WECs and the West Coast of Canada
WCWI team members are developing WEC technology specific ProteusDS modules that are required to capture the salient characteristics of the power take off mechanism of each partnering WEC device. For example, some devices use hydraulics to drive the electrical generator while others rely on the water-air interface to drive an air-turbine. By adding proper PTO modules to the ProteusDS package, the project team will create an innovative flexible simulation framework for the WEC industry.
In terms of the WEC controllers applied in the simulation of WEC technologies, the study of WEC control in realistic irregular wave conditions is extremely topical. Under monochromatic wave excitation, Falnes showed that the complex mechanical impedance of the PTO with a perfectly stationary spar (a “one-body” WEC) should be “matched” to the WEC by setting it equal to complex conjugate of the WEC’s intrinsic complex mechanical impedance. However, in realistic polychromatic sea states, any theoretical PTO or WEC impedence adjustments can only be achieved with knowledge of the future wave motion – referred to as acausal control. To negotiate the dilemma of acausal control, non-linear simulations are now being used to evaluate non-linear, and mostly heuristic, control strategies using available WEC state information and model based predictions of the forthcoming wave elevation.
The power that you get from a WEC depends on where it is. In a location where there are lots of large waves you may get more power but the WEC may need to spend more time in a survivability mode.
The WCWI are looking at locations off the West Coast of Canada. We are using the information provided by the wave resource assessment team, at potential deployment sites, as inputs to the numerical models, to determine the actual potential power that can be extracted.
Different WECs respond differently to different wave heights and different time between waves (the time between waves is described as the wave period). A WEC may perform very well in certain wave conditions but this is only relevant if those conditions frequently occur in its deployment location. An example of a typical potential deployment location’s wave climate is below. This shows the amount of hours each year that a sea-state occurs and the sea-states are represented by a significant wave height (Hs) and a peak period (Tp).
For a potential deployment location, we can obtain the wave resource information and use this to determine the annual power estimates for each of our partners’ WEC and how this varies over the year. An example of one of the partners’ WECs and its response to the different sea-states is below. This shows the different sea-states and the percentage of the total time-averaged power that the WEC extracts in each sea-state.
This work allows us to build models that show the combined results of a WECs performance and its deployment location. The total yearly energy that can be obtained from a WEC at a certain deployment site off the West Coast of Canada is shown below. The percentages show the proportion of energy that is extracted in each sea-state.
