Adaptive covers for combined radiative cooling and solar heating. A review of existing technology and materials

• Published in: Solar energy materials and solar cells Vol. 230; p. 111275
• Main Authors: Vilà, Roger, Martorell, Ingrid, Medrano, Marc, Castell, Albert
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 15-09-2021; Elsevier BV
• Subjects: Adaptive cover; Convection suppression; Coolers; Cooling; Energy consumption; Heating; Hot water heating; Optical properties; Radiative cooling; Radiators; Renewable energy; Smart materials; Solar collectors; Solar heating; Solar thermal collection; Technology; Temperature; Adaptive cover; Convection suppression; Radiative cooling; Renewable energy; Solar thermal collection
• ISSN: 0927-0248; 1879-3398
• DOI: 10.1016/j.solmat.2021.111275

Radiative cooling is a promising technology for space cooling. This technology can be combined with solar heating applications, enabling the production of both energy demands –heat during daytime and cold during nighttime– in a single device; thus, reducing the non-renewable primary energy consumption for space conditioning and domestic hot water. Radiative cooling and solar heating appear in different wavelength ranges, 8–14 μm and 0.25–2.5 μm respectively, thus the device must be able to switch between ranges in each mode. An adaptive cover placed on top of the radiator/absorber can provide this switch by combining materials with suitable optical properties for each mode. Another effect derived from the usage of covers is the reduction of convective heat losses, enhancing the performance of the device. This paper aims to review the existing materials used in solar collectors, and radiative coolers as well as available smart materials used in other fields for its potential use as adaptive covers for combined radiative cooling and solar heating applications.
•First review on adaptive covers for combined radiative cooling and solar heating.•Overview on radiative cooling and mixed solar collector/radiative cooling system.•Empirical correlations for convection coefficients in radiators and collectors.•Discussion on main materials used in solar collectors and radiative coolers.