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Auxiliary engine allows trucks to convert their own waste heat into power

EU-funded scientists developed unique engine technology that could capture and use waste heat from the exhaust pipes of millions of heavy-duty vehicles. The new system could save vehicles hundreds of litres of fuel and reduce CO2 emissions by 10 %.


Internal combustion engines powered by petroleum products will not be scrapped anytime soon. Such engines are expected to survive in heavy-duty vehicles for at least 20 more years. Although modern engine systems are considerably more efficient than their predecessors, around 60 % of the energy they produce goes to heat rather than power. By capturing this energy and putting it to use, WHIITE’s new prototype engine promises large gains in power conversion and reduced fuel consumption.

Bringing waste heat recovery systems to heavy-duty transport

Engineers pioneered the design of a small auxiliary engine, easily integrated into existing engines (trucks and tractors), that can create additional mechanical power without emitting gases. “Our technology is based on a unique patented thermodynamic open cycle using ambient air as a working fluid. Thanks to a heat exchanger and a hot air machine, the engine converts thermal energy from the conventional engine’s exhaust gases into mechanical power. Fuel consumption and gas emissions can drop by 10 %,” notes Frédéric Thévenod, coordinator of the WHIITE project. Conventional internal combustion engines burn different kinds of fuels – petrol, natural gas or biogas – to run a shaft that provides mechanical energy to move the vehicle. “Our new engine prototype is a very simple machine that uses only heat as a fuel. It transforms heat from exhaust gases into pressure in the cylinder, which pushes a piston; a crankshaft then turns the reciprocating motion of the piston into rotational motion. The operation resembles that of a pressure cooker,” adds Thévenod. The new engine does not add any weight to the vehicle – it replaces the air compressor and the exhaust gas recirculation cooler.

Next steps to increase the market potential

Theoretically, WHIITE’s novel system could work with all trucks and tractors. Production costs are low: the engine is built with conventional materials that mitigate the need for electronics. Using just ambient air, the engine requires no maintenance for 1 000 000 km. The only constraint is that the heat captured must be at least 500 degrees Celsius. Depending on the price of fuel, the payback period can be as short as 2 years. “With the completion of a successful prototype, we have made a major step towards addressing a leading problem in energy use – the waste of more than half of the energy produced by heavy-duty vehicles,” notes Thévenod. However, much engineering work remains for waste heat recovery technology to yield a positive impact on trucks. “Making the engine more compact and adapting its operation to lower temperatures (to match the temperatures of the trucks’ exhaust gases) are good first steps toward this direction.” For now, WHIITE’s technology can be used in power generation systems in energy applications, but in the next few years, it is expected to enter the transport market. The project's ambition is to provide a one-stop reference technology for waste heat recovery in heavy-duty vehicles. “The development of a breakthrough engine of any kind is always a big challenge. Introducing it to a very competitive mass market is another one. The first step has been made and we should now succeed in scaling up and further improving the technology,” concludes Thévenod.


WHIITE, engine, power, waste heat, truck, heavy-duty vehicles, tractor, waste heat recovery, exhaust gases, internal combustion engines

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