Design and fabrication of a solar-powered tiller for smallholder crop growing in Uganda

Abstract

Smallholder farmers in Uganda primarily rely on hoes or costly diesel-powered tillers for cultivation, which results in low production, high labor intensity, and adverse environmental impacts. This study presents the design, fabrication, and field evaluation of a walking, electromechanical solar tiller tailored for small- and medium-scale crop growing. A detailed energy-mechanical analysis determined soil draft forces (≈4100 N) and the required blade torque (≈820 Nm at a 0.2 m radius), yielding a mechanical power demand of 8.6 kW. Accounting for drivetrain and motor efficiencies (≈80 %), an electrical power rating of 10.7 kW was selected. The powertrain integrates a 4-kW brushless DC motor, a 90 Ah lead-acid battery, and a 290 W photovoltaic array sized for six peak sun hours, enabling approximately 1.5 hours of continuous tillage per full charge. The chassis—a mild-steel frame with ergonomic handles—was modelled in SolidWorks and fabricated at MUARIK. Prototype tests on loam soil demonstrated effective tillage, producing a fine seedbed suitable for planting. However, the 240 kg machine imposed noticeable shoulder strain and chain-drive contamination from soil ingress. Bearing life calculations indicated above 19,000 hours under design loads. Recommendations for future iterations include substituting lightweight alloys to reduce total mass, sealing chain-drive housing to prevent debris penetration, adjustable ground clearance to protect drivetrain components, and vibration-dampening handle supports to enhance operator comfort.