Dispatch optimization of the electricity and heat of the smart-energy-transform-unit

With the integration of renewable energy production into grids, hydrogen storage is an effective solution for coping with the fluctuating nature of the resources and reliably providing energy demands. Metal hydride storage is seen as a key technology due to its low operating pressure and temperatures near ambient, while it has a significant volumetric capacity (for room temperature hydrides: 50-110 kg/m³) compared to pressurized (40 kg/m³ under 700 bar and room temperature) or even liquified hydrogen (70 kg/m³ at – 253 ºC and 1 bar). One potential application with metal hydride storage lies in the flexibilization of residential energy demand. Excess photovoltaic generation from a house can power an electrolyser to produce hydrogen, which is then stored in the metal hydride storage. When power and heat are needed in the building, the hydrogen is released into a fuel cell. This case study investigates the dispatch optimization of a metal hydride storage system within a residential household energy system. The interaction of the electrolyser, metal hydride storage, and fuel cell, all components of a container solution called Smart Energy Transform Unit, was studied during summer and winter. Results show that in an exemplary period in winter, from 21 December 2021 to 28 December 2021, the total electricity demand is 98% covered by supply from the grid due to the low photovoltaic generation, which also yields a low hydrogen production; the total heat demand is 90% covered by the heat pump and the thermal storage as a buffer. During an exemplary period in summer, from 20 June 2021 to 27 June 2021, the system is self-sufficient, as hydrogen was stored during the day due to the high yield of photovoltaic generation, and hydrogen is used in a fuel cell at night to provide energy demands. In addition, heat pump operation during summer is small due to the heat provided by the electrolyser, the fuel cell, and the thermal buffer storage. The PV system, together with the Smart Energy Transform Unit, covers 99% of the total electric demand during this period in summer, while for the total heat demand, a coverage of 85% is observed, and the heat pump covers 15%.