Optimal centralized renewable energy transfer scheduling for electrical vehicles

Plug-in hybrid electrical vehicles (PHEVs) that can use both gas and electricity have the potential to greatly reduce air pollution from vehicles. In this paper, we consider a bus system where the buses are PHEVs, and some charging points at the bus stops are connected to a central energy storage (CES) via underground cables. The CES is charged by renewable energy sources and the buses get electricity from the CES (and thus use renewable energy) through the charging points. Since the CES has limited capacity, the energy generated by the renewable energy sources will be wasted when it exceeds the capacity of the CES. On the other hand, since each bus has a battery, the buses naturally form a distributed energy network that can help to store the energy from the CES to reduce energy waste. We formulate and solve an optimization problem that determines the amount of energy that a bus charges or discharges at the charging points to improve effective load carrying capability at the CES while maximizing the total amount of renewable energy used by the buses. Simulation results demonstrate that our approach significantly outperforms a baseline strategy. In addition, our approach uses the batteries of the buses efficiently, and hence only a small battery at the CES is sufficient to realize most of the gains.