In the European Industry, 275 TWh of thermal energy is rejected into the environment at temperatures beyond 300 °C. To recover some of this wasted energy, bottoming thermodynamic cycles using supercritical carbon dioxide (sCO₂) as working fluid are a promising technology for the conversion of the waste heat into power. CO₂ is a non-flammable and thermally stable compound, and due to its favourable thermo-physical properties in the supercritical state, can lead to high cycle efficiencies and a substantial reduction in size compared to alternative heat to power conversion technologies. In this work, a brief overview of the sCO₂ power cycle technology is presented. The main concepts behind this technology are highlighted, including key technological challenges with the major components such as turbomachinery and heat exchangers. The discussion focuses on heat to power conversion applications and benefits of the experience gained from the design and construction of a 50 kWe sCO₂ test facility at Brunel University London. A comparison between sCO₂ power cycles and conventional heat to power conversion systems is also provided. In particular, the operating ranges of sCO₂ and other heat to power systems are reported as a function of the waste heat source temperature and available thermal power. The resulting map provides insights for the preliminary selection of the most suitable heat to power conversion technology for a given industrial waste heat stream.

Alternative vehicle powertrains (hybrid, hydrogen, electric) are a right answer to the emissions problem in very congested urban areas. The most effective alternative choice is surely represented by fuel cell vehicles. The design and optimization of this kind of powertrain can take a great benefit from mathematical models which include auxiliary management and control strategies of the energy fluxes: the use of a virtual platform limits the expensive and time-consuming experimental activity.The Authors present a lumped parameter mathematical model of a hybrid vehicle fed by a fuel cell pack. The propulsion system (fuel cell and battery) is accurately designed according to energy balancing. The mechanical power is given by an electric machine, whose behavior as alternator allows the energy recovery during braking. This aspect is treated with particular care (inside the overall vehicle and powertrain modeling). Vehicle's stability and safety has been also verified before recovering energy, re-modulating the braking action