Challenges and Issues of Wave Energy Conversion

rickWave Energy News

Technical, Environmental and Permitting Challenges Facing Wave Energy Conversion for the California Coast This article summarizes the status of ocean wave energy technology and some of the challenges facing its development Cost environmental, permitting and regulatory issues, especially as they pertain to the U.S. West Coast, are also summarized.


California is blessed with energetic ocean waves and a continental shelf that deepens quickly seaward, producing a wave energy resource relatively close to shore. Placing wave energy converters (WECs) close to shore minimizes both project cost and ocean wave suppression by friction. The resource availability is matched by a sizeable coastal population with large energy needs. By contrast, the East Coast of the United States has a very wide, shallow continental shelf, which induces a large amount of bottom friction loss to the incident waves. The minimum depth contour at which there is little or no energy in wave energy due to bottom friction is normally around 90 meters in depth.

California’s Pacific Coast stretches over roughly 11.5[degrees] of latitude, extending from about 32.5[degrees] N to 44[degrees] N. This offers roughly 900 nautical miles of coastline with opportunity for WECs. Generally, the northern and central zones are characterized by high waves of relatively low frequency and the southern coast is characterized by low waves of higher frequency.

WEC Challenges

One of the major obstacles with any wave resource study is lack of long-term ocean wave measurements inside the 100-meter-depth contour, where refraction effects result in spatially inhomogeneous wave parameters. Lack of data makes it difficult or impossible to mark the optimum locations for WECs. Visual inspections could lead to places with good but short-term yield or to places with sporadic surges exceeding the safety threshold. An ideal WEC site would supply consistent power throughout the year, which of course is precluded by seasonal weather variation and wind patterns.

These unavoidable variations in wave parameters also impose changes in WEC outputs. When the WEC runs at wave conditions below what it is designed for, it is called part-load operation. Similarly, wave conditions exceeding design conditions impose overload operation. At these two operating conditions, WEC output is reduced (i.e., the energy conversion efficiency drops). The overload could also lead to significant structural damage.

Thus, load variation is unavoidable in WECs, and the variations can be inherent to the cycle of the wave itself or could be imposed as a result of external conditions, such as weather profile, bathymetry and surface friction.

The pressure exerted on a WEC by a rising water column changes in quantity and direction, maxing just before the wave height peaks. Then, both the flow rate and the pressure drop to zero during the transition, when the flow direction changes from blow to suction. In addition to the external factors impacting WEC load, this wave cycle also imposes a variable load on conversion devices, and it is inherent to the wave phenomenon. For any given wave height and period, the part-load range can be projected, and WEC devices can be suited to be less impacted by this internal load variation. Thus, a WEC system must be sized for maximum efficiency at part load, but it also should be designed with flexibility to capture all or most of the available wave energy. Balancing these two objectives remains a serious challenge to developing WECs. Only extreme values of weather- imparted load variations can be estimated. So far, these extreme values, such as rare and transiently strong waves, can be accommodated more as safety factors than for energy recovery. Other challenging issues include identifying suitable sites for deployment and matching a proper technology to such sites. Reliability, maintainability, grid connection and system control also remain serious challenges.

Research and Cost

One of the most critical obstacles to developing WEC technology in California is the lack of research support to motivate coordinated efforts in advancing the technology. In contrast, the European Commission has increased its support for WEC projects since the beginning of the Joule Program.2,3 The last decade of research and development represented more than 20 large projects backed by hundreds of millions of dollars. The “Atlas of Wave Energy Resource in Europe” and the “Exploitation of Tidal and Marine Currents” are two prime contributions of the last decade. The European combined efforts also produced two outstanding pilot projects: the Pico and the Limpet plants now in operation. Furthermore, in 1999, the European Commission invited 14 wave energy representatives from various European countries to cooperate in the European Thematic Network on Wave Energy. The project addresses important scientific, technical and economic issues and aims to produce a variety of guidelines in the areas of standards, recommendations, software, research and development, support base and outreach. Research and development on WECs is also conducted in a number of countries outside Europe, including Australia, Canada, China, India, Israel, Japan, Sri Lanka, Indonesia, Iran, Korea, Mexico and Russia. The United States has little WEC research in progress, and no large deployment is anticipated in the near future. Government and institutional support has been modest.

As a latecomer to the table, WEC technology is still not widely recognized in North America as an alternative source of renewable energy. The lack of institutional funding and miniscule research support have kept the estimated cost of installation relatively high, and this in turn has kept interest in WECs very low.

WECs are not benefiting from the heavy institutional support that other renewable forms of energy conversion techniques continue to enjoy, helping these technologies become cost-competitive.

It is unlikely that WEC technology will show any significant growth in North America in the foreseeable future without drastic changes in institutional support.

Environmental Issues

To date, there is a limited amount of data available on the environmental impact of wave farms that are in continuous operation. In one study, however, T. W. Thorpe examined the potential environmental impacts of various technologies. Relative to other forms of electric generation, including other renewable sources such as sunlight or wind, wave energy conversion is expected to cause little adverse environmental impact.

Once the wave farm is installed, the main impacts will come from increased operational activity to maintain the devices.

