Design and fabrication of a solar powered paddy rice winnowing and destoning machine.

Abstract

Rice is a staple food for more than half of the global population, playing a critical role in food security worldwide (Mohidem et al., 2022). In 2020, global rice production was around 500 million metric tons, with Asia producing over 90% of this output (Mohidem et al., 2022). In Africa, rice is becoming increasingly important, especially in West Africa, where countries like Nigeria and Senegal lead in production. However, contamination from stones, dust, and foreign materials remains a persistent challenge, negatively affecting rice quality and market value (De Vos et al., 2023). Uganda, a leading rice producer in East Africa, has experienced rapid growth in rice cultivation, expanding from 20,000 hectares in the early 2000s to over 95,000 hectares by 2020 (UBOS, 2022). The country produces a substantial volume of rice but still faces significant postharvest losses due to inadequate processing equipment, particularly for winnowing and destoning.

Traditional or semi-mechanized methods used in rice-growing regions like Butaleja, Pallisa, and Gulu are tedious and labor-intensive, resulting in poor rice quality and economic losses for smallholder farmers (Oonyu et al., 2011). Addressing these challenges, this study presents the design and fabrication of a solar-powered paddy rice winnowing and de-stoning machine. This machine aims to improve rice processing efficiency by integrating sustainable solar energy, making it particularly suitable for rural areas where electricity access is limited and fossil fuel costs are prohibitive (Ageze et al., 2024). The machine addresses the limitations of earlier designs, such as the inefficiency of 36% caused by high camshaft vibration and reliance on a single sieve size (Joseph et al., 2022). It features an innovative linkage system to control vibrational energy and two interchangeable sieves: an upper, detachable sieve for larger impurities and a lower sieve for finer contaminants. This modular design accommodates different grain sizes, enhancing impurity separation and overall processing efficiency.