The Hydraulics & Maritime Research Centre (HMRC) is currently investigating the spectral composition of seaways that occur off the western seaboard of Ireland. This level of resource detail is important to wave energy development since most devices proposed to date have resonant responses, so the exact excitation frequencies forcing the machines must be known to accurately predict the performance. Typically a device’s annual production would be estimated from a scatter diagram for any sea area and a corresponding power matrix. However, within the occurrence of a certain wave height and period the spectral profile can vary from the classical shapes, such as Bretschneider and JONSWAP traditionally employed in both physical and mathematical modelling programmes. The validity for this assumption relative to the sea areas where WEC will be deployed is being checked by a number of methods such as plotting the bi-variate scatter plot against multiple temporal statistic, so the amount of deviation from a classical spectrum can be seen. The primary data source is a full year’s archive of Waverider buoy records from a 60m deep station just over one nautical mile from the western seaboard. This information is in the process of being extended by additional shorter duration measurements over the coming year at similar type sites.
In parallel a secondary investigation is being conducted into the fidelity of computer predicted spectra and whether this information can be relied upon for device evaluation. Simultaneous predicted records from a Regional WAM program run by Met Éireann, are being obtained and checked against the measured records. These are provided in the form of a full 3-dimensional energy density table of 30 frequencies and 24 directions output every 6 hours (with a 48 hourly forecast). A previous contract had verified the accuracy of the summary seaway statistics but this is the first time the spectral profiles have been investigated. This paper will present the preliminary findings from the study, with particular interest in the results from the analysis of a number of large storm occurrences during December 2006.