Wind Energy

Introduction to the Wind Energy Industry

Wind is air in motion. Winds are caused by the uneven heating of the earth’s surface by the sun. The earth’s surface is made of different types of land and water. These different types absorb the sun’s heat at different rates giving rise to the differences in temperature and subsequently to winds.

During the day, the air above the land heats up more quickly than the air over water. The warm air over the land expands and rises, and the heavier, cooler air rushes in to take its place, creating winds. At night, the winds are reversed because the air cools more rapidly over land than over water.

In the same way, the large atmospheric winds that circle the earth are created because the land near the earth's equator is heated more by the sun than the land near the North and South Poles.

One can hence say that wind energy is derived from solar energy.

Wind energy is hardly new; it has been used in some form or another for centuries. However, large-scale, commercial utilization of wind as a form energy source is relatively recent.

Wind Energy Potential

Outside of hydro-energy, wind energy is one of the most significant renewable energy sources for electricity generation worldwide. Total wind energy installed capacity worldwide in 2008 was about 120 GW. Only hydro – at 800 GW installed capacity in 2008 – has a higher installed capacity for renewable electricity generation

The Global Wind Energy Council (GWEC) predicts that the global wind market will grow by over 155% from 2007 to reach 240.3 GW of total installed capacity by 2012 (GWEC, 2008). This would represent an addition of 146.2 GW in five years. The electricity produced by wind energy will reach over 500 TWh in 2012 (up from 200 TWh in 2007), accounting for around 3 per cent of global electricity production (up from just over 1 per cent in 2007).

Productive Wind Speed: The range of wind speeds that are usable by a particular wind turbine for electricity generation is called productive wind speed. The power available from wind is proportional to cube of the wind's speed: double the speed, eight times the energy. So as the speed of the wind falls, the amount of energy that can be got from it falls very rapidly. On the other hand, as the wind speed rises, so the amount of energy in it rises very rapidly; very high wind speeds can overload a turbine. Productive wind speeds will range between 2.5 m/sec to 35 m/sec (9km/hr to 125km/hr).

Summary of Locations of the Most Attractive Regions for Wind Energy

 

Region

Location

Europe

North and west coasts, some Mediterranean regions

Asia

East coast, some inland areas

Africa

North, southwest coast

Australasia

West and south coast

North America

Most coastal regions, some central zones, especially where mountainous

South America

Best towards the south

Source: Czisch, 2001 

Technology

Wind energy technology is fairly simple. Wind turbines are located in farms (wind farms) that experience significant winds. The turbine is connected to a generator to generate electricity.

Wind Turbines

A wind turbine is a rotating machine which converts the kinetic energy in wind into mechanical energy. If the mechanical energy is used directly by machinery, such as a pump or grinding stones, the machine is usually called a windmill. If the mechanical energy is then converted to electricity, the machine is called a wind generator.

Wind turbines can be separated into two types based by the axis in which the turbine rotates.

  • Vertical Axis
  • Horizontal Axis

Turbines that rotate around a horizontal axis are more common. Vertical-axis turbines are less frequently used.

The wind turbines are grouped in a location to farm a wind farm.

Wind Farms

Based on their locations, the different types of wind farms are:

  • Onshore
  • Nearshore
  • Offshore
  • Airborne

Onshore Wind Farms

Onshore wind farms are the conventional wind farms. These are erected on land, usually in large vacant spaces such as farms.

These types of wind farms have some advantages as well as disadvantages over offshore wind farms.

Advantages - These are cheaper to construct and easier to integrate with the electricity grid. These are also easier to operate and maintain.

Disadvantages - Some of the disadvantages present in these wind farms are in terms of turbulence and obstructions (buildings, mountains, etc.), land-use disputes, limited availability of lands, objections based on visual impact, noise, impact on wildlife, etc.

The disadvantages present in onshore farms – and the wider wind-marine resources and availability – may explain the dislocation of a significant part of the investment in wind energy to offshore systems.

