The optimum configuration and operating strategy for a wind-diesel system is highly dependent upon the peculiarities of the wind regime and load pattern at the host location. Thus it is highly desirable before deciding upon a specific system to obtain an insight into performance by using a mathematical model.

In this chapter various methods are outlined whereby wind-diesel systems can be simulated and the aim and state of development of each approach is given. Originally it had been the intention of the authors to identify the most accurate and cost effective models to emerge from the International Energy Agency programme on Decentralised Applications of Wind Energy. This has not proven to be possible due to both the specific nature of most of the current models being developed and to the difficulty and cost of obtaining a comprehensive data set with which to validate them. Full details have therefore only been included on the simpler approaches. To guide future researchers an overview is given of the IEA model validation exercise, and recommended common reporting formats are suggested for future intercomparison of the models.

The purpose of developing models of wind-diesel systems is primarily to fulfil the need for cost effective planning and design tools. Depending upon the level of decision being taken on the planning of the system, different types and complexity of model are required. There are two main approaches to modelling: Time Series and Statistical.