Stirling Heat Engine to Stirling Heat Pump : How is it done?

[@raindogs451]

I’m a 30 year HVAC guy with a great deal of knowledge on a micro level of installing and maintaining these types of systems, but with a tiny fraction of your knowledge on a more global scale, including the science, and policy wrestling. I comment ONLY (because I don’t think I have any particularly useful knowledge) but because I’ve come to the realization that often personal pain has to be induced to get people to move. “We’re all going to die” is a diffuse and hazy concept and so people fiddle while Rome burns. Tell them, “energy costs will rise 20% next month IN YOUR HOME”, and people will move; they’ll buy a more efficient unit. The same principle existed when gas prices shot up: SUV sales plummeted, while small car sales shot up. I perceive that “global warming is going to kill your grandkids” isn’t an evolutionary wolf at the door threat to compel people. As much as I hate to say it, personal pain is needed. Most people are reactionary, as opposed to proactive. Self interest induces inertia.

[@janami-dharmam]

The technology did not develop, because in my opinion, the fossil fuels were cheaper and the cost of conversion would have been significant. The picture is different today...

[@sailor67duilio27]

"We are all going to die", the question is when. Therefore, why wasting time awaiting to die, let's get on with living.

[@NickCombs]

@Atlas V Everyone is lazy. It's evolutionarily advantageous to save energy unless absolutely necessary. We struggle against that instinct every time we try to be proactive.

[@ChrisGlenski]

Hi Matthew, from a chemical engineer who finds HVAC stuff fascinating but am not the best at communicating the impact of well designed hvac systems, do you have any other thoughts on how we can communicate with our older relatives on this issue? Are there other benefits to heat pumps/modernization beyond co2 emissions and saving money?

[@Calligraphybooster]

I suggest you look up prof. Tim Garrett and what he has to say about thermodynamics. (The Second Law of-) I do agree with you, but think that when we consider our fate, and what we might do to stave off imminent disaster, only prof. Garrett is taking a look at things from the appropiate perspective.

[@haroldb1856]

I was first introduced to the Stirling cycle as a young mechanical engineering student, during a summer with the navy. At the time, the Stirling cycle was being considered as an engine for submarines. For years, it was an obscure, niche cycle, never finding wide adoption and recognition. It's great to hear that it might finally have its day.

[@grahamboddington5433]

Love your channel. Commercially available in 3 years. I recently installed a Hot Water Heat Pump System that uses R744 (CO2) refrigerant technology rather than the CFC's. Love the idea that CO2 is put to a better use. The max COP is 5.9 at 30 deg C and still a COP of 3 at -10 deg C. Would love to use this technology in 3 years time but in the meantime it is still possible to implement significantly improved heat exchange systems. Don't wait for the better technology - go improve what you have now. Use all the options available rather then waiting for the best one still to come. Same with motivating people - there in no one best way. Different things motivate different people - use them all. Even the trolls will change eventually - ignore them and just get on with it.

[@carlbrenninkmeijer8925]

What I like most is how clear your presentations are !

[@davidkirkland3140]

I am an HVACR master technician. If this is true this company has found the end of the rainbow. You people will control my industry in 10 years.

[@daviddavids2884]

IF..... not

[@davidkirkland3140]

@@daviddavids2884 if not then on to the next idea

[@benm3574]

I am an inventor and in my past life a HVAC mechanic so my knowledge in this field and the design overview tells me they are on the right path but missing a few key pieces to make this commercially viable. One issue is the helium with supply, cost and required containment as well as the mechanical difficulties they are encountering in the life cycle of this application. The properties needed for the level of efficiency they are trying to achieve may require a hybrid secondary delivery system. Well done though and a great video. We are the makers and so we are the future of technology in the pursuit of a better world.

[@pdxyadayada]

..you know how difficult it is to find good news (solutions) these days? Thank you for your ongoing endeavors!

[@willmcgo8288]

There are commercial Stirling heat pumps that are used to cool to cryogenic temperatures. Some of those units are used for cooling superconducting RF filters on cell towers. When the cold end of the unit is put in a thermos it can cool air enough to liquefy it . Probably not very efficient, but very compact and simpler than typical compressor based refrigerant systems. This is a great video, thanks!

[@arturoeugster7228]

This is exactly what ~30 years ago Atlantis Energy Ltd installed in the maintenance shops in Vaulruz is Switzerland A stirling heat pump using hydrogen working gas. The only problem is to be sure that no air is introduced during the occasional replenishment. The Delaval Stirling unit was used.

[@grinpick]

I watch your videos regularly and really like your presentation style. I somehow have the feeling that if I were walking past your house you'd tell me the kettle had just boiled and invite me to sit on the porch with you and have a cup of tea. And me, a loutish American who'd prefer coffee. But I'd still accept, with alacrity (which, in this case, is how I take my tea. But I digress.) The technology in this episode seems potentially even more transformative than your usual. Hope it can be packaged in a practical, scalable and durable device. Thank you for making me better informed.

[@PeterJFlower]

Wow what a brilliant idea. I've worked as a consultant engineer in the HVAC industry since the 1970's and I never thought that Stirling Engines could do that. I'm guessing that it works backwards as well providing heating on cold days as well as cooling on hot days. I have a working model of the stirling engine just like yours and I have always been facinated by it, now I know why. Wouldn't it be great if all of the factories currently making soon to be redundant petrol and diesel engines could change to producing these in hug quanitities, giving economies of scale and better prices.

[@daviddavids2884]

yer guessing, WRONG. ambient temperature is not a factor. when the 'system' is driven, it 'makes' HEAT at one cylinder and Cold at the other. consequently, there is ALWAYS an Unwanted energy by-product; to get rid of, Somehow. googletranslate

[@stephenwilliams163]

The algorithm sent me your way a few weeks ago and I gotta say that I really appreciate your channel. I have very little technical knowledge of engineering and yet I am usually able to wrap my mind around the concepts you're describing. Thanks!

[@jerrykingzett4848]

We used Stirling engines for classroom labs and it was a dramatic difference when we used Helium. It was amazing improvement over air! Although it bothered me that this Helium gas was forever lost for human use.

[@ZacLowing]

I was going to google that, but can we make our own Helium? Is it hard to contain? Thank you in advance

[@mikefochtman7164]

Of course H2 is even better. But of course comes with a lot of safety concerns. But H2 is readily available whereas He is limited.

[@robertvanderbaan3722]

Feelings again. Something has to give for progress.

