Chapter 2 The National Wind Resource
This chapter presents a summary of the United States wind energy resource on a region-by-region basis. The regions are identified on the map shown in Map 3-1; the numbers on the map indicate the order in which the regional information is presented. For each region, major wind resource areas are described that have been estimated to have suitable wind energy potential for wind turbine applications (class 3 or greater annual average wind power).
The regional summaries are accompanied by regional and state maps. The regional maps display major cities, mountain ranges, and geographic features. The state maps show the geographic distribution of annual average wind power and depict prominent wind energy areas and other geographic features. Chapter 1 gives information on interpreting the wind power maps.
A latitude-longitude grid is superimposed on each state map to facilitate locating specific places on the maps. The grid cells are 1/4° latitude by 1/3° longitude for states in the contiguous United States. This corresponds to grid cells that are approximately 25 by 25 km (15 by 15 mi). For Alaska, grid cells are 1/2° latitude by 1° longitude. For Hawaii, Puerto Rico, and the U.S. Virgin Islands, grid cells are 1/8° latitude by 1/8° longitude.
Some of the larger states (i.e., Alaska, California, and Texas) are subdivided for the purpose of presenting the analyses more clearly. Some of the smaller states (i.e., Massachusetts, Connecticut, and Rhode Island; Vermont and New Hampshire; and Maryland and Delaware) are combined as a set of states on one map.
The Northwest region consists of Idaho, Montana, Oregon, Washington, and Wyoming. Almost half of the region's people live in western Washington and Oregon, where the region's two largest citiesSeattle and Portlandare located. The major cities, rivers, mountain ranges, and national parks are shown in Map 3-2.
The topography varies dramatically throughout the Northwest, which is dissected by the Cascade Range in the western part of the region and by the Rocky Mountains in the central and eastern parts of the region. Over one-third of the region's terrain is hilly and mountainous. Much of the mountainous terrain, and western Washington and Oregon, are heavily forested.
Areas of good wind energy potential are dispersed throughout the Northwest. Some notable areas where wind energy developments have occurred are the Columbia River corridor along the Oregon-Washington border between Portland and Boardman, Oregon, 275 km (170 mi) to the east of Portland; the Ellensburg corridor in central Washington; the Oregon coast; southern Wyoming (especially around Medicine Bow); and the Livingston corridor in southwestern Montana. Goodnoe Hills, located approximately 200 km (120 mi) east of Portland, is the site of three MOD-2 wind turbines currently being monitored by DOE. Medicine Bow, in southeastern Wyoming, has also served as a field test location for several large wind turbines. DOE sponsored measurement programs at seven sites in the Northwest region: Livingston, Montana; Boardman and Cape Blanco, Oregon; Augsburger Mountain, Diablo Dam, and Goodnoe Hills, Washington; and Bridger Butte, Wyoming. The Bonneville Power Administration has taken wind measurements at numerous sites throughout the western part of the Northwest region. The Bureau of Reclamation and Western Area Power Administration, among others, have also been active in selecting sites and measuring the wind resource for potential wind turbine applications.
Considerable amounts of new data have been collected throughout the Northwest region since the completion of the regional atlas (Elliott and Barchet 1980). Analyses of these new data have resulted in some significant changes in the wind energy analysis from the previous analysis.
Major areas in the Northwest region with class 3 or greater annual average wind power are described below. Maps of annual average wind power are presented as Maps 3-3 through 3-7 for Idaho, Montana, Oregon, Washington and Wyoming.
The estimated annual average wind power for exposed coastal areas of Oregon and Washington is class 4 at 50 m (164 ft). Specific sites that experience terrain-induced acceleration of the wind may have greater than class 4 power. The abrupt increase in surface roughness inland from the coastline, because of vegetation and topography, rapidly attenuates the wind resource landward. During winter, the season of maximum wind power at sites well-exposed to the prevailing south and southeasterly winds, high wind speeds are usually associated with storms and fronts moving in from the Pacific Ocean. However, during the summer, wind power is high along the central and southern Oregon coast at sites well-exposed to northerly winds and is associated with the strong surface pressure gradients created by the cold water and relatively warm interior.
The Columbia River wind corridor straddles the Oregon-Washington state border from just east of Portland, Oregon, to Boardman, Oregon (which is about 70 km or 40 mi west of Pendleton, Oregon). Goodnoe Hills, the site of three MOD-2 wind turbines, is located on a ridge in the eastern part of the Columbia River corridor.
The Columbia River gorge provides a low-elevation connection between continental air masses in the interior of the Columbia Basin east of the Cascade Range and the maritime air of the Pacific coast. Especially strong pressure gradients develop along the Cascades and force the air to flow rapidly eastward or westward through the gorge. Summer winds blow eastward from the cool, dense maritime air west of the Cascades to the hot, less dense air in the Columbia Basin. In winter, the comparatively cold air in the Columbia Basin frequently blows westward through the gorge.
Although the Columbia River corridor is generally an area of high wind resource, terrain variations cause considerable local variability in the wind resource. The wind resource has been measured at numerous sites throughout the Columbia River corridor, and the annual average wind resource at exposed areas ranges from class 3 to class 6. Spring and summer are the seasons of maximum wind power, except for the extreme west end where the maximum resource is in winter.
Near Ellensburg, Washington, another breach occurs in the Cascade Range, which separates maritime and continental air. Unlike the Columbia River gorge, the central Washington corridor consists of relatively low mountain passes leading into a broad valley corridor to the east. In winter, the cold, dense air to the east of the passes occasionally becomes deep enough to spill westward into the Puget Sound. However, in late spring and summer the cool, marine air over western Washington is often deep enough to flow eastward over the passes and through this valley corridor into the Columbia Basin.
Data from several sites throughout the central Washington corridor indicate that exposed areas have class 4 to 5 annual average wind resource, with class 6 resource during the spring and summer seasons. This high wind resource area extends eastward over the low ridges to Wanapum Dam on the Columbia River, about 50 km (30 mi) east of Ellensburg.
Areas of class 4 and 5 annual average wind power exist over the plains of northwestern Montana from near the Rocky Mountains eastward to Cut Bank and Great Falls. The highest wind energy occurs from October to April, when strong westerly to southwesterly winds frequently occur in association with intense surface pressure gradients. The seasonal average wind resource varies from a maximum of class 6 in winter to a minimum of class 2 and 3 in summer. New data collected at several sites throughout this region indicate that the highest wind resource exists in the northern part of the region, east of Glacier National Park in the vicinity of Browning and Cut Bank.
Areas with up to class 6 annual average wind resource, are found in several valley wind corridors in southwestern Montana. Three such areas that have been identified are located in the vicinities of Livingston, Whitehall, and Harlowton-Judith Gap. Another valley corridor of high wind resource (class 4) is located in northwestern Wyoming in the vicinity of Cody. Strong winds in these corridors are often associated with strong surface pressure gradients. The channeling effect of the valleys and the local terrain intensifies the winds set in motion by the pressure gradients. Prevailing strong winds at Livingston, Whitehall, and Cody are primarily from the southwest quadrant, in alignment with the orientation of the valley corridors. However, the Harlowton-Judith Gap area experiences frequently strong northerly winds caused by channeling of flow between the Little Belt and Big Snowy mountains.
All of these wind corridors have pronounced seasonal variations in wind power density, with a maximum power density in the winter. Neighboring valleys and basins lacking the appropriate orientation show a significantly reduced wind resource.
Wind data have been collected at several new sites throughout southwestern Montana and northwestern Wyoming since the late 1970s. These data indicate that considerable local variability exists in the wind resource in the vicinity of these wind corridors, although well-exposed sites can have up to class 6 to 7 annual wind power. The only known site where winds have been measured up to heights near 50 m (164 ft) above ground was the DOE candidate site at Livingston, where class 6 annual wind resource was measured.
An area of high wind energy extends across southern Wyoming from the Utah border on the west to the Nebraska border on the east. This zone of high wind energy can be attributed to a major gap, about 150 km (90 mi) wide, in the north-south barrier of the Rocky Mountains. Prevailing westerly and southwesterly winds blow with little resistance through this gap across the relatively high plains and uplands of southern Wyoming. As a result, this is the largest region of non-mountainous terrain in the Northwest with a high wind energy resource.
Wind measurements taken throughout the extent of this high wind corridor in southern Wyoming indicate that exposed areas have class 4 to 6 annual average wind resource. Areas of highest wind resource occur where there is enhanced channeling by the terrain (e.g., between two mountain ranges) and/or where there is terrain-induced flow acceleration (e.g., over hilltops, uplands, or low ridges). One large area of exceptionally good wind energy potential occurs from near Rawlins eastward to Medicine Bow and the Laramie Mountains and southward along the Laramie Mountains divide to the Colorado border. Several large wind turbines have been installed in the Medicine Bow area.
Wind measurements from a DOE candidate site at Bridger Butte, in extreme southwestern Wyoming near Fort Bridger, showed class 6 annual average wind power at heights to 50 m (164 ft). Aircraft measurement (Dawson and Marwitz 1981) and surveys of eolian land forms (Marrs and Kopriva 1978) throughout southern Wyoming also indicate areas of very high wind energy potential. However, considerable variability in the wind resource exists in certain areas, especially where there are local terrain influences.
Winter is the season of maximum wind power, with class 7 power in the best areas. In summer, the season of minimum wind power, class 3 power can be expected in the best areas.
