ABSTRACT
Energy is stored because of the variability of some renewable resources or to keep the building powered during a grid failure. Having batteries as part of the system makes it possible to run building functions when no electricity is being produced. Adding batteries reduces the overall efficiency of the system because of the additional energy needed to charge and to maintain full charge. Batteries are direct current (DC). Batteries need to be deep cycle: able to be discharged and recharged many times without losing capability. The two most common battery types used today are lithium-ion and lead-acid, which use different chemical reactions to produce electricity. Batteries hold a lot of charge and need to be cared for, stored, and secure. The size of the battery bank depends on the daily load, system voltage, days of autonomy, discharge limit, and amp-hour (Ah) capacity of the battery. Other energy storage options include pumped storage hydropower (PSH), molten salt energy storage (MSES), vanadium redox flow technology (VRF), and phase change materials (PCM).
