ABSTRACT
This chapter is stimulated by the considerable confusion, still existing even in the wind power literature, on the ‘capacity credit’ or capacity value of wind power systems. By this is meant ultimately the extent to which the inclusion of wind power within an electricity grid can lead to savings in conventional power plant; or, more simply, author may ask whether a wind power system, because of its inherent unreliability, needs to have a complete backup of conventional plant. The chapter contributes some relatively simple arguments and concepts to this debate. Simple probability models of the key variables (wind power, plant on outage and electricity load) will be used to obtain algebraic expressions for capacity credit. One crucial goal in planning the development of a conventional grid is to ensure that there is sufficient generating plant installed such that the available plant at any time will rarely exceed unconstrained load.
