Modeling and design optimization of carbon-free hybrid energy systems with thermal and hydrogen storage

With increasing demand for carbon-free power to mitigate climate change, hybrid energy systems (HES) is expected to play an instrumental role in the coming decades. The study is focused on replacing all coal and natural gas electricity generation in the state of Texas with solar, wind, and nuclear power. As an integral part of the designed nuclear-renewable hybrid energy system (N-RHES), both thermal and hydrogen storages are used to provide daily short-term and seasonal energy storage. Each subsystem is dynamically modeled in Dymola/Modelica with hourly wind speed and solar irradiance data entering the wind turbine and solar PV modules. Using Year 2020 data, the N-RHES is collectively controlled to meet hourly energy demand of the state. Aiming to minimize the system's levelized cost of energy (LCOE) while meeting the demand at all times of the year, an optimization algorithm is developed to find an optimum design point of the system. The optimized LCOE of the system was found to be $73.04/MWH, which results from 61 Natrium nuclear power plants, 5317 3.2-MW wind turbines, and 307.9 km² of solar PV panels. While this optimized LCOE is greater than the current LCOE, it provides carbon-free electricity for the entire state of Texas. According to the design, most of the demand is met by nuclear power with the rest being a near even split between wind and solar power. Although the stored hydrogen in salt caverns contributed only to a small portion of the total electricity production, it provides a large amount of green hydrogen to future clean energy markets.