This study has described a time domain analysis of a floating buoy, oscillating in heave with a hydraulic PTO unit in regular monochromatic waves. It is fully understood that monochromatic sea waves do not occur in reality but it is useful to fully comprehend the operation of these complex WEC devices in regular waves before they can be investigated under more realistic conditions. It has been shown that a typical hydraulic PTO unit behaves similar to a Coulomb damper producing a square wave force rather than the sinusoidal nature of a viscous damper as previously assumed. The hydraulic PTO unit was modelled as both an ideal unit and a unit including losses so that a realistic power output and PTO unit efficiency could be predicted. The PTO unit efficiency was found to only vary slightly with wave height. It has been shown that a hydraulic PTO unit can be optimized, in the same manner as a viscous damper, by altering the motor displacement, which varies the effective damping of the unit. The optimum damping of the PTO unit has a linear relationship to wave period but only a minimal variation with wave height. The inclusion of losses in the model has no effect on the optimum values for the effective damping of the PTO unit. The optimum value is not the same as that of a viscous damper. However, all three cases investigated showed a similar trend for the optimum PTO force amplitude against wave period. This implies that for a given wave period, regardless of PTO design, there is an optimum force amplitude which the PTO unit should produce to maximize the power generated.
Determination of optimal parameters for a hydraulic power take-off unit of a wave energy converter in regular waves
Bestimmung der optimalen Parameter für ein Wasserkraftwerk mit Wellenenergiewandler in regelmäßigen Wellen
2012
14 Seiten, 19 Bilder, 4 Tabellen, 18 Quellen
Aufsatz (Zeitschrift)
Englisch