[@janhemmer8181]

60 years ago Philips in the Netherlands developed the "koudgas koelmachine", as a spinoff from its Stirling research. Had all those features - swash plate, regenerator and compressed helium. These are used all around the world for cryogenic research. Only the heat exchanging, pumped system dipping in a liquid is a new idea - and a great one I must admit! Everybody will be happy with a noiseless heat pump that doesn't drive you mad with infra sound.

[@MegaSnail1]

As always your reports offer hope for the future. I can't thank you enough for all of your well done presentations. Lets hope some big investors are following your reports. Be well.

[@larryteslaspacexboringlawr739]

i am going to have to break out the old thermo text books for this one, great video

[@TheStandardJoe]

Philips in the Netherlands had a whole division dedicated to Stirling Engine R&D in the 1970’s - they demo-ed a bus, river boat and car.

[@chargingcycles]

I was lucky enough to buy one of the Coleman Stirling cooler/freezers over a decade ago. Just used it last weekend... Lovely device.

[@MervynPartin]

The refrigerant in our wall mounted, air sourced heat pump/air conditioner is R290 which is, I believe, a high purity Propane. We have found it very effective in heat pump mode, but are now waiting for some warm weather to see how effective it is in cooling. That was merely to say that there are other refrigerants than CFCs available, even Ammonia might possibly be used in sealed domestic units. The Stirling cycle machine shown looks promising, although I have misgivings about the use of Helium which is a very finite resource. Perhaps Hydrogen might be an alternative? Both gases have their problems with containment due to their small molecular size, and Hydrogen embrittlement of steel is an issue. I look forward to developments and hope that system proves successful.

[@tomastomesek8062]

Your channel is fantastic. As a Science teacher I want to show the kids the cutting edge of what is around. Your channel does that. I noticed Australia has so many excellent technologies and companies that provide or underpin sustainability.

[@michaelstarkey9745]

Tyvm for what u do soldier for future generations and it train of thought of teaching students TODAYS technology as opposed to something from a book written 90 years ago

[@Warekiwi]

Another excellent report! Now I feel guilty as I'm about to install a 5kw air to air aircon system to cool my living room duringly the increasingly hot UK summer. I wonder if the system you described will ever work at the smaller end of the market? Another use of Stirling engines that you may not have heard of was the Whispertech co-generation system. Designed and made in NZ but marketed in the UK during the 90s. It ran on natural gas and replaced a domestic boiler with the extra benefit of about 1kw of electrical power. Sadly the Christchurch earthquake destroyed the factory and production never restarted.

[@Kevin_Street]

Welcome back, and thank you for this great new video! For more than 160 years the wonderfully elegant design of the Stirling engine has been inspiring people to push the boundaries and reach for elegant simplicity in their own designs, so it makes sense that this Fluid Mechanics company would use the Stirling engine as the basis for their improved heat pump. And with a 30% energy efficiency over conventional models and no HFCs their machine should sell itself. But I worry a little about their odds. Most start-ups don't succeed, sometimes for reasons that have nothing to do with the technology behind them, like business culture. In the US there's an almost ideal climate for start-ups, with lots of venture capital floating around and everybody wanting to be the next Tesla. Here in my own country of Canada the business environment is very different. There isn't much venture capital, and the money that does exist tends to be very conservatively managed, with banks and other financial entities often unwilling to give you a loan if your business plan is based on an unproven new idea. I don't know what the business climate is like in Britain, but hopefully it's more like the US and less like my home.

[@mrpaul5726]

Great potential for this so called old technology. Turns out to be an elegant solution to a modern problem.

[@kensmith5694]

A few points to add to the mix: Stirling heat pumps can reach the temperatures needed for superconductors. The Stirling engine running off how much hotter the solar thermal panel is, could drive a heat pump. The idea is that the total heat delivers to the living space would be more than just the solar thermal panels are providing. On a bright sunny cold day, this could be very useful. A home made system using hydrogen would be a practical thing to build. With a helium one you need to be extremely careful of the leakages. With a hydrogen one. losing a few CC of gas a day could easily be made up by extracting hydrogen from water. Instead of plates as fins, I would try rows of pins as fins. You get more surface area with pins.

[@kensmith5694]

@@dschmidt5293 I just had an interesting thought. PV cells are most efficient in the near-IR and red end of the spectrum. For longer IR they just get hot. I wonder if some sort of low loss wavelength selection could be done to send what works well to the PV and the part that doesn't the the sterling.

[@chuckkottke]

Dave, several years back I attended a Midwest Renewable Energy Fair and asked an old salt why Stirling solar wasn't the mainstay, given its efficiency at converting solar energy into electricity. His answer was that due to so many complex and wearing parts, seal issues, and overall cost, PV panels were preferred. As time passes, these problems may be solved, so it's refreshing to see the work being done on heating and cooling systems with Stirling engines. Thank you for bringing forth a good look at the current state of technology in this field.🌄. One other thought: what about Peltier junction coolers; are they making progress on them for vehicle or home cooling? 🌡️💧🌞

[@nicholaskelly6375]

As noted earlier Chuck the main problem with the Stirling engine is its power (or lack off) If you keep it simple then it isn't very powerful at all. To improve its performance it becomes complicated as Phillips found out. That doesn't mean you shouldn't use its potential. But I fear your "Old Salt" was correct. If you want electricity from solar then PV is your best bet. However there are always situations where things like the Stirling engine would be applicable. The most amusing application must have been Ericsson's ship the 'Calorific' which had to be "bump started" by it's sails!

[@talldarkhansome1]

10 to 15% efficiency according to google, so it's a no go.

[@kirknay]

Peltier effect devices are inefficient af, and that's a limit of the effect itself. You're not gonna see them for higher scale than a dehumidifier, as we have mini fridges that have more effeciency with a standard unit at a similar scale than a peltier at about 5 cubic cm.

[@juanfermin1841]

If you have some space it's better to use the Canadian Cooling System, it will take a 33ºC home down to 16ºC. and it will save you hundreds per year on cooling costs.

[@data9309]

@@juanfermin1841 Is this Canadian Cooling System the same as radiant cooling? If so, it is apparently excellent for new construction and large buildings.

[@CplusO2]

Hi Dave, thanks again. Going through the comments section reveals a pretty clever audience. Some other channels like yours are creating ways for all this brain power to collaborate.. ( discord groups etc. ) Your viewers are a valuable resource.

[@tedrees5989]

That is a great execution of engineering. The approach is exactly what is required. The question is if it can be scaled up into a successful business.

