Wind Energy

1. History of Wind Energy

  • Ancient Uses:

    • Sailing ships (thousands of years).

    • First windmills: Horizontal (Persia, 600s AD), then vertical (Europe, Middle Ages) for grinding grain/pumping water.

  • Electricity Era:

    • 1887: First wind turbine (Scotland).

    • 1930s: Decline due to grid expansion.

    • 1970s: Denmark pioneered utility-scale turbines.

2. How Wind Turbines Work

  • Process:

    • Kinetic energy (wind) → Mechanical energy (blades spin) → Electrical energy (generator).

  • Key Physics:

    • Power Equation: P=12ρAv3P=21​ρAv3

      • PP: Power output.

      • ρρ: Air density.

      • AA: Rotor area.

      • vv: Wind speed (cubed relationship!).

    • Small speed changes → Massive power shifts (e.g., 2x speed = 8x power).

3. Wind Industry Basics

  • Turbine Types:

    • Horizontal-axis (common; 3 blades, nacelle).

    • Vertical-axis (less efficient but omnidirectional).

  • Onshore vs. Offshore:

    • Offshore: Stronger winds, higher costs, fewer NIMBY issues.

  • Capacity Factor: ~40% (actual output vs. max potential).

4. Advantages of Wind Energy

  • Clean: No CO₂ emissions or water use.

  • Renewable: Globally available.

  • Low Operating Costs: $0 fuel after installation.

5. Disadvantages & Challenges

  • Intermittency:

    • Unpredictable output (varies with wind speed/season).

    • Not a standalone baseload source (needs storage/grid mix).

  • Efficiency Limits:

    • Betz Limit: Max 59.24% theoretical efficiency (real-world: 25-40%).

  • Environmental/Social Impacts:

    • Bird/bat fatalities.

    • Noise pollution.

    • Visual intrusion (NIMBY protests).

    • Rare earth metals in generators.

6. Key Equations & Concepts

  • Power Output: P=12ρAv3P=21​ρAv3 (memorize!).

    • Why v3v3? Small speed changes drastically alter power.

  • Betz Limit: 59.24% max efficiency (physics prevents 100%).