In Europe today, more than half of the railway network is not electrified. Especially for regional transportation, diesel electric trains (called Diesel Multiple Unit: DMU) are then widely used. ALSTOM will release next year its new regional train called Regiolis. A Regiolis train may use up to 6 diesel engines of 338 kW each, which represent a total onboard power of about 2 MW. In this context, TRENERGY project aims at evaluating the interest of using a Rankine cycle in order to recover some lost heat and to increase the efficiency of the Diesel power packs. Rankine-cycle systems (and their derivatives like Organic Rankine Cycles, ORC) have already been investigated in the past for transportation means (train, trucks and more recently cars), but the fact is that up to now they have been mainly used for stationary equipments (power plants, heat recovery for boilers, furnaces and ovens…) or for heavy ships. For lighter transportation means, several scientific and technical bottlenecks still have to be addressed before Rankine systems may represent profitable devices for increasing energy efficiency. This is especially due to the transient behaviour of the heat source that characterizes this kind of applications. TRENERGY will focus onto: • the selection of the best control approach for an ORC system using a turbine in a varying heat source application, based on the analysis of the impact of component choice on control authority and system controllability, and on the design of a control strategy which can cope with the resulting limitations and make the most of the final architecture; • the design of a compact high-efficient low-power turbine, with a robust optimization of the internal fluid flow, and a strong focus towards high rotational speed, bearing systems and thermal management in order to improve the performance/cost ratio as well as the reliability of the component.; • the testing of a more environmentally friendly working fluid than current mediums tested for transportation applications like pentafluoropropane (R245fa) that may be banned in the next years. This joint work of ALSTOM, ENOGIA small business, ARTS ET MÉTIERS PARISTECH-DynFluid Laboratory and IFP Energies nouvelles will materialize at the end of the project through the testing, at the engine test cell, of a prototype Rankine system, equipped with a dedicated turbine, that may prefigure a future device to be fitted onboard high energy-efficient Diesel electric locomotives. As such, the project has strong industrial potential, and should lead to strategic advantages for the partners. As significant advances in research will be needed to attain the goals and obtain exploitable results, we expect that this project will not only increase competitiveness of the industrial partners, but also highlight the excellence of the academic partners.