Technology White Paper 

on 

Wind 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 
WIND 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 wind resources on the OCS. Resource 

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

environmental and economic considerations that can be surmised from literature and 

environmental studies that are available 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 

 

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. 

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waves, solar radiation, and ocean currents, and the transportation of energy generated on the 

OCS to onshore as electricity or in the form of hydrogen. 

RESOURCE POTENTIAL 

The U.S. Department of Energy (DOE) estimates that more than 900,000 MW2 (close to 

the total current installed U.S. electrical capacity) of potential wind energy exists off the coasts 

of the United States, often near major population centers, where energy costs are high and landbased wind development opportunities are limited. Slightly more than half of the country’s 

identified offshore wind potential is located off the New England and Mid-Atlantic Coasts, 

where water depths generally deepen gradually with distance from the shore. Resources on the 

Gulf Coast and Great Lakes Regions3 have not been fully characterized (Offshore Wind 

Collaborative Organizing Group 2005). Table 1 shows estimated OCS wind energy resources by 

region for waters less than 30 m deep and waters equal to or greater than 30 m deep in the 

United States. Development of offshore wind energy technologies has the potential to provide up 

to 70,000 MW of domestic generating capacity to the nation’s electric grid by 2025 

(Thresher 2005). 

Of the more than 900,000 MW of offshore wind resources beyond 5 nautical miles from 

shore, slightly more than 10% (98,000 MW) is estimated to be over waters less than 30 m deep. 

In the near term, existing offshore technologies, which have been used in Europe’s shallow 

waters for more than a decade, may be applicable for these shallow U.S. waters. However, 

because the remaining OCS resources are over waters that are 30 m or deeper, new technologies 

(e.g., for towers, foundations, and blades) will be needed to harness the wind in the harsher 

conditions associated with deeper waters. Harsher conditions generally include higher wind 

velocities and greater wave action. 

Today, more than 600 MW of offshore wind energy capacity is installed worldwide 

(all in waters less than 30 m deep). Proposed offshore wind facilities through 2010 amount to 

more than 11,000 MW, with about 500 MW each in the United States and Canada, and the 

remainder in Europe and Asia (Musial 2005). 

 

2 This estimate excludes the offshore zone from the shoreline to 5 nautical miles. It also excludes 67% of the 

potential area within 5 to 20 nautical miles from shore, to account for shipping lanes and avian, marine mammal, 

fish, and view shed concerns. For the 20- to 50-nautical-mile zone, the exclusion was reduced to 33% where 

there are fewer environmental concerns and where wind facilities would not be visible from the shore (Musial 

and Butterfield 2004). 

3 The Great Lakes are outside the scope of this White Paper. 

 2 
TABLE 1 Offshore Resource Estimates (MW) 

5 to 20 Nautical Miles 20 to 50 Nautical Miles 

Region 

< 30 m 

deep 

=> 30 m 

deep 

% 

Exclusion < 30 m => 30 m 

% 

Exclusion 

New England 9,900 41,600 67 2,700 166,300 33 

Mid-Atlantic States 46,500 8,500 67 35,500 170,000 33 

California 2,650 57,250 67 0 238,300 33 

Pacific Northwest 725 34,075 67 0 93,700 33 

 Total 59,775 141,425 67 38,200 668,300 33 

Source: Musial and Butterfield (2004). 

RESOURCE UTILIZATION TECHNOLOGIES 

Wind turbines will be used to harness the kinetic energy of the moving air over the 

oceans on the OCS and convert it to electricity. Offshore winds are less turbulent (because the 

ocean is flat relative to onshore topography), and they tend to flow at higher speeds than onshore 

winds, thus allowing turbines to produce more electricity. Because the potential energy produced 

from the wind is directly proportional to the cube of the wind speed, increased wind speeds of 

only a few miles per hour can produce a significantly larger amount of electricity. For instance, a 

turbine at a site with an average wind speed of 16 mph would produce 50% more electricity than 

at a site with the same turbine and average wind speeds of 14 mph (Offshore Wind 2006). 

