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Forum Index : Other Stuff : Anyone do any real form of " alternative" heating or cooling?
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| Solar Mike Guru  Joined: 08/02/2015 Location: New ZealandPosts: 1138 |
Hot air is a pretty hopeless media for transferring heat to any storage mass as its specific heat is so low, you need big fans etc. Water is very good, solar hot water DIY flat panels are 50 - 70% efficient, evac tubes up to 80%, your PV is only 16%. Water is easily stored in a HWC for domestic use, or in a large timber box lined with rubber roof liner. Another option is to dig a large pit outside the house, line with slabs of polystyrene, fill it with 50 tons of sand, layered with 20mm black plastic water pipe, zig zagged across the surface every 30cm depth. Put up some solar hot water heating panels and circulate the water through the sand mass, over the summer it will warm up, on cold days circulate the warmed water back out through a heat exchanger (car radiator + fan) to warm your house, or feed into a hydronic heat pump for under floor heating etc. We will be using a similar setup with the sand under the floor of a green house, during cold mornings etc the heat will naturally flow up into the green house warming it up. Cheers Mike |
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| rogerdw Guru Joined: 22/10/2019 Location: AustraliaPosts: 852 |
Mmmm ... that's a pity. Maybe that's why no one does it that way. Having experienced the hot air heat from just one pipe I was impressed. Can I assume that if enough were combined and we could channel the heat into the house, that it would still be effective as a space heater ... forgetting the idea for the moment of trying to store it for overnight use? Thanks for those numbers, puts things in perspective. I certainly cannot argue with that ... the only reason I was avoiding water in this discussion was that all these evacuated tubes come without the heat pipes and metal heat transfer strips that are needed to extract the heat for a water manifold. Having to buy those makes the whole experiment a lot more expensive and of course a much bigger risk. Now that's something I can understand ... and could possibly do something like that and using a heat exchanger to harvest some heat. Unfortunately we don't have hydronic underfloor heating pipes in the slab ... we have electrical underfloor heating!!! Such a shame PV only scores 16% efficiency!!! Do you have any thoughts about phase change materials. Pumping your heat into PCM and then using that, supposedly allows a COP of up to 3 or so. Of course the PCM is expensive too ... though you can use parafin wax or even coconut oil ... but the quantities required mean that the price is still substantial. Unless you know of any recipes to cook up your own version. I really appreciate your input, thanks Mike. Attached to one of my earlier links are some comments from "Munter" who actually did some experiments on a serious scale. Well worth a read ... plus scroll to bottom for more ... ... then click the left arrow at the very top for more posts ... http://renovations08.blogspot.com/2017/09/the-big-plan-solar-hydronic-heating.html Cheers, Roger |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
Its all been tried before by various governments, universities, and research groups such as the CSIRO, and the Victorian Solar Energy Council where I worked for quite some time as a technical officer. An internet search can turn up a lot of data. Try "rock pile heat storage" and "Trombe wall" All these systems have been expensively built and tested with often very disappointing results. Best results have been passive heating through the direct greenhouse effect, and summer shading with deciduous trees, but you probably need to build a completely new suitably situated house to get the full benefits. The most dramatic failed solar heating project I was personally involved with at the time was the hydronic heating of The Patch Primary School in the Dandenongs Victoria. In the end it was so expensive to run and maintain they ripped it out, and today I believe they use grid powered heat pumps to heat and cool the school. Please excuse my cynicism, but its all a result of years of personal hands on experience on many of these government funded disastrous projects. Edited 2021-03-30 11:52 by Warpspeed Cheers, Tony. |
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| Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1578 |
Same as at night which I am most concerned about. Starting to get cool here in the evenings. I always said here it's fine till about a fortnight after Easter and then the cold hits. Don't give me much time to get organised for this winter. |
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| Solar Mike Guru Joined: 08/02/2015 Location: New ZealandPosts: 1138 |
