Investigating impacts of condensation on thermal performance in greenhouse glazing and operational energy use for sustainable agriculture

Abstract

Condensation frequently manifests in environmentally controlled agricultural structures (such as greenhouses) due to the utilisation of specific covering materials and the often meticulous management of high relative humidity to facilitate optimal plant growth. The formation of condensation can significantly influence the thermal and optical characteristics of the covering materials, which also affects the covering insulation and the growth of plants. This study was conducted to investigate the impacts of surface condensation on the thermal performance of various greenhouse covering types. These options feature low-emissivity (Low-E) coatings, infrared reflective (IR) additives, UV protective films, and anti-condensation additives. The physical properties, specifically emissivity and wettability, were examined to understand their roles in modifying the thermal transfer dynamics of greenhouse coverings. A scale physical model was made to test the thermal performance of the coverings with and without condensation. The results indicated the effect of condensation on the overall heat transfer coefficient (U-factor). Especially when the surface exhibited characteristics of low emissivity, it resulted in a notable near-tripling of the U-factor. These widely accepted and advocated strategies of Low-E and IR reflective products may inadvertently lead to enhanced operational energy consumption when considering the influence of condensation. Notably, this research has also devised a regression function that establishes a correlation between the contact angle and the condensation heat transfer coefficient. This tool facilitates swift analysis and estimation of the effects of condensation on the U-factor. In the end, the potential and future work on condensation effects is also discussed.