to convert microwaves into 7.3V of electrical energy. By comparison, Universal Serial Bus (USB) chargers for small electronic devices provide about 5V of power.
Oooooo, volts. How about power instead.
Consider a powerful AM station like WLW (50 kilowatt transmit power). At 1 km away, assuming no atmospheric absorption and and omnidirectional pattern (not true but good for a first estimate), you would have an energy flux of about 4 milliwatts per square meter. Now consider that most of the transmitters they are talking about are in the milliwatt to watt range instead of 50 kW.
Compare that to solar which has an energy flux of about 1 kilowatt / square meter at ground level on a sunny day.
Discovered in the ruins of the Twentieth Century Motor Company in Starnesville, Wisconsin.