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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 |
I had thought of buying some reflective mylar like they use in grow tents and hydroponics ... and if I can't get it already bonded to a backing ... glue it to some coreflute. Coreflute lasts for years in the weather, though I don't know how well the mylar will survive. Worth a try though. Mirrored stainless steel sheeting would be nice ... but a bit out of my price range I'm sure. Cheers, Roger |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
How about Coreflute covered with some of that heavy reflective foil used in the building trade ? https://www.bunnings.com.au/ametalin-1350mm-x-10m-silverwrap-ld-reflective-wall-insulation_p0811067 Cheers, Tony. |
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| rogerdw Guru Joined: 22/10/2019 Location: AustraliaPosts: 852 |
Great idea, I hadn't seen that material before. I need to work out the sizes of material so I can put in some supports across the frame ... before I drag it up on the roof. Each side requires a reflector 2.4 metres x 1.8 metres ... but of course thats too big to find material in one sheet ... so I'll need to add in supports for the joins plus stop it flapping about in the wind under the tubes. I do have some 4mm stainless cable left over from a job that could be strung back and forth underneath ... but a few lengths of angle welded in place would be stronger. Cheers, Roger |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
How about four sheets of 6mm Hardiflex 1.2m x 1.8m ? Absolutely weatherproof but really really heavy. The weight might actually be an advantage in the wind. https://www.bunnings.com.au/james-hardie-hardieflex-1800-x-1200-x-6mm-cladding-2-16m-_p0711079 Cheers, Tony. |
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| rogerdw Guru Joined: 22/10/2019 Location: AustraliaPosts: 852 |
I guess that would work ... at least it shouldn't flap around too much as long as I can get some screws into it in enough places. If I do a dry fit down on the ground to get the holes in the right place, and thread them ... then I should be able to bolt it together on the roof. Probably need some big washers on top so the edges don't crack away. And also need to find a compatible glue that'll keep the silver wrap attached. By the way, I weakened and ordered 20 x 6.5 mtr lengths of new tubing. And while they apparently deliver up here on Wednesday's, they wont be here till next wed coz of the shut down. Still beats having to go collect it myself ... and have to cut it up there to get it on the trailer. Would have been nice to use up all that second hand stuff and save on the new ... ... but when I start adding up the cost of all the rods I've bought, the gas ... not to mention the time ... I wish I'd aimed for new from the start now. Anyway, I have learned a bit about welding aluminium ... and I still need to be able to weld them into my holy angle. Plus I am certainly more confident that the device is worth building ... so not so afraid to sink some money into it. Cheers, Roger |
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| Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1578 |
For a reflective backing, You may find stainless steel ( I think it comes in a polished variety) in very thin gauge may be a lot more economical than you think. Wouldn't hurt to ring and get a price anyway. |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
Some big pieces of cardboard and cooking foil held on with sticky tape should work as well as anything else for an initial back to back test. In fact you could try it out on your small prototype first, and see what kind of difference it makes. Edited 2021-07-27 17:03 by Warpspeed Cheers, Tony. |
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| rogerdw Guru Joined: 22/10/2019 Location: AustraliaPosts: 852 |
I know I've seen that youtuber in Europe who uses it a lot and makes it sound like it is cheap ... but I bet it's not cheap out here. I'll have to ring around to get some idea before I dismiss it completely. Yes, that should be easy enough to do ... though I do already have those three reflector panels behind my existing tubes. It's really hard to compare results because of the constant changes that happen out in the sun. I really need two systems side by side to be confident. Today started off well ... but a change with rain came in about lunch time. On top of that, one of my loggers glitched for some reason and must have changed its recording times somehow. If you look carefully you can see where it should line up ... so it's still worth posting to see what poor conditions do to the results.  Cheers, Roger |
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| Solar Mike Guru Joined: 08/02/2015 Location: New ZealandPosts: 1138 |
Last winter I made a shiny reflector for a ground post mounted 2 sqM solar hot water panel; by placing a sheet of shiny foil between two thin sheets of 1mm clear polycarbonate and sticking all the edges together with aluminum tape, then screwed to a timber frame. The reflector was approx the same surface area and sat vertically behind the 40 degree sloping collector to catch and redirect the low angle sun onto the collector. Hot water production increased 10% or more. Cheers Mike |
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| Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1578 |
Mate of Mine used some as a splashback in the kitchen he put in the stables. Said it was pretty reasonable. Then again, the kitchen in the stables would not be at all out of place in a home magazine. He built and office in his shed that looks like a boardroom and the " Shower" bathroom looks like something out of a luxury day spa. He does not do things by halves but the stainless looks excellent. I can relate to Tony's earlier comment about the tubes being excellent for the lead in and run out of winter. Your weather seems much like ours has been last few weeks with a lot of cloud and only half sunny days. I sort of gave up on my solar panel heater because of that. Where it is located does not allow it to have full sun till about 11 Am and then the clouds would roll in and then it was useless. We did get quite late into the season that would normally be cold with brilliant sunny days. I am sure your tubes would be Punching out the heat then. The current weather makes your setup a little iffy but then every year is different and next year may be much sunnier even if cold days. We seem to come out of winter here, have beautiful September weather and then the first week or 2 of October is Chit just when you put the cotton sheets on the bed and did away with the warm clothes. Usually rains for a fortnight or best part thereof as well. This last week since I got the Diesel going again I am running it much lower and the house is staying at 20. I was blowing through a tank of fuel every few days before, now it's just sipping it. We had one day with a low of -2 then 5 days later the low was 12! It makes a HUGE difference to the heat input required. You mentioned gas Roger. Are you giving the wood burner away or it that just for Quick heat when you don't want to light the fire? You have Gas, wood and reverse cycle? You must have the warmest house anywhere! :0) You also mentioned putting up a sizeable PV array. Not sure if you already have a legit system you are going to add to or just a DIY but using electric heating may still be cheaper when you can generate your own power. Given the tube heater will be taking an amount of load, you may not need all that much power.... although I think you said you weren't keen on the AC? I can understand that. Coming back to sensor placement, I tried putting the sensor for the diesel quite close to the outlet. The outlet tube does extend past the sensor's location so it's effectively to the side and behind it about 100mm but the reading I'm getting seems accurate to the rest of the room in various places. Only reads a degree difference to the heat gun and that's more than within error margin for those 2 questionable Thermo's. |
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| Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1578 |
BTW Roger, I found a welding Vid you might be interested in. Not entirely applicable but you may pick up a few pointers from it. welding |
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| rogerdw Guru Joined: 22/10/2019 Location: AustraliaPosts: 852 |
Thanks Mike, that's useful to know. Gives me another option to try. What was the reflective material and has it deteriorated since it's been up? Mmm ... that's hopeful, though the prices I found from the US were pretty crazy. When I first started I reckon we had a few days when it was pretty lousy ... but then it picked up and had been fantastic most of the time ... just the odd day that was poor ... but we've had a lot more of them recently. I don't know if this is a normal winter or not really ... feels like it hadn't been all that cold or wet ... but we've certainly had plenty of rain and now cold ... so maybe it'll get real wintery for the next couple months ... and make my machine ineffective! Reminds me of a microwave ... cook something at room temperature and it's all good ... but put in food from the fridge and it takes ages to heat and you start thinking is only at half power. Well I'd like to give the wood away ... though I don't think I will get away with that. I mentioned gas because I still have a couple gas heaters from our last place that would run on bottled gas ... and if we only need a bit of heat to suppliment the solar heater in the evenings and early mornings ... gas would be so much easier than chasing wood. Our hot water uses bottled gas ... and it probably wouldn't be that hard to have an outlet plumbed in for a heater. That's my lazy side showing now.  Yes, that's my next project ... along with going back the Warpinverter. And no, we don't have an existing system, only the panels for the pool pump. That's a good point about using electric heating, I hadn't really thought about it ... and just for the fill in times, might be helpful. Neither of us are all that keen on the aircon because it still seems so draughty (for heating) ... but if we had plenty of power, that would also be an option. I was thinking of you earlier today when I got an email from aliexpress advertising waste oil burner parts Cheers, Roger |
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| Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1578 |
