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Forum Index : Solar : Hot water from a different perspective
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yahoo2 Guru  Joined: 05/04/2011 Location: AustraliaPosts: 1166 |
Seeing as Mulver wants to toss ideas around and Madness is thinking about wood heating I thought I would show an Idea I have trialed in preparation for fitting in my own house. The concept comes from Russian masonry heaters, the problem they have in Russia is that if you go on holidays and there is no one home to light the fire, the hot water pipes in the wetback freeze and burst. To get around this problem they have a small resistive heater that slides into an inspection hole in the same chamber as the heat exchanger for the hot water service and they leave it running while they are away. I was thinking to myself that might be handy for those days when we cant decide if it is cold enough to light the heater, we could run this element from a solar diverter and it would heat the mass, the house and hot water service all at the same time then switch to the HWS internal element in the afternoon if the water is not up to temp. I pinched this photo from a YouTube video by Ramunas Lekstutis. Sorry I dont have a link, I have had the video for a long time. There is an oven above the firebox door shown that is also in the same bell chamber as the heat exchanger and the clean-out port that the heating element fits into, so it would be possible to cook at the same time.  These heaters use a bell system to trap the hot air in areas inside the heater and not let it escape up the chimney while at the same time bleeding away cold air to prevent any mixed dilution of the heat. I have seen a Kusnetsov stove in action, in Australia one firing a day would be plenty of heat, they are just off the chain for efficiency and output. Anyway I just wanted to share what I thought was a novel twist rather than the standard badly engineered and poorly placed wetback that I normally see. One that sucks the heat directly out of the fire and makes it smoke and burn poorly. I'm confused, no wait... maybe I'm not... |
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Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
Interesting concept, I am going to be building with rammed earth and a significant benefit is the thermal mass which this stove you have shown uses to a lesser degree also. I was not aware that a wet back was such a bad thing, I will be using a Everhot Combustion Stove initially that already has a wetback. There are only 10 types of people in the world: those who understand binary, and those who don't. |
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| yahoo2 Guru Joined: 05/04/2011 Location: AustraliaPosts: 1166 |
It depends exactly where the wetback is. Wood fires are a two stage process the primary stage is decomposing the wood this needs to be high temperature so heat is best reflected back into the burn chamber with firebrick, the secondary burn is injecting heated air and completely burning the gas, this can happen at a lower temperature so it is the place to fit a heat exchanger. I'm confused, no wait... maybe I'm not... |
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| Georgen Guru Joined: 13/09/2011 Location: AustraliaPosts: 462 |
I noticed that your picture could have been taken from this U-Tube https://www.youtube.com/watch?v=DQaTvP_x7VQ George |
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oztules Guru Joined: 26/07/2007 Location: AustraliaPosts: 1686 |
Mad, I used to burn wood with plenty of oxygen. I since built a mack truck brake drum pot belly stove, and I put grills in the floor of that for air to go in as normal...... Much later on, and 8 inches of ash product in the bottom, there is no way for air to ingress into the pot belly now, ... except for lid on the top. When I built it, I allowed for the lid to slide back and forth to allow a 6mm gap at the hinge area. Now, I mostly don't burn wood, but pyrolyze it instead..... this is turning the organic material into charcoal, same as making charcoal... no oxygen, but the wood still turns for carbon..... also sometime called carbonization.....or thermo-chemical decomposition 200-300C... it is not burning, that requires oxygen. This allows for a single log to sit over night, and by morning it is still there in the exact same shape... but if you poke it, it disintegrates into red hot coal. You get the same pyrolysis and products if you use straight sulphuric acid and no temperature.... or when you burn a cake in the oven.. is a bit like it where you make carbon, without burning with air and setting the cake on fire.... no flames, but charcoal cake non the less. There will always be oxygen or even halogens available for some normal oxidation of the organics, as there are gasses tied up in the wood itself... but mostly it is aerobic in nature. For QLD, it may be worthwhile seeing if your chosen oven has facility for closing off all oxygen...then you get slow but continuous heat output, and spread the 4-5kwh/kg of wood over a longer period to infuse into the wetback. Makes a huge difference to the amount of wood you get through. I changed (re- built) the flue cap, and now it does not get blocked for some reason... don't know why, but have not needed to fiddle with it this year at all. It used to clog up with tar deposit as would be expected, but it does not do so now.... odd really. Still musing.... a combustion oven in QLD........ ..........oztules Village idiot...or... just another hack out of his depth |
