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01-31-21, 05:10 AM | #1 |
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Ian's Thermal System
I am a turtle (slow progress) .. because I'm a tinkerer who gets more out of the tinkering itself than the functional finished product .. and because I have soo many tikering projects to compete for my time .. and because I have a day job that eats 2k-3k hours a year.
Soo , I've been tinkering with allot of the pieces of this project for many years .. but it's starting to come together enough that I thought I might start to write up the overall combined system here. DIY Solar thermal collection from less than ideal orientation but sunnier side of house .. and a DIY compost heating pile .. and maybe someday add a DIY geothermal loop. Make use of DIY heatpump system for higher COP and higher dT. DIY thermal storage. DIY PV collection (with small battery backup) to reduce use of grid electricity. |
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01-31-21, 06:42 AM | #2 |
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Compost pile heating.
A fairly good book is "The Compost Powered Water Heater" .. not perfect , but a good place to start. There is roughly the same wh of energy weather the material is burned or composted .. A well made compost pile has a potential for a small thermodynamic efficiency benefit because burning usually leaves allot of heat energy in exhaust gasses going out a hot chimney .. a compost pile can have much less heat 'going up the chimney' .. colder temperature exhaust gases .. but if the compost pile is outside and uninsulated , than allot of the pile's wh of heat it produces / converts .. will get used / lost just to heat the pile itself from those colder outside ambient conditions (lower net efficiency) .. and if you insulate it , you add cost , complexity , etc. It does vary .. leaves vs paper , type of wood , etc .. but a basic average for common composted hydrocarbons is around ~5kwh per kg .. although not all compost kg are those wh containing hydrocarbons .. for example water content is needed for the biology of the compost pile to function , but the kg of water does not bring with it kg of hydrocarbon wh fuel chemical energy. Compost pile is vastly slower than burning (stove or such) .. slower to get up to temperature .. hours to days instead of minutes .. and slower to process the same kg of fuel .. the easiest hydrocarbons break down over days to weeks instead of minutes to hours .. the most resistant hydrocarbons break down over months to years instead of minutes to hours. Condition Complexity .. A stove burn style is fairly simple (in comparison) operating conditions .. fuel that isn't too wet (the drier the better can't be too dry) .. enough oxygen for combustion (if damper turned down it goes slower but doesn't stop entirely) .. start slow (kindling) and build up to a hot fire .. Composting can be either .. less complex , when years are available to process the kg of fuel , or for very large piles .. it will basically happen all by itself (actually difficult to prevent) if given a big enough material in a pile and enough time .. the smaller the pile and the faster one wants the kg to be used the more complex / details kreep in .. what is the moisture content (not too wet, not to dry) , what is the the O2 ratio content , trace nutrients (available nitrogen , etc) , operating temperature (not to hot , not to cold) , etc , etc. I have leaves , junk mail , etc .. every year .. and if needed (free to me) where I work has a hundreds of tons of wood waste they dispose of every year .. about a dozen or so people take some home for their wood stoves , fire pits , etc. Both have a start up cost .. cost to buy and install a wood or pellet stove .. or a cost to buy and install compost pile heating .. it is easier legally to do the compost pile heater .. Here in RI (legally) I would have to pay a licensed pro to install a fire place / wood stove / pellet stove / etc .. and the stove itself has to have been EPA approved .. soo, no DIY home made , or some of the old versions .. etc .. but compost piles do not have such restrictions .. DIY is encouraged .. it can't smoke or catch fire .. but both of those is a failure case to be avoided in design anyway. The time investment for a compost heater is more concentrated .. subjective if that's good or bad .. you spend ~98% of your invested time at the ends .. beginning and end .. A wood stove / pellet stove / etc .. unless you your entire winter heating fuel in some type of automated fuel delivery to stove heating system , you spend __ of your time every day feeding the stove .. the compost pile heater concentrates all that time .. setup time and then end tear down time , but (ideally) doesn't require your time day to day , week to week , etc. Space investment .. The wood / pellet stove itself as a reaction space is compact .. but the chimney also uses space .. __ tons of pellets ... or __ cords of wood also eats space .. total combined space is roughly about the same either way .. compost pile or stove .. but .. the orientation and type of the space is a different mix between them. |
01-31-21, 07:14 AM | #3 |
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1st experiments were just off the shelf compost tumbler style composting.
