4 ms·

A prototype for a new, quiet, thermoacoustic Stirling generator

68 points by g42gregory 3y ago

hurtuvac78 3y ago
https://archive.is/yjpei https://archive.is/yjpei
- neonate 3y ago
  https://web.archive.org/web/20231117055525/https://www.scmp.com/news/china/science/article/3240924/chinese-scientists-bring-record-breaking-stirling-generator-life-while-nasas-patent-stays-paper https://web.archive.org/web/20231117055525/https://www.scmp....
deleted 3y ago
[deleted]
fbdab103 3y ago
>“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 https://en.wikipedia.org/wiki/Steam_engine#Efficiency
- groestl 3y ago
  The next paragraph is also worth citing (it probably applies to the thermoacoustic Stirling engine as well) "It is also possible to capture the waste heat using cogeneration in which the waste heat is used for heating a lower boiling point working fluid or as a heat source for district heating via saturated low-pressure steam." This way (district heating), the power plant in my city achieves 86% overall efficiency.
- throwaway81523 3y ago
  Are those measuring the same thing? Does 63% Carnot efficiency mean 63% of the efficiency of the ideal Carnot cycle, which is determined by the temperature difference and is always less than 100% of the heat energy extracted from the fuel? Or does it mean the amount of fuel heat that is converted to motion? 63% would be fantastically high, I thought.
  - bonzini 3y ago
    63% is the Carnot efficiency between 565°C (838 K) and 30°C (303 K)
tromp 3y ago
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.
- xnx 3y ago
  I believe the James Webb telescope cryocooler is pretty close to the opposite of this device: https://webb.nasa.gov/content/about/innovations/cryocooler.html https://webb.nasa.gov/content/about/innovations/cryocooler.h...
2rsf 3y ago
> 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.
- adrian_b 3y ago
  Normally all thermoacoustic Stirling engines do not need lubrication, which is one of their main advantages, because they do not have a piston of traditional form, but they have something similar to the membrane of a loudspeaker or, better said, like the membrane of an electrodynamic microphone, which oscillates back and forth, moved by the gas, and the movement induces electric currents in a coil, either a stationary coil or a moving coil attached to the oscillating membrane. The traditional Stirling engines have pistons that move in cylinders, so they need seals and lubrication (though there are designs with dry gas seals, which do not have lubrication with oil).
- taneq 3y ago
  It's kind of a weird claim. If it doesn't need lubrication then it should last forever without maintenance. If it's a sealed system using a lubricant that lasts a decade or so, then maybe it'd make sense. Otherwise it sounds like whispers.
  - naasking 3y ago
    Thermoacoustic Sterling engines don't need lubrication because they don't have pistons: https://youtu.be/abswNCqnMRQ?si=jYIZnUG83ZQnQ-Ru https://youtu.be/abswNCqnMRQ?si=jYIZnUG83ZQnQ-Ru The membrane may eventually need replacing though.
jacquesm 3y ago
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.
- jstanley 3y ago
  Can you share any pictures or videos of your engine?
  - jacquesm 3y ago
    I still have pics of the concentrator and I'm pretty sure we should have a single print of the running motor but no video. This was in 2006 or so. The fun bit was a crystalline fiber to transport the light from the collection point to the motor, and an improvised wrapper around the hot side of the motor that allowed to inject the light into the cavity where the hot piston was located. We had to make it black to get it to work. I'll see if I can find that picture but no promises. I still have the little engine but I no longer have the mirrors or the fiber.
- pge 3y ago
  One of the successful applications of stirling engines I find interesting is on diesel submarines where stirling engines are used to extend submerged running time substantially. An example is https://en.m.wikipedia.org/wiki/Gotland-class_submarine https://en.m.wikipedia.org/wiki/Gotland-class_submarine
genman 3y ago
"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?
- SiempreViernes 3y ago
  If you listen to the noises coming from DC the US is in principle competing with China everywhere, as the official strategy is "primacy" over China. Consequently calling something a China-US race is very popular, and is used for basically anything.

