20 ms·
Off-Grid, Solar-Powered, Zero-Battery Refrigerator
- ColanR 7y agoFor actual historical temperature data, see here. [1] It looks like a general range of 5-9 C is the norm, with 12, 15, and 30 C (53, 59, 86 F) spikes over the last 2 months of data. For that kind of failure rate, I wouldn't depend on it without some failsafe warnings for when the temp had dropped below safe levels. Neat project though, and I might build one if the reliability improves. [1] http://house.joeyh.name/historical.html http://house.joeyh.name/historical.html
- joeyh 7y agoAny sharp spike on that graph is a bad sensor read; the 1wire protocol has a pretty weak checksum and you can get bad data that crcs ok when you're reading lots of data. That covers the 30C, 15C. The spikes to 12C or so that then slowly drop back down are generally the fridge being filled with groceries and taking time to cool back down. If you measured your conventional fridge you might see similar events. I did have the arm board hang twice this summer. Once I was on vacation, luckily it froze with the fridge turned off (so it didn't freeze down to -5C which is where the dumb thermostat is set), and the fridge was fine for the 24 hours or so until I got home, creeping up to maybe 10C. I need to find a more reliable embedded computer.
- kwhitefoot 7y ago3000 lines of control software? Seems a bit excessive. Why does it need a computer at all?
- Scoundreller 7y agoSeems like it's a chest freezer used as a fridge, so there needs to be some set point adjustments. And depending on what's being stored, aggressive thermal banking (if you blow -5C air at your carton of milk, it's not going to freeze for a while, so do it anyway).
- icebraining 7y agoThe solar panels are shared between the fridge and some batteries. His house computer is connected to the charge controller of the panels, to the fridge AC inverter and to thermometers inside and outside the fridge to decide whether to turn on the AC inverter. It also generates graphs of the temperatures, running times, etc. And it warns him if the fridge temperature gets too low. That said, I think the 3k lines include adapters for talking to the sensors, etc. The algorithm itself is about 250 lines: https://git.joeyh.name/index.cgi/joey/house.git/tree/src https://git.joeyh.name/index.cgi/joey/house.git/tree/src
- munk-a 7y agoAh, that's reassuring, I'm rather afraid of anybody who brags about how many LoC their thing is - ideally it is somewhere near the lowest reasonable LoC to get a thing done cleanly and expressively. Oh, also, Haskell - nice going fridge fellow.
- icebraining 7y agoYeah, he's also the guy who created git-annex, one of the most useful Haskell programs ever, in my opinion.
- segfaultbuserr 7y agoUpvoted. I can understand downvoting heated expressions, but I don't understand why a sincere question can be downvoted.
- quickthrower2 7y ago> I don't understand why a sincere question can be downvoted. Perhaps because it comes off like a criticism not a question.
- quickthrower2 7y agoEdit: there is a terminology for this: https://rationalwiki.org/wiki/Just_asking_questions https://rationalwiki.org/wiki/Just_asking_questions
- segfaultbuserr 7y agoYes, it's a technique to argue in bad faith and to shift the burden of proof. And let's see how it applies here... > 3000 lines of control software? Seems a bit excessive. Why does it need a computer at all? It really means, > 3000 lines of control software is unbelievable. It's excessive, it doesn't even need a computer at all! Sure, it's criticism. But I don't see any bad faith argument here. So I guess "Just asking questions" doesn't apply here. And from the Guideline, > Please don't post shallow dismissals, especially of other people's work. A good critical comment teaches us something. So it's probably the reason for downvoting. But consider the fact that other readers have already responded to the question/criticism with more information on the author's intention, I think downvoting this is unnecessary.
- kwhitefoot 7y agoAt risk of causing further dancing on the head of a pin style argument I'd like to point out that contrary to what some people seem to believe it was a sincere question based on my own experience of writing similar control software in an industrial context. I meant exactly what I said, there was no subtext. I wanted to know the answer and it was provided by icebraining. If I had intended to say that the number of lines were in actual fact excessive I would have omitted the word seems.
- everybodyknows 7y agoDiscussion in 2018: https://news.ycombinator.com/item?id=18770213 https://news.ycombinator.com/item?id=18770213
- abraae 7y agoThese "minimal battery" concepts are great. They are the sort of thing that would be fantastic (and maintainable) in the event of a grid apocalypse. A similar one would be a hot water cylinder that only heats up when the sun is shining. And maybe something that fills scuba bottles to store electricity as compressed air. etc.
