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Forum Index : Other Stuff : Anyone do any real form of " alternative" heating or cooling?
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| Davo99 Guru  Joined: 03/06/2019 Location: AustraliaPosts: 1578 |
I'm always looking at different things for practical energy saving use and wondering if anyone here had anything they use practically in their homes? I have a bunch of possibilities beside brute force solar but a few things with that and others. I am putting in a spa I am going to heat with waste oil. The Idea there is to use that as a thermal mass and pump the water through a radiator and duct the hot air into the house. Other off beat Idea that I think would be practical would be to put a heater element in a 200L drum of rocks and sand and heat that through the day to radiate heat at night. Could use water which has a better energy density but if for whatever reason it leaked, The dog would be moving in and I'd be moving out to her kennel. Other one I'm considering is bringing the lister engine down, putting it in a little garden shed I can sound proof near the house and using that in a Co gen setup. I don't have much idea for cooling but in summer there is plenty of solar to Run the AC so no real problem. I do use a water mister on the outside coils and they seem to make a big difference to it's efficiency on the real hot days. There is a lot that one can do but some things are more practical easily implemented and used than others. Anyone done anything practical and Out of the Box? |
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| Georgen Guru Joined: 13/09/2011 Location: AustraliaPosts: 462 |
One method that captured my interest is out of my reach, as it involves larger block of land and quite a lot of money. It is "just" say 300mm diameter tube loop that starts in house and comes back to house in different place, buried couple of metres underground and few hundred metres long with fan to move air. Supposedly uses heat exchange for heating in winter and cooling in summer. Got impression that you have larger block of land and machinery, so could have a go at it, providing you can spare lots of money on materials, fuel and machine maintenance. George |
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| Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1578 |
Yes, I have seen a couple of Videos on this showing people in the states using it for greenhouses. The Vids made it look very workable but reading up on it some more I found a lot of people talking about issues with moisture and mold and spores in the vent pipes causing problems. While a very interesting concept that appeared to work very well, not something I'd be wanting to endure the wrath of the Mrs tearing up the yard to try. I think it comes down to what you alluded to, the cost of materials and construction would probably make more conventional methods like solar a better proposition for most people in Oz. I did ask a mate who does AC a while back about a ground loop system for heating and cooling as he was involved with one somewhere. He said the amount of Pipe needed and the area it had to be spread over was significant. He said the one he was involved Worked fairly well for what it was because they did go a bit deeper than normal in the ground. He said even though there was supposed to be no benefit after a certain point (6 or 8 ft? ) He said the system when it was up and running was doing better than expected so he thought there had to be some benefit in the deeper pipe. I was thinking of this the other day as I was looking at designs for building a deep ripper for the tractor. I saw how they used them for pipe laying with an attachment and the very minimal damage they cause the ground. It also then dawned on me that rather than run round the edge of the lawn and get a couple of hundred meters in, I'd need to put many hundreds of meters in to get any benefit. Solar or oil would be an easier alternative for me and get better results. I haven't tried a water filled collector I have seen made of coils of black pipe. I wonder what the efficency of those is compared to solar PV? I think to get anything good out of them you need to box them with a glass or perspex top. A friend did email me the other day about those solar air heaters. Basically tubes painted black placed in the sun, often over windows that cold air goes in one end and warm out the other. I haven't tried that but I did a couple of winters back try putting some black curtains in the north facing french doors. There was an air gap at the bottom and the top for convection but I was pretty disappointed in that I really couldn't tell any perceivable increase in warmth in the room. The 2 doors were each 2m x about 1800 and the curtains extended well past the sides. It though that was a reasonable surface area to work with and I would have seen some temp improvement but if there was, it wasn't enough to be worthwhile. I think for air heating the winner would be to box in and seal under solar panels and blow air under them and duct that into the house. Even on the coldest but sunny winters day, they can be uncomfortably hot to handle. Wonder if anyone has tried and calculated the heat recovery from that? |
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| rogerdw Guru Joined: 22/10/2019 Location: AustraliaPosts: 852 |
