A step above solar power with the energy harvesting mobile phone screens

Love your mobile phone, but hate its capacity to run flat at the most inconvenient moments? This defining ethos for mobile phones is a global issue soon to be curtailed by the University of Cambridge. IEEE Fellow Arokia Nathan now promises a future where phones may never need to be plugged in, ever again.

Nathan’s group of resourceful scientists have cooked up a prototype device which takes ambient light and converts it into juicy energy. An array of solar cells, made up of hydrogenated amorphous silicon will lie within the mobile phone’s display. The mobile phone becomes an effective, lightweight energy harvester.

Typically, 36% of generated light escapes from the front of the display. The “wasted light” will be harnessed with the assistance of thin-film PV cells embedded on the edge of the screen, according to Nathan.

For the energy harvester to work, the issue of fluctuation must be addressed. Voltage fluctuations can permanently fry the phone’s battery. To correct this, the research team created a thin-film transistor circuit to “smooth out voltage spikes and extract energy efficiently”.

The battery will not be charged directly, as according to the Cambridge team, this would have meant the creation of highly complex circuitry. Again, a workaround was created in the form of supercapacitors, electric systems which can generate as much as 165 microwatts per square centimetre in the ideal light conditions.

An example laid out by Nathan proposes that a 3.7-inch smartphone screen which could produce an output of five milliwatts. Unfortunately, this is a mere fraction of what a typical smartphone requires.

The energy harvesting screen can also be cheaply produced according to Nathan. The thin-film device is made with lightweight plastics which barely affect the overall weight as well as the cost of integrating it into a mobile phone. The team continues its research, but the promise of free, ever-available power is a palpable reality.

Steven Norris: grumpy curmudgeon


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