Performance evaluation of a multi‐functional solar thermal system tested under hot arid climate

A stainless steel–based multi‐functional integrated solar device capable of simultaneous drying, cooking, and water heating was designed, fabricated, and experimentally evaluated under hot arid climatic conditions of Rajasthan (26.24° N 73.01° E), India. The use of stainless steel effectively overcomes corrosion and leakage issues associated with conventional galvanized iron systems, thereby enhancing durability, structural integrity, and long‐term operational reliability. The system incorporates a trapezoidal water storage tank beneath the drying cabinet, which improves heat transfer and promotes natural convection, resulting in better temperature uniformity. Experiments indicated that the system achieved a maximum temperature of 120°C under no‐load conditions, while maintaining temperatures up to 75°C during drying and approximately 105°C during cooking operations. The highest recorded temperature in the water heating subsystem was 56°C, which was obtained through effective thermal storage. The drying cabinet reduced the weight of fenugreek leaves from 750 to 85 g which gave around 88.7% moisture removal in the drying experiments. The best model found for fenugreek leaves drying was the Midilli model with a good coefficient of determination value ( R 2 = 0.995). Economic feasibility analysis was also carried out which resulted in a benefit–cost ratio of 2.03 and payback period of 5.09 years. Including carbon credit monetization, these indicators improved considerably to 2.53, ₹ 29,482, 34.7%, and 3.55 years, respectively. The developed system shows good thermal efficiency and economic feasibility and has potential applications for decentralized sustainable energy systems.