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Forum Index : Solar : Deciding if I should build this solar heater
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Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1578 |
I suppose it is only the lost temperature be replaced but I would have assumed my place at least was looking a lot more than a KW or so. If anything it makes my oil heater build more difficult. Getting the brun down to a KW will be most challenging. Maybe just have the thing going at 10 KW and regulate the temp by leaving a door Open! One thing I have been observing and am very surprised with is how even the house seems to be keeping. I was thinking with the oil heater I'd have to still run the ducted fan and that's a KW on it's own. I have been running the fan heater in the office here a bit which is at the other end to the diesel but so far, does not seem to be any cold spots that noticeable at all. May as well run the heater for the KW and get some heat out of it as burn the KW just moving the air around. I just went and replaced some crappy old 180W panels with some new 270W ones. I'm going to have to go change my shirt from the sweat. I don't mind working in the cool provided it's not windy. I hate wind and it makes me crook every single time. I am a bit surprised at how well it is working actually. Not a single complaint from the women of the house, only the odd compliment which is a bit thing. Might be calling it a bit early, seems winter still hasn't truly hit here but the deeper we can go into it and the sooner we can come out of it without having to throw massive amounts of power at keeping comfortable, the happier I am. I am wanting to experiment with the Veg oil because although I had a windfall with the diesel, I'm sure as hell not going to be that lucky too often although I will certainly keep my ear out and even try to chase some up from now on. The veg is virtually limitless and free so If I can run 50%, even if I have to buy diesel it's still making it a lot cheaper and far cheaper for the heat I get than buying power. 30% is a good saving. I have a very clear picture in my mind what 30% of the wood I cut for my father would look like. That's at very least a Cubic meter, probably 1.5. That's a good half days work at least for me. I was out before thinking of the benifits of a heater like yours. Warm day in the sun but still a bit chilly when not working hard. I don't want to use the solar too much because I'm pushing to make half the KWH I did in summer and falling behind even with the diesel and I don't want to run the diesel stupid hours above what I already need it for. They are not meant for what I'm doing with it already so even if the fuel is free the running hours have a cost. |
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rogerdw Guru Joined: 22/10/2019 Location: AustraliaPosts: 852 |
Haha, yeah. I suppose the start up process is a bit fiddly ... you can't just have it turn off for 5 then turn back on again. With electronics it's usually the other way around, okay at low power levels but difficult at high. I had assumed I would use our ducted aircon on fan to distribute the hot air once I have a system on the roof ... but if I could direct the output into just two of the cold spots, I reckon that's all I'd need. Where I have the existing one through the window, it has really helped that end of the house. My wife has mentioned a couple times just how warm it is up there ... so it's making a difference. I'm going to have to go change my shirt from the sweat. I don't mind working in the cool provided it's not windy. I hate wind and it makes me crook every single time. You make it sound so easy just swapping them around. I've got soft in my old age and prefer not to work out in the weather, but do occasionally if I have to. Need to be protected though. That's a big plus. That's a good half days work at least for me. I reckon it's at least that much here. We always seem to get through a lot, though the house is always warm. I did wonder what their life time is likely to be ... especially running every day on high for a few hours. Still, sounds like they're not all that expensive even if you do eventually wear one out. Good point, I didn't even think to mention that, but it is the most important to me as well, so I know which way to head or to give up and try something else. Fair enough, though the ones I bought are surprisingly simple to use. In fact I ordered another couple today. You install a simple program on your PC ... then plug in a datalogger and the program recognises it. You can set the parameters for what you want it to do, eg record temp in C at 1 min intervals ... and it's ready to use. Then on the device you hold down the play button for 5 secs and it starts recording. When you want it to stop, press the pause button for 5 secs. To see the results, make sure program is open on PC and plug it into usb socket. The data automatically downloads, and if you click 'graph', you get a graph of the days data. It's also available as a spreadsheet etc. but the graph tells me all I want to know at the moment. You can select multiple files to display together, which is what I use to display the data, though I add a third line using a graphics program. Won't have to do that once I have another logger. These are the ones I've got. Cheers, Roger |
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Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1578 |
