Technology White Paper 

on 

Wave Energy Potential on the U.S. Outer Continental Shelf 

Minerals Management Service 

Renewable Energy and Alternate Use Program 

U.S. Department of the Interior 

Available for Downloading at http://ocsenergy.anl.gov 

May 2006 
 1 

WAVE ENERGY POTENTIAL ON THE U.S. OUTER CONTINENTAL SHELF 

INTRODUCTION 

With the passage of the Energy Policy Act of 2005 (EPAct), Public Law 109-58 (H.R. 6), 

the Minerals Management Service (MMS), a bureau of the U.S. Department of the Interior, was 

given jurisdiction over Renewable Energy and Alternate Use Program projects, such as wind, 

wave, ocean current, solar energy, hydrogen generation, and projects that make alternative use of 

existing oil and natural gas platforms in Federal waters. A new program within MMS has been 

established to oversee these operations on the U.S. Outer Continental Shelf (OCS). MMS is 

developing rules to guide the application and permitting process for development of Renewable 

Energy and Alternate Use Program projects on the OCS. To apply the requirements of the 

National Environmental Policy Act (NEPA) in the establishment of national offshore alternate 

energy development policy and a national alternate-energy-related use program and rules, MMS 

plans to prepare a programmatic environmental impact statement (Programmatic EIS). The 

Programmatic EIS process will (1) provide for public input concerning the scope of national 

issues associated with offshore alternate-energy-related use activities; (2) identify, define, and 

assess generic environmental, sociocultural, and economic impacts associated with offshore 

alternate-energy-related use activities; (3) evaluate and establish effective mitigation measures 

and best management practices to avoid, minimize, or compensate for potential impacts; and 

(4) facilitate future preparation of site-specific NEPA documents—subsequent NEPA documents 

prepared for site-specific Renewable Energy and Alternate Use Program projects will tier off of 

the Programmatic EIS and Record of Decision. The Programmatic EIS will evaluate the issues 

associated with development, including all foreseeable potential monitoring, testing, commercial 

development, operations, and decommissioning activities in Federal waters on the OCS. 

Information defining the issues and current technology will be obtained primarily from Federal 

research organizations, MMS, industry, and other valid sources. 

In preparation for the Programmatic EIS, MMS has developed a series of White Papers 

on topics of interest to the Renewable Energy and Alternate Use Program. The overall objective 

of the White Papers is to provide sufficient information on the prospective alternative 

technologies to support assessments of the potential environmental impacts of the technologies 

and of the viable impact mitigation strategies in the Programmatic EIS. The White Papers also 

will serve as sources of information for stakeholder outreach. 

This paper discusses the generation of energy from ocean waves on the U.S. OCS. 

Resource potential and technologies for capturing the energy in the waves are discussed.1 Major 

environmental and economic considerations that can be surmised from available literature at this 

time for the development of this energy resource are listed. Companion papers in the series 

address the generation of energy on the OCS from wind, solar radiation, and ocean currents, and 

 

1 Reference herein to any specific commercial product, process, or service by trade name, trademark, 

manufacturer, or otherwise does not represent its endorsement, recommendation, or favoring by MMS, the 

United States government, or any agency thereof. 
 2 

the transportation of energy generated on the OCS to onshore as electricity or in the form of 

hydrogen. 

RESOURCE POTENTIAL 

Ocean waves represent a form of renewable energy created by wind currents passing over 

open water. Capturing the energy of ocean waves in offshore locations has been demonstrated as 

technically feasible. Also, basic research to develop improved designs of wave energy 

conversion (WEC) devices is being conducted in regions such as near the Oregon coast, which is 

a high wave energy resource (Rhinefrank 2005). Compared with other forms of offshore 

renewable energy, such as solar photovoltaic (PV), wind, or ocean current, wave energy is 

continuous but highly variable, although wave levels at a given location can be confidently 

predicted several days in advance. 

