Wind Energy

24/01/23 16:14:22

• manipulation of ‘leading edge’, called ‘pitching’.
• Located higher from the ground where wind speeds are higher
• Turbine (electricity), mill (mechanical work).
• Lack of offshore wind, one of the reasons we lag behind Denmark (similar size, environment and population).
• Offshore turbines significantly bigger than onshore (94m blades).
• Power is a function of swept area and wind speed.

27/01/23 10:49:50

• The wind resource (how we can model it).
• Causes of wind: air pressure differences.
• Sun heats atmosphere differently around the globe.
• Differential heating and coriolis effect. This develops an atmospheric boundary layer due to friction with air and earth. This boundary layer has a ‘vertical velocity profile’.
• ”Wine engineering is best described as the rational treatment of interaction betweeen wind in the atmospheric boundary layer and man and his works on the surface of earth”
• off shore wind allows access to high windspeeds for low altitudes.
• reduction in velocity of wind is a function of surface roughness, different for different terrain types.
• Wind is stochastic. Wind speed can be assumed statistically as the sum of a mean component and a fluctuating component.
• If you go out and measure wind speeds over a 10 minute interval, generally fairly stable.
• Fluctuations in wind speed over that 10 minutes is called turbulence.
• A measure of turbulence is turbulence intensity. I or Iv. Std deviation of the windspeed/mean wind speed. A crude measure of turbulence. Normally varies from 5-30% average of about 10%.
• We can use the kinetic energy of the wind for power. To do useful work.
• From a power point of view you want large turbulence and windspeeds, but from a design point of view, the higher the windspeed, the higher the load (on the structure).
• Load due to wind …
• Felxible wind structures, making it dynamic for dynamic loads.
• Dynamic loading (loading that changes with time).
• streamlined body (wing of airplane), when immersed in fluid flow doesn’t have detachment from fluid. Compared to a bluff body (like a building).
• Bluff body aerodynamics slide.
• Components to a wind turbine.
• Blades rotate low speed shaft, at the same speed as the blade, gearbox steps up the low speed rotation to a high speed shaft, connected to a generator
• Vast majority of turbines are upwind machines (the blades are not shadowed by tower). The drawback being, the blades need to beoriented (yawing) to the wind, needs a yawing sysstem which can be expensive.
• Most of failures are due to gearbox failures.