The research aims to study the effect of leading edge protuberances on the blade performance at the stall region of the small-scale horizontal axis wind turbine (HAWT) with variable rotational speed. Experiments were carried out for the blades with smooth leading edge (baseline) as well as some comparative models with leading edge protuberances characterized by different sinusoidal amplitudes and wavelengths. The experiments were performed for the 3D static models to obtain the lift/drag coefficients. Additionally, rotor-blade models of the HAWT system were also tested separately to consider the rotation effect. From the experiments, the results indicated that the protuberant blades with smaller amplitudes possess better performance at the stall region as compared with the baseline model. The research aims to study the effect of leading edge protuberances on the blade performance at the stall region of the small-scale horizontal axis wind turbine (HAWT) with variable rotational speed. Experiments were carried out for the blades with smooth leading edge (baseline) as well as some comparative models with leading edge protuberances characterized by different sinusoidal amplitudes and wavelengths. From the experiments, the results indicated that the protuberant blades with smaller amplitudes possess better performance at the stall region as compared with the baseline model. Display omitted •Experiments were performed to study the protuberance effect on a variable-speed HAWT .•This paper reports the effects of sinusoidal protuberances on the Cp of the HAWT blade.•Protuberances will increase the lift/drag ratios for static tests of 3D models under negative angles of attack.•The blade with larger amplitude and smaller wavelength for the sinusoidal protuberances will perform worse.•The Cp at the stall region (with low tip ratios) is effectively improved by the sinusoidal protuberances.