You make it sound so easy just swapping them around. I've got soft in my old age and prefer not to work out in the weather, Weather wasn't bad but it wasn't easy, that's why I was sweating. Took 8 panels down, carried them up the back and put them on a pallet and then bought 7 of the new ones down. Roof was low but I had very little clearance between the edge and the garden wall I built there a few years back. Had to shove them up on my own then hold them from sliding off while I clipped the cables together then screwed them down. They actualy look better than the old yellowed ones with the big Diamonds in the middle and they are putting out more power. The verandah is east west so I might throw another array up on the other side to give better all day charging. Also want to move the couple of panels on the diesel heater battery. They are more south facing than anything and I have room more northerly facing atm so I'll move them round. Just not quite getting the battery up where I want it atm. Since loosing weight I have lost a lot of strength and these panels that didn't bother me handling them 25 at a time are now bit of an effort. Probably need to handle more to build myself back up again. I want to replace what's on the shed which is about 40 odd panels and that's going to be an effort! I did wonder what their life time is likely to be ... especially running every day on high for a few hours. Still, sounds like they're not all that expensive even if you do eventually wear one out. Info on the net seems conflicting. From what I can gather how hard you run them seems a big factor. The Failure point seems the fan. It's really the only moving part and pretty much everything else is serviceable or replaceable. I'm not sure if the fans are. I have noticed though, a complete heater is worth about 5X it's price in spare parts, if not more. There are nearly always alternative ways of doing things. I have seen over and over again particularly with different money/ energy saving ideas, It's often better just to do things the conventional way because the savings in any aspect you want to look at are negligible or don't exist despite the Hype. Take commercial home batteries for instance. People buy them to save money but they cost a lot more than buying power from the grid. That's why I did the calcs on the diesel heater. May have been more exy to buy fuel than power so I needed to know which one was cheaper. Also looked at LPG but that is fractionally more exy than Diesel. Cheapest of course is still solar but I know it's difficult to produce what I need in winter despite the stupid amounts of power I can make in summer. I'm trying to balance the 2 heat inputs so I can use the available solar I have and make up any shortfall with the diesel. Veg heater will be the real answer though. Unlimited free fuel and I can have the place as warm as I want. Trick will be not having it too warm. Might be worth getting a couple to measure as you are, out and inside temps. The house seems to have cooled a fair bit this morning which is unexpected. Mrs had the oven on last night which warmed out there appreciably but it's Cooled off this morning. Might be I went to bed early and turned the thing down sooner. I don't think it's particularly cooler than it has been. 4o Atm so not warm. Really does take a LOT of energy to keep this place warm. |
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rogerdw Guru Joined: 22/10/2019 Location: AustraliaPosts: 852 |
I didn't worry about an update yesterday, though I did keep the data. Today was awesome, so wanted to share the results. Forecast was for fog in the morning, then partly cloudy with a top of 20. I noticed the sun out at 8:15, but didn't want to change the routine and logger charts, so hung off until 9am to turn them on. If the tubes see much sun while the fan is off ... they seem to build up a lot of stored energy ... and once the fan comes on, we get a huge inrush of heat until it is depleted. That is clear in the chart below. Rest of the details are in the image below Cheers, Roger |
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Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
Great stuff Roger. Its going to work a lot better with more tubes too. Cheers, Tony. |
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rogerdw Guru Joined: 22/10/2019 Location: AustraliaPosts: 852 |
Amazing what you can do on your own when you have to. Good job. I haven't lost any weight, but I certainly have lost a lot of strength in the last couple years. I really need to do something about it, if its possible. Maybe some weight training. Sounds like a massive job. Good luck with that. That makes sense. I imagine it would be worth keeping one on hand if they aren't too expensive ... though the parts are where they make their money if the price doesn't stop you buying a new one. Either way they win! Haha, yeah, though this forum is full of people who just wanna do things different ... even if it doesn't save much money or work any better. We're a strange bunch. Yes, they are really handy in showing info you might otherwise miss. eg today I had a fantastic output from the device and for so much longer than previously ... yet when I went to compare the previous highest output temp, expecting new highs ... today wasn't as high as a couple days ago ... yet temps outside were higher and ran longer than the other day. I would really love to have an irradiance meter logging the sun to compare that as well ... coz it's not just temperature that warms up these tubes. Cheers, Roger |
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rogerdw Guru Joined: 22/10/2019 Location: AustraliaPosts: 852 |