[@ZenaiditaLenis]

First video I have watched from you. I have a newly bought Stirling engine powering the fan on my wood stove. As a control system person who has written software to control high power refrigeration systems. Including multi stage cooling systems (a cooling system cooling another cooling system to get low enough temps with sufficient horse power). Its most interesting as reducing power consumption is generally enjoyed by the end customer.

[@martinevans1427]

There are parts of New Zealand where you don't need to dig deep to reach high temperatures. A stirling engine in your back yard in Rotorua, for example, could supply all your needs. When the "fuel" is free, efficiency can take a back seat.

[@rogeradamz]

this is the most realistic eye-opening tech presented on this channel! Big thanks!!!

[@michealoflaherty1265]

I think the killer application for this are supermarkets as they have a simultaneous demand for heat and cooling. Great video!!

[@coreys2686]

District heating too, combined with ground source heat pumps. And liquid metal batteries for long term storage.

[@michealoflaherty1265]

@@coreys2686 All approximately 3 years away 😊

[@christalbot210]

Restaurants would be another great choice, especially if the heat could be used for stoves and ovens. Of course, a stove or oven needs a few hundred degrees, so I doubt it could run solely on that. Still, would be cool.

[@punkdigerati]

@@christalbot210 Hot water for washing dishes is a good case, and there are already heat exchanger systems that can reclaim waste heat from refrigeration and AC systems for hot water, that don't seem to be used much, sadly. They also happen to increase the efficiency of the refrigeration units.

[@VTdarkangel]

I see a few issues with this. First is you have moving seals in this system...a lot of them. They are notorious for wearing and breaking down regularly. These seals also are not just seperating different parts of the system with the same fluid, but they are seperating different fluids. When they fail, you could have contamination in the working fluid that will severely rob efficiency. This is complicated by the use of helium or hydrogen. Helium and hydrogen are incredibly hard to store for long periods of time because they leak so easily. The same small molecule/atomic structure that makes them great heat transport fluids for this application also makes them very leak prone. I see the potential in this in this technology, and I myself have wondered about the use of a stirling machine as well, but there are some real problems that need to be worked out.

[@yasirrakhurrafat1142]

You mean the pistons themselves ? I think I've found a theoretical solution. If this peaks your interest. I'll elaborate. Maybe you can even tell me why it wouldn't work.

[@sandorrabe5745]

@@yasirrakhurrafat1142 interested to learn more!

[@yasirrakhurrafat1142]

@@sandorrabe5745 so you're inclined to hear my broken English, try to explain how I have a novel strategy of replacing pistons ? Great ! So if you look up foot pump on google, what you'll find is a device ( usually in yellow color , and has two inlet/outlet fluid ports ) that is made of one solid object that kinda resembles a spring. You press on that device, it performs compression. Same as a piston. Yet its not limited by very tight tolerances. It may potentially be able to replace the piston of a non-combustion engine.

[@richardabrahams585]

The real truth engineering channel..outstanding team!!! Bravo!!!

[@Maths4you4real]

This is lovely. This is my first time learning about the sterling engine and its applications.

[@WirelessGriff]

Another great coverage piece of a new development. Thanks Dave!

[@rustywater3219]

Commercial buildings use hydronic systems. They heat air to pump everywhere via ductwork. At the end of the ductwork, at each conditioned space, they have VAVs (variable air volume) boxes with coils and fans. The coils add on-demand air flow (with a smaller fan) and the coils circulate heated or chilled water with throttle valves. All controlled by a centralized scada system. You could likely use this Stirling engine to cool the hydronic water. The heated water is sometimes part of a boiler system to create hot water through heat exchangers. But you could likely get creative and use the Stirling there as well.

[@DanielinLaTuna]

Thanks for the model of the Stirling engine. I’ve never really understood it. But as they say, “seeing is believing”; or in this case, understanding.

[@marymarlow5598]

They avoided speaking on horse power out put. The Swedes have a submarine that runs on sterling engines. It's not fast, moves about 25 Knott's max. It's the quietest sub out there.

[@justsayen2024]

I've been working in the HV/AC field for about 39 years seen many compressors different styles come through it's nice to know they're still making new Innovations to make them more efficient. Generally its investment that holds back innovation, only unfortunate side-effects is they money they charge for units that are hyper-efficient. Sorry about the trolls you have to deal with😒

[@ColinKable]

Whenever I see heat pump technologies I think someone should design a home circulatory system that shuttles hot and cold temperatures to where they're needed. One could picture having fridges, stoves, water heaters and air temperature systems all running off, or at least supplemented by, a central powerful heat pump system.

[@tomwickland]

A ground-source heat pump heats our water and heats and cools our home. It comfortably maintains the temperature of our home year-round through very cold Chicago winters and hot, humid summers. However, it will not heat or cool our home rapidly. I don't think such a system would work well for quickly creating the very hot temperatures needed for an oven or a stove.

[@nickwarburton9273]

Yes I like this idea. I know ther are some tech about for recovering heat from drains water etc. But something that could be plumbed together efficiently would be fantastic. Imagine a circulatory system running around your house in the same way as the wiring.

[@rustywater3219]

Look up hydronic heating systems. They use this in Commercial buildings.

[@Number_Free]

I'm not a heating expert but I think that electric heaters may be the best solution, as they can easily be controlled and they are very efficient I believe. The challenge is to produce the e-juice in an efficient manner of course, which is where SE's may help.

[@marcofossa5741]

@@Number_Free cop of electric heaters is by definition equal to 1, while for heat pumps (of any kind) is much higher.. The ground source heat pump at the Uni where I teach. (applied thermodynamics fir mech. Engineers) is rated at cop=4.5, since its working temperatures are suitable (according to Carnot law) to this aim. Back to this video, just great, so interesting and correctly described in terms of thermodynamics laws Compliments Sir Dave

[@Neodymigo]

For Stirling machines, the size of the equipment for practical use, is a prohibitive cost factor at low working fluid pressure due to volume of gas being cycled. To transfer a practical amount of heat around, you have to go to high pressure helium or other working fluid, at which point mechanical sealing and weight of dispacers and connecting rods becomes an issue. The large amount of heat absorbed by common refrigerants and their high heat transfer rates as they evaporate or condense gives them a huge cost advantage over Stirling based equipment. Just giving you the perspective of a mechanical engineer whose interest in Stirling machines and career in refrigeration spans nearly 50 years.

