Case C-4/16: Judgment of the Court (Second Chamber) of 2 March 2017 (request for a preliminary ruling from the Sąd Apelacyjny w Warszawie Wydział Cywilny — Poland) — J. D. v Prezes Urzędu Regulacji Energetyki (Reference for a preliminary ruling — Environment — Directive 2009/28/EC — The second subparagraph of Article 2(a) — Energy from renewable sources — Hydropower — Meaning — Energy produced in a small-scale hydropower plant located at the point of discharge of industrial waste water from another plant)