This podcast episode examines Finland's innovative use of sand batteries as a solution for seasonal energy storage, particularly for heating purposes. These systems function as thermal energy storage, converting surplus renewable electricity into heat stored in large volumes of sand. The text highlights the advantages of sand, such as its low cost, abundance, high heat retention capacity, and environmental friendliness, while also addressing limitations like the inefficiency of electricity reconversion and challenges in scaling for individual homes. Case studies of commercial projects in Kankaanpää and Pornainen demonstrate the technology's development and potential, particularly in district heating networks, aligning with Finland's goals for carbon neutrality and energy security. Ultimately, the sources suggest sand batteries represent a promising, albeit still developing, approach within a diverse range of energy storage solutions.