Natural Resources and Farming Systems: Wind Energy Notes

Topographic Conditions: Wind energy potential varies significantly based on terrain at $50\,m$ above ground level. Categories include sheltered terrain, open plains, sea coasts, and open sea.
Measurement Metrics: Resources are measured by wind speed ( $m\,s^{-1}$ ) and power density ( $W\,m^{-2}$ ).
Offshore vs. Onshore: Offshore resources typically offer higher wind speeds; for example, at $100\,m$ height over open sea, speeds can exceed $10.0\,m\,s^{-1}$ .

Renewable Energy Mix (2024): Wind and marine sources account for $25\%$ of the UK's renewable energy, following bioenergy at $50\%$ .
Onshore Capacity: Cumulative installed capacity has grown steadily from 2010 to 2022, with Scotland holding the highest share of onshore wind capacity.
International Comparison: The UK's wind share of total generation was approximately $24\%$ (per BEIS), compared to Denmark's $48\%$ .
UK Capacity Outlook: The Onshore Wind Taskforce Strategy (2025) aims for a clean power capacity range of $27\text{--}29\,GW$ by 2030.

Types: Turbines are categorized into Horizontal Axis and Vertical Axis designs.
Aerodynamics: Power is generated through the forces of Lift and Drag acting on the blades as wind flows through the rotor.
Major Components:
- Nacelle: Houses the gearbox, generator, and controller.
- Rotor: Includes the blades and hub; pitch control adjusts blade angles.
- Tower: Supports the structure; hub height significantly impacts wind capture.
- Directional Controls: Anemometer and Wind Vane feed data to the Yaw motor and Yaw drive to align the turbine with the wind.
Scale Comparison:
- Small turbine: Approximately $2.5\,kW$ rated capacity, $11\,m$ hub height.
- Utility-scale turbine: Approximately $1,650\,kW$ rated capacity, $78\,m$ hub height, saving $1,900\,tCO_2/year$ .

Cost Distribution: According to Munday et al., the turbine represents $64\%$ of the total capital cost for a $5\,MW$ project.
Other Costs: Civil engineering ( $13\%$ ), electrical infrastructure ( $8\%$ ), and grid connection ( $8\%$ ) are the next largest expenses.
Trend: The Levelized Cost of Energy (LCOE) has decreased significantly since 1980 as hub heights and rotor diameters have increased.

Wind Speed and Height: Wind speed increases with height above the ground; however, urban sites encounter higher displacement heights and turbulence due to buildings.
Obstacles: Turbines should be located away from the "zone of max turbulent flow." A general rule (per Olabi et al.) is to place turbines at a distance of at least $10 \times H$ (height of the obstacle) downstream.
Spacing: Proper turbine spacing within a site is essential to account for prevailing wind directions and maximize yield.

Carbon Footprint: Onshore wind has one of the lowest carbon footprints at approximately $11\,gCO_2\,eq/kWh$ , compared to coal at $820\,gCO_2\,eq/kWh$ .
Habitation Proximity: Recommended distances vary by region. In England, the recommended distance is $500\,m$ , while Wales utilizes a $2,000\,m$ guideline.
Public Perception: In May 2023, support for onshore wind in the UK was high ( $78\%$ overall), though local acceptance for specific developments was lower (around $43\%$ ).
Environmental Concerns: Issues include bird mortality (ranging from $0.03$ to $35$ birds/turbine/year depending on location), Electromagnetic Interference, and Shadow Flicker.

Acceptance Rates (1991–2017): Onshore wind has an approval rate of approximately $44\%$ , with $52\%$ of applications being refused or abandoned.
Application Trends: There has been a significant decline in the number of onshore wind planning applications in England since 2015.