The word “limitless” is in the headline and in the text because it is undefined. Some will think that there is an infinite amount of power available.
But it isn’t.
This seems to yield small amounts of power, and looks like it can be useful.
The idea of limitless in this case is as long as the circuit is able to absorb thermal energy from it’s surroundings the current will flow indefinitely. Put a device such as this in a perfectly insulated box and thermodynamics dictates that as work is extracted via thermal motion of atoms in this case graphene that thermal energy is reduced thus cooling the device. As long as you are able to supply thermal energy from the ambient environment then the thermal vibrations will continue forever. Could be quite useful to power small sensors in remote places if they can store energy in a capacitor then you can use a graphene based ultracapacitor to drive a radio burst transmitter to send data to a remote receiver.
Tesla had a similar idea to use quantum vibrations to literally pull energy from the quantum vacuum. He didn’t use the terms quantum it was ethereal energy but same thing.
University PR department strikes again!