Class 3 and 4 annual average wind resource occurs over the open plains and upland areas throughout eastern Montana and northeastern Wyoming. There are relatively few wind measurement sites in this vast area, aside from airfield stations near the larger towns and cities. New data from the uplands area east of Circle, Montana, indicate class 4 wind energy potential.
At least class 3 or higher wind power is estimated for most of the exposed mountain summits and ridge crests throughout the Northwest except for some of the lower, forested summits of Oregon and Washington. Average wind speeds may vary significantly from one ridge-crest site to another and are primarily influenced by the height and slope of the ridge, orientation to the prevailing winds, and the proximity of other mountains and ridges. Winter is the season of highest wind power over most mountain summits and ridge crests in the Northwest because mean upper-air wind speeds are highest during this season. However, severe icing, access problems, and damaging storm winds severely restrict the suitability of wind energy development for many of the higher mountain summits and ridge crests in the Northwest.
The North Central region, (Map 3-8), consists of Iowa, Minnesota, Nebraska, North Dakota, and South Dakota. Two-thirds of the residents live in Iowa and Minnesota. The region is largely rural.
The topography of the region is generally flat plains to rolling hills and uplands, with the exception of the mountainous Black Hills area of western South Dakota. Topographic features in the North Central region, especially in the eastern Dakotas, Minnesota, and parts of Iowa, are largely the result of glaciation, with flat areas that are the beds of ancient lakes. Consequently, a large fraction of the land area is well exposed to the wind.
Class 3 and higher wind energy potential exists at exposed areas throughout the North Central region except for portions of eastern Minnesota, southeastern Iowa and the Missouri River lowlands along the Nebraska-Iowa border. As a result of new measurement programs beginning in the late 1970s and early 1980s, several areas in the North Central region, notably in North Dakota, indicate significantly greater wind energy potential than previously estimated (although higher wind power was speculated) in the regional atlas (Freeman et al. 1981). These new measurements indicate that the annual average wind resource is class 5, and possibly class 6, in certain areas.
Very strong nocturnal shear is evident from data collected at a DOE-installed meteorological tower near Finley, North Dakota, such that the average annual wind shear increases at a rate much greater than that predicted by a 1/7 power law. Thus, data collected near 10 m (33 ft) may not provide a realistic indication of the wind power and diurnal variation at 50 m (164 ft). However, at other areas in the North Central region, such as Huron, South Dakota, the nocturnal wind speeds at 50 m (164 ft) are substantially less than those at Finley, North Dakota. Finley, located on an upland above an escarpment, is slightly elevated with respect to its regional terrain environment, whereas Huron, located in the James River plain, is slightly lower than the uplands to the east and west of the river plain.
Thus, minor variations in elevation appear to have a very significant influence on the wind energy resource in the northern Great Plains. Additional data are needed to evaluate the nature of the low-level nocturnal jet in this region and its effect on the spatial and temporal variation of the wind energy resource with respect to minor variations in elevation. Major areas with class 3 or greater annual average wind power are described below. Maps of annual average wind power are presented as Maps 3-9 through 3-13 for Iowa, Minnesota, Nebraska, and North and South Dakota.
The Canadian wind corridor is a wide, flat area that comprises most of the central part of the North Central region. It is characterized by low relief and low surface roughness and is, thus, well-exposed to the strongest winds, which are mostly northerly to northwesterly in all seasons except summer. This area appears to have a significant effect in channeling cold arctic air from the Canadian interior southeastward into the United States during the winter. Strongest winds occur in conjunction with the passage to the east of migratory low-pressure systems that originate in the lee of the Rocky Mountains. This entire area is estimated to have class 4 annual average wind power.
Within this general area is the Red River valley. The Red River forms much of the boundary between North Dakota and northern Minnesota. This valley slopes downward to the north as the Red River flows northward into Lake Winnipeg. Data from stations near the Red River indicate some channeling effect, with prevailing winds being split between north and south directions. Data from Pembina and Grand Forks indicate annual wind power averages that are near the borderline between class 4 and class 5.
The Missouri Escarpment is an area of abrupt east-to-west rise of about 200 m (600 ft) in the otherwise flat terrain of eastern and central North Dakota and eastern South Dakota.
Left by receding glaciers, this feature is near the approximate western boundary of the Canadian wind corridor. The Pembina Escarpment is similar to the Missouri Escarpment and is located west of the Red River, forming the approximate western boundary of that valley. The Turtle Mountains are located on the Canadian border in north-central North Dakota, with elevations about 200 m (600 to 700 ft) higher than the flat terrain to the south.
Wind measurements from new sites located on hilltops and uplands at the top of these escarpments indicate that these areas have class 5 annual average wind resource at 50 m (164 ft), with class 6 possible in some places. Almost 2 years of data from the DOE-installed site at Finley, North Dakota, located above the Pembina Escarpment, indicate class 6 at 50 m (164 ft) with maximum wind power at night. Class 4 power was measured at 10 m (33 ft), and the diurnal variation at 10 m (33 ft) was completely reversed from that at 50 m (164 ft). Data from another DOE-installed site located south of Minot, North Dakota, at the top of the Missouri Escarpment, indicate class 5 wind power. New site data collected near 10 m (33 ft) above ground by Bureau of Reclamation and Western Area Power Administration indicate class 4 and 5 power in the upland areas of the Missouri Coteau, located between the Missouri Escarpment and the Missouri River.
Maximum wind power occurs in spring, with class 6 to 7 power at 50 m (164 ft). The new data at Finley and Minot show very strong nocturnal wind shear during the summer and surprisingly high wind energy potential at 50 m (164 ft), class 6 and 4, respectively, for the summer season. Previous estimates of the summer wind resource in the regional atlas were only class 2 for these areas. However, longer-term data at 50 m (164 ft) are needed to verify the higher summer resource measured at Finley and Minot, which is based on only two summers' data.
The Prairie Coteau is a basin-like plateau, rising about 200 to 250 m (656 to 820 ft) above the surrounding flat terrain, and containing numerous small moraine lakes. It is bounded on the east by an extension of the Missouri Escarpment and on the west by a similar though lower ridge. Sloping downward to the south, its north end appears on topographic maps as a wedge pointed north into the Canadian wind corridor.
To the east of the Prairie Coteau, near the Minnesota-South Dakota border formed by Lake Traverse, is an area that forms a divide between the Red River and Minnesota River drainages. New data collected near 10 m (33 ft) indicate class 4 power over these areas; however, class 5 is possible at 50 m (164 ft) if strong nocturnal shear occurs over these areas. No data at 50 m (164 ft) are available to verify this estimate.
New site data collected near 10 m (33 ft) from hilltops and uplands of the Missouri Plateau of the western Dakotas and the Sand Hills of northwestern Nebraska that are well exposed indicate class 4 to 5 wind power. Several instrumented sites near an upland divide in southwestern North Dakota measured class 5 wind power. Class 5 wind power was also measured over an elevated area in north-central South Dakota. Most other exposed sites of Missouri Plateau and Sand Hills measured class 4 power.
Many of the valleys and drainages in the Missouri Plateau are frequently sheltered from prevailing winds. These valleys have a lower wind power class, especially in winter and autumn when these valleys tend to fill with cold air. The resulting high stability restricts vertical mixing so that winds in these valleys are not as strong as on the uplands and better exposed areas. Examples of this are Bismarck and Williston, North Dakota, which are located in sheltered areas of the Missouri River valley.
Exposed ridge crests and summits in the Black Hills are estimated to have at least class 4 annual average wind power. Average speed at any particular location depends on the elevation, orientation with respect to strong westerly winds, and proximity to other ridges and mountains. Wind power should be greatest at high elevations of the Black Hills that have wide-open exposure.
Exposed elevated sites in southern Minnesota and northwestern Iowa are estimated to have class 4 wind power, although no data from 30 to 50 m (98 to 164 ft) above ground were identified in these areas and surface data are very limited. Data from the Rochester Airport, located on an exposed ridge in southeastern Minnesota, indicate class 4 wind power. Limited data from northwestern Iowa and southwestern Minnesota also indicate class 4 power for exposed uplands. Class 3 wind power is estimated for exposed areas throughout the rest of Iowa, except for the extreme southeastern and southwestern parts of the state. Lower and more sheltered locations will have significantly less wind power, especially in winter and autumn when stable air in these lowlands restricts vertical mixing, causing wind speeds to be less than at higher locations.
In northeastern Minnesota, the Mesabi Range and Lake Superior shore are estimated to have class 3 annual average wind power. The Mesabi Range, which is oriented perpendicular to the strongest winds in the area, is estimated to have class 3 because of acceleration of winds blowing over this ridge. However, there were no data to verify this estimate.
The Lake Superior shore is exposed to the strong easterly winds from Lake Superior. Data from Duluth Airport indicate that strong easterly winds in this area may penetrate inland up to 25 km (15 mi). Thus, class 3 wind resource is estimated to extend inland up to 25 km (15 mi) from the shore.
The Great Lakes region consists of Illinois, Indiana, Michigan, Ohio, and Wisconsin. The major cities, lakes, rivers, and geographical features are shown in Map 3-14.