The common measure of wave power, P, is 

π

ρ

32

2 2 g TH P =

 watt per meter (W/m) of crest length (distance along an individual crest), 

where: 

ρ = the density of seawater = 1,025 kg/m3, 

g = acceleration due to gravity = 9.8 m/s/s, 

T = period of wave (s), and 

 

H = wave height (m). 

Because wind is generated by uneven solar heating, wave energy can be considered a 

concentrated form of solar energy. Incoming solar radiation levels that are on the order of 

100 W/m2 are transferred into waves with power levels that can exceed 1,000 kW/m of wave 

crest length. The transfer of solar energy to waves is greatest in areas with the strongest wind 

currents (primarily between 30° and 60° latitude), near the equator with persistent trade winds, 

and in high altitudes because of polar storms. 

Waves are also efficient transporters of solar energy. Storm winds generally create 

irregular and complex waves. In deep water, after the storm winds die down, the storm waves 

can travel thousands of kilometers in the form of regular smooth waves, or swells, that retain 

much of the energy of the original storm waves. The energy in swells or waves dissipates after it 

reaches waters that are less than ~200 m deep. At 20-m water depths, the wave’s energy typically 

drops to about one-third of the level it had in deep water. 
 3 

The total annual average wave energy off the U.S. coastlines (including Alaska and 

Hawaii), calculated at a water depth of 60 m has been estimated (Bedard et al. 2005) at 

2,100 Terawatt-hours (TWh) (2,100 × 1012 Wh).2

Estimates of the worldwide economically recoverable wave energy resource are in the 

range of 140 to 750 TWh/yr for existing wave-capturing technologies that have become fully 

mature (ETNWG 2003). With projected long-term technical improvements, this could be 

increased by a factor of 2 to 3 (Thorpe 1999). The fraction of the total wave power that is 

economically recoverable in U.S. offshore regions has not been estimated, but is significant even 

if only a small fraction of the 2,100 TWh/yr available is captured. (Currently, approximately 

11,200 TWh/yr of primary energy is required to meet total U.S. electrical demand.) WEC 

devices have the greatest potential for applications at islands such as Hawaii because of the 

combination of the relatively high ratio of available shoreline per unit energy requirement, 

availability of greater unit wave energies due to trade winds, and the relatively high costs of 

other local energy sources. 

RESOURCE UTILIZATION TECHNOLOGIES 

A variety of technologies have been proposed to capture the energy from waves; 

however, each is in too early a stage of development to predict which technology or mix of 

technologies would be most prevalent in future commercialization. Some of the technologies that 

have been the target of recent developmental efforts and are appropriate for the offshore 

applications being considered in this assessment are terminators, attenuators, point absorbers, 

and overtopping devices. 

Terminators 

Terminator devices extend perpendicular to the direction of wave travel and capture or 

reflect the power of the wave. These devices are typically installed onshore or nearshore; 

however, floating versions have been designed for offshore applications. The oscillating water 

column (OWC) is a form of terminator in which water enters through a subsurface opening into a 

chamber with air trapped above it. The wave action causes the captured water column to move 

up and down like a piston to force the air though an opening connected to a turbine. A full-scale, 

500-kW, prototype OWC designed and built by Energetech (2006) (Figure 1) is undergoing 

testing offshore at Port Kembla in Australia, and a further project is under development for 

Rhode Island. 

 

2 This estimate was made at a specified water depth of 60 m (irrespective of the distance from the shore at which 

that depth occurs) in order to allow comparisons of wave energies between coastal areas and to eliminate the 

possible, but unpredictable loss of energy of the wave through its interactions with the sea bottom (scouring) at 

shallower depths. Typical wave energy in U.S. offshore regions ranges from 2 to 6 kW/m in the mid-Atlantic, 

12 to 22 kW/m in regions such as Hawaii with trade winds, and 36 to 72 kW/m in northwestern U.S. coastal 

areas near Washington and Oregon. 
 4 

 

FIGURE 1 Oscillating Water Column (Source: Energetech 2006) 

In an Electric Power Research Institute (EPRI)-cosponsored study (Bedard et al. 2005), a 

design, performance, and cost assessment was conducted for an Energetech commercial-scale 

OWC with a 1,000-kW rated capacity, sited 22 km from the California shore. With the wave 

conditions at this site (20 kW/m average annual), the estimated annual energy produced was 

1,973 MWh/yr. For a scaled-up commercial system with multiple units producing 

300,000 MWh/yr, the estimated cost of electricity would be on the order of $0.10/kWh. 