Govt entities have a habit of spending > $1M on a project and achieve very little, that a group of enterprising workers could get the same job completed for $20K with a few working bee's and Saturday BBQ's. Having visited a new house here in Wgtn many years ago that has a huge bed of sand in an insulated hole under the internal garage slab floor, with pex tubing snaked throughout it heated by 8 sqm roof mounted hot water panels. The main HWC is heated first then any surplus heat is sent into the sand bed, takes most of the summer to warm up and gives a few months of low grade heating during the cooler periods. I agree on the hopelessness of getting any useful instant heating from the sun on a grey winters day, an electric hot water heat pump heating a concrete slab is probably the most efficient, unless you can source free firewood. Mike |
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| Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1578 |
I was thinking about this today a lot from the POV of a tube in tube HE for a burner. With nothing more than mental arithmetic of how to practically build this, just wasn't convinced in my mind I could get enough heat out of it and then worried about smell from hot metal. The advantage is simplicity and heat control in my mind. I was thinking Of maybe a 6" metal duct inner with a 8" over that and a Couple of T pieces on the ends and sealed to the smaller pipe for air in and out. Have a fan pulling air from top to bottom and discharge. All good. But I'd have to insulate The outer tube and then I'd have to seal it as I have no place to put this undercover where I would want a burner going. Needs to be far enough away from the house so it it does burn, I don't care. Then I have to have a large duct taking the hot air into the house. In practical application it gets a bit complex to implement effectively for MY needs. Water leaves every other non exotic material for dead when it comes to thermal storage and heat transfer. The flat panel efficiency is interesting as is the rest of the numbers. Good info! Would you happen to have any numbers as to what a domestic solar hot water heater like the solarhart types put out in KWH? Might be worth setting one up as a ground mount for a bit of thermal storage. This is pretty much an Idea I was very excited about and I think outlined here some time back. I wanted ( and still do) to dig a pit, Line it with black builders plastic, Insulate it with old cool room panel, drop in a couple of IBC's, Cover with more cool room panel, fill with water and heat it with an oil burner. Pump the water through a HE and hot air into the house. LOT of thermal storage there! About 120 Kw. The other thing I thought was this could be used in summer as well. Simply fit an external fan/ radiator and run that a couple of hours Before dawn with a water mister on the radiator to aid in evaporative cooling and you could get the water temp down to 20 C or so. Run the system through the day and get cool air. I'd really like to try this but can't sell the Mrs on the idea. I'm thinking of using the spa we are trying to get organised as the thermal storage instead of the IBC's. Sand and soil have the same heat capacity so if you didn't have the sand and had to buy it, you'd do just as well with the soil you took out of the pit to begin with. If you could line the Pit and keep the sand soil wet, you'd have much better heat capacity. Sand/ soil/ stone has less than 1/5th the heat capacity of water although you can take them higher temps but not too much with plastic tubes running through them. As a rough calculation, if you would put 50o heat rise in the sand/ soil you have a bit under 600 Kwh of heat storage. For heating a home, for my winters, does not seem a lot. If one heated with 3kw/ h for 6 hours a day,that 126 Kwh week So \roughly 5 weeks of heat less losses in the storage Over the time you supply the heat to when you use it through the autumn. If I think of MY AC and what it puts out which is intermittent but more than 5 KWH and my dads wood heater that's probably doing 5kwh non stop for the hours one would actively heat, The 600 KWH from my POV is not going to get too far into the winter. I'd like to hear what others thing they would use and how far 600 Kwh would get them.... assuming you would be able to get a 50O heat rise into the storage in the first place. Might be able to get more which would be helpful> That's why I'm thinking oil over electric. There is 2000Kwh in a 200L drum of waste oil and that's very compact and easy to store. I have more than 3 Drums up there now so If I can do the heat exchange decently, I can have a very warm winter.... and I hate the cold, depresses me. That too was my other idea. Put a greenhouse or at least a veggie garden on the top to make use of the lost heat. I'm thinking of going back to my old ( formerly) gas fired water heater. It's rated at 6 KW input but I might be able to get 10 Kw into it with the oil burner. If I could find a larger scrap one with higher capacity, that would be good. I think 10 KWH would be enough for the heat I need. The benefit of the gas heater is it's already a gas to liquid HE, it's insulated and weather proof as far as the insulation getting wet and being defeated. Also has some storage for the night or early morning. I think this is my best bet for the limited time I have left to get organised. Probably just me but I can't seem to get my head around heating in summer or the warm months to set up in advance. |