The topography of the region, relative to western sections of the United States, is not complex. The entire area is almost all glaciated; terrain ranges from flat in Indiana and Illinois to gently rolling in central and northern Wisconsin. The two exceptions are southeastern Ohio and extreme southwestern Wisconsin, where terrain is rugged and unglaciated. Areas near the Great Lakes have sandy bluffs and marshes. Glacial lakes are prevalent in Wisconsin and Michigan where the terrain is more hilly.
In the Great Lakes region, class 3 or higher wind energy potential is estimated for exposed coastal and offshore areas of Lakes Erie, Huron, Michigan, and Superior, hilltops and ridges in southwestern Wisconsin and in the upper part of Michigan's lower peninsula, and upland plains in west-central Illinois. Areas of highest wind energy potential in the region are the exposed coastal and offshore areas and islands of the Great Lakes. At least class 5 wind power can be expected over offshore areas of all the Great Lakes, with maximum wind power in the winter (class 6) and minimum wind power in the summer (class 3). Over offshore areas, prevailing strong winds are mostly from the northwest-to-southwest directions. Exposed coastal points along the eastern shore of Lake Michigan and along the northern and western part of Keweenaw Peninsula in Lake Superior are estimated to have class 5 wind power, because these areas are well exposed to the prevailing strong winds with a long fetch over the open waters.
Major wind resource areas in the Great Lakes region are described below in greater detail. Maps of annual average wind power are presented in Maps 3-15 through 3-19 for Illinois, Indiana, Michigan, Ohio and Wisconsin.
The annual average wind power for exposed coastal and offshore areas of Lake Michigan is estimated to range from class 3 to class 5. The abrupt increase in surface roughness inland from the coastline, because of vegetation and topography, rapidly attenuates the wind resource landward.
Areas of highest wind energy potential are the exposed offshore areas, islands and exposed capes, and points along the eastern shore of Lake Michigan. Class 5 wind power is estimated for these areas, with maximum wind power in the winter (class 6) and minimum wind power in the summer (class 3). Over the offshore areas, prevailing strong winds are mostly from the northwest-to-southwest directions. Exposed coastal points along the eastern shore of Lake Michigan are well exposed to these prevailing strong winds, which have a long fetch over the open water. The class 5 estimate for exposed coastal points along the eastern shore of Lake Michigan is verified by approximately two years of wind measurements at 30 and 46 m (98 to 151 ft) on a DOE-installed tower at Big Sable Point.
The western shore of Lake Michigan forms the eastern edge of Wisconsin and has an annual average wind power of class 3. This reduced wind power on the western shore reflects the prevailing westerly winds. Eastward-moving storm systems during the winter and late autumn are responsible for the easterly winds that flow off the lake. Thus, on the annual average, the wind power on the western shore is less than on the eastern shore but still reflects the influence of Lake Michigan. Lake breezes, which are maximized in the spring, also enhance the wind power potential along this shoreline.
Like the Wisconsin shore of Lake Michigan, the Lake Huron shoreline was estimated to have class 3 annual average wind power with class 4 possible at some of the most prominent capes. Offshore, wind power increases to class 5.
The average prevailing winds are westerly. In addition to lake breeze effects in spring, during the storm season (late fall through early spring) northeasterly and easterly winds frequently blow off the water. Because the low surface friction of the lake surface does not reduce the wind velocity, the annual average wind power along the coast is higher than inland. The abrupt increase in surface roughness inland from the coastline, because of vegetation and topography, rapidly attenuates the wind resource landward.
The coastal region of extreme northern Ohio has an estimated annual wind power of class 3, increasing to class 5 over offshore areas of Lake Erie. Prevailing northerly and westerly winds have a long, smooth fetch across Lake Erie, resulting in powerful winter and spring winds, especially along the coastal areas of northeastern Ohio. The shape of the coastline is such that exposed coastal sites can also experience strong onshore winds from the northeastern quadrant.
The annual average wind power along Lake Superior shorelines is estimated to range from class 3 to class 5, with class 5 existing at exposed areas along the northern Keweenaw Peninsula, Isle Royale, and offshore areas of Lake Superior. In some areas, class 3 and 4 wind powers are estimated to occur at exposed sites 15 to 35 km (10 to 20 mi) inland from the shoreline. In the western part of Michigan's upper peninsula, the class 3 and 4 wind power areas represent exposed sites along the coast and in the Gogebic, Porcupine, and Huron mountains, where the wind power estimates are representative only of well-exposed sites on the higher elevations.
In the northern part of Michigan's lower peninsula, exposed sites on elevated terrain features are estimated to have class 3 annual average wind power. These elevated terrain features comprise the higher mountains, hilltops, and uplands in this region.
Exposed hilltops and ridges in southwestern Wisconsin are estimated to reach class 3 annual average wind power. Although representative data from well-exposed sites have not been identified in southwestern Wisconsin, long-term data are available from a well-exposed airport site (Rochester, Minnesota) located on a ridge in extreme southeastern Minnesota. Based on the data from this site, similarly well-exposed sites on hilltops and ridges in southwestern Wisconsin were estimated to have class 3 wind power.
Uplands of west-central Illinois from Quincy to Springfield are estimated to reach class 3 annual average wind power, slightly higher wind energy potential than other inland areas of Illinois. Long-term data from the Springfield Airport gave the highest annual average wind power of any airport site in Illinois. No 50-m (164 ft) data were identified in this area of Illinois (Paton et al. 1980).
The Northeast region consists of Connecticut, Massachusetts, Rhode Island, Maine, New Hampshire, Vermont, New Jersey, New York, and Pennsylvania. The region's total population in 1980 of 49,136,000 represents approximately one-fourth of the nation's population. A large percentage of the people in the Northeast live in the corridor between Boston and Philadelphia, while large areas of northern Maine and upstate New York are quite sparsely populated. The major cities, rivers, lakes, and mountain ranges are shown in Map 3-20.
The topography varies dramatically throughout the Northeast. The Appalachian Mountains extend in a bank from northern Maine beyond the southern border of Pennsylvania. To the east of the mountains lie piedmont and coastal plain regions. West of the mountains the land becomes flatter as one approaches the Great Lakes. A large portion of the land area of the Northeast is composed of either hills and mountains or open hills and mountains, while large areas of Massachusetts, Rhode Island, Maine, and New York are plains containing hills. The only area of tablelands in the Northeast extends in an arc from the Hudson River valley, across central New York, and into northwestern Pennsylvania. Central and southern New Jersey contain the only true plains in the region.
Areas of class 3 or higher wind energy potential occur throughout much of the Northeast region. The primary areas of good wind energy resource are the Atlantic coast, the Great Lakes, and exposed hilltops, ridge crests, and mountain summits from Pennsylvania to Maine. Areas of highest wind energy potential (class 5 and 6) are the outer coastal areas such as Cape Cod and Nantucket Island, offshore areas of Lake Ontario and Lake Erie, and the higher mountain summits of the Appalachians. Winter is the season of maximum wind power throughout the Northeast region. During this season, all except the most sheltered areas have class 3 or better wind resource, and exposed coastal areas and mountain summits can expect class 6 or 7 wind resource. In summer, the season of minimum wind power, class 3 wind resource can be found only on the outer coastal areas and highest mountain summits.
Major areas of wind resource in the Northeast region are described below. Maps of annual average wind power are presented in Maps 3-21 through 3-26 for Connecticut, Massachusetts and Rhode Island (displayed on one map), Maine, New Hampshire and Vermont (displayed on one map), New Jersey, New York, and Pennsylvania.
The annual average wind power for exposed Atlantic coastal and offshore islands of the Northeast is primarily class 4, 5, and 6. Class 4 is found immediately along the coast, while class 6 exists along the outer capes and islands such as Cape Cod and Nantucket Island. Semi-enclosed bodies of water, such as Long Island Sound and Delaware Bay, have a lower wind resource (class 3).
When onshore flow occurs, the abrupt change in surface roughness inland from the coastline, because of vegetation and topography, rapidly attenuates the wind resource landward. The strongest onshore flow on the synoptic scale occurs most frequently in the winter and early spring and is associated with strong pressure gradients occurring with coastal storms.
Wind measurements up to 46 m (150 ft) above ground have been taken at four DOE-installed tower sites along the northeastern Atlantic coastNantucket Island and Provincetown, Massachusetts; Montauk Point, New York; and Block Island, Rhode Island. Long-term data (5 yr) from both Block Island and Montauk Point indicated class 4 annual average wind power at 50 m (164 ft) for those areas. Limited data (2 yr) from Nantucket Island and Provincetown indicated that these outer areas could have class 6 or better annual average wind power at 50 m (164 ft). At 10 m (33 ft), the annual average wind power varied considerably among these four sites and was only class 2 at Block Island and Provincetown. These data provide excellent examples of how local roughness features such as vegetation and buildings can reduce the wind power at levels near the ground and how near surface (10-m or 33 ft) data may not provide a realistic indication of the wind power at 50 m (164 ft).
An extensive area, including most of Vermont and New Hampshire, as well as much of Maine, Massachusetts, and Connecticut, has annual average wind power of class 3 or higher on exposed locations. Highest powers (class 5 and 6) occur on the best-exposed mountain and ridge tops in Vermont's Green Mountains, New Hampshire's White Mountains, and Maine's Longfellow Mountains. The remainder of the hilltops and mountain tops in this area that are outside of these major ranges have class 3 or 4 wind power. At the highest elevations this wind power increases to class 6 and 7 in the winter. Average wind speeds may vary significantly from one ridge crest to another and are primarily influenced by the height and slope of the ridge, orientation to the prevailing winds, and the proximity of other mountains and ridges. For example, the White Mountains are indicated to have class 6 wind power, but Mount Washington, at 1,917 m (6,288 ft) elevation, is known to have considerably greater wind power as a result of terrain-induced acceleration as the air passes over the mountain.
