You know those crystal sets that people played with many years ago? They enabled you to listen to radio using a high impedance earphone, without a battery, because the radio waves induce a small voltage in the circuit (forgive me if I don’t understand it fully)
Well, I’ve often wondered why thousands or even millions of these circuits couldn’t be connected in series to give us some free meaningful power. If someone could explain..
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There is no such thing as a free lunch. The energy conversions of those setups experiences a lot of loss, a quick google shows they only get around 30-40% efficiency. This means that for every watt of power you want the receiving device to get the transmitter has to pump out around 2.5 watts.
And you still have to generate the radio waves that are being used to power the devices. So instead of getting a free and universal power supply you are getting an extremely expensive and inefficient power system. Not only does the transmitter have to pump out enough power to supply the devices, it has to pump that power out in all directions regardless of if a device is there to receive the energy.
If you try to use background radio noise your devices are limited to that level of power generation.
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