- sandworm101 7y agoGreat ideas if you are dead against batteries, but there are massive downsides. Batteries are not evil or expensive, at least if you go with traditional lead-acid ones. They are a thousand times more reliable and efficient than compressed air storage. Compressed air storage has many dangers, from explosions (metal fatigue) to fire (compressing gas creates heat). The best and most reliable method of non-battery storage of energy is the traditional water tower. It used to be standard practice for buildings to maintain water storage tanks on their roofs. Mate a water tank with some solar panels and you can create an energy storage system without heat, high pressures, chemicals, high voltage or even moving parts (the pump has only one moving part).
- adrianN 7y agoLead-acid batteries die after only a few hundred cycles.
- mgiampapa 7y agoNo they don't. Case in point, I live off grid with a 24v system composed of 2v lead acid marine batteries. They were 2 years old when I got them and have put them through over 1000 days of use since. Mind you, I don't discharge the system past 23.5v ever, and I check my electrolyte levels weekly adding distilled water as needed, but lead acid are cheap, effective, long lasting, and recyclable with minimal effort. The only thing against them is maintenance, and they are big and heavy. My house doesn't seem to care.
- ledauphin 7y ago
- Baeocystin 7y agoI wonder if, for the stated design goal of a zero-battery solution, something like a solar thermal concentrator + Einstein–Szilard refrigerator would work. Something as simple as an icyball or two kept charged via the solar thermal system might work as well. https://en.wikipedia.org/wiki/Einstein_refrigerator https://en.wikipedia.org/wiki/Einstein_refrigerator https://en.wikipedia.org/wiki/Icyball https://en.wikipedia.org/wiki/Icyball
- abdullahkhalids 7y agoPeople have tried with a regular heat source. But a solar concentrator could work .https://en.wikipedia.org/wiki/Vaccine_cooler https://en.wikipedia.org/wiki/Vaccine_cooler
- newguy1234 7y agoThis is a really great idea. It almost reminds me of AC systems that work by freezing water using solar energy.
- beefield 7y agoHere is at least one example: https://www.ice-energy.com/ https://www.ice-energy.com/ For AC applications, though, water is not the perfect heat storage medium. The efficiency would be better if the freezing point was higher. But then again, I do not know of any material with melting point at +10 celsius, heat capacity close to water and yet, would be having a reasonable cost compared to water.
- wallace_f 7y agoThis would combine well with another low-tech battery solution, stacked weight, which would store without loss or reliability worries for those few days in the year you need them. Edit: Actually, while this idea sounds good, a fridge requiring 1 million joules for a rainy day would need 10,000kg @ 10 meters, even before considering efficiency losses.
- jeffrallen 7y agoVaccines are transported in a cold chain from the manufacturer all the way out to the last village on the end of tracks so poor only motorcycles can ride on them. The last part of that cold chain is off grid, using solar, diesel generators, ice packs, and kerosene fridges. The first rule of operating an off grid cold chain is to always, always, always keep the freezer full to the top with ice packs. The ice packs will of course be needed to pack coolers to distribute the vaccines, but they are also your backup system. A freezer filled to the brim with ice packs will be able to bridge a 3 or 4 day interruption in fuel (or failed generator, or burned up wiring, or security evacuation, or, etc, etc, etc), and save hundreds of thousands of dollars of vaccines from loss, not to mention possibly human lives. Ice rocks.
- bcaa7f3a8bbc 7y agoWhat is "No Tech Magazine"? > NO TECH MAGAZINE – We believe in progress and technology > No Tech Magazine hosts all links and updates from Low-tech Magazine. We refuse to assume that every problem has a high-tech solution. Is it a parody site? Is it a "Low Tech Magazine" mirror site? Or is it sister site operated by low-tech magazine fans, just with a slightly different altitude towards technology, hence the joke?
- vanderZwan 7y agoIt is linked to by Low-Tech Magazine all the time, so it is a sister site
- _ph_ 7y agoIt looks as if this is using liquid water as a thermal capacity. While water has a high thermal capacity (4.2 J/g), the energy required to melt ice is much larger (334 J/g) and a melting ice block will maintain the 0°C until molten. So it would be more efficient and better guarantee the temperaturs in the fridge, if it worked with melting ice as the thermal buffer.
