Development and performance evaluation of an indirect fresnel lens solar cooker with thermal oil storage tank

• A Fresnel solar cooker with thermal oil storage is designed and tested off-grid. • The solar cooker can achieve 16.92% efficiency with a concentration ratio of 127.43. • The absorber temparature can reach 160 °C and the hotplate stabilized at 103.3 °C. • Developed solar cooker can boil 500 ml of water in 24.75 min and fry an egg in 33 min. • The developed solar cooker costs ∼$485 and cuts energy costs in sunny, off-grid areas. This study introduces the design, fabrication, and performance assessment of an innovative indirect solar cooker that uses a Fresnel lens in combination with a thermal oil storage tank—specifically designed for off-grid and rural settings. While concentrating solar cookers offer notable benefits, their limited ability to store heat and function under fluctuating sunlight remains a major drawback. To overcome these issues, we developed a new system that incorporates a 90 × 160 cm flat Fresnel lens, a cylindrical copper cavity absorber, and a thermal oil circulation loop connected to a stainless-steel hotplate. A dual-axis solar tracking mechanism was employed to enhance optical efficiency. Heat captured at the lens's focal point is transferred through thermal oil to a 7-liter insulated storage tank, and from there to the cooking surface. The system underwent field testing over four sunny days in Tehran during July 2023, with environmental and performance data recorded at 10-minute intervals. Results showed a peak absorber temperature of 160 °C and a steady hotplate temperature of 103.3 °C. The average thermal efficiency was calculated at 16.92%, and the optical concentration ratio reached 127.43. Cooking trials further highlighted the system's practicality: boiling 500 ml of water took 24.75 minutes, frying an egg required 33 minutes, and cooking 100 g of potatoes took 74.5 minutes. A cost analysis revealed a total fabrication expense of USD 485, with an estimated payback period of under five years in typical household scenarios where LPG costs exceed 0.3 USD/kg. Altogether, this solar cooker presents a sustainable, fuel-free solution for clean cooking, with strong potential for local manufacturing and deployment in remote areas. Future efforts will explore scaling the system and integrating phase change materials to enhance thermal storage.