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Innovative Device Harnesses Heat at Night


New device generates electricity from darkness.

Winter is fast approaching, days are getting shorter, nights are getting colder. It is inevitable that even the most eco-conscious among us start thinking a bit more about staying warm and cosy.

A team of scientists from Stanford University, took on a quest to explore unconventional ways to generate electricity, which can green up the long nights. They tapped into something that everyone shines away from- the darkness.

The process the team based their concept on is called radiative cooling. Their invention was designed to harness the energy, which the Earth sends back to the atmosphere in the form of reflected thermal radiation. Essentially, this is the exact opposite process of what solar cells are based on.

The team designed a system, which consists of black aluminium disks (each 20 centimetre wide), which are connected to regular thermoelectricity generators. The disks act as emitters of radiation. When the heat is emitted from the surface of the Earth to the air it reaches the thermoelectricity generators and hits the disks. The system was able to produce the impressive 25 milliwatts per square meter of the disk at night. This is roughly sufficient to power an LED. What is even better, the device can act in reverse manner, and harness the energy from the sun during the day.

The scientists point out that the device can be optimized further, easily producing 0.5 watts per square meter of disk in drier environments, or with better insulation.

Although compared to solar cells, the amount is quite minimal, the potential of such system is great. Imagine what a difference something like this could make in a remote area in Africa, where energy storage is a luxury, while lights at night are more than necessary. Aaswath Raman, an assistant professor of materials science and engineering at the University of California, and lead author of the study, points out that the system is very cheap and can definitely serve as a great backup when solar panels are not able to produce energy.

Image (c) Raman et al (Joule (2019))

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  1. Coupled underneath solar panels, you’d get electricity day and night…
    Well, OK, only a few hundredths of what solar panels produce, so just enough to feed a webcam and IR LEDs. But on a large scale, it would also cool down the area.


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