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| rogerdw Guru Joined: 22/10/2019 Location: AustraliaPosts: 852 |
Well that is all a little depressing, but thanks anyway. I guess, if it was easy to make work it would have been done years ago ... so I can't see it being any different for me. Ha, I remember that story, what a saga. Glad it wasn't me paying the bills ... or worse, explaining to the higher ups exactly where it all stuffed up. Haha, you're excused. I need a reality check every now and then. Cheers, Roger |
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| rogerdw Guru Joined: 22/10/2019 Location: AustraliaPosts: 852 |
Sounds like you all live in Melbourne.  One of my links a few comments back is to an article by a guy who thought the same about using a heat pump to warm the slab ... then fitted a bigger one ... gave up and pulled it out and went to evacuated tubes. Maybe they've been ditched by now too, dunno. We haven't bought firewood in the five years since we've had our wood fire here because of a wonderful friend who allows us to come over to his property and clean up any of the fallen stuff around the farm. But it's still hard work to collect, cut, store, split ... then feed the fire ... but it is a wonderful warmth and it keeps my wife very happy. I know the grass is always greener on the other side ... but sometimes it would just be nice to flick a switch. Cheers, Roger |
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Haxby Guru Joined: 07/07/2008 Location: AustraliaPosts: 423 |
Thought I'd chime in with my setup here. Also in Melbourne. (Why are so many regulars on this forum in Melbourne?) Generally I think insulation is key, and thermal mass is over rated. If you maximise insulation, you won't need much energy to keep things warm/cool, and thermal mass tends to work against you about 50% of the time anyway so I try to avoid it. I've got a lot of insulation in the walls, roof and under floor. The house has black steel cladding, so it's warm in winter. In summer it gets too hot but with ample solar panels we can run the air con guilt free during the day. The house is all electric. No gas. No wood fire. Resistive storage hot water is on a timer that turns on at 11am. Induction cooktop works great. I was worried I'd miss the gas cooktop but that turned out to be unfounded. We have only had the solar on for a few months so haven't got bills over winter yet, but over this last summer we have been in credit with the electricity provider. In winter I suspect the hot water system will be better off with a smaller heating element so that it gets the most out of the solar panels. It's a 3.6kw element right now and uses about 7 kWh per day. I think a 2.4kw element might be better over winter. Another option would be reverse cycle hot water but I hear they need to run for a long time, can be noisy, and are expensive to buy, so I'd rather not risk it for now. LED lighting is amazing by the way. Those 3w bulbs can light up a whole room. So heating/cooling the house and heating hot water seems to be the lions share of the energy pie chart. |
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| noneyabussiness Guru Joined: 31/07/2017 Location: AustraliaPosts: 512 |
If your referring to a " heat pump " hot water system, the only thing right there is they are expensive... mine is a 250l , pulls about 800w when heating, only for a short period of time ( about 5 hours a day, that can increase when the teenagers stay), and we are a family of 6 ( 4 little ones)... they are completely wrapped with the heating coil so they heat more effectively with less energy ( thermal law still applies) rather than 2-3kw element 6 inches long ( if that makes sense). Not noisy at all, unless there is a problem i would imagine. . I was extremely lucky and got one for 200 bucks!! as its outta case was damaged, but they usually are in the 1000s, but if you can afford DEFINITELY worth it..and bonus in summer if you can, duct the " cold " side into house for extra cooling... I think it works !! |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