Historical Perspective

As early as 200 B.C., wind was reportedly used to pump water in China and grind grain 

in the Middle East. Over the centuries, onshore wind has been harnessed to generate power 

worldwide. In the nineteenth century, settlers in the United States used windmills to generate 

electricity for homes and pump water for consumption and crop irrigation; industrialization 

sparked the development of larger windmills to generate electricity for commercial purposes. 

Interest in wind energy has waxed and waned with the price of fossil fuels. After the 1973 Arab 

oil embargo, new ways of converting wind energy into useful power were developed. Many of 

these approaches have been demonstrated in wind facilities (also known as wind farms, wind 

power plants, or wind projects), which are groups of turbines that feed electricity into the utility 

grid. Wind facilities began appearing in California in the 1980s, and, today, the cost of onshore 

wind-generated electricity is close to that generated from conventional utilities in some locations. 

Wind energy is the fastest growing energy source worldwide at about 20 to 30% per year. 

The worldwide installed capacity of onshore grid-connected wind power is about 40 GW. 

Turbine sizes have increased over the past two decades. In the mid-1980s, the rotor (blades and 

hub) diameter was about 20 m; today, rotor diameters are 100 m or more (bigger than the 

wingspan of a 747 aircraft), with the rotating blades covering an area the size of a football field. 

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The first offshore wind facilities were installed in the early 1990s in Europe where there was 

limited land available for onshore wind energy production. The Vindeby Facility in Denmark 

(Figure 1), completed in 1991, has eleven 450-kW turbines that provide a total capacity of 

4.95 MW. Since then, the trend has been to move wind turbines offshore to take advantage of 

higher wind speeds; smoother, less turbulent airflows; larger amounts of open space; and the 

ability to build larger, more cost-effective turbines. Today, more than a dozen offshore European 

wind facilities with turbine ratings of 450 kW to 3.6 MW exist offshore in very shallow 

(depths of 5 to 12 m) waters. Because of these shallow depths, the offshore turbines installed to 

date have been able to use conventional land-based designs with upgraded electrical and 

corrosion control systems, and foundations (concrete bases or steel monopiles) to anchor them to 

the seabed. 

Basic Offshore Wind Technology 

A wind turbine can be compared to a fan operating in reverse: rather than using 

electricity to produce wind, the turbine uses the wind to make electricity. In a wind turbine, the 

blades capture a small portion of the kinetic energy of incident wind through a process of 

aerodynamic lift, and the blades spin a shaft that is connected through a set of gears to the center 

shaft of an electrical generator. As with land-based wind facilities, offshore facilities are likely to 

consist of a number of turbines operating independently, but delivering their power to onshore 

customers through a common conduit, typically an undersea cable. The positions of the turbines 

are selected to ensure that each turbine operates in the wind regime for which it was designed 

and to prevent the air turbulence that is created by the towers and rotating blades of one turbine 

from interfering with the efficient operation of nearby turbines. Such careful “micrositing” of 

turbines within a wind facility helps ensure that the facility, as a whole, operates with the highest 

possible efficiencies, regardless of wind direction. In some land-based settings, this requires 

turbines to be separated by as much as 10 rotor diameters from each other. In offshore 

applications, where only two wind directions are likely to predominate, the distances between 

turbines arranged in a line can be shortened to as little as two to four rotor diameters without 

FIGURE 1 World’s First Offshore Wind Facility, Vindeby, 

Denmark, 1991 (Source: Siemens 2006) 

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creating interferences because of turbulence. Principal components of an OCS wind turbine 

include the following: 

• Rotor (blades and blade hub), which is connected through a drive train to the 

generator; 

• Turbine assembly, which includes the gearbox and generator, and is enclosed 

by a shell or nacelle; 

• Tower, which supports the turbine assembly, houses the remaining facility 

components, and provides sheltered access for personnel; and 

• Foundation or structure to support the tower. 

Offshore turbines have technical needs not required of onshore turbines because of their 

exposure to the more demanding climates that exist in offshore locations. Offshore turbines look 

similar to those onshore, with several design modifications. These include strengthening the 

tower to cope with wind-wave interactions, protecting the nacelle components from the corrosive 

nature of sea air, and adding brightly colored access platforms for navigation and maintenance. 

