Case C-571/21, RWE Power: Judgment of the Court (Fifth Chamber) of 9 March 2023 (request for a preliminary ruling from the Finanzgericht Düsseldorf — Germany) — RWE Power Aktiengesellschaft v Hauptzollamt Duisburg (Reference for a preliminary ruling — Taxation of energy products and electricity — Directive 2003/96/EC — Article 14(1)(a) — Second and third sentences of Article 21(3) — Electricity used to produce electricity and to maintain the ability to produce electricity — Exemption — Scope — Opencast mining operations — Electricity used in order to operate fuel bunkers and means of transport)