Its going to work a lot better with more tubes too. Thanks Tony, I'm getting more confident that this is all worthwhile. In my head I worked out how to put up a system three times the size with 54 tubes ... and if I can get triple todays output on good days ... I'll be looking for ways to throttle it back. The next three days are forecast for the same as today but 1-2 degrees warmer ... so looking forward to seeing high outputs continue. In thinking about summer and having to cover the tubes to stop them getting ridiculously hot for no reason ... I wondered if I could use the hot air through a heat exchanger and use it to heat the pool. Though that would be a little tricky with the exchanger on the roof ... I'd still have to run the pump to get the water up there ... which I do already with the existing solar heater. Pity I didn't start with a water heating system and forego the air heater ... though I suspect I wouldn't have started if that were the case. Still feels a bit tricky. Cheers, Roger |
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Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
It should be possible to just switch it on and off with a room thermostat like any other kind of space heating. The more heat you can gain earlier in the day the better. Its going to make a big difference to the cost of heating, even if on some really gloomy days its not terribly effective. Like your pool pump, it should chug away in the background doing its thing, requiring very little attention. Cheers, Tony. |
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Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1578 |
Putting on Muscle is a Very difficult thing when you get older. My wife has lost a lot of weight and the one thing the Doc has been watching carefully is that she did not loose too much Muscle because she said ( as has been confirmed by others) that putting it back on for her will be near impossible. Went and had lunch with my health Nut mate the other week and his energiser Bunny girlfriend. She has been sick and put on a lot of weight and is loosing it again but he said it will take a long time for her shred the fat and build the muscle back up again. Mind you, she is 60 and before she got sick she would have picked me up by the belt in one hand and my equal size mate in the other and carried up up a flight of stairs like we would have carried a couple of drink bottles. She is bit of a freak not only of nature that one but of incredible will, stamina and determination. Actually it's pretty good because it's a flat roof. Nothing like near as difficult or exhausting as doing the 35o house roof. Yes, it's a fair few panels but once you have them up there, positioning them and connecting them up is no where near the effort, strain and stress ( of not falling off the damn roof) as the house ones. That makes sense. I imagine it would be worth keeping one on hand if they aren't too expensive ... I was just looking at some parts on the web. Glow plug, gaskets and vaporisers. Basic stuff you need for a clean out with the GP just in case. Add in the fuel pump and other things that seem to fail and I was thinking I may as well just buy another unit and the 10 gaskets for $10 and be done with it. As you say, in event of a failure, just swap the thing out and repair it without a rush. Haha, yeah, though this forum is full of people who just wanna do things different ... even if it doesn't save much money or work any better. We're a strange bunch. Maybe but no other group I rather be with when the unspeakable smelly stuff hits the rotational air moving apparatus. I think of that with my 2 good Friends. Both certified Geniuses and very hands on problem solvers. Between the 3 of us there isn't a lot we couldn't fabricobble together to survive comfortably. I know the low end stuff that is beneath them but would fill in some gaps. I would really love to have an irradiance meter logging the sun to compare that as well ... coz it's not just temperature that warms up these tubes. An irradiance meter just sounds like a solar cell that has a small load and a data logger for the output to me. :0) Edited 2021-05-19 01:46 by Davo99 |
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Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1578 |
Don't waste energy! Just open a window at the far end of the house!! :0) In thinking about summer and having to cover the tubes to stop them getting ridiculously hot for no reason ... I wondered if I could use the hot air through a heat exchanger and use it to heat the pool. Though that would be a little tricky with the exchanger on the roof ... You know a car heater core would take all the heat those tubes could dish out about 10x over? Motorbike radiator the same. They are air to liquid HE's and the amount of thermal energy they can sink is huge. You could not need a very big he at all and no reason you couldn't bring the hot air down and put it through the HE. I think if the water is in a Circuit, coming down and going up, the energy required will not be a lot. If the HE is down on the ground, same thing. I know a lot of those solar water heaters use Circ pumps which have virtually no head because the weight of the water coming down is the same as going up so really all they need to do is overcome frictional and any restrictive losses. Did you read ANYTHING we wrote at the start..... or several times over?? :0) I thought what you did was going to be tricky but you managed that with seemingly little trouble. Still convinced that you would not need an in/ out with water. The way I see it, as long as the open end is up, the heat will rise one way or the other. Has to. If it's stagnant in the bottom of the tubes it will get to boiling point. when it does that a gas bubble will rise and then be condensed by the sub boiling temp water and give up it's energy. That and probably stir the fluid in the tube and allow the water liquid to rise back up. Other thing I see is thermosyphoning within the tube. Hot water will rise to the top along the length of the tube drawing colder water in and the hot water will stick to the top of the tube and flow out. I think a steady water flow across the top of the tubes and it would sort itself out. |