Offshore turbines are typically equipped with corrosion protection, internal climate control, highgrade exterior paint, and built-in service cranes. To minimize expensive servicing, offshore 

turbines may have automatic greasing systems to lubricate bearings and blades, and preheating 

and cooling systems to maintain gear oil temperature within a narrow temperature range. 

Lightning protection systems minimize the risk of damage from lightning strikes that occur 

frequently in some locations offshore. There are also navigation and aerial warning lights. 

Turbines and towers are typically painted light blue or grey to help them blend into the sky. The 

lower section of the support towers may be painted bright colors (e.g., yellow) to aid in 

navigation and to highlight the structures for passing vessels. 

Offshore wind turbines are also bigger than onshore turbines (to take advantage of the 

steadier and higher velocity offshore winds and economies of scale). A typical onshore turbine 

installed today has a tower height of about 60 to 80 m, and blades about 30 to 40 m long; most 

offshore wind turbines are at the top end of this range. Offshore turbines installed today have 

power generating capacities of between 2 and 4 MW (Figure 2), with tower heights greater than 

61 m and rotor diameters of 76 to 107 m. Turbines of up to 5 MW are being tested. 

Figure 3 shows the primary components and dimensions of one of the eighty 2-MW 

turbines in Denmark’s Horns Rev offshore wind park (the largest capacity offshore wind facility 

constructed to date). 

Figure 4 shows how a European offshore wind park converts wind to electricity and 

sends it to the onshore grid (BWEA 2006a). After a suitable place for the wind facility is located, 

piles (1) are driven into the seabed. Once the turbine is assembled, sensors on the turbine detect 

the wind direction and turn the nacelle to face into the wind, so that the blades can collect the 

 5 
FIGURE 2 Rotor Assembly for Scroby Sands, 

United Kingdom Offshore Wind Facility 

(2-MW turbine) (Source: BWEA 2006c) 

maximum amount of energy throughout each diurnal cycle.4 The moving wind over the 

aerodynamically shaped blades (2) makes them rotate around a horizontal hub, which is 

connected to a shaft inside the nacelle (3). This shaft, via a gearbox, powers a generator to 

convert the energy into electricity. Undersea collection cables (4) take the power from the 

individual turbines to an offshore transformer (5) that converts the electricity to a high voltage 

(33 kV) before running it back via an undersea transmission cable 8 to 16 km to connect to the 

grid at a substation on land (6). At the substation, the outputs of multiple collection cables are 

combined, brought into phase, and stepped up in voltage for transmission to the onshore grid. 

OCS Wind Development in the United States 

Because of the relatively vast onshore wind resources that exist in the United States 

(as opposed to Europe), there has been relatively little U.S. OCS wind development, and there 

are no commercial wind facilities operating today off the coasts of the United States. In the past 

few years, interest in offshore wind energy has increased because of a number of factors: 

offshore wind turbines can generate power closer to high-value coastal load centers than onshore 

turbines, offshore winds produce more power per unit area, and offshore European wind 

facilities have demonstrated the feasibility of offshore facilities. 

 

4 Diurnal wind cycles result from the differential cooling and heating rates between land and water, thereby 

generating wind even if there are no storm fronts in the area. 

 6 
FIGURE 3 Primary Components and Dimensions of One of the 2-MW 

Turbines in Denmark’s Horns Rev Offshore Wind Park (Source: Adapted 

from Offshore Wind Collaborative Organizing Group 2005) 

Today, at least three offshore wind facilities are in the planning stages in the 

United States: 

• Cape Wind facility off the coast of Massachusetts. Developers filed for a 

permit from the U.S. Army Corps of Engineers in 2001 to build this 

130-turbine facility slated to produce up to 420 MW. It is on the OCS 

(just beyond 5 km offshore), and it would be the largest offshore wind energy 

facility in the world. 

