SIMULATION OF A TIGHT-MOORED AMPLITUDE- LIMITED HEAVING-BUOY WAVE-ENERGY CONVERTER WITH PHASE CONTROL

Abstract

A mathematical model is presented for a tight-moored heaving-buoy wave-energy converter, with a high-pressure hydraulic machinery for energy production and motion control. The buoy is cylindrical, has a diameter of 3.3 m, and the height is, at equilibrium, 3.1 m below mean water level and 2.0m above. A valve in the machinery can be actively controlled, and it is used to obtain largest possible power production, and to limit the excursion of the buoy, in order to protect the hydraulic machinery. In addition, an end-stop device is provided as a safety measure, in case the control fails to limit the excursion. For comparison a quite similar hydraulic machinery, without active control, is also investigated. A procedure is developed for control in irregular waves, and on the basis of a scatter table the year-average power production is estimated to be approximately 14.7kW for the buoy with control and 5.3 kW for the buoy without control. Further, a duration curve is presented, which shows that for the buoy with control the mean power production is between 10 kW and 20kW more than 70 % of the year. For the buoy without control more than half of the annual energy output is obtained in less than 20 % of the time. This shows that control will both