ME 252 Thermal-Fluid Systems G. Kallio Wind Turbine Systems ME 252 Thermal-Fluid Systems G. Kallio

Introduction 2/16/2019 Wind Turbine Systems

California Wind Power Project MW Installed Energy Output (1998) California leads nation in installed wind power systems; Texas is 2nd with 1052 MW Project MW Installed Energy Output (1998) San Gorgonio Pass 615.89 805 M kWh Tehachapi 608.72 1.2 B kWh Altamont Pass 548.32 637 M kWh Solano County 240.78 NA Pacheco Pass 16.0 Others 0.675 TOTAL 2030 2/16/2019 Wind Turbine Systems

Economics Capital costs: turbines (49%), towers (10%), construction (22%) 1981-2000 Trends Rotor size: 10  71 m Power/unit: 25  1650 kW Cost/kW: $2600  $790 Capacity factor: 21%  39% 2/16/2019 Wind Turbine Systems

Turbine Design Most common design is the horizontal axis wind turbine (HAWT) Other types VAWT Drag vs. lift types 2/16/2019 Wind Turbine Systems

Wind Turbine Power Curve Power curve for a 600 kW-rated turbine 2/16/2019 Wind Turbine Systems

Components 2/16/2019 Wind Turbine Systems

Rotor Rotor consists of hub and blades Most turbines use upwind rotors with three blades made from fiberglass reinforced plastics (GRP) NACA airfoil shapes used for outermost blade profile Blade power control Passive stall control: blades have fixed pitch and designed to stall at high wind speeds Pitch control: blade pitch is variable and controlled to optimize power output 2/16/2019 Wind Turbine Systems

Rotor Size 2/16/2019 Wind Turbine Systems

Drive Train Parts include a low-speed shaft (from rotor), gearbox, high-speed shaft (to generator), bearings, brake, and couplings Input shaft: 30-300 rpm Output Shaft: usually 1800 rpm Types of gearboxes Parallel shaft Planetary Brake: used to stop rotation during maintenance or down-time 2/16/2019 Wind Turbine Systems

Generator Types Variable speed vs. variable slip Synchronous Asynchronous (induction) Variable speed vs. variable slip Most grid-connected systems use an asynchronous generator, due to ruggedness, low cost, and easy grid connection; but stator requires power from external source Stand-alone systems often use a synchronous generator 2/16/2019 Wind Turbine Systems

Yaw Mechanism Yaw error occurs when the rotor is not aligned perpendicular to the wind direction, producing less power and higher fatigue loads Most upwind HAWT use forced yawing, where electric motor(s), gearing, wind sensor, cable twist counter, and control system align the rotor with the wind Free yawing (self-aligning) systems are commonly used on downwind rotor turbines 2/16/2019 Wind Turbine Systems

Control System Goals maximize power production maximize fatigue life of all stressed components Limit drive train torque/power Sensors – velocity, position, temperature, current, voltage, etc. Controllers – electronics, computers, mechanical mechanisms Power – switches, electrical amplifiers, hydraulic pumps, valves Actuators – motors, pistons, magnets, solenoids 2/16/2019 Wind Turbine Systems

Tower Primary tower types Tubular steel Lattice (truss) Guyed Height: want at least 20m up to 1.5 times the rotor diameter; tallest towers are around 110m 2/16/2019 Wind Turbine Systems