Thermal Engine and Climate Change Challenge

Combustion engines have dominated power generation and propulsion in the transport sector since the beginning of the industrial era. With environmental concerns, first linked to local urban pollution and then to the global greenhouse effect, "clean" energies are tending to relegate combustion engines to the category of obsolete technology. We need to analyze the operation and potential of these machines, born of an era and a society in which environmental concerns were of secondary importance to current and future societal and industrial objectives.

Faced with technologies such as wind power, solar power, nuclear power and the direct use of electricity, which seem to have immediately solved the issues linked to polluting emissions and the greenhouse effect, the internal combustion engine suffers from the characteristics that the industry has been willing or able to give it: a technology that is inexpensive, reliable and requires little in the way of precious materials, but which is often poorly efficient, leading to pollution and climate disruption. In what follows, we propose to study the potential of internal combustion engines to meet the energy efficiency and low carbon footprint requirements of the future, by highlighting the advantages and disadvantages of the internal combustion engine, and distinguishing them from the design choices inherited from the economic criteria of the past.

For an engine using combustion as a heat source to generate motion, energy efficiency is directly linked to gas emissions, whether greenhouse gases and/or pollutants. The best engine from an ecological point of view is therefore first and foremost the one that generates the lowest emissions for a given power output, and therefore makes the best use of fuel in the transformation of chemical/calorific energy into motion.

In a broader sense, the best engine is one that consumes the fewest resources and generates the fewest emissions for a given power output, not only during use but also during production, including the production of fuel, lubricants, coolant, accessories and all other components required for production and operation.

Energy efficiency, i.e. the ratio between the production of useful motion and fuel consumption, is therefore crucial when considering the future of an engine. The concept can be extended to other ratios, such as that of pollutant emissions or that of fossil or mineral resources as a whole.

Depending on priorities, engines with low pollutant emissions could be preferred for urban use, and engines with low greenhouse gas emissions could be preferred for heavy transport over long distances.

In order to shed light on current compromises and the potential for...