Nearshore Wind Farms

Near shore turbine installations are on land within three kilometers of a shoreline or on water within ten kilometers of land. These areas are good sites for turbine installation, because of wind produced by convection due to differential heating of land and sea each day. Wind speeds in these zones share the characteristics of both onshore and offshore wind, depending on the prevailing wind direction.

Offshore Wind Farms

Offshore wind development zones are generally considered to be ten kilometers or more from land.

The following is the method by which these farms are constructed and operated.

Once a suitable place for the wind farm is found, piles are driven into the seabed. Erosion protection mechanisms are placed at the base to prevent damage to the sea floor, and signs erected to make the wind farm visible to ships.

Once the turbine is assembled, sensors on the turbine detect the wind direction and turn the head, known as the nacelle, to face into the wind, so that the blades can collect the maximum energy. The aerodynamically shaped blades rotate around a horizontal hub, which is connected to a shaft. This shaft, via a gearbox, powers a generator to convert the energy into electricity. Subsea cables take the power to an offshore transformer which converts the electricity to a high voltage before running it back to connect to the grid at a substation on land.

Offshore wind turbines are less obtrusive than turbines on land, as their apparent size and noise is mitigated by distance. Because water has less surface roughness than land (especially deeper water), the average wind speed is usually considerably higher over open water. Capacity factors (utilisation rates) are considerably higher than for onshore and nearshore locations.

In stormy areas with extended shallow continental shelves, turbines are practical to install.

Airborne Wind Farms

Airborne wind turbine is a design concept for a wind turbine that is supported in the air without a tower. A tether would be used to transmit energy to the ground, either mechanically or through electrical conductors. These systems would have the advantage of tapping an almost constant wind and doing so without a set of slip rings or yaw mechanism, without the expense of tower construction.

Of the four types of wind farms mentioned above, the onshore wind farms are the most common.

Wind Farm Capacity

Since wind speed is not constant, a wind farm's annual energy production is never as much as the sum of the generator nameplate ratings multiplied by the total hours in a year. The ratio of actual productivity in a year to this theoretical maximum is called the capacity factor. Typical capacity factors are 20-40%, with values at the upper end of the range in particularly favorable sites. For most calculations, a capacity factor of 30% is taken. For example, a 1 megawatt turbine with a capacity factor of 30% will produce only 2628 MWh (0.30x24x365) and not 8,760 megawatt-hours in a year (1x24x365) 

2.7.4 Wind Industry - Status and Trends

Global Installed Capacity of Wind Power (Current) 

Source: Global Wind Energy Council Report, 2008

Observations from the above chart:

CAGR of cumulative installed capacity between 1996 and 2008: 28.25%

CAGR of cumulative installed capacity between 1996 and 2002: 31.2 %

CAGR of cumulative installed capacity between 2002 and 2008: 25.37% 

One can see that the growth rate has been high and consistent over the past 12 years, and this trend is expected to continue. Assuming a CAGR of 25 % for the next five years 2008-13, the following are likely to be the global installed capacity.

 

Year

Cumulative Global Capacity (MW)

2009

150997

2010

188746

2011

235933

2012

294916

2013

368646

Even under the above scenario, it should be noted that the total electricity generation capacity from wind energy will be less than 8% of the total installed capacity worldwide in 2013. In 2009, global installed capacity for electricity is estimated to be about 5000 GW.

        Source: Global Wind Energy Council Report, 2008

Observations from the above chart: 

CAGR of annual installed capacity between 1996 and 2008: 28.9%

CAGR of annual installed capacity between 1996 and 2002: 33.5 %

CAGR of annual installed capacity between 2002 and 2008: 24.5% 

Taking the estimates for global cumulative installed capacity for 2008-12 as the base (presented earlier), the annual installed capacity estimates for the period are as follows:

Year

Cumulative Global Capacity End of Year Estimate (MW)

Annual Installed Capacity Estimate (MW)

2009

150997

30199

2010

188746

37749

2011

235933

47187

2012

294916

58983

2013

368646

73730

Regional Wind Energy Scenario:

Region

Total installed capacity end 2008 (GW)

