This paper proposes a methodology for optimal operation of railway electric energy systems considering renewable energy sources (PV panels and wind turbines), regenerative braking capabilities and hybrid electric energy storage systems (ultracapacitors and batteries). The uncertainties associated to renewable energies are taken into account through a scenario tree approach. All these elements are integrated into a multi-period AC optimal power flow problem. This problem is then cast as a large-scale nonlinear optimization problem. The aim is to study the potential for energy and economic savings of the railway operation as well as energy storage systems behavior. A real case study is analyzed for a Spanish high-speed railway line. Results are reported for several cases comparing four different operation modes.

The expansion on the use of Electric Vehicles demands new mechanisms to ease the charging process, making it autonomous and with a reduced user intervention. This paper reviews the technologies applied to the wireless charge of Electric Vehicles. In particular, it focuses on the technologies based on the induction principle, the capacitive-based techniques, those that use radiofrequency waves and the laser powering. As described, the convenience of each technique depends on the requirements imposed on the wireless power transfer. Specifically, we can state that the power level, the distance between the power source and the electric vehicle or whether the transfer is executed with the vehicle on the move or not or the cost are critical parameters that need to be taken into account to decide which technology to use. In addition, each technique requires some complementary electronics. This paper reviews the main components that are incorporated into these systems and it provides a review of their most relevant configurations.

The problem of optimally sizing hybrid energy storage systems (HESS) installed in electric railway systems, considering the effect of regenerative braking is studied in this paper. HESSs combine traditional batteries and newly developed ultracapacitors, taking advantage of the high energy capacity of batteries and of the flexibility and ability to capture high power density of ultracapacitors. A novel mixed integer linear programming formulation that includes the counting of battery cycles is presented. Some particularities of battery operation are included in the model, like the dependence of its performance on the number of cycles and the depth of discharge (DOD). Results are reported first for a illustrative case study, allowing us to perform sensitivity studies for several parameters; results are also reported and for a larger case, closely resembling the problem faced by railway energy systems planners and operators.