Hi guys, just following your thoughts with interest. A while ago I saw some evacuated tubes (about 35) for sale on FB Marketplace but coz they were a fair way away I didn't follow through on them. They were from a water heater collector that had failed and the owners put them up for $20. Kicking myself ever since! I was trying to work out if I could use them for heating my pool or perhaps heating air to funnel into the house during winter ... but dragged my feet too long and they were sold. And then recently I saw a heap more that were offered ... but these didn't have the copper tube collector in the end ... the bit that transfers the heat into a manifold ... so I imagine they are not of much value. Is there any way those tubes can be used without buying or making an evaporator (or whatever they are called) for each tube? Cheers, Roger |
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| Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1578 |
My only knowledge of Tubes is through a very environmentally Conscious Friend. He spent some considerable money on an evac tube water heater. I don't know the type as I am aware there are several but it was probably around 10 years ago now. Some time later he took the heater down and replaced it with PV panels. I was surprised knowing the money he spent and the enthusiasm he had for it initially anyway. When asked why he said the things were either too efficient or not efficient enough meaning the water was hot by 9am in summer or it never got hot without being boosted at all. He is a scientist / engineer that works in the aerospace industry and as such is very particular about monitoring and keeping records. I have no doubt he would know what was going on and calculated the energy efficiency to the joule. He was much happier with the PV and a resistance water heater. If the Tubes didn't work for him then I would think one would be better off with panels. I have several friends and if I want to know about something, I just ask them what they are using or doing and do the same. I have learned that if it's good enough for them, I'm not going to do any better. :0) If you could use these tubes for air heating, I don't know. From what I understand the ones with the ends for manifolds get REALLY hot so I'm not sure air cooling would be sufficient. Might have to water cool them then pump the water through a HE and duct the warm air into the house. I have seen a lot of conflicting opinion on the tubes. Some say they are much better than PV, others not. 2 Things stand out to me with them. Plumbing is a lot more expensive and complicated than wiring. The other thing as my friend said, they either heat the water early in the day and the rest of the time do nothing or they don't do a lot to start with. It seems there is no real way to get a balance with them. Even if PV is half as efficient, one may have their water hot before lunch and the rest of the afternoon they are powering their home or Feeding back for a credit. Looking on YT there seem to be a lot of people doing air heaters, including a couple of Vids I saw from a university professor. Hate to sound a smart arse but there were some flaws in what he was presenting that made me laugh. If a twit like me can see them and KNOW it's wrong, that is a severe worry. Really hard to know what sort of heating value people are getting out of these things. Seen loads of Vids where people throw a coil of 1/2" copper pipe on a fire and swear it's heating their uncovered above ground swimming pool too. Even if one set something up, I spose it's pretty hard to quantify what you are getting out of it. Not like putting a meter across an electric cable and getting a clear reading of the power being produced. |
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| rogerdw Guru Joined: 22/10/2019 Location: AustraliaPosts: 852 |
Yeah, for the pool I would have been happy to play with some plumbing ... but for inside the house, no way. I did envisage the copper ends being clamped to a number of large heatsinks inside a housing ... and channel air over them to harvest the hot air. Half a dozen Aerosharp heatsinks at 450mm long each would absorb some heat. Yep, I'm inclined to agree with that as well. Just so many more options with PV. Cheers, Roger |
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| Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1578 |
Sounds feasible. Yeah, I think that's the key, versatility. From what I have seen of the solar water heaters they aren't cheap and would go a long way if not cover the cost of a PV system. With that you can heat the water, cool the house, run the fridge, a Welder to Build something else and get a much faster payback on the investment. I was thinking of an enclosure for Panels for air heating this afternoon. Wouldn't be complicated but it would be bit of a construction. I think one would want 2 Panels to be worth while at least. I would pull air down from the top and try to have some sort of dispersal method inside so the air was drawn over the entire back of the panels much as possible. The arrangement could self power and one could also take some power from what was generated to make a resistance heater to further add to the heat output. Would have to be north facing obviously which would be a bit inconvenient for my setup with something like that and there is also the question of just how much hear the thing would produce? In summer I think one could have their own fan forced oven but in winter.... ? |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
