to Modify. You could have a look at what you have at home Roger and go buy a new one and cannibalise the old one so the Chief of Domestic affairs and corporate Finances is not displeased. |
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| rogerdw Guru Joined: 22/10/2019 Location: AustraliaPosts: 852 |
Thanks Tony, I get it now. It was the fully enclosed part that had me wondering. I had often thought of collecting some of these, as much for the motor and fan as anything ... but I'll check out the dump shop etc. That is exactly right. At 8.45 this morning ambient was 10.6... all overcast and mostly cloud again. I fired it up and it crept up to 16.6 ... and I actually noted "feels warm compared to ambient" I think you're correct there too. I probably do need a solar panel leaning against the frame as well and take corresponding readings along with mine. I think I had the wrong idea about these tubes and the heat collection because of my early testing. Early on I just had them lying in the sun and was measuring the temperature inside from time to time ... and they seemed very slow to drop after building up. On top of that, if I did blow air into them, it took say 5 minutes to get the temperature down a reasonable amount. Now though, that I have them with a constant airflow through them ... I can see an almost instant change in temperature in relation to sun exposure. Just this morning with the cloud breaking up and the sun coming and going constantly ... I've seen a high of 30.4 and then a low of 24.2 over just 2 minutes. It follows very closely the amount of sun shining (as you would expect). Having said that, if I allow the heat to build up inside the tubes and then turn on the fan ... there seems to be a buildup of heat that takes several minutes to disperse before the temperature drops down again to a level consistant with the actual amount of sunlight on the array. Cheers, Roger |
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| rogerdw Guru Joined: 22/10/2019 Location: AustraliaPosts: 852 |
Yeah, I've definitely been encouraged by the figures I've seen. Yesterday was probably almost a typical winters day for around our parts ... and even then, there were a couple of hours of useful heat available. It will definitely need an active control system to get the most out of it and not have it blowing cold air when it shouldn't ... but I don't see that being all that hard to set up. Funny you should say that ... I have the same experience with the solar pump on my pool. As I walk past the pool area I hear the pump running ... and I often am amazed at how slow it seems to be running for a full on sunny day ... and conversely, just how fast it can sound when it's a fairly ordinary, almost grey sky. I then start looking around for just why that is, but clearly it's not just maximum sun for maximum power ... at least with my panels and motor setup. Yeah, sorry about that. This is really the first taste of winter we have had, it's been really beautiful weather until now. Yeah I have, but not sure I can afford what would do a really great job. Did you see my post a few days ago about PCM ... phase change material. A good PCM can store up to 10-12 times the energy you can store in a drum of water or a pile of rocks. I badly want some to experimant with. Mine too ... and PCM is just the answer for cold nights after half reasonable days. Cheers, Roger |
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