Wind Energy

Wind Energy Overview

  • Wind energy is generated by air movement caused by uneven heating of the Earth's surface by the sun.

  • Air over land heats up and rises, creating local breezes; this process reverses at night.

  • Global wind patterns are influenced by Earth's rotation and seasonal variations.

History of Wind Power

  • Wind has been harnessed for millennia for sailing and milling grains.

  • Notable early uses include water pumping in the Netherlands and powering livestock water needs in arid regions.

Development Milestones

  • 1887: Prof. James Blyth built the first windmill for electricity in Scotland, charging batteries for lighting.

  • Charles F. Brush constructed a large wind turbine in Ohio (1888) to power buildings.

Current Capacity and Trends

  • Over 200 GW of wind capacity installed globally across 83 countries.

  • Offshore wind projects are increasing, with significant installations planned in Europe and China.

  • Denmark generates over 1/3 of its electricity from wind energy.

Types of Wind Energy Collectors

  1. Horizontal-axis Rotors

    • Most common; blades rotate parallel to wind direction.

    • Subtypes include upwind and downwind designs.

  2. Vertical-axis Rotors

    • Simpler design; wind direction changes do not require rotation.

    • Includes Savonius and Darrieus types; generally less efficient.

  3. Cross-wind Horizontal-axis Rotors

    • Rotate perpendicular to wind; experimental designs.

Axial Momentum Theory

  • Power extraction from wind can be calculated based on wind velocity.

  • Maximum energy extraction occurs when wind speed is reduced to one-third its original speed (Cp max = 16/27).

Applications of Wind Energy

  • Directly used for pumping water and generating electricity.

  • Can also be used for heat generation and producing hydrogen via electrolysis.

Energy Storage Systems

  • Storage options include batteries, pumped storage hydro, compressed air, and hydrogen.

  • Wind energy storage allows for uninterrupted supply and peak load management.

Site Selection Factors

  • Wind velocity is key; higher speeds yield more power (cubical relationship).

  • Factors like ground roughness and terrain affect wind profiles and potential energy.

Economic Considerations

  • Costs involve wind availability, service life, capital investment, and maintenance.

  • Current average installation costs around $1,500 per kW, with goals to reduce this significantly.

Environmental Considerations

  • Concerns include structural hazards, noise, aesthetic impacts, wildlife effects, and potential electromagnetic interference.

  • Further studies on wildlife impacts needed; mitigation strategies include using visual cues for birds.

Wind Formation: Wind is formed by the uneven heating of the Earth's surface by the sun. As the sun heats the ground, some areas warm up faster than others, causing the air above these heated regions to rise. This creates differences in air pressure, with warmer, lighter air rising and cooler, denser air moving in to replace it, resulting in air movement known as wind. Additionally, factors such as the Earth's rotation and geographical features influence local and global wind patterns.