A High Energy Density Power Generator


There is a great need for small compact generators with: i) high energy-density, ii) significantly improved efficiency, and iii) a low noise and vibration signature. This high energy-density rotary combustion generator is perfectly balanced and can store kinetic energy.


This is a high energy-density rotary combustion generator designed to produce electrical power from 1 kW upwards. The generator has only two moving parts comprising two opposed-toroidal-pistons and a matching cylinder. The pistons are connected by a torsion spring to allow timed-combustion to generate mechanical resonance.

Small conventional IC engine generators can never be dynamically balanced, making them noisy and, when not in use, they cannot store kinetic energy. This design is perfectly balanced, eliminating all side-thrust and reducing ring-pack friction for improved efficiency, which in turn produces a much lower noise and vibration signature. When not in use the design can store kinetic energy as a flywheel.

A High Energy Density Power Generator

The High Energy Density Power Generator showing the toroidal opposed-pistons (the toroidal cylinder and the torsion spring are not shown).


Potential applications

The generator could be applied anywhere where small, high energy density generators are needed. It could be used as a Range Extender for Hybrid Electric Vehicles, possibly using zero-carbon fuels. It could also be suitable as a low-noise high-efficiency generator for the domestic Combined Heat and Power market. It can also store kinetic energy to improve the regenerative braking efficiency of Hybrid Electric Vehicles.

IP status

The technology is protected by granted patents in UK and Germany.


  • [1] J. F. Dunne, (2010) Dynamic Modelling and Control of Semi-Free-Piston Motion in a Rotary Diesel Generator Concept ASME Journal of Dynamic Systems, Measurement, and Control, Vol 132 (5), (September), (12 pages).
  • [2] Kigezi, Tom Nsabwa and Dunne, Julian (2017) A model-based control design approach for linear free-piston engines. Journal of Dynamic Systems, Measurement and Control, 139 (11). ISSN 0022-0434

The technology has also been presented at a number of conferences, including at the 13th Motion and Vibration Control conference at the University of Southampton in 2016, at the International Conference on Dynamical Systems in Poland in 2017 and at the Conference on Control Technology applications in Copenhagen, Denmark in 2018.

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