Offshore wind has the potential to address all three issues: the energy supply, the environment, and the economy. Offshore wind uses the vast renewable wind resources adjacent to the ocean perimeter of the United States, which are domestic, indigenous, inexhaustible energy supplies in close proximity to our urban energy load centers. Offshore wind turbines can convert the strong ocean winds into clean, renewable power with no harmful emissions. Offshore wind has the potential to contribute significantly to the revitalization of the U.S. manufacturing sector, which will help strengthen both the economies of coastal states and the U.S. economy as a whole.
Recognizing these issues, the Obama administration has strengthened the nation’s commitment to renewable energy and clarified some of the actions needed to reduce our dependence on fossil fuels and bring emission levels in line with IPCC recommendations. The administration has set forth the following specific clean energy actions for the United States (White House 2009):
• Double this nation’s supply of renewable energy in the next 3 years.
• Invest $15 billion per year to develop technologies like wind power and solar power, advanced biofuels, clean coal, and more fuel-efficient cars and trucks.
• Cut our carbon pollution by about 80% by 2050, and create millions of new jobs.
• Lease federal waters for projects to generate electricity from wind, as well as from ocean currents and other renewable sources.
• Put the nation on the path to generating 20% or more of our energy from renewable sources by 2020.
As a contributor to the overall solutions, the offshore wind resource in the United States has the potential to deliver substantial amounts of clean electricity to U.S. consumers. The National Renewable Energy Laboratory (NREL) estimates that the gross U.S. offshore wind resource over
all water depths, in regions with annual average wind speeds greater than 8.0 m/s, is 2,957 GW (1 GW = 1,000 MW).2 If average winds of 7.0 m/s are included, the estimated wind resource grows to 4,150 GW (Heimiller et al. 2010; see also Section 4). This is approximately four times the electricity generating capacity of the U.S. electric grid. Although these numbers provide only an upper bound, they demonstrate that for 54-GW offshore wind scenarios like those defined in the U.S. Department of Energy’s (DOE) 20% Wind Energy by 2030: Increasing Wind Energy’s Contribution to U.S. Electricity Supply (the “20% report” or the “20% scenario), the offshore wind resource supply is not the primary issue determining deployment (DOE 2008).3
Wind speeds generally increase significantly with distance from the coast, resulting in a higher annual energy production than a similar turbine sited on land. Table 2-1 shows how sites with higher wind speeds—such as those found offshore—translate into high energy production. The table illustrates that an increase of two wind power classes (the difference that can be reasonably expected between a typical “Class 4” land-based site and a typical “Class 6” offshore site) would result in a gain of about 29% in annual average energy production for an NREL reference wind turbine (Jonkman et al. 2009).
Table 2-1. Energy Production by Wind Power Class Average Annual Wind
Speed (m/s) Wind Power Class Change in Energy Production Relative
Source: Elliott et al. 1987.
a The relative change in energy production was computed using NREL’s 5-MW reference wind turbine parameters, varying only the annual average wind speed. Actual turbine performance could be optimized for site-specific design conditions.
In addition to being plentiful, the offshore wind resource of the United States is broadly
distributed. Thirty U.S. states border an ocean or Great Lake. The offshore wind resource exists within reasonable distances from major urban load centers, reducing the need for long-distance power transmission. These urban areas are home to much of the U.S. population; have the highest electricity prices in the nation; and currently depend heavily on a high-carbon, volatile supply of imported fossil fuels. According to the EIA (2007), the 28 coastal states in the lower 48 states4 generate 75% of the nation’s electricity (3,108 TWh of 4,157 TWh generated nationally in 2007).5
2 This estimate is based on wind speeds at a 90-m elevation (hub height of the reference wind turbine) and includes all regions out to 50 nm. The estimate assumes that 5 MW (or about 1 turbine) of installed capacity would be installed in every square kilometer. This estimate includes the coastal regions for all of the lower 48 contiguous states with no exclusions.
The electricity generated in the U.S. coastal states represents 16.6% of the
3These resource estimates do not assume any exclusion areas where wind development would not be allowed. Judging from land-based experience, exclusion zones would result in at least a 60% reduction of the available resource.
4 Alaska and Hawaii, although remote, have abundant offshore resources and could become electrically self-sufficient using offshore wind in conjunction with other renewables, along with smart grid and storage technologies. These states are treated separately, though, because they are isolated and cannot distribute power to other states.
5 Electric energy generation figures published by the EIA can provide a rough estimate of the energy consumed by the same state.
In some cases generation is transmitted across state boundaries or generation can take place behind the meter, as in large
world’s total electricity (world electric energy generation was approximately 18.77 TWh in 2007; EIA 2010a). As such, the electricity consumption of U.S. coastal states has a large impact on the world’s carbon emissions. These states could significantly reduce global GHG emissions if they choose to adopt renewable energy solutions such as offshore wind.
