**Albedo Effect and Energy Efficiency of Cities**

Aniceto Zaragoza Ramírez1 and César Bartolomé Muñoz2

*1Polytechnic University of Madrid 2Spanish Cement Association Spain*

#### **1. Introduction**

The United Nations, by means of the Intergovernmental Panel on Climate Change (IPCC), establishes in the Fourth Assessment Report, Working Group I, that warming of the climate system is unequivocal and that most of the observed increment in global average temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations.

European Union considers that the average surface temperature of the Earth should not be exceeded in more than 2ºC with respect to preindustrial levels in order to avoid negative consequences of global warming. With this purpose, CO2 concentration should be kept below 450 ppmv.

The International Energy Agency (IEA) predicts an important increment of primary energy demand until 2030. The electricity generation sector expects that world's demand gets duplicated, which would mean the installation of new plants up to an additional global capacity of 5,000 GWe. This huge increment of the demand, together with other economic factors, will give fossil fuels (coal, gas and oil) a key role within the energy field.

The IPCC Third and Fourth Assessment Reports state that no individual measure by itself will be able to reduce the necessary amount of greenhouse gases emissions, but a global approach will be required. In this context, energy efficiency is considered the most relevant measure to achieve the objectives.

Despite energy efficiency shows the highest potential as a mitigation measure, the influence of the albedo of cities on global warming is not mentioned in IPCC reports, focusing on other aspects such as: thermal envelope, heating systems, co-generation and efficiency lighting systems, which are also of paramount importance, but no as powerful as albedo effect.

#### **2. Albedo effect**

#### **2.1 Background**

Looking backwards into History, we can fix the first human energy revolution when human beings abandoned the caves where they lived and set up stable settlements where new houses were built. Inside caves, the temperature was almost constant independently from the external temperature and acclimatization needs were negligible. However, new houses required new measures to keep their temperature acceptable for life.

Albedo Effect and Energy Efficiency of Cities 5

Fig. 3. Solar radiation intensity (Source: http://www.ez2c.de/ml/solar\_land\_area)

more important in the near future.

**2.2 Earth radiation and albedo** 

droughts and hurricanes.

reflected by Earth's surface (8% approx.).

the energy flows entering and leaving the Earth are balanced.

This portion of the planet includes ¾ parts of World's population and, in consequence, these measures would have a large impact not only in developed societies, but also in developing countries from Asia or South America, where the demand of energy will become more and

The atmosphere of the Earth is fully transparent to visible light, but much less to infrared radiation. This is the reason why almost 58% of solar light that our planet receives reaches its surface, from which 50% is absorbed by the Earth. The rest of the radiation coming from the Sun is absorbed by the atmosphere (20% approx.), reflected by clouds (22% approx.) or

The energy absorbed by the Earth makes it getting warm and then emitting this heat as infrared radiation, which heats up the atmosphere until it reaches a temperature at which

The presence in the Earth's atmosphere of water vapour, methane, CO2 and other greenhouse gases, which are nearly impermeable to infrared radiation, keep the energy emitted in such a way, increasing the equilibrium temperature in comparison with the temperature in the absence of these gases. This effect is desirable, since otherwise the temperature of the Earth would be too low (-18 or -19ºC) for life. However, the excessive concentration of GHG has resulted into an unusual increment of atmospheric temperature and consequently into a climate change that will modify rain distribution around the Earth, will increase the frequency of extreme atmospheric phenomena and will cause more floods,

The first approach from the international community to face this problem consisted of reducing the emission of GHG so that the infrared radiation emitted by the Earth is not

Fig. 1. Reductions in energy-related CO2 emissions in different climate-policy scenarios (*Source: International Energy Agency, 2010*)

Fires were lighted inside houses during winter in order to protect themselves against cold. However, no air conditioning system was available for summer and our ancestors resorted to passive measures: increasing the width of walls and painting facades in light colours.

The construction of white buildings is a simple and economical bioclimatic measure to save energy, since they reflect a higher amount of solar radiation and, therefore, these buildings are cooler in summer. On the other hand, these houses are not able to absorb solar energy during winter time and they have a greater demand of heat. For this reason, we only find this kind of buildings within latitudes where solar radiation reaches a minimum value.

