Thermal analysis and optimization of stand-alone microgrids with metal hydride based hydrogen storage

Abstract

Stand-alone microgrids, also known as remote area power supply systems, are crucial towards providing electricity access to off-the-grid locations/buildings and for communities trying to become 100% dependent on renewables. Design and development of efficient energy storage system remains a key challenge for the stand-alone microgrid technology. Metal hydride based hydrogen-energy storage system, offering long term energy storage at near ambient conditions and additional benefits of thermal and green hydrogen output, have attracted researchers and industrialists worldwide. In this work, LaNi5 (Lanthanum Penta-nickel) based hydrogen-energy storage system for stand-alone microgrid application is studied. An optimization study is performed to find the optimal sizes of hybrid (solar + wind) and wind microgrid components for the requirements of typical Indian village/UK community of 50 households located at various geographical locations, having diverse solar and wind resources availability. The study ensures that the microgrid satisfies the required electric load but is not over-designed, which is achieved by limiting the two performance parameters i.e., unmet load fraction and excess electricity fraction, below 10%. The optimization study is done based on an hourly analysis for a year using the simulation software HOMER. A thermal analysis is carried out to quantify the additional benefit of thermal output from the energy storage system. Comparisons between the performance and thermal output of optimized hybrid and wind microgrids are carried out for the selected locations. Also, green hydrogen produced for energy storage and available for use at the end of the year is quantified. Upon comparing hybrid (solar PV + wind turbine) and wind energy based microgrids, it is observed that hydrogen storage requirement decreases by up to 97% while using hybrid energy source depending on the location. Besides serving electrical load, the microgrid delivers thermal outputs of about 1kWh and 5kWh for Indian and UK locations respectively.