Gasch R., Twele J. (Eds.) Wind Power Plants: Fundamentals, Design, Construction and Operation

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1.1 Wind Energy in the year 2010

Fig 1-2 Wind energy utilisation, total installed capacity in MW [1, 2]

Denmark

The wind energy renaissance started in Denmark in 1980. Against the background

of the oil crises in 1973 and 1978, small companies – mostly manufacturers of

rural machinery and equipment – developed the first generation of wind turbines for

commercial use. These wind turbines had rotor diameters of 10 to 15 meters, and

generator capacities of 30 to 55 kW (see Fig. 1-1). The electricity not consumed

by the turbine owner was fed directly into the grid. Changes in energy policy

guaranteed that turbine owners would receive a fair and fixed price for excess

electricity. This policy change created a market for renewable energy. By 2007,

25 % of the electricity consumed in Denmark was produced by wind turbines.

Since 2003 Denmark´s wind development has taken place primarily offshore.

Although Denmark led the world in cumulative installed wind capacity in the

1990s, Denmark now ranks only 10

behind market leaders such as China, United

States, Germany, Spain and others.

The United States of America

The US wind energy boom in California began in 1980/81. The boom resulted in a

total installed capacity of 1,600 MW by 1987. Californian wind farms employed

large numbers of small turbines (35 to 75 kW) that were either manufactured in

the US or imported from Denmark. As in Denmark, the extreme rise of oil prices

in the 70s led the government to favour renewable energies, including solar, wind

1 Introduction to Wind Energy

and geothermal technologies. As a result, commercial solar-thermal power plants,

with a total capacity of 350 MW were constructed in California. These positive

trends were stopped, however, when the Democratic Governor of California, Jerry

Brown, lost his majority to the Republicans in 1987. With the oil crisis subsiding,

the new governor changed the energy laws to favour the cheapest offer. Fossil-

fuelled power plants, with their large CO

and greenhouse gas emissions, once

again became the predominant power generation technology. By 2001, however,

wind energy had begun to make a comeback in the US, and impressive 9,922 MW

of new capacity was installed in 2009.

Germany

Germany did not experience rapid wind market growth until 1991. In that year, a

federal law called the Electricity Feed Law (EFL) guaranteed both grid access and

a fair, fixed-price to wind energy generators. During the next eight years, 3,000

MW of new capacity came online. By 1998, the coastal provinces of Niedersachsen

and Schleswig-Holstein supplied about 7 % of their electricity demand through

wind power. Ten years later, this share had increased to 40 %. The Renewable

Energy Law (REL), which came into force in April 2000, and replaced the EFL,

encouraged the development of inland sites and laid the regulatory groundwork

for offshore installations. Following this legislation, a record for new installations

was set in 2002 with 3,247 MW. The market has cooled somewhat, with between

1,500 MW and 2,000 MW installed each year since 2002. There are high expecta-

tions, however, for market growth offshore in the future. .

Spain

There has been a rapid increase in the number of wind turbines in Spain during the

past few years. In 2010, yearly installations amounted to 1,516 MW. The total in-

stalled capacity had increased to 20,676 MW. Spain is considered one of Europe’s

fastest growing markets.

India

India has experienced a wind energy boom since 1993. Although few turbines had

been installed by 1990, 200 MW had been installed by 1994. By 1998, this num-

ber had increased to 1,000 MW, and by 2010, India’s installed capacity reached

13,065 MW. This development has been fuelled by India’s enormous electricity

demand. Government and industry want to use wind farms to end the frequent

industrial production stoppages caused by electricity shortages.

1.2 The Demand for Electricity

China

China´s wind market recorded (new installations 16,500 MW) the highest growth

rates in the world in 2009 of 113 % (see Fig. 1-3), leaving the country total

installed capacity 42,287 MW at the end of 2010. Beside this, in the northern

grasslands of the country (Inner Mongolia), about 150.000 wind powered battery-

chargers are used by nomadic groups. These wind turbines have an average capa-

city of approximately 100 Watts.