Fig. 2. White buildings in a town in the South of Spain

Although this value is not scientifically fixed, the experience has established that these measures are effective within latitudes under 40º, both in the north and south hemispheres, where the Earth radiation is, on average, over 225 W/m2.

Sustainable Development – 4 Energy, Engineering and Technologies – Manufacturing and Environment

Fig. 1. Reductions in energy-related CO2 emissions in different climate-policy scenarios

Fires were lighted inside houses during winter in order to protect themselves against cold. However, no air conditioning system was available for summer and our ancestors resorted to passive measures: increasing the width of walls and painting facades in light colours.

The construction of white buildings is a simple and economical bioclimatic measure to save energy, since they reflect a higher amount of solar radiation and, therefore, these buildings are cooler in summer. On the other hand, these houses are not able to absorb solar energy during winter time and they have a greater demand of heat. For this reason, we only find this kind of buildings within latitudes where solar radiation reaches a minimum value.

Although this value is not scientifically fixed, the experience has established that these measures are effective within latitudes under 40º, both in the north and south hemispheres,

(*Source: International Energy Agency, 2010*)

Fig. 2. White buildings in a town in the South of Spain

where the Earth radiation is, on average, over 225 W/m2.

Fig. 3. Solar radiation intensity (Source: http://www.ez2c.de/ml/solar\_land\_area)

This portion of the planet includes ¾ parts of World's population and, in consequence, these measures would have a large impact not only in developed societies, but also in developing countries from Asia or South America, where the demand of energy will become more and more important in the near future.

#### **2.2 Earth radiation and albedo**

The atmosphere of the Earth is fully transparent to visible light, but much less to infrared radiation. This is the reason why almost 58% of solar light that our planet receives reaches its surface, from which 50% is absorbed by the Earth. The rest of the radiation coming from the Sun is absorbed by the atmosphere (20% approx.), reflected by clouds (22% approx.) or reflected by Earth's surface (8% approx.).

The energy absorbed by the Earth makes it getting warm and then emitting this heat as infrared radiation, which heats up the atmosphere until it reaches a temperature at which the energy flows entering and leaving the Earth are balanced.

The presence in the Earth's atmosphere of water vapour, methane, CO2 and other greenhouse gases, which are nearly impermeable to infrared radiation, keep the energy emitted in such a way, increasing the equilibrium temperature in comparison with the temperature in the absence of these gases. This effect is desirable, since otherwise the temperature of the Earth would be too low (-18 or -19ºC) for life. However, the excessive concentration of GHG has resulted into an unusual increment of atmospheric temperature and consequently into a climate change that will modify rain distribution around the Earth, will increase the frequency of extreme atmospheric phenomena and will cause more floods, droughts and hurricanes.

The first approach from the international community to face this problem consisted of reducing the emission of GHG so that the infrared radiation emitted by the Earth is not

Albedo Effect and Energy Efficiency of Cities 7

On average, the albedo of the planet is 0.35. That is to say 35% of all the solar energy is reflected while 65% is absorbed. However, it must be pointed out that polar ice, with its high albedo plays an important role in maintaining this balance. Should the polar ice melt, the average albedo of the Earth will fall because the oceans will absorb more heat than the ice.

Humans act on Earth's surface, mainly by means of construction works, usually decreasing its albedo. Pavements and building's roofs are the most exposed surfaces to solar radiation among typical construction works and they must become the objective of any measure aiming at increasing energy efficiency by means of the application of the albedo effect. In this sense, there exist at the moment construction materials that are lighter than the natural surface of the Earth. Its utilization would increase the global albedo, reducing, this way, the

Asphalt albedo ranges from about 0.05 to 0.20 (Akbari and Thayer, 2007), depending on the age and makeup of the asphalt. Its albedo typically increases somewhat as its colour fades with age. A typical concrete has an albedo of about 0.35 to 0.40 when constructed; these values can decrease to about 0.25 to 0.30 with normal usage. With the incorporation of slag or white cement, a concrete pavement can exhibit albedo readings as high as 0.70. As shown in Figure 5, concrete has a significantly higher albedo than asphalt, either new or old. In fact, concrete usually has a higher albedo than almost every other material that is typical to

urban areas, including grass, trees, coloured paint, brick/stone and most roofs.

