Solar Thermal Integration for Traditional Dairy Processing in India: Design, Performance, and Sustainable Development Potential

Abstract This study investigates the feasibility of concentrated solar energy for producing traditional Indian dairy products, Khoa and Basundi, as a sustainable alternative to conventional energy sources. A customized solar parabolic trough collector (6.88 m2 aperture, 0.58 m focal length, 84° rim angle) was developed for thermal processing, using Sigma Therm-K heat transfer fluid to deliver energy to a stainless-steel jacketed vessel. Various absorber tube configurations were tested, with and without polycarbonate covers. The twin-double-pass copper tube with cover (C-3) showed the best performance, achieving a peak useful heat rate of 1697 W and a daily average thermal efficiency of 31.52%, outperforming other designs even under lower DNI. The system enabled complete solar-based preparation of dairy products while meeting Food Safety and Standards Authority of India (FSSAI) norms. Seasonal variations, particularly cosine losses and end-shadowing, reduced wintertime efficiency. An economic analysis estimated a 4.6–5.7-year payback period, confirming feasibility for small-scale, standalone dairy operations. The results emphasize the potential of solar thermal integration for decentralized food processing, enhancing energy efficiency and sustainability in the agri-food sector.