A prototype for a new, quiet, thermoacoustic Stirling generator

Fortunes have been burned on all manner of Stirling engines including some pretty interesting variations on the theme such as Stirling engines with free pistons, liquid pistons and even more exotic versions. There are some interesting applications in fields that really need the features that Stirling engines offer (for instance: run in reverse they can be used as very good refrigeration engines). In America there were car manufacturers experimenting with them and in Europe Philips and DAF did a lot of work on this. But it all went nowhere and the reasons were varied, some related to seals ('rollsocks') to contain the working fluid, some related to the leakage between the two sides (Stirling engines become more efficient as the thermal delta between the two ends increases), some related to the eventual loss of working fluid and some because of fouling of the hot end because of incomplete combustion.

I've dabbled a bit in this with a solar powered Stirling motor (demonstration level, just a tiny unit, enough to serve as POC) and my own takeaway was that it can work but it is extremely hard to make it work economically. But to see sunlight turned into motive power without any intermediary is a really neat effect and it is still one of my projects that I'm most fond of.

>“The current thermoelectric conversion efficiency is about 28 per cent; with a hotter 600 degree thermal fluid, efficiency could reach 34 per cent,” he said. Such efficiency can rival that of steam turbines.

I was curious about that, but Wikipedia[0] says

>...in steam turbines, turbine entry temperatures are typically 565 °C (the creep limit of stainless steel) and condenser temperatures are around 30 °C. This gives a theoretical Carnot efficiency of about 63% compared with an actual efficiency of 42% for a modern coal-fired power station.

>...A modern, large electrical power station (producing several hundred megawatts of electrical output) with steam reheat, economizer etc. will achieve efficiency in the mid 40% range, with the most efficient units approaching 50% thermal efficiency.

[0] https://en.wikipedia.org/wiki/Steam_engine#Efficiency

> the absence of mechanical parts needing lubrication means the generator could exceed a decade of lifespan

This is something specific to their design, as far as I could Google Sterling Engines requires lubrication in general.

The explanation of thermoacoustic sounds like sci-fi:

> The engine converts heat into sound waves that resonate to form a stable sound field. These waves then drive a piston, which in turn generates electricity.

"Chinese scientists bring record-breaking Stirling generator to life while Nasa’s patent stays on paper" - Chinese posturing is funny. Are we in some kind of Stirling race?