The chapter reviews the current state of knowledge in wave resource assessment. It starts by introducing the basic concepts and definitions used to describe ocean waves. The mathematical description of wave propagation and kinematics is presented and the notions of wave spectra and spectral parameters are discussed.
The main sources of wave data from measurements and modeling are described in detail. Measurements from moored buoys and satellite altimeters and data generated by spectral wave models are compared, highlighting important aspects and limitations to be aware of when using each source of data.
The variability of the wave resource on multiple scales is discussed and the impact this has on the predictability of energy yield of a wave energy converter is considered.
The topic of estimating extreme conditions is discussed in detail. Models for the short-term distribution of individual wave and crest heights are reviewed, together with methods to estimate the long-term distribution of extreme sea states. Finally, methods for the combination of short-term and long-term distributions to estimate return values of individual wave or crest heights are presented.