I am pretty nutty when it comes to energy efficiency. It upsets me to know that if the morons who built my house had used the latest information available at the time, my house would require almost no heating. One thing that really gets me excited is the prospect of reusing waste energy. I like the idea of taking energy that would otherwise be destined to diffuse out into the environment and turning it into something useful.
As such, it was inevitable that a paper on recovering microwave energy would catch my eye. And, yes, I shall inflict it on you, too. Unfortunately, harvesting Wi-Fi radiation doesn't seem like it will win us very much. But before we get to that, let's take a look at the very cool ideas behind the harvester.
The basic idea behind harvesting Wi-Fi radiation is a very old one: just construct a circuit that absorbs all that microwave energy. Let's take a very artificial situation: imagine a microwave traveling along a bit of coaxial cable. A coaxial cable consists of a central conducting wire enclosed in a cylinder of non-conducting dielectric material, all wrapped in a conductor. The power from the microwaves is not transmitted "in" the central wire. It is actually in the electric and magnetic fields in the dielectric. These propagate as waves down the cable with a speed that is partially given by the properties of the dielectric material.
Ars TechnicaChris Lee https://arstechnica.com