Yorick Ligen
Thermodynamics and heat engines are the core disciplines which enabled the development of the thermo-industrial society during the 20th century. Liquid hydrocarbon fuels are one of the easiest and most convenient solutions offered by the thermophysical constraints of our world. However, an alternative to these dense energy carriers is required to enable a transition to a low carbon transport sector. Climate change mitigation, local air pollution reduction and energy independency are some of the key advantages that hydrogen fuel cell and battery electric vehicles can bring in this context.
Beyond a shift from fossil fuels, the entire value chain, from primary energy to powertrains must be reconsidered, redesigned and redeployed to include renewable energies, robust powergrids, charging stations and electric powertrains. The prominent role of the infrastructure in terms of energy efficiency is demonstrated in chapter 2, introducing a grid to mobility segmentation for life cycle studies. In addition, the shortcomings of local and off-grid solutions are highlighted in the same chapter. Nevertheless, the grid integration also requires innovative solutions to comply with the physical constraints of current networks. In particular, the role and the sizing of stationary buffer batteries is detailled in chapter 3. The stochastic nature of charging events is used to develop a battery sizing algorithm including grid tie constraints.
This research was intrinsically motivated by the perspective of infrastructure operators. A full scale demonstrator is at the core of the scientific questioning of this thesis. The design, the construction and the operation of a grid to mobility demonstrator is reported in chapter 4. Including a 200 kW / 400 kWh Vanadium redox flow battery, a 50 kW alkaline electrolyser, and a hydrogen refueling station, this demonstrator enabled a better understanding and characterization of process engineering, of control and programming and of electrochemical phenomenons. In particular, the data analysis on the electrolysis side and purification solutions are reported in chapter 5. Finally, the intrinsic characteristics of air driven gas boosters, a robust small scale compression solution, are analyzed in chapter 6 and the challenges for a full scale hydrogen mobility are discussed with an economic and logistics perspective.
EPFL2020
