Performance characteristics, power losses and mechanical power estimation for a breastshot water wheel

•Water wheels are a sustainable and efficient way for the production of energy.•The characteristic curves of a breastshot wheel are calculated experimentally.•A theoretical model is developed and compared to simplified past models.•The biggest power losses are those occurring during the impact and filling process.•A better design of the inlet and blades will improve the efficiency of the wheel.

Breastshot water wheels were in widespread use in the Nineteenth and Early Twentieth century for the production of energy; although they represent an economic, efficient and sustainable technology, only a small amount of research has been paid to water wheels nowadays, in particular to the breastshot ones.In this work a theoretical approach is adopted to estimate the different kinds of power losses occurring inside a breastshot water wheel, in order to predict its mechanical output power. The theoretical results are then validated with experimental results on a physical steel model. The characteristics experimental curves of the wheel are also illustrated, reporting the wheel efficiency and output power versus the flowrate, stream and wheel velocity.The average estimated error between the experimental and the estimated theoretical output power is 9%, which is much lower than that calculated using some past formulations found in literature. The theoretical results show that the big power losses are the dissipation of the stream kinetic energy against the blades and the hydraulic losses in the headrace, after the passage through the sluice gate; therefore, a better design of the inlet and blades geometry may improve the efficiency of the wheel.