MILP based optimization tool for PV and BESS planning in railways: a case study in extensive market analysis

The integration of photovoltaic plants (PVs) and battery energy storage systems (BESS) into railways traction power substation (TPSS) is attracting increasing attention. The ample space, that is generally available in a TPSS, allows installing large PVs but the uncertainties in policy and market frameworks represent barriers for investments prompting operators to explore planning methodologies that maximize revenues and assess the impact of different market conditions. This paper presents a MILP-based optimization tool for sizing PV and BESS supplying a TPSS assuming a dynamic variation of the energy price for revenues and cost calculation. The tool maximizes the annualized net profit of self-producers by balancing the revenues from energy production against the investment costs for the equipment installation. The proposed tool is validated with a dataset collected from a real TPSS and exploited for an extensive market analysis simulating 11,250 economic scenarios. Considering different equipment costs alongside fluctuating energy prices, the extensive market analysis provides insights even about disruptive changes in the policy framework, the technological landscape and the energy market. The obtained results show the significant potential for combining TPSS with PV and BESS, pointing out that BESS is partially convenient if its unitary cost ranges from 80 to 200 k€/MWp.