Nanoplastics make more efficient streetlights if you turn them upside down

Scientists in Saudi Arabia have developed a new coating for streetlights which they believe will reduce energy lost as heat, making the lamps more efficient.

The research is published in the Springer journal Light: Science & Applications.

Streetlights are a particularly big burden on the city councils and municipalities. Streetlighting accounts for about 1–3% of total electricity demand worldwide, according to the global policy forum Clean Energy Ministerial.

Domestic and industrial lighting accounts for about 20% of total electricity usage globally, and 6% of greenhouse gas emissions, according to study lead Qiaoqiang Gan from the King Abdullah University of Science and Technology (KAUST).

“Thermal management is a critical challenge for semiconductor light-emitting diodes (LEDs), as inadequate heat dissipation reduces luminous efficiency and shortens the devices’ lifespan,” the authors write.

“There is an urgent need for more effective cooling strategies to enhance the energy efficiency of LEDs. LED streetlights, which operate primarily at night and experience high chip temperatures, could benefit greatly from improved thermal management.”

Co-author Hussam Qasem, from the King Abdulaziz City for Science and Technology, says the new design “significantly improves LED cooling while maintaining high illumination efficiency, making it a promising solution for sustainable lighting”.

The team developed a nanomaterial called nanoPE (nanoporous polyethylene) which enhances the release of thermal radiation from the LED’s surface and reduces the LED temperature. About 75% of the energy that goes into an LED is lost as heat.

NanoPE works if the lamps are turned upside down.

LEDs coated with the nanomaterial allow thermal radiation to pass through while visible light is reflected – hence the inversion of the lamp.

The study showed that 80% of the heat, or infrared light, passed through the coating into the sky. Meanwhile, more than 95% of the light reflected back to the ground.

NanoPE is based on polyethylene – the most widely produced plastic. The nanoplastic has holes as small as 30nm to allow infrared light to pass through while reflecting visible light.

The coating led to temperature reduction on LEDs of 7.8°C in the lab and 4.4°C outside.

“These reductions were accompanied by an efficiency improvement of approximately 5% and 4%, respectively,” the authors write. “This enhanced efficiency translates into substantial annual energy savings, estimated at 1.9 terawatt-hours when considering the use of LED streetlights in the United States. Furthermore, this electricity saving corresponds to a reduction of approximately 1.3 million metric tons of CO₂ emissions, equivalent to 0.03% of the total annual CO₂ emissions by the United States in 2018.”