One of green energy‘s biggest challenges is how to provide a year-round, steady power supply from renewable energy during changing seasons and variable weather conditions: the answer is sand, in Vatajankoski power plant, 270 km north-west of Helsinki, home to the world’s first commercial-scale sand battery. Fully enclosed in a 7m-high steel container, the battery consists of 100 tonnes of low-grade builders’ sand, two district heating pipes and a fan: the sand becomes a battery after it is heated up to 600C using electricity generated by wind turbines and solar panels in Finland, brought by Vatajankoski, the owners of the power plant. The renewable energy powers a resistance heater which heats up the air inside the sand: inside the battery, this hot air is circulated by a fan around the sand through heat exchange pipes. Read more on