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rogerdw Guru Joined: 22/10/2019 Location: AustraliaPosts: 852 |
The more heat you can gain earlier in the day the better. Its going to make a big difference to the cost of heating, even if on some really gloomy days its not terribly effective. Like your pool pump, it should chug away in the background doing its thing, requiring very little attention. Yes, it should be quite controllable and I can either keep it really simple or try and build some sort of intelligent control with variable speed fan. That wouldn't be needed on the brighter warmer days, probably only to get the most out of the gloomy days. My wife has lost a lot of weight and the one thing the Doc has been watching carefully is that she did not loose too much Muscle because she said ( as has been confirmed by others) that putting it back on for her will be near impossible. While we're fit and healthy it doesn't seem to matter too much ... but if ill health kicks in it can take a real toll. And aging just seems to creep up on you. Glad you've got it worked out. I'm a bit nervous about mounting panels on my shed roof. It's pretty high and a reasonable slope, plus I've never fitted panels on a roof before, so need to get confident about doing it. Yes, it doesn't feel right having to throw away a complete unit for want of a couple parts ... but when those parts are almost the cost of a new unit, it virtually forces you to replace it. Yep ... never ceases to amaze me how little most people know or understand about practical things ... and we wonder why they talk so much crap about everything else. A lot of them don't have any clue about non practical things either. I did wonder exactly how I could measure irradiance (cheaply) and a solar cell did come to mind ... I'd just need to buy a datalogging multimeter as well. Datalogging irradiance meters are all over $300 and I kinda baulked at spending that much. Temp meters can be used in lots of applications, so I justified those to myself ... especially seeing they are only $30 something each. I suppose ... that would definitely work. Great idea, never thought about one of those. Hopefully by then I'll have finished my Warpinverter and have a roof full of panels so running the pump wont be so expensive. Haha, yeah good point. Though I'm sure there must be some deep seated childhood issue lurking around there somewhere in regards to leaking pipes or flooded houses. That's my excuse anyway. Thanks. I find that if I can think through and understand a complete process of building something ... then I have a chance ... but once there's a part that I don't know how to do ... or feels too difficult for my skills level, I come to a screaming halt. You are exactly right. It was only half way through this project that I realised that some systems did actually use "water in pipe" systems. I thought that they all used heat pipes. I also discovered there's a third method, having a copper tube carry water into and then back out of the evac tubes to pick up the heat. A really tight 180 degree bend at the bottom of each tube. I had considered that for a while to start with, but the quantity of copper tube I would need was going to cost a fortune ... and on an unproven idea I wasn't going to risk it. Of course I later discovered it was a method used for real ... though couldn't find any data as to the efficiency compared to the other methods. Cheers, Roger |
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Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
Water in a pipe can be a real problem if you are in a frost prone area. Boiling in summer can be pretty interesting as well. For what you are hoping to achieve, I think just a direct air heating system is definitely the simplest, lowest cost, and least trouble prone solution. Cheers, Tony. |
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Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1578 |
Forgive my ignorance but can frost only be at ground level and not higher up on a roof? I imagine if the temp is zero it's zero but I don't know much about frost. We sure get it here and sub zero temps and I was looking to put fans in on my garden to try and keep some of the more seasonal Veggies alive but looking it up I was unsure if moving air stopped frost or the fans they use in orchards brought down warmer air from above Ground level. Built a veg oil heater to blow some warm air around but it seemed better just to let the thing radiate. was going to put some tube on the sides and blow warm air along the ground but Mrs wanted to reclaim garden to pave it so never got that far. I imagine the amount of water would be significant but I wonder what amount of alcohol would be needed to meet the lowest temps Rogers area saw? 20L of Metho or Methanol isn't that expensive. Other thing is if just turning the pump on when the temp hit say 2 o to keep the water circulating may stop freezing to a point at least. I believe that's what they do in parts of the US and Europe. Water is always circulated through the mains and has a return to stop in