U.S. Department of Energy Reports on Environmental Effects of Hydropower

The U.S. Department of Energy (DOE) recently released the Report to Congress on the Potential Environmental Effects of Marine and Hydrokinetic Energy Technologies.

This report analyzes the potential environmental effects of technologies that capture energy from waves, tides, ocean currents, the natural flow of water in rivers, and marine thermal gradients. Since such marine and hydrokinetic technologies are not widely used at this point, their environmental effects are not well documented.

The report examined American and international peer-reviewed literature, project documents, environmental assessments, and observations from similar activities.

It focused on the potential effects on aquatic environments (i.e., rivers, estuaries, and oceans), fish and fish habitats, ecological relationships, and other marine and freshwater aquatic resources.

It described nine types of environmental effects that may occur and detailed how monitoring and adaptive management principles might be employed to evaluate and mitigate those effects. The report found no conclusive evidence that marine and hydrokinetic technologies will cause significant environmental effects, but it did highlight areas for future environmental research.

There are well over 100 conceptual designs for converting the energy of waves, river and tidal currents, and ocean temperature differences into electricity. Most of these ocean energy and hydrokinetic renewable energy technologies remain at the conceptual stage and have not yet been tested in the field. Most considerations of the environmental effects have been in the form of predictive studies and environmental assessments. Several common potential environmental effects include:

• Alteration of current and wave strengths and directions
• Alteration of substrates and sediment transport and deposition
• Alteration of habitats for benthic organisms
• Noise during construction and operation
• Generation of electromagnetic fields (EMF)
• Toxicity of paints, lubricants, and antifouling coatings
• Interference with animal movements and migrations, including entanglement
• Strike by rotor blades or other moving parts

In the case of ocean thermal energy conversion technologies, additional potential effects stem from the intake and discharge of large volumes of sea water; changes in temperatures, nutrients, dissolved gases, and other water quality parameters; and entrainment of aquatic organisms into the intake and the discharge plume.

Mitigation of environmental effects can involve:

1. Avoiding impact altogether by choosing not to take certain actions;
2. Minimizing impacts by limiting the degree or magnitude of the action;
3. Repairing, rehabilitating, or restoring the affected environment;
4. Reducing the impact over time by preservation and maintenance operations during the life of the technology;
5. Compensating for the impact by replacing or providing substitute resources.

The most certain way to mitigate potential impacts is to avoid environmentally sensitive areas. Such areas may be particularly fragile, exhibit high biological productivity or biodiversity, embody special cultural or environmental values (for exmaple, critical habitats for endangered species), or be vulnerable to major impacts from longer-range consequences like sedimentation.

For biological resources, impacts are likely to be reduced by avoiding installation during sensitive seasons; for example, during migrations of aquatic animals or reproductive periods for fish, marine mammals, and shorebirds. Structural and operational mitigation options are often unique to the technology or issue, and could include streamlining the shapes of non-generating structures, burial of electrical transmission cables, insulation against noise and EMF, protective screens to prevent entrainment or blade strike, and appropriate spacing of individual units or projects.

The Energy Independence and Security Act of 2007 required DOE to prepare this report, in consultation with the Department of Interior and the National Oceanic and Atmospheric Administration (NOAA).