And Might be Cold and sunny and your setup will work a treat!! Every day, or half day it does work will be a win and I'm sure at the end of the season with your monitoring you'll be able to see how much it all added up to. If you got a months worth of heating out of it, it's the same as if someone said I can reduce your heating bill by 33%. You would think that was worthwhile. It's not a one winter deal either, it's an every winter situation. Put my foot it it after saying that but confirms what I said earlier. Temps dropped lower than expected last night. Only had the Diesel on low. Got up during the night and it felt Chilly and the room was down to 17. Craned the Diesel heater to half and put the fan heater on low. That's not much but still heat. Got up late after the dog slept up with us instead of on the end of the bed where she normally stays and it was still 17 at 7:30. Goes to what I said about being impressive about your heater being able to pull your place up 5o. Also interesting hoe accustomed and sensitive one gets to a certain temp. Even the dog Felt Chilly. She never comes and Cuddles up with us unless she is cold so she felt it as well. I could run the diesel on the thermostat but then the thing would pretty much run flat out all the time I reckon. It's not very accurate in it's management. There is that in it I spose. I have a gas heater up the back but I'm not rich enough to use it. I remember when I did it could demolish a 45 Kg Bottle in about a fortnight and that was run for 4 Hours a night if that on the lowest setting. Bottle gas is NOT cheap here now. What I found couple of months ago when Crunching the Numbers for the Diesel, Much cheaper for me to get 9 Kg bottles from the servo than the 45's which have to be delivered. Talking to me Neighbour couple of days ago he said he is giving away his wood heater. wants to get gas and one of those big tanks that sits above the ground. I thought that sound cheap but the guy is cashed up with well over a Mill in the bank so not going to be a concern. That being the case, for summer I'd look at adding an electric hot water heater. If you have the solar available, it would be cheaper to use that than the gas. Depending on how you want to do it you could either set it up as a pre heater ( at full heat) going into the gas heater) or just parallel them so you could turn the gas off and just run the electric when you had the power. You could either use a voltage dependent relay like I have to use the hot water as a dump load when there was excess power ( voltage) or just have a light sensitive switch on a relay. If you have analogue meters you can wind back during the day, don't matter when you use the power, if you have a smartarse meter you can set up to only use your own power. You have the space to do a pretty decent PV setup and summer should give you 5, probably closer to 6X generation in kwh so you may find you have power to burn. Alternatively, My Idea of using the tubes through a heat exchanger and do the hot water that way would also be an option. With the temps you are likely to get, shouldn't have ANY trouble making all the hot water you need. One thing is for sure, you are certainly going to have some creative and cost saving options available. Definitely see your home featuring in the Eco magazines!! :0) Nothing lazy about not wanting to sweat your guts out doing fire wood! That's just good sense! I have every Tool and convenience available and it's still hard work. Run my mates commercial automatic firewood processor worth over $100K and I can well see why he can't find people whom want to stick with that job. It's STILL hard Yakka especially doing it as a Day job every day. You might like to look at the oil Filled Column heaters. I have a couple at the holiday house and think they are great. Granted, the whole place would fit in the corner of the kitchen here but they are a gentle, comfortable heat. Have a little box/ through the wall AC there which is a ball tearer and heats and cool the place with ferocity but like you say, it's Draughty and this one is noisy. I use that to pull the temp up at the same time I have the oil heater warming up then shut off the AC. The oil heater keeps the place real nice. There is one in the bedroom and I put that on low and keeps the place beautiful. don't even sleep with a doona in winter. You can buy them cheap on Dumbtree etc so might be worth getting one just to try. I think you would be happy with it but they are not fast heating like a fire but they are excellent and maintaining a comfortable temp that seems very even in the room. I have seen those before but looking at the nozzles, I always thought they ran with compressed air. Looks like all they need is an air Blower for the combustion chamber. I did not know they would run like they are shown. Something to look more into. Thanks for the heads up. |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
The coldest frosty mornings usually go with a clear bright starry night, along with a cloudless sunrise. Perfect scenario for the "Roger Tubes". Cheers, Tony. |
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| rogerdw Guru Joined: 22/10/2019 Location: AustraliaPosts: 852 |
