Abandoned Helsinki oil caverns now heat 25,000 homes for a year

In a groundbreaking move toward carbon neutrality, Helsinki has transformed two abandoned underground oil caverns into Finland’s largest heat storage facility. According to Helen, the city’s energy company, the caverns in Mustikkamaa were filled with 260,000 cubic metres of hot water, creating a giant “heat battery” to balance consumption peaks throughout the year. The project, which began construction in 2018 and was completed in 2021, marks a unique case even on a global scale and represents an important step on Helsinki’s path to becoming carbon neutral. The stored heat corresponds to the heating of 25,000 one-bedroom apartments all year round and is expected to decrease Helen’s carbon dioxide emissions by 21,000 tonnes per year.A unique solution for a cold climateThe heat caverns, located 80 metres underground in Mustikkamaa, are a unique case even on a global scale.