In English

Efficient point absorbing wave energy converter configurations: influence of environment and array design

Charlene Vance
Göteborg : Chalmers tekniska högskola, 2018. 134 s.
[Examensarbete på avancerad nivå]

Waves are a sustainable energy resource that have significant potential for utilization. Point absorbing wave energy converters (WECs) use the heave motion of the waves to generate electricity. Configurations include the WEC buoy, mooring system, and electricity collection system. This thesis studies key parameters that affect the performance of the point absorbing WEC configuration through analyzing the power absorption of the WEC and fatigue life of the mooring lines. Waves4Power’s WaveEL 3.0 device, installed in Runde, Norway, is used as a baseline model for hydrodynamic and structural response simulations. Two versions of the WaveEL buoy are considered with different shaft lengths. The environmental conditions at various locations are studied. Basic arrays of three (TriBuoy) and four (SquareBuoy) are then designed. Single buoy configurations are simulated with the conditions found at various studied locations, while array configurations are simulated applying the environmental conditions found at Runde. Simulations are run through SESAM software. The results are then postprocessed in MATLAB. Fatigue life and power absorption are studied varying environmental parameters, mooring system, and WEC buoy version. Select configurations are further analyzed through an analysis of LCOE and LCA. The results show that optimal mooring line geometry depends on the depth at the location, and that optimal WEC buoy shaft length depends on the average sea conditions at the location. The best location in terms of power absorption for the WaveEL device is Garðskagi, Iceland. The array simulations at Runde show that small WEC separating distances will limit the mooring line length, which will result in lower power absorption and lower fatigue lives in the mooring lines. The LCOE shows that the SquareBuoy configuration is the most profitable, and that assuming a different sea state affects the calculated LCOE significantly. The LCA shows that the main process contribution to climate change is the manufacturing of the WEC buoy itself, and that the buoy with the longer shaft has a higher environmental impact per MWh produced. The final recommendations are to further explore the Garðskagi site for WEC farm potential, to use a mooring line geometry that is optimized depending on the water depth, to choose a large enough separating distance between WECs where the optimal mooring line geometry can be applied, and to focus on decreasing the costs and CO2 emissions associated with the manufacturing of the WEC buoy. It is also recommended to simulate for more sea states and run more analyses in further stages when more details are obtained about the sites and properties of the WEC system.

Nyckelord: fatigue, LCOE, LCA, point absorber, wave energy, WEC array, WEC mooring system

Publikationen registrerades 2018-08-07. Den ändrades senast 2018-08-07

CPL ID: 255648

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