Optimizing Size of Lithium-Ion Battery Combined with PV Generation

Lithium-ion batteries have been popular partners of photovoltaic (PV) arrays for more efficient utilization of solar energy. Although the lithium-ion battery price shows a continuously decreasing trend, it is still a challenge to deploy a cost-effective lithium-ion battery energy storage system (BESS) without financial incentives, especially for attaining higher profits. In order to maximize the profit of a lithium-ion BESS combined with a PV array, we proposed a two-stage stochastic optimization model that simultaneously determined the optimal size, charging and discharging schedules of the lithium-ion BESS. We considered that the PV-BESS could earn multi-source benefits by participating in the energy market, shaving the peak load demand, and alleviating power deviations from the forecast. Additionally, the capacity degradation of the lithium-ion battery was incorporated to estimate its lifetime and total revenue over its lifespan. The objective of our model is to maximize the BESS profit, i.e., total revenue minus cost. The BESS profit was formulated as a nonlinear function of the planning stage variable (battery size) and the operation stage variables (charging and discharging schedules). The optimization results suggested a trade-off between daily revenue and battery lifetime through optimizations of battery size and charging and discharging schedules.