A Markovian Approach to Size a Hybrid Wind-Diesel Stand Alone System

A Markovian approach already developed in a previous paper by some of the authors to evaluate the energy production and power availability of a wind turbine is utilized to size a hybrid wind-diesel stand alone system. The wind turbine power time variability is taken into account by means of a discrete reduced number of contiguous power classes, each corresponding to an opportune range of values, starting from wind field measurement data; the duration of each class is statistically treated so to preserve information about the transition rates into all the other classes. A simple probabilistic model is developed to represent the load of a large shrimp farm to be supplied. The presence of an energy reserve constituted by lead acid batteries is taken into account by means of proper modifications of the power profile versus the time of the wind turbine. The hybrid system availability is evaluated by means of an availability model which explicitly refers only to diesel generator units, that assure the required availability level. The results obtained for the proposed models are compared with those obtainable by utilizing the time sequence of wind speeds observed and a large number of load demand time sequences.