Estimating the Hypothetical Wind Power Potential on Public Lands in Vermont Prepared for the Vermont Department of Public Servi
Total Page：16
File Type：pdf, Size：1020Kb
Estimating the Hypothetical Wind Power Potential on Public Lands in Vermont Prepared for The Vermont Department of Public Service By Vermont Environmental Research Associates, Inc. December 2003 Introduction 1 Purpose and Objectives 1 Methodology and Analyses 2 Section One: Mapping the Hypothetical Mean Annual Net Energy Production on Public Lands. 2 A. Assemble new wind resource maps for GIS processing. 2 B. Conversion from an area wind map to a linear map. 6 C. Identify hypothetical turbine strings on public lands. 9 D. Estimate the annual net energy production for each “turbine string” segment. 10 E. Screening for proximity to electric transmission lines. 11 Section Two: Evaluating Wind Development Compatibility with Public Land Use Objectives. 11 Results and Conclusions 14 Appendices Appendix 1: Windy State Parcels with Wind Development Compatibility Rating List 17 Appendix 2: U.S. Forest Service Management Areas and Wind Development Compatibility Categories List 20 Lists of Figures and Tables List of Figures Figure 1: The Vermont and New Hampshire region of the New England Resource Wind Map (50 meter wind speeds). 3 Figure 2: Relative size of Vermont land area to land owner types and Wind Class 4 and higher wind resource areas in Vermont. 5 Figure 3: Areal distribution of Vermont’s wind resources in standard Wind Classes at 50 meters above ground level. 6 Figure 4: Wind Class 4 and higher wind resource areas in Vermont Map. 7 Figure 5: Topographic map illustrating turbine strings drawn along ridgelines with Wind Class 4 or greater wind resource. 8 Figure 6: Public lands parcels transected by turbine strings. Map section illustrates “cut” turbine strings outside public land parcel boundaries. 9 Figure 7: Public lands classified by Wind Development Compatibility (WDC) categories together with turbine strings on those lands. 13 List of Tables Table 1: 50-Meter Wind Classes with associated mean wind speeds and the percent of land area in Vermont and public land type found in each wind class. 4 Table 2: Percentage of each public land area type by Wind Development Compatibility category. 14 Table 3: Relative amounts of hypothetical mean annual net wind energy production by Wind Development Compatibility category on three types of public lands. 15 Introduction Interest in utility-scale wind power development in Vermont has increased substantially in recent years. Previous wind resource assessments by the Vermont Department of Public Service (DPS), private wind development firms, the National Renewable Energy Laboratory (NREL), and the newly released “New England Wind Resource Map” all document that the wind resources along the higher elevations of the Green Mountain ridges are substantial. Many of these windy ridges include publicly owned or controlled land. Policy questions have been raised regarding the use of this public land for commercial wind power development. Some of the issues frequently raised involve learning how much of this resource is on public land, and what is the hypothetical energy production potential of these resources, considering general land use restrictions. The Vermont Department of Public Service commissioned this study in 2003 in recognition of the need for baseline data on the wind energy potential on public landsa on which answers to these questions can be developed and future policies considered. Purpose and Objectives The purpose of this study is to develop estimates of the hypothetical wind power potential on public lands in Vermont. It seeks to estimate how much electrical energy, in a relative sense, could potentially be generated by wind power according to certain wind classes and land use categories. It is hoped that the results of this work will provide baseline data to individuals and organizations responsible for planning and managing public lands and the state’s electrical energy supply and land use policies. Specifically the objectives of this study include: • Assembling publicly available wind resource and public lands data, in collaboration with wind experts and state and federal land management personnel; • Developing hypothetical estimates of the “Mean Annual Net Energy Production” potential on public lands; • Categorizing tracts of public land according to its compatibility for wind power development; and • Tabulating wind resource and land use data to determine the distribution of wind classes across broad categories of wind development compatibilities on public lands. a “Public land” as used in this study includes municipal lands, lands in which the state holds title or has a legal interest, and federal lands as included in the VGIS databases, as are more fully described on page 9 of this report. 