Polar Night Energy, a Finnish thermal energy storage startup, has successfully secured €7.6 million (~$8.1 million) in a seed funding round. Jonathan Oppenheimer, a South African businessman, led this round, which was co-led by Finnish investment companies Stephen Industries, Holdix, and Turret and joined by a Swedish family-owned investment company, PC Rettig & Co. Impact. Existing investors also participated in the funding round.