Ground-facing radiative cooling for high power LED lights

Abstract

Objects on Earth facing the sky have the ability to emit thermal energy into the universe through the transparent atmosphere. This process can enable electricity-free cooling due to the extremely low temperature of outer space. However, factors such as humidity, clouds, and air pollution within the atmosphere can affect this process, particularly for electricity-free sub-ambient cooling applications. For high-temperature objects, the dependency of radiative cooling performance on the environment is significantly reduced. In this study, we explore the potential of utilizing ground-facing radiative cooling for improved high-power light-emitting-diode (LED) lighting applications. By using a transparent material, like polyethylene, as the front cover of the LED light package, one can efficiently release thermal radiation from the semiconductor chips that can reach temperatures of 60–130 °C. As a result, we demonstrate a reduction in the operational temperature of the LED chip by 3.9 °C in controlled indoor settings and by 3.7 °C in selected outdoor environments. Our analysis reveals that employing ground-facing radiative cooling can enhance the luminous efficacy of LED lights by approximately 3.0%. Assuming all current global electricity consumption is used for LED lights, this enhancement translates to an estimated annual energy savings of 128 terawatt-hours and a reduction in carbon dioxide emissions by 55 million metric tons. Remarkably, according to our aging experiment over 4000 h, this method can extend the lifespan of LED lights by 21.7% due to the lowered junction temperature of the semiconductor chip, resulting in reduced material, labor, and maintenance costs for future global LED lighting products.