[@Hclann1]

Wouldn't mass production lower costs?

[@chaorrottai]

That's exactly why high pressure striling engines are used where power density is needed. NASA made this really cool stirling engine: kzbin.info/www/bejne/gZPReJ-Zhs5_Z8U it's a shame they did all that testing, cost assessment and manufacturing assessment and determined it was realistic, feasable, marketable and easily manufactured and then did literrally nothing with it. Nasa still loves the striling cycle, just now they use a linear striling engined with automatically oscillating displacer and use that for nuclear power generation.

[@ellenorbjornsdottir1166]

Do you suppose high pressure air could be practical?

[@PaulSpades]

If leaking commercial refrigerants is an issue in a closed loop system with no moving parts, try keeping Hydrogen or Helium contained in a constantly moving multi-cylinder system. I also call bollocks on their efficiency numbers.

[@willm5814]

Finally! A practical use!! I remember getting excited about Sterling engines 10 years ago and then deciding that if this thing really had any promise somebody on youtube would be doing something more practical then a little fan for my woodstove 😂

[@TerraPosse]

There have been solar powered Stirling generators since the mid-80's. Mainly used inside the tropics of course.

[@IMBlakeley]

Helium because the molecule size is so small is much more prone to leaking than existing refrigerants. It is used to check for leaks in piping now for that reason. Also there are limited stocks and it is pricy.

[@pathall1532]

So why not hydrogen like the chap said ?

[@IMBlakeley]

@@pathall1532 Apart from hydrogen having an even smaller molecule size there is its tendency to catch on fire in the presence of oxygen.

[@benthere8051]

@@IMBlakeley There is not enough hydrogen involved for that to be an issue. We are not talking about a zeppelin here....

[@logic9140]

@@pathall1532 So hydrogen corrodes metals and more It’s huge problem for rockets and more NASA and other have spent millions trying to stop it It also leaks out even more than helium as it’s smaller along one action and can bind into metal, etc than get released out Every common and few exotic metals but few aluminum and copper alloys get much more brittle with hydrogen at room temperature but it’s worse at high temperature. You can’t use steel, other iron or nickel alloys, and even titanium core.ac.uk/reader/84914440

[@IMBlakeley]

@@benthere8051 That's not how it works at all, hydrogen mixed with oxygen/air is the issue the range of concentrations over which it is explosive is pretty big. Now you're using this as a working gas/fluid in a heat pump into a house and most likely the same room where there's a gas boiler or a cooker. good luck with that.

[@WhichDoctor1]

Only thought is that it looks very mechanically complex when compared to existing cooling systems. Looks like it would be quite a challenge to miniaturise down to something that could affordably go in a private car. But for building and ship level uses this looks really exciting!

[@chopper3lw]

Thanks for this video. I'd seen a couple that didn't explain their advancement in any detail that actually explained it.

[@rennieamundsen778]

I had a sterling engine when I was a child. That was over 60 years ago. The engine was mounted in a vacuum tube filled with hydrogen and featured a rotating antenna fitted with 4 -1 in, squares of paper. The paper was black on one side and whit on the other. The rotation of the squares was driven by the heat differential of the black and white sides of the paper. The system worked perfectly and the drive shafted wheel rotated as long as the sun was shining. Hundred year technology could potentially replace polluting heat exchange systems around the world.

[@paulmaxwell8851]

That was a radiometer. I had one too. The glass bulb 'contained' a vacuum, not hydrogen or any other gas. A Stirling engine is completely different, using a pair of pistons, a heat exchanger and usually a flywheel. They are fascinating devices. I hope to build one once my new workshop is finished.

[@rennieamundsen778]

As I stated the antenna with the 4 squares drove a drive shaft with a wheel. The wheel was fitted with 2 pistons much like the steam engine model that I also had. Both were science toys by Mechano a British firm that also produced a chemistry set and a microscope both of which I also had. The legend on the little engine that could stated very clearly that the vacuum tube was filled with hydrogen. It was a marvelous toy which I kept in my window for almost 20 years.

[@dg-vg9di]

Radiometer. Not a sterling engine.

[@coastalfog809]

Wow great Video! Videos like this are a joy to watch!

[@warrenbrooke2402]

Amazing! This could have good applications in Canada for heating homes with electricity to displace natural gas furnaces. There has been some work done with low temperature air source heat pumps, but these typically have a temperature range down to -20 C, and the outdoor temperature can get down to -40 C. If you want the indoor temperature to be 20 C, then the heat pump from Fluid Mechanics with an 80 degree lift would be a good fit.

[@janami-dharmam]

Whatever way you may look into, it cannot better direct heating. However, with a natural hag heating system, your flue gases will be at the inside temp and that will be a good candidate to run a Stirling engine.

[@Mrdevs96]

Direct heating as in electric baseboard heat ?

[@janami-dharmam]

@@Mrdevs96 Exactly! All other heating methods have inefficiencies built in.

[@Mrdevs96]

@@janami-dharmam yes efficiency is key, the combination of natural gas and stirling pump could be very efficient

[@Mrdevs96]

@@janami-dharmam a lot of heat loss in the electric heat

[@andrewal410]

HI Dave, a big thank you, for me this is the most interesting device you have shown us in the time I have watched your very interesting and informative channel. I am building a carbon negative house in the Algarve and this technolgy really appeals to me for heating the swiming pool.

[@davidgeorge7443]

Sunday morning now complete, time now for yard work. Thanks JHAT!

[@JustHaveaThink]

Cheers David. Glad you enjoyed it :-)

[@Sean_S1000]

I could sworn, I saw you do this this the other week. no issue with watching it twice as its good and interesting

[@JustHaveaThink]

Are you thinking of Matt Ferrell? He is my American doppelganger and he did a video on Stirling Engines a few weeks ago.

[@Sean_S1000]

@@JustHaveaThink Ah I am indeed, love both of your guys content! keep up the good work

[@lylestavast7652]

@@JustHaveaThink and he doesn't say "meethane". lol actually how do brits pronounce the drug methamphetamine ? meeth-amphetamine ? (I'm just joshing btw - my grandparents were brits...and my parents canadians... I'm a first gen American, so I'm entitled to speak oddly.)

[@jenssvensson9184]

There are heat pumps that use CO2 as the refrigerant, ie no harmfull hydrocarbon. I have got one works a treat. It is a Sanden a Japanese heat pump .

