Diode Harvests Ambient Infrared Energy
S. Himmelstein | February 05, 2018
Overlapping metal arms shaped like a bowtie form a ‘rectenna’ that captures renewable infrared energy. Source: Atif Shamim, KAUSTInfrared radiation is ubiquitous, with natural emissions estimated to be millions of gigawatts per second. Such radiation is viewed as an energy resource by researchers from King Abdullah University of Science and Technology, who developed a device that can harness infrared’s power potential as well as waste heat from industrial processes.
Infrared heat can be harvested 24 hours a day by treating it as high-frequency electromagnetic waves. Using appropriately designed antennas collected waves are sent to a rectifier, typically a semiconductor diode, that converts alternating signals to direct current charge for batteries or power devices. However, infrared emissions have very small wavelengths and require micro- or nanoscale antennas that are not easy to fabricate or test. Infrared waves also oscillate thousands of times faster than a typical semiconductor can move electrons through its junction.
The research team turned to quantum tunneling for a solution. Tunneling devices, such as metal-insulator-metal (MIM) diodes, rectify infrared waves into current by moving electrons through a small barrier which is only a nanometer thin. The MIM diodes can therefore handle high-frequency signals - 28.3 THz or 10.6 μm - on the order of femtoseconds.
A bowtie-shaped nano-antenna that sandwiches the thin insulator film between two slightly overlapped metallic arms was designed to produce the intense fields needed for tunneling. The structure is assembled with metals featuring different work functions, enabling the MIM diode to capture the infrared waves with zero applied voltage, a passive feature that switches the device on only when needed. Experiments with infrared exposure revealed the bowtie successfully harvested energy solely from the radiation and not from thermal effects, as evidenced by a polarization-dependent output voltage.
The research is published in the journal Materials Today Energy.
Hmmm, the 2nd law of thermodynamics seems to be attracting more and more detractors and opponents these days.
How long till ThermoCongress debates an amendment to replace or repeal the 2nd law of thermo?
Maybe the second law is just more of a guideline of sorts.....
I read the article in, " materials today energy ". I have a question, maybe someone can answer it.
How large or small would a rectenna need to be to produce (1) volt of DC current ?
Personally I think this is a wonderful idea and I hope they can bring it to fruition .
In reply to #3
"... How large or small would a rectenna need to be to produce (1) volt of DC current ?..."
....at least 4 seconds large or small.
j/k The question is moot. Current is not measured in volts.
In reply to #4
Sorry about the moottation. Let me rephrase the question.
How large or small would a rectenna need to be to produce 1 volt DC ?
In reply to #5
The size of the individual antennae will be based on the peak frequency attempting to be harvested. So it depends on the ambient temperature from which energy is to be harvested.
The paper linked was working on harvesting in the 28 THz neighborhood. They calculate 85 nV from their antenna with an area of 3.4 ×10-5 mm2
It is important to note the harvesting was done while a laser was applied to the rectenna and that significant efforts were needed to differentiate energy harvested vs. noise. Efficiency of the rectenna was calculated to be 1.75 x 10-14 .
In reply to #6
Thank you for your reply. I can tell you Want to help others understand information. :)