Wind Power Generation for Florida
A Position Paper by the Big Bend Climate Action Team
Tallahassee, Florida, 12 October 2007
Governor Charlie Crist said earlier this year that global climate change is one of the most important issues facing the State of Florida and observed that with its long coastline and high populations densities at the coast, “Florida is more vulnerable to rising ocean levels and violent weather than any other state.” As a consequence, it is vital that Florida come to grips with the paired problems of its growing energy demands and the need to reduce its reliance on fossil fuels. The state’s future energy should be increasingly delivered by two forms of alternative energy: (1) conservation and efficiency measures; and (2) those new renewable power sources that make best use of the state’s natural resources.(01)
The state is already making progress in both of these alternative energy realms. The Florida Energy Commission, together with citizen advisory groups, has met numerous times this year and is developing plans to make use of all of the non-fossil energy resources that are available and cost-effective for the state. Considerable potential exists for the substantial development of these resources, which, according to a 2007 study by the American Council for an Energy-Efficient Economy (ACEEE), can reduce Florida’s future electricity needs by almost half (45%) over the next 15 years. Our accompanying position paper titled “Ocean-Current Energy for Florida” (September, 2007) provides details of the ACEEE study.
Among renewable energy resources in wide use elsewhere are solar thermal and solar photovoltaic energy, hydroelectric energy, various forms of ocean energy, biomass, and wind energy. This paper examines the question of whether Florida should invest substantial resources in the last-named resource, wind energy.
The Wind Resource
The wind is a purely renewable resource. It cannot be used up. It is actually a form of solar energy: winds are caused by the heating of the atmosphere by the sun, the rotation of the earth, and the earth’s surface irregularities.
Wind speeds vary from zero to well over 100 mph, and they are much more constant at some locations than at others. The best sites for generating electrical energy those where the wind is steady and strong at a height above the ground where turbines can be installed and maintained. The energy available from wind varies with the cube of its speed (thus, a 20-mph wind delivers eight times more energy than a 10-mph wind), and according to the Wind Energy Association, the optimal wind speed for grid-connected applications is 11 miles per hour (5 meters per second). Slower speeds are adequate for non-connected applications such as pumping water and charging batteries. (02)
The wind industry rates wind power from class 1 to class 6 or higher according to the number of watts per square meter that a turbine can deliver at various heights above the ground. Table 1 shows these ratings for winds of various speeds for two heights—10 meters, and 50 meters.
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Table 1. Wind Power Ratings at 10 m and 50 m above the Ground
Wind 10 meters 50 meters
power Speed Speed
class (mph) (mph)
1 < 9.8 < 12.5
2 9.8 – 11.5 12.5 – 15.3
3 11.5 – 12.5 14.3 – 15.7
4 12.5 – 13.4 15.7 – 16.8
5 13.4 – 14.3 16.8 – 17.9
6 14.3 – 15.7 17.9 – 19.7
7 > 15.7 > 19.7
Source: American Wind Energy Association, “Basic Principles of Wind Resource Evaluation,” http://www.awea.org/faq/basicwr.html
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Currently, only the highlighted classes, 4 and above, are considered suitable for large-scale wind projects. Research is being dedicated to the development of grid-connected wind technology in areas with classes 3 and below.
