Significant research is under way to determine the potential environmental effects of marine and hydrokinetic energy systems. This work, being guided and funded by the U.S. Department of Energy, is intended to address knowledge gaps and facilitate installation and operation of these systems.

A relatively new generation of waterpower technologies, broadly categorized as marine and hydrokinetic (MHK) energy systems, offers the possibility of generating electricity from water without dams and diversions. The potential power that could be derived from currents, tides, waves, and ocean thermal gradients is enormous, and there are numerous plans in the U.S. and internationally to develop these technologies.

But because the concepts are new, few devices have been deployed and tested in rivers and oceans, and even fewer environmental studies of these technologies have been carried out. Thus, their potential environmental effects remain mostly speculative.1,2,3,4 Movement is under way, particularly by the U.S. Department of Energy (DOE), to perform the research necessary to address the uncertainties about the environmental effects of MHK technologies, with a view toward getting devices in the water.

EISA report to Congress

To address some of these uncertainties, the U.S. Congress – in Section 633(b) of the Energy Independence and Security Act (EISA) of 2007 – called for a report that addressed:

– Potential environmental impacts, including impacts to fisheries and marine resources, of MHK technologies;

– Options to prevent adverse impacts;

– Potential role of monitoring and adaptive management in identifying and addressing any adverse environmental impacts; and

– Necessary components of such an adaptive management program.

The EISA Report was completed in 2009 by DOE, in conjunction with the departments of Commerce and Interior.5 The report focused on potential effects of MHK technologies on aquatic environments (rivers, estuaries, and oceans), fish and fish habitat, ecological relationships, and other marine and freshwater resources (such as marine protected areas and recreation). It identified nine potential environmental issues (see Table 1) and outlined possible mitigation measures.

Impacts to aquatic ecosystems will occur during installation and operation of MHK projects. Installation involves placement of the generating units, mooring cables or anchors, and electrical transmission cables to shore.

Possible operational environmental issues include alteration of river and ocean currents and waves, alteration of bottom substrates and sediment transport/deposition, impacts of noise and electromagnetic fields, chemical toxicity, and interference with animal movements and migrations. Designs that incorporate moving rotors or structures (tidal stream and river technologies, some wave technologies) pose the potential for injury to aquatic organisms from strike or impingement.

Another broad class of ocean energy systems, ocean thermal energy conversion (OTEC) technologies, will include impacts more akin to those of steam electric plants: alteration of water temperatures, entrainment, and impingement.

Although some have expressed concerns about the effects of even single MHK turbines, environmental evaluations are expected to focus primarily on impacts from deployment of large numbers of units, as well as the cumulative effects of developments when added to existing stresses on aquatic systems. For example, impacts to bottom habitats, hydrology, or underwater noise levels that are minor for one or a few units may become significant for large energy farms. In rivers, the effects of hydrokinetic turbines would occur in the context of impacts associated with boat traffic and water withdrawals and discharges. In the ocean, MHK developments must compete with aquaculture, offshore wind turbines, gas and oil platforms, defense-related activities, mining, merchant shipping, and recreational and commercial fishing.

The EISA Report noted the uncertainty associated with environmental impacts of these new technologies and concluded that for some environmental issues the potential effects will prove minor. Other issues, such as interference with animal movements and strike, may need to be monitored as part of project siting and licensing. Because potential impacts to aquatic systems will be device- and species-specific, not all issues will be a concern for every project.

DOE-supported research

To address these concerns and accelerate the environmentally sound development of MHK technologies, DOE is supporting a range of research and assessment activities related to the issues discussed in the EISA report. For example, in 2009 DOE issued two parallel funding opportunities for research and development on waterpower technologies. One was directed at industry partners and industry-led teams and included elements for MHK site-specific environmental studies and other projects that support market development (including research and development to address environmental issues). The second was directed at DOE laboratories to address technical challenges in water power development and market acceleration barriers.

Table 2 summarizes the environmental studies that are being supported from these funding mechanisms. Most of these projects are multi-year studies that publish interim progress reports.

Also, DOE; the Bureau of Ocean Energy Management, Regulation, and Enforcement (BOEMRE); and National Oceanic and Atmospheric Administration (NOAA) announced eight jointly funded research awards in October 2010.6 These awards are designed to address key environmental research questions surrounding ocean renewable energy and to fund the development of environmental research protocols to help provide greater regulatory certainty for developers.

In addition, DOE is funding efforts to improve the siting of MHK projects from an environmental standpoint. Best siting practices and tools for navigating the regulatory process are being developed by several organizations: