Determination of battery energy storage technology and size for standalone microgrids

The high investment cost associated with upgrading utility grid to supply remote area's demand for electricity makes the implementation of standalone microgrids inevitable. These microgrids normally consist of a mix of energy sources such as diesel generators, photovoltaic arrays, wind turbines, and fuel cells. In order to improve the microgrid reliability, reduce its operation cost, and address operational challenges, battery energy storages (BESs) are commonly integrated within remote microgrids. There are a variety of BES technologies with different characteristics which makes it crucial to select the BES technology that is best suited for the standalone microgrid. Since the BES capital cost depends on its size, it is also very important to determine the optimal size for the installed BES. In this paper, a mathematical model that combines the optimization of choosing the BES technology (based on the technical characteristics) and size is developed. The objective is to minimize the standalone microgrid annual expansion planning cost while ensuring that critical loads could be supplied without interruption. Value of loss load is included in the objective function to quantify the economic loss of failing to supply the local load. A mixed integer programming method is used to formulate the problem. The proposed model is tested on a standalone microgrid. The results indicate that the BES technology selection and sizing depend greatly on the microgrid configuration and the renewable penetration level.