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FIGURE 4 Schematic of Offshore Wind Facility (Source: BWEA 2006a) 

• Long Island Offshore Wind Park. Off the southern coast of Long Island, 

New York, and also on the OCS, this facility is planned to consist of 

40 turbines producing 140 MW of power. A permit application for this facility 

was submitted to the Corps in April 2005 (FPL 2006). 

• Fifty-turbine facility off the Galveston, Texas coast. While this facility is not 

in the Northeast, where offshore winds are considered to be the strongest and 

other energy alternatives are lacking, its developers believe it will be 

successful because of the area’s experience with other offshore energy 

development and a more favorable state regulatory environment 

(Miller 2006). (State of Texas regulatory authority extends to 16 km off the 

coast, whereas other states’ authorities extend for 5 km.) 

Important differences exist between Europe and the United States regarding offshore 

wind environments. U.S. waters are generally deeper than those off the European coasts, and 

ocean conditions on the U.S. OCS are more severe than those in Europe. Thus, the technologies 

designed for European offshore environments will need to be modified to adapt to the harsher 

U.S. OCS conditions. 

U.S. Technology Needs 

As wind speeds tend to increase with distance from the shore, turbines built farther 

offshore will be able to capture more wind energy. However, as the distance from land increases, 

the costs of building and maintaining the turbines and transmitting the power back to shore also 

increase sharply. To capture the wind power and reach the economies of scale needed to make 

the far offshore sites financially viable, it is generally believed that 5-MW or larger turbines will 

be needed. Technologies will be needed for low-cost mooring and anchor development, for 

erecting and decommissioning in relatively deeper waters (greater than 30 m), and for improving 

accessibility and reliability. Ways to store wind energy for later use may also be required. 

Technologies also will be needed to develop large composite blades, to reduce the weight of the 

blades, and to improve their ability to withstand variations in turbulence. Reducing blade weights 

 8 
also reduces the structural demands placed on the towers. DOE recently announced plans to 

develop a multimegawatt offshore wind power system over the next several years that would 

include innovative construction techniques, rotor designs, drive trains, electrical components, 

and foundations designed for the harsh offshore environment, while optimizing the total lifecycle cost (DOE 2006). 

The extreme requirements placed on tower foundations are important constraints on OCS 

wind development. Many turbines have been installed on steel monopiles—long, steel tubes that 

are hammered, drilled, or vibrated into the seabed until secure. Others have been attached to 

gravity foundations—concrete structures that settle and are stabilized by sand or water. These 

types of foundations are less suitable for the deeper waters off U.S. coasts. Platforms capable of 

supporting the turbines in deep water (up to 900 m) will allow access to offshore areas where an 

estimated 750,000 MW of wind resource potential exists (Thresher 2005). 

It is possible that floating structures developed for offshore oil and gas industries can be 

adapted for wind turbines. A floating structure for a wind turbine must provide sufficient 

buoyancy to support the weight of the turbine and to restrain pitch, roll, and heave motions 

caused by wind and wave forces, under normal and storm conditions. At the same time, the 

offshore floating platforms used by the oil and gas industry have certain requirements that may 

not be needed by wind turbine platforms. For example, oil and gas platforms often provide 

permanent residences for offshore personnel and must have additional safety margins and 

stability for spill prevention that would not be required for wind turbines. Finally, oil and gas 

platforms are deployed in water depths up to 2,438 m; wind turbines would probably not need to 

be sited in waters deeper than 183 m. Figure 5 shows several platform concepts for the relatively 

deep waters. 

FIGURE 5 Offshore Platform Concepts (Source: Musial 2005) 

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Integration with Other OCS Energy Technologies 

There have been proposals to combine tidal and wind power and install tidal stream 

turbines on the bases of offshore wind turbines. The hybridization of wind and wave energy 

could enhance cost competitiveness with onshore wind facilities because of synergies that 

include single permitting; shared foundation/mooring infrastructure; shared deployment and 

operation maintenance with common facilities, equipment, and personnel; and higher capacity. 

However, marine-based renewable energy technologies are all at relatively earlier stages of 

development than offshore wind, so such amalgamated facilities are not imminent. 