1 Methodology and Analyses In this study, hypothetical wind energy production estimates for public lands were made considering the strength of the wind resource; the amount of available ridgeline along which wind turbines might be installed; the proximity to existing electric transmission infrastructure; and potential compatibility with using these ridgelines for wind power development. The methods and analyses used in performing this work are described in the following sections: Section One: Mapping the Hypothetical Mean Annual Net Energy Production on Public Lands. A. Assemble new wind resource maps for GIS processing. A digital version of the "New England Wind Resource Map" prepared by TrueWind Solutions, LLCb in 2003, was obtained for this study. This wind power map was generated at a spatial resolution 200 meter square grid cells using publicly available 1:250,000 scale digital elevation models and a proprietary advanced numerical atmospheric computer model ("Mesomap") developed by TrueWind Solutions, LLC. The model outputs wind statistics for each grid cell calculated by integrating existing surface and upper-air meteorological data with a cell’s elevation and other physiographic characteristics. The Vermont – New Hampshire portion of the New England Wind Resource Map is presented in Figure 1. The region’s windier resource areas (orange- red colors) are shown to be off the Atlantic coast and along the highest ridges of the Appalachian Mountains. The TrueWind Solutions’ computer mapping program is capable of producing wind statistics for specified heights above “effective ground level”c (see www.truewind.com for details and assumptions used in the preparation of this map). b The New England Wind Resource Map was produced in 2003 with joint funding from the Massachusetts Technology Collaborative Renewable Energy Trust, Connecticut Clean Energy Fund, and Northeast Utilities. It was validated by NREL and consulting meteorologists, including those familiar with Vermont’s long-term wind resources. Visit Truewind’s web site at www.truewind.com for further details about the map’s accuracy and assumptions used in its preparation. c “Selected heights chosen on the wind maps may not always be the actual height above ground level. Where the vegetation is dense, the "effective ground level" is not the base of the vegetation because the wind flow is displaced upward. The level of zero wind, called the displacement height, is typically about two-thirds the height of the top of the vegetation. In dense forests the height above ground at which the predicted wind speed actually occurs may be as much as 7-15 m (23-50 ft) higher than indicated on the maps. For example, in an area covered by forest with an average canopy height of approximately 18 m (60 ft), the Wind Map's wind speed prediction at the 50 m (164 ft) level would actually apply to a height of 62 m (204 ft) above ground [50 + 2/3(18)]”. 2 Figure 1: The Vermont and New Hampshire region of the New England Wind Map (50 meter wind speeds). Windier areas or commercial interest are green-blue to red shaded. 3 An electronic map of mean wind speeds at a height of 50 meters was selected for this study. The mean wind speed is a widely used statistic that is easily converted into energy production estimates for wind turbines and the 50-meter height is consistent with the hub-heights of commercially available turbines that are suitable for installation in New England's mountainous regions. The map also categorizes wind speed and wind power density values into seven wind classes that are routinely referenced in the wind industry and are used in this study as the basis for categorizing wind resources. The mean wind speed and power parameters associated with the seven wind classes at the height of 50 meters are presented in Table 1 along with the portion of Vermont’s total land area; and the portions of federal, state, and municipal land area found in each wind class. It should be noted that most of the land area in Vermont, 56 percent (56%), falls below Wind Class 1, averaging less than 5.1 m/s (11.4 mph) mean annual wind speeds. Of the remaining 44 percent classified in Table 1, only the windiest portion of this is commercially attractive for wind power development. In this study, areas with wind Wind Wind Power Speed, Land area Federal State Municipal Class Density, m/s (mph) (% of VT) (% of VT) (% of VT) (% of VT) W/m2 <1 Insignificant 55.7 1.1 2.5 0.4 1 160 5.1 (11.4) 30.1 1.1 3.3 0.1 2 240 5.9 (13.2) 8.7 3.6 1.8 0.2 3 320 6.5 (14.6) 2.6 1.1 0.4 .03 4 400 7.0 (15.7) 1.2 0.2 0.4 0.0 5 480 7.4 (16.6) 1.2 0.2 0.1 .004 6 640 8.2 (18.3) 0.5 .04 .01 0.0 7 1600 11.0 (24.7) .002 0.0 0.0 0.0 Total: 100% 7.3% 8.5% 0.7% Table 1: The left 4 columns show the Wind Classes (50-meter), associated power densities, mean wind speeds with the percent of Vermont’s land area that lies within each wind class.