freezing when stagnant. In any case the water at night would have some temp left in it and the tubes are not going to radiate anything only the plumbing and if that was insulated.... Should get through the night OK. would want to get to at least 20 in the day before the heating for the home came in so would have that reserve for the next night. Good point and may be the bigger danger. Alcohol in the system would lower the boiling point as well. I wonder if the system was drained and left open if the water boiling off in the tubes would be a big deal? May be quite gradual. as the weather warms up the water may boil off gradually in the spring so once the real hot days come, the tubes are already empty. Blowing some gentle air through the pipes may help drive off the water slowly. OTOH, if an ammonia solution was used, the steam could be used in a refrigeration cycle for cooling! :0) True but then the versatility/ benefit factor comes into play. If the system can be used to heat the pool after the house heating is done, the cost and effort factor I would deem to be amortised through it's extended utilisation. |
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Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
Frost is a very big problem with solar water heating, both pumped systems and thermosyphon systems. There are two methods used to overcome it. A pumped system can briefly run the pump if solar panel temperature drops to within a very few degrees of zero. That circulates hot water through the panel, just enough to prevent it from freezing. Thermosiphon systems can have a frost protection valve at the lowest point. That opens and dribbles water out of the system, drawing in hot water into the top of the panels, which again keeps the panels just above freezing temperatures. Swimming pool heaters using black plastic pipe it does not matter if it freezes. The plastic pipe just expands a bit to accommodate the ice. Copper pipe must be used for domestic hot water heating panels because of the much higher temperatures, and maybe even have to withstand full mains hot water pressure, may split if the pipes freeze. They are both problems you would be better off without. Much less to fail or go wrong. You could always direct hot air (from a second air blower) to a ground mounted heat exchanger fitted into your pool pump circulating loop. Cheers, Tony. |
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Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1578 |
Glad you've got it worked out. I'm a bit nervous about mounting panels on my shed roof. It's pretty high and a reasonable slope, plus I've never fitted panels on a roof before, so need to get confident about doing it. I procrastinated and thought about doing the house roof for literally 6 Months or more. I was thinking of using cherry pickers and brick elevators and all sorts of things and it seemed a real Dilemma. I started getting up there to make measurements etc and then someone said get those Dunlop Volley tennis shoes because they grip well. And they certainly Do! Mrs even calls them my solar shoes. Only time I wear them. I got up there a couple of times and just sat up there admiring the view. I remember one afternoon I was up there and the neighbour and his Grandson cam out and were playing with a helium Balloon on a long string. I sat up there for over an hour watching them and just enjoying the peace and calm. Neighbour said later I looked very comfortable up there. I said it was very nice and a simple pleasure I thoroughly enjoyed. I was going to get a mates safety harness but the day came I wanted to put the things up and he had it on site so I got some Unistrut, welded the door striker from a car on it and got on the roof ridge, unscrewed 4 Bolts, put the uni strut there and screwed it down. I had got some thick rope and made an abseiling type rig that went through my crotch and around my waist and that was it. I was pretty confident in any case if I did fall, All I had to do was land feet first because it's about 3 feet at very best between the height of the roof and the height of me and less if I'm tearing the guttering off on the way down! Long as I didn't land on my head and crack the Pavers, all good. In the end, it was a complete walk in the park and 100X easier than I had imagined in my worries. I was doing the BIG 420W panels as well so I started with the hardest panels I'd ever done but I didn't have one slip, mishap or single close call. Yeah, took my time, thought my moves through and looked for potential problems and what would happen but it was just a non event which I was happy for. Looked a HELL of a lot harder from the ground that it did once I was up there. I put a short novel about it here: Panel install Re done the array in the first pic on the back of the house now 3 times and haven't bothered with the rope sice the first time nor had any concerns. Put on my solar shoes and sunglasses and I'm good to go. Only safety concern I have is that my daughter when helping me does not stand under where I'm working. If I slip and a Panel ( or I) come down, will come down fast and I couldn't give a flying about a wrecked panel ( or me that much) but she is another matter. Long as she is clear, all good. Yes, it doesn't feel right having to throw away a complete unit for want of a couple parts ... but when those parts are almost the cost of a new unit, it virtually forces you to replace it. No, it never feels right to me to throw thing away that could be repaired but that's probably why I have so much damn crap around the place. I'm trying to fight a loosing battle against things