Abstract
Since electricity generated by wind power and other renewable sources fluctuates significantly, their extensive use requires energy storage technologies. This study analyzes life cycle CO2 emission (LCCO2) of power generation systems combining wind turbines with energy storage equipment, focusing on four types of hydrogen storage, i.e. compression hydrogen (cH), liquid hydrogen (LH), metal hydride (MH), and organic hydride (MCH) as well as three types of battery, i.e. lead-acid (PbA), redox flow (RF), and sodium-sulfur (NaS). In order to appropriately compare the two different types of system, the functional unit is defined to meet customers' demands of electricity and heat, because this study assumes that hydrogen is finally converted into electricity and heat using a fuel cell at consumption sites. The analysis revealed that, in general, LCCO2 of battery systems is smaller than that of hydrogen storage systems, not depending on characteristics of customers (e. g. heat-to-power ratios, load curves) and the patterns of wind power, when wind turbines are away from consumption sites. However, when wind turbines are located at consumption sites, LCCO2 of cH and MH systems is almost equivalent to that of battery systems for a customer who has a relatively large heat demand such as a factory, hotel and hospital.
