Graphene based and LED heat energy converters

Heat into electricity and heat into light energy converters

It’s just curious, but two innovative energy converters from heat to another form of energy have been claimed at the start of this month.

The first one I discuss and I link here, and claimed by Researchers at Hong Kong Polytechnic University, is a kind of battery, where a conductive graphene strip is connected between two electrodes and soaked in a solution of copper-chloride ions.

The copper ions (Cu2+) moves inside the solution because of the thermal energy from environment and continually collide with graphene. In the graphene the electron quasi-particle at the Dirac point, has a zero effective mass and a minimal energy suffices to free it from the graphene structure, so that an electrical current is generated. They have produced a voltage of more than 2 V, enough to drive a red light-emitting diode.

This work paves the way to practical applications such as cooling systems and energy harvesting.

Click here for a figure

Preprint: http://arxiv.org/abs/1203.0161

More information here: http://physicsworld.com/cws/article/news/48889

The other discovery, made by researchers from the Massachusetts Institute of Technology, enables to convert thermal energy into infrared light by using  a LED. As it is well known, semiconductors are poors light emitters, and usually the low energy emitted equals the bandgap. In this case the device is able to convert lattice vibrations into infrared photons, in such a way to harvest thermal energy from the surroundings. To get this, they have lowered the bias voltage to values very low corresponding to a power input of 30 pW and measured 70 pW of power being emitted by the LED, obtaining an efficiency of more than 200%. Of course, the surplus of energy is coming from the thermal energy in the surroundings of the device.

Unfortunately the very low energy involved do not promise practical applications in the near future.

The link to the full PRL article is here: http://prl.aps.org/abstract/PRL/v108/i9/e097403

For more information: http://physicsworld.com/cws/article/news/48882

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About Francesco Buonocore

Francesco Buonocore is an Italian solid state theoretical physicist, staff scientist of the Italian government agency ENEA. Francesco likes Physics, thinking about Physics and how Physics and life are related.
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