25%

50%

75%

100%

125%

2001 2002 2003 2004 2005 2006 2007 2008 2009

China

India

Germany

Spain

Fig 1-3 Growth rates in top 5 most important markets

1.2 The Demand for Electricity

Since the demand for energy, and specifically electricity, has increased so dra-

matically over the last 100 years (Fig 1-4), it has now become important to con-

sider the environmental impacts of energy production. In the past, high standards

of living and “modern lifestyles” were based on increased energy consumption.

Today, statistics from highly developed countries show that standards of living

can increase independently of energy consumption if energy efficiency measures

are introduced.

In 2008, the global demand for electricity was about 20.2 10

kWh. This

demand was met mainly through fossil fuels and nuclear power (see Fig. 1-5).

Renewable energies, other than hydropower, only had a 2.8 % share. This marks a

slight increase compared to 1999, despite to fast increasing total demand.

1 Introduction to Wind Energy

100%

200%

300%

400%

500%

600%

700%

800%

900%

1000%

1100%

1200%

1300%

1400%

1900 1920 1940 1960 1980 2000

electricity consumption

population

Fig. 1-4 Development of world-wide population and consumption of electricity [3]

1950 = 100%; population = 2.55 10

; annual electricity consumption = 1.2 10

kWh

gaz

21,3%

coal

41,0%

nuclear

13,5%

oil

5,5%

hydro

15,9%

other

renewables

2,8%

Fig 1-5 Share of the global electricity supply in 2008 [3]

The large increase in electrical energy demand has strongly influenced global

energy market projections. Using statistics from 2003 to 2008, Fig. 1-6 shows that

countries with expanding populations and growing economies have experienced

enormous growth in electricity consumption. Highly developed industrial coun-

tries, however, have started to limit their energy consumption, without decreasing

their living standards, by encouraging energy conservation and energy-efficient

technologies.

1.2 The Demand for Electricity

Country Population

2008

Consumpt

ion of

electricity

2008

Annual

consumpti

on per

capita

2008

Growth rate

of popula-

tion

2003 - 2008

Growth rate

of electricity

consumption

2003 - 2008

Million TWh /

year

kWh /

cap. p.a.

% p.a. % p.a.

Germany 82.1 587.0 7150 - 0.10 0.62

USA 304.5 4155.9 13648 0.92 1.85

China 1325.6 3252.3 2453 0.58 15.84

India 1140.0 645.3 566 1.42 7.85

Fig 1-6 Consumption of electricity in representative countries (2003-2008) [3, 4]

While meeting the growing demand for energy, it is imperative to take the envi-

ronmental impacts of the various energy technologies into account (see Fig 1-7).

Continued use of the current resource mix will contribute further to global warm-

ing and will lead ultimately to climatic disaster.

ash

nuclear

waste

energy resource

g/kWh g/kWh g/kWh g/kWh mg/kWh

Carbon

(with

pollution

control)

977

(977)

5 – 9

(0.8)

3 – 6

(0.8)

(0.1)

Oil

(with

pollution

control)

730

(730)

1 - 4.2

(0.8)

2 – 5

(0.8)

(0.1)

fossil fuels

gas

(with

pollution

control)

419

(419)

0.05

(0.01)

2 – 4

(0.7)

(0.01)

nuclear 4

DEWI [5]

Strauß [6]

refers to 1% sulphur in the oil

Heitmann [7]

Fig 1-7 Comparison of the environmental impact of different fossil and non-fossil fuel energy

resources. The values in brackets ( ) are obtained using modern pollution control technologies.

An increased reliance on the energy from the wind, water and sun will decrease

the chance of environmental disaster since renewables do not emit greenhouse

gasses, and obviously produce no nuclear waste.

