ADVANCED THERMODYNAMIC DESIGN AND PERFORMANCE EVALUATION OF A SOLAR-ASSISTED ABSORPTION MACHINE FOR DUAL-MODE FERMENTATION COOLING AND MACERATION HEATING IN THE WINEMAKING INDUSTRY

Abstract

Temperature control is a critical parameter in winemaking, directly influencing fermentation kinetics, flavor development, and color stability. Conventional refrigeration and heating units employed for fermentation cooling and maceration heating rely heavily on electricity or fossil fuels, leading to high operational costs and environmental impacts. This study presents an advanced thermodynamic design and performance evaluation of a solar-assisted absorption machine engineered to provide dual-mode operation delivering both cooling and heating for winery processes. The proposed system integrates solar thermal collectors, a LiBr–H₂O absorption refrigeration cycle, and a stratified hot-water storage system to supply chilled and hot fluids to the fermentation and maceration units, respectively. A detailed thermodynamic model was developed based on the first and second laws of thermodynamics, incorporating energy, exergy, and mass balances for each component. The influence of solar collector temperature, generator heat input, and absorber/condenser cooling water flow rate on the coefficient of performance (COP) and exergy efficiency was examined. The system was simulated under realistic climatic and process conditions typical of Mediterranean winery regions, and validated through a pilot-scale setup designed to deliver a 10 kWₜₕ refrigeration capacity and 8 kWₜₕ heating output. Results indicate that the solar-assisted absorption system achieved a COP₍cooling₎ of 0.74 and COP₍heating₎ of 1.65, with an overall exergy efficiency of 43 % at peak solar irradiation. The solar fraction reached up to 68 %, significantly reducing auxiliary energy consumption. The system maintained fermentation temperatures between 15–28 °C with less than ±0.5 °C deviation, while maceration heating achieved rapid thermal ramps to 60–70 °C within 20 minutes, satisfying enological requirements. Comparative energy analysis revealed 32 % savings in primary energy and a reduction of approximately 0.42 kg CO₂ kWh⁻¹ relative to conventional vapor-compression systems. The study demonstrates that solar-driven absorption technology can effectively substitute mechanical chillers and electric heaters for winery thermal management. Beyond energy and environmental benefits, the dual-mode configuration simplifies plant layout, enhances operational flexibility, and enables partial heat recovery between cooling and heating cycles. The proposed design framework provides valuable guidelines for mechanical engineers in optimizing absorption systems for industrial process applications, contributing to the transition toward sustainable and low-carbon manufacturing in the food and beverage sector.