Only fairly radical thing I can think of, was coupling up a Rinnai gas space heater to a tumble dryer. In winter the 2Kw required to run an electric tumble dryer was a bit optimistic with my small solar system, and natural gas is relatively cheap here in Melbourne. I bought a $50 e-bay victim tumble dryer, and an e-bay $20 Rinnai gas space heater, so nothing really expensive if the whole project fell on its face. Anyhow, a standard Rinni room heater takes in cold room air at the back up near the top. There is a double ended centrifugal blower at the top that blows cold air downwards through the heat exchanger, and hot air comes out of the front near the bottom. I removed the blower from the top, and bolted it where the hot air normally comes out, so the direction of airflow through the heat exchanger is reversed. The hot air now spews out vertically directly from the top of the heat exchanger. I bolted the Rinnai to the wall in the usual way, and mounted the tumble dryer on top, so the hot air blows upward into the inside of the tumble dryer cabinet. The hot air discharge from the tumble dryer exits through the wall in the normal way. Its an odd looking device, but it works extremely well. Both the temperature and airflow ended up being perfect on the low burner and low blower speed setting, and its been working for the last five years drying my washing without a single problem. Its a bit weird, and If I get a lot more solar panels, probably unnecessary. But it may be of interest to someone as crazy as I am.  Edited 2021-03-12 10:30 by Warpspeed Cheers, Tony. |
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| Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1578 |
That's Brilliant Tony! |
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| rogerdw Guru Joined: 22/10/2019 Location: AustraliaPosts: 852 |
I agree, amazing job there. I don't think I'd get it approved here though ... the wife might have an issue with the aesthetics ... and I'd be worried about the gas bill seeing we're on bottled gas. Just goes to show the differences between areas of Australia. Here we very rarely even use our tumble dryer. Even in winter the rain stops plenty long enough to get washing dry the majority of the time ... and if it's looking like staying damp for a while we use a clothes airer inside near the wood fire. Still one more step to hang it up I suppose ... but the power saving is worth it. For years I've wondered about venting the heat from the rear of the fridge to outside. Especially in summer it never made sense to pump it into the same room that you're trying to keep cool. Back then we were in an old stone home with wooden floors. Could have put a vent in the floor, a vent in the ceiling and box it in a bit. Then use a low powered fan to help the natural convection. Now we have concrete floors, so can't get airflow the same way. Cheers, Roger |
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CaptainBoing Guru Joined: 07/09/2016 Location: United KingdomPosts: 2075 |
I love it! I have a "scrap" Neff electric oven here that I am going to rip the guts out of and fit a MicroMite controller with a load of 4KVA SSRs I got cheap. Fed up of ovens going pop and it is a dark art to try and understand the maze of rotary controllers with dodgy PCB tracks etc. Had a few Neffs over the years (Mrs Boing likes them) but they can play up and then start working again like nothing was wrong, just as I am closing in on the fault... which is always near that front PCB. It has to be a simple task right? Switch the current to the elements, Heat a box, sense the temperature and then maintain with pulsing the heater. Throw in a few safety checks and logic... Edited 2021-03-12 19:04 by CaptainBoing |
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| Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1578 |
I have encouraged the mrs to use it more. We have the excess power at least 9 months of the year and even in winter, we can close the back door, open the laundry door and have the heat in the house. It's a little moist but isn't a problem as it can actualy be pretty dry here in winter anyway. Oh please! I have a psychotic hate for those damn things! Sick to death of picking the damn things and all the clothes up when they fall over and them being in the way and fallng down when you try to store them and tripping over the mongeral things. Uggghhh!! I have literally hurled a number of them out the front or back doors in fits of rage. Amazing how an unstable person like me can be set off by the most innocent of things! When we recently re did the kitchen, I had to move a wall and put a vent clean up through the ceiling above the back of the fridge enclosure to take away the hot air. It's a reasonable snug fit at the top and I have given it some smoke tests at the base and sides and there is definitely a draft effect going on. Might take some heat away in winter but with all the windows and doors in this place, I think there are about 50 other heats losses of more concern than that. in my old house that was on piers with wooden floors, in summer I had a tube fan sitting over a hole pulling air up from underneath the house. It was amazingly cool even after days of scorching summer heat. I improved the effect after noticing the ground under the house was drying out and the effect diminishing by putting water Misters under the floor spraying down to create a wide circle around the hole where the air was being drawn from. I remember a mate who works in Aircon coming over and commenting on the fact I'd got the old broken AC going again then looking up and realising it wasn't. I pointed to the hole in the floor with the fan and told him about the water spray and he was clearly amazed. Said he would not have believed how effective it was till he saw it and