Optimal energy mix of a microhydro-wind-grid system powering a dairy farm in Western Cape, South Africa.

Abstract This paper presents an optimal control strategy of a grid-tied microhydro-wind power system for a rural dairy farm in South Africa. The problem is formulated as a multi-objective optimisation programme in discrete time domain to minimise grid imported energy cost under Time of Use Tariff (TOU) while at the same time maximising revenue generated from the sale of surplus renewable energy to the grid at a specified renewable energy feed-in tariff. The application of the proposed model to a practical case study shows the potential of the model to save the farmer the grid energy cost up to 75.07% in summer and 70.69% in the winter with a discounted repayment period of 3 years and 7 months.