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www.sname.org/sname/mt October 2012 type drives mooring systems require- ments and there is great variety in the type of anchors proposed. Tidal devices gener- ally pursue bottom-mount structures, in which the sheer mass of the device or pil- ings provide the anchoring. As devices grow larger and potentially pursue deeper water depths for applications such as ocean cur- rent turbines, moored devices will be more common. Several developers are working through the design challenges of mooring a tidal device such that it is suspended o the sea oor at a predetermined depth in the water column. Wave devices typically use traditional ground tackle and anchoring systems that are common in the o shore industry today. Most designs have multiple (3 or more) anchors and use combinations of synthetic mooring lines and chains. Some devices require a more rigid mooring regime where the device must be tightly suspended in the wave resource, whereas other devices operate best with a relatively loose moor- ing con guration and will oat around in a prescribed watch circle. Simulation soft- ware is critical in the analysis of a device and its mooring system. Developers are focusing signi cant attention to advance simulation tools to ensure both survivability in storm conditions for a given resource environment and to optimize device performance in aver- age, expected conditions. Challenges MHK development in the U.S. is active and new discoveries are being made each day. Despite recent progress, challenges still exist. Most research and development con- ducted in the MHK eld is conducted using pub-lic funding; continued availability of public funding to bridge the development gap as devices mature towards commercial viability is critical. Furthermore, great strides have been made in the regulatory process and permitting, but sustained effort in this arena is still critical to help bolster the edg- ling industry and enable safe, e ective, and envi- ronmentally responsible demonstrations of MHK technology.Technology barriers must be overcome with analysis and testing, and proven with the accumulation of critical hours of device operation in relevant environments. Open- water test centers are critical in expediting the deployment of devices for testing and stimulating the feedback loop from doc- umented, at-sea performance to the engineering design process. Additionally, at-sea testing provides significant visibility and helps devel- opers prove their device to financiers, insurance agents, utilities, and other key stakeholders. MTBrian Lounsberry is a senior engineer with Cardinal Engineering. Workers complete ? nal assembly of Ocean Renewable Power Companys TidGen tidal turbine in Eastport, Maine. Go Deeper To learn more about marine and hydrokinetic devices, check out the following Web sites: www.water.energy.gov | www.oceanrenewable.com