then went round the side to check it out in detail. I did for a short time Duct heated air under the house from an oil burner. It was wonderful to have warm floors but typically the setup was a bit too hashed together and some smell came though and I got a bit worried about gasses and fire risk. Done properly it would have been brilliant. By then Life went into meltdown, we decided to move so the setup that I was keen on was never realised. Yeah, this place is on a slab and I don't like it much. The floor in the en suite particularly is just a giant cold radiator in winter and due to yet more full length windows facing west, it's hotter than a sauna in summer. Terrible design this house from that POV really. I did look at electric floor heating to put in the kitchen when we re did that but the cost was ludicrous. If I did every build, which I'd never be brave enough to do having seen the Dramas even tradie friends have gone though, I'd have hydronic underfloor piping put in and oil fire it. Heated floors to me are the ultimate comfort and Luxury. Might be because I only have to walk 3 feet on a cold floor in bare feet and I get the sniffles. What a wimp! Winter is fast coming and I'm still dicking around with a head full of wonderful different heating ideas and little progress with any of them. I was going to go with one of those 5 Kw Diesel caravan heaters and simply put it in a window and use that for supplemental heating when the solar was not keeping up. Doing the maths it's actually cheaper to run than buying power. I wanted to run it on veg oil but looks like they don't take kindly to that and my suggestion of water injection in the intake to a guy that is a bit of a guru on the thing didn't seem to help any like it does in engines when he tested it. I'm not comfortable with buying fuel when Veg is so readily available for free. Made so many of my own monster burners that could heat a warehouse but getting something down to 5 or 10 Kw is much more difficult. Actually probably the more difficult part is building a heat exchanger that will yield decent efficiency. I Might entertain the idea of making some Biodiesel for one of these little Diesel heaters. That should come in at about 1/5th the cost of buying diesel and a 200L batch which would give about 160L of product would probably be about all I'd need for a winter. Wouldn't need to make it the typical fuel grade I used to, Just basically Chemically strip it of all the components that leave ash residue so it burned clean like Diesel. I probably haven't bought any methanol for 10 years now and I'll guarantee the guy I used to get it from isn't in business and probably not even above ground any more. He was a pretty well aged guy then. It was always a Butt puckering experience to see the way he handled the stuff the way he did and I didn't know a single person that had seen him in action that didn't question how he was still alive then. :0) I would also like to co gen one of the diesel engines but making one of them acceptably quiet to locate close enough to the house is going to take some effort and planning. Same as using the spa with an oil burner as a heat reserve and firing that up every few days. I think that could be a winner but still haven't got the damn thing in yet because we keep changing ideas of what we want. Procrastination and indecision is definitely our downfall with home improvements. I'm trying to get the new Circa 30 Kw solar farm up on the roof and see how that goes this winter. At least that meets the requirement many other rushes of blood to the head don't, it's not an eyesore and is practical and something anyone in the house can run. If this place was built 90o either way, I'd definitely be laughing with solar power all year round. |
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| Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1578 |
I was just sitting here stuffing my self on a fantastic roast pork dinner. There are some things my wife is acknowledged by all to cook perfectly and pork is one of them. I could not imagine anything better than what she does. It's perfect and I am a lucky man for being able to enjoy it. Walking past the oversize oven, I noticed the heat coming out the thing and thought that wouldn't be a bad way to heat the place when the temp goes sub zero and the old AC unit freezes up solid. I remember going away once when the Kids were young. We went to these holiday units and the weather was freezing and the heating was limited and very insufficient. The power circuits were very limited but of course the stove/ oven was on it's own circuit. Turned on the oven, fired up the stove elements and the place was nice and cosy. Everyone else staying in the same place was complaining their units were ice boxes too but I told the mrs don't tell too many people what we did or we could overload the building wiring and get no power at all. Couple did come up the day after and thank me for a much more pleasant night using my idea. I still have the old perfectly good oven out on the back verandah. We kept it as an extra for the family Christmas dinner and of course it's still there. I was thinking to pull the elements out of that and put them on a PWM and make an enclosure for a fan. Same token, may as well just buy a fan heater from Kmart for $20 and be done with it. What I really want is to be able to save all the heat The AC Discharges in summer and put it back in the place in winter and save all the cold the thing wastes in winter and use it back in summer. Spose that's another of the holy grails of an impossible perfect scenario. One thing that does puzzle me is why my solar inverter puts out heat I don't believe adds up to its stated efficiency in summer because it is like holding your hand under a fan heater at full tilt but is barely discernable at the same flat out power outputs in Winter? I just don't understand what is in play to allow that and it's definitely not my imagination. |