that are purposefully designed to be disposable. I got stuff up there that is just badly or cheaply made I have repaired many times over the years. Under rated components that are impossible to upgrade but not hard to swap every few years and when you know why something has stopped the repair is even easier. Yep ... never ceases to amaze me how little most people know or understand about practical things ... and we wonder why they talk so much crap about everything else. A lot of them don't have any clue about non practical things either. Oh don't even get me started. Like that other place we know of infected by a 99% population of people that I think are hard pressed to tie their shoelaces and probably get the person in the shop to thread them initially when they buy them. I get it some people have their knowledge in other non practical areas and that's fair enough. Some people are just completely inept and have no skills in anything at all though. They always blame the government for not doing enough when they are hard pressed to change a light bulb themselves. Don't know it would give you anything more than an indication but what about replacing the temp sensor with an LED or 3 to give an input based on the light levels it sees? Would tell you when it was brighter and darker at least. With what you said before about getting more power on not so bright a day, Welcome to the world of Solar! Seen this so many times with my Pv. Kinda hazy day then a bright clear perfect day and you make less power. Matter of fact, I prefer a few clouds than none at all, long as they don't block the sun. I don't know what wavelengths panels work on, never looked it up, but it's sure as heck not just the visible spectrum alone, that I can say for sure. Probably their sensitivity spans into the UV and IR ranges as well and the Tubes are probably similar. What we see is only a tiny part of the magnetic spectrum so more than possible when the Visible spectrum goes down the other wavelengths go up depending what part of the spectrum they are in and what the panels/ tubes are sensitive to. Being black, they probably have a pretty wide range actually. Just like your phone can see the IR emitted from security camera's but your eye can't. Great idea, never thought about one of those. They are compact and will sink a lot of energy. Even a decent cabin heater core can pull 20KW and I'd say that's on the bottom end of the range. Get one out of a Mercedes or BMW or other Euro " 6 months of snow on the ground at home" built vehicle and Id guarantee they will do 50kw from my experience. There are Liquid to air HE's on fleabay etc as well all set up with fans and some have thermo control's as well. All you do is connect them to power and a hot water supply....or cold if you have a Chiller. Hopefully by then I'll have finished my Warpinverter and have a roof full of panels so running the pump wont be so expensive. Circ pump I just bought has 3 settings from 60 to 120W and will do up to 6M head so plenty of lift and would need about a kilo of power a day unlike my ducted fan doing a tad over kilo an Hour! It's a fair one. To overcome it have all the plumbing outside and just have the warm air coming in the house. That's the way I intend to appease my similar concerns. Thanks. I find that if I can think through and understand a complete process of building something ... then I have a chance ... but once there's a part that I don't know how to do ... or feels too difficult for my skills level, I come to a screaming halt. Yes, I am similar. I have to have a pretty clear idea of how I am going to go about a task and what parts I' going to use to do it before starting. Not to say I don't get into it and then say "Oh ohh!!" a lot of times but.... My pet and repeated infuriation is planning plumbing and thinking I'll use this piece here and that there and drawing up a list of what you need then going to get them and no one around has that one fitting you need. You then need to completely re design the lay out in your head in the shop with an additional 17 pricy fittings to compensate for the one that every vulture has sold out of. Ugggh! You are exactly right. It was only half way through this project that I realised that some systems did actually use "water in pipe" systems. There you go. I thought they all had the heat tubes as well but 00% opf my knowledge of the things come from this thread. Just the same, couldn't see why they wouldn't work reasonably well at least just letting the heat bleed off as long as the water is moving. Actually, if the design was a non pressure design and the HE was at the top of the manifolds which had a slight rise to the top like a gentle Inverted V shape, the heat would thermo syphon and probably wouldn't need circulation at all.... Much like one of those heat tubes work. Seems to me that would still be basically an air to liquid system if the tubes are not liquid filled. Also seems that would leave a lot of heat on the table in the tube but maybe not. Don't even see why one would need the return line? Have a manifold with even 1/4" down pipes going to the bottom of the tubes and let the hot water flow out into the main manifold. One could run into the other and any thermal transmission between each side would be irrelevant because it would all end up in the same place anyway. If the tubes in a single manifold with water going by is going to work, why go to any more effort and significant trouble and expense? |
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Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1578 |