Didn't work well for me. - - - - - - Smallest Compost heater experiment was small ~4 Gallons in a old ~5 Gallon water bottle , in my basement. pic attached It didn't make enough heat to create a noticable dT from ambient .. but did compost some of the material over a ~6 Months potential heating season. - - - - - - - Then I tried 6 different mixes , each ~40 Gallons in it's own ~55Gallon Drum. Also in my basement .. exhaust gases vented out through old (not in use) natural gas water heater chimney flue. pic attached. video https://youtu.be/dRHOkPpzCaM Better results , but not good enough. logged data graph attached. - - - - - - - - This 2020 winter I started the 3rd test / experiment outside in back yard ~600Gallon total. It's been doing better so far than the 2nd test .. but , there are still some improvements I have planned for a 4th version in the fall/winter of 2021. Pic attached Video https://youtu.be/fpaYgWquZCI Last edited by Daox; 02-01-21 at 04:15 PM.. |
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01-31-21, 09:29 AM | #4 |
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The DIY heat pump approach I've been experimenting with is converting a used mass produced window air conditioning air to air style heat pump unit.
The mass produced effect means they are inexpensive , and even good condition used ones are available for even less $ (craigs list and such). The power use scale is good for my current direction .. It takes about ~5kw of heat to heat my house (~800SqFt living ~600SqFt Basement work shop) on those cold single digit F winter nights .. A Heat pump with a COP of about ~3 means it should be able to do that for about ~1.7kw of electrical input .. of course that's isn't the common outside temp .. Soo the vast majority of the time 95%+ far less than they will be needed .. and future planed insulation upgrades will also further reduce the amount of kw needed. My 1st experiments have been with the smaller ~500w (5-6k BTU) versions. There are lots of videos and such out on the web of people doing similar for gaming CPUs , Brewing (Wine / Beer) , pet enclosures (aquarium , reptile). Although the air / air style system works .. and I could blow the cold air where I want to take heat .. and the hot air where I want to give heat .. after only a little testing I decided I wanted to modify it to run as a liquid / liquid style system instead of air/air. Air/Air is easier , and has the benefit of not needing to worry about frozen water breaking something .. but frost can build up and stop it from working effectively. Water/water has some attractive benefits .. because of the higher specific heat and material density of liquids like water .. more wh of heat can be moved for a given dT .. that is good because the larger the dT the more it tries to leach out into places I don't want it .. ie. heat loss through a insulated pipe , container , etc is a function of size and dT .. to move the same watts of heat with air requires either larger volume containers (larger size = more loss) , and/or higher temperatures of that air (higher dT= more loss). After carefully bending the coils out. I 1st tried the dunk coils (evaporator / condenser) into water bath .. 55 gallon drum .. and it worked .. cold water sinks .. hot water rises .. soo, there was considerable temperature gradient .. which was good for cold side , but bad for hot side. pic attached. Then I scaled the dunk bath down to the size of the coil .. ~5Galon and ~8 Gallon. This reduced the temperature gradient effect .. progress .. from there I could then pump the heated / cooled water where I wanted it to go. pic attached To further improve the heat transfer from coil to working fluid I blocked off the bottom and sides soo that the water had to flow through the exchanger .. a little better. pic attached To further improve the heat transfer from the coil to the working fluid I made a form to go on each side , which will force the water to flow back and forth through the coil (snake like) .. Still tinkering with it .. not 100% done yet. pic attached. video https://youtu.be/HLPhRFaLJXY - - - - - I'm still a little on the fence about the number of heat pumps .. But I am leaning toward 2 systems. One for the inside storage to outside dT harvesting / expelling. One for the inside storage to living space dT harvesting / expelling. Something like the attached diagram. The thermal storage can be regular water (even free rain water) .. the working fluid might be best to be distilled water or such so as to not clog up the heat pump coils .. where it could do bellow freezing (like outside run in winter) , will either need a 'drain back' design .. avoids need for glycol and such .. or , no need to drain back I use Glycol (or such) .. The inside runs will not ever go below freezing , soo that shouldn't be a issue anywhere else. Last edited by Daox; 02-01-21 at 04:17 PM.. |
01-31-21, 09:45 AM | #5 |
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When the house is closed up for a long time the inside air gets 'stale' .. link after months in the winter.
