“There is no conclusive evidence that marine and hydrokinetic technologies will actually cause significant environmental impacts,” notes the Department of Energy (DoE) in its report, Potential Environmental Effects of Marine & Hydrokinetic Energy Technologies prepared for the Congress.
The report analyses 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, without building new dams or diversions.
Marine and hydrokinetic technologies are not yet widely deployed, and their environmental effects are not well documented. DoE worked with the Department of Interior and the National Oceanic & Atmospheric Administration to highlight areas where further information and research is needed.
Based on peer-reviewed literature, project documents, environmental assessments and observations, the report describes 9 types of environmental effects that may occur and describes how monitoring and adaptive management principles could be employed to evaluate and mitigate any effects.
It says the range of technologies would not only benefit from the dissemination of information from site-specific monitoring of existing installations, but also from generalised research to understand the nature and severity of impacts associated with particular stressors common to many marine and hydrokinetic technologies.
Technologies have not yet been tested
“Few marine and hydrokinetic renewable energy technologies have been tested at full scale, and it is therefore difficult to resolve all of the uncertainties about their specific environmental effects,” it concludes.
“Assessment methods, such as ecological risk assessment, are available to identify and evaluate adverse impacts, and mitigation practices have been established to address many of these risks.”
DoE estimates more than 100 marine and hydrokinetic renewable energy technologies have been tried, with most remaining at the conceptual stage. “Consequently, there have been few studies of their environmental effects” and most considerations of environmental impacts have been in predictive studies and environmental assessments that have not been verified.
“The assessments identified common elements among these technologies that may pose a risk of adverse environmental effects,” it adds, ranging from alteration of currents and waves; alteration of substrates and sediment transport and deposition; alteration of habitats for benthic organisms; noise during construction and operation; emission of electromagnetic fields; toxicity of paints, lubricants, and antifouling coatings; interference with animal movements and migrations; and strike by rotor blades or other moving parts.
In the case of OTEC (Ocean Thermal Energy Conversion), “additional potential impacts stem from the intake and discharge of large volumes of sea water, temperature and other water quality changes, and entrainment of aquatic organisms into the intake and discharge plume.”
Learn from problems faced by other technologies
A sense of the significance of each issue can be gained from the studies published for other technologies on noise generated by similar marine construction activities, EMF emissions from existing submarine cables, environmental monitoring of active offshore wind farms, and others. “Experience with other, similar activities in freshwater and marine systems will also provide clues to effective impact minimisation and mitigation options that can be applied to these devices,” it adds.
“Some aspects of the environmental impacts are unique to the technologies and require operational studies to determine the seriousness of the effects and best mitigation options,” it notes. “Early information about undesirable outcomes could lead to the implementation of additional minimization or mitigation actions which could be subsequently re-evaluated.”
“The most certain way to mitigate potential impacts is to avoid environmentally sensitive areas,” it states.
FERC has guidance to ensure development
The US Federal Energy Regulatory Commission (FERC) is the agency responsible for licensing marine and hydrokinetic energy projects, and it has rules and guidance to “help ensure sound and orderly development,” the report explains.
“Environmentally sound development of ocean and hydrokinetic renewable energy technologies would not only benefit from the dissemination of information from site-specific monitoring of existing installations, but also from generalised research to understand the nature and severity of impacts associated with particular stressors common to many technologies.”