- DoctorOetker 7y agoSomething that I see rarely discussed when it comes to solar power and inverters is how a large part of the expense of an inverter stems from its internal temporary energy storage eelements (could be capacitors, could be inductors). Assuming illumination is constant in timescales of minutes (so thousands of electrical AC cycles), one can observe the following conundrum: a solar panel produces DC electrical power, while most consumer devices assume AC power input. So when designing (or choosing) an inverter one can make 2 choices in theory. If one draws on average half the current a solar panel can supply, the other half of the energy will simply recombine in the solar cell, heating it up. I will assume a resistive load (as a well designed product should not reflect energy back in the grid). An AC grid voltage is sinusoidal, and for a resistive load the current is also sinusoidal (the relation of course being U=RI) The power is P=UI=RI^2. so the power is also oscillating sinusoidally, centered about the average power. This seems to forces us to choose between the following 2 options: 1) have the inverter use all the incoming power (requiring electrical energy storage within the inverter: energy storage capacitors or inductors, which is expensive) or 2) have the inverter draw half the solar panel power (the other half is wasted as heat in the ), or have 2 solar panels (half the energy again wasted) to reach the same output AC power as 1); the inverter can theoretically convert the DC power to AC this way But in reality there is a third way, if you don't mind having 2 outlets where the AC voltages come out in quadrature. If two AC outlets deliver the same average power with the voltages in quadrature, then the powers will be in counterphase, so no energy storage capacitors or inductors are needed (cheaper inverter per watt), and no energy is wasted (full utilization of the solar panels). The only downside is that you can't deliver the total power to one and the same device. But consider some high-way stop convenience store in the desert with multiple refrigerators, say an even number of off-grid refrigerators, then who cares if half of the refrigerators use AC power in counterphase with the other refridgerators? A similar reasoning could be used for houses in a street, where the even houses and the odd houses are powered in counterphase (voltages in quadrature), which would substantially decrease the costs for inverters.
- dmurray 7y agoOr a single refrigerator with two cooling elements.
- Quequau 7y agoSome months ago there was an interesting article here about some startup using "AI" to determine the precise design of compressors for a given refrigeration design specification. In that article it was suggested that getting the exact size and shape of the compressor elements was more fiddly and troublesome than "it was worth". So this start-up's value proposition was making it way easier to develop very well balanced refrigeration / heat pump designs... which in turn are significantly more efficient than current state of the art in mass production.
- mcv 7y agoWhen I traveled in Mali in 2006, some villages had a single fridge running on a generator to keep water for tourists cool. Tourists can't drink well water, and selling them bottled water is a source of income for the villages. But having a generator running for that is wasteful. A cheap solar fridge would be a perfect solution.
- gambiting 7y agoYes, but it's probably one of those things where the village can justify spending $100 per month on diesel for the generator, but wouldn't be able to justify $1000 for a solar panel large enough to run the fridge.
- mcv 7y agoPossibly. It would probably be a good idea if someone helps those villages fund the new fridge. Saving that $100 per month would add up quickly.
- jkoudys 7y agoI'm sure they're capable of multiplying by 10.
- gambiting 7y agoHave you met any poor people? Once you're poor you only buy something that you can afford right now, it doesn't matter that spending more would save you more money in the long run.
- Curnee 7y ago“The reason that the rich were so rich, Vimes reasoned, was because they managed to spend less money. Take boots, for example. He earned thirty-eight dollars a month plus allowances. A really good pair of leather boots cost fifty dollars. But an affordable pair of boots, which were sort of OK for a season or two and then leaked like hell when the cardboard gave out, cost about ten dollars. Those were the kind of boots Vimes always bought, and wore until the soles were so thin that he could tell where he was in Ankh-Morpork on a foggy night by the feel of the cobbles. But the thing was that good boots lasted for years and years. A man who could afford fifty dollars had a pair of boots that'd still be keeping his feet dry in ten years' time, while the poor man who could only afford cheap boots would have spent a hundred dollars on boots in the same time and would still have wet feet. This was the Captain Samuel Vimes 'Boots' theory of socioeconomic unfairness.” ― Terry Pratchett, Men at Arms
- JulianMorrison 7y agoSee also: https://en.wikipedia.org/wiki/Pot-in-pot_refrigerator https://en.wikipedia.org/wiki/Pot-in-pot_refrigerator
- lancewiggs 7y agoWhen I see articles like this I immediately go to Ali Express and search for the appropriate term - in this case "solar power refrigerator". The exact solution isn't there but there are DC fridges for sale and examples of the set-up you require for solar charging. So this is a solved problem. Shenzhen is well ahead in the hardware innovation game. If you have a hardware idea look there first.
