A Dispatch Optimization Model for Hybrid Renewable and Battery Systems Incorporating a Battery Degradation Model

Abstract

Abstract Recently, there has been an increased level of integration of renewable energy systems in existing power grids. Lack of integrated dispatch models has led to waste in power produced. This paper proposes a mixed-integer linear optimization model for hybrid renewable-generator-plus-battery systems, with the objective of maximizing long-term profit. Prior studies have revealed that both high and low state of charge (SOC) of the battery is detrimental to its lifetime and results in reduced battery capacity over time. In addition, increased number of cycles of charge and discharge also causes capacity reduction. This paper models these two factors with a constraint relating capacity loss to the SOC and number of cycles completed by the battery. Finally, the loss in capacity is penalized in the objective function of the optimization model, thereby indirectly penalizing high and low SOCs and frequent cycling. To overcome the computational difficulties of achieving global optimality, a rolling time horizon optimization approach is used. By incorporating battery degradation in the real-time model, the model is capable of maximizing the profits from the power dispatch to the grid while also maximizing the life of the battery. This paper exercises the model by assessing sample generator time series profiles with a range of battery capacities. The results demonstrate that the battery lifetime is extended in comparison to conventional models that ignore battery degradation in dispatch decisions. Finally, we analyze the relationship between operational parameters of the battery and the capacity fade.