Polar Night Energy and Lahti Energia are partnering on the Sand Battery project in Finland. Image: Polar Night Energy / Lahti Energia. Technology provider Polar Night Energy and utility Lahti Energia have partnered for a large-scale project using Polar’s ‘Sand Battery’ technology for the latter’s district heating network in Vääksy, Finland. The project will have a heating power of 2MW and a thermal energy storage (TES) capacity of 250MW, making it a 125-hour system and the largest sand-based TE...