Think about all the ambient radio waves in our environment: 2.4 and 5Ghz WiFi, similar wireless home phone frequencies, terrestrial radio and television, cell phone frequencies, etc. There’s a lot of waves in the air and these waves carry energy. What if we could harvest them.
This is exactly the tech that Nokia is developing according to the MIT Technology Review. The tech is similar to already existing RFID tags, which harvest electromagnetic waves and convert it to an electrical signal. All that needs to be done is ramp up the conversion efficiency.
Currently Nokia claims their prototypes can harvest about 3 to 5 milliwatts of power from ambient RF frequencies, which isn’t very much. However, they are working on new prototypes that will harvest up to 50 milliwatts, which is enough to slowly charge a phone which is in a power saving mode.
Unfortunately, the biggest hurdle for this project is enabling the antennas to harvest enough frequencies to gain that much power. They need a wide band antenna that can pick up hundreds of different radio frequencies so they could generate enough power. Such an antenna would drain power and also lose capturing efficiency due the amount of frequencies it would be looking for.
But regardless, the research sounds promising and if Nokia can do it, they would revolutionize the way think about smartphone batteries. This combined with their recent research into solar powered smartphone screens could spell the end of charging cables forever (army least for Lumia phones). This tech is estimated to be available to the mass market in about 3 to 5 years.