Another floating OWC is the “Mighty Whale” offshore floating prototype, which has 

been under development at the Japan Marine Science and Technology Center since 1987 

(JAMSTC 2006) 

Attenuators 

Attenuators are long multisegment floating structures oriented parallel to the direction of 

the wave travel. The differing heights of waves along the length of the device causes flexing 

where the segments connect, and this flexing is connected to hydraulic pumps or other 

converters. The attenuators with the most advanced development are the McCabe wave pump 

and the Pelamis by Ocean Power Delivery, Ltd. (2006). 

The McCabe wave pump (Figure 2) has three pontoons linearly hinged together and 

pointed parallel to the wave direction. The center pontoon is attached to a submerged damper 

plate, which causes it to remain still relative to fore and aft pontoons. Hydraulic pumps attached 

between the center and end pontoons are activated as the waves force the end pontoons up and 

down. The pressurized hydraulic fluid can be used to drive a motor generator or to pressurize 

water for desalinization. A full-size 40-m prototype was tested off the coast of Ireland in 1996, 

and commercial devices are being offered by the manufacturer. 
 5 

FIGURE 2 McCabe Wave Pump (Source: Polaski 2003) 

A similar concept is used by the Pelamis (designed by Ocean Power Delivery Ltd. 

[2006]), which has four 30-m long by 3.5-m diameter floating cylindrical pontoons connected by 

three hinged joints (Figure 3). Flexing at the hinged joints due to wave action drives hydraulic 

pumps built into the joints. A full-scale, four-segment production prototype rated at 750 kW was 

sea tested for 1,000 hours in 2004. This successful demonstration was followed by the first order 

in 2005 of a commercial WEC system from a consortium led by the Portuguese power company 

Enersis SA. The first stage, scheduled to be completed in 2006, consists of three Pelamis 

machines with a combined rating of 2.25 MW to be sited about 5 km off the coast of northern 

Portugal. An expansion to more than 20-MW capacity is being considered. A Pelamis-powered 

22.5-W wave energy facility is also planned for Scotland, with the first phase targeted for 2006. 

The EPRI wave energy feasibility demonstration project has selected the Pelamis as one 

of the technologies for design, performance, cost, and economic assessment (Bedard et al. 2005). 

Sites for evaluation were selected off the coasts of Hawaii (15.2 kW/m average annual wave 

energy), Oregon (21.2 kW/m), California (11.2 kW/m), Massachusetts (13.8 kW/m), and Maine 

(4.9 kW/m). For systems at these sites scaled to a commercial level generating 300,000 MWh/yr, 

the cost of electricity ranged from about $0.10/kWh for the areas with high wave energy, to 

about $0.40/kWh for Maine, which has relatively lower levels of wave energy. 

Point Absorbers 

Point absorbers have a small horizontal dimension compared with the vertical dimension 

and utilize the rise and fall of the wave height at a single point for WEC. 
 6 

 

FIGURE 3 Pelamis Wave Energy Converter (Source: Ocean Power Delivery Ltd. 2006) 

One such device is the PowerBuoyTM developed by 

Ocean Power Technologies (2006) (Figure 4). The 

construction involves a floating structure with one 

component relatively immobile, and a second component 

with movement driven by wave motion (a floating buoy 

inside a fixed cylinder). The relative motion is used to drive 

electromechanical or hydraulic energy converters. A 

PowerBuoy demonstration unit rated at 40 kW was installed 

in 2005 for testing offshore from Atlantic City, New Jersey. 

Testing in the Pacific Ocean is also being conducted, with a 

unit installed in 2004 and 2005 off the coast of the Marine 

Corps Base in Oahu, Hawaii. A commercial-scale 

PowerBuoy system is planned for the northern coast of 

Spain, with an initial wave park (multiple units) at a 

1.25-MW rating. Initial operation is expected in 2007. 

