A ‘thermal cloak’ the Janus shield: An asset for electric cars.

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A “thermal cloak” the Janus shield – one of the primary challenges in electric car technology is thermal management. Lithium-ion batteries, the beating heart of electric vehicles, are notably sensitive to temperature fluctuations. Whether it’s the intense heat of summer or the bitter cold of winter, these shifts can lead to a decline in battery performance and, over time, damage to the lithium-ion cells. However, a research team from Shanghai Jiao Tong University has crafted an ingenious and eco-friendly solution to this issue: a passive “thermal cloak” named Janus.

Janus: A Thermal Shield Inspired by Nature

Named after the two-faced Roman god, Janus is a battery cover that keeps electric cars cool in the summer and warm in the winter. This technological marvel operates on a captivating concept: it mimics how the Earth naturally cools itself against solar radiation. Kehang Cui, the lead author of the study, states, “The cloak essentially works in the same way the earth cools itself, through radiative cooling. The Earth is enveloped by the atmosphere, and the atmosphere is transparent to a certain range of electromagnetic energy.”

In practice, this means that the outer layer of the Janus cover absorbs energy and emits it in a long-wave infrared spectrum. These waves escape, thus allowing the electric car to stay cool. Indeed, the cloak’s material can reflect a significant portion of solar radiation.

An Economical and Efficient Assembly

But that’s not all. Janus’s design is simple and cost-effective. It consists of a layer of silica fibers coated with boron nitride, a material similar to graphite known for its high albedo, meaning its ability to reflect light effectively. These fibers are then woven to create a soft fabric before being adhered to an inner layer made of an aluminum alloy.

During tests, the team found that the cover could maintain a car’s interior temperature at 22.8°C (73°F) — almost eight degrees below the external temperature. In comparison, a vehicle without the device reached an internal temperature of 50.5°C (122.9°F), a significant difference of nearly 28°C (50.4°F).

In winter, the cloak is just as efficient. To prevent heat loss, the researchers employed a process called “photon recycling,” which bounces trapped energy between the car and the cloak. Quebec indeed experiences severe winters with temperatures plummeting to as low as -30°C (-22°F), and hot summers where the mercury can soar up to 35°C (95°F). These extreme conditions can affect the performance and durability of electric car batteries.


A Promising Advance for the Electric Automotive Industry

With Janus, the researchers from Shanghai Jiao Tong University have indicated a promising pathway to enhance the durability of electric car batteries. This straightforward and effective invention, if widely embraced, could significantly contribute to the energy efficiency of electric vehicles and ultimately reduce our overall carbon footprint.

In conclusion, this shield will substantially extend the lifespan of electric car batteries. Though this technology isn’t yet standard on all cars, if you have battery troubles, consider consulting a “Plug-in Garage” for repairs rather than replacing the entire battery unit.