Wind turbine

**History:**
– First recorded wind-powered machine by Hero of Alexandria
– Practical wind power plants in Sistan, Persia from 7th century
– Wind power in Europe during Middle Ages
– Dutch windmills in Rhine delta in 14th century
– Croatian inventor Fausto Veranzio’s advanced wind turbines in 1595

**Wind Power Density:**
– Wind Power Density measures wind energy available at a location
– Calculated based on wind velocity and air density
– Wind turbines classified by wind speed and turbulence intensity
– Class I to Class III, with A to C turbulence intensity
– Different wind speeds and turbulence levels for each class

**Efficiency:**
– Betz’s law states the maximal achievable extraction of wind power by a turbine
– Maximum theoretical power output of a wind machine is 59.3% of kinetic energy rate
– Formula for calculating maximum theoretical power output
– Conservation of mass principle for air entering and exiting a turbine
– Relationship between effective disk area, wind velocity, and power output

**Impact and Applications of Wind Turbines:**
– Wind turbines convert wind’s kinetic energy into electrical energy
– Hundreds of thousands of large turbines generating over 650 GW of power
– Wind farms adding 60 GW of power annually
– Study showing wind energy’s low greenhouse gas emissions
– Used globally to lower energy costs and reduce reliance on fossil fuels
– Small turbines for battery charging and remote devices
– Larger turbines contributing to domestic power supply
– Unused power sold back to utility suppliers via electrical grid
– Manufactured in various sizes with horizontal or vertical axes
– Used for various purposes like traffic warning signs and power generation

**Efficiency Factors:**
– Wind-to-Rotor Efficiency impacts wind power price
– Inefficiencies like gearbox losses reduce power output
– Power extraction above rated speed protects components
– Commercial turbines deliver 75-80% of extractable power
– Efficiency may decrease due to blade contamination
– Long-Term Efficiency Trends
– Efficiency can decrease slightly over time
– Dust and insect debris on blades affect aerodynamics
– Analysis of older turbines in Denmark revealed production decreases
– Stable weather conditions result in higher efficiency
– Wind speed stability impacts turbine efficiency
– Material Impact on Efficiency
– Different materials affect wind turbine efficiency
– Experiment showed higher mass materials have lower power coefficient
– Material choice impacts friction moment and power output
– Glass and glass/carbon epoxy blades had lower efficiency
– Air velocity significantly influences turbine efficiency
– Location Selection Importance
– Air velocity is crucial for turbine efficiency
– Choosing the right location impacts turbine performance
– Wind velocity is higher near shores due to land-ocean temperature difference
– Proper location selection enhances turbine efficiency
– Wind turbine efficiency is closely linked to air velocity
– Atmospheric Stability Effects
– Stable weather conditions lead to higher efficiency
– Greater efficiency achieved in stable wind conditions
– Faster wake recovery and flow entrainment in stable conditions
– Wind speed can increase by 7% under stable conditions
– Turbine wakes recover faster in unstable atmospheric conditions