But just opening a window to get 'fresh air' might work .. it also let out allot of heat. When all that is needed is the fresh air .. it is ideal to keep as much of the heat as possible. OEM made heat recovery ventilation (HRV) units do this .. you get fresh air in .. because heat naturally flows from to cold the colder outside air will get warmed up some by the hotter inside air going out. Never 100% efficient .. but something is better than nothing. Of course off the shelf OEM units are expensive .. so this is a DIY version I made out of a piece of fluted (corrugated) polycarbonate sheet. When ~67F inside and ~42F outside ~96% of heat retained. When ~69F inside and ~17F outside ~79% of heat retained. Fabrication Video https://youtu.be/_kJB9LPhZDs Results / Performance: https://youtu.be/fCgf1lCK4qQ Last edited by Daox; 02-01-21 at 04:17 PM.. |
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01-31-21, 10:49 AM | #6 |
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Thermal Storage
One of the ironies (to me) .. is that I spend energy in the summer to get rid of heat .. and I spend more energy in the winter to get heat .. If only I could only spend the energy needed to move it to when I need it. Entropy is a rough .. storing energy as a object of a different temperature is difficult to do for any long period of time .. conventional insulation on water heaters and such do ok in the range of storing for a few hours .. but to get even a few days takes extremely high insulation R values .. never mind trying to store a large % of heat energy for weeks or months. There are a few 'loop holes' .. if the energy is not stored as heat energy .. there are other types of energy storage that do a much better job of low loss over time. Energy stored in chemical bonds can more easily be stored for long periods of time numerous years .. wood , coal , hydrogen , etc .. but the down side is the very low round trip efficiency .. a large % of the original heat energy is lost by the time you have converted it back to heat. Energy could be stored in batteries .. some modern types like LiFePO4 and LTO can have very low .. like under 5% self discharge per year .. and they can have high cycle efficiency ~95% or greater .. but the $/kwh is very expensive to do whole house light heating from them for months at a time. The reversible desecants are a nice option in that sense .. they give off heat when they absorb water , and they absorb heat when they give off water .. they have very high cycle efficiency , and as long as kept dry they can hold that 'potential' energy for years .. there down side is the cost .. $ , weight , and space needed for a given wh amount of energy storage. Gravity can be nice .. that weight up high on the hill retains all it's gravitational potential energy for as many years as it's up there .. and no exotic materials .. but .. the density some in again .. the amount of space and weight needed to store significant (to heat a home with) amounts of energy is rather large and prohibitive. - - - - - - Where I work gets water soluble wood glue by the 55 gallon drum .. Then when it's empty , they throw away the 55 Gallon water tight drum. I wouldn't use them for potable (drinking water) .. and I probably wouldn't even use them fro 'grey' water to shower with , without allot of cleaning ... but for thermal storage .. the quality of the water doesn't really matter. Large amounts of heat for a long period of time will still not be very effective / easy with storing energy as heat .. but at least with something like water .. it's specific heat and density mean a higher amount of wh can be stored in a decent size ... about ~46,000 BTUs can be stored in a single ~55Gallon Drum with 100dT like from 40F to 140F .. that can be used in 1 hour @ 46,000 BTU/hr .. or over 10 hours at ~4,600 BTU / hr. Soo , I'm leaning this way due to the fairly low cost of tinkering with them. Because of the insulation losses , this is expected to be a few hours to at most a few days of thermal buffer storage .. not seasonable storage .. not 100% of my heating or cooling needs. Sense the drums are free to me .. and the water fill them is free to me .. I might splurge and get better insulation .. I'm considering maybe going with something like an ~R70 , 3" thick sandwich shell .. 1" R6 foam + 1" R66 Panasonic Vacuum insulated panel + 1" R6 Foam. The VIP won't be the cheapest option for insulation .. but .. I do like the crazy high R value from such little space .. all said and done to get a similar R value from normal foam board wouldn't end up being much cheaper anyway. https://www.digikey.com/en/products/...4DcCGBjEBdAvkA https://b2b-api.panasonic.eu/file_st...leversion/3247 But , can't puncture or cut them .. they are the size they are .. or maybe I'll try it with just R6 Foam board first , see how it does before splurging. |
02-02-21, 11:39 AM | #7 |
Supreme EcoRenovator
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Chemical energy storage is somewhat less dense than the source. Megajoules per kilogram is the metric. As expected, burning liquified petroleum gas is pretty dense, around 50. Liion batteries come in around 0.8 on the same scale. But you have to have a source to store. And the 2LOT complicates things further, you cannot break even. Rube Goldberg would be proud.
