Thermal performance and energy efficiency of a hybrid solar thermosyphon evaporative cooling system for livestock housing

Abstract

Heat stress in livestock housing significantly reduces animal productivity and increases the energy demand of environmental control systems, particularly in tropical climates. This study experimentally investigates a hybrid solar thermosyphon heating-cooling system integrated with evaporative cooling and floor-based water circulation for improving thermal performance, energy efficiency, and environmental sustainability in livestock houses. The proposed system utilizes a thermosyphon heat pipe solar collector to generate hot water during the daytime and chilled water during the nighttime, enabling continuous thermal management. Experimental results demonstrate that the thermosyphon system reduces the temperature of 1000 L of water from 30 °C to approximately 26 °C within 12 h during nighttime, while producing hot water at 48–52 °C during daytime. The use of chilled water enhances the performance of the evaporative cooling system, increasing the heat transfer rate of the wetted media by 27.8% and improving the overall heat transfer coefficient from 509.4 to 664.0 W·K−1. In addition, the integration of floor water circulation improves cooling efficiency by approximately 8.6% and reduces indoor relative humidity by about 5.8%. The Temperature–Humidity Index (THI) decreased from 81.3 to 75.0, indicating a reduction in the index-based assessment of potential heat stress. Furthermore, the system showed a potential electrical energy saving of approximately 3.3%, corresponding to an estimated reduction in CO₂ emissions of 383.2 kg CO₂/year. However, the uncertainty associated with the electrical-energy-saving estimate was not independently quantified; therefore, this result should be interpreted cautiously. Further testing with component-level electricity monitoring and independently repeated comparative trials is needed to establish the reliability and generalizability of the estimated energy-saving potential. These findings suggest that integrating renewable energy with conventional cooling systems may improve environmental control and contribute to more sustainable livestock production under tropical conditions.