In coastal areas of the United States, offshore resources tend to dwarf the land-based wind component. Most coastal states do not have optimal land-based wind energy resources with the exception of a few: California, Oregon, Texas, Washington, and Maine. If offshore and land-based wind resources are counted together, coastal states would have sufficient wind resources to make wind energy a significant part of their electricity profiles (see sections 3 and 4). For many of these states, offshore wind is the most abundant indigenous energy source and the only commercial option for renewable power generation. This is especially true in some southern states where land-based resources become scarcer with decreasing latitude. Most other alternatives involve importing energy across state lines, which would require building up
interstate transmission corridors or depending even more on fossil-fueled electricity generation.
U.S. wind energy generated offshore has the potential to compete economically in highly populated coastal energy markets where land-based wind energy is less available. Figure 2-3 shows that the offshore resource tends to be geographically located near states with high electric utility rates (EIA 2007). Figure 2-3, which is based on retail energy prices obtained from the EIA, also shows that the Mid-Atlantic and northeastern states have significantly higher
electricity prices than the national average of $0.099/kWh.6 These prices are higher than inland and southern retail electricity prices, where energy prices are generally lower because of a fuel mix that relies heavily on imported coal and nuclear generation. The Pacific Northwest also has low electricity prices resulting from abundant hydropower resources (UCS 2010).
industrial facilities. Electric energy generation exceeds the energy consumption based on EIA retail sales. Generation is a better metric for stating total U.S. electricity demand.
6 Ideally, the cost of offshore wind should be compared to wholesale electricity price data, not retail price data, though these metrics are expected to follow the same trends. This analysis does not address the fact that many external costs (e.g., public health, emissions, and nuclear waste disposal) are not included in the market price of energy
Source: EIA 2007.
Figure 2-3. Coastal versus inland state electric rates (2008)
Regionally high electricity costs in congested offshore areas, more energetic wind regimes, and closer proximity to grid interconnects might allow offshore wind to compete, even at higher initial costs, in many coastal areas. Although capital costs for offshore wind energy will remain higher than those of land-based wind energy systems, unique regional market conditions and enhanced offshore turbine performance will, at least partially, offset the difference.
Increasing the percentage of renewable energy generation in our nation’s fuel mix has the potential to significantly reduce harmful emissions. Although offshore wind projects have high capital costs, they have no fuel costs and low operating costs. These characteristics allow the turbines to produce energy at a much lower marginal cost than fossil-fuel power plants. As a result, offshore wind turbines displace power that otherwise would have been generated by the fossil-fuel plants and avoid any emissions that would have resulted from the combustion of the fuel. The specific type of displaced generation will vary by region and is dependent on the mix of generation in the area (Jacobson and High 2008).
DOE’s Wind and Water Power Program has led a number of initiatives to drive down the cost of wind energy through sustained technology innovations (NWTC 2006a, 2006b). These targeted cost reduction programs are partially responsible for the dramatic reduction in the cost of land-based wind energy and subsequent acceleration in deployment. During the past two decades, land-based wind energy has seen a tenfold reduction in cost and is now competitive with
fossil-fuel and nuclear power generation. Over the same time period, deployment has increased from 1,800 MW in 1990 to 35,603 MW at the end of 2009 (AWEA 2010).
Although cost-competitiveness remains an important driver for wind energy deployment, the industry faces new challenges that must be overcome if current wind energy growth rates are to be sustained and projections of 20% wind energy by 2030 are to be met (see DOE 2008). The availability of electric transmission, the firm delivery of generated wind capacity, the long-term cost and reliability of the turbine equipment, and the availability of critical supply chain growth all challenge the nation’s ability to meet these projections.
Fifty-four gigawatts of offshore wind will be required to achieve the 20% scenario. But other recent studies present detailed and compelling analyses indicating that 20% or 30% wind electricity cannot be realized in the United States without developing both land-based and offshore wind resources (see, for example, EnerNex 2010). Offshore resources must be
developed in high wind-energy penetration scenarios mainly because of transmission constraints and load balancing concerns.
Offshore wind projects offer a number of cost reduction opportunities and advantages that are unique when compared to land-based projects. These opportunities include fewer restraints on turbine size, reduced transmission requirements, and the ability to site projects farther from human use areas.
The generation cost of offshore wind could be lowered by taking advantage of larger turbines than those typically employed for land-based wind energy. Most wind turbine manufacturers are preparing 5-MW offshore machines for large-scale commercial deployment and several
manufacturers have designs in the range of 8 to 10 MW on the drawing board. The shipping and lifting capacities of marine equipment and vessels still far exceed the installation requirements for the current generation of multimegawatt offshore wind turbines. In contrast, the size of land-based turbines is restricted by the capacity limits of the existing transportation and erection equipment. The capacity limits of the existing equipment is causing the growth of land-based wind turbines to level off. This is a significant advantage for offshore wind because larger machines could significantly lower the installation and balance-of-station (BOS) costs, per kilowatt, for offshore wind projects. The challenges of building larger machines, however, have not been fully explored (see Section 5).