PV solar is so less dense, they had to invent metrics for comparison. The going rate is 25 equivalent watts per square meter. This is with 10% pv panels. Moral of the story is that if you're jimmy carter, you can power a tiny town for the low price of (he doesn't have to tell you) money. In effect, you're replacing a continuous duty burner of a certain size with a PV energy concentrating storage system capable of less service at higher expense. YOLO, it's just money... The best way to use your dehumidifier scale phase change contraption is to integrate it into your window HRV. Put each heat exchanger at the downwind end and reflect the heat outdoors or indoors, depending on the season. 300 CFM per ton of refrigeration, or 10 watts per CFM of heat transfer, is the standard target indoors. This setup beats the above solar concentrating system described above by a factor of COP times ten. All day and all night, without batteries. Off grid? No problem. Just run it off the power inverter. If this post sounds scattered, it is fashioned to reflect this thread. If it were me, I would probably post up 4 or 5 separate topics and keep each topic more focused. A combined system is only as strong as its weakest component. Last edited by jeff5may; 02-02-21 at 12:16 PM.. Reason: Info |
02-02-21, 06:40 PM | #8 | |||||
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Doesn't matter , because LPG is not part of this system.
Feel free to use any units you personally prefer .. calories , kwh , joules , BTUs , ERGs , etc .. etc .. any of them can easily be converted to any other. I don't exclusively use wh .. but it is the main unit of energy I use most often. 0.8 Mj is about ~222wh LiFePO4 and Toshiba SCiB LTO I have are closer to around ~120wh/kg. Better than break even is regularly achieved with any modern heat pump operating over a COP of 1. A heat pump operating at a COP of 3 provides 3 energy units of heat/cooling for every 1 energy unit of electricity input you give it .. what ever unit of energy you like .. wh , joule , ERG , calorie , etc. Quote:
Standard 1 Sun condition is 1000 input light watts per square meter .. a 10% conversion efficient PV panel would output 100watts per square meter .. not the 25w you claimed. The ~10% you sited has not been the 'going rate' for PV for about ~20 years now .. Maybe back in the days of Windows Me O.S. , but a few things have changed/improved in technology in the last ~20 years .. ~18% is the 'going rate' today .. low end systems are ~15% .. average systems ~18% .. high end systems up ~22% .. and top of the line systems up near ~39%. The PV panels I got operate at 20.5% conversion efficiency .. soo, anybody using 20~30 year old ~10% PV doesn't matter to me .. in the 1 square meter area of your example under standard 1 sun conditions these ~20.5% conversion efficiency panels would result in ~205watts. Quote:
To spend less money .. to get a more capable system .. that pollutes less .. and enjoy many entertaining hours of a tinkering project along the way. Quote:
The pump I am using is a larger scale heat pump than a household dehumidifier is. Quote:
Although what you propose would work .. it would not be COP times ten .. aka a COP of 30 .. no , that is impossible from the arrangement you suggest. Oh that's right .. we also have 'ton' as a unit of energy .. aka "freezing or melting of 1 short ton of pure ice at 0 °C in 24 hours" because humans just love using lots of different energy unit terms. Your proposed system will be worse under some conditions. Lower COP Heat pumps get lower COP / efficiency the larger the difference in temperature between the hot side and cold side .. doing as you suggest would result in the system trying and get the most wh of heat to living space when it is the coldest outside temperature .. thus your design would result in a lower net average COP of the heat pump. 300CFM is allot of air flow .. for a ~800sqft with ~10ft tall rooms .. that's an entire house air change 55x every 24hr day .. Far to fast , and too often for me .. a little fresh air is one thing , but I think that is going a bit overboard. In my design the winter night time heat pump doesn't have to work as hard as your design would .. my thermal storage will not be 10F temperature to try and pull heat out of .. thus I will get a higher/better average COP. Quote:
Sometimes .. not always. Some combined systems are more robust than a single non-combined system would have been .. there can be a redundancy in the system design .. or the additional combinations can improve net performance (not be entirely dependent on it to function at all). For example in my system design .. If 1 of the 2 heat pumps fail .. the system will still work (just not as well) .. even if both heat pumps fail .. the system will still work (just not as well) .. even if grid fails .. my system will still work (just not for as long as with grid) .. even if PV fails entirely .. my system will still work (just more from grid than if they do work) .. even if the solar thermal collector fails .. you guessed it .. my system will still work (just not as well) .. etc ... etc. |
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02-06-21, 07:13 AM | #9 |
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Arranging the 55Gallon Drums.