[@olisipocity]

Hello Dave. Thanks for your content, as always pretty easy to comprehend. I' am not an engineer but from my research and the viewing of other videos on the matter, I believe that the combination of the Stirling engine with solar to produce electricity, via a dynamo or similar device, and then use that electricity to run some kind of appliance, is less complicated and more viable, and perhaps less expensive. Never the less, any kind of technology is good if it brings any benefits to the world. However, it looks as if to pursue a greener goal, it will require a combination of systems that complement each other rather than a single formula or technology-based one.

[@jimgraham6722]

I have several Stirling engines and they are fun to watch, but in the end their main problem is thermodynamic efficiency. They do work at low temperature differentials but produce very little power. There have been many efforts to improve the efficiency of the Stirling cycle but without much success. For practical power generation using solar thermal, Brayton cycle and solar concentrators have better prospects. They same problem exists with the Stirling cycle if you use it in reverse to generate heat or cooling. A lot of power is needed to generate only smallish temperature differentials. Conventional cooling has the advantage here because it is not just pumping a working gas backwards and forwards through heat exchangers with all the pumping losses that involves. The conventional cycle involves pumping the working fluid in a sealed loop that includes a phase change that efficiently carries away substantial heat energy to a significant physical distance as latent heat.

[@robandsharonseddon-smith5216]

Late to the party but thank you. Comment mostly for 'engagement' but perhaps at 1 year post, it might be worth revisiting this one as it has great potential. One of the biggest challenges facing the UK is replacement of gas boilers - current heat pumps struggle to get water hot enough so larger radiators and pipes are required, but a good chunk of the UK seldom gets so cold that these systems would not work almost as well as a gas boiler as a direct replacement.

[@nicholaskelly6375]

At last The Reverend Dr Robert Stirling's Time Has Come!

[@JohnGilmour]

Maybe. Poor efficiency

[@nicholaskelly6375]

@@JohnGilmour John don't dismiss this. If the technology is as promising as it appears then it could be a "game changer". Another issue that is worth noting is that if the energy source is effectively free or very cheap (ie passive solar) then surely efficiency is less of an issue. More important is its effectiveness. Also of course it is always "horses for Courses" just because a technology may be "inefficient" (or indeed "old fashioned") doesn't mean that it should be dismissed. As there are often circumstances were it is viable.

[@JohnGilmour]

@@nicholaskelly6375 I guess I am a pessimist. I am all for innovation and discovery but we have been waiting for fusion for good percentage of my 66 years and I don't expect to be cremated by the energy produced from this source :-)

[@uzemakistyle]

@@JohnGilmour there's a big difference between fusion and the subject of this video though. It already has working prototypes that show good results, and though promises on 'when its market ready' can be taken with a grain of salt their challenges pale in comparison to getting a working fusion reactor.

[@nicholaskelly6375]

@@JohnGilmour So true John I am 62 and it would appear that for all my life nuclear fusion has been "25 years away into the future!" On that momentous day in July 1969 I was in hospital in Shrewsbury having broken my right leg a week earlier. I genuinely believed that nuclear fusion and moonbases were just a few years away! How wrong I was. We still have not got moonbases and nuclear fusion is still "25 years into the future" ! But I live in hope Nick!

[@robertjacklin4255]

Really interesting. From past operational and engineering involvement in refrigeration on petrochemical and natural gas production facilities, all have come under focus for the Montreal protocol and have been upgraded and/or replaced to comply. Some have chosen refrigerant free processes, or progressively lower GWP (global warming potential) refrigerants. The elimination of refrigerants is great, as is the improvement in efficiency with the isothermal compression and expansion. I will watch this technology develop with interest as the reliability is tested and proven.

[@dsdmtom]

I wonder what kind of seals they're using to keep the helium or hydrogen inside the cylinders. Those gases tend to leak very easily due to the small size of the atoms and molecules.

[@dougaltolan3017]

Leakage at the piston seals could go both ways, the expansion cylinder will suck inn from the yoke area and the compression cylinder will leak into it. That section could be filled with helium meaning that the only retention seal would be at the drive shaft. It might be that the system works better at an average elevated pressure in which case the shaft seal needs to be as good as you suggest. Leakage at the pistons would then only impact efficiency and not refill time.

[@logic9140]

Me too. Not all would leak out where it could be sucked in again. Hydrogen although cheaper than helium and more plentiful also leaks more and cause hydrogen embrittlement Maybe they found solution but I don’t know

[@boreddude3898]

@@logic9140 this is why everyone uses helium before hydrogen too, its still tough to contain but infinitely easier than hydrogen which can leak through even atomic pores

[@johnckircher]

Hydrogen is easy to come by with electrolysis to pressurize.

[@benthere8051]

@@logic9140 - Embrittlement is only an issue in the case of certain alloys.

[@Teddystream.]

Increasing the plumbing to assist entropy that's the game here to reduce size, lots of difficult engineering challenges and very complicated but seems to be relatively safer than some. good luck with the project.

[@dragonskunkstudio7582]

I had to watch this twice as it's just an amazing machine.

[@steveblack728]

Hi, I work for a large am& E Consultancy and we’re working currently with A few Local Authorities, on Decarbonisation projects, we’re struggling to find ASHP that will meet the criteria, if only this was available now, it would be superb, thanks for your interesting Channel I came across it a couple of weeks ago now and enjoy it immensely

[@MickyELee]

A geothermal "radiator" in the ground would minimize the temperature differential between the ground and a home, say 53 F in the ground and 70 F in the home. Really interesting.

[@kensmith5694]

Yes, and it is likely a pipe below the water table would be able to stay at the "53F" number you suggest more easily. Water moving through the ground would carry new heat in all the time.

[@picobyte]

A Dutch company tried sterling engine heaters to provide combined heat and power for homes. It was very efficient but all the mechanics made those units expensive and they needed to much maintenance.

[@Richard-fx6go]

This is quite a breakthrough in efficiency, not to mention the HCF savings. I imagine the maintenance on these engines will be quite high considering the moving parts and pressures involved. Using Hydrogen would exacerbate this.

[@tdoubt100]

Thanks for this Dave. Fascinating with an awful lot of potential

[@SpencerHeath-q4m]

The interesting aspect is if you consider geothermal as part of a sterling system, if heat is always available in say a desert and the ground is constantly a lower temperature, the system besides maintenance could be completely free of fuel, the heat batteries using bricks to store heat would even offer same efficiency at night.

