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In this paper the evaluation of the global wave energy potential is presented based on data from a global wind-wave model (validated and calibrated against satellite altimeter data) and buoy data (the WorldWaves database). The theoretical potential was computed first using all the available wave data and, in a second step, areas in which the power level is very low (P≤5kW/m) were excluded. Finally, in the third step, areas impacted by sea ice were removed. Annual and seasonal power distributions are presented both in tables and maps. The technical resource was also assessed for the west coast of Iberian peninsula showing a significant power decrease from north to south within only 500 km.

The European Wave Energy Atlas (WERATLAS), developed within a R&D European project, includes a wide range of annual and seasonal wave-climate and wave-energy statistics for 85 offshore data points distributed along the Atlantic and Mediterranean European coasts. The data used are results of the numerical wind-wave WAM model, implemented at ECMWF, and buoy data for the North Sea, Norwegian Sea, and Barents Sea. A full verification of WAM results against buoy and satellite altimeter data revealed that the accuracy of the results is very good for the North Atlantic, but the hindcasts quality is lower for the Mediterranean, probably due to poorer accuracy of the input wind fields. The patterns of power level and power directional distribution over the Northeastern Atlantic are presented along with the interannual wave and power variability. The wave power level is much lower in the Mediterranean, where it is not possible to find a general pattern for the power level and its directional distribution.

The nearshore wave energy resource in Portugal has been assessed through the development of ONDATLAS. This is an electronic atlas, compatible with Internet access, containing comprehensive wave climate and wave energy statistics for 78 points at about 20m water depth spaced variably ca.5-30km, 5 points at deep water, and 2 points at open ocean locations. The data were produced by a third-generation wind-wave model, complemented by an inverse-ray model that computes the directional spectra transformation from open ocean to the nearshore. Shoaling, refraction, bottom dissipation, and shelter by the coastline and/or neighboring islands are taken into account. ONDATLAS statistics comprise yearly and monthly values, variability and probability data for significant wave height, energy (mean) period, peak period and wave power, and directional histograms for wave and power direction. Joint probability distributions for various combinations of the above parameters are also available, as well as extreme values and return period for wave height and period parameters. A summary of the detailed verification of this model using long-term buoy measurements at four sites is presented. The main characteristics of ONDATLAS are described. The strong spatial variability that wave conditions exhibit at the coastal area are illustrated and a brief assessment of the nearshore resource at the Portugal mainland is presented.

An atlas of the European offshore wave energy resource, being developed within the scope of a European R&D program, includes the characterization of the offshore resource for the Atlantic and Mediterranean coasts of Europe in addition to providing wave-energy and wave-climate statistics that are of interest to other users of the ocean. The wave data used for compiling the Atlas come from the numerical wind-wave model WAM, implemented in the routine operation of the European Centre for Medium Range Weather Forecasts (ECMWF), in addition to directional wave measurements from the Norwegian offshore waters.

To evaluate the performance of a Wave Energy Converter (WEC) with realistic Power Take-Off (PTO) configurations, moorings, control systems and other contributions, time-domain models are required to deal with the non-linearities arising from the different elements of the energy chain. Future developers, in order to give a correct estimation of the expected power output of their devices, will have to apply these models and will be asked about the accuracy they can provide, particularly on what concerns the performance of the device in a determined location. A general mathematical outline of this approach was firstly proposed by Cummins by using, under linear assumptions, a classical way of representing the equation of motion of a floating body with a system of integro-differential equations with convolution terms that involve frequency-dependent coefficients. Many methods have been proposed, in literature, to solve this system in the most efficient and accurate way. Some of them relied on a direct numerical integration using standard methods for the solution of Ordinary Differential Equations, while, in turn, others are based on the approximation of the radiation convolution term with a determined number of linear sub-systems or properly chosen transfer functions. This paper presents a general scheme for a simple heaving single-body WEC, whose hydraulic Power Take-Off is coupled to a gas accumulator that serves as a storage device. Different time-domain methods will be used and compared. Particular attention will be paid to the accuracy of the performance calculation of this WPA. It is expected that the results of the simulations provide deeper understanding of the importance of the numerical parameters used in the estimation of the device performance and in this way will constitute an additional suggestion for the choice of a time-domain model for the evaluation of a WPA performance.

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The present paper deals with the influence of wave climate on the design specifications of the power take-off equipment and annual production of electricity by OWC wave power plants. A wave-to-wire model of the Pico plant developed in previous studies was used. In addition to the Pico, six other wave climates characteristic of areas in the northeastern Atlantic Ocean were used, with annual wave power levels ranging from about 14 kW/m to 54 kW/m. Apart from Pico, the remaining sites were selected in pairs with similar wave power levels but different variability, thus enabling the influence of these two wave climate parameters to be assessed separately. An analysis of the influence of the detail of wave height and period statistics on the annual production of electricity is also presented.