Some of the potential effects include wave hydrodynamics (the transport of sediments along the shorelines), creation of artificial habitats (attachment surfaces for a variety of algae and invertebrates), change of migration route for marine mammals, noise, navigational hazards, visual effects and impacts on some forms of recreation, such as scuba diving and jet skiing.

Regulatory Issues

Several federal, state and local authorities would have overlapping jurisdiction over a WEC project. An exhaustive list of the maritime boundaries recognized by local, state, federal and international law is beyond the scope of this report.

The following is a summary for a California scenario:

River and Harbors Act. Section 10 of this act prohibits the obstruction or alteration of navigable waters of the United States without a permit from the U.S. Army Corps of Engineers (USAGE).

Title 33 Navigation and Navigable Waters. The district commanders of the U.S. Coast Guard have the authority to determine whether an obstruction in the navigable waters of the United States is a hazard to navigation and, if so, what markings (lights, fog signals, etc.) must be placed on or near the obstruction for the protection of navigation.

Wafer Pollution Control Act (Clean Water Act)/CalHornia Porter- Cologne Water Quality Control Act of 1970. This act prohibits the discharge of dredged or fill material into waters of the United States without a permit from the USAGE.

Marine Protection, Research and Sanctuaries Act. Section 103 of this act authorizes the USAGE to issue permits for the transportation of dredged material for the purpose of dumping it into ocean waters.

Federal Power Act. This act provides for federal regulation and development of water power and resources, authorizing the Federal Energy Regulatory Commission (FERC) to issue licenses for hydroelectric project works, including dams and reservoirs, to develop and improve navigation and to develop, transmit and use power.

FERC has recently indicated that it considers WEC technology to fall under the category of hydroelectric project works.

Coastal Zone Management Act (CZMA)/California Coastal Act. In conjunction with the federally approved California Coastal Management Program authorized by the CZMA, the California Coastal Act of 1976 established the California Coastal Zone and placed it under the jurisdiction of the California Coastal Commission.

Submerged Lands Act/California State Lands Act. The Submerged Lands Act grants coastal states title to offshore lands within their historic boundaries, as well as the rights to the natural resources on or within those lands. The federal government relinquishes its claims to the lands and resources, but maintains the right to regulate offshore activities for national defense, international affairs, navigation and commerce. Endangered Species Act/Fish and Wildlife Coordination Act. Section 7 of the Endangered Species Act directs all federal agencies to consult with the U.S. Fish and Wildlife Service and the National Marine Fisheries Service to ensure that the actions they authorize, fund or carry out do not jeopardize listed species or destroy or adversely modify critical habitats.

National Environmental Policy Act (NEPA). NEPA requires that environmental consequences and alternative actions must be considered before a decision is made by an agency to implement a federal project. If the project does not fall within the category of actions designated as categorical exclusions or requiring an environmental impact statement, the agency must prepare an environmental assessment.

California Environmental Quality Act (CEQA). This act represents the state counterpart of the federal NEPA regulations. CEQA requires that project proponents study and disclose a project’s anticipated environmental impacts and specify means to avoid or minimize those impacts.

California Endangered Species Act (CESA). This act generally parallels the main provisions of the Federal Endangered Species Act and is administered by the California Department of Fish and Game.

CESA establishes a petitioning process for the listing of threatened or endangered species.

Other federal and state laws may also govern or affect the processing and evaluation of applications for WEC development.


There are serious technical and bureaucratic challenges to harnessing wave energy in California and the United States. The regulatory process is complex and expensive. One simple measure that could advance this clean technology is establishing a point of contact, one office that will be in charge of permits on behalf of all legal and formal stakeholders. Such an office could combine the state and federal interests and implement all existing laws and requirements on behalf of the governing and overseeing regulatory bodies. The combined administrative process and complexity of jurisdictional modus operand! unduly burdens the progress of the technology.


This paper was extracted from a larger report on California wave energy resource evaluation, a project funded by the California Energy Commission. The authors are thankful to the commission for supporting and funding the project.

“It is unlikely that WEC technology will show any significant growth in North America in the foreseeable future without drastic changes.”

By Dr. Asfaw Beyene


San Diego State University

San Diego, California


Dr. James H. Wilson

Chief Scientist

Renewable Energy Division

Planning Systems Inc.

San Clemente, California


For a complete list of references, contact author Asfaw Beyene at

Visit our Web site at, and click on the title of this article in the Table of Contents to be linked to the respective company’s Web site.

Dr. Asfaw Beyene received his Ph.D. from Warsaw University of Technology in mechanical and aerospace engineering. He has taught at San Diego State University since 1989. Specializing in energy systems and renewable energy, he has received many awards, attracted several funded projects and has been published in various journals.

Dr. lames H. Wilson, of Planning Systems Inc., is one of the two principal investigators for the California Energy Commission’s Wave Energy Resource Study and has begun design studies for two wave energy projects along the California coast. Wilson has published numerous recent articles on wave energy.

Copyright Compass Publications, Inc. May 2008

(c) 2008 Sea Technology. Provided by ProQuest Information and Learning. All rights Reserved.

Source: Sea Technology


rickChallenges and Issues of Wave Energy Conversion