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| rogerdw Guru Joined: 22/10/2019 Location: AustraliaPosts: 852 |
Sorry, I had to smile at the picture of you chucking one out the back door. I do understand somewhat, they can be a pain. Not sure how seriously to take your last sentence though. That's the difference between you and me. 30 years ago I had the exact same ideas ... but never actually followed through with any of them. Couldn't seem to get the approval and wasn't really committed enough. Our house has floating floors in the bedrooms but tiles everywhere else. Not bad in summer, but in winter they're a bit cold. After our wood fire has been going a few weeks you can really notice the temperature gradient in the floor. If I walk out the bedroom and down the hall the tiles are cold ... but halfway down you can feel a definite warmth which gets better and better the closer you get to the fire. In another thread a year or so ago, I mentioned that the previous owners fitted underfloor electric heating under the tiles but had never connected them up!!! I was keen to try and get enough PV to warm the floor, but with minimal power in winter when it's needed, the general consensus was that I had no show of making it work. There's two circuits requiring 3kW each and for lots of hours per day each (don't remember exactly). The suggestion was that while the underfloor elements were on we would feel the warmth, but as soon as they were turned off the heat went away immediately. My argument was that the slab should eventually have warmed up a little to retain some heat, but was told that would not be the case. I also got that from a supplier of the technology as well ... so figured they must be right ... though my experience of the wood fire warming the tiles after some weeks does make me wonder still. This discussion has me wondering if I could tap off some of the waste heat going up the flue from the heater as well. Probably not practical, but would be nice. Cheers, Roger |
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| Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1578 |
I have my issues and while I try very hard to be rational and calm, I also have a very short fuse with some things and easily explode. Repeated experience with those dryers which my wife seems to love and the frustration they have caused me makes me instantly go into melt down. That is the case with Most of my bright Ideas but this one was very simple, quick and easy to do and cheap. Also Invisible to the Chief of all things domestic so was an easy one to execute.... unlike many others. One I did do last year was construct a small output Draft oil burner that got the seal of approval MUCH to my surprise. While sitting out on the back verandah admiring the thing, The commandant came out, had a look, asked some questions and disappeared. Next thing she is brining out coffee and raisin toast and sitting with me in the winters night enjoying the burner and talking bout where it could be put permanently. That one failed to get installed as with all of those "Simple" draft burners, they never burn really clean and they soot up. forced air burners run perfectly clean but they are hard to do in small outputs. I might try again this year. As someone with a solar obsession, I can confirm the backward nature of solar no matter how oversized an array is. When you want the power most which for me certainly is in winter, it's least available. Not even so much the outright power due to lower isolation, it's the fact the days are half as long that's the real killer. I would have said the same thing. I would have thought even if the majority of the energy was radiating out into the soil on the other side of the slab, that would warm and become a thermal mass itself. I would class dirt as a pretty fair insulator but maybe it has to be dry. I built a couple of furnaces out of ordinary dirt from the garden and they held up pretty well insulation wise. The inside could be glowing past red hot and the outer walls 4" thick took some time to get too hot to touch. I have looked at that many times but it's always said that doing that creates too much soot deposits. I see it in oil burners so I give that idea full credibility. Supposed to be some powders one can put on the fire to add that but the only person I had first hand experience with it still had a coked Chiminey although her burning practices were HIGHLY questionable so I couldn't take anything from the observation one way or the other. I thought about a water injection system like I use on veg fuels engines. The steam would probably keep things clean and the heat loss would be minimal. How do you execute it in a safe, reliable and workable manner though that gets the approval of the Chief operating officer? I have been looking for some time to get an old wood heater and do a test converting that to oil. If it worked how I fully expect it would, I'd install one of those and all me heating and winter power concerns would be over. No way in hell I'm running one on wood though. I wear myself to a frazzle just trying to keep the wood up for my fathers fire and still fall well short. Not trying to do it for myself as well, WAAAY to much work for me to handle. |