Wind power of class 3 and higher is estimated for the high elevations of the Adirondack Mountains of northeastern New York. Two of the highest mountains, Mt. Marcy and Whiteface Mountain, have at least class 6 wind power. As in the case of Mount Washington, wind measurements on Whiteface Mountain indicate higher than class 6 power because of local acceleration effects. Mean upper-air wind speeds appear to be about the same over the Adirondack Mountains as they are over the mountains of northern New Hampshire and Vermont.
Class 3 and higher wind power is estimated for exposed hilltops, ridge crests, and mountain summits in Pennsylvania, southern New York, and northwestern New Jersey. The highest wind power, class 5, exists in southeastern New York on the higher summits of the Catskill Mountains. Other major mountains or mountain ranges included in this resource area are Bald Eagle Mountain, North Mountain, the Pocono Mountains, and the Allegheny Mountains. The wind power in much of this area increases to class 5 and 6 in the winter.
Annual average wind power of class 3 or 4 is found along the coastal areas of both Lake Erie and Lake Ontario as the smooth, overwater fetch allows strong near-surface winds to develop. Class 5 is estimated to exist in the central part of both lakes. Existing data indicate that class 3 wind power may extend 30 to 40 km (20 to 25 mi) inland from the eastern shore of Lake Ontario (Pickering et al. 1980).
The East Central region consists of Delaware, Kentucky, Maryland, North Carolina, Tennessee, Virginia, and West Virginia. North Carolina, Virginia, and Maryland account for nearly 60% of the region's population, of which most reside in the Mid-Atlantic Lowlands. The major cities, rivers, mountain ranges, and national parks are shown in Map 3-27.
The region's topography varies from rolling hills in the west to forested mountain ridges in the central portion to relatively flat coastal plains in the east. The mountain ridges are generally oriented in a northeast-southwest direction.
Areas of class 3 annual average wind power are found along exposed coastal areas from Delaware southward to Cape Lookout, North Carolina, including much of Delaware Bay, Chesapeake Bay, and Pamlico Sound. Seasonal average wind power along the coastal areas ranges from class 4 in the winter and spring to class 2 in the summer. Class 3 to 6 annual average wind resource is estimated for exposed mountain summits and ridge crests of the Appalachians. Over 4 years' data collected at a DOE wind turbine site on a 1,347 m (4419 ft) mountain summit near Boone, North Carolina, indicated class 4 annual average wind power at 50 m (164 ft). Seasonal average wind power ranged from a maximum of class 7 in winter to a minimum of class 2 in summer at this site.
Aside from the coastal areas and exposed mountains and ridges of the Appalachians, there is little wind energy potential in the remainder of the East Central region for current wind turbine applications (Brode et al. 1980).
Major areas of wind resource in the East Central region are described below. Maps of annual average wind power are presented in Maps 3-28 through 3-33 for Delaware and Maryland (displayed on one map), Kentucky, North Carolina, Tennessee, Virginia, and West Virginia.
The annual average wind power for exposed coastal areas of Delaware, Maryland, Virginia, and North Carolina is estimated to be class 3. South of Cape Lookout, North Carolina, wind power decreases to class 2. There is a steep gradient in the estimated wind power within several kilometers of the coastline because of the abrupt change in surface roughness between the land and open water, even though relatively flat, smooth plains extend far inland along the entire length of the East Central region's coastline. While most of the coastline is oriented such that the prevailing wind direction (from the southwest across most of the region) is offshore, there is considerable variation in the orientation from one area to another.
Winter and spring are the seasons of maximum power for the coastal areas of the region, with class 4 wind power from Cape Hatteras northward. In summer, wind power decreases to a minimum of class 1 and 2 along the coastal areas.
Much of the Chesapeake and Delaware bays are estimated to have class 3 wind power. Areas of highest wind resource are expected where there is a large fetch over open water for the prevailing strong winds, which come from the west through north directions. The complexity of the Chesapeake Bay shoreline, with its many islands and inlets, suggests a high variability of wind power in this area.
Class 3 or higher wind power is estimated for exposed mountain summits and ridge crests in western North Carolina, eastern Tennessee, eastern West Virginia, western Maryland, and portions of Virginia. Average wind speeds may vary considerably from one ridge-crest site to another and are primarily influenced by the height and slope of the ridge, orientation to the prevailing winds, and the proximity and relative height of other mountains and ridges. Most of the ridges in Virginia, West Virginia, and western Maryland are oriented perpendicular to the prevailing westerly winds. As a result, the higher ridges may experience wind power that is considerably enhanced by a venturi speed-up effect - wind flows are compressed as they are forced over the ridges. Winter is the season of maximum wind power over the mountain summits and ridge crests of the East Central region because mean upper-air wind speeds are highest during this season. In contrast to valley and plain locations, the daily maximum wind speed for mountain summits and ridge crests generally occurs at night; this situation occurs because the frictional boundary layer is more shallow as a result of the absence of solar heating and associated vertical mixing.
The Southeast region consists of Alabama, Florida, Georgia, Mississippi, and South Carolina. The region's total population in 1980 of 24,746,000 represents approximately one-tenth of the nation's population. Nearly three-quarters of the people in the Southeast live on the East Coast from South Carolina to Florida. The major cities, rivers, mountain ranges, and geographical features of the Southeast are shown in Map 3-34.
With the exception of the north-central portion of the Southeast region and a few scattered areas, the topography is relatively low and flat. Roughly 41% of the topography in the Southeast is irregular plains, 41% is flat and smooth plains, and only 18% is tableland, hills, and low mountains, which lie in the north-central part of the Southeast. The northern half of Alabama, the northern part of Georgia, and the far northwestern corner of South Carolina have the most complex terrain of the region, with tablelands, hills, and low mountains.
There is little wind energy potential in the Southeast region for existing wind turbine applications (Zabransky et al. 1981). Even along coastal areas, existing data from exposed sites indicate at best only class 2 at 50 m (164 ft) above ground. The only places in the Southeast region estimated to have 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, as described below. Maps of annual average wind power are presented in Maps 3-35 through 3-39 for Alabama, Florida, Georgia, Mississippi, and South Carolina.
The exposed ridge crests and mountaintops of the southern Appalachians in extreme northwestern South Carolina and northeastern Georgia have annual average wind power densities of class 3 to class 5. This area is highly confined and represents an extremely small percentage of exposed land in the Southeast region.
The South Central region, consisting of Arkansas, Kansas, Louisiana, Missouri, Oklahoma, and Texas, is about the same size as Alaska and equal to one-fifth the area of the 48 contiguous states. Texas has 45% of the area and slightly more than 45% of the region's population. Over 40% of the people in the South Central region live in the six metropolitan areas that have over one million inhabitants each. In order of decreasing population, these are Dallas-Fort Worth, Texas; Houston, Texas; St. Louis, Missouri; Kansas City, Kansas; Kansas City, Missouri; New Orleans, Louisiana; and San Antonio, Texas. The major cities, rivers, mountains, and national parks of the South Central region are shown in Map 3-40.
The South Central region extends from the interior plains to the coastal plains with a few interior highlands in the east-central part. The Mississippi River makes up most of the eastern boundary of the region as it flows south to the Gulf of Mexico. The only major portions of the region that are mountainous are the western tip of Texas, and parts of Arkansas, Missouri, and extreme eastern Oklahoma.
A substantial portion of the South Central region has class 3 or higher annual average wind power. The most extensive area of wind resource includes most of Kansas, Oklahoma, and northwestern Texas, where a large fraction of the land area is well exposed to power-producing winds. Other areas of significant wind resource in the region include the Texas coast and exposed hilltops, ridge crests, and mountain summits in parts of southern Missouri, western Arkansas, eastern Oklahoma, and extreme western Texas.
Since the completion of the regional wind energy atlas (Edwards et al. 1981), many new sites have been instrumented to measure the wind resource throughout much of Kansas, western Oklahoma, and northwestern Texas. Wind measurements at levels up to 46 and 50 m (150 to 164 ft) above ground have been taken at 16 new sites in this area. Four of these were sites instrumented for the DOE candidate site program. These were located near Amarillo, Texas; Meade and Russell, Kansas; and Fort Sill, Oklahoma. Some other organizations involved in wind measurement activities in this area included the Alternative Energy Institute, Kansas State University, and Wichita State University. The composite analysis of the new wind data obtained for this area resulted in some significant revisions in analysis from the previous regional assessment.
For example, the class 5 area previously shown over the southern High Plains from north of Amarillo, Texas, to extreme southwestern Kansas, has been revised to class 4 and 3, based on the wind measurements taken at or near 50 m (164 ft) at five new sites in this area. In eastern Kansas, an area previously assigned class 3 has been up-graded to class 4, reflecting exposed areas in the Flint Hills where several new sites indicate class 4 (and possibly class 5) at 50 m (164 ft) above ground. In the Texas coastal area, the class 4 area was revised to class 3, based on new data at 30 to 60 m (98 to 164 ft) above ground from two sites and a re-analysis of the coastal data previously used in the regional assessment. The seasonal analyses in the Texas coastal area (presented on the national-scale maps) have been revised to show an on-shore maximum in the wind resource in the spring and summer. During these seasons, the wind resource is estimated to be greater along the inner coastal areas than along the offshore islands, such as Padre Island. Additional data are needed, especially at heights to 50 m (164 ft), to provide a more reliable estimate of the extent of this onshore maximum in the wind resource.
