On uBeam's relative efficiency, from the article: When the university’s engineers heard about uBeam’s approach to wireless charging a month ago, the concept sp

On uBeam's relative efficiency, from the article: When the university’s engineers heard about uBeam’s approach to wireless charging a month ago, the concept sparked a discussion about a textbook exercise they teach their students, he added. “There’s a problem in an acoustics textbook: How long would you have to yell at a cup of coffee to make it boil?” said Bailey. “It’s something like 10 years.” Geesh!