[@Leopold5100]

another excellent well researched informative and inspirational subject matter ................... just have to watch this a couple more times till I am across all the technology and concepts ;-) [BTW model Stirling Engine Model as shown in video are available via eBay]

[@bretthorwood9396]

This is a great idea.

[@h.e.hazelhorst9838]

I like the little Stirling Engine. Ordered one a couple of years ago, amazing. Also big fun to build one using only soda cans, some plastic pipe and wires. But this heat pump stuff looks very promising.

[@devinhedge]

Appreciate this video. It’s been a minute (30+ years) since learning of the Sterling Engine. 🎉 One comment about fossil fuel use: I notice that nobody talks about the plastic/polymer aspect of oil and how there will continue to be demand for oil for industrial use, lubricants, and for manufacturing plastic/polymer products and coatings. Love your latex paint? Thank oil. Love your mobile phone? Oil again. It’s terribly pervasive and invisible relative to use in energy. Would love to see a couple videos exploring where scientists and companies are trying to find ways to reduce our reliance on oil for manufacturing.

[@mikefochtman7164]

Good point. But those uses don't put CO2 into the atmosphere (at least not directly/immediately).

[@DataSmithy]

Hi Dave, I really like where this technology is going. Having just installed a super effiecient multi-split unit, I can really appreciate the energy efficiencies, and money savings, of the new technologies being used even today. For example, the variable compressor driven by an inverter, and ability to heat a single room, vs the entire house. After watching this video, and the other video on the linear compressor by Magtor, I can't help wonder what the effieciency would be if the stirling and linear compressor technologies were combined! I am looking forward to watching how these technologies develop, and hopefully become commercial in the comming years.

[@markhonea2461]

It is one year later. The refrigeration industry is switching to a different refrigerant- R600. Believe it or not this is pure iso-butane. Yes, like in a butane lighter or camp stove. It is extremely more efficient than any of the other 'nasty chemicals' talked about in this video. And butane has a low static pressure as well. I'm sure many people will be thinking about the fire danger of using this in a domestic refrigerator, but in reality, only 3 - 5 ounces is used per unit. Not much. Haven't heard of problems with ignition - so far, and it is in very many units already, and will soon be mandated for all units, replacing the old hcfc systems. By the way these units require FAR LESS electrical energy to achieve the same desired results.👍

[@DavidHarsant1]

still not a suitable replacement on larger commercial applications.

[@Yanquetino]

BIG thumbs up! I responded in Patreon. Thanks, Dave!

[@philmanke7642]

Really love the Sitling principle.!.!. I've made about a dozen different working types.!.!.!.!. Most intricate is a 4 Cylinder, actually eight; four displacers and four double acting power pistons.!.!. It runs slowly, about 200 rpm, with smoothly overlapping power strokes,!.!. They come on and recede gradually, as the heat is exchanged.!.!.!. Four little gas flames under the displacers runs the thing, which I've mounted in a 5 gal bucket cover and set it up on top a 5 gal pail, which contains the small gas flames.!.!.!..It has a vertical wobble crank in the center coordinating the strokes in 90º sequences.!.!.!. I have also built three liquid piston hot air engines, which use water in a "U" shaped tube, sealed at the top, but connected with an air exchange tube,, hot on one side and cold dissipating on the other, with a heat saver copper mesh in the top middle, which is actually the real defining principle of the later Stirlings.!.!.! The 'U' tube is filled about half with water, and may have an insulating disc or ball floating on the hot side to keep water from boiling off.!.!.!. An inlet tube with check valves in it is soldered in the lower end, at a directional angle, which goes to a reservoir, or tanks of water to be pumped.!.!. As the water is destabilized, it flows or sloshes from one side of the tube to the other, causing the air above the water to alternately expand and compress, which pulls and pushes water in and out of the bottom inlet, causing water to flow when heat is applied with a flame on the hot side

[@enmiredbythelazy4401]

If you were to post some "how-to" videos of these, it would be helpful, even if you first tore them down and showed the assembly.

[@mikefochtman7164]

I remember trying to build a 'u' tube Stirling. (unfortunately, I had 'limited' success lol) Saw the plans in a magazine somewhere. Fell in love with the concept though. Want me to watch a video or read an article? Just mention 'Stirling engine' in the title or synopsis. lol

[@shad0wyenigma]

Amazing invention. Love it

[@stevezimmerman5644]

It'll be great to see this tech come to market. It will be a while before they are more widespread though. Early adopter tax is high and most engineers will shy away from specifying something new for that reason.

[@philwoodfordjjj8928]

I read an article (many years ago now) regarding research in Germany and hot air technology. To put it bluntly, this technology has been around for a hundred plus years. The 90°v twin is the way to go, and is what the German researchers used in conjunction with pellets to produce a CHP configuration, which supplied both heat and power on a domestic scale. Simple tech with a modern twist, with out faffing about.

[@flex-cx9bi]

Two companies is Sweden tries to launch Stirling engines for different applications, and both have been struggling with the technology. Azelio for renewable energy storage in aluminium. Very, very low efficiency so it will probably fail to reach a market. Swedish Stirling uses flare gases from melting companies (like Glencore) or oil producers to heat stirling engines to create electricity. The later might be successful because the source of the energy is basically free of charge and the fact that this technology have a positive effect on the environment since these gases are burnt anyways. Now the can be used to create electricity and be burnt more efficiently to reduce polution. So there is very few successful use of Stirling engine technology for commercial purpouses. Basically none.

[@philwoodfordjjj8928]

@@flex-cx9bi Try the Swedish navy's submarine technology: the sub was very successful in war games sinking Ronald Regan, and gess what? The stealth boats use Stirling engines when on patrol, which makes them difficult to detect. Moreover, I don't see what's so difficult about this known technology.

[@flex-cx9bi]

@@philwoodfordjjj8928 The two companies I'm talking about is off-springs from the company that supplied Stirling engines for some Swedish submarines. Same people and basically the same technology. A really effective Stirling engine is not easy to develop. There have been a lot of research to get the most out of the engines Azelio and Swedish Stirling use today.

[@philwoodfordjjj8928]

@@flex-cx9bi How much more effective do you want? Being hunted by the yanks and was never caught. Moreover, in Canada they have been used a part of a CHP system about the size of a wall mounted Combi boiler it's also used in the same way.

[@johnhayman5483]

two problems: - Helium leaks out of everything, seals are a big problem. - Hydrogen is to dangerous - Flammable (and also leaks out of everything)

[@paulsutton5896]

Helium is certainly not flammable. But it is a very limited resource, and its most important use is to make peoples' voices go funny, at parties.

