Some members of the Stirling Engine Society have been playing about with various designs of Thermal Lag Engine. I'm hoping that there will be some examples at the midlands exhibition later this month, to have a tinker with. (I do know that one of the people who has been building these devices will be there.)

There have been various theories suggested for how these odd little engines work - some slightly more feasible than others. But there still seem to be a number of unknowns. I suspect it is high time that thermal plasmonics was thrown into the mix - just to confuse matters still further

If you google around, you can find examples of some thermal lag engines online - along with some videos. The challenge (as always) is to improve the efficiency of the current devices - so that they might find more of a use than just being cute.

I also see that our friend Allan Organ is now getting in on the act - with his latest (unaffordable) textbook.

There was a Stirling Engine rally in Hereford last Sunday. Here is a short video (under 3 minutes) of some of the engines on display.

Quote from Frogfall

I've long suspected that the designers of regenerative "Caloric" engines, such as John Ericsson (1803-1889) believed that Caloric possessed some form of inertia. I don't think Ericsson (or his contemporaries) could quantify it - but it might explain some of the design features of the early engines, which seem slightly bizarre today (with our currently accepted thermal theories).

Just thought I'd post a little update.

The sudden shifting of heat along a heated bar, plunged in water, could be amenable to calculation through variations of the Drude model for thermal conductivity.

Note that the model involves laws (such as the Wiedemann-Franz law) rather than full theory, however it does give a route to introduce such concepts as phonons and "thermal inertia".

China tests a Stirling cycle power converter in orbit

They have used twin free piston units, horizontally opposed and possibly electrically synchronised - in an effort to overcome balance issues. Heat is from radioactive decay - but the article below doesn't mention the source type (The previously abandoned NASA unit, above, used Plutonium-238).

If fact, the Phys.Org article is ridiculously dumbed-down and bizarrely compares the generator to a hydroelectric dam rather than to other heat engine generators or solid state thermoelectric systems.

China tests a Stirling engine in orbit

The China National Space Agency (CNSA) has made considerable progress in recent years with the development of its Long March 5 (CZ-5) rocket and the completion…

phys.org