The Lightning Lords: Book 2 of the Van Diemen Chronicles

A deadly flu epidemic is now sweeping through the southern lands of Tasmania threatening to wipe out what remains of their small community. In desperation the Hobart Mayor Lily Dayton, who still lives in a city without electricity, sends her nephew Tom on a mission to seek out a rumoured Tower in the island's midlands. The Tower is a massive construction built to send electricity wirelessly through the air and ground but is said to be defended by silver clad beings who can throw lightning from their hands.