Furthermore, wind energy is not a land-intensive energy technology, which has

become an important point of discussion in increasingly crowded northern

1 Introduction to Wind Energy

European countries. Fig. 1-8 shows land used by wind energy in terms of power

produced per square meter when compared to other types of power stations.

Site Data

Hydropower Itaipu, 1985

(Brazil)

Spiez, 1986

(Switzerland)

12.600 MW

H = 200 m

23 MW

H = 65 m

6 W / m

70 W / m

(per m

flooded area)

Brown coal

(lignite)

fired plants

Schkopau, 1996

(Germany)

Schwarze Pumpe, 1998

(Germany)

Buschhaus, 1985

(Germany)

1.000 MW

1.600 MW

380 MW

8 W / m

16 W / m

31 W / m

(per m

mining area)

Wind power

plants

Germany v

Wind

= 4.5-

6.0 m/s

50 - 120 W / m

(per m

rotor area)

foundation area is 10

times less

Fig. 1-8 Electrical power produced per square meter land use

There are other advantages to renewable energies besides the fact that they emit

no greenhouse gases, and are less land intensive than conventional fuels. Within a

few months, renewable energy plants are able to produce enough energy to pay

back the amount of energy used to manufacture them. This so-called energy amor-

tisation is shown in Fig 1-9.

Wind Solar Water

4.5

m/s

5.5

m/s

6.5

m/s

Mono Multi Amorph Large Small Micro

Energy

amortis

ation

(in

months)

6 -

4 -

2 -

28 -

19 -

14 - 28

5 - 6

8 - 9

9 - 11

Fig 1-9 Energy amortisation of different renewable energy sources [8]

The economic benefits associated with a decentralised energy supply, e.g. job

creation, create an opportunity for sustainable development that strengthens local

economies. Compared with an energy supply based on large and centralised con-

ventional power stations, a decentralised energy supply creates steady local

employment, because of:

- jobs created by the planning and construction of the plants

- the craftsmanship involved (i.e. the installation of solar thermal or

PV plants)

1.2 The Demand for Electricity

- the higher rate of employment per kWh associated with the operation

- and maintenance (O&M) of renewable energy plants.

Fig.1-10 shows the average cost of electricity generation from newly built power

plants. The total cost varies from 0.036 € / kWh, for electricity generated by gas-

driven power plants, to 0.057 € / kWh for nuclear and wind power plants.

wind (0.057 € / kWh)

0,0%

17,5%

82,5%

coal (0.046 € / kWh)

37,0%

18,5%

44,6%

gaz (0.036 € / kWh)

33,8%

52,1%

14,1%

capital costs

fuel costs O & M

nuclear (0.057 € / kWh)

69,9%

14,2%

15,9%

wind (0.057 € / kWh)

0,0%

17,5%

82,5%

coal (0.046 € / kWh)

37,0%

18,5%

44,6%

gaz (0.036 € / kWh)

33,8%

52,1%

14,1%

capital costscapital costs

fuel costsfuel costs O & MO & M

nuclear (0.057 € / kWh)

69,9%

14,2%

15,9%

Fig. 1-10 Cost distribution for different power sources [9]

For the different types of electricity generation, these costs are distributed among

three categories:

- capital costs - the total upfront investment

- fuel costs

- costs of operation and maintenance (O&M costs)

Though capital costs are lower for fossil fuel plants than they are for nuclear or

wind plants, fuel costs are higher.

The Kyoto Protocol is the first attempt to limit carbon dioxide emissions

through an international convention. Wind energy, and other renewable energy

sources, provide a way to meet increasing energy demand without compromising

the environment and contributing to climatic disaster. Fig.1-11 is a scenario,

1 Introduction to Wind Energy

200

400

600

800

1000

1200

1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010 2020 2030 2040

Exajoules

renewable energies (wind, solar, hydro and biomass)

taditional resources (fossile fuels, traditional biomass and nuclear)

forecast

200

400

600

800

1000

1200

1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010 2020 2030 2040

Exajoules

renewable energies (wind, solar, hydro and biomass)

taditional resources (fossile fuels, traditional biomass and nuclear)

forecastforecast

Fig. 1-11 A scenario for meeting future global energy demand [10]

The next section will illustrate how policy can be used to encourage renewable

energy use.