[@PasajeroDelToro]

You can use plastic to safely store hydrogen without much leakage. PVC-U and PVC-Hi and PE pipes are suitable for 100% hydrogen, provided the gas is dry, according to a Dutch study.

[@polyjohn3425]

As mentioned, certain polymers can effectively contain hydrogen. While it adds an additional layer of complexity, stirling engines can be engineered for dry fit, low maintenance seals and a whole-system enclosure to ensure minimal gas leakage overall

[@entyropy3262]

Impressive ! Thx for sharing !

[@tekannon7803]

Great spreader of knowledge you!

[@ashoakwillow]

Another area of research is radiative cooling, as used for centuries in desert areas to make ice. Although deserts are life-threateningly hot during the day, they can be life-threateningly cold at night due to infra red radiation heading for the absolute cold of space. Even with cloud cover there is still appreciable cooling. So it should be possible to cool down thermal mass within a building during the night, and keep out unwanted energy during the day with external insulation. In principle a storage heater in reverse, with water being a useful medium for transfer and storage of energy, hot or cold.

[@heckyes]

I LOVE THIS CHANNEL

[@chaughten]

Great visual with the wiki pages!

[@AnonyMole]

Thought on a possible implementation... Floating, Stirling engine powered desalination plants. Imagine using the flat-black painted steel surface (the hot plate) of a large barge or raft, situated in the tropics. The cold plate would be cooled by the sea. One of the Stirling engines would be used to pump up much colder water from a few hundred meters down, that would help drive a cadre of other Stirling engines. Those would power reverse osmosis pumps to produce desalinated water. Those same engines might be used to drive electric generators for electrolysis generating hydrogen fuel. I wonder how much temperature differential is required to make such a scheme viable?

[@paxzin8501]

I think your idea is interesting, but there are some problems with Stirlings. While it might seem like a small temperature difference is enough to turn a fly-wheel, it really does not create a lot of horse-power. In a project like you are talking about, it would involve a massive set up, and a sufficiently high heat source. So much so, that it would actually be more practical to simply boil the water, and distill it, rather than pumping, and then using a reverse osmosis system. Not saying that it can't be done, but I don't know if the view is worth the climb on this type of project. The 'hot plate' simply wouldn't get hot enough (assuming that we are applying solar heat). The delta T might only get to about 20 deg. on average. Even under the best conditions, the solar heated hot plate might reach about 80 deg. F, but would lose a lot of it's heat with wind, water, overcast conditions, etc. In order to achieve the kinds of joules you desire, you'd need a hot plate in the 1000s of degrees. And this is based on a simple setup, that creates maybe a few gallons per day being created. I don't mean to come across like I'm poo-pooing on your idea, because I commend anyone that really digs into the capabilities and potential uses of a Stirling engine. A Stirling really isn't a powerful engine to start with, but it is still an 'engine' by definition. It converts physical energy into mechanical energy. I'd encourage you to pursue this idea, despite any of my criticism. And look around for other uses (size, heating requirement, torque, etc.), and see how even the smallest of projects, often require external heat sources that almost make it into a larger-sized gadget. (Stirling powered go-cart, or other aspects like that).

[@andrewmattox1233]

@@paxzin8501, That is a fair point. I would also point out, that in the tropics, a solar collector could be used. Fresnel Lens, comes to mind. A very high temperature could be achieved during the day. Comparing that temp to the ambient temperature of sea water, plenty of delta T. However, for desalination, those solar collectors could probably do more, by boiling the water, and distilling it. For other application, Solar Collector plus Sterling could be viable, though.

[@paxzin8501]

@@andrewmattox1233 I think you see my point, that it would take an addition of power, before a stirling would be able to produce any worthwhile effect on it's own. How much additional heat, what size/power can the stirling produce, and finally, how much desalinized water are we looking to collect and transmit. I know we'd love to think that a stirling engine alone has the capability using ambient water vs. ambient heat to be sufficient. First, we have to consider. Are we hoping to use the stirling as a 'pump' to push the water (as through hose from point A to point B), or are we trying to use the stirling to press the water through a filter for reverse osmosis? Overcoming the head pressure is our first obstacle, and a stirling should be able to do this, depending on it's size and volume capabilities, but even then, I don't expect the volume to exceed the horse power, of any other conventional pump assembly. Even if we were to use a fresnel, perhaps enclosed in a 'green house' type of bubble, perhaps with solar collectors, or solar heater assemblies, only then, might we see enough delta T, to overcome the head pressure, and potentially be able to cause the water to flow sufficiently through a hose, under a mild pressure. I think you can see, that with enough heat additions, it *could be* done. But at what cost? You'd probably have to have an assembly of stirlings, with matching heat collectors, that would match the size of an aircraft carrier before you could utilize the few 'solar hours' of the day to produce a few thousand gallons. Now sure, on that assembly, you could use 'fires' or steam engines, or other types of additional heat to make this extend past the solar hours, but again, it isn't something that a stirling on a floating flat-black painted pontoon, can do without excessive amounts of additional heat. Now if money is not in question, and the demand is, "Fresh potable water at any cost", then that would really be the only way such a system could be made with any semblance of 'practicality'. However, such a system would probably be more suited to being land-based, with a syphon extracting the sea-water, and taking it to a nearby facility, using steam engines to both 'boil' and distill the water, and then condensing it, without a need for a stirling. I know the allure of a stirling, I've spent many hours contemplating using it as a hot/cold air exchanger that works both forward and backward, depending on the time of year, and the desired, 'heating or cooling' of the air in summer/winter. Each time I hoped that the delta T, between the ambient air, and ground temperatures, would be sufficient. And yes, they work, as long as you don't expect too much air movement, unless you can add heat (or cold), but the stirling simply doesn't magnify power. Even using magnets, or additional gears will introduce higher friction, or more work to be required to both start and sustain any amplified use of a stirling to the point that it still remains at-best, a 99% efficient engine.

[@andrewmattox1233]

@@paxzin8501, Indeed, regarding the OP, I'm not sure a barge would be the way to go. *Unless it was a country like Singapore, which has very limited land, or other countries like that. In which case, due to Land Cost, putting things on a barge might make sense.

