RF Energy Harvesting for Controllable Wireless Power Systems
The slide show here was presented by Charlie Greene of Powercast during the 4th Annual Energy Harvesting Workshop at Virginia Tech in January 2009.
Notice on slide 9 how multiple transmitters of lower aggregate power create a more even field of available RF energy than a single, higher power transmitter. With this kind of design, a wireless power infrastructure can be created within buildings similar to lighting or Wi-Fi. Also notice on slide 15 the graphed results of calculations that show how wireless sensors spend a majority of battery energy on sleep mode. If power was sent wirelessly on a scheduled or periodic basis, sleep mode could be replaced by an inactive state where the sensor is essentially consuming no power.