Integration with Onshore Energy Technologies/Systems 

Wind resources vary by the minute, hour, day, month, and year, and these variations can 

affect the onshore electric power generation, transmission, and distribution systems with which 

they interface. Since the electricity coming into the power system is variable, there may be times 

when it could potentially overload the system, and there may be times when its anticipated 

contribution falls short. However, grids are designed to compensate for loss-of-load 

contingencies when large power plant units suddenly become unavailable. Utility studies have 

indicated that wind can readily be absorbed in an integrated network until the wind capacity 

accounts for about 20% of maximum demand. Beyond this, some changes to operational practice 

may be needed. Integrating variable output is easier when it is part of large power systems that 

can take advantage of the natural diversity of variable sources. A large geographical spread of 

wind power will reduce variability, increase predictability, and decrease the number of instance 

with near zero or peak output. 

Grid connection of offshore wind facilities is not a major technical problem per se, 

because the relevant technologies are well known. But integrating large wind facilities with the 

grid could present challenges. With smaller facilities, wind turbines could go off the system 

when the grid became unstable. Once the grid stabilized, they would resynchronize and come 

back online. With large wind facilities comprising a significant part of the generation capacity in 

some areas, the objective now is to make the wind facilities act more like thermal units from a 

power distribution level (Gadomski 2005). Large OCS facilities, could in principle, provide the 

same ancillary services that conventional generators offer today to help ensure system stability. 

Wind turbine manufacturers are investing in technologies to smooth sudden bursts and even out 

short-term fluctuations in wind-generated power. 

Wind-generated electricity must be conditioned and phased properly before it is 

introduced into the grid. That is, its voltage, frequency, and other electrical parameters must be 

made compatible with the conditions existing on the grid. Procedures for such interconnections 

need to be considered and established to accommodate power generated in offshore wind 

facilities. 

The feasibility of using electricity generated by offshore wind turbines to produce 

hydrogen as an alternative to connecting that electrical power to an existing onshore power grid 

is also being investigated. Hydrogen would be produced through the electrolysis of desalinated 

 10 
seawater by using electricity produced by the wind. It could then be transported to shore as pure 

hydrogen in its molecular form (H2) either as compressed gas or as liquid via pipeline, tanker, or 

a ship, or via a hydrogen carrier that would use materials to transport hydrogen in a form other 

than free H2 molecules. (See the White Paper on the transportation of energy generated on the 

U.S. OCS to onshore for more details.) Some of the electricity produced by the turbine also 

could be used to provide the power needed to run reverse osmosis or distillation systems. 

ENVIRONMENTAL CONSIDERATIONS 

Potential environmental impacts associated with the development and utilization of wind 

energy resources on the U.S. OCS will be fully investigated in the Programmatic EIS. Impacts on 

major environmental resources, including human health and safety, air and water quality, 

ecology, socioeconomics, waste management, resource requirements, and cultural resources, will 

be analyzed individually and cumulatively with other facilities potentially affecting each 

environmental resource. The following paragraphs highlight potential environmental 

considerations for each phase of OCS wind energy development. 

Construction 

Construction time for offshore facilities to date has been about 6 months, but this would 

be longer for the larger facilities that would be built on the U.S. OCS. (Construction time for the 

Cape Wind facility is estimated to be about 2 years.) During construction, key concerns are 

sedimentation, noise, and vibration. Construction practices such as soft-start pile driving, bubble 

curtains, and other proven best practice methodologies can help mitigate noise and vibration. 

During construction, there is a risk that oil or other harmful substances could be spilled and thus 

deteriorate water quality. 

Operations 

OCS wind turbines are expected to have an operational life of 20 to 25 years. However, it 

may be possible to install new turbines on existing foundations so that a given wind facility may 

remain operational beyond the life expectancy of its component turbines. Potential impacts on 

the environment that may occur during operations are highlighted below. 

• Marine life. Foundations can act as artificial reefs with a resultant increase in 

fish populations from the new food supply. These increases in fish population 

may also have stimulating effects on bird populations in the area, which could 

promote collisions between birds and towers or rotors. 