- davidhyde 7y agoA DC fridge does not "solve the problem". The problem the author solved was not having to use a battery to keep the fridge cold at night or when it rains. He did this with a thermal mass (a large tank of water in the fridge) that takes a while to heat up. Kind of like using an ice pack in a cooler box. I'm assuming that he used an AC fridge / freezer with an inverter because he already had one. Besides, I've never seen a large inexpensive DC fridge before. They just don't enjoy the same economies of scale.
- tim333 7y agoI've used the thermal mass of water to keep the darn thing quiet at night in a studio flat - put bottles of water in the ice box and turn it off over night.
- jkoudys 7y agoPlus DC motors are just fundamentally different from ac. AC is generally simpler and less maintenance, so it's not purely a question of scale.
- gg82 7y agoAnother similar project. http://mtbest.net/chest_fridge.pdf http://mtbest.net/chest_fridge.pdf
- jammmety 7y agoI love the simplicity of removing the requirement for a battery. In applications where one is necessary, and portability is not an issue, we have been looking at saltwater batteries. Non toxic, 15 year lifespan, 100% DOD, heavy so hard to steal… https://www.bluesky-energy.eu/en/greenrock-saltwater-energy-storage/ https://www.bluesky-energy.eu/en/greenrock-saltwater-energy-...
- abdullahkhalids 7y agoLooks very interesting. Is this you? What are the physical dimensions (LxWxH) of say 5 kWh and 10 kWh batteries? Edit: Okay, found it [1]. For 2.7KWh it is Height 929mm, Width 313mm, Depht[sic] 329mm. That's large but definitely within acceptable usage. Follow up question: What are stacking limitations? How much clearance do you need between different two modules or wall and module? Can you stack vertically? [1] https://www.bluesky-energy.eu/en/salt-water-battery-aib-technology/ https://www.bluesky-energy.eu/en/salt-water-battery-aib-tech...
- jkoudys 7y agoIt's a very cool, back to basics approach. To me it sounds like building a solar freezer makes its own ice (not literally), so it's an ice box when there's no power. When it comes to "when all you have is a hammer" type thinking, HN tends to use high-tech, trendy approaches as its hammer. Sometimes taking a step backwards and looking to simpler solutions gives us the better approach. I read the phrase "once battery technology improves" so much on articles about solar power I've become numb to it, so I found this a refreshing read.
- deleted 7y ago[deleted]
- softwarelimits 7y agoI live without a refrigerator. It works. Probably most people do not need that thing, too. It seems to be a cult object of prosperity. It just happened a few years ago while travelling a lot (by train), but then I found that idea interesting and never bought one, just to see if I "can do it" without. After a few years I do not even know what I would store in a refrigerator. Yes, of course, I am living in a city, with everything I need in markets around me, but it really just takes a little bit of planning and thinking to not need that thing even in remote places, I did that, it worked.
- jrugk 7y agoI don't even know what to say about a comment like this. I take it you have loads of time and/or money or live off bread and nuts?
- vectorEQ 7y agothere's plenty of ways to store things without refrigerating them. you can keep meats and other things for a long time without refrigeration.. using for example salt.
- munk-a 7y agoThat would be such an insane amount of effort to go through to replace a fridge.
- k__ 7y agoMaybe they only got a freezer?
- AmericanChopper 7y ago> It seems to be a cult object of prosperity These sorts of strange delusional comments, followed up by a claim that they can’t understand normal perspectives on things like “what would you do with a fridge”, are surprisingly common on HN. I have no idea what sort of thinking goes into a comment like this, but I suspect it’s sort of role play where they imagine the world would be such a great place if only everybody else also prescribed to their fringe view on fridges.
- magoon 7y agoIce is the battery. Freeze the ice using solar when the sun is beaming.
- ryanmarsh 7y agoI wonder how efficient water is for storing and transferring energy as opposed to something like a lead acid battery. Ice takes a lot of energy to freeze. That means your freezer is going to be really inefficient for a long period of time once the power kicks back on. Also, any other food you put in the freezer is a thermal mass as well. It might be the last to thaw but it could also be the last to freeze if you deplete the "battery" and have to start the process over. I'm surprised he didn't invest in further insulating the freezer. Deep freezes are not well insulated and waste more cold than your typical cheap foam beer cooler.
