A new kind of solar panels shows that we can generate electricity even at night

(ORDO NEWS) — Conventional solar technology absorbs rays of incoming sunlight to generate voltage. Ironically, some materials are able to work in reverse, producing energy when they radiate heat back into the cold night sky.

A team of Australian engineers has demonstrated the theory in action, using technology commonly used in night vision goggles to generate power.

So far, the prototype generates only a small amount of power and is likely unlikely to be a competitive source of renewable energy on its own – but when combined with existing photovoltaic technology, it could use the small amount of power generated by solar panels cooling down after a long, hot day at work.

“Photovoltaics, the direct conversion of sunlight into electricity, is an artificial process that humans have developed to convert solar energy into electricity,” says Phoebe Pierce, a physicist at the University of New South Wales.

“In this sense, the thermoradiative process is similar; we are redirecting energy flowing in the infrared from a warm Earth into a cold Universe.”

By heating the atoms of any material, you cause their electrons to generate low-energy pulses of electromagnetic radiation in the form of infrared light.

No matter how weak these oscillations of electrons are, they are still capable of starting a slow current of electricity. All it takes is a one-way electronic traffic light called a diode.

Made from the right combination of elements, a diode can shuffle electrons down the street as it slowly loses its heat to a colder environment.

In this case, the diode is made of mercury-cadmium telluride (MCT). The ability of MCTs to absorb mid- and far-range infrared light and convert it into current is already being used in devices that detect infrared light and has been well studied.

But it is still not entirely clear how this special trick can be effectively used as a real source of energy.

Heated to about 20 degrees Celsius (nearly 70 degrees Fahrenheit), one of the tested MCT photoelectric detectors generated a power density of 2.26 milliwatts per square meter.

Of course, this is not enough to boil a pitcher of water for morning coffee. For this small task, you will probably need enough MCT panels to cover several city blocks.

But that’s not the point, as it’s still very early days in the field and there is potential for technology development in the future.

“At the moment, the demonstration we’re doing with the thermoradiation diode is relatively low power. One of the challenges has been actually detecting it,” said Ned Ekins-Dawks, lead researcher on the study.

“But the theory says that eventually this technology could produce about 1/10th of the power of a solar cell.”

With this efficiency, it might be worth the effort to weave MCT diodes into more typical PV grids so that they continue to recharge batteries long after sunset.

To be clear, the idea of ​​using the cooling of the planet as a source of low-energy radiation has been of interest to engineers for some time. Different methods give different results, and they all have their own costs and benefits.

However, by testing the limits of each and tweaking their ability to absorb more infrared, we can create a set of technologies that can extract every drop of energy from virtually any type of waste heat.

“In the future, this technology could harvest that energy and eliminate the need for batteries in some devices or help charge them,” Ekins-Dawks says.

“This is not a case where conventional solar is necessarily a viable option.”


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