I am a bit torn between two approaches .. But usually leaning toward Option2. Option #1> Space Condensed. Think/image one big block , with everything all together. Or in principle if it were just one large storage tank. Pros: #1> Less total gallons of room space consumed for the same gallons of storage space. #2> Reduces the cost of components .. less material for plumbing when there are all close to each other .. less insulation and frame materials. #3> Because it would also have less surface area, that means it will also retain it's internal temperature better. #4> A little easier to 'sell' the idea of it being an 'appliance' .. If that option is needed/desired. Cons: #1> More difficult to accesses the 'buried' interior pieces should any service/maintenance ever be needed. #2> Space is less available for 'multi-use'. If I go 2 vertical drums high or 3 horizontal high , either way , that's floor the ceiling, no other use for that space. #3> Not as easily modular .. should one ever want to expand or reduce the size of the system. - - - - - - - - - Option #2> Distributed / Modular / Multi-Use approach. Kind of like John's design .. Although his website is down , I'll attach a pic I previous saved of the concept. Pros: #1> More easily modular .. expand or reduce system size as desired. #2> Service & Maintenance access .. each drum unit is more accessible should any service or maintenance be needed. This also allows for more easily bypassed bad modules .. should there ever be some type of service or repair issue with one of the modules , a bypass around that one faulty module is more easy to do .. not only helps with repair or servicing the issue module itself .. but also helps reduce the down time of the whole system while that issue is being serviced. #3> More Multi-Use Space .. Although the gallons/cubic feet / etc of volume of the system is still occupied .. the top of the drums (especially vertical 1drum tall) is still usable as a counter / bench space above it. Cons: #1> More surface area , means more heat loss for the same insulation and same dT. #2> More materials for more surface area , means more total system cost. #3> More total volume from the room will be consumed for the same volume of thermal storage. |
02-07-21, 01:15 PM | #10 |
Supreme EcoRenovator
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I'm repeating common, industry standard, optimistic figures for your benefit. For example, the 25 watts per sqft figure is a well researched average daily value. The sun doesn't shine at 100% when it's up, and it's down every night. I'm not trying to argue whether your specific panels peak out at some heavenly output or not on a cool, cloudless day. I'm just saying that the 25 is what the pros use for sizing utility-scale arrays. If you beat that, hooray, you're doing better than PG&E.
You're singing to the wrong choir regarding engineering and materials science. There are many masters lurking in this place, anxious to see something unique. This stuff has all been done before. It's your journey, amigo. I've personally been flamed and scathed in here for overstating or misrepresentating expectations of contraptions, both real and imaginary. A heat pump isn't a free energy machine. All they do is pump gas in a circle. It's throughput is actually pretty lossy. Why do you think that efficiency numbers have constantly been improving over the years? Improvements in all aspects of design. A fancy compressor used to be a twin single; now it's a hyper heat turbo inverter. Micro channel heat exchangers and shtuff. Speaking of heat pumps, here's my heat pump of the week. Currently on week 2 because I ran out of acetylene. The fresh air knob will become the heat/cool knob. Defrost will be handled by a freebie CNT 05008 board and a couple of 10k ntc thermistors. Last edited by jeff5may; 02-07-21 at 02:25 PM.. |
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