Matt said the right things, I agree with him.
As for the video, it is another promotional offer to increase sales. Marketing.
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Stirling comes up now and again, especially from folks new to the forum. The collective wisdom, including from Matt above, is that Stirling is a dead-end, impractical engine design, at least for regular people living on Earth. But… if you REALLLY want to explore the rabbit hole…
This NASA paper from the 80s is about as comprehensive as you’ll get for the research of the time and more or less to the present day given light development since. The paper is as constructive on Stirling as you could be. It helps that it is NASA. They have an unlimited budget, access to exotic materials and state of the art manufacturing process. NASA is also focused on space applications where combustion is fraught.
As constructive as NASA was on Stirling Engines, they ended up using fuel cells, batteries and solar panels rather than Stirling engines. Take from that what you will.
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Yes, too far from DIY to be of interest for most of us. No junk spare parts, very unefficient and so on.
Swedish subs use Stirlings for silent propulsion. Also, I remember stirling gennies were still around in military service in the 80s. We never used them though.
I’ve seen some german company offering small Stirlings for home use in resent years - but with less than 1kW electrical output. I don’t know if they are still around.
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What heat source do they use? You can’t have a bonfire under the water.
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Haha! No, they use diesel and liquid oxygen. There are several videos on YT about those Stirling stealth subs.
Ordinary boats would probably work very well converted to wood. Subs - not so much 
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Yes, or from Australia. Sunmachine was maybe German, bankrupt. The small 1 kW you are refering too is a scam too. It cant take intermitant loads, it has to run constant. That means you are very energy hungry on the thermal site. 1 kWe doesnt help in such a situation and those people often have one or more extra boilers. Nothing eco or efficient about that.
Phillips tried the Stirling for ever and didnt succeed. Well, a backyard DIY wil do bether of course. Ded end road.
I have been thinkering forever and maybe it will go on forever. Tried the turbo route but that is a dead end too. Turbine has to be big for efficiency, to much heat losses if they are small. At the end there is only one practical solution: Mr Steve’s topic, small ICE. Left or right, that is the place you will end.
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Fascinating. But l dont realy get it. Why not use a fuel cell then, they are way more efficiant and literaly noiseless?
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KristijanL. I’d say it was because of the time-frame of the adaptation.
Stirling was and is a thermal-mechanical engine. Without the combustion “booming”“ringing” of an IC engine. Without the highs-speed whining of turbines. As gas turbines very fuel and air gobbling. As steam turbines really needing the make silent pressure power of nuclear systems. Military submarines are the needs to be true “Silent Service”.
Fuel cell development back in the mid-cold war era still had a long way to go. Even still with now refined and available rare metals fuel cell reamaing cost-plus specialists to implement and use. Still regeneration from internal build ups seems to be a hanging up problem. Needing to be pre-heated; then in high demand applications cooled; hang ups too.
Toyota, BMW and others still after decades not satisfied with releasing them for general use as of yet.
All . . . “I think”.
Steve Unruh
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Kristijan! Steve may be close to the thruth. Myself, I can only add - I have no idea Maybe a combination with heavy batteries would risk the thing to sink 
Miltary gadgets aren’t my cup of tea.
I think Swedish Atlas Copco was the closest to success. Still far from it.
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Stirling is a dead end road because of efficiency. There are a couple of other things I have seen in the last 10 years. One was an engine based on the Carnot cycle but it was something cycle, I don’t recall the name. That company went out of business.
There are two groups that annouced something similar but simpler. One was out of Atlanta, and I suspect that one is going no where. it was a black phycist from I think the jet propulsion labs.
Another one is the guy from I think university of Utah, and he was converting heat into sound and I believe then sound to electric. (sound into electric is essentially a microphone.)
Another one is where they take the electromagnetic heat waves and use essentially an antenna to capture the heat, the main issue with that is it creates high frequency ac, that has to be rectified, and you essentially have to get a diode as smaller then the antenna, work at low currents, and react very fast.
I just saw an article recently about similar technology, but I didn’t read the article, just the headline.
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Sean, you are thinking of Lonnie Johnson, inventor of the super soaker.
His TEC (Thermo-electric converter) is really neat, but has two problems. The first is that it looks like a fuel cell at first presentation, even though it isn’t and that makes for a harder sale. The second is a fuel cell type problem related to materials. Basically he needs a material with very specific properties and none exist that are quite good enough. I hope he finds success with his TEC. It is really clever.
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Seems like Lonnie started off like many of us. Where are our millions?
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That is part of what made it look like a fake. He was looking for funding and VC, and there was a lot of minority rhetoric that went with it when I started looking at his company. I don’t know whether that was because of the BLM stuff, whether it was trying to get minorities interested in science or he was just trying to loot money from the government.
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