considerations and multiple- or competing-use issues such as fisheries or recreation. Such filters are, by nature, specific to the local sites where decisions related to MHK projects will be made. The practical filters can greatly influence the timing of the permitting process and can lead to unpredictable consequences, which in turn can affect a project’s economic viability. Box 1-2 presents two scenarios to help elucidate the differences between the theoretical, technical, and practical resource.
MHK resource assessments are going to be of interest to a variety of parties, including electric utilities, project developers, and public officials. However, the orders-of-magnitude differences between theoretical, technical, and practical resources need to be stressed, especially because some resource assessments have been publicized in terms of a national or regional single-number estimate. To provide a better understanding of the difference among these resources, two scenarios are provided below.
• Scenario 1. A local official examines one of the MHK GIS databases and notes that there is a 100 MW theoretical resource nearby. After taking into account the efficiency of the extraction device, such as a turbine (30%), coverage of the resource by the device(s) (20%), and the efficiency of connecting the extracted energy to the electricity grid (90%), the technical resource amounts to only 5.4 MW. The local official notes that 50 percent of the remaining power would interfere with existing fisheries and navigation routes in the area, leaving a practical resource of 2.7 MW.
• Scenario 2. A developer is interested in building a 100 MW MHK plant. This would be considered the desired practical resource. In this case, 20 percent of the site is unavailable because it is in a Marine Protected Area. After taking into account device efficiency, site coverage, line efficiency, and the practical constraints posed by the use conflict, the site of interest would have to be endowed with a theoretical resource of 2,300 MW.