High efficient energy conversion concept based on the integration of energy recovery devices, energy storage and engine auxiliaries electrification on a Natural Gas heavy duty engine.The energy recovery strategy is based on two mainstreams:• recovery of a portion of the kinetic energy thanks to the adoption of a belt driven generator• recovery of the waste heat with an energy cascading approach: thermoelectric generator operating at high temperature subsequent turbo-generatorThe system includes an appropriate energy storage system and electrified auxiliaries such as coolant and oil pumps, auxiliary turbo charger, air and air conditioning compressors.The engine control strategies will be tuned and optimised (combustion, cylinder de-activation, …) to maximise the efficiency of the energy recovery and re-use subsystems and the benefit the auxiliaries electrification. Finally the combination of the electric auxiliary turbocharger and the abortion of a liquid cooled charge air cooler will be implemented as part of the whole strategy to optimise the engine efficiency.The Project results will be experimentally demonstrated at bench level (engine test rig) while the benefits of the engine down-sizing, combination of control strategies and the reference mission(s) and integration with hybrid or hybrid-like powertrains will be evaluated at vehicle level thanks to advanced dynamic models.The industrial feasibility, the portability on diesel engine and the cost estimation are also included in the as well as a preliminary packaging study to assure the on board integrability.The Project most important outcome will be a new powertrain concept based on a combined energy recovery, storage and re-use system integrated and optimised with the engine system and controls.The project will answer to the request to achieve an efficiency at vehicle level well above 50% at acceptable cost.