4E performance evaluation of renewable microgrids: Comparing hydrogen and battery storage for nearly net zero energy buildings

Abstract

Renewable microgrids and decentralized power generation have recently emerged as sustainable solutions for powering standalone nearly-net-zero buildings. This study proposed two photovoltaic-based microgrids: one with hydrogen energy storage and the other with battery energy storage, to supply the real-time energy needs for electrical appliances, heating, cooling, and hot water at a research office. Both systems are designed to achieve a levelized cost of energy of 0.78 EUR/kWh. Simulated using TRNSYS 18 software with a dynamic power load following model, the systems have been evaluated based on Energetic, Exergetic, Economic, and Environmental (4E) criteria over the first year of operation. The hydrogen-based system comprises a 13.1-kWp photovoltaic array, a 7-kW alkaline electrolyzer, and a 3.5-kW fuel cell. In contrast, the battery-based system includes a 150-kWh lead-acid battery. The hydrogen-based system fully meets the electrical demand with a loss of load probability of 0% and provides hot water through waste heat recovery from the fuel cell. The battery-based system, however, results in a loss of load probability of 4.34%. Both systems exhibit similar overall energy efficiencies but slightly different exergy efficiencies. The first system achieves 12.37% and 14.33%, respectively, while the second system achieves 12.28% and 20.8%. Despite the battery-based system having a higher energy dump, it boasts a greater round-trip efficiency of 90.23% compared to 46.86% for the hydrogen-based one. Both configurations avoid annual greenhouse gas emissions of about 8.5 tCO₂ eq. Therefore, they can be considered sustainable alternatives for cleaner energy production, significantly contributing to carbon footprint minimization.