Yep, you're right. I'm usually an optomist but occasionally I do start to wonder what I'm doing. Very good points too, thanks for the reminder. In fact I had figured that it would be cool to set up a raspberry pi or something to monitor the output when it has one ... and actually record the kWhrs it produces. Shouldn't be that hard if I only have one or two fan speeds ... log the temp in and out ... and the length of time it's on. Pipe dream of course, but nice to think about. The "it's an every winter situation" is very apt too. I have to keep reminding myself that this potentially could last 20 or 30 years with virtually no maintenance required. About the only thing to wear out may be a fan motor or two ... and a bit of rust on the frame to clean up and repaint. And that's why I also have to fit a dc motor to run off pv panels ... so the uneducated can't point to the little 50 or 100 watt fan and say "but it runs off electricity ... that's where all the heat comes from" Haha, that's why mine were still upstairs above the workshop. Our gas is $135 a bottle, though we don't use anywhere near as much since a certain couple of girls left home. I do have a smaller bottle for the barbie that I could hook up temporarily and they are only $20 to refill down at the carwash. Yeah, I keep thinking that if instead of all the time I spend cutting, collecting, shifting, splitting, chopping ... I were fixing some of those controllers etc ... I could buy 10x more wood than we flipping well need ... I just need some adjustments in my thinking. Addressing that is certainly in my plans ... some sort of pre-heater at least ... though I need to finish this and get on with the warpinverter and panels next. I looked for more info on how they build them, but didn't find anything. Looks like possibly a good start with all the components though. Haha, yeah ... I didn't think it was all that cold this morning when I got up ... but it's certainly come in cold now. Came in for lunch and put on my ugg boots and beanie. It's cold, blustery and has been raining ... but the whole time I've been in here I can hear the fan running. I don't know how it's getting any heat out of anything but it's pumping 34 degrees at the moment so I'm rapt. I'm also changing my thinking for when the big one goes up. Before I had just planned to have an outlet in the lounge and one in the games room which is always cold ... but now I'm thinking I need the main one here in the kitchen/living area ... even though that's where the wood heater is. That way, with the wood heater off, it is still the first area that gets warmed, because that is where we all mostly spend our time inside. Once it's warm enough in here ... we can switch in the inlets to those other rooms to spread the warmth further ... which I have no doubt we'll be able to do fairly often. A couple of those damper valves should handle that ok, along with some smarts of some kind. Cheers, Roger |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
Yup. Easy enough to do with one or more room thermostats and some relay logic. Once your main living area is up to temperature, divert the heat somewhere else, then maybe to a third choice on a priority basis. Cheers, Tony. |
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| Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1578 |
Maybe I just don't know enough to know what I don't know.... But seems to me it should not be that hard apart from programming the PI itself. You have 2 of the 3 parameters, air flow speed and diameter of the Pipe so qty of air. Even if you didn't have that, Mass air flow sensor like in a car wouldn't be hard to work with, seen that done many times on DIY projects. All you need is a sensor for the temp and surely there should be a calculation you could plug into the Pi to give both an instant and cumulative output in KW. Although we think so much alike on so many things, we also think very differently. Now if this was my work of art and engineering Genius and someone told me all the heat was coming from a 100W Motor, the LAST thing I'd be doing would be trying to change their minds! I'd be saying "ya know, you are dead right, you figured it out. I'm making 4Kw of heat from only 100W of electrical input. I was going to market this myself but my wife wants me to spend more time with my family ( guess where I stole that line from? ) so I have decided just to sell the rights to this. If you are interested, I'll sell you the machine and give you full rights to the technology to manufacture them yourself and keep 100% of the profits. Can you imagine how much money you'll make?" That the side benifit of years of marketing, sales and advertising experience Roger. If there is a potential quid in it, don't argue with people, go along with what ever they say...... You'll never change the mind of the terminally stupid so don't try. If ever some do gooder accused you of Ripping people off, I call it the cost of Education. We all know anything fast and time saving costs a lot and this would be a real fast education that could save them many years and many dollars they might have otherwise wasted had you not been kind enough to help them. I certainly give them all the help I could relieve them of their money and make them smarter. Just the kind, generous, giving sort of guy I am! :0) Same as me. 45 Kg cylinder $135 = $3 Kg. 9 kg Bottle $20 = $2.20 KG. 45 x.80 saving = $36 Per 45 Kg cylinder worth. You can save enough to buy a 2nd 9kg bottle on the first 45kg worth so you have a spare Bottle. If you are lucky and really arsey, You can go to the scrap metal joint and pick up some bottles out of date or otherwise that look in good nick. The Punjabs at my local Servo never