That circulates hot water through the panel, just enough to prevent it from freezing. Was just thinking... with these Tubes being evacuated, I'd expect them to be the last things to freeze. They are little thermos flasks after all and that's their whole claim to fame, no heat loss. The danger to me would seem to actually be in the piping to and from the tubes. They wouldn't be hard to insulate so may not take much heat in the system at all to keep it out of danger with the occasional circulation depending on the temperatures experienced and for how long where they are installed. Might only drop to freezing for a few hours like here and not be enough time to freeze them up. I remember 2 winters ago fetching the mop bucket outside at 11Am and it still had an inch of ice on the top. |
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Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
The vacuum only really slows down conducted heat. Radiated heat will go straight through a vacuum. The suns radient heat gets here without any trouble at all through 186 million miles of vacuum. An inch of vacuum will do nothing to prevent your black surface becoming very cold indeed at night. It depends what it can "see". Relatively warm cloud overhead, or the sunless terrible cold of deep space. A black surface exposed to the near absolute zero of space on a cloudless night will radiate all its heat very readily. Frosty nights are always clear nights. Cloud blocks thermal radiation. Cloudy days are usually cool, but at night the clouds prevent the extreme heat loss you will get with a clear starry night sky. Edited 2021-05-19 16:03 by Warpspeed Cheers, Tony. |
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rogerdw Guru Joined: 22/10/2019 Location: AustraliaPosts: 852 |
Boiling in summer can be pretty interesting as well. For what you are hoping to achieve, I think just a direct air heating system is definitely the simplest, lowest cost, and least trouble prone solution. Yep, I like simple, low cost and least trouble. I can always aim higher later on once this is finished and my inverter project is up and running. Thanks for the advice there, I'll have to look out for some. When we had the workshop built here and gutters put on the shed, the builders used a couple of scissor lifts. They were awesome. I took the opportunity over the weekends to use one to change all the fluros inside the shed, because I have no way of getting to them otherwise. Shed's too high. I'll definitely be using something to help prevent disaster. I do know where a safety harness is, I might see if I can borrow that. The roof is high, gutters are at 14 feet. Awesome, I hope I can say that when I'm finished. I enjoyed your short novel and do recall reading it before. Great job. Sounds like my place. But then I invite people to drop off stuff to be fixed. That's my job. That's an interesting idea. Had certainly not thought of that. I had thought about buying a datalogger multimeter and jerryrig some sort of light meter to feed into it ... but the ones I found on ebay have to come from China, so potential big delay. Haha, yep. I already had noticed something similar with the pool pump really zinging along on days where I expected it to struggle ... but being quite mediocre on bright sunny days. Never seemed right. Yes, that's what I'd have to do for peace of mind. I'll still have plenty of tubes to play with, so maybe aim for water with the next lot. Cheers, Roger |
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Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1578 |
Wouldn't want to bounce off the ground from there. I think the big thing is the angle of the roof. Steepest pitch on the shed is 8o . it's nothing. Most is 5o so even less. The house is 35 and there is no walking round on that. Need a hand hold of some kind at all times. The roof battens are 1M apart. I take the roof screws out, out in a solar bracket and then can hold myself or use them as a foot hold. I started with a panel along the lowest line of screws near the gutter. Pushed that up from the ladder and screwed it down. Then got on the roof and used the panel as a foot hold. Pulled the next panel up, manoeuvred that into position and Daughter screwed that down. Once the lower row was done I could walk along those ( pretty much laying sideways on the roof) and used a strap with a hook my Daughter connected to the lip of the panel and dragged it up over the gutter, across the lower panels and into position. It was not elegant or graceful but it works and now we have done it so many times don't even think about it. If your roof is less steep the Job will be exponentially easier. From what I understand a lot of homes are built with 22o roofs. That would be nice! Must have been expecting snow round here to make mine so steep! Might be as simple as connecting some LEDS to a datalogging Multimeter. The LEDS will generate a current when exposed to light so all you need is a way to record the input. [QUOTE I'll still have plenty of tubes to play with, so maybe aim for water with the next lot. Might be interesting to set up half a dozen to test as water heaters. Could use the pool as the reserve and tap off from the pump to circulate the water. wouldn't need much flow. Wouldn't change the pool temp but you could easy put a temp sensor in each end and measure the in / out temps. |
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Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1578 |
Radiated heat will go straight through a vacuum. Very enlightening. I am certainly learning a lot from this thread. Thanks Tony. :0) |
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