I remember the school principal saying, just fix the bloody thing, I don't care how much it costs, I don't want to have cold children. So I did. First I fitted a hot water circulating pump to the 10,000 gallon heat storage tank to pump cold water from the bottom to the top, as the electric booster elements were located one third from the top, and were not capable of heating more than the top third. The heating elements were only supposed to come on at night on off peak power if solar during the day was insufficient to heat the tank, so it was hot in the morning when school started. So I arranged things so the heating elements, all 30Kw would run during the day on full tariff if the tank temperature fell below some fairlyhigh minimum. All that was barely adequate, but it was the best I could do. Anyhow the principal was happy about the improved heating, although the Education Department started to query the $10K+ quarterly electricity bills through mid winter. It gets pretty cold up in the mountains. I let the bureaucrats fight that one out. It was way above my pay grade. But wow, ten grand's worth of Kilowatts, about a hundred dollars a day. Ain't solar heating a wonderful thing !! Heat pumps with a COP of about maybe four ? would be more like twenty five dollars a day. Not sure about the current circumstances there now, this was all about forty years ago. Edited 2021-03-31 09:24 by Warpspeed Cheers, Tony. |
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| ryanm Senior Member  Joined: 25/09/2015 Location: AustraliaPosts: 202 |
https://builditsolar.com/Projects/SpaceHeating/DHWplusSpace/Main.htm This website is chockers with diy/crackpot ideas that people have actually done properly with data logging the results etc. Really interesting read if you're into that sort of thing. |
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| Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1578 |
I don't think the problem with a lot of these things is the idea themselves, it's the fact that when the gubbermint is pay the vested interests make sure they get their cut too. Even a Moron like me can work out what sort of heat input I need, what amount of panels I'll need, how much roof area that takes and see if the sums add up. I think with gubbermint projects, the idea is handed to some private company whom wanting to make the most they can, tend to implement the idea even though blind freddy can see it's going to be a white elephant from a mile off. They could do the sums, go back and say, this isn't going to fly, you owe us $5K or they can go through with it and make $350K and having fulfilled the criteria, not their concern. One has to work out things for their specific conditions. the same thing further north with warmer temps that still required heating and better sunshine may have been a winner but you have to do the sums first for ones individual circumstance. Pretty sure Tony if you were personally asked to look into the viability of it before money was spent you'd say it won't fly but instead they called you in to fix what was already a non viable situation. THAT I think is the problem with a lot of these Gubbermint ideas. People wanting to make what they can and certain entities within the gubbermint wanting to create the PR ops of saying " Look at what we are doing" and not worrying about the merits of it, just the one off PR value. |
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| Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1578 |
I have looked at this and discussed it here and for ME, insulation isn't the answer. The place really is poorly designed in the first place. It's a bit over 20 YO and has insulation but probably the minimum requirement at the time. My problem is 40 odd ( large) windows from what I have been told here and elsewhere is not going to help a lot in summer with heat going to double glazing and that would cost several tens of thousands to do them all as well. Winter may be better but insulation probably wouldn't pay off in the time I have left to live as against paying somewhat higher bills and, offsetting with solar or other heating means. Only option I have is to do the ceiling better. Neighbour had more insulation put over the top of the existing insulation last year and reckons it made a difference but as much as I like the guy, he's terribly prone to exaggeration and mis information although I am sure it did something. I think the slab is like a cold radiator in winter. If I built which is basicly no chance, I would have all the insulation done properly and have the house setup for efficiency. It's a LOT more difficult if not impractical to do it on an existing place though and having done it, would add no extra value to the place either. This is my perspective as well. In summer I make a lot of power so curing the heat problem with AC is cheaper than trying to prevent it with insulation. Winter is the killer. Not nearly enough power for the AC So I'm looking at other alternatives. Not much I can do to keep the heat out in summer although we are looking at an awning on the back half of the house which does not presently have one. I think that would make a difference as it faces west. Would shade the back in summer and give me more space for panels for winter. The winter sun is pretty useless much as people say otherwise. You can also use a cheap PWM controller to turn the element output down. I have one I use for testing and I