Major areas of wind resource in the South Central region are described below. Maps of annual average wind power are presented in Maps 3-41 through 3-47 for Arkansas, Kansas, Louisiana, Missouri, Oklahoma, and Texas. (Texas is displayed in two maps, one for West Texas and one for East Texas.)
Exposed areas of the Great Plains encompassing a large area of northwestern Texas, Oklahoma, and Kansas have class 3 and 4 annual average wind power. The most extensive area of class 4 power extends from the Texas Panhandle to northwestern Oklahoma and south-central Kansas. In this area, the wind power is estimated to approach class 5 over some of the uplands and hills. However, over much of the Great Plains, local variations in terrain elevations and exposure cause variability in the wind resource, such that the wind resource may vary from class 2 over lowlands and river valleys to class 4 (and possibly class 5) over exposed uplands and hilltops.
Seasonal variations in the wind resource at 50 m (164 ft) over the area from the Texas Panhandle to south-central Kansas are not as large as indicated in the previous regional assessment. Spring is the season of maximum wind power, with class 5; however, an area of class 4 appears in each of the remaining three seasons. At the Amarillo DOE site, 5 years' data indicated that summer was the season of second highest wind power at 50 m or 164 ft (with a strong class 4), although summer was the season of lowest wind power at 10 m or 33 ft (with class 3). Strong nocturnal wind shear, especially prevalent during the summer, results in a higher wind power class at 50 m (164 ft) in the summer than would be indicated by 10-m (33 ft) data. Mean wind speeds at 50 m (164 ft) are greater at night than during the day.
The Flint Hills extend north to south through eastern Kansas. Wind measurements at heights to 50 m (164 ft) above ground at exposed sites in the Flint Hills indicate class 4 annual average wind power, and possibly class 5 over well-exposed areas of the southern Flint Hills. As it does over exposed uplands in the Great Plains, strong nocturnal shear occurs over elevated areas of the Flint Hills, such that mean wind speeds at 50 m (164 ft) are greater at night than during the day.
The wind resource at 50 m (164 ft) remains high throughout the four seasons; the seasonal average wind power is estimated to be a strong class 5 in the spring and class 4 in the other three seasons. Additional data are needed to verify the seasonal nature of the wind resource, because less than two years' data were available for this area at the time of this analysis.
Over most of the remainder of eastern Kansas, class 3 is estimated for the open plains and exposed uplands and hilltops.
Limited data in the vicinity of the Wichita Mountains in southwestern Oklahoma indicate at least class 4 or higher wind power. Local, strong acceleration of the wind speeds is estimated to occur around the eastern and western ends of the Wichita Mountains, as a result of the prevailing strong northerly and southerly winds over this region. Limited data from a DOE-installed tower on the plains near the eastern end of the Wichita Mountains indicate very good wind energy potential (possibly class 6), although additional data are needed to verify the magnitude and nature of the wind resource in this area.
The Texas coastal area from Galveston south to the Mexican border is estimated to have class 3 annual average wind power. This wind resource extends up to 30 to 60 km (20 to 40 mi) inland. The wind resource along the inner coastal area (just onshore and to 30 km inland) may be slightly greater than that over the offshore islands, such as Padre Island. New site data from the offshore islands indicate class 2 to class 3 wind power at 50 m (164 ft), rather than the class 4 previously assigned in the regional atlas. Data at 60 m (197 ft) from the inner coastal area indicate class 3 annual average wind power. A reanalysis of the near-surface data from airfields in the inner coastal area also indicates that class 3, rather than class 4, is more appropriate to this area.
Seasonally, the inner coastal area is estimated to have greater wind power in spring and summer than the offshore islands. Existing data indicate a spring maximum of class 4 along the inner coastal area south of Matagorda and a winter maximum along the offshore islands and the coastal fringes northward to Galveston.
Upper-air wind data have been used to estimate class 3 and 4 wind power at exposed areas in the Ouachita and Boston mountains, which extend from Arkansas westward into Oklahoma. Although the wind power map implies that nearly one-fourth of Arkansas has class 3 and 4 wind power, the exposed mountain summits and ridge crests account for only 3% of Arkansas land area. No surface data from mountain summits or ridge crests in these areas were available to verify this wind resource.
The Ozark Plateau is an area of forested hills and low mountains and ridges in southern Missouri and northwestern Arkansas. Exposed hilltops, ridge crests, and mountain summits of the Ozark Plateau are estimated to have class 3 annual average wind power, although no data were available from a well-exposed site to verify this wind resource. However, wind data from the Springfield, Missouri, airport, which is located on an upland near a crest in the Ozark Plateau but at an elevation approximately 60 m (197 ft) lower than the crest, indicates class 2 annual average wind resource. Thus, well-exposed sites at the highest elevations on the Ozark Plateau are expected to have at least class 3 wind power at 50 m (164 ft).
Seasonally, wind power over the Ozark Plateau is estimated to reach a maximum of class 4 in winter and spring, decreasing to a minimum of class 2 in the summer.
The ridge crests and mountaintops of the Guadalupe and Davis mountains in the basin and range region of the Rocky Mountain extensions in southwestern Texas are estimated to have up to class 6 wind power. Surface data taken at Guadalupe Pass confirms this and suggests that there is some funneling in the passes and valleys.
The Southern Rocky Mountain region consists of Arizona, Colorado, New Mexico and Utah. Over 60% of the region's people reside in the metropolitan areas of Denver, Colorado; Phoenix, Arizona; Salt Lake City, Utah; Tucson, Arizona; Albuquerque, New Mexico; and Colorado Springs, Colorado. The remainder of the region's people live in agricultural, industrial, and resort communities distributed throughout the area. The major cities, rivers, lakes, mountain ranges, and geographical features of the Southern Rocky Mountain region are shown in Map 3-48.
Topography varies dramatically throughout the Southern Rocky Mountain region. The region is dissected by the continental divide, which extends through central Colorado and western New Mexico, and is composed of five basic topographic areas: the high plains, the Rocky Mountains, the Colorado Plateau, the Great Basin, and the southwestern desert. The high plains area occupies roughly the eastern one-third of Colorado and New Mexico. The Rocky Mountains, which extend from north to south through Colorado and New Mexico, are composed of numerous ranges that attain elevations in excess of 4,250 m (13,944 ft). The Colorado Plateau occupies the area surrounding the Four Corners area. The Great Basin of western Utah is composed of desert basins, playas, and small mountain ranges. The southwestern desert includes the desert areas of southern New Mexico and southern Arizona.
Areas of class 3 or higher wind resource can be found throughout the Southern Rocky Mountain region. The most extensive area of wind resource is found over the high plains and uplands of eastern Colorado and eastern New Mexico. Over this area, the annual average wind resource is mostly class 3 and 4, but can be higher on well-exposed hilltops that are found over portions of the high plains region. Mountain summits and ridge crests estimated to have class 3 or higher wind resource exist throughout the Southern Rocky Mountain region. Higher mountain ranges are estimated to have at least class 6 wind power, but many of these may not be suitable because of the ruggedness of the terrain and the potential for extreme wind and icing conditions. Two valley wind corridors have been identified that are estimated to have at least class 3 wind resource. One of these wind corridors is in the vicinity of Milford, Utah, and the other is in the vicinity of Santa Fe, New Mexico.
These major areas of wind resource in the Southern Rocky Mountain region are described below. Maps of annual average wind power are presented in Maps 3-49 through 3-52 for Arizona, Colorado, New Mexico, and Utah.
Class 3 and 4 annual average wind power is found on the high plains and uplands of eastern Colorado and eastern New Mexico. Strong northerly and southerly winds in this area are usually associated with the intense surface pressure gradients that are prevalent during the winter and spring. Plains areas farther west that are within the sheltering influence of the Rocky Mountains and river drainages generally have less wind power.
Buttes, hilltops, and other types of elevated summits are scattered throughout parts of the high plains, especially in northeastern New Mexico and southeastern Colorado. Well-exposed summits and hilltops, where there is terrain-induced acceleration of the wind, may have class 5 or higher wind resource. For example, a DOE site on a hilltop near Tucumcari in northeastern New Mexico indicated class 5 power at 50 m (164 ft) over a 2-year period. Another DOE site located on open plains near Clayton in northeastern New Mexico had class 3 wind power at 50 m (164 ft), based on 5 years' data. The class 5 power previously estimated for the plains area around Clayton in the regional atlas (Andersen et al. 1981) appears too high. These previous estimates were primarily based on near-surface, airfield data of unknown quality from the 1940s and early 1950s.
New site data throughout northeastern Colorado indicate an extensive area with class 4 annual average wind power. This is an upland region between the South Platte River to the north and the Arkansas River to the south. Wind power is considerably lower in the river plains and valleys than on the uplands.
Seasonal average wind power over the upland plains of eastern Colorado and New Mexico ranges from a maximum of class 4 and 5 in spring to a minimum of class 2 and 3 in summer.
