Heating equipment inside the Marstal solar heating plant on Danish island of Aeroe. It’s among the largest in the world with more than 33000 m2 covered in solar panels, producing heat for 1560 customers, who are also owners of the cooperative station. When the heating requirement cannot be covered by the sun, a wood pellet boiler will supplement the requirement. Two Danish islands, Samsoe and Aeroe, became the first of Denmark's official renewable energy islands.