Research Projects

Global urbanization and industrialization have dramatically increased energy demands, with cooling systems accounting for a significant portion of the demand. In the Indian subcontinent, extreme temperatures are common; air-conditioning is both a necessity and a liability on energy infrastructure. The International Energy Agency (IEA) predicts that cooling energy demand will triple by 2050, mainly driven by urban growth and rising incomes. This trajectory poses a dual challenge: meeting cooling demands sustainably while reducing environmental impacts. Traditional cooling technologies, such as air conditioners and chillers, rely mostly on electricity and refrigerants. These systems are not only energy-intensive but also emit greenhouse gases, directly contributing towards global warming. For instance, hydrofluorocarbons (HFCs), widely used in refrigeration, have global warming potentials thousands of times more than CO₂. Passive Radiative Coolers (PRC) offer a sustainable alternative by using thermal radiation to dissipate heat into the coldness of outer space (~3 K) through the atmospheric transmittance window (i.e. 8–13 µm wavelengths). This mechanism requires no external energy inputs, making it a promising candidate for energy-efficient cooling. Unlike active cooling systems, PRC can operate round the clock, provided the material design allows for daytime solar reflectivity and nighttime thermal emissivity. Design and development of a daytime PRC remain a challenge due to stringent optical requirements: minimizing solar absorption (between 0.3–2.5 µm wavelengths) and atmospheric absorption (between 2.5–8 µm wavelengths) while maintaining high emissivity in the atmospheric transmittance window (i.e. 8–13 µm wavelengths). Existing solutions often face scalability, robustness, or environmental resilience limitations. This project aims to fill this gap, providing a scalable, durable metamaterial-based PRC design suitable for diverse applications. The project will be carried out in three main steps. The first step involves exploring the metamaterials-based design of PRC that may significantly increase the cooling performance resulting in increased temperature reduction below the ambient temperature. Further, we aim to obtain optimized parameters for the metamaterials-based design of PRC through rigorous theoretical modelling and numerical simulations using full-wave multi-physics software. In the next stage, prototype devices will be fabricated in a clean room environment using typical photolithography or e-beam lithography. Finally, we will assess the devices for their desired optical responses.