North of the South Platte River in northeastern Colorado, the elevation increases northward to the high plains of southeastern Wyoming and western Nebraska. The proximity of the sheltered South Platte River valley to the southern Wyoming wind corridor creates a steep gradient of annual average wind speed, and hence wind power, between these areas. The strong prevailing westerly winds, which blow uninterrupted through the large gap in the Continental Divide in southern Wyoming, appear to extend into northeastern Colorado and western Nebraska.
Class 4 to 6 annual average wind power is found in this part of Colorado south of the Wyoming and Nebraska borders. New site data indicate that class 4 wind power extends eastward to Peetz, Colorado. Class 6 wind power is found on the Laramie Mountains divide, a broad upland which extends southward just into Colorado.
Strongest winds in this area occur during the winter as a result of intense pressure gradients between the low-pressure systems moving east across the northern tier of states, and the semi-permanent high-pressure system that occupies the Great Basin. Prevailing wind directions during strongest winds are generally westerly and northwesterly.
Class 3 annual average wind power is found in the valley corridor in the vicinity of Milford, Utah. Strong southwesterly winds frequently occur over this area, especially during the spring when the wind resource averages class 4. Higher wind resource may exist in areas where the terrain causes even stronger channeling of the winds. Data are scarce in this region of southwestern Utah, and the geographical extent of this wind resource area is not well known.
Class 3 annual average wind power is estimated for the Rio Grande Valley corridor in the vicinity of Santa Fe, New Mexico. Wind speeds are enhanced as air flowing up or down the Rio Grande Valley is channeled and accelerated through a broad gap between two large mountain ranges. Wind resource reaches a maximum in the spring, when it averages class 4. Higher wind resource may exist in areas where the terrain causes even stronger channeling of the winds.
Class 3 or higher annual average wind power is estimated for exposed mountain summits and ridge crests throughout the Southern Rocky Mountain region. Class 6 is estimated for the higher mountain ranges in parts of Colorado, New Mexico, and Utah. However, many of these higher mountain ranges may not be suitable for wind turbine applications because of extreme icing, damaging winds, and inaccessibility, especially during the winter.
Average wind speeds may vary significantly from one ridge crest site to another and are primarily influenced by the height and slope of the ridge, orientation to prevailing winds, and the proximity of other mountains and ridges. High wind resource may exist in mountain passes or saddles where prevailing strong winds are funneled. A DOE site at San Augustin Pass, located about 30 km (20 mi) northeast of Las Cruces in the San Andreas Mountains of southern New Mexico, indicated class 6 annual average wind power at 50 m (164 ft) with a strong class 7 in the winter and spring.
Winter is estimated to be the season of maximum wind power over mountain summits and ridge crests in Utah, Colorado, northern New Mexico, and northern Arizona, because mean upper-air wind speeds are highest over these areas during this season. However, on the exposed mountainous areas of southern Arizona and southern New Mexico, winter and spring power appear about equal and are the seasons of maximum wind power.
The Southwest region consists of California and Nevada. (To facilitate the presentation of the wind resource analysis, we have divided California along 37°N into northern and southern California). Nearly three-quarters of the inhabitants of the region live in coastal California, where the region's three large metropolitan areasthe San Francisco Bay area, Los Angeles Basin and San Diegoare located. Major cities, rivers, mountain ranges, and national parks are shown in Map 3-53.
There is a large variety of topography throughout the Southwest. California has many mountain ranges, several of which extend above 3,000 m (10,000 ft) in elevation. It also has some very large flat areas, notably the Central Valley, which is composed of both the Sacramento and San Joaquin valleys and is over 700 km (400 mi) long. The California desert is mostly composed of isolated peaks and ranges dotting an undulating basin. Nevada is composed almost exclusively of basin and range country; there is a series of parallel valleys alternating with steep mountain ranges. Some broad upland plains are found in northern Nevada near the Oregon and Idaho borders.
Considerable wind energy development has occurred in California; more wind turbines have been sited in California than in any other region of the United States. Extensive wind resource assessments have been conducted throughout California by the California Energy Commission (CEC) and various other organizations. The CEC has assimilated a wind resource data base on California that was utilized in verifying or updating this assessment. The DOE has sponsored wind measurement programs at three sites in California - Point Arena, San Gorgonio Pass, and Pacheco Pass - and one site in Nevada - Wells (located on a mountain ridge in northeastern Nevada about 65 km (40 mi) northeast of Elko).
Areas of class 3 and higher wind resource are dispersed throughout the Southwest region. The most notable areas where most of the wind energy development has been occurring are the coastal and inland passes through which cooler marine air is funneled to the warmer, drier valleys in the interior. At least six major passes, or wind corridors, with high wind resource occur throughout central and southern California. These are the Carquinez Straits, Altamont Pass, and Pacheco Pass in north central California and Tehachapi Pass, San Gorgonio Pass, and the Sierra Pelona in southern California. The annual average wind resource can reach class 6 or higher at well-exposed sites in these wind corridors. High wind resource is also found in some of the southeastern California desert corridors, such as the western part of the Antelope Valley and the Barstow-Daggett area.
Other areas of class 3 or greater wind resource in the region are the outer Channel Islands and exposed coastal areas north of Point Conception, and many of the exposed mountain summits and ridge crests that are located throughout the Southwest region.
Major areas of wind resource in the Southwest region are described below in greater detail. Maps of annual average wind power are presented in Maps 3-54 through 3-56 for California and Nevada. (California is displayed in two maps, one for northern California and one for southern California.)
The annual average wind power for exposed coastal areas of California north of Point Conception is estimated to be largely class 3, except for class 4 around Cape Mendocino. Because the prevailing wind direction is northwest during spring and summer and between the winter storms, and because much of the California coastline is oriented northwest to southeast, coastal areas that protrude into the flow experience the highest wind power. They also protrude into the southerly or southeasterly flow, which dominates during winter storms. However, because the rest of the shoreline is concave between these areas and thereby out of the strong flow, it experiences a markedly lower wind resource. The abrupt increase in surface roughness inland from the coastline, because of vegetation and topography, further slows the wind.
Almost 5 years of new site data from a DOE-installed tower at Point Arena indicated class 3 wind power at 50 m (164 ft). This site, which is well exposed to prevailing strong winds, is considered largely representative of exposed coastal areas of central California. Previous estimates of class 5 for much of this coastal area, which were based primarily on very limited surface data and offshore marine data (ship observations), appear too high (Simon et al. 1980). However, specific sites that experience local terrain-induced acceleration of the winds may exist that have class 5 or greater wind power. For example, limited data from a site on the exposed ridge crest at an elevation of about 450 m (1,476 ft) on Cape Mendocino indicate class 6 annual average wind power. In such areas of complex terrain, considerable spatial variability in the wind resource can be expected.
The southern California coastline south of Point Conception has very little wind power, because it is sheltered from the northwest winds by the Transverse Ranges. The outer Channel Islands (San Miguel, Santa Rosa, and San Nicolas) of southern California are far enough west to escape the sheltering that affects the rest of the southern California coastal area, and they are estimated to have class 3 to class 4 wind power.
Spring is the season of maximum wind power at exposed coastal areas from Point Arena south to Point Conception and the outer Channel Islands, where exposed areas average class 4 and 5 wind power. Over these areas, class 3 or greater wind resource is experienced in every season except autumn.
From Cape Mendocino northward, wind power is about equal in winter and spring, because strong winds associated with winter storms are more frequent along the northern California coast than the central and southern coast. Exposed areas on Cape Mendocino are estimated to have class 3 or greater wind power in every season.
From spring through summer, the strong surface pressure gradients created by the cold water and warm interior force marine air through the gaps in the coastal mountains into the interior. This sea breeze is funneled in some cases by the topography. Where this happens, very strong and persistent winds are likely to occur. The Carquinez Straits, Altamont Pass, Pacheco Pass, San Gorgonio Pass, and the Sierra Pelona fall into this category. All have high annual average wind power and a spring or summer seasonal maximum. Although not a true gap, the Sierra Pelona region, which is located north of Los Angeles and south of Antelope Valley, is a long stretch of mountains that are lower than the mountain ranges on either side of it, and the marine air flows through this low area on its way to the Mojave Desert. The windiest areas are near the eastern end of each pass and the highest ridges of the Sierra Pelona.
There are four areas of the Coast Range that have wind power of class 5 or better. Two areas, the higher mountains of northwestern California (2,000 to 3,000 m or 6,562 to 9,843 ft) and the San Gabriel Mountains east of Los Angeles (3,000 m or 9,843 ft), are strongly affected by the upper-air winds, and the wind resource therefore shows a strong winter maximum and summer minimum. They are 500 to 1,000 m (1,640 to 3,280 ft) higher than the surrounding mountains, so they are well-exposed to the free-air winds. The Vaca Mountains (about 900 m or 3,000 ft), west of Sacramento, and the Laguna Mountains (about 2,000 m or 6,562 ft), east of San Diego, while higher than surrounding terrain and influenced by the upper-air flow, are also influenced by modified sea-breeze winds of spring and summer. Hence, their season of maximum wind power is winter, but the sea-breeze winds produce almost as much power in the spring, and the summer wind resource is not as low as in the other two areas. This sea-breeze circulation further complicates the wind regime of the Vaca Mountains. The prevailing strong winds of the other areas are generally westerly. This is true for the Vaca Mountains as well, except that they experience a definite wind shift from westerly during the day to northeasterly at night during the spring and summer.
