A spectral analyser, showing the power density of frequency bands present in the room. The big spike at 2.4GHz is Wi-Fi; the lower bands will be GSM, 3G, and 4G.

Freevolt: Perpetual, free RF energy harvesting to power the Internet of Things

www.kent.ac.uk stms documents research reports T1_12 batchelor.pdf

uk stms documents research reports batchelor.

The world is awash in free power just waiting to be exploited (sort of...)

Europe proposes shifting TV frequencies to make way for mobile services by 2020

Wireless / RF Energy Harvesting Example

RF-based Wireless Charging and Energy Harvesting.