- mikepurvis 7y agoI feel like preserving ice over long periods of time has become a bit of a lost art, but before mechanical refrigeration, ice was sent extreme distances by ship and rail and stored for months at a time, see: https://en.wikipedia.org/wiki/Ice_trade https://en.wikipedia.org/wiki/Ice_trade
- ryanmarsh 7y agoI've read up on this quite a bit. It was incredibly inefficient and worked mostly in cooler northern latitudes. At southern or tropical latitudes often 90% of the product would melt before it made it to market. Insulation was primitive (saw dust).
- ghostly_s 7y agoYou need to throw out your fossil-economy preconceptions. Efficiency is irrelevant when you're running off direct solar energy. Sure, you could drop the price of a complete unit if it can run on a smaller panel, but the significant variable is not energy efficiency, its resilience to intermittent insolation.
- artsyca 7y agoNo Tech Magazine speaks to me on a very deep level --
- tuhinkarmakar 7y agoB nmn .Mm.m...... ..
- geggam 7y agoWhen baling hay back in the day we would drop the beverages down the well in a fishing basket. Cold Cold drinks
- quirkot 7y agolarge chunks of downtown chicago are cooled with ice storage. See here: https://enwavechicago.com/how-district-cooling-works/system-operation/ https://enwavechicago.com/how-district-cooling-works/system-...
- RileyJames 7y agoI’m interested in building one. Would be a nice to have, although buying ice in summer, and mining from a snow bank in winter works too. 1kw of panels is a lot tho. Not going to work for many van life situations.
- sly010 7y agoCould you improve this further by somehow automatically controlling heat exchange between the thermal mass and a separate grocery compartment? That way the thermal mass would really act like a battery, you could save all the energy during a sunny week and use it over time?
- FemmeAndroid 7y agoPrevious Discussions of Joey's Fridges: Fridge 0.2 https://news.ycombinator.com/item?id=18770213 https://news.ycombinator.com/item?id=18770213 Fridge 0.1 https://news.ycombinator.com/item?id=17106098 https://news.ycombinator.com/item?id=17106098
- ivanhoe 7y agoThe best hack I've seen for refrigerators is piping the outside air into it in winter. In Alaska and other cold places like that people can use refrigerators passively cooled by outside air for half a year and more, using almost zero electricity.
- 52-6F-62 7y agoThere's also the old Canadian bar fridge. It's when you stick your beers in the snowbank while hitting the ice, bud.
- Scoundreller 7y agoExcept then you’re actively pumping cold air into your home, increasing the load on your heating system. While a fridge works by extracting the heat from the stuff you put in your fridge and heating your home with it, decreasing the load on the rest of your heating system before even accounting for the compressor inefficiencies. Kinda like when hotels put their ice machines in some tiny room on each floor: that room gets really hot because it’s tap water in and ice out.
- ivanhoe 7y agoYou're pumping cold into the fridge, which is insulated as well as the piping, so I imagine it doesn't significantly affect the room temperature. You're right that fridge does heat up the room, but it's not that significant when it's -20^C (-4F) outside, you'll need to heat that house a lot more anyways.
- Scoundreller 7y agoThe fridge is much more poorly insulated than the walls, with more surface area to boot. And any wind outside will suck out warm air or push in cold air with every opening. Point being, that low-tech fridge (ice box connected to outside) is thermodynamically inefficient if you’re heating inside, while an electric fridge is an efficient heat pump. In a cabin with poor insulation and “limitless” wood, go for it. But for a modern structure, it’s not fully thought out. What would really make sense is a fridge that moves heat outside in hot climates.
- tpkj 7y agoFWIW, and this does involves battery, but it is an off grid power solution. https://zolaelectric.com/ https://zolaelectric.com/
- PorterDuff 7y agoIt would be interesting to know how much of refrigerator power consumption is due to door opening/insertion of warm food and how much is imperfect insulation. Given that the writer of the article doesn't appear to have space issues, it would be cool to see a homebuilt unit with much higher insulation using an existing freezer to mine for parts. I really like the redneck Yeti coolers that people build. A more trivial modification might be to put strips of plastic across the opening so that less air interchange occurs when you put stuff in or out.
- mumblemumble 7y agoI'd also be curious to know how much of it is the fridge being too close to the wall. I assume you need to be able to get decent air flow over the radiator for it to work efficiently, and that you won't get decent air flow if it's only a couple cm away from the wall, or recessed into some cabinetry that's built tightly around it.
- miohtama 7y agoThe source code contains the latitude and longitude of the device location for Sun cycle, with an interesting comment https://git.joeyh.name/index.cgi/joey/house.git/tree/src/Sun.hs https://git.joeyh.name/index.cgi/joey/house.git/tree/src/Sun...