The 20% scenario estimates that 305 GW of installed wind power (land-based and offshore combined) would avoid 825 million metric tons of CO2 in 2030 for a cumulative total of 7,600 million tons of CO2 from 2010 to 2030. For comparison, the U.S. electric sector currently emits about 2,500 million metric tons of CO2 per year (EIA 2010b).
Developing a domestic wind industry offers a viable way to revitalize our domestic manufacturing sector and create high-paying, stable jobs while increasing the nation’s competitiveness in twenty-first century energy technologies. In the 20% scenario, 54 GW of offshore wind would create more than $200 billion in new economic activity with a high percentage of that revenue remaining in the local economies. This offshore wind power
development would create many benefits beyond the $200 billion in revenues because the power generated would have no fuel price variability, no emissions, and no significant use of water resources. Finally, offshore wind development would reduce dependence on foreign energy resources (DOE 2008).
Most of the labor for offshore wind will draw from local and regional sources that cannot be easily outsourced overseas. Analysis done at NREL, extrapolated from European studies (EWEA 2009), estimates that offshore wind will create approximately 20.7 direct jobs per annual
megawatt in the United States. In addition, approximately 0.8 jobs would be created for every cumulative megawatt of offshore wind in operation. If 54 GW were installed under the 20%
scenario, more than 43,000 permanent operations and maintenance (O&M) jobs and more than 1.1 million job-years would be required to manufacture and install the turbines (GWEC et al.
2008; Musial 2007).
Land-based wind resources are generally located far from population centers and require significant transmission capacity to deliver electricity to load centers. Recent evidence shows that the development of high-quality land-based wind sites is being constrained by limited access to transmission and that the output of operational wind farms is increasingly being curtailed by system operators as a way of reducing congestion (Piwko et al. 2005; Fink et al. 2009). These examples suggest that transmission will be a primary near-term barrier to large-scale
development of land-based wind projects in the United States. Although the nation needs to develop both land-based and offshore resources, offshore wind is less likely to be affected by congestion in the transmission system. Offshore wind resources are located close to coastal urban load centers. attribute that could be very valuable to utilities in helping to alleviate transmission constraints.
Both land-based and offshore wind projects face issues associated with their visible impact.
Aesthetic concerns may continue to be an issue whenever turbines can be seen from populated areas but offshore wind projects have the advantage of being located farther from inhabited areas than most land-based projects. With the development of new technology for deeper waters, offshore wind turbines could eventually be sited far enough from shore to virtually eliminate visual impacts. Offshore wind turbines also have the potential to eliminate human objections to sounds from turbines because most projects would be sited beyond the threshold of sound propagation. Public concerns about other factors such as the effects on local tourism, rights to private use of the public commons, and possible avian collisions with turbines suggest that further studies on these impacts will be necessary (Kempton et al. 2005). Wide-ranging environmental and social issues have been investigated in existing European wind farms for more than 10 years, and no significant environmental impacts have been identified (see Section 8; see also Nielsen 2003; DONG Energy 2006). As a result, public concerns about offshore wind can be expected to wane as consumers gain comfort with this technology. Studies have shown that when the public is faced with an energy choice between offshore wind and other forms of electricity generation, offshore wind energy is considered preferable (Firestone, Kempton, and Krueger 2009).
2.5 Findings and Conclusions
Looking toward the future, offshore wind appears to be a leading contender to provide a substantial portion of a low-carbon energy supply. In 2007, the European Union (EU) and the European Wind Energy Association (EWEA) established aggressive targets to install 40 GW of offshore wind by 2020 and 150 GW by 2030. In the United States, there are no offshore wind projects yet but interest is growing with greater than 2,000 MW of offshore wind in the detailed planning, site development, and approval process (see Section 3). Based on the U.S. experience to date, regulatory and permitting issues will have a large effect on the pace at which offshore
development can progress. The Minerals Management Service (MMS; renamed the Bureau of Ocean Energy Management, Regulation and Enforcement (BOEM) in June 2010) has
traditionally taken a cautious approach to permitting and certification for offshore wind projects.
The MMS published the final rules for wind energy development on the Outer Continental Shelf in April 2009 (MMS 2010). Multiple agencies and industry members are now looking at the implications of this rule with respect to the total regulatory process time frame and further clarifications are expected as experience with the process is gained.
Although offshore wind development is sure to benefit from continued innovation associated with land-based growth, experience has shown that offshore wind cannot be simply extrapolated from land-based experience alone. Establishing a competitive, mature offshore wind industry in the United States will require dedicated investment in technology research specific to offshore conditions. European countries have already installed more than 2,000 MW of offshore capacity and the experiences gained from these initial deployments are supporting new technology developments that have the potential to lower costs (see sections 5 and 6). Offshore wind faces many near-term technical and regulatory challenges that must be addressed before the
technology can compete broadly in U.S. energy markets. The remainder of this report focuses on these challenges.