The AquaBuOYTM WEC (Figure 5) being developed by the AquaEnergy Group, Ltd. 

(2005) is a point absorber that is the third generation of two Swedish designs that utilize the 

wave energy to pressurize a fluid that is then used to drive a turbine generator. The vertical 

movement of the buoy drives a broad, neutrally buoyant disk acting as a water piston contained 

in a long tube beneath the buoy. The water piston motion in turn elongates and relaxes a hose 

containing seawater, and the change in hose volume acts as a pump to pressurize the seawater. 

The AquaBuOY design has been tested using a full-scale prototype, and a 1-MW pilot offshore 

demonstration power plant is being developed offshore at Makah Bay, Washington. The Makah 

Bay demonstration will include four units rated at 250 kW placed 5.9 km (3.2 nautical miles) 

offshore in water approximately 46 m deep. 

FIGURE 4 PowerBuoy Point 

Absorber Wave Energy 

Converter (Source: Ocean 

Power Technologies 2006)
 7 

 

FIGURE 5 AquaBuOY Point Absorber Wave Energy Converter 

(Source: AquaEnergy Group, Ltd. 2005) 

Other point absorbers that have been tested at 

prototype scale include the Archimedes Wave Swing (2006), 

which consists of an air-filled cylinder that moves up and 

down as waves pass over. This motion relative to a second 

cylinder fixed to the ocean floor is used to drive a linear 

electrical generator. A 2-MW capacity device has been tested 

offshore of Portugal. 

Overtopping Devices 

Overtopping devices have reservoirs that are filled by 

impinging waves to levels above the average surrounding 

ocean. The released reservoir water is used to drive hydro turbines or other conversion devices. 

Overtopping devices have been designed and tested for both onshore and floating offshore 

applications. The offshore devices include the Wave DragonTM (Wave Dragon 2005), whose 

design includes wave reflectors that concentrate the waves toward it and thus raises the effective 

wave height. Wave Dragon development includes a 7-MW demonstration project off the coast of 

Wales and a precommercial prototype project performing long-term and real sea tests on 

hydraulic behavior, turbine strategy, and power production to the grid in Denmark. The Wave 

Dragon design has been scaled to 11 MW (Christensen 2006), but larger systems are feasible 

since the overtopping devices do not need to be in resonance with the waves as is the case for 

point absorbing devices. 

The WavePlaneTM (WavePlane Production 2006) overtopping device has a smaller 

reservoir. The waves are fed directly into a chamber that funnels the water to a turbine or other 

conversion device. 

FIGURE 6 Wave Dragon 

Overtopping Device (Source: 

Wave Dragon 2005) 
 8 

ENVIRONMENTAL CONSIDERATIONS 

Conversion of wave energy to electrical or other usable forms of energy is generally 

anticipated to have limited environmental impacts. However, as with any emerging technology, 

the nature and extent of environmental considerations remain uncertain. The impacts that would 

potentially occur are also very site specific, depending on physical and ecological factors that 

vary considerably for potential ocean sites. As large-scale prototypes and commercial facilities 

are developed, these factors can be expected to be more precisely defined. 

The following environmental considerations require monitoring. 

Visual appearance and noise are device-specific, with considerable variability in visible 

freeboard height and noise generation above and below the water surface. Devices with OWCs 

and overtopping devices typically have the highest freeboard and are most visible. Offshore 

devices would require navigation hazard warning devices such as lights, sound signals, radar 

reflectors, and contrasting day marker painting. However, Coast Guard requirements only require 

that day markers be visible for 1 nautical mile (1.8 km), and thus offshore device markings 

would only be seen from shore on exceptionally clear days. The air being drawn in and expelled 

in OWC devices is likely to be the largest source of above-water noise. Some underwater noise 

would occur from devices with turbines, hydraulic pumps, and other moving parts. The 

frequency of the noise may also be a consideration in evaluating noise impacts. 

