Can you clarify the 70% efficiency claim in the article? I assume this is 70% efficiency of DC conversion of received power, and not any sort of end-to-end metric?
70% efficiency is the current state of the art limit for solid state based Tx. we loose close to 0% in the atmosphere and our Rx is well beyond 90% efficient.
What end-to-end efficiency are you getting and at what distance?
For example, we are currently looking at powering an island across a distance of 30km with an end-to-end efficiency of around 60%.
I bet Musk will be your best friend if you brief him with such project ;)