There was a period of time when there was much hype about using 2.4Ghz WiFi to power sensors and recharge batteries. I was wondering if this would be a practical solution for the sensors in my home automation system.
To celebrate the temprary victory of being able to light an LED at a range of 1 ft, I gave a short talk about it at Hackware 2.7 back in 2017.
After the realization that the power transmission efficiency I was getting was super low (<0.1%) at a range of 10-15ft, and some people (including myself) were really not comfortable being irradiated with 5Ghz radio waves, I decided to call it a day and shelve this.
Hardware: HFSS for antenna design, CAD
Future work: Experiment with power delivery using an array of infrared lasers.
Credits: Assistance and advice from Ivan Lu and Wei Jia