In this work, AlxGa1−xAs nanostructures on a planar Si substrate are employed to achieve highly efficient light trapping with improved light absorption. In this context, cylindrical and conical nanostructures are shown to render themselves as better light absorption surfaces. The effects of the AlxGa1−xAs nanostructures geometrical parameters and the Al concentration (x%) on the optical characteristics of the proposed solar absorber (SA) are studied. The optical performance of the suggested SA is numerically simulated using three-dimensional finite difference time domain method. The reported absorber has a superior performance in terms of absorption and short circuit current density, compared to its counterparts in the literature. The SA with cylindrical and truncated cone nanostructures can offer a high short circuit current density of 31.28 and 33.20 mA/cm2, respectively.

Radiative cooling exploits the imbalance between the thermal emission from the radiative cooling surface and the downward atmospheric emission. Since the atmospheric emission power is polar angle-dependent, a mirror structure can be used to increase this imbalance and to amplify the net cooling power. The degree of amplification is determined by various parameters, such as the sky emissivity, the geometry of the mirror structure, and the degree of thermal insulation. A parametric study of aperture mirror-enhanced radiative cooling is presented using a model atmosphere, characterized by an average sky window emissivity and the ambient temperature. A counterintuitive finding is obtained: the aperture mirror structure is more effective in the tropics than in the desert, both in terms of the cooling power and the temperature reduction. The power enhancement obtainable from a relatively simple mirror structure can be significant. For example, in the tropics, the cooling power can be enhanced by more than 40%. The aperture mirror structure holds the potential to be a practical augmentation to improve the stagnant temperature and the response time of radiative cooling devices.

Fossil fuel consumption for heating and cooling represents a considerable portion, approximately half, of the world’s total energy use, thereby presenting a substantial challenge in diminishing dependence on these energy sources. Our study presents the design and fabrication of a zero-energy switchable radiative cooler (ZESRC) to address the global climate crisis by reducing energy consumption within buildings. ZESRC utilizes a simple morphology-driven method that exploits materials’ differing thermal expansion coefficients, enabling a seamless switch between cooling and heating modes at any preset temperature point, enabling superior adaptive thermal management. Field experiments demonstrate that, relative to ambient temperature, ZESRC usage results in a maximum temperature decrease of 7.1°C during summer and a maximum increase of 7.5°C in winter. Furthermore, we developed an energy-efficiency map for different climate zones, showing the ZESRC’s superiority over devices with only solar heating or radiative cooling, cutting building energy use by 14.3%. The results underscore the ZESRC’s capability for net-zero energy consumption, significantly advancing global energy conservation and the 2050 net-zero carbon goal.