68 points by g42gregory 3y ago

hurtuvac78 3y ago

https://archive.is/yjpei https://archive.is/yjpei

neonate 3y ago
https://web.archive.org/web/20231117055525/https://www.scmp.com/news/china/science/article/3240924/chinese-scientists-bring-record-breaking-stirling-generator-life-while-nasas-patent-stays-paper https://web.archive.org/web/20231117055525/https://www.scmp....

deleted 3y ago

[deleted]

fbdab103 3y ago

>“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 https://en.wikipedia.org/wiki/Steam_engine#Efficiency

groestl 3y ago
The next paragraph is also worth citing (it probably applies to the thermoacoustic Stirling engine as well) "It is also possible to capture the waste heat using cogeneration in which the waste heat is used for heating a lower boiling point working fluid or as a heat source for district heating via saturated low-pressure steam." This way (district heating), the power plant in my city achieves 86% overall efficiency.
throwaway81523 3y ago
Are those measuring the same thing? Does 63% Carnot efficiency mean 63% of the efficiency of the ideal Carnot cycle, which is determined by the temperature difference and is always less than 100% of the heat energy extracted from the fuel? Or does it mean the amount of fuel heat that is converted to motion? 63% would be fantastically high, I thought.
- bonzini 3y ago
  63% is the Carnot efficiency between 565°C (838 K) and 30°C (303 K)

tromp 3y ago

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.

xnx 3y ago
I believe the James Webb telescope cryocooler is pretty close to the opposite of this device: https://webb.nasa.gov/content/about/innovations/cryocooler.html https://webb.nasa.gov/content/about/innovations/cryocooler.h...

2rsf 3y ago

> 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.

adrian_b 3y ago
Normally all thermoacoustic Stirling engines do not need lubrication, which is one of their main advantages, because they do not have a piston of traditional form, but they have something similar to the membrane of a loudspeaker or, better said, like the membrane of an electrodynamic microphone, which oscillates back and forth, moved by the gas, and the movement induces electric currents in a coil, either a stationary coil or a moving coil attached to the oscillating membrane. The traditional Stirling engines have pistons that move in cylinders, so they need seals and lubrication (though there are designs with dry gas seals, which do not have lubrication with oil).
taneq 3y ago
It's kind of a weird claim. If it doesn't need lubrication then it should last forever without maintenance. If it's a sealed system using a lubricant that lasts a decade or so, then maybe it'd make sense. Otherwise it sounds like whispers.
- naasking 3y ago
  Thermoacoustic Sterling engines don't need lubrication because they don't have pistons: https://youtu.be/abswNCqnMRQ?si=jYIZnUG83ZQnQ-Ru https://youtu.be/abswNCqnMRQ?si=jYIZnUG83ZQnQ-Ru The membrane may eventually need replacing though.

jacquesm 3y ago

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.

jstanley 3y ago
Can you share any pictures or videos of your engine?
- jacquesm 3y ago
  I still have pics of the concentrator and I'm pretty sure we should have a single print of the running motor but no video. This was in 2006 or so. The fun bit was a crystalline fiber to transport the light from the collection point to the motor, and an improvised wrapper around the hot side of the motor that allowed to inject the light into the cavity where the hot piston was located. We had to make it black to get it to work. I'll see if I can find that picture but no promises. I still have the little engine but I no longer have the mirrors or the fiber.
pge 3y ago
One of the successful applications of stirling engines I find interesting is on diesel submarines where stirling engines are used to extend submerged running time substantially. An example is https://en.m.wikipedia.org/wiki/Gotland-class_submarine https://en.m.wikipedia.org/wiki/Gotland-class_submarine

genman 3y ago

"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?

SiempreViernes 3y ago
If you listen to the noises coming from DC the US is in principle competing with China everywhere, as the official strategy is "primacy" over China. Consequently calling something a China-US race is very popular, and is used for basically anything.