Final Report Summary - WAVESSG (Full-scale demonstration of robust and high-efficiency wave energy converter) Wave energy is a renewable, pollution free source of energy, able to contribute a lot in the field of renewable energy sources (RES) which currently attracts global research attention. Contemporary research challenges regarding wave energy are to obtain reliability on the technology, reduce the cost and increase the system efficiency. WAVESSG project aimed to develop, install and operate a full-scale SSG wave energy converter, with approximately 200 kW installed capacity, in 19 kW/m wave climate, including turbine, generator, and control system. The pilot structure would be a full-scale 10 m wide module, including three reservoirs to capture the ocean energy, constructed as a robust shoreline device. The patented multi-reservoir concept ensured that a variety of waves would be utilised for energy production, thus increasing the efficiency. In addition, the project involved the development of a patented multi-stage water turbine (MST), specifically designed for the SSG converter, which would enable the exploitation of different wave heights using a single turbine wheel. As a result, the energy supply to the grid would be smoother and the overall efficiency further increased. WAVESSG objectives were quantified as follows: 1. operate at full-scale one module of the SSG converter in 19 kW/m wave climate; 2. design a full-scale 150 kW technical prototype of the MST; 3. manufacture, test and install an MST prototype into the SSG structure; 4. design a full-scale 150 kW generator and control system equipment; 5. measure performance data of the SSG converter in a period of up to six months; 6. manufacture, test and install a full-scale generator and control system equipment for grid connection and annual production of 200 000 kWh; 7. obtain minimum hydraulic efficiency of 39 % for the shoreline application; 8. obtain a wave-to-weir efficiency of more than 25 % during the test period; 9. obtain 96 % availability of the plant with regard to operational hours and 10. obtain 85 % availability of production with regard to wave climate. During the initial project phase, the principal focus was to develop and design the optimum layout for the mechanical and electronic systems in the SSG, bearing in mind the system reliability and efficiency required. In addition, the development and construction of the MST was of major importance. The main challenge in this novel turbine design was the creation of a labyrinth seal to avoid air intrusion. Given the issues that occurred during MST preparation, which were difficult to overcome without significant delays, it was decided to equip the SSG with Kaplan turbines and increase efforts in order to be able to include the MST in the pilot plan for testing purposes, in addition to Kaplan turbines. The data acquisition system which was to be installed for the SSG monitoring would enable evaluation of the whole spectrum of waves, processing significant wave height, peak and energy periods. System specifications also included monitoring of the power in the overtopping, in the reservoirs, in the turbine, the power of generator and to the grid. All three SSG reservoirs would be equipped with pressure transducers, and the system would be designed to allow for the possible incorporation of other sources data. It was decided to use asynchronies generators, vertical frame, with belt drive transmission between them and the turbine. The synchronising of the generator with the grid would be controlled by a soft starter, in order to avoid inrush currents. Laboratory tests of this process were carried out, and their results were in accordance to the system requirements. The knowledge acquired during the SSG design and testing was disseminated through articles and publications, participations in conferences and project presentations, as well as through the creation of a website dedicated to the project. However, in spite of the fact that the progress was significant and the SSG had a building permit and was about to be installed, difficulties that arose due to objections raised against the construction by an individual proved impossible to overcome during the project duration. As a result, WAVESSG project had to stop before the installation and testing of SSG prototype. It was estimated though that the experience gained throughout the design will permit for the SSG pilot being installed and tested at a different location in the future. Related documents Final Report - WAVESSG (Full-scale demonstration of robust and high-efficiency wave energy converter)
