EXPERIMENTS AT ISLANDSBERG ON THE WEST COAST OF SWEDEN IN PREPARATION OF THE CONSTRUCTION OF A PILOT WAVE POWER PLANT Stefan Gustafsson 1 , Olle Svensson 1 , Jan Sundberg 1 , Hans Bernhoff 1 , Mats Leijon 1 , Oskar Danielsson 1 , Mickael Eriksson 1 , Karin Thorburn 1 , Kerstin Strand 2 , Urban Henfridsson 2 , Ellerth Ericsson 3 , Karl Bergman 3 , 1 Swedish Centre for Renewable Electric Energy Conversion Division for Electricity and Lightning Research, Department of Engineering Sciences Uppsala University, Sweden 2 Vattenfall Utveckling AB, Sweden 3 Vattenfall AB, Sweden ABSTRACT For testing and evaluating purposes, a pilot wave power plant is under construction at Islandsberg on the West Coast of Sweden. The concept suggested for wave energy conversion consists of a surface following buoy, a point absorber, connected to a three-phase permanent magnetised linear generator placed at the seabed. The motions of the buoy drive a piston in the generator, thereby converting the energy of the waves into electric energy. This paper describes the test site and the two measurement set- ups that are in use in order to receive information for the design and optimisation of the direct driven linear generator. A Datawell Waverider buoy provides wave data in the form of time series of wave elevation and wave variance spectra. The second set- up, built in house, measures loads on a full-scale point absorber. INTRODUCTION Wave energy is a renewable source, which has not yet been exploited to a large extent. Even though the major portion of Europe’s potential wave energy resources is found offshore, near-shore waters with a calmer wave climate hold a substantial amount of energy (EU report, 1992). Examples of well-known full-scale sea trials for energy conversion are AWS (Waveswing, 2005), Pelamis (Oceanpd, 2005) and “Mighty Whale” (Washio et al., 2000). The overtopping construction TAPCHAN and OWC’s, such as the Pico and the LIMPET plant, are examples of full-scale shoreline devices (WaveNet, 2003). A concept involving a surface following buoy, a point absorber, connected to a three-phase permanent magnetised linear generator placed at the seabed is studied here. The motions of the buoy drive a piston in the generator, thereby converting the energy of the waves into electric energy. A previous study (Leijon et al., 2005) used FEM based computer simulations to investigate the possibility of using three-phase permanent magnet linear generators for wave energy conversion. Their results indicate that small units, ranging down to 10 kW, producing electricity through wave energy can have an impact on tomorrow’s new sustainable electricity production. The technology of the linear generator is assumed to be somewhat depth independent and the unit size of 10 kW for power conversion is assumed to match a significant wave height in the range of 2 m, found in near shore and sheltered waters. A wave power plant consisting of a number of small wave energy converters using linear generators should therefore be useful for harvesting the wave energy of coastal areas see figure 1. The simulations indicate the possibility for electrical power production in places with comparatively small wave heights but further simulations and experimental verifications are needed since the results are based on a simplified buoy-wave interaction model. For testing and evaluating purposes a pilot wave power plant is under construction at Islandsberg on the West Coast of Sweden. Figure 1 Array of linear generators, illustrated by Karl Åstrand. At present, two measurement set-ups are in use in order to receive information valuable for the design and optimisation of the direct driven linear generator. The first equipment, a Datawell Waverider buoy, was launched in April 2004. It provides time series of wave elevation to the computer simulations. The second set-up, launched in March 2005, is an 1