indica News Bureau-
An Indian-origin electrical engineer at the University of California, Los Angeles, has designed a device that uses the darkness of night to create light.
The idea struck Dr Aaswath Raman when traveling through Sierra Leone in West Africa six years ago. It was pitch dark and only when he heard muffled human voices did Dr Aaswath realize that he was passing through human habitation. There was, he recalled, not a single light around.
That made the engineer wonder if he could use all that darkness to light up something, the way solar panels use the sun’s heat and light to generate electricity.
Last week, in new research published in the scientific journal Joule and reported in The New York Times, Dr Aaswath demonstrated how to harness a dark sky to light up a bulb.
The prototype he has designed uses radiative cooling, the phenomenon that makes buildings and parks feel cooler than the surrounding air after sunset, to generate electricity.
As the device releases heat, it does so unevenly, the top cooling faster than the bottom. This difference in heat is converted to electricity. In his paper, Dr Aaswath described how his device, when connected to a voltage converter, was able to power a white LED.
Dr Aaswath and his colleagues Wei Li and Shanhui Fan wrote in their paper: “Thermodynamically, for any energy conversion process to produce useful work, for example, electricity, there must be a hot source and a cold sink. Most renewable approaches to electricity generation, including photovoltaics and solar thermal systems, rely on using the Sun as the hot source and the ambient surroundings of Earth as a cold sink. At night, however, no such ubiquitous and easily accessible hot source exists to drive a heat engine.”
However, they pointed out that at night there exists a “ubiquitous cold sink that has to date been largely ignored: the cold of outer space. Using the ambient air surrounding Earth’s surface instead as the heat source and space as the cold sink, then, would allow one to drive a new kind of night-time heat engine and generate electricity at night.”
Those interested in knowing how exactly the experiment was carried out can click here. (https://www.cell.com/joule/fulltext/S2542-4351(19)30412-X)
The innovation has immense possibilities even though the power generated through this method is a fraction of that generated through, let’s say, photovoltaic cells. Jeffrey C Grossman, a materials scientist at the Massachusetts Institute of Technology who studies passive cooling and solar technology, said the work was “quite exciting” and showed promise for the development of low-power applications at night, The New York Times report said.
“They have suggested reasonable paths for increasing the performance of their device,” Dr Grossman said. “But there is definitely a long way to go if they want to use it as an alternative to adding battery storage for solar cells.”