• Migrating birds. In addition to potential collisions (bird strikes), it is possible 

that the birds would need to consume more energy to avoid collisions and 

maintain their orientation when navigating around the turbines. Tower 

illumination may also cause navigational disorientation for birds. 

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• Interference with navigation for endangered and threatened species. 

Electromagnetic fields created by the electric cables running from the turbines 

and underwater noises and vibrations could affect orientation and navigational 

ability. 

• Potential alteration of natural environments and diminution of habitats. 

Underwater support pilings, anchoring devices, scour-protection materials, 

and electromagnetic fields could cause a decrease in benthic communities, 

alter natural environments, and possibly affect migration patterns. 

• Emissions. Each unit of electricity generated from the wind that substitutes for 

a unit generated from fossil fuels helps reduce greenhouses gases, pollutants, 

and waste products that result from fossil fuel use. 

• Conflict with Other Sea Space Uses. Wind turbines on the OCS may interfere 

with commercial shipping and fishing and recreational boating. It is possible 

that wind turbine energy facilities may disrupt air traffic control and maritime 

radar systems. 

• Visual impacts for systems that are close to the shore.5 (At greater distances, 

visibility impacts are reduced.) 

• Noise. Newer wind turbine generators produce less sound than older turbines, 

but impacts of low frequency sound near the turbines on mammals would 

need to be investigated. 

Decommissioning 

After an OCS turbine has reached its useful life, it would be dismantled and 

decommissioned—a process expected to take about 6 months. Removal of turbine components 

including blades, nacelle, tower, and containerized transformer, is anticipated to be largely a 

reversal of the installation process and would be subject to the same constraints. Ultimate 

decommissioning of a facility may range from complete removal of all components ⎯ including 

cabling, foundations, and scour protection ⎯ to dismantling and using the decommissioned 

equipment for artificial reefs. Environmental impacts would vary depending on approach. They 

would likely be similar in nature to those found in other phases of development and use, 

although they may be more significant in terms of degree. 

A number of measures can be employed to mitigate potential effects. Environmental 

impacts associated with OCS wind development should be evaluated in conjunction with the 

impacts of other energy technologies over the entire life cycle of operations. 

 

5 The OCS generally begins 5 km from the shoreline. Thus, projects that are less than 5 km from the shoreline 

would not be OCS facilities but would be within state jurisdiction. 

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Siting Constraints 

In selecting OCS wind facility locations, developers will need to consider how candidate 

areas are already used to avoid potential conflicts. In addition to minimizing the types of 

potential environmental impacts identified above, potential siting issues that need to be 

considered include the following: 

• Shipping lanes, 

• Excavation of raw materials in OCS areas, 

• Existing areas used for disposal of dredged materials and other wastes, 

• Pipelines, 

• Commercial and recreational fishing areas, 

• Low-flying aircraft flight patterns, 

• Military operations and radar systems, and 

• Migration patterns for birds and mammals. 

ECONOMIC CONSIDERATIONS 

The economic viability of an offshore wind facility depends on whether the costs can be 

offset by high-quality wind resources and high productivity. In the last 20 years, the costs of 

creating energy from wind have dropped significantly. According to DOE, advanced turbines 

have reduced the price from $0.40/kWh to $0.04 to $0.06/kWh today for onshore wind. This 

compares with natural gas at $0.04 to $0.05kWh, but it is still more expensive than hydro 

($0.03 to $0.04/kWh) and coal ($0.02 to $0.03kWh) (Pellerin 2005). Offshore wind facility costs 

today are generally between $0.08 and $0.15/kWh ⎯ almost double that of onshore facilities 

(Offshore Wind Collaborative Organizing Group 2005). These costs are for wind facilities 

located in the shallow (less than 30 m deep) areas of the coasts of Europe, where development 

costs are less than would be expected in the deeper, harsher U.S. OCS waters. To date, most 

offshore wind facilities have been developed with some kind of government support.6

Nonetheless, by 2012 and beyond, DOE envisions 5-MW and larger machines generating power 

for $0.05/kWh (DOE 2006). 

