WIND ENERGYThe ultimate renewable energy

Introduction

Wind power is extracted from air flow using wind turbines or sails to produce mechanical or electrical power.

Wind power as an alternative to fossil fuels, is plentiful, renewable, widely distributed, clean, produces no greenhouse gas emissions during operation, and uses little land.

The net effects on the environment are far less problematic than those of nonrenewable power sources.

History

Wind power has been used as long as humans have put sails into the wind.

Wind power was widely available and not confined to the banks of fast-flowing streams, or later, requiring sources of fuel.

The first windmill used for the production of electricity was built in Scotland in July 1887 by Prof James Blyth of Anderson's College, Glasgow (the precursor of Strathclyde University).

The WindmillA windmill is a mill that converts the energy of wind into rotational energy by means of vanes or blades.

Wind Turbine

A wind turbine is a device that converts kinetic energy from the wind into electrical power.

The correct description for this type of machine would be aerofoil-powered generator.

Arrays of large turbines, known as wind farms, are becoming an increasingly important source of renewable energy and are used by many countries as part of a strategy to reduce their reliance on fossil fuels.

Design and Construction

Design and Construction

Wind turbines are designed to exploit the wind energy that exists at a location.

Aerodynamic modeling is used to determine the optimum tower height, control systems, number of blades and blade shape.

Conventional horizontal axis turbines can be divided into three components: the rotor component, the generator component, and the structural support component.

Design And Construction

The rotor component, which is approximately 20% of the wind turbine cost, includes the blades for converting wind energy to low speed rotational energy.

The generator component, which is approximately 34% of the wind turbine cost, includes the electrical generator, the control electronics, and most likely a gearbox (e.g. planetary gearbox),adjustable-speed drive or continuously variable transmission component for converting the low speed incoming rotation to high speed rotation suitable for generating electricity.

The structural support component, which is approximately 15% of the wind turbine cost, includes the tower and rotor yaw mechanism.

Wind Energy

Wind energy is the kinetic energy of air in motion, also called wind. Total wind energy flowing through an imaginary surface with area A during the time t is:

E = ¼mv2 = ¼(Avtp)v2 = ¼Atpv3

Where p is the density of air; v is the wind speed; Avt is the volume of air passing through A (which is considered perpendicular to the direction of the wind); Avtp is therefore the mass m passing through "A". Note that ¼ pv2 is the kinetic energy of the moving air per unit volume.

Efficiency

Since conservation of mass requires that as much mass of air exits the turbine as enters it. Betz's law gives the maximal achievable extraction of wind power by a wind turbine as 59% of the total kinetic energy of the air flowing through the turbine.

Further inefficiencies, such as rotor blade friction and drag, gearbox losses, generator and converter losses, reduce the power delivered by a wind turbine. Commercial utility-connected turbines deliver 75% to 80% of the Betz limit of power extractable from the wind, at rated operating speed.

Advantages

The environmental impact of wind power when compared to the environmental impacts of fossil fuels, is relatively minor.

While a wind farm may cover a large area of land, many land uses such as agriculture are compatible with it, as only small areas of turbine foundations and infrastructure are made unavailable for use.

The price of wind power is much more stable than the volatile prices of fossil fuel sources.

Disadvantages

Wind power forecasting methods are used, but predictability of any particular wind farm is low for short-term operation. For any particular generator there is an 80% chance that wind output will change less than 10% in an hour and a 40% chance that it will change 10% or more in 5 hours.

There are reports of bird and bat mortality at wind turbines as there are around other artificial structures.

Worldwide Distribution

Wind Power Production

United States ChinaSpain GermanyIndia United KingdomFrance ItalyCanada DenmarkRest Of The World

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