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| Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
Hi Oz, When it gets down to 10 degrees occasionally we feel very cold. It is all relative and depends on what you acclimatise to, we can spot the southern tourists a mile off in shorts and t shirts in the middle of winter here. There are other times when it is raining that the stove will be used for cooking and hot water. When the sun is shining and it is warmer the hot water will be heated by solar electrically and the same for cooking. The Everhot Slow Combustion stove is a proven design that works, I will not be bothered to try to modify it. So long as it works I don't care if it could be more efficient or not. We will have an endless supply of wood for our own use just from fallen branches, on top of that there will be the tops of at least 20 huge Blackbutt trees. I intend to build a bandsaw with a 1M X 8M log capacity to mill them for building the house. There is already a fairly new 8M X 22M shed that half of will be home for a few years. The combustion stove is already there along with the hot water system for it, however, the previous owner passed away before installing it. The most efficient stove is a gasifier type similar to the wood chip gasifier I built several years ago. They draw the gas from the wood through hot charcoal and inject preheated air at that point. This breaks the long chain hydrocarbons down to carbon monoxide, methane and hydrogen. The hydrogen is the result of moisture content in the wood reacting with the red hot charcoal, the oxygen attaches to the carbon making carbon monoxide and the hydrogen is left free. This makes very clean burning gas that has virtually no smell and definitely no trace of smoke. This is essential for running an engine off the gas, there are heaters that use this process also and give very high BTU's for the amount of wood used. I am not interested in playing around with that though, free time is in short supply so I will just use the stove that is there. Your heater sounds interesting and something I will keep in mind for the future. PS The slow combustion stove is designed to burn overnight, I am sure others here have the same or similar. There is a grate that the fire sits on and air is drawn up through the grate and ash falls into the ash box below. Air flow can be closed down to virtually nothing as well closing the damper. We used to have the same stove when I was kid, it was the only source of hot water and cooking in the house. The fire was always burning 24/7/365, I remember the hot water system boiling and spitting hot water and steam on the roof of the house. There are only 10 types of people in the world: those who understand binary, and those who don't. |
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| yahoo2 Guru Joined: 05/04/2011 Location: AustraliaPosts: 1166 |
You found it!  Thanks GeorgeI have a couple of other heat manipulation concepts to cover one is for semi on-grid or very large storage heaters and the other is the ultimate redneck, scrapheap challenge setup. Unfortunately I have got a few days of sheep work to get done and I will be beyond the world wide web so it will just have to wait till I get back. I'm confused, no wait... maybe I'm not... |
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Revlac Guru Joined: 31/12/2016 Location: AustraliaPosts: 1022 |
I might be a little off topic but still relevant there is a lot of heat between the ceiling and the tin roof on our house so I just thought i would try and make use of it. Just had an old exhaust fan sitting around 250mm dia and some 300mm PVC pipe, made up a flange bolted it together stuck it up through the manhole in the ceiling with the pvc pipe close to the mid point of the tin roof so we could draw down the maximum heat available. Temp in the house this morning 15 degrees, went out shopping and come back home at 12:00pm turned on the exhaust fan and the air temp coming down was 43 degrees, by 4:00pm temp inside the house was 23 Degrees so time to shut it down, bit too warm. Just an easy way to worm up the house on a sunny day during winter, wont work for everyone but I just thought it might be useful for someone with a small house with a tin roof.  Cheers Aaron Cheers Aaron Off The Grid |
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| Mulver Senior Member  Joined: 27/02/2017 Location: AustraliaPosts: 160 |
