Hydrogel-based thermal regulation strategies for passive cooling: A review

Hydrogels are characterized by their high heat absorption and dissipation capabilities, which offer significant potential for passive cooling applications. This review paper provides a comprehensive overview of advanced hydrogel-based cooling methods that utilize three distinct thermal regulation strategies: latent heat, sensible heat, and radiant heat. These heat transfer mechanisms serve as the basis for the development of four functional hydrogel: evaporative cooling hydrogel, radiative cooling hydrogel, thermoelectric hydrogel and thermal interface hydrogel. This review presents the basic principles related to these hydrogels and the general considerations for hydrogel-based cooling methods are provided. Hydrogel-based cooling techniques provide diverse capabilities in temperature reduction, cooling time, and cooling area to meet various cooling requirements. To deliver a unified evaluation of these hydrogels, this review investigates the cooling power and cooling capacity across different cooling methods, along with their test conditions. Analyzing and comparing these factors provides valuable insights into the effectiveness and applicability of hydrogel-based cooling methods in various scenarios. Then, typical applications of hydrogel-based cooling methods in buildings and electronic devices are discussed. By thoroughly exploring advancements in these passive cooling methods, this review contributes to the development of energy-efficient and sustainable cooling solutions for buildings.