The large mountain ranges of the Southwest have a high wind energy resource. The Cascades, Sierra Nevada, Tehachapis, and the ranges of Nevada are well exposed to the upper-air winds and therefore experience a winter maximum wind power. Where the mountain ranges and ridgelines are oriented perpendicular to the free-air flow, these winds may be further enhanced. Additionally, these ranges are large enough to separate adjacent air basins. The unequal heating of these basins during spring and summer produces air flow over some of these barriers. This flow results in wind speeds that are higher than those that would be found if only the upper-air winds produced the wind resource of the mountains.
East of the Coast Range in southern California, low-elevation wind corridors exist that have class 3 or greater wind resource. One notable wind corridor is Tehachapi Pass, near Mojave, where winds are funneled from the San Joaquin Valley into the Mojave Desert. Areas of class 6 annual average wind resource are indicated by new site data in the Tehachapi Pass vicinity. Spring and summer are the seasons of highest wind resource.
The western part of the Antelope Valley is another area of high resource potential. New site data in the extreme west end of the Antelope Valley indicate class 6 wind resource. Class 3 or higher wind resource is estimated to exist over much of the southern and western parts of the Antelope Valley. Spring and summer are seasons of maximum wind resource.
In the vicinity of Daggett (just east of Barstow), another wind corridor exists where desert winds are channeled between the Calico and Rodman Mountains. Over 20 years of data from the Daggett Airport show class 3 to 4 annual average wind power. New site data by the California Energy Commission also indicate class 3 to 4 wind power in this area. Maximum wind resource occurs in the spring and summer.
Desert conditions are found in most of southeastern California and the valleys of southern Nevada. Intense heating will often generate strong afternoon winds that persist into the evening. The lack of vegetation and the preponderance of broad open valleys in California and narrower valleys in Nevada (which may funnel the winds) allow wind storms to sweep the desert with little abatement. In spite of these mechanisms, most desert floors have only class 1 or 2 power, as wind speeds decrease during the night and morning hours. The numerous mountain summits and ridgelines, which are less subject to stable layers that develop in the valley floors, may experience wind power of class 3 and higher. The lower mountains and ridges of southern California and southern Nevada, being more strongly affected by the thermal circulation, experience a spring maximum.
Alaska covers an area of 1,518,776 km2 (586,400 mi2). Because of the state's large size, in the Alaska wind energy resource assessment (Wise et al. 1981) the state was divided into four subregions: northern,southeastern, south-central, and southwestern. The state population in 1980was 402,000. More than 40% of Alaska's population lives in the metropolitanarea of Anchorage, in the south-central subregion. The major cities, towns, villages, rivers, mountain ranges, and national parks are shown in Map 3-57.
The topography of Alaska varies from subregion to subregion. A large portion of the land is mountainous; the Brooks Range is in the northern subregion, the Alaska Range is in the south-central and southwestern subregions, and the Coast and St. Elias mountains are in the southeastern subregion. Flat coastal plains, such as those along the Arctic coast and Yukon-Kuskokwim Delta (in the northern and southcentral subregions, respectively) are also prominent features. Flat alluvial plains are found in the river valleys, such as the Yukon River valley in the southeast portion of the northern subregion. Up-land plains are found throughout the state.
In Alaska, high wind resource occurs over the Aleutian Islands and the Alaska Peninsula, most coastal areas of northern and western Alaska, offshore islands of the Bering Sea and Gulf of Alaska, and over mountainous areas in northern, southern, and southeastern Alaska. The largest areas of class 7 wind power in the United States are located in Alaskadata from some of the Aleutian Islands indicate an annual average wind power over 1000 W/m2 at 10 m, which corresponds to about 2000 W/m2 at 50 m.
Major areas of wind resource in Alaska are described below. Maps of annual average wind power are presented for the four subregions in Maps 3-58 through 3-61.
The annual average wind power for exposed coastal and offshore areas is estimated to be at least class 5. Coastal areas near Barter Island, Point Lay, and Cape Lisburne show class 7. Even though much of the area north of the Brooks Range is of low relief, wind power drops off rapidly with distance from the coast as shown by data from Sagwon and Umiat. On the eastern Beaufort coast, an area with wind power of class 4 or higher appears to extend from the coast southward to the crests of the Brooks Range. Along the Chukchi Sea coast, wind power of class 5 to 7 is probably confined to near the coast, although there are no data available inland to corroborate this assumption.
Islands in the Bering Sea, such as the Pribilofs, St. Lawrence, St. Matthew, and Nunivak, all show annual wind powers of class 7 except in the vicinity of Savoonga on St. Lawrence Island, which has class 6. Along the coast from the Alaska Peninsula northward, wind power of class 5 or higher (with class 7 in exposed areas like the west end of the Seward Peninsula and the Cape Romanzof area) is shown. Wind power of class 5 or more extends eastward for 150 km (100 mi) in the Yukon-Kuskokwim Delta area, as shown by Bethel data.
The Alaska Peninsula west of 162°W shows annual wind power class 7 at all locations except those shielded somewhat by local terrain. The whole peninsula has class 5 or higher power. This area is along a major storm track from eastern Asia to North America. Storms generally move from west to east. Some storms also move northward through the Bering Sea, especially during the summer months. Amchitka and Asi Tanaga in the western Aleutians show mean annual wind power of over class 7 (1,000 W/m2). Winter is the season of maximum wind power throughout the area.
The area from Iliamna Lake to Kamishak Bay across Cook Inlet to the Barren Islands is a corridor for strong winds. This is reflected at Bruin Bay, which shows an average annual wind power of over 1,300 W/m2. Subjective comments from mariners indicate that this lower Cook Inlet area can be very windy. Bruin Bay data and an examination of weather records from two drilling rigs operating in the area confirm this impression. There are no other permanent stations besides Bruin Bay that show this wind resource.
Exposed areas of the entire Gulf of Alaska coast should experience mean annual wind power of class 3 or higher. Offshore data from Middleton Island indicate class 7 wind power. Shore data such as Cape Spencer, Cape Decision, Cape Hinchinbrook, and North Dutch Island reflect class 5 or higher power. Data from more sheltered locations, such as Cordova, Sitka, and Yakutat do not reflect these wind power classes. Most of this coastline is rugged and heavily wooded, so wind power estimates are very site-specific.
At least class 3 or higher wind power is estimated for mountain summits and ridge crests in the Alaska Range, the Coast Mountains in southeastern Alaska, and portions of the Brooks Range. The map analyses represent the lower limits of the wind power resource for exposed areas. Wind speeds can vary significantly from one ridge crest to another as a result of the orientation to the prevailing slope of the ridge and its closeness to other ridgelines. Winter is the season for highest wind speed and power at mountain summits and ridge crests.
The Hawaii and Pacific Islands region differs significantly from the mainland regions. Though millions of square miles of ocean are included, land area is small. The state of Hawaii has 16,710 km2 (6,450 mi2), and more than 2,200 Pacific Islands affiliated with the United States have a total land area of 2,621 km2 (1,012 mi2). A map of the Hawaiian island chain is given in Map 3-62. The principal Pacific Islands and island groups described in this atlas are Guam, Wake, Johnston, and Midway Islands; and the northern Marianas, Carolines, Marshalls, and American Samoa. A map of the Pacific Islands is given in Map 3-63.
The major Hawaiian Islands (Kauai southeastward to Hawaii) are the peaks of submarine volcanoes. Local relief exceeds 900 m (3000 ft) on most of the major islands. Fifty percent of the land area lies above 600 m (2,000 ft) MSL elevation and nearly 50% lies within 8 km (5 miles) of the coastline.
The state of Hawaii had a population in 1980 of 965,000. The island of Hawaii comprises nearly two-thirds of the state's land area. Over 80% of the residents in the state live on the island of Oahu; this island consumes 90% of Hawaii's electric power.
The Pacific Islands are of two types: mountainous islands and atolls. The former, which are less than 1,000 m (3280 ft) elevation, include the Northern Marianas, Guam, American Samoa, and several of the Carolines. Most of the islands are atolls, which may not rise more than 5 m (17 ft) above the ocean.
The climate in the Pacific Islands is tropical. The Carolines mostly lie within the area of the near-equatorial convergence. Within this region, weather is dominated by light winds and humid, showery conditions. The eastern islandsJohnston, Midway, Wake, and the Marshallslie under the influence of brisk trade winds generated by the Pacific anticyclone. The trades weaken slightly in the western Pacific, though migratory anticyclones during winter provide brisk northeasterlies.
Samoa, in the southern hemisphere, experiences brisk trade winds during winter (June-August in the southern hemisphere). In summer, a monsoonal trough develops eastward from Australia, causing weak winds interrupted by tropical cyclones.
Tropical storms are major components of the climate of the Pacific Islands. Guam has been hit by some of the most devastating typhoons on record. Tropical storms are primarily late summer and early fall features, but have occurred in all months.
Local influences on climate vary with island type. Atolls exert little influence on the prevailing air streams. Diurnal variations on atolls match those observed for the open oceans. Mountainous islands, especially in areas of light synoptic winds such as at Ponape, produce significant local effects on cloudiness and precipitation.