 

6 For example, the United Kingdom’s offshore projects are being developed in two rounds. The first round, 

consisting of 13 offshore wind facilities, was announced in 2001; all of these received government grants. Of 

these, three are in operation, one is under construction, and two have been put on hold indefinitely because the 

developer no longer believes they are economically viable. The remaining seven are experiencing delays. The 

second round was to have benefited from experience and economies of scale so that government support would 

not be necessary. However, developers say that costs have actually risen by one-third, and that it is doubtful that 

the second round of projects can proceed without government support (Webb 2006). 

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The costs of OCS wind energy development are higher than those for onshore wind for 

several reasons, including the need for more expensive foundations, protection against salt spray 

and corrosion, and transporting and installing at sea. Power collection and transmission costs 

may also be higher for OCS applications. Overall, capital investment requirements may be 

30 to 60% higher for OCS applications than for onshore facilities (DWIA 2006). Operation and 

maintenance (O&M) costs are higher because of site remoteness and potentially unfavorable 

weather conditions. Annual O&M costs for offshore wind facilities are estimated to be roughly 

1.5 to 2.0% of the initial capital investment. These increases are partially offset by energy yields 

that are up to 30% higher than onshore yields (BWEA 2006b), economies of scale,7 and close 

proximity to high-value load centers. Also, prices are expected to drop as technology improves 

and more experience is gained. For example, the capital costs for onshore wind development 

have decreased an average of 15% for every doubling of capacity (Offshore Wind Collaborative 

Organizing Group 2005). 

At the just-completed 2006 annual offshore conference of the British Wind Energy 

Association (BWEA), however, information was presented indicating that the costs of building 

offshore facilities have increased by 33% and are nearly double the costs of building onshore 

facilities. The increasing costs of steel and the demand from Asia and the United States for wind 

facilities have pushed up the price of turbines and limited the availability of the equipment 

needed to install them (Webb 2006). 

Construction and accessibility are the leading cost drivers for wind facilities, and these 

costs are much higher at sea. The majority of costs in offshore facilities are in the facility 

components, including the foundation/support structure, installation, and transmission, whereas 

for onshore facilities, most of the costs are in the turbines. Depth of water is an important 

contributor, with each additional meter of tower height adding an estimated $2,000 to the capital 

cost (DWIA 2006). Although there is no long-term experience with OCS facilities, current 

estimates are that rebuilding some of the major components after about 25 years of operation 

could be necessary for efficient operation. Current estimates indicate that such costs would be on 

the order of 25% of the initial capital investment (DWIA 2006). 

SUMMARY 

OCS wind energy has the potential to provide 900,000 MW, which is close to the total 

currently installed U.S. electrical capacity. Much of this potential is near high-energy demand 

areas with limited energy resources. OCS wind turbines and technologies are based on onshore 

wind technologies, but they are generally larger and more expensive (because of marine 

conditions). The largest OCS wind turbines in commercial operation today are 3.6 MW, and 

development is underway for 5 MW-offshore turbines that are expected to generate electricity 

for costs of about $0.05/kWh. To use the greater wind resource potentials that exist in the far 

offshore areas, technological advances will be needed to reduce the weight of turbines and to 

develop safe and cost-effective platforms to harness the wind that is available over deeper 

 

7 The physical constraints of transporting large components such as blades do not apply to the same degree 

offshore, and the cost of installation offshore is much the same regardless of the size of turbines. 

 14 
waters. Potential advantages of OCS wind energy are that the fuel has no cost, harnessing the 

energy produces no emissions, the power is produced domestically, and a significant amount of 

renewable energy that is relatively close to high-energy demand centers is harnessed. 

Potential impediments for near-term utilization include the need for new technologies to 

capture the resource in larger amounts and higher costs relative to onshore technologies. 

Environmental considerations will need to be addressed. For offshore applications to be 

commercially competitive there is a need to overcome current depth limits, improve accessibility 

and reliability, develop design methods, establish safety and environmental standards, and 

demonstrate the technology at a commercial scale. 

REFERENCES 

British Wind Energy Association (BWEA), 2006a, “How Does an Offshore Wind Farm Work?” 

