Vågenergiforskning I Svèrige: Slutrapport Etapp 5

The work within the Group for Wave Energy Research is commissioned by the Swedish Board for Energy Research. This report summarizes stage 5. A system study of an energy converter, the IPS-buoy concept indicates a cost optimum buoy diametre when the power plant is installed in the Baltic. Several parameters are studied. Results of measurements from real tests at sea with an IPS-buoy are used to estimate energy production and mooring forces. The optimum buoy will be costed more accurate in a following report. From foreign concepts - Salters ducks, Bristol Oscillating Cylinder, Lancaster Flexible Bags and Oscillating Water Column are costed for Swedish wave conditions. The result can only be used for comparison between the four concepts. The distribution 0f the currents in a power plant with intermediat DC-links is studied. It is shown by simulation that although some links are instantaneously currentless the total power production is little affected. The design of the system have to take these phenomenas into account. The ice in Swedish waters is quite a problem. It is shown that in the interesting areas for wave power, severe ice conditions as a mean appear every fourth year. The best methods to handle these problems is either to sink the devices when the ice comes or to have them submerged all the time. Wave energy could be used for other purposes than direct electricity production. For instance wave energy could be used for heating and desalination of sea-water. A study is made for a small isolated island where wave- and wind energy is supposed to be used. Another application for wave energy is propulsion. So called foil-propellers are useful for positioning of floating bodies. Cleverly attached to a wave power device it could reduce the mooring forces. It could work as a converter itself and also propel ships. Energy production from wave energy devices, has been studied to some extent. The results from the trials with the IPS-buoy have been used to estimate the energy production from scaled buoys in the Baltic. The effect of power saturation has been studied and a method to linearize in the frequency-domain is discussed. Equipment to control the damping (also locking) of a small model-IPS-buoy has been built and partly tested in Lake Lygnern. A computer program to determine mooring forces is under development. An asyncronous generator with a controllable power factor is going to be tested at the laboratory. This technique gives a better efficiency for the electrical system but less efficiency for the generator. The wave recordings at Hoburg (SMHI) has shown less value than expected compared to hindcastings. This however probably depends on leward effects