- bmsleight_ 7y agoWhich actually points to some mountains https://goo.gl/maps/pwiSWB9nKy55iiCD8 https://goo.gl/maps/pwiSWB9nKy55iiCD8
- syncsynchalt 7y agoWest, not East. https://goo.gl/maps/MaYQ8BQBM16EEiiv8 https://goo.gl/maps/MaYQ8BQBM16EEiiv8
- logfromblammo 7y agoTo go slightly higher tech than a water tank, you could line the inside of the fridge with bags of phase-change material keyed to around 2.8°C. Then you program the thermostat to shut off at 1.0°C and turn on if 2.8°C or greater (and powered). That ensures that the phase-change material is always completely frozen after a long period of being powered, and keeps the fridge at a good refrigeration temperature. Tetradecane paraffin seems like a good starting point. It's not always easy to find phase-change data on heavier organic molecules, even plain old alkanes, but here are a few in about the right range: 5.8°C n-tetradecane C14H30 5.0°C 2-methyl hexadecane C17H36 4.8°C 2-methyl heptadecane C18H38 2.5°C 2-ethyl octadecane C20H42 0.6°C 3-methyl octadecane C19H40 The closer the branch is to the center of the chain, the lower the freezing point. It's likely one could get a decent refrigerator-liner phase-change material just by chilling liquid mixed alkanes to 4.0°C, filtering out any solids, then chilling to 1.0°C, filtering again, and keeping those solids. Those are exactly the types of molecules refiners hate. Similar isomers are already removed and reprocessed to improve the cold-temperature characteristics of diesel fuel, because otherwise they gel, and gum up cold-flow filters. Rather than cracking them all into more desirable fuel molecules, some could be diverted as fridge wax.
- aidenn0 7y agoIIRC some PFCs have a higher heat capacity than water (one reason why they are used in fire extinguishers). I don't know if its sufficiently higher to merit the extra cost though.
- srmatto 7y agoIts a little frustrating that the author didn't include a cost for the project. I understand that some if not all the parts are generic and can be swapped out, but a ballpark sum would be helpful to compare against products like this: https://sundanzer.com/product/dcr165-dcf165/ https://sundanzer.com/product/dcr165-dcf165/
- beached_whale 7y agoYou see refrigerators that are propane/electric or both but use the ammonia/water cycle to produce a chill. You make heat to boil off the ammonia(I think it's 60C) and then hold that in a vessel and let it recombine as needed. Ammonia is hydrophilic and the reaction of them is endothermic. There are a lot of ways of getting heating to 60C and doing this. I have always thought that a system could use evacuated solar tubing to generate the heat.
- Pfhreak 7y agoThe data linked shows the fridge sitting above 40 degrees F for days at a time. From what I understand about food safety, those conditions will allow bacteria to propagate. It looks like a good start on a project, but I'd be super nervous about using it in a 'production environment' for any period of time.
- jbob2000 7y agoThat just means it needs to be advertised as a cooler, not a refrigerator. This thing is perfect for the dock at the cottage to keep the beers cool.
- MarkMarine 7y agoI worked at a startup and designed the thermal battery and pumping systems for a solar powered milk chiller/storage system for the Indian market. About 500L of milk chilling & cold storage capacity, also storing solar energy as cold (not ice) Depending on where you are, you need a whole bunch of insulation to not condense vapor on the outside of your storage, because condensation is a killer for efficiency. My system needed about 50mm of foam rubber for the worst case, around a 1000L thermal storage medium tank, which makes these systems very large.
- _iyig 7y agoA related idea I’d love to explore is an off-grid fridge cooled via the Stirling cycle [0]. It’s essentially a Stirling engine run in reverse, using power to move heat vs. the other way around. No refrigerant is required, just an external source of power e.g. a DC electric motor. Such technology is used today for ultra-low-temperature cryonics. At least one Stirling cycle mini-fridge has been developed and brought to market; it got rave reviews from the boating community to whom it was marketed, but went out of production and was never followed up [1]. I’d love to find out why this technology hasn’t been more widely deployed. [0] https://en.wikipedia.org/wiki/Stirling_cycle https://en.wikipedia.org/wiki/Stirling_cycle [1] http://www.cruisersforum.com/forums/f115/coleman-stirling-power-coolers-12685.html http://www.cruisersforum.com/forums/f115/coleman-stirling-po...