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| rogerdw Guru Joined: 22/10/2019 Location: AustraliaPosts: 852 |
I was wondering more about the heat between the flue and the outer heat shield tube. Wind some copper tube to fit tightly around the outside of the flue ... but all inside the shield tube still. Would probably be a bit hard to make happen though seeing it's all been together for a few years already. Perhaps just punch a hole in the outer shield up higher in the ceiling and draw the heat out of that. Put a suction fan of some kind down into the adjacent room ... and let the return air find its way next door and back up inside the shield at ceiling level where it starts ... drawing heat off the flue again. I also kept seeing the ad for all those evacuated tubes ... so I picked up a box of 10 today. Late this arvo I put two on the back lawn propped up at about a 10 degree angle. Ambient temperature was 20 degrees and sun was nice and bright but behind broken clouds. Only took a little while for the temp inside the ends to get to 30 degrees ... and then I left the probe in the end ... effectively blocking it so the heat couldn't get out. It took about 20 mins before the temp was up over 70 degrees C ... and off the scale of my probe. 5.30pm. I found some 10mm diameter, thin walled plastic sleeving and slid down to the bottom and blew into it ... but the restriction of the creased tubing made it hard to get much flow before I ran out of breath. So I blew in air from the air compressor ... and the resulting air was pretty impressive. Couldn't hold my hand in front because it was like a hair dryer. I expected the compressor air to cool the whole thing down pretty quickly ... but it held up remarkably well and took quite a while to start coming down. Took several minutes to drop to 60 degrees ... then another 5 or 6 mins to get to 30 degrees. Pretty hefty airflow though. I had some chores to do and came back at 6.15pm and the tubes were in shadow by then. Ambient was down to 18 degrees. I used the compressor to blow air in again and it came out at 43 degrees. Took 4 minutes of constant flow for it to drop to 35 degrees. And all this out of just one tube. I do kinda wonder what 40 or 50 of these tubes could do laid out on the roof and into a common manifold ... though I suspect it may be difficult to get a good airflow into all of the tubes to harvest the heat. Any airflow or fluid dynamics experts around here?  Cheers, Roger |
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| rogerdw Guru Joined: 22/10/2019 Location: AustraliaPosts: 852 |
Haha, I found a cooking thermometer to use and sat it inside the top end of the tube. Came back in half an hour and it was at 182 degrees C. I might go get some snags to cook for lunch. Who needs a BBQ. Cheers, Roger |
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| Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1578 |
Very interesting Rodger. " but the restriction of the creased tubing made it hard to get much flow before I ran out of breath." Having anything bar smooth wall tubing is a great impediment to flow in any medium be that gas or liquid. Even imperfections like welds and joints can have effects on flow rates same as bends. OTOH, concertina type tubing can break up boundary layer gasses and greatly aid in heat transfer. It should not he hard to make a manifold for the Tubes but if they are able to get to 180 or more, it would have to be metal. Imagine what they could do on a hot summers day! You would probably want to group them in batches of 10 or so in order not to create too much of an airflow restriction. A cheap and very good type of blower I use are the jumping castle type. They do good pressure as well as flow which a fan can't. A scroll type blower out of something like an AC or that Tony uses on his dryer may be a better compromise between flow and pressure. I have been running a lot of calculations on PV heating water for space heating and the numbers just don't add up for me. I can put up a LOT of panels but would still fall way short of the heating power I need. Perhaps the tubes would be more effective? The only drawback I see with this air system is it may be more difficult to store heat for say Night use. If the sun is out here, even in winter it's fine. At Night..... Agggh! Solar is in a bit short supply when one needs it the most. Would be interested to get some sort of comparison as to the heat output for these Tubes so one could calculate their power and relative to that of PV. I would expect Tubes to be significantly more efficient. If you can get 35o out of them in shade, that's brilliant. I have read conflicting reports about these things. Some people say they work in shade, others say they need sun. I think the air heating concept especially with the flue is a good one. Been buying pumps and things to make an oil fired heater for water which I can store heat for night but, It's a whole lot easier and more practical to go straight to air. It would also be a lot easier for heat control. would work for tubes but for combustion one would just blow the amount of air you want for the heat output and vary as needed. and excess could go to waste. It's an inefficient system but as I'll be using free fuel, efficiency isn't the highest concern. A disperser or spreader in the flue gasses to break up the boundary layer would make a big difference but on a wood fire, may be problematic. I see there is a fast Growing interest in the little 5KW diesel RV type heaters being put to use for