Abstract
Ocean energy extraction has gained attention as a viable component of the energy portfolio of the future. While utility-scale wave and current energy installations have yet to become common, technologies are continuously being developed (U.S. Department of the Interior 2006; EPRI 2011) to take advantage of the vast and renewable ocean energy resources that have the potential to provide the ancillary benefits of reducing carbon emissions and improving energy security. A recent wave resource assessment conducted by the Electric Power Research Institute (EPRI; 2011) estimated a total available wave resource of 2,640 terawatt-hours (TWh) along the outer continental shelf of the United States (to the 200 m depth contour of the shelf). Additionally, the federal government estimated that capture of just 1/1000th of the current flow of the Gulf Stream would supply over 75 TWh of energy, which is approximately equivalent to 35% of Florida’s energy needs (U.S. Department of the Interior 2006). North Carolina (NC) could benefit economically from pursuing the development and utilization of ocean energy resources by taking advantage of access to the ocean along approximately 3,375 miles of coastline (NOAA 2002) and its history of economic success in the research and manufacturing sectors. The area of the relatively shallow continental shelf of NC out to a depth of 50 m exceeds the total shelf area for all other east coast states by a factor of two, so space for shallow-water renewable energy development is abundant off the NC coast. Pursuit of ocean energy by NC also has the potential to reduce its 2008 10% net import of electricity and its ranking as the 13th highest carbon dioxide emitting state in the country (U.S. Energy Information Administration 2010).
While the environmental impacts of marine hydrokinetic (MHK) devices are not generally expected to be extreme, they are under-studied at present because of the lack of utility-scale installations where observations and empirical information can be gathered. Nonetheless, risk assessments of potential environmental impacts of ocean energy devices on marine resources and habitats are necessary for any future ocean installation. In fact, requirements for consideration of several potential impacts are already included in federal and state regulations.
Interference with existing and anticipated human activities is another aspect of the potential environmental impacts of MHK devices that requires careful consideration. The rivers, estuaries, sounds, and nearshore ocean (≤ 15 m depth) shelf constitute locations for several extensive human activities and uses, so judging the level of conflicts and the means of minimizing negative interaction is an additional component of assessing environmental (human, in this case) impacts. Some locations such as ocean inlets, the surf, and other nearshore zones of the ocean are heavily used for multiple recreational and commercial activities, implying a need for spatially explicit planning to minimize conflicts.
Siting of MHK installations off of the NC coast will be based on the availability of wave, ocean current, and tidal current energy and the risk of environmental impacts on organisms and habitats, including aspects that are presently regulated or that may be regulated in the future, and serious conflicts with existing human uses of the coastal ocean. In addition, up-front consideration of potential future uses of the areas where the installations may be located may be necessary to reconcile concerns of various ocean stakeholders who may perceive MHK installations as threats to their interests and be compelled to object to commercial-scale MHK development.
This report addresses the potential environmental and ecological effects posed by commercial installations of ocean wave, ocean current, and tidal current energy generating devices. It does not detail the potential effects of prototype-scale devices, which will need to be considered to obtain permits for their test installations, but the issues that we raise will apply at a smaller scale and can be inferred from our assessment of commercial-scale effects. The report also addresses the temporal and spatial use of the ocean off of the coast of NC by humans and by fish and wildlife. An understanding of the temporal and spatial dynamics of potentially conflicting human uses and of uses by sensitive natural resources could lead to resolution of these conflicts through spatial or temporal segregation before they erupt and become an impediment to development.