Way of harvesting energy in the air from wireless and broadcast networks to power low energy devices unveiled. The ‘Freevolt’ technology collects radio frequency energy from networks such as 4G, WiFi and digital TV to power devices such as wearables and sensors that form part of the “internet of things” without needing to plug them in, according to the British entrepreneur who recently demonstrated the system. “It doesn’t require any extra infrastructure. It doesn’t require us to transmit any extra…