The great challenge of the 21st century to mitigate climate change requires generation of green electricity to be an achievable goal. One way of producing green electricity is through usage of wave energy converters which are devices that use the energy of the ocean waves to produce electricity. W4P Waves4Power AB is a company from Sweden, devoted to commercializing their wave energy converter called the WaveEl buoy. The WaveEl buoy is a point absorber that produces electricity by using the energy of the waves to run a hydraulic motor connected to a generator. The working principle of the buoy is to let a water piston oscillate in a tube with a water column. The water column exerts flow resistance forces on the piston as it oscillates, and these forces create a frame of reference upon which the hydraulic motor system may operate. There are leakage clearances at the sides of the water piston that allow for flow of water past the piston and associated with this flow are parts of the flow resistance forces. The flow resistance forces that are present due to water flow in the leakage clearances are calculated with the use of a flow resistance parameter and, in the literature, there is little investigation conducted as to the importance of this parameter. The goal of present thesis work was to investigate the effect on 4 parameters of the WaveEl buoy system (power captured from the waves, flow resistance force acting on the piston, mean piston position, and number of bumper hits) due to adoption of 3 different values of the flow resistance parameter. One of these values was the currently assigned value by Waves4Power at the time when this study was conducted. The value was the constant 0.75 and was a guess by Waves4Power. The other two values were received from a parallel thesis work done at Karlstad University by Linnéa Tebelius where, with the use of CFD, Tebelius calculated the flow resistance parameter with different levels of accuracy. The results of present thesis work were generated from simulations in a MATLAB Simulink model describing the dynamics of the WaveEl buoy system. Simulated time varied from 5.5 to 8.5 minutes per simulation. Generated results were compared to the results from using 0.75 as the value for the flow resistance parameter and showed that the energy captured from the waves was, at most, overestimated by approximately 13 % and underestimated by 6 %, depending on applied level of accuracy for description of the dynamic flow resistance parameter and simulated wave state. Furthermore, it was found that number of bumper hits varied extensively, in some cases from 0 to 47, between simulations where the only difference was applied value of the flow resistance parameter – further indicating that assigning a more accurate value on the dynamic flow resistance parameter may be of great importance when modelling the dynamics of the WaveEl buoy system.
| Identifer | oai:union.ndltd.org:UPSALLA1/oai:DiVA.org:kau-91258 |
| Date | January 2022 |
| Creators | Lundin, Alfred |
| Publisher | Karlstads universitet |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Student thesis, info:eu-repo/semantics/bachelorThesis, text |
| Format | application/pdf |
| Rights | info:eu-repo/semantics/openAccess |
Page generated in 0.0022 seconds