Available at http://www.bwea.com/offshore/how.html. Accessed May 11, 2006. 

BWEA, 2006b, “Offshore Wind, Frequently Asked Questions.” Available at http://www.bwea.

com/offshore/faqs.html. Accessed May 9, 2006. 

BWEA, 2006c, “BWEA Briefing Sheet, Offshore Wind.” Available at http://www.bwea.com/

pdf/briefings/offshore05_small.pdf. Accessed May 9, 2006. 

Danish Wind Industry Association (DWIA), 2006, Series of articles on wind energy economics. 

Available at http://www.windpower.org/en/tour/econ/economic/htm. Accessed May 9, 2006. 

U.S. Department of Energy (DOE), 2006, “U.S. Department of Energy to Develop 

Multimegawatt Offshore Wind Turbine with General Electric,” News Release, Office of Energy 

Efficiency and Renewable Energy, March 9. Available at http://www1.eere.energy.gov/

windandhydro/news_detail.html?news_id=9822. Accessed May 9, 2006. 

Florida Power & Light Company (FPL), 2006, “Long Island Offshore Wind Energy Center 

FAQ.” Available at http://www.fplenergy.com/projects/contents/long_island_wind_faq.

shtml#56. Accessed May 11, 2006. 

Gadomski, C., 2005, “Challenges Ahead for the U.S. Wind Industry,” Modern Power Systems, 

September, pp. 38−39. 

Larsen, Jens H.M., et al., 2005, “Experiences from Middelgrunden 40 MW Offshore Wind 

Farm,” Copenhagen Offshore Wind 26−28 October 2005. Available at http://www.

middelgrunden.dk/artikler/Copenhagen%20Offshore%207%20Middelgrund.pdf. 

Accessed May 11, 2006. 

Miller, D., 2006, “Wind Farms off the Texas Coastline?” KVUE news site. Available at 

http://www.kvue.com/cgi-bin/bi/gold_print.cgi. Accessed May 9, 2006. 

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Musial, W., 2005, “Offshore Wind Energy Potential for the United States,” Presentation at Wind 

Powering America⎯Annual State Summit, May 19. Available at http://www.eere.energy.gov/

windandhydro/windpoweringamerica/pdfs/workshops/2005_summit/musial.pdf. 

Accessed May 11, 2006. 

Musial, W., and S. Butterfield, 2004, “Future for Offshore Wind Energy in the United States,” 

Preprint for Energy Ocean 2004, Palm Beach, Florida, June 28−29, 2004. Available at 

http://www.nrel.gov/docs/fy04osti/36313.pdf. Accessed May 11, 2006. 

Offshore Wind Collaborative Organizing Group, 2005, “A Framework for Offshore Wind 

Energy Development in the United States,” Sept. Available at http://www.masstech.org/offshore/

final_09_20.pdf. Accessed May 9, 2006. 

Offshore Wind, 2006, “Why Offshore over Land Based Wind Energy?” Available at http://www.

offshorewind.net/wiki/index.php/Main_Page. Accessed May 9, 2006. 

Pellerin, C., 2005, “Wind Power World’s Fastest-Growing New Electricity Source.” Available at 

http://usinfo.state.gov/usinfo/Archive/2005/Apr/22-89769.html?chanlid=washfile. 

Accessed May 11, 2006. 

Siemens, 2006, “Special Applications, Offshore.” Available at http://www.powergeneration.

siemens.com/en/windpower/technology/offshore/index.cfm. Accessed May 9, 2006. 

Thresher, R., 2005, “Offshore Energy Hearing, Full Committee Hearing, April 19, 2005,” 

Dr. Robert Thresher, Director, National Wind Technology Center, National Renewable Energy 

Laboratory, Golden, Colorado, prepared statement. Available at http://energy.senate.gov/

hearings/testimony.cfm?id=1463&wit_id=4184. Accessed May 9, 2006. 

Webb, T., 2006, “Offshore Wind Farms Blown Off Schedule by Two Years,” The Independent, 

April 16. Available at http://news.independent.co.uk/business/news/article357900.ece. 

Accessed May 11, 2006. 

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