Cost-benefit analysis of battery storage investment for microgrid of Chalmers university campus using OPF framework

Paper in proceeding, 2017

This paper presents a cost-benefit approach for evaluation of battery energy storage (BES) options to be installed in the electrical distribution grid of Chalmers University from the microgrid perspective. The evaluation is based on a multiperiod ac optimal power flow model applied for microgrid, which is referred to as the micro-OPF, with the objective function being the total grid operation cost. The model is developed for the real 12 kV grid of Chalmers. The micro-OPF is used as the calculation tool for the cost-benefit analysis where the benefit-to-cost ratios (BCR) of battery options in the grid in a year over the annualized cost of battery are evaluated for various options of battery sizes in the grid. The best location for the battery storage was however determined with the minimum loss criterion. The BCRs demonstrate the cost-effectiveness of the battery in microgrid operation. Battery options considered include both distributed option and a centralized option. It has been found that the best location of battery storage at Chalmers grid is at the point of connection to upstream grid of Gothenburg Energy distribution system for the centralized option. The study results show that the benefit gained from using battery storage increases with the size of battery, and the size with the highest BCR was found to be 2 MWh when considering the grid-connected mode of operation. The optimal size when the grid is in island mode is however dependent on island mode capability.