Abstract
PacWave, a marine energy test facility off the coast of Oregon in the United States, is set to test various sizes and shapes of wave energy converters (WECs) over the next couple of years. The facility has energetic waters, subsea power cables, and on-land infrastructure ready to use for WEC developers wanting to test their devices. However, WEC developers do not always have mooring system components designed or acquired for device stationkeeping during testing, and PacWave does not own any mooring system components for developers to use. The challenge addressed in this report is to determine the best method of acquiring mooring system components for WECs expected to be tested at PacWave.
Not all WECs tested at PacWave will be of the same design; some may be similar in shape and function but may not be the same between developers. This means that the most cost-effective mooring system design for one WEC may not satisfy design criteria for another WEC. Therefore, other than designing and acquiring specific mooring system components for each WEC that is tested at PacWave, which can be expensive, mooring system components at PacWave can be designed to support a wide range of WEC sizes and functions while still satisfying all mooring design criteria at an affordable price. This report details the design process and potential acquisition costs of general mooring system components to be used at PacWave. A series of assumptions are initially defined that are used in the mooring design process, such as the expected types of WECs to be deployed at PacWave, the most common types of mooring system configurations, and the most common types of mooring line configurations. It is also assumed that the designed mooring systems would be temporary mooring systems, so that they could be repeatedly installed and uninstalled, rather than permanent mooring systems, which would remain installed on-site.
These assumptions, as well as the PacWave environmental conditions and other modeling assumptions, are used to design 43 different mooring systems consisting of various line configurations, layout orientations, and footprint sizes to serve two general styles of WECs. Each mooring line design has its line diameters, line lengths, and intermediate point masses or volumes sized to meet mooring design criteria and minimize cost. The results provide a wide range of mooring system designs that could potentially be used for various types of WECs deployed at PacWave, but a determination of specific mooring designs to be acquired was not made. However, a set of “acquisition scenarios” are detailed to provide a sense of the overall cost to acquire certain quantities of mooring system components.
Using these results, it is initially recommended that the most cost-effective mooring acquisition scenario would be for PacWave to purchase and retain the mooring system components used for the first few devices that are tested at PacWave from the developers, rather than purchase a predetermined set of components, as outlined in this report. This way, PacWave can slowly compile reliable and proven mooring system designs that can be reconfigured for future deployments.