Solar Cooking with Reinforced Coating Experiment

Abstract

The continued dependence on solid fuels for household energy remains a critical global challenge, with approximately 2.1–3 billion people relying on biomass, coal, and kerosene for cooking, primarily in developing regions (Pokharel, 2004). This reliance contributes to millions of premature deaths annually due to household air pollution. In South Asia, this dependence persists despite high solar availability (4–6 kWh/m²/day), highlighting a clear gap between renewable energy potential and practical adoption. Among available alternatives, box-type solar cookers offer a low-cost and sustainable solution; however, their widespread use is limited by low thermal efficiency and significant heat losses. Previous studies identify absorber surface properties as a key factor influencing performance, where increased absorptivity and reduced emissivity directly improve heat retention and system efficiency (Sarangi et al., 2024). This study experimentally evaluates the performance of a box-type solar cooker integrated with three reinforced selective coatings — anodized aluminum, black enamel, and black powder coating — under real climatic conditions in Kathmandu, Nepal. The system was fabricated using locally available materials, incorporating a double-glazed cover, insulated enclosure, and optimized reflectors. Temperature measurements were recorded via K-type thermocouples across three field trials (7 August 2025, 7 September 2025, and 8 September 2025) under solar insolation ranging from 400 to 800 W/m², capturing both clear-sky and partly cloudy conditions. Standardized thermal efficiency (η) was calculated for each coating by averaging the rate of temperature rise across all three trials and normalizing to a baseline irradiance of 700 W/m² (Vilarinho et al., 2016). While black enamel recorded the single highest instantaneous peak temperature (81.87°C) in one trial, its higher emissivity produced greater radiative losses over the full test duration; when averaged across all trials, anodized aluminum delivered the highest standardized efficiency — (29.68% clear-sky, 19.91% cloudy, 28.15% post-noon)— due to its lower emissivity and faster thermal response. These findings confirm that targeted material optimization can substantially improve solar cooker efficiency, positioning such systems as practical, cost-effective, and sustainable solutions for reducing fuel dependency, lowering emissions, and advancing clean energy adoption in developing