home heating. Using diesel for the same KWH delivered as what I pay for electricity would be over 2.5X cheaper. If a little efficiency optimisation was employed, the numbers would gain a point or 2 on that. Some say these heaters are not good on waste oils, some have run them multi seasons with no trouble. Many whom are using WMO are not running it straight but blending it with diesel. This makes sense just as it does for engines. My thoughts also based on years of running engines on various blends would bring me back to the one I always Championed and that was not to blend with Diesel but petrol. These little heaters will run on straight petrol somewhat sub standardly but I think having it maybe 10-20% in oil would help burn the deposits well. It is also said the heaters should be run hot. That would be no problem in my case as I have great doubts 5Kw in this place would be near enough heat. For the price of the units, 1 at either end of the house could be Viable though and 10 KW I think would do the trick. Be very interested to see some more R&D on these tubes. |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
If its freezing cold outside, with an evil grey sky, there is not going to be too much heat to tap, no matter what you decide to use. No free lunch unfortunately. The advantage of the evacuated tubes over say coiled black plastic pipe as a heat absorber, is that you can reach much higher temperatures, because the thermal losses back into the environment are much lower at higher temperatures. There is actually no extra heat, in fact black plastic pipe may be overall more heat efficient area for area if you only need low grade heat for say, swimming pool or floor slab heating. Certainly a lot cheaper to install ! If you absolutely need to reach higher temperatures for domestic hot water, the evacuated tubes would be a better choice. With current technology I believe the most energy efficient heating might be with a heat pump. That could be with a solar powered compressor, and the heat source could also be partially from solar, and partly from the outside air as is usual. Cheers, Tony. |
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| rogerdw Guru Joined: 22/10/2019 Location: AustraliaPosts: 852 |
Thanks for the feedback Dave. Yeah the tubing was the first bit of stuff I could find lying around the place to experiment with. I envision some fairly large diameter copper tube to use instead. Big enough to have less restriction ... and also bring the copper closer to where the heat is concentrated ... on the inner surface of the inner tube ... ... though still needs enough space for the return air up the outside. And you're right that it needs to be metal ... the highest temp I saw yesterday was 194 degrees C !!! A guy I saw on youtube has added a spiral system to keep the return air inside longer ... but also says too many turns creates too much restriction, but that it does pick up more heat. https://www.youtube.com/watch?v=qObaltPPohU&t=11s Yeah, that is quite likely. I imagine it will need a decent number of tubes, but the airflow will be the problem if not designed properly I agree. Needs a fan that moves air slowly rather than fast. Half way between a fan and an air compressor supply. I do have one of those jumping castle type blowers, so I can experiment with that if I can get a few tubes together. I do wonder about some method of using the venturi effect to draw the heat out ... but the fact the hot air has to be replaced with cooler air means it has to get in there somehow ... and I can't cut a hole in the bottom or the vacuum is gone! Maybe just needs the right sized pipe partway down into the tube ... and blow air across the top and suck out the hot air ... dunno, will have to research and experiment. That's a pity because it would be so much easier to pipe the heat around ... just choose what electrical appliance you want to use and plug it in. Still, if it doesn't add up ... there must be another way. The only drawback I see with this air system is it may be more difficult to store heat for say Night use. If the sun is out here, even in winter it's fine. At Night..... Agggh! Solar is in a bit short supply when one needs it the most. Yep, back to the same old problem ... though you gave a link to those off peak storage heaters up above I think it was ... and they use something like a 5kW heater (off peak overnight) for 5-6 hours to heat up a heap of bricks in a housing ... and then use a fan to blow out that heat for the rest of the day. ... and that housing is just over a metre wide by 670 high by 280 mm or so deep ... not really very big at all. What if we built a well insulated box outside and filled it with heat bricks, five or ten times bigger ... and plumbed the hot air into the house somehow ... either through the wall or up through the eves. Would also need a return line as well, otherwise would be heating up potentially freezing air from outside to pump back in. I can't add much about the diesel burners, though they do look very interesting ... I just have no experience with them at all. The fact you have a wealth of knowledge and experience with alt fuels gives you a good headstart. If you want more info on the tubes and other opinions ... I came across a 11 year old thread about evac tubes here ... http://offline-forums.ata.org.au/topic.php?id=147 ... and then "Munter" the guy asking the questions eventually built a system in around 2017 ... and showed some pictures here ... http://renovations08.blogspot.com/ Cheers, Roger |
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