Winds over Florida
The Wind Energy Resource Atlas of the United States says there is little wind energy potential in the Southeast Region for existing turbine applications: “Even along the coastal areas, existing data from exposed sites indicate at best only class 2 at 50 meters above ground. The only places in the Southeast region estimated to have a class 3 or higher annual average wind resource are the exposed ridge crests and mountain summits confined to northeastern Georgia and extreme northwestern South Carolina.” Maps in the Atlas show Florida experiencing class 2 winds for about 9 months of the year, dropping down to class 1 during the summer months.(03)
The American Wind Energy Association makes available a rank list of the top 20 states for wind power. First on the list is North Dakota, with 1,210 billion kWh annual energy potential. Number 20 is Missouri, with 52 billion kWh. Florida ranks somewhere below Missouri, suggesting that it is an unpromising area for the generation of electricity from wind.(04)
Offshore Winds
Off Florida’s shores, the potential for harvesting energy from winds may be greater. Historical wind data available from the National Buoy Center for the Florida Coast suggest that the areas offshore from Florida experience winds from classes 1 to 4. Most of the class 1 and 2 stations are located off Florida’s west coast between 27 and 30 degrees north latitude—that is, from about Venice to the Big Bend region. These stations have strong continental influence, since they are situated over the continental shelf. At the same time, they are far enough out so that they yield a good estimate of the strength of the wind in their area. Class 3 stations are located all along the east coast on the inner continental shelf between 26 and 32 degrees north latitude—that is, from Fort Lauderdale to the Georgia line; additional class 3 stations are off the extreme west coast at about Panama City. At these sites, turbines are active more than 80 percent of the time. There is also a class 3 station near the end of the Florida Keys archipelago, beyond Key West.(05)
In terms of production, wind data enabled the Geothermal Energy Group to identify three class 3 sites off Florida that might be suitable for wind power generation. These range from an average production per turbine of 1MW for Miami to about 1.15 MW for Jacksonville and Pensacola inner shelves. Off the Florida Keys archipelago, average turbine power production range between 0.7 and 1.0 MW.(06)
Further analysis suggests that a wind farm of a size similar to that of the wind farm planned for Cape Cod (130 turbines) on the inner continental shelf off Florida’s west coast should produce, on average, 169 MW. High productivity periods would occur 25% of the time and could achieve approximately 238 MW for class 3 turbines (and 295 MW for class 4). Minimum productivity periods would occur 75% of the time and would yield about 22 MW for class 3 turbines (26.5 MW for class 4). These are conservative estimates.
The Cape Cod wind farm is estimated to produce more energy than this. A total maximum output of nearly 3.23 MW per turbine (420 MW altogether) is anticipated. This corresponds to nearly 40% greater productivity than our class 4 stations could yield (with a 25% probability assumed for periods of maximum production).
The best candidates for the placement of offshore wind farms would be the Pensacola, Miami, and Jacksonville coasts. These are near densely populated areas. (We exclude Key West from this list not only because of the relatively weaker wind resource, but also due to the large area occupied by the Florida Keys National Marine Sanctuary.) From a practical point of view perhaps the best candidate would be the area close to Jacksonville. Jacksonville is the fourteenth-largest city in the United States, with a population of more than 800,000 people. As mentioned earlier, this region has a wind resource that averages 7 to 8 meter/sec winds over the inner continental shelf and turbines that are 80 to 85% active. An additional advantage of Jacksonville is that in 1999 it agreed with the Sierra Club and the American Lung Association that it would generate 7.5% of its energy from renewable sources by 2015. The Guana-Matanzas National Estuarine Reserve is nearby, but it could be avoided by a wind-farm project. In sum, the region has both the wind resources and the market for offshore wind power, and with proper study and planning, could resolve environmental issues.
Hurricanes and other extreme events are an issue of major concern in Florida for any construction near the shore and especially offshore. However, turbine design engineering is being developed to withstand such conditions. The actual feasibility for an implementation of a wind farm is not well defined since more studies are needed on the probability of occurrences of storms and hurricanes and on the behavior of wind turbines facing these extreme events. It seems, however, to be only a matter of time before these constraints are overcome.
Advantages and Disadvantages of Wind Energy
Wind energy offers many advantages, which explains why it is the fastest growing energy source in the world. Research efforts are aimed at addressing the challenges to greater use of wind energy.
Among its advantages, wind is a clean “fuel.” It doesn’t pollute the air as do power plants that rely on combustion of fossil fuels such as coal or natural gas. Wind turbines produce no greenhouse gases and no atmospheric emissions that cause acid rain. Moreover, wind energy is a domestic energy resource and the U.S. wind supply is abundant. Wind turbines can be erected on ranches or farms, thus benefiting the economy in rural areas, where most of the best wind sites are found. Farmers and ranchers can continue to work the land because the wind turbines use only a fraction of the land. Wind power-plant owners make rent payments to the farmer or rancher for the use of the land.
Wind energy is also one of the lowest-priced renewable energy technologies available today. It costs between 4 and 6 cents per kilowatt- hour, depending upon the wind resource and project financing.
The major challenge to using wind as a source of power is that the wind is intermittent and it does not always blow when electricity is needed. Wind energy cannot be stored (unless batteries are used); and not all winds can be harnessed to meet the timing of electricity demands. Wind power must compete with conventional generation sources on a cost basis, and depending on how energetic a wind site is, a wind farm may or may not be cost competitive. Also, even though the cost of wind power has decreased dramatically in the past 10 years, the technology requires a higher initial investment than fossil fueled generators.
