Finland isn’t exactly known for hot weather. But as the climate changes and summer heat waves become more common in northern Europe, don’t expect to see more air conditioners in Helsinki: The city is pioneering a huge cooling system that uses cold water from nearby lakes and the sea instead of electricity.
Hundreds of feet underneath an ordinary-looking park in downtown Helsinki, a local energy company built a huge reservoir filled with nearly 9 million gallons of lake water. When the system is fully operational next summer, the water will be pumped to local buildings in the area to keep them cool. At night, the water will flow back underground, where waste energy will be used to cool it down again.