The development of the Pelamis wave energy converter from its conceptual origins to its commercial deployment is reviewed. The early emphasis on designing for survivability and favourable power absorption characteristics focused attention towards a self-referenced articulated line-absorber in an attenuator orientation. A novel joint and control system allow the machine to be actively tuned to provide a resonant response power amplification in small and moderate seas. In severe seas, the machine is left in its default or natural condition, which is benign and non-resonant. Hydraulic rams at the joints provide the primary power take-off with medium-term storage in high-pressure accumulators yielding smooth electricity generation. Land-based modular construction requiring minimal weather windows for rapid offshore installation is an essential engineering feature necessary for viable commercialization. The second-generation Pelamis designs built for E.ON and ScottishPower Renewables are presented, and the scope for further cost reduction and performance enhancements are explained.

[1] Using a large collocated data set of altimeter and buoy measurements, we examine the relationship between the altimeter Ku-band measurements of significant wave height, H s , backscatter coefficient, s 0 , and the buoy wave period. This is used to derive an empirical altimeter wave period model for TOPEX, Poseidon, Jason-1, ERS-2, Envisat, and GEOSAT follow-on. We show that there is a step change in the response of s 0 at around 13 dB and above this value s 0 is not related to wave period. The results are compared to algorithms proposed by two previous authors (Gommenginger et al., 2003;Quilfen et al., 2004) and examined in terms of absolute accuracy (RMS error), ability to replicate the joint distribution of wave height and period, and residual trends with various parameters. The new algorithm is shown to perform better than the previous algorithms in all metrics considered. Finally, we demonstrate that there is a limiting accuracy achievable for a function of the form f(H s , s 0 ) and that our model comes close to this.Citation: Mackay, E. B. L., C. H. Retzler, P. G. Challenor, and C. P. Gommenginger (2008), A parametric model for ocean wave period from K u band altimeter data,

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A general and widely applicable methodology to assess and present the performance of wave energy converters (WEC) based on sea trials is presented. It is meant to encourage WEC developers to present the performance of their WEC prototypes, on a transparent and equitable way while taking care of possible discrepancy in the observed performance of the WEC. Due to the harsh uncontrollable conditions of the sea that is encountered by WECs during sea trials, some of the performance of the WECs might be sub optimal and the data sets not fully complete. The methodology enables to filter the data by applying a selection criterion on the performance data that was obtained for a certain range of wave conditions. This selection criteria result in a subset of performance data representing the performance of the WEC for specific wave conditions, from which an average value an appreciation of the related uncertainty can be derived. This can lead to the estimation of the annual energy output of the WEC at its test location, while it also provides a method to estimate its annual energy output for another location of interest and possibly also at another scaling ratio. The same methodology can also be used to perform parametric studies with environmental or device dependent parameters and to analyse the power conversion chain from wave to wire, which both could lead to an enhanced understanding of the performance and behaviour of the WEC. The same methodology is also applicable to tidal devices or any other developing technologies that are used in an uncontrollable environment