[@paxzin8501]

@@andrewmattox1233 I love the idea of using stirlings for desalinization. And I really wish that stirlings were up to the task. Without sufficient delta T, they really aren't going to be able to do it. If there were a way to add a tidal generator, wind power, or additional heat, we might have a small chance. And maybe something like this could be applied more to off-shore oil rigs, where there is a distinct separation from a 'hot plate' and the cold water below. Even without adding power, 40 deg F water, and potentially 100 deg F, solar heated platform, we're still dealing with a potential for only 60 deg F. This means that the stirling would have to be considerably large (or large combustion chambers) to utilize that 60 degrees. Then, we'd have to consider if we are going to set up the desal, on the surface of the water, or pipe it up to the oil rig platform. There are pros and cons to both. Less head pressure means the potable water could be collected and stored, to be plumbed or picked up by boat easily. But the risk of tides, or salt-water damage might cause the system to fail completely. And trying to use a stirling to pump it up to the rig platform, limits the amount that can be extruded severely. Even if we could get a stirling to properly convert 1 deg F, into 1 HP, (which I really don't think is possible), the unit would have to be on a massive scale. Whereas, a steam engine the size of a coffee can might could do it. Steam engines operate at around 75% efficiency. Car engines, about 15%, but both rely on internal combustion. The 'fuel' for the stirling is dependent on external temperatures alone. Even a diesel electric is about 30% efficient (for combustion alone), but by converting into 95% electricity, would probably be the best way to go. Consider those 'toy' or hobby stirlings, and how much it takes to pump water. That's done by adding an additional piston to the crank, which displaces a very small surface area, which can hopefully be eventually siphoned into a collection cell. In all of the time I've been waiting for someone to come up with a better Stirling engine/configuration, they all look good on paper, but fall short of any real value or longevity. Precise machining and changing temperatures do not bode well as a unit. Or the parts require new gaskets, or tweaking, to the point that they will pretty much always remain in the 'hobby' category. The only way to really crank up a stirling is to add energy, and if that's what it takes, then a solar-powered steam engine (with all of the additional sources mentioned earlier) would be better suited.

[@SlowHandism]

This is a great video. Thank you.

[@bernym4047]

A very interesting discourse on a very pertinent subject. I did wonder on what mechanical power source Fluid Mechanics are using and whether that has been accounted for in the efficiency calculations. I'm guessing that such a heat pump could be powered by wind, tide or water power. 🙏

[@raymondscbnetzer64]

Standard heat pumps will not work when temperature drops too low because the working fluid can not change from liquid to gas. Stirling cycle don't rely on changing from liquid to gas so they will keep on working when temperatures get bitter cold.

[@ryanjamesloyd6733]

This is very close to a thing I've been pondering- that being using the waste heat and unused cold of a traditional AC or heat pump to run a stirling engine to recoup some of the energy it takes to run the thing. Seems the same principle could be applied here with the addition of another stirling generator in the heat dispersal bit. I mean, you've got waste heat and cold at points in that system. Might as well put it to work.

[@Mrdevs96]

Yes you can see how it could work at scale, and it creates a feedback loop of free hot or cold energy

[@punkdigerati]

This concept is already in use in some utility and campus size power generation, but typically with organic rankine cycle engines instead of stirling, essentially the same concept of heat engine/pump reversibility as described in the video but with traditional refrigeration technologies.

[@lozl]

Fantastic! Very interesting indeed. I look forward to hearing more about this.

[@michaelstarkey9745]

Forrealness prevails

[@anders21karlsson]

Awsome video as always!!!!

[@bibliotek42]

I had a model of a stirling engine 25 years ago at college. It took me two days in the pre internet world to work out how it worked. Perhaps if I'd gone into engineering I might have got more out of my efforts. I am still amazed though by how fast the air heats/expands and cools /contracts. You would think after a few minutes it would have gradually transferred the heat from hot to cold and stop working. But that doesn't seem to happen. I seem to remember back then of hearing of a small boat on the Thames that was powered by a Stirling engine. They run very close to silently, so it must have improved the experience. No idea what they might have used for fuel.

[@poppasan1873]

Would the heat differential between the air and evaporative cooling of river water be enough?

[@bibliotek42]

@@poppasan1873 I don't know, but I wouldn't think so. My model would run in a room using a candle - just - but worked better if you used a hotter flame. But the temperature difference is important too. I would be highly surprised if it would work with outside air for heat and river water for cooling. This is more than 25 years ago, so it probably ran on gas.

[@revengefrommars]

9:19 I'm fairly sure that should be "Silicone Oil" instead of silicon.

[@durwoodmaccool890]

Back in the 70s Popular Science had a number of articles about a refrigerant free air conditioner system, that used air as the working fluid with a clever sliding vane style compressor / expander pump. Some of the energy used to compress the air was recouped by the expansion. I think it was called 'Rovac' or something similar but some casual googling hasn't turned up anything. Anyway I'm glad to see potential progress in this area. Thanks, Dave!

[@vaibhavahire4055]

Please answer this if possible. In my experience, sealing Helium is extremely difficult. If the expensive Helium gas leaks over time, refilling will be impractical for general consumer. Is the Helium trapped inside some cavity welded at all joints?

[@BinarySpike]

Helium is not expensive. Helium is a trash byproduct of the oil and gas industry.

[@toxicgaming816]

@@BinarySpike Actually, we are on the brink of a helium shortage crisis as the gas is so light it floats to the top of the atmosphere and gets picked of by solar wind into space. Some estimates that we will run out of helium in about 20 years.

[@sophieirisviel4100]

i think for the most part, the only place the helium would leak out is where the piston cylinders are, which i’m not sure about how to weld that sealed without other problems. as for the other people mentioning the helium shortage (or possible shortage or something) the guy in the video mentioned that hydrogen would also work extremely similarly to helium in the pump, but that probably comes with some fire risk

[@paulmaxwell8851]

Yes, most helium filled Stirling engines are hermetically sealed for this reason.

[@deanhough8993]

Wow, this was an excellent presentation. Nicely done!

[@Havox7]

This is very exciting. My concerns are how robust is this system. can those fins handle vibrations on a vehicle. I can definitely see this for large commercial buildings but maybe not vehicles. With the refrigerant with lower greenhouse effects i wonder how much of a place this will have with its added complexity. Just need the new refrigerant to not have a patent...

[@dereksimpson7959]

Thanks!

[@JustHaveaThink]

Thanks for your support. Much appreciated 😀

[@abizarlakdawalla4519]

there are highly successful commercial ultra low freezers based on the stirling cycle, called Stirling Ultracold.

[@tobiasL1991]

Very impressive stuff!

[@PeacefulWarriorAmanda]

Very informative!