The Case of the Vanishing Power Levels

Jul. 2019
Power vs. Distance. Click to enlarge

Power vs. Distance. Click to enlarge

The promise of long-range wireless power is: “power anywhere”.  No batteries. No wire. No matter where you are within the range of the power source.

But this promise is severely tainted if the amount of power that a device can receive is very dependent on the distance from the power transmitter. Such changing power levels mean that a device might receive enough energy when it is very close to the power source but not be able to receive sufficient energy when it is farther from it.

With Wi-Charge, this is not an issue. Because light can travel in a thin, focused beam, the small Wi-Charge receiver can provide the same amount of energy to the charged device, regardless of distance.

Sadly, this is not the case with alternative approaches to wireless power. Most other approaches follow the “inverse square” law, meaning that with every doubling of the distance, power levels drop by 75%. For instance, let’s assume that the device in question can receive a sufficient amount of energy when it is 1 ft (0.3 meters) from the power transmitter. Let’s call this an energy level of 100%. Consider what happens when the distance grows:

  • At 3 ft (just under 1 meter), you’d get just 11% of the energy level
  • At 10 ft (~3 meters), you’d be able to get just 1% of the original energy level
  • At 5 meters, you’d be able to receive just 0.3% of the original energy level.

That’s not good. Why settle for vanishing power levels when you can have constant power levels?