Power over WiFi: 'Physics is Physics' or 'Dare to Dream'?

by Ben Smith on 23rd February 2010

Our post about the RCA Airnergy device generated a bit if a conversation… both for and against.

To reflect many of the sceptical comments around the web I added a video from EEVblog which summarised much of the physics-based disbelief, but our readers can do better than that…

In the meantime Terrence Eden had been handing the believers their back-sides in physics-shaped hats

- A WiFi access point can transmit a maximum of 0.1W.
- A WiFi access point radiates energy in a sphere – it does not direct the signal.
- A WiFi access point does not transmit all the time.

A typical USB charger supplies about 4.4 volts at 100 milli Amps. That’s about 0.44 Watts.

So, this magical devices would need to absorb ALL of the power produced by a WiFi access point with 100% efficiency with the WiFi transmitting ALL the time in order to get a quarter of the needed power.

And that’s the best case scenario. And it’s impossible.

…This is a nice idea – pick up lost power – but as Scotty says “You canna change the laws of physics!”

But Jonathan MacDonald says he’s also seen another firm working on this technology and believes we are witnessing a game-changer. He urges us not to fall into the trap of ‘The Fallacy of Certainty‘:

For the moment I remain a sceptic but am confused why a brand such as RCA – one which is used by a number of firms none of whom would be obvious sources of earth-shattering physics breakthroughs – would make this claim regardless if it’s true or not.

What do you think?

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