Energy efficiency matters.
We know that consumers love products without a connector, but it is impossible to beat the efficiency of a connector and copper wire. (No, superconductive wires are not more efficient than copper wires. The cost of cooling is prohibitive.)
So what can we do to create efficient wireless battery chargers?
We found that standby power consumption is the key. Standby power dominates total energy consumption for battery chargers that remain connected to mains power. By lowering standby power the total energy consumption is significantly reduced.
How low can you go? At first I thought we would have to trade low standby power against response time. You would expect that a responsive transmitter, searching constantly for new power-demanding receivers, will consume more power than a transmitter that goes to sleep and looks once a minute.
It turns out there is no need to trade response time. I have seen a Qi transmitter with a standby power of only 0.0001 Watt (100 µW) that detects new receivers instantaneously.
In the efficiency analysis that is published on the front page you can see what the effect is on total energy consumption.