look at the date unless it's a rusty, crappy looking bottle which obviously shouldn't be filled. Long as the bottles look decent, you can have a good reserve. You don't want to be working all the time but there are better things you could be doing with that great boy of yours. Seeing you have all that spare ally tube now, You could build him a Go Kart. Practice your welding skills at the same time. Just put a little 160CC mower engine on it. I have one up the back that will put a huge smile on his face, clods of dirt on yours and a terrified look on his mothers dial. Exactly the sort of stuff a young man dreams of!! I looked again and they are not using the Nozzles I thought. They are standard oil furnace Nozzles as are so popular in the US. The trick to the setup as shown is in the electric fuel pump they have. Not seen one like that. I bought a Nozzle probably 20 years back but it had some weird thread and they run some high pressure too. I had in mind ( and in stock up the back) to run one off a power steering pump. Wouldn't need a very big AC motor to drive it for the flow and the pressure could be adjusted with a bleed off valve to lessen the load on the pump as well. The electric pump on the site would certainly be more economical and compact though. If you are going to bring the duct through the roof, you could either set it up with it's own diffuser like used for AC or look at dumping it in the AC return air plenum. This would allow you to distribute the air and may help the fan to suck it though as well. You may want to look at restricting the return air from the house though to avoid too much heat dilution. Wouldn't be hard or expensive to set it up with it's own duct work and diverters. Just be sure to put in a master damper so you can seal it off to stop the heat going out the room when you are heating by some other method. I think all you would need is a thermostat. When the main room hits temp, it opens the other damper for the secondary rooms. I'd still leave the main damper open as you'll still want some heat going in there so it does not cool off. |
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| rogerdw Guru Joined: 22/10/2019 Location: AustraliaPosts: 852 |
Sounds easy when you say it like that but I expect I should be able to cobble something together ... or find someone who can help me. Haha, I hadn't thought of that. Maybe I can learn a thing or two. We rarely have bbq's here but I did go down last week to fill up my bottle ... so I could use propane to try and make my aluminium brazing rods work ... and even though the bottle does look brand new ... the guy wouldn't fill it. Said it ran out in 2012!!! I hadn't looked but I knew it was years old. He said just go to Bunno's and tell them it's out of date and they'll take it and give you a fresh one. Apparently they 'check' them out, paint them and fit a new valve and put them back into service. It cost me $27 but when it's empty I can go back to the carwash and they'll fill it for $20. Yeah, first thing my wife said was can we use it to make a flying fox that I've been talking about for ages. Not sure how ally tube would work for that. And we already have a gokart which I have to just about bribe him to use. Just a cheapy, but with a big motor and plenty of grunt ... and a decent paddock to roar around. The grandkids love it, but him not so much. He's keen for knowledge though and his reading and comprehension skills are years beyond his age bracket. Was reading a book to him last week which was pretty hi brow ... so the next night I asked if he was sure he wanted me to read more from it ... and he said yeah, I love hearing you stumble over all the big words. Thanks kid! I had considered that ... but was concerned that with all the other ducts it might create issues. I don't know enough about ducts and airflow etc. I do have a friend who is an AC tech, so I might invite him around to show him and ask my questions then. I am leaning towards a 3 way outlet just under the tiles, that will feed the seperate areas ... each with a damper valve so I can direct air or shut off completely to stop draughts like you suggested. For the inlet, I still like the idea of a preheater ... perhaps a more conventional air heater mounted on the wall outside ... with its outlet feeding into the big one on the roof ... and it's inlet fed from outside air. I keep coming back to that because like today for example ... as cold and unpleasant as it was outside, the laundry was beautiful and warm ... just a small room facing the sun with glass for the door and wall. Cheers, Roger |
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| rogerdw Guru Joined: 22/10/2019 Location: AustraliaPosts: 852 |
Yes, makes a lot of sense now, thanks. After this evening where I didn't relight the fire until 8:30pm, I think I'll make sure I do it earlier as it is noticeably less cosy in here now than usual. Must have had a false sense of security because it did feel nice and warm when I came in at 6:30 after a day of the solar heater supplying heat ... but obviously that disappears fairly soon.  Cheers, Roger |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
the temperature rise is considerable, and will be about three times as high with the big system. I think were gonna need a bigger blower  Cheers, Tony. |
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