1.3 Energy Policy and Governmental Instruments

When analysing wind energy markets, two principal market types can be identi-

fied: those where governmental support is motivated by environmental concerns

(e.g. Europe) and those where governmental support is based on energy need (e.g.

Asia) (see Fig. 1-12).

Environment-driven markets Energy-driven markets

- No need for additional capacity

- Financing available

- Wind energy only contributes a

small part of total energy supply

- Desire and obligation to reduce CO

- Wind energy development is not

very sensitive to variations in

international fuel prices

- Immediate need for additional

energy - capacity shortfall

- Shortage of foreign currency

- Dependant on importing fossil fuels

- Moderate to high economic growth

- Need for technology transfer and

local production

- Very sensitive to variations in inter

national fuel prices

Fig. 1-12 Typical markets for wind energy [9]

1.3 Energy Policy and Governmental Instruments

Political instruments

In order to open up markets for renewable energy, a supportive policy framework

is necessary. The following list shows the range of policy mechanisms typically

used to stimulate the use of renewable energy:

- Public funds for R&D programs

- Public funds for demonstration projects

- Direct subsidies of investment costs (% of total costs or an amount

per kW installed)

- Guaranteeing premium prices for electricity from wind turbines (an

amount per kWh delivered)

- Financial incentives – special loans, favourable interest rates, etc.

- Tax incentives i.e. favourable depreciation

An analysis of the development in different markets shows that an appropriate

mixture of several policies directly affects market growth. Planning security is es-

sential to wind energy market growth. This allows investors to calculate turnover

and profit over a wind power plant’s life time -- i.e. for 20 years.

Fig. 1-13 compares the wind energy policies of European governments. Some

countries guarantee a fixed price to wind power, like Germany through Renewable

Energy Feed-In Tariffs (FITs), while other countries employ a bidding system that

sets a fixed yearly quota for new capacity that is to be installed. Obviously, coun-

tries with a guaranteed price per kWh fed into the grid (Germany, Spain) have

stimulated their markets more than those operating with capacity quotas.

Fig. 1-13 Overview of governmental instruments and their effects in some European markets

The liberalisation of the European energy market will affect the development of

renewable energies in the future. But liberalisation will not benefit the environ-

ment unless it is combined with penalties for CO

emissions and/or the production

1 Introduction to Wind Energy

of nuclear waste. This penalty could be enacted through a tax on conventional en-

ergies. Such a tax would encourage renewable energies to become competitive

without the use of subsidies.

Fig 1-14. gives a summary of the wind power capacity installed in Europe at

the end of 2010.

27214

20676

3752

2237

5797

5204

2163

1208

1428

3702

1011

5660

197

441

911

215

1107

462

27214

20676

3752

2237

5797

5204

2163

1208

1428

3702

1011

5660

197

441

911

215

1107

462

27214

20676

3752

2237

5797

5204

2163

1208

1428

3702

1011

5660

197

441

911

215

1107

462

Fig.1-14 Installed wind power capacity in Europe at the end of 2010 [2]

1.4 Technological development

The following columns of words summarise the debate between competing wind

power plant design options during the last two decades:

- 3-bladed rotor - 2-bladed rotor

- constant rotational speed - variable rotational speed

- stall control - pitch control

- induction generator - synchronous generator

- electrical excited synchronous - permanent magnetic synchronous

generator generator

- gearbox - no gearbox, direct drive

- glass fibre blades - metal, wooden blades

- direct grid connection - ac-dc-ac conversion

- hydraulic actuators - electrical actuators