Reduction in wave height from wave energy converters could be a consideration in some 

settings; however, the impact on wave characteristics would generally only be observed 1 to 

2 km away from the WEC device in the direction of the wave travel. Thus there should not be a 

significant onshore impact if the devices were much more than this distance from the shore. 

None of the devices currently being developed would harvest a large portion of the wave energy, 

which would leave a relatively calm surface behind the devices. It is estimated that with current 

projections, a large wave energy facility with a maximum density of devices would cause the 

reduction in waves to be on the order of 10 to 15%, and this impact would rapidly dissipate 

within a few kilometers, but leave a slight lessening of waves in the overall vicinity. Little 

information is available on the impact on sediment transport or on biological communities from a 

reduction in wave height offshore. An isolated impact, such as reduced wave height for 

recreational surfers, could possibly result. 

Marine habitat could be impacted positively or negatively depending on the nature of 

additional submerged surfaces, above-water platforms, and changes in the seafloor. Artificial 

above-water surfaces could provide habitat for seals and sea lions or nesting areas for birds. 

Underwater surfaces of WEC devices would provide substrates for various biological systems, 

which could be a positive or negative complement to existing natural habitats. With some WEC 

devices, it may be necessary to control the growth of marine organisms on some surfaces. 

Toxic releases may be of concern related to leaks or accidental spills of liquids used in 

systems with working hydraulic fluids. Any impacts could be minimized through the selection of 

nontoxic fluids and careful monitoring, with adequate spill response plans and secondary 
 9 

containment design features. Use of biocides to control growth of marine organisms may also be 

a source of toxic releases. 

Conflict with other sea space users, such as commercial shipping and fishing and 

recreational boating, can occur without the careful selection of sites for WEC devices. The 

impact can potentially be positive for recreational and commercial fisheries if the devices 

provide for additional biological habitats. 

Installation and decommissioning. Disturbances from securing the devices to the ocean 

floor and installation of cables may have negative impacts on marine habitats. Potential 

decommissioning impacts are primarily related to disturbing marine habitats that have adapted to 

the presence of the wave energy structures. 

A detailed site-specific environmental assessment has been conducted for a project to 

install and test multiple WEC devices at the Marine Corps Base Hawaii, Kaneohe Bay 

(Department of the Navy 2003). A summary of this assessment is provided for illustrative 

reasons. The project involves installation and testing of up to six WEC devices of the point 

absorbers design. The WEC buoys are to be located in about 30 m of water approximately 

1,200 m offshore, at two possible sites in Hawaii. The electrical power generated would be 

transmitted to shore via an underwater cable. Submerged equipment would be weighted and 

secured to the seafloor with rock bolts. The 10 potentially affected resources that were identified 

for this project are shoreline physiography, oceanographic conditions, marine biological 

resources, terrestrial biological resources, land and marine resource use compatibility, cultural 

resources, infrastructure, recreation, public safety, and visual resources. None of these resources 

were found to be significantly impacted by the proposed installation and operational testing. 

Installation procedures would be designed to minimize impacts on living coral and benthic 

communities by avoiding areas of rich biological diversity and high coral coverage. Growth of 

benthic organisms, such as corals and sponges, on the new substrate provided by the undersea 

components of the system may end up benefiting the ecosystem. Organisms sensitive to electric 

or magnetic fields may be able to detect stray currents or corona effects when very close to the 

undersea cable; however, the effects would be minor and temporary. It was determined that there 

would be no significant impacts on recreation and public safety, although recreational activities 

in the immediate vicinity of the buoy array would be somewhat curtailed for safety reasons. 

Access to the area around the buoy area would not be restricted. Signage would be installed 

advising of the dangers associated with the equipment. Operation of the system is expected to 

produce a continuous acoustical output similar to low-grade noise associated with light to normal 

ship traffic. At the proposed distance from shore, visual impacts by the buoy mast assembly 

above the waterline would not be significant. 