Another disadvantage in some cases is that good wind sites are often located in remote locations, far from cities where the electricity is needed. Transmission and distribution costs mount up as distances grow.
Also, wind farms do occupy land. Although they may be compatible with other uses of the land such as farming or ranching, wind farms may compete with other land uses, and indeed with uses that may be more highly valued than electricity generation.
Wind power plants exert relatively little impact on the environment compared with other conventional power plants, but there is some concern over the noise produced by the rotor blades, aesthetic (visual) impacts, and in some areas, bird mortality. Most of these problems have been resolved or greatly reduced through technological development or by properly siting wind farms.
Conclusion
Available data indicate that Florida does not have the utility-grade winds (class 4 and above) that the current technologies of large wind generators require. As large turbine technology improves, some of Florida’s sites with lighter winds or located in deeper waters may prove to be usable. Further studies need to be conducted on the promising sites by qualified groups. Current research efforts are under way by the U.S. Department of Energy (see Appendix).
There may be small pockets of winds usable for community-based turbines that could serve windy coastal communities. Recent efficiency improvements and lower costs may make residential wind generators more attractive to individual homeowners who live in windy areas.
At this point in time, the Big Bend Climate Action Team finds that the most promising renewable resources for future use in Florida are solar thermal, solar photovoltaic, and ocean-current energy.
The mission of the Big Bend Climate Action Team (BBCAT) is to help local governments, businesses, and citizens to do their share to abate climate change by reducing fossil fuel use and promoting energy efficiency, conservation, and renewable fuels in power plants, buildings, and vehicles. We are concerned that climate disruption, caused primarily by human use of fossil fuels, is already occurring and is rapidly becoming more severe. We know that many forms of alternative energy are available and cost-effective and that the growing energy needs of populations in our region must for the foreseeable future be met by using less fossil fuel and more efficiency and renewable resources.
References
01 Governor Charlie Crist, State of the State Address, 6 March 2007.
02. American Wind Energy Association, “Basic Principles of Wind Resource Evaluation,” http://www.awea.org/faq/basicwr.html
03. Elliott, D.L., C.G. Holladay, W.R. Barchet, H.P. Foote, and W.F. Sandusky, Wind Energy Resource Atlas of the United States, prepared for the U.S. Department of Energy and published by the Solar Technical Information Program and the Solar Energy Research Institute [now the National Renewable Energy Laboratory], October 1986. http://rredc.nrel.gov/wind/pubs/atlas/
04. http://www.awea.org/pubs/factsheets/Wind_Energy_An_Untapped_Resource.pdf
05. Green, B. D. and R. G. Nix, Geothermal—The Energy Under Our Feet, U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, 2006 November, http://www.nrel.gov/docs/fy07osti/40665.pdf
06. Green and Nix, 2006.
Appendix
Current Research into Offshore Wind Technology (U.S. Department of Energy)
The Wind and Hydropower Technologies Program is leading research into offshore construction of wind power plants. Several offshore wind projects on the east coast have sparked interest in building wind turbines to harvest offshore winds. Until now, the program didn’t focus on offshore wind power development because there is great potential on land for wind power and offshore development is more expensive. However, on the northeast coast of the United States offshore development is an attractive alternative because electricity costs are high and land based transmission line construction faces many obstacles.
Europeans have some experience with offshore wind energy projects, but these have been in sheltered, shallow water sites. U.S. offshore locations with significant wind resources do not match previously developed European sites well. Many of the U.S. sites will require the application of technologies that have yet to be explored or seriously considered in Europe, especially those that will allow development in deeper waters, which may have greater wind, wave, and ice loading. In addition, numerous environmental, political and regulatory issues exist in the US, which must be dealt with in the near term before significant development can get under way.
The offshore installations will see very different environments and energy density. These turbines also need to be designed with confidence in the nature of the offshore winds (higher energy, lower turbulence) in combination with wave and current loadings at the base. Both these environments need to be specified sufficiently to allow designers to optimize the system for the conditions at the site. Current approaches to design specifications are not capable of providing such a complete designation of site design conditions.
Research activities will include developing technology for offshore sites, mapping coastal wind resources, tracking European projects and studies, and organizing workshops.
Source: U. S. Dept. of Energy, Energy Efficiency and Renewable Energy, Wind and Hydropower Technologies Program, http://www1.eere.energy.gov/windandhydro/wind_offshore.html
