Wind Turbine Technology and System Considerations 02042020 3 slides

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Central Washington University *

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Mechanical Engineering

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Oct 30, 2023

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2/6/2020 1 Wind Turbine Technology ENSC 220 Small Scale Wind Power • Utility Scale Wind Power – Larger Turbines • Larger than 100 kW • Most common today – 1.5 to 3.0 MW on land – Up to 6 MW off shore – Utility connected, built in farms • Small Scale Wind Power – Small Turbines • Up to 100 kW • Most common sizes – Below 1 to 10 kW GE 1.5 MW Bergey 10 kW Power in the wind (W) = 1 / 2  A V 3 0 5 10 15 20 25 30 35 2 4 7 9 11 13 16 18 20 22 25 27 29 31 34 36 38 40 42 45 47 49 51 Wind Power (kW) Wind Speed (mph) The Power in the Wind (kW) for 8.2 ft dia Area 1 2 3

2/6/2020 2 Betz Limit • If you catch all the power in the wind you will stop the wind and won’t be able to convert it to rotational energy • If you catch none of the power you can’t turn it to rotational energy • There is a theoretical limit to how much you can catch and convert to rotational energy • Albert Betz 1919 calculated the limit to be – 59.3% Power in the wind (W) = 1 / 2  A V 3 And Betz Limit 0 5 10 15 20 25 30 35 40 45 50 2 4 7 9 11 13 16 18 20 22 25 27 29 31 34 36 38 40 42 45 47 49 51 Wind Power (kW) Wind Speed (mph) The Power in the Wind (kW) for 8.2 ft dia Area Betz Limit Power in the wind Two Configurations • Horizontal Axis – All major manufacturers use this design – 2 or 3 blades are most common • Vertical Axis – Many have tried and failed with this design – Still a couple of small manufactures trying this 4 5 6

2/6/2020 3 Three Types of Small Turbines • Savonious • Darrieus • Horizontal Axis Horizontal Axis Wind Turbines National Renewable Energy Laboratory Innovation for Our Energy Future Savonius Wind Turbines (II) Helix Wind 7 8 9

2/6/2020 4 National Renewable Energy Laboratory Innovation for Our Energy Future Darrieus Wind Turbines Straight-bladed rotor or H-rotor (I) Mariah Wind Power Pacwind Wind Spire Overspeed Control Approaches 1. Furling - some manufacturers are moving away from furling due to: – Concerns about sound levels – Inconsistent results – High forces on the turbine during furling 2. Constant-Speed Operation - induction generator, with a gearbox, is coupled to the grid frequency keeping the rotor at a constant speed 3. Dynamic Braking - slowing the rotor by temporarily increasing the load by the generator which slows the rotor, taking it into aerodynamic stall 4. Aerodynamic Stall - Stalls occur at the critical angle of attack , where induced drag (airfoil drag) exceeds lift 5. Variable-Pitch Blades - the blade angle to the wind is changed to reduce aerodynamic lift, activated by centrifugal forces or drive motors & controls Over-Speed Protection – Furling • Upward Furling: The rotor tilts back during high winds 10 11 12

2/6/2020 5 Over-Speed Protection – Aerodynamic Stall National Renewable Energy Laboratory Innovation for Our Energy Future Overspeed/Overpower Control is Difficult • VAWTs take wind from any direction, so they can’t turn out of the wind (furl) like a HAWT • VAWTs are fixed pitch, so they can’t pitch the blades to feather or to stall • VAWTs do not stall well by reducing rotor speed, rotor torque remains high – Oversized generator, or – Large brake • Overspeed control is difficult for a HAWT, too, but VAWTs have fewer options Abundant Renewable Energy, LLC From R. Preus Bergey XL (1 kW) 13 14 15

2/6/2020 6 Power (kW) Power Curve Bergey 1 kW Wind Turbine Power 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 4 7 9 11 13 16 18 20 22 25 27 29 31 34 36 38 40 42 45 47 49 51 Turbine Power (kW) Wind Speed (mph) Power Curve Bergey 1 kW Wind Turbine Power 0 2 4 6 8 10 12 14 16 18 2 4 7 9 11 13 16 18 20 22 25 27 29 31 34 36 38 40 42 Power (kW) Wind Speed (mph) Wind Power vs Power Curve for 1 kW turbine Power in the wind Power Curve Bergey 1 kW Betz Limit 0 5 10 15 20 25 30 35 40 45 0-5 mph 5-10 mph 10-15 mph 15-20 mph 20 and Above % of year Wind Speeds Lincoln, NE 1996-2005 (hprcc data) 16 17 18

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