In this video I show you the beginning of the investigation into which Stirling engine concept could become the successor to the Rhombic Stirling.

The Stirling engines I have built are too complex for energy selfsufficiency and therefore too expensive and maintenanceintensive.

I would now like to extensively investigate which engine concept would be best for my next project.

The Thermal Lag Engine represents a mechanical simplification of common Stirling engines.

It uses only a single piston which avoids a complex linkage mechanism.

The piston is also located in a cooled volume which makes sealing much more easy and increases endurance properties.

The Thermal Lag Engine is still a relatively new invention which has not been researched much and offers a lot of potential for improvement.

The Thermal Lag Engine was patented in 1995 by Peter Tailer.

It consists of a hot space where the heat is supplied to power the engine and a cooled cylinder in which the piston moves.

The single piston in the cooled part of the engine simplifies sealing and endurance characteristics.

The simple linkage mechanism causes little friction and can be built very small, which simplifies any pressure charging.

The hot heat exchanger typically has a much smaller diameter than the cooler and is therefore much cheaper and easier to build.

In contrast Thermal Lag Engines are still in the research and development phase and have not yet been applied in practice.

There are only a small number of studies relevant to the TLE reported.

Fundamental knowledge investigation of the TLE is lacking and the physical understanding is insufficient.

Colin D. West and Peter Tailer claim that the main effect of the TLE is the bulk motion of the fluid from the hot to the cold space and back which leads to the heat transfer that drives the engine.

Allan Organ explained the engine from a completely different perspective.

He identified the connecting space between the hot and cold spaces of the TLE as a pulse tube.

Further analysis revealed that both theories are not explicitly contradictory, but represent different implementations of the same effect.

To improve engine performance, the driving phenomena needs to be fully understood.

Numerical models have shown that the PV diagram is much narrower than that of a traditional Stirling engine.

The TLE thus has a relatively poor efficiency and thermodynamic performance.

To increase the efficiency the design of the engine based on fundamental knowledge and physical insight becomes more essential.

Different approaches such as the analytical method, the thermodynamic model, CFD (Computational Fluid Dynamics) and even a neural network and generic algorithm were used to calculate optimal performance and efficiency.

Nevertheless, the most powerful experimental TLEs known to me only have a maximum output of 2545 watts.

The complex interrelationships of the operating principle do not make the design easy.

In addition, the design of the heat exchangers is not conducive to intuitive development, making experimental optimization difficult.

There is still a lot of room for performance improvements here, but the still very unexplored optimization methods make a promising development difficult.

The TLE offers many simplifications and advantages but for me the potential for a selfbuild is difficult to assess and therefore I don't think the TLE would be a good choice.

What do you think about the Thermal Lag Engine, please let me know and write it in the comments!


Thank you very much for your attention.


Thank you so much for the TLE artwork from my wonderful daughter Anna


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