% Contribution

Africa & Middle East

0.67

0.55

Asia

24.37

20.17

Europe

65.95

54.59

Latin America & Caribbean

0.63

0.52

North America

27.54

22.80

Pacific Region

1.64

1.36

World

120.8

 

 

 

Annual Installed Capacity by Region 2003-2008

 Source: Global Wind Energy Council Report, 2008

Wind Energy Installed Capacity in Top Ten Countries (2008)

 Top 10 Total and New Installed Capacities

Country

MW

Top 10 Total Installed Capacity %

Country

MW

Top 10 New Capacity %

USA

25,170

20.8

US

8,358

30.9

Germany

23,903

19.8

China

6,300

23.3

Spain

16,754

13.9

India

1,800

6.7

China

12,210

10.1

Germany

1,665

6.2

India

9,645

8

Spain

1,609

5.9

Italy

3,736

3.1

Italy

1,010

3.7

France

3,404

2.8

France

950

3.5

UK

3,241

2.7

UK

836

3.1

Denmark

3,180

2.6

Portugal

712

2.6

Portugal

2,862

2.4

Canada

526

1.9

Rest of the World

16,693

13.8

Rest of the World

3,285

12.2

Total top 10

104,104

86.2

Total top 10

23,766

87.8

Total

120,798

100

Total

27,051

100

Source: Global Wind Energy Council, Global Wind Report 2008

Wind Energy: Future Potential

Global Wind Energy Installations and Capacity - Market Forecast: 2009-2013

    Source: Global Wind Energy Council Report, 2007

 

Wind Market Predictions

Global Wind Energy Council (GWEC) is predicting the global wind market to grow by over 155% from its current size to reach 240 GW of total installed capacity by the year 2012. This would represent an addition of 146 GW in 5 years, equaling an investment of over €180 billion (277 billion US$, both in 2007 value). The electricity produced by wind energy will reach over 500 TWh in 2012 (up from 200 TWh in 2007), accounting for around 3% of global electricity production (up from just over 1% in 2007). The main areas of growth during this period will be North America and Asia, and more specifically the US and People's Republic of China (Source: GWEC – Global Wind 2007 Report)

Wind Energy Projects & Companies

The table below provides the current wind energy projects that have applied for registration under CDM (clean development mechanism, under the Kyoto Protocol) in various countries worldwide. As you can observe, not all projects in all the countries have applied for this, owing to a number of reasons.

Wind CDM* Projects (As of May 2008)

Country

# of Projects

MW

India

183

3818

PR China

191

9934

Mexico

10

1172

South Korea

9

287

Brazil

7

436

Dominican Republic

3

173

Phillippines

2

73

Morocco

2

70

Cyprus

2

44

Egypt

1

120

Panama

1

81

Mongolia

1

50

Jamaica

1

21

Costa Rica

1

20

Colombia

1

20

Israel

1

12

Argentina

1

11

Chile

1

19

Nicaragua

1

20

Vietnam

1

30

Ecuador

1

2

Total

421

16410

                                    Source: 2007 Global Wind Report

*: Clean Development Mechanism

Highlights from the above table:

  1. India’s individual project capacities are much smaller than those of most other countries. On average, each wind project in India has about 21 MW, while for China it is 52 MW and for countries such as Egypt and Mexico, it is over 100 MW.
  2. India and China together constitute over 80% of the total installed capacity under these projects. 

Largest Wind Projects Operating in the U.S. (MW)

Wind farm

Size (MW)

Project owner

Horse Hollow, TX

736

FPL Energy

Sweetwater, TX

585

Babcock & Brown, Catamount

Peetz Table, CO

401

FPL Energy

Capricorn Ridge, TX

364

FPL Energy

Buffalo Gap, TX

353

AES

Source: AWEA 2008 Annual Rankings Report, www.awea.org/

Note: Horse Hollow, completed in 2006, remains the largest single wind farm in operation in the U.S. for the second year. All of the top five wind farms are located in the Southwest, where large projects continue to be built.