The four young Finnish engineers who invented this sand battery go back a long way. Tommi Eronen, Markku Ylönen, Liisa Naskali and Ville Kivioja bonded as children over a shared passion for athletics. The sprinter, cyclist, triple jumper and discus thrower belonged to the same club in Tampere, southern Finland, cheering each other on at track and field events during their teenage years.
