Wind Energy Resource, Advantages, and Constraints Dr. Richard Nelson Engineering Extension

Renewable Resources and Technologically Viable End-uses Wind - electricity and hydrogen production No Greenhouse Gas Emissions Insurance Against Conventional Fossil-based Price Risk No Sulfur Dioxide (SO2), Nitrous Oxide (NOx), or Mercury Emissions

Why Wind Energy? Wind, for now, is the renewable energy resource/technology of choice “Free” resource A “clean” resource due to: Replacement of a “dirty” energy source (coal) and, No emissions associated with its use Can be utilized on underutilized land or on lands currently in commodity crop production (“harvest” on the surface and “harvest” above the surface) Will primarily be used for electricity generation for immediate end-use or as a “driver” for hydrogen production

Energy Production and the Environment Energy use in power plants accounts for: 67% of air emissions of SO2, the primary cause of acid rain. SO2 causes acidification of lakes and damages forests and other habitats. 25% of NOx, which causes smog and respiratory ailments. 33% of Hg (mercury), a persistent, bio-accumulative toxin which increases in concentration as it moves up the food chain, e.g. from fish to birds, causing serious deformities and nerve disorders. SOURCES: Union of Concerned Scientists (UCS)

Wind Energy Benefits No air emissions No fuel to mine, transport, or store No cooling water No water pollution No wastes

Wind Resources in the United States Wind resources are characterized by wind-power density classes, ranging from class 1 (the lowest) to class 7 (the highest). Good wind resources (class 3 and above) which have an average annual wind speed of at least 13 miles per hour, are found along the east coast, the Appalachian Mountain chain, the Great Plains, the Pacific Northwest, and some other locations.

Wind Resources in the United States Wind speed is a critical feature of wind resources, because the energy in wind is proportional to the cube of the wind speed.

Kansas Wind Potential Kansas is one of the three best wind states in the country Total “windy” land equals more than 108,000 square kilometers (about 1/2 of state) Total Energy Potential = 1.07 trillion kWh or 121,900 MWa Most of that potential probably won’t be developed . . .

Physical & Engineering Aspects Wind Energy Basics Physical & Engineering Aspects

P = ½ * air density * Area Swept by Rotor * Wind Speed3 Wind Power Equation P = ½ * air density * Area Swept by Rotor * Wind Speed3 P = ½ * ρ * A * V3 Power in the wind is correlated 1:1 with area and is extremely sensitive to wind speed (the cubic amplifies the power significantly) If the wind speed is twice as high, it contains 23 = 2 x 2 x 2 = 8 times as much energy A site with 16 mph average wind speed will generate nearly 50% more electricity and be more cost effective than one with 14 mph average wind speed (16*16*16) / (14*14*14) = 1.4927 Therefore, it “pay$” to hunt for good wind sites with better wind speeds

Energy from the Wind Turbine output drives wind economics and output is a strong function of wind speed Wind speed increases with height above the ground Power = 1/2 × (air density) × (area) × (wind speed)³ Energy in the wind increases as height increases (theoretically) V2/V1 = (H2/H1)1/7

Wind Turbines

Turbines: Different Sizes and Applications Small (10 kW) Homes (Grid-connected) Farms Remote Applications (e.g. battery changing, water pumping, telecom sites) Intermediate (10-500 kW) Village Power Hybrid Systems Distributed Power Large (500 kW – 5 MW) Central Station Wind Farms Distributed Power Offshore Wind

Large Wind Systems Range in size from 100 kW to 5 MW Provide wholesale bulk power Require 13-mph average wind sites

Technology Overview Large Wind Projects Over 98-99% availability Can deliver power for less than 5 cents/kWh (with Production Tax Credit) in many locations ~6,000 MW to be installed nationwide at end of 2003 In 2004, will generate about 3x Vermont’s total use

Typical Turbine Size 1.3 to 1.8 MW rated capacity Rotor diameter 60 to 80 meters Tower height 60 to 80 meters Turbine footprint 10 m x 10 m Lowest ground clearance is at least 100 ft. 245-330 ft. TIP 165-220 ft TOWER Apx. 100 ft.

Next Generation Wind Turbines

Wind Turbine Schematic

Nacelle for 1.65-MW turbine Two more slides to give a feel for the scale of a state-of-the-art wind turbine. First, a nacelle . . .

Cross section of blade for 1.65-MW turbine . . . And second, a blade.

Variability Quantifying Wind Power Performance 99% Availability >90% Operating Time* 30 – 40% Capacity Factor * Lake Benton, Minnesota Analysis of Windfarm Operation

Expected Output/Capacity Factor The capacity factor is simply the wind turbine's actual energy output for the year divided by the energy output if the machine operated at its rated power output for the entire year A reasonable capacity factor would be 0.25 to 0.30. A very good capacity factor would be 0.40 Capacity factor is very sensitive to the average wind speed

Power Curves The turbine would produce about 20% of its rated power at an average wind speed of 15 miles per hour (or 20 kilowatts if the turbine was rated at 100 kilowatts).

Operating Characteristics of Wind Turbines

“Value” of Wind Energy The value of a wind turbine or wind farm depends upon many factors location terrain wind speed = f(location, terrain) cost of competing energy source rate structure of competing energy source

Wind Insures Against Fuel Price Risk Platts “conservatively estimates that generating electricity from renewable sources can ultimately save consumers more than $5/MWh (1/2¢ per kW-h) by eliminating fuel price risk”* *4/8/03 announcement re “Power Price Stability: What’s it Worth?” Value of domestic fuel source (wind) would have a direct benefit on the Kansas/community Wind energy “Fuel” is inflation-proof; therefore impervious to fuel price hikes

Wind - Natural Gas Comparison High Operating Costs Low Capital Cost Dispatchable Fuel Supply/Cost Risk Smog, Greenhouse Gas Emissions Wind Low Operating Cost High Capital Cost Non-dispatchable No Fuel Supply/Cost Risk No Emissions

Wind Power Costs Wind Speed Assuming the same size project (total MW installed), the better the wind resource, the lower the cost; capture more energy for the same capital/ installed/ maintenance cost

Wind Power Costs Project Size Assuming the same wind speed, a larger wind farm is more economical; economy-of-scale associated with wind farm installation

Wind Power Isn’t Perfect Wind Power output varies over time; it isn’t dispatchable Wind Power is location-dependent (rural vs. urban where it is needed most) Wind Power is transmission-dependent for tie-in to the grid Wind Power has environmental impacts (pro / con) Wind Power can only meet part of the electrical load

Common Misunderstandings Wind turbines are only generating electricity about one third of the time. Wind turbines generate electricity essentially all the time, but only at their rated capacity about 30-40% of the time

Wind Web Sites www.awea.org www.wwea.org www.windpower.org