; (D) district heating; (E) heat storage; (F) carbon capture, use, utilization, and storage; (G) microgrid or island applications; (H) integrated systems modeling, analysis, and optimization, inclusive of different configurations of hybrid energy systems; and (I) integrated design, planning, and operation of systems with existing infrastructure, including interconnection requirements with the electric grid, as appropriate. (4) Authorization of appropriations There are authorized to be appropriated to the Secretary to carry out the program under this subsection— (A) $52,500,000 for fiscal year 2021; (B) $55,125,000 for fiscal year 2022; (C) $57,881,250 for fiscal year 2023; (D) $60,775,313 for fiscal year 2024