DESIGN AND FABRICATION OF A MINI SOLAR OPERATED LAWN MOWER

ABSTRACT The rise in environmental concern and the high cost and unreliability of fossil fuels in Nigeria motivate alternatives for small-scale lawn maintenance. This project presents the design, fabrication and performance evaluation of a mini solar-powered lawn mower suited to Bayelsa State conditions. The prototype integrates a 100 W monocrystalline photovoltaic panel (99 × 58 cm), a 12 V/40 Ah deep-cycle lead-acid battery, a PWM solar charge controller and a 12 V, 600 rpm DC motor coupled to a 400 × 30 × 4 mm steel cutting blade. Design calculations used an average Bayelsa peak sun hour of 5 hrs. Fabrication emphasized local materials, safety (dead-man switch, blade guard) and maintainability. Laboratory and field tests measured PV output, battery charge/discharge behavior, motor current draw, cutting performance and system energy flows. Results show the PV array’s theoretical daily energy of ~415 Wh and an actual delivered-to-battery energy of ~370 Wh (system energy loss ≈45 Wh), giving an overall measured system efficiency of 370/415 = 89.2%. Measured motor current draw ranged from 7.8–9.2 A depending on grass height; single-pass run times varied from ~42 minutes (short grass, 2–3 cm) down to ~29 minutes (taller grass >10 cm). With solar recharging considered, cumulative operating capacity reached up to ~2–3 hours per day under clear sky conditions. Cutting quality was satisfactory for grasses up to ≈10 cm; heavier vegetation required multiple passes or a higher-torque motor. The prototype meets the project objectives: it demonstrates feasible component sizing and design for a solar mower, delivers a working fabricated prototype, and provides quantified performance comparisons versus conventional petrol units (no fuel cost, low noise, zero tailpipe emissions). Recommended next steps include battery chemistry upgrade (Li-ion), blade aerodynamics optimization, and optional MPPT charge control for partial-shade conditions. The work furnishes a practical, low-cost model for renewable lawn care in Nigerian and similar tropical contexts.