Very Nice Yahoo! If i was truly going to be off grid I would certainly consider this style of water heating. My grand parents had a wood boiler for hot water and floor heating 25+ years ago and as a kid I had a blast helping to fill it up and lighting it for the evening/night. They had a big farm and endless supply of wood for one house. |
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| Phil23 Guru Joined: 27/03/2016 Location: AustraliaPosts: 1664 |
Still getting good benefits from the ceiling heat in mid winter here. Around 4 to 5 hours of good heat most days. Mentioned my setup in these older thread. Ceiling Heat. Phil. |
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| yahoo2 Guru Joined: 05/04/2011 Location: AustraliaPosts: 1166 |
I'm back from my little worktime away. Ive got a few sore spots, the sheep were fine with shearing but were not keen about Vitamin B12 injections at all. Second idea I want to talk about is using heat storage and stratification to our advantage. The idea that demonstrates this best is a total redneck solution. A few years ago I spent some time playing with a very simple solar hot water storage system using four 200 liter pickle drums and joining them with pex pipe and uniseals. Uniseals are a simple bulkhead seal that works well with curved surfaces and can be installed from the outside very quickly. The idea is to have solar thermal panels heating the drums in series, the hot water is pumped to the first drum and the coldest water in that drum is stratified to the bottom, removed and placed in the top of the next and so forth down the line. The system is open and pumped so that when the pumping is stopped the water in the solar collectors drains back to the drums to avoid problems with ice and boiling. The neat trick with this is to run the pressure water system into the top of the drums in the reverse direction like a series of heat exchangers starting from the coldest drum first, water that is cooled by this heat exchange drops to the bottom of the drum . This avoids most of the problems we have with storing hot water in a single pressurised tank and gives us a lot more heated water over a longer time period. There are very cheap pump controllers available nowadays that have no trouble running a variable speed pump and looking at multiple temperature sensors to enable this solar system to fill with water at a fixed upper limit of temperature and then shut down.  The insulated box can be built out of polyurethane, SIPS , metal clad polystyrene, Hebel block aerated concrete or whatever. The strange thing is the more look at this, I see so many possibilities, the hardware can be incredibly low cost and infinitely configurable. I'm confused, no wait... maybe I'm not... |
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| yahoo2 Guru Joined: 05/04/2011 Location: AustraliaPosts: 1166 |
One thing folks in country South Australia dont realise when they get their new solar digital meters fitted is that the booster circuit for their j tariff loads is now wired into the single meter. It has its own non adjustable real time clock set for 12pm to 8am (non daylight savings time) So this means at midnight boosters across the state run from 30-45 minutes to 3 -4 hours to heat water up depending on the circumstances then spend the rest of the night "topping up". Depending on the hysteresis of the thermostat and how badly the tank and pipes are insulated this can vary from no top-ups so the water is borderline cold in the morning to few times a night right up to flicking on every few minutes and chewing a massive amount of power. Also with an exposed copper pipe from the storage tank to the shower is usually the longest distance hot water has to travel. The heat loss early in the morning (coldest part of the day) can be enormous particularly if tempering valves are fitted close to the tank. So we can see there is a lot of scope to improve this, people that shower in the evenings might switch the booster off entirely. Those that have a small household or frugal water users might fit a programmable timer and switch their HWS on later in the night, closer to the morning. Others might fit an instantaneous water heater and give the solar tank the flick entirely. Others might fit a second tank to solar preheat the water and a smaller tank with the booster element in it so there is no mixing of cold water when some is used. There is also households with solar panels and a standard electric heater, these places are good candidates for Solar Diverters when there fancy feed in tariffs are finished All these tactics can work depending on the use case. We just have to think about it a little bit. I'm confused, no wait... maybe I'm not... |
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| davef Guru Joined: 14/05/2006 Location: New ZealandPosts: 499 |
Check out the openenergymonitor website for another diverter product. |
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| Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