Interactions between prevailing trade winds and island topography determine the distribution of wind power. On all major islands trades accelerate over coastal regions, especially at the corners. The best examples are regions of class 6 or higher wind power on Oahu, Kauai, Molokai, and Hawaii. The rampart-like mountain crests of Oahu enhance prevailing winds to class 6. On other islands, circular mountain shapes and extreme elevations prevent the type of wind acceleration observed on the Oahu ranges (Schroeder et al. 1981).
Annual average wind power in Kauai and Honolulu counties is presented in Map 3-64. The primary wind resources in Kauai County are on the southeastern and northeastern coasts of Kauai where trades accelerate around the island barrier. Broad areas of class 3 or higher wind power occur over the northern, southern, and eastern parts of Kanai, increasing to class 6 over the northeastern (Kilauea) and southeastern (Makahuena) points.
On Oahu (Honolulu County), the long Koolau mountain rampart and shorter Waianae Range enhance trades to class 6, although the rugged topography, watershed value, and turbulent air flows over these ranges may preclude practical application of wind power generation. The northeastern (Kahuku) and southeastern (Koko-head) tips of Oahu have areas of class 7 and broad areas of class 3 or higher. A class 3 and 4 area exists at Kaena Point on the island's northwestern tip, and class 3 areas exist along the southern coast west of Honolulu and southeastern coast north of Makapuu Point.
Maui County is made up of three principal islands: Molokai, Maui, and Lanai. A map of annual average wind power for Maui and Hawaii counties is given in Map 3-65.
Molokai is unique among the major Hawaiian Islands in that it lies almost parallel to the prevailing trades. Exposed areas on most of the island are estimated to have class 3 or above, and much of the northwestern quadrant is class 4 or above, becoming class 7 at Ilio Point. Eolian features are found in northwestern Molokai. A narrow belt of class 4 lies on the southeastern coast.
The primary wind resource on Maui lies in the central valley where trades accelerate between Haleakala and west Maui Volcano existing as class 5 and 6 near Maalaea Bay. Secondary power resources exist at the northern (class 3 and 4) and southeastern (class 3) tips.
Lanai lies partly in the wind shadow of western Maui. Nevertheless, deformed trees indicate that winds are slightly accelerated (class 4) over the northwestern third of Lanai. This area is exposed to winds funneling through the Pailolo Channel between Maui and Molokai. Exposed areas over the remainder of Lanai are estimated to have class 3 power.
Hawaii consists of five major mountains and the saddles between them. The tall volcanoes, Mauna Loa and Mauna Kea, provide a barrier to the trade winds, producing a stagnation which extends well upwind of Hilo. Trades diverted to the north of Mauna Kea accelerate through the Waimea saddle and over the Kohala Mountains, producing a significant area of class 7 wind power and a broad area of class 3 or higher wind power. A smaller area of high wind resource, up to class 7, exists at the south cape.
Wind power maps for the Pacific Islands are presented by island group - for Guam and the Marshalls (Map 3-66), the northern Marianas (Map 3-67), the Carolines and American Samoa (Map 3-68), and the isolated islands of Midway, Wake, and Johnston (Map 3-69). Except for Guam (the largest Pacific Island), wind power values are presented for the surrounding ocean areas; these estimates are based on ship wind data (Wyrtki and Meyers 1975) obtained over 6 years (1965 through 1970). The wind power estimates were calculated from mean wind speeds (averaged over 6 years) assuming a Rayleigh distribution of wind speeds.
Wind data from the Pacific Islands are sparse. Approximately half of the documented stations have questionable anemometer heights and exposures as a result of inadequate documentation. Wind power densities were available for some of the islands. Except for some of the small atolls, open-ocean wind power considerably exceeds island values. Apparently, well-exposed sites are rare in the Pacific Islands. Available site descriptions consistently mention adjacent stands of coconut palms.
Guam is the only Pacific island outside of the Hawaiian chain with more than one wind station. The island data indicate class 2 power, although ship wind data indicate class 5 to class 6 power in surrounding waters. Data from Andersen Air Force Base, on the plateau on what should be a windy island corner, indicate only class 2 power.
The Marshall Islands lie in a belt of strong ocean winds and possess the best wind power potential of the major Pacific Islands groups. Ship wind power densities reach class 7 in the northern Marshalls and class 4 in the south. With the exception of Enewetak and Kwajalein, island wind power densities differ drastically from the ship values.
The northern Marianas, which extend 700 km (435 mi) in a nearly north-south line, are volcanic peaks, some with considerable relief. Ship winds indicate power densities of class 5 to class 6 in surrounding waters, although available island data indicate class 2 and 3 power.
The Caroline group lies in a region of weaker ocean winds. The near-equatorial convergence migrating back and forth during the year accounts for weak winds, especially in the south. The islands lie well away from the major winter or summer trade wind belts. However, class 3 wind power potential appears to exist in the northern atolls such as Ulithi.
American Samoa consists of six mountainous islands. The main island, Tutuila, contains the only NCDC station, Pago Pago. Island data indicate little wind power potential, but ship winds indicate power densities of class 3 to class 4 in surrounding waters.
Midway, Wake, and Johnston Islands were grouped for convenience even though they are widely separated. Each is a low coral island with negligible relief and little vegetation. The data on Midway indicate only class 2 power. However, ship data show class 6 power for the ocean area. Thus, exposed sites on Midway may have higher power than that estimated from the island data. At Johnston Island, an atoll located 1,500 km (900 mi) south-southeast of Midway, brisk trade winds prevail throughout the year. Data from an apparently well-exposed station on Johnston Island indicate class 5 power, which is not significantly different from the class 6 power estimated for the ocean area. Wake Island is also an atoll, located north of the Marshall Islands. Like Johnston, data from an apparently well-exposed station on Wake Island indicate class 5 power, which is not significantly different from the class 6 power estimated for the ocean area.
The Puerto Rico/ Virgin Island region consists of the main island of Puerto Rico, its surrounding islands, the three main Virgin Islands (St. Thomas, St. Croix, and St. John), and several small islands in their immediate vicinity (see Map 3-70). This group of islands lies at the dividing point between the Greater and Lesser Antilles (which separate the Atlantic Ocean from the Caribbean Sea). The region totals slightly more than 9,100 km2 (3,570 mi2), which makes it a little smaller than the state of Connecticut, and has a population of approximately 3,000,000. Nearly 98% of the people in the region reside in Puerto Rico; about one-third of Puerto Rico's population lives in the metropolitan area of San Juan.
The topography throughout the region is generally hilly to mountainous. The main island of Puerto Rico is bounded on the north by a coastal plain averaging about 8 km (5 mi) in width. On the south coast the plain varies in width as mountains and hills intersect the coastline at several points. On the eastern end of the island a hilly valley extends inland to near Caguas. The coastal plain and valleys comprise 27% of Puerto Rico's total area. Hilly land surrounding the central mountain range occupies about 37% of the island's area. The interior of Puerto Rico consists of mountainous terrain of high local relief. This range of mountains, comprising 36% of the land area, runs east and west and is called the Cordillera Central. To the east of the main island are the hilly islands of Culebra and Vieques and to the west lies the island of Mona.
The three main Virgin IslandsSt. Thomas, St. Croix, and St. Johnare essentially mountains protruding from the sea. St. Croix, which has a valley sloping down from the center of the island to a broad coastal plain on the southern coast, is the only U.S. Virgin Island with a significant portion of flat land.
Exposed points and capes along the entire northern coast, and most of the eastern coast, of Puerto Rico appear to have class 3 annual wind power as do the windward (northeastern) coasts of Culebra, Vieques, and Mona (Map 3-71). Perhaps the best wind resource in Puerto Rico can be found on Cape San Juan, which extends approximately 5 km (3 mi) seaward from the mainland on the extreme northeastern corner of Puerto Rico (Wegley et al. 1981). The mean wind speed at Cape San Juan slightly exceeds that of the mean trade wind flow because of acceleration of the trades as they round the windward corner of the island. The wind at this location appears to have a slight winter maximum, but remains strong during all seasons of the year.
The highest peaks and ridge crests of the Cordillera Central, Sierra de Cayey, and Sierra de Luquillo are estimated to have class 3 annual wind power. Considering the complexity of the terrain here, there may be individual ridges, gaps, or other wind-enhancing terrain features that have class 4 wind power.
Several islands lie offshore near the northern coast of St. Thomas. The windward sides of these islands are estimated to have class 3 annual wind power. Exposed coastal sites on the northern coast as well as the exposed points at the southeast corner of St. Thomas also appear to have class 3 wind power (Map 3-72).
In central St. Thomas, the higher ridge and summits should have class 4 power. Some of the slightly lower peaks, particularly on the northeastern side of the island, are estimated to have class 3 annual wind power.
The central St. Croix ridge runs east-west the entire length of the island. The orientation of the island and its ridgeline suggests that the areas of highest wind power include the higher peaks as well as their northern and southern shoulders, where acceleration of the prevailing easterlies occurs as they flow around these topographical barriers.
The eastern tip of St. Croix points into the trade winds. This tip, the exposed points on the northern and southern coast, and Buck Island (near the northeastern coast) are all estimated to have class 3 annual average wind power.
A ridge of approximately 300 m (1,000 ft) MSL, paralleling the western shore of Coral Bay, appears to be the region of strongest winds (class 4 wind power) on St. John Island. The irregular coastline leaves many jutting points along the northeastern, eastern, and southeastern coasts. These points should have annual wind energy densities near class 3.
Chapter 4 References
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