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.