Global Radiative Sky Cooling Potential Adjusted for Population Density and Cooling Demand

Ablimit Aili,Ronggui Yang,Xiaobo Yin

doi:10.3390/atmos12111379

Ablimit Aili, Ronggui Yang + Show 1 more

Open Access

https://doi.org/10.3390/atmos12111379

Copy DOI

Abstract

Thanks to recent advances in nanophotonics and scalable manufacturing of metamaterials, radiative sky cooling has emerged as a “self-reliant” cooling technology with various potential applications. However, not every region across the globe is well suited for the adoption of radiative cooling technologies, depending on the local climate, population density, cooling demand, air conditioning saturation, economic prosperity, etc. Because the atmospheric downward longwave radiation, especially the portion from the atmospheric window (8–13 µm), is substantially affected by weather conditions, the performance of a well-designed radiative cooler can be vastly different across regions and seasons. Here, we first map the global radiative sky cooling potential in the form of net cooling power density. We then further evaluate it based on the global population density and cooling demand. In terms of the adjusted potential, we show that geographically and demographically “transitional” regions, located between wet and dry climates as well as sparsely and densely populated regions, are better suited for the adoption of radiative cooling technologies because of their temperate climate and moderate population density. Even in densely populated and humid regions, the cumulative impact and other accompanying benefits must not be ignored.

Highlights

Radiative sky cooling refers to the process of passively cooling a sky-facing object by maximizing its net emission of longwave thermal radiation and minimizing its absorption of downward shortwave radiation
The seasonal anomaly of cooling potential, ers that agrees with specific experimental measurements [3,48,49,50], there are still misunpopulation density, and globalpractices cooling in demand are important factors determine the derstandings and unrealistic the modeling of radiative skythat cooling
Since we have only cloud cover fraction data on the global scale, we argue in a similar manner next. (i) If the sky is completely covered by clouds ( f = 1), the cloud base is near the Earth’s surface and acts as a black body (Tcloud ≈ Tamb and ε cloud = 1). (ii) If the sky is partially covered by clouds ( f < 1), the cloud base tends to be higher and colder, and the cloud cover fraction is exponentially proportional to the cloud base temperature, T

Summary

Introduction

Radiative sky cooling refers to the process of passively cooling a sky-facing object by maximizing its net emission of longwave thermal radiation and minimizing its absorption of downward shortwave radiation. The Earth itself is the largest radiative cooling object, manifesting its subambient cooling potential through occasional occurrences of dew or frost in some clear-sky mornings [4]. This self-cooling capability of sky-facing surfaces gives the inspiration that a highly solar-reflective and yet highly infrared-emissive object can relentlessly maintain its coolness even during the day. Radiative sky cooling can be an attractive complement or even an alternative to traditional cooling technologies such as power-intensive air conditioning [15,17,18,19,20] and Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations

Methods

Results

Conclusion