regularly run a 3.6 Kw water heater off it in summer from a regular power point. I boil the water to use to put on the weeds to kill them. I'm testing a pre heater going into the main tank to run off solar direct as well. I changed all my lighting to LED when bunnings had a clear out couple of years back. Good Phillips globes for $1 ea. Have since spent a bit replacing all the downlights with LED. The place is like an airport runway now. Didn't add any extra lighting, just replaced the 450W bulbs with 11's I think they were and sure made a massive difference to the light levels and the consumption. On the back verandah I replaced 3x 100W bulbs in the coach lights with 4W bulbs and it's brighter out there than it was before. Leds are certainly one of the breakthrough technologies far as I'm concerned but can be a lot better. I saw a review of what I think are called Dubai or Saudi LED's. Apparently the prince there commissioned Phillips to make more efficient lighting. The elements run at lower power but there are more of them and this makes them emit more light for less power. They are 3 or 5X better than what the rest of the world gets. efficent LED |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
Phil, you seem to have a lot of unshaded glass, and the solution to that is the specially treated glass that passes the visible spectrum, but blocks infrared and ultraviolet. From the outside it looks like a mirror, from the inside just like ordinary transparent glass. All the modern high rise city buildings use the stuff, and it works very well at blocking direct solar heat gain. The stuff I messed with a few years back was from memory called "Solarcool" but there are other similar brands out there these days. Just try one room first, buy a cut sheet and use gaffer tape to hold it on to the outside of the existing glass just for testing. I think you will be impressed. I did a small spare bedroom that has an unshaded west facing window with two panes. I fitted solarcool glass to one, and double glazed the other. The double glazing did absolutely nothing for direct solar heat gain in summer. Its more for thermal insulation in very cold climates. So I have now properly fitted solarcool to both panes and the drop in late afternoon summer room temperature was dramatic. Highly recommended !!! https://www.vitroglazings.com/products/reflective-glass/solarcool-glasses/ Edited 2021-03-31 15:33 by Warpspeed Cheers, Tony. |
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| Haxby Guru Joined: 07/07/2008 Location: AustraliaPosts: 423 |
Warp, the large windows down stairs are actually already low emissivity glass. Also double glazed and argon filled. I had the benefit of designing the house before owner building it in 2019, so a lot of thought went into energy efficiency at the planning stage. At my old job I made a demonstration that used two panes of glass with two heat lamps. One pane of glass was regular and the other was low-e. Students could hover their hand over each pane and feel a distinct difference between the two. The difference was remarkable. The new glass coatings make the glass look exactly the same as non-treated glass. No mirror look at all. Actually I lie, if you hold them up right next to each other, you can just see a slight blueish tinge. |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
You are definitely ahead of the game Phil.... But for others here, there is some trick window glass that is well worth the trouble finding out about. Cheers, Tony. |
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| Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1578 |
Does it work for keeping cold out or just heat Tony? Maybe looking at it the other way, If I put it on the inside will it keep the heat in? :0) |
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| Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1578 |
I believe that wood heating is more efficient than anything else including AC. My Dad has a woodfire so I have some experience with it now. It keeps me warm cutting the trees down, I'm hot time I Limb them, wrap the chain round and drag them up the wood shed with the tractor, I'm starting to sweat time I cut all the rounds with the chainsaw and I'm roasting like a Pig splitting and stacking the lumps...... I'm more than warm and the fire is 150M away and isn't even lit! Now that's efficient in anyone's language! I have upped Dads solar so hopefully he'll use a bit more AC this winter. |
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| rogerdw Guru Joined: 22/10/2019 Location: AustraliaPosts: 852 |
Haha, yep ... I've heard that wood warms you five times ... for all the reasons you said. If I didn't get it for free, it may be a different story ... though if I spent the same time fixing stuff (for pay) as I did in the wood process ... I could probably buy twice as much ready cut wood with the proceeds, or just run the AC. Cheers, Roger |
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