ECONOMIC CONSIDERATIONS 

Cost estimates of energy produced by WECs are dependent on many physical factors, 

such as system design, wave energy power, water depth, distance from shore, and ocean floor 

characteristics. Economic factors, such as assumptions on discount rate, cost reductions from a 

maturing technology, and tax incentives, are also critical. A detailed evaluation of potential wave 
 10 

energy development in the U.S. coastal areas has been conducted, taking into account variability 

in these factors (Bedard et al. 2005). The resulting cost estimate of electricity from the first 

commercial-scale facilities in the California, Hawaii, Oregon, and Massachusetts offshore 

regions with relatively high wave energy was in the range of $0.09 to $0.11/kWh, after tax 

incentives. 

These facilities are very capital intensive, and these costs currently have a high degree of 

uncertainty. For example, capital investment cost estimates for the applications noted above 

range from $4,000 to $15,000/kW, suggesting that significant breakthroughs in capital cost 

would be needed to make this technology cost competitive. 

SUMMARY 

The offshore ocean wave energy resource, as a derivative form of solar energy, has 

considerable potential for making a significant contribution to the alternative usable energy 

supply. The total average wave energy at a depth of 60 m off the U.S. coastlines, including 

Alaska and Hawaii, has been estimated at 2,100 TWh/yr. In the past several decades, various 

designs have been developed and tested to capture this energy resource, and several are now 

moving toward commercial prototype testing. On the basis of currently available empirical 

information, the environmental impacts are expected to be small; however, as with any emerging 

technology, unknowns still exist with respect to environmental impacts, and careful monitoring 

and assessment are required. 

REFERENCES 

AquaEnergy Group, Ltd., 2006, “AquaBuOY Wave Energy Converter.” Available at 

www.aquaenergygroup.com. 

Archimedes Wave Swing, 2006, “Archimedes Wave Swing Website.” Available at 

www.waveswing.com. 

Bedard, R., et al., 2005, Final Summary Report, Project Definition Study, Offshore Wave Power 

Feasibility Demonstration Project, EPRI Global WP 009 − US Rev 1, Jan. 14, 2005. 

Christensen, L., 2006, e-mail from Christensen (Wave Dragon ApS, Copenhagen, Denmark) to 

L. Habegger (Argonne National Laboratory, Argonne, Ill.), June 22. 

Department of the Navy, 2003, Environmental Assessment, Proposed Wave Energy Technology 

Project, Marine Corps Base Hawaii, Kaneohe Bay, Hawaii, Jan. 

Energetech 2006, “Media Release: Port Kembla Trial Deployment Results,” Nov. 2005. 

Available at www.energetech.com.au. 
 11 

European Thematic Network on Wave Energy (ETNWE), 2003, Results from the Work of the 

European Thematic Network on Wave Energy, ERK5-CT-1999-20001, 2000−2003. Available at 

www.wave-energy.net. 

Japan Marine Science and Technology Center (JAMSTEC), 2006, “Wave Energy Research and 

Development at JAMSTEC, Offshore Floating Wave Energy Device, Mighty Whale.” 

Available at www.jamstec.go.jp/jamstec/MTD/Whale/index.html. 

Ocean Power Delivery Ltd., 2006, “World’s First Wave Farm⎯Shipping of First Machine to 

Portugal,” Press Release, March 14. Available at www.oceanpd.com. 

Ocean Power Technologies, 2006, “Making Waves in Power.” Available at www.oceanpower

technologies.com. 

Polaski, K., 2003, “Waiting for the Waves,” The IEA Ocean Energy Systems Newsletter, Issue 2, 

Sept. Available at http://www.iea-oceans.org/newsletters/news2.pdf. 

Rhinefrank, K., 2005, “Wave Energy Research, Development, and Demonstration at Oregon 

State University,” presented at Energy Ocean 2005, April 26−28, Washington, D.C. 

Thorpe, T.W., A Brief Review of Wave Energy, 1999, ETSU Report R-122, prepared for the 

United Kingdom Department of Trade and Industry. 

Wave Dragon, 2005, “Technology.” Available at http://www.wavedragon.net. 

WavePlane Production A/S = WPP A/S, 2006, Home page. Available at www.waveplane.com.