Unless you are on a subsidised rebate with solar panels to has to be cheaper to heat your water during the day. Here in QLD you can not install an electric only HWS in a new home, also a tempering valve and lagging are mandatory. We have a 300L solar HWS and can go 3 days with no sun before needing to boost it. There are only 10 types of people in the world: those who understand binary, and those who don't. |
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| yahoo2 Guru Joined: 05/04/2011 Location: AustraliaPosts: 1166 |
The two assumptions that have blighted me over the years are, 1. dont assume somebody elses interpretation of the rules is correct 2. When I hear "built to code" alarm bells start going off in my head. When it comes to something like insulation and air leaks, workmanship and attention to detail will beat theoretical R-values by a huge margin every day of the week. Qld Hot water system requirements That is different to some tradie or salesman saying "nobody does it because you miss out on a rebate" or "all HWS in this area must have gas boosters by law" or " I tried it once before and the inspector wanted extra paperwork and I told him to  "The laws were not keeping up with new improvements in heating and favoring less flexible, less efficient and higher maintenance systems. I'm confused, no wait... maybe I'm not... |
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| Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
Thanks for that, I was not aware of the rules changing back. I guess it helps bump up electricity bills to gouge money out of the public. There are only 10 types of people in the world: those who understand binary, and those who don't. |
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| Boppa Guru Joined: 08/11/2016 Location: AustraliaPosts: 814 |
My sister had issues with her solar system recently where (as she usually does) turns the booster off- has always been adequate even in winter for one person with evening showers- just... It was only ever getting warm- not even enough to warrant turning on the cold tap- even in the evenings, so she turned the booster element back on, thinking it was just winter and too cool When I visited, noticed a soggy part of the lawn (by stepping in it and sinking up to my ankle in mud) at the corner of the house, there was a persistent drip from the gutter there- turns out the solar panel on the roof had sprung a leak Sad ending to story, she had a plumber come out and fix it (mob who installed panel only a couple of years ago wouldnt come out to fix it) that cost couple of hundred, and she just got the electric bill- $300 above usual which I expect was totally the fault of the leaking HWS- $500 she wasnt expecting on a system only a few years old, to which she is now rather down on solar as well as it has never really lived up to expectations (mostly due to west facing panel and partial shading during the day by trees to boot) This was a system where the 'must be solar' rule was in place and she was rather upset as she replaced a perfectly good offpeak HWS that had a rusted out tank that was cheap to run with a solar system that has always underperformed and couldnt claim offpeak rates for the booster it struggles with 1 person unless evening showers are the norm, 2 people or more and the booster becomes a must- and thats expensive- So there is a note stuck to the front door "TURN OFF HWS' to remind her to turn the booster off when not required :-( (my personal experience has been actually quite good with them thankfully) |
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| yahoo2 Guru Joined: 05/04/2011 Location: AustraliaPosts: 1166 |
Thanks, looks like I will have to buy a couple of the new emonpi units and check them out to see how easy it is to make them divert power with the latest improvements. Last time I tried with their older stuff I couldn't make it work with net metering. I spent two months trying to get the glitches out and gave up, if I couldn't get it to run at my place with me hovering over it 24/7 I wasn't going to install it on other peoples systems. The old displays worked great as a monitor. I'm confused, no wait... maybe I'm not... |
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| Mulver Senior Member Joined: 27/02/2017 Location: AustraliaPosts: 160 |
This is a good read yahoo https://openenergymonitor.org/forum-archive/node/176.html |
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| yahoo2 Guru Joined: 05/04/2011 Location: AustraliaPosts: 1166 |
Yeah, I remember now that I looked at Robin Emley's PV Router page and put the kit build in the "I will get to that later" category and I forgot. The thing that put me off then was I couldn't get my head around the RF link and how that might link into the open energy monitor dashboard. I have since watched a pair of videos Mikes DIY Powerwall Update 60 - Free Hotwater! - YouTube Mikes DIY Powerwall Update 61 - DIY Part2 Free Hotwater! Power Diverter - YouTube I would like to not data-log via RF but my tinkering is not good enough to get a wifi link working properly just yet. cheers! I'm confused, no wait... maybe I'm not... |
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