Transcript Slide 1
Wind Turbine Design Methods Robert Scott [email protected] November 1, 2007 Advantages of Wind Power • • • • Clean Flexible Large Potential for Growth Economically Viable (most of the time – peak opportunity) Design • • • • • • Siting Configurations Sizing Rotor Tower Generator Siting • • • • • Wind speed Climate Conditions Inland or at sea Terrain Surrounding Community Configurations • Vertical Axis – Darrieus – H-Type – Savonius • Disadvantages – Size limits – Reliability Configurations • Horizontal Axis – 3-bladed most common, structures and dynamic considerations – 1 and 2-bladed designs exist, but don’t even bother. – Upwind or Downwind Sizing • Designs exist for capacities of <1 kW up to 5 MW. • What are you designing for? – Utilities – Individual Use – Special Use Rotor • Diameter • Blades – Airfoils – Shape (Twist) • Control – Stall/Pitch regulated – Rotational Speed 3.50 3.00 Rated Capacity (MW) – Larger = higher capacity and higher costs, helps for lower windspeed 4.00 2.50 2.00 1.50 1.00 0.50 0.00 0 20 40 60 Rotor Diameter (m) 80 100 120 Rotor • Control – Stall/Pitch regulated – Rotational Speed – Cut-in, rated, cut-out velocities Tower • Type – Tubular – Lattice • Height – Tall = smoother air – Short = better for construction Wind Variability • The terrain of the site affects the wind speed. • Higher roughness lengths slow the wind down more at low elevations. U ( z hub ) lnz hub z 0 U z anem lnz anem z 0 Generator • Enclosed? • Gearbox? • Direct-drive? Design Process • Performance – Efficiency – Reliability • Economics – Infrastructure (~ $1.7 Million per MW) – Construction – Operational Costs (~ 2% of acquisition costs/yr) – Subsidies The Power Curve Published power curve for a 1.5 megawatt wind turbine. Nordex S70. Vc-o≈ 2VR Wind Variability 0.16 Ū = 5 m/s Ū = 7 m/s Ū = 9 m/s Ū = 11 m/s 0.14 – The Weibull distribution k 1 0.12 prob dist funct, ƒ • Model the wind as a probability density function 0.1 0.08 0.06 0.04 0.02 0 kx f x; k , e k 10 15 20 25 wind speed (m/s) Ū = 5 m/s Ū = 7 m/s Ū = 9 m/s Ū = 11 m/s 1 0.8 2 U U 2 f U e U 5 1.2 x For wind, F U 1 e 0 k 2 cumul. dist, F F x; k , 1 e x 0.6 0.4 0.2 0 0 5 10 15 wind speed (m/s) 20 25 What does all this tell us? 0.16 Capacity Factor: Ū = 5 m/s Ū = 7 m/s Ū = 9 m/s Ū = 11 m/s 0.14 t 0.12 CF 0.08 Pdt 0 Prated t E E max 0.06 A capacity factor of 35% for a wind turbine is considered good. 0.04 0.02 1 0 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 0.9 Capacity Factor Ū = 5 m/s Ū = 7 m/s Ū = 9 m/s Ū = 11 m/s 0.8 Ū = 5 m/s CF = 0.05 Ū = 7 m/s CF = 0.18 0.7 0.6 1-F prob dist funct, ƒ 0.1 0.5 0.4 Ū = 9 m/s CF = 0.42 Ū = 11 m/s CF = 0.73 0.3 0.2 0.1 0 0 0.1 0.2 0.3 0.4 0.5 Capacity Factor 0.6 0.7 0.8 0.9 1 Sensitivity Studies – HOMER Sensitivity to wind speed Ū = 5 m/s: 225,000K kWh/yr @ $0.15/kWh Sensitivity to hub height zH = 40 m 500,000K kWh/yr @ $0.087/kWh Ū = 14 m/s: 1,000,000K kWh/yr @ $0.055/kWh Ū = 5 m/s: 675,000K kWh/yr @ $0.07/kWh The Power Coefficient Cp P 1 U 3 A 2 0.5 0.45 0.4 0.35 power coeff Cp The power output normalized to the energy density of the wind and the rotor area. 0.3 0.25 0.2 0.15 0.1 0.05 Measures the amount of power actually converted out of the power available in the wind 0 0 5 10 15 wind speed (m/s) 20 25 Optimized Costs of Energy • High wind speed areas, U > 10 m/s consistently • Maximized hub heights, zH = 100 m • Large development – Economies of scale reduce per unit price of turbines. Comparison with other fuels: Coal $0.02 – 0.03/kWh Natural Gas $0.05 – 0.08/kWh Nuclear $0.02 – 0.03/kWh Note: Other fuels, especially coal and nuclear, benefit from not having to include their high external costs in the price of energy. Wind energy also receives a $0.015/kWh tax credit. Optimized Cost of Energy: • $0.038/kWh (3% interest) • $0.040/kWh (4% interest) • $0.042/kWh (5% interest) • $0.044/kWh (6% interest) Useful Websites • List of wind farms: http://www.fplenergy.com/portfolio/contents/portfolio_by_ source.shtml • Wind turbine Manufacturers – – – – – http://www.skystreamenergy.com/skystream/ http://www.enercon.de/en/_home.htm http://www.nordex-online.com/en/ http://www.gamesa.es/index.php/en http://www.suzlon.com/ • Current Events – http://www.cnn.com/2007/TECH/science/10/09/pip.wind.energy/ – www.wind-watch.org