When it comes to such things as energy transmission the laws of physics dictate what's possible and what is not. Just like the laws of physics dictate that there is an end to how much smaller you can make something (which caused the end of the free ride we call Moore's law) they dictate how much power you can transmit through a given medium with waves generated through some means in that medium.

Tesla tried to transmit energy using coils and antennae, both of which were fairly well understood at the time.

uBeam is trying to do something similar, but over much smaller distances (a few meters rather than all over the globe from a single transmitter) and using soundwaves.

So at face value uBeam's goal is much more achievable than Tesla's.

The most important component in transmitting energy using soundwaves is called a transducer, it takes electrical energy and transforms it into a soundwave with some measure of efficiency (higher = better, the remainder is heat which you need to conduct away from the transmitter). It can also do the reverse, convert soundwaves back into electrical energy.

Transducers exist in a number of varieties, the ones most suitable for energy transmission work using the piezoelectric principle (a magnet based system or electrostatic system would not have a high enough efficiency at those frequencies).

So, to transmit energy using soundwaves you need at a minimum two transducers, a generator to power the transmitter (which is a fairly simple device that outputs a repetitive wave form, or a much more complicated device if you want to 'steer' the soundwave by changing the phase between the signals with which multiple transducers are powered).

But for now let's just assume one transducer to send and one to receive with.

You then need to point the receiver at the sender and vice-versa or it will not work, also, any objects in between the sender and the receiver will attenuate the signal to the point where it probably also won't work.

The transmitter and receiver each have their own conversion efficiency, and the expanding wave-front from the transmitter will hit an area much larger than the receiving transducer by the time it arrives there leading to further loss. Then there is loss due to friction in the air.

All these losses are multiplied with each other and that is what makes this whole affair so fragile. The problem is that if it works at all it will need an input power that is large enough to cause serious concern about the risks associated with pumping that much energy at a frequency where it can do real harm into a space occupied by humans and pets.

Likely we're talking about at a minimum 100's of watts and possibly 1000's of watts in order to output a very low amount of power at the receiver. No 'modern components' or 'additional research' is going to change the basics.

Assuming that article linked elsewhere in this thread is true then 53% of the energy transmitted will be lost at 1 meter. Assuming for the moment then that half is lost for every meter that would mean that you're going to have a 3dB loss for every meter of path-length. That means that if you want to transmit over 3 meters (ceiling to a table) you'll have to input 8 times as much power on the input side as you will get on the output side. And that's not counting any other conversion losses, that's just the best case that I've seen so far from one transducer to the other without knowing the specifics of that setup because I can't read the paper.

But consider that the very best case and what I can see in the linked demo is not within orders of magnitude from that level of efficiency.

So uBeam is - as far as I'm concerned - still very very far away from being either a reality or even a feasible concept, the fact that it would be nice to have does not make it any more real, for the moment it seems as though practical obstacles will prevent it from ever becoming real.

So I remain skeptical and would very much wish that uBeam would give at least one demo that did not leave you with more questions than you started out with, they have had all the chances in the world by now to substantiate their (outrageous) claims, and they've already considerably walked back their initial claims and have by now more or less admitted that their previous demos were staged (as was suspected at the time).