Optimally arranged Savonius wind turbine clusters utilize aerodynamic coupling effects to significantly enhance the average power output compared with isolated units. Existing relevant research mainly focuses on inefficient semicircular turbines and typically neglects the crucial impact of the relative-phase angle (Δϕ) between adjacent turbines (0° by default). This study pioneers the exploration of high-efficiency modified Bach turbines through validated numerical simulations

with Δϕ set at 90° to maintain the positive effect linked to the phase angle. Quantitative spacing effects in dual-turbine systems were initially established. Subsequently

the Taguchi method was applied to optimize the average power coefficient (CP) of a three-turbine cluster

with turbine spacing (S1

S2)

configuration angles (θ1

θ2)

and rotation direction (RD) as experimental factors. Results reveal that angles exert the most significant impact on CP

followed by spacing and RD. The optimal configuration [S1 = 1.6D

S2 = 1.6D

θ1 = 110°

θ2 = 110°

RD = (+

−

+)] achieves a 64.13% improvement in CP compared with the isolated turbine

with the flow structure analysis of it revealing the coupling mechanisms accounting for performance enhancement. Furthermore

a scalable quasi-linear cluster was developed based on the optimal configuration

yielding a 58.97% enhancement in average CP at five-turbine scale. The findings confirm the potential of the modified Bach blade and Δϕ = 90° for optimizing Savonius wind turbine clusters

aiding the development of low-speed distributed wind power generation.