In 2015, Drayson Technologies announced Freevolt, a system that harvests energy from radio frequency (RF) signals bouncing around the air and turns it into usable, “perpetual power.” Capturing energy from the thin air is nothing new, but most proof-of-concept scenarios have employed dedicated transmitters that power devices at short ranges. Freevolt is the first commercially available technology that powers devices using ambient RF energy, no dedicated transmitter required. Freevolt uses a multi-band antenna which scavenges RF energy from any source within the 0.5-5GHz range, which is then fed through an “ultra-efficient” rectifier that turns this energy into DC electricity. A standard Freevolt unit produces only 100 microwatts of power which is still insufficient to charge your smartphone. But the internet of things sensor-based devices, such as a smart smoke alarm, can be powered by Freevolt indefinitely. Beacons that provide indoor mapping and targeted advertising are also perfect candidates. An entire smart city — where roads know when they’re busy and bins know when they’re full — could be devised using countless sensors that require no upkeep, and have no overheads beyond the price of the hardware itself.