Fig. 5. Albedo ranges of various surfaces typical to urban areas *(Source: NASA, Akbari and* 

As previously mentioned, the albedo effect has a significant influence on climate change since approximately 50% of the solar radiation reaches the Earth's surface, where it will be

amount of solar energy absorbed by our planet.

**3. Influence of albedo on global warming** 

*Thayer, 2007)*

Fig. 4. Earth radiation Budget (Source: Kiehl and Trenberth, 1997)

retained in the atmosphere. Nevertheless, there exist other fields that have not been exploited yet, at least at a global scale, whose influence on global warming would be relevant. Increasing the reflectivity of the Earth's surface would decrease the absorption of solar energy, thus, emitting less infrared radiation and cooling the atmosphere. This action is cheap and means no significant changes in production processes, thus, permitting an immediate and fast deployment.

Earth's surface naturally reflects approximately 8% (not considering the poles) (Kiehl and Trenberth, 1997) of the total solar energy it receives. This reflection is conditioned by the colour of the surface: the lighter the more energy it reflects and vice versa.

The albedo or reflection coefficient is the diffuse reflectivity or reflecting power of a surface. It is defined as the ratio of reflected radiation from the surface to incident radiation upon it. A surface that absorbs all the energy it receives (black surface) has an albedo of 0, whereas a perfect reflector (white surface) has an albedo of 1.


Typical albedo of different kind of surfaces and materials are shown in table 1:

Table 1. Typical albedo values of different kind of surfaces and materials *(Source: European Concrete Paving Association, 2009)*

Sustainable Development – 6 Energy, Engineering and Technologies – Manufacturing and Environment

retained in the atmosphere. Nevertheless, there exist other fields that have not been exploited yet, at least at a global scale, whose influence on global warming would be relevant. Increasing the reflectivity of the Earth's surface would decrease the absorption of solar energy, thus, emitting less infrared radiation and cooling the atmosphere. This action is cheap and means no significant changes in production processes, thus, permitting an

Earth's surface naturally reflects approximately 8% (not considering the poles) (Kiehl and Trenberth, 1997) of the total solar energy it receives. This reflection is conditioned by the

The albedo or reflection coefficient is the diffuse reflectivity or reflecting power of a surface. It is defined as the ratio of reflected radiation from the surface to incident radiation upon it. A surface that absorbs all the energy it receives (black surface) has an albedo of 0, whereas a

Surface **Albedo Surface Albedo**  Fresh snow 81 - 88 % Old snow 65 – 81 % Ice 30 – 50 % Rock 20 – 25 % Woodland 5 – 15 % Exposed soil 35 % Oceans 5 – 10 % Concrete 15 -25 %

Table 1. Typical albedo values of different kind of surfaces and materials *(Source: European* 

Fig. 4. Earth radiation Budget (Source: Kiehl and Trenberth, 1997)

colour of the surface: the lighter the more energy it reflects and vice versa.

Typical albedo of different kind of surfaces and materials are shown in table 1:

immediate and fast deployment.

perfect reflector (white surface) has an albedo of 1.

Asphalt 2 – 10 %

*Concrete Paving Association, 2009)*

On average, the albedo of the planet is 0.35. That is to say 35% of all the solar energy is reflected while 65% is absorbed. However, it must be pointed out that polar ice, with its high albedo plays an important role in maintaining this balance. Should the polar ice melt, the average albedo of the Earth will fall because the oceans will absorb more heat than the ice.

Humans act on Earth's surface, mainly by means of construction works, usually decreasing its albedo. Pavements and building's roofs are the most exposed surfaces to solar radiation among typical construction works and they must become the objective of any measure aiming at increasing energy efficiency by means of the application of the albedo effect. In this sense, there exist at the moment construction materials that are lighter than the natural surface of the Earth. Its utilization would increase the global albedo, reducing, this way, the amount of solar energy absorbed by our planet.

Asphalt albedo ranges from about 0.05 to 0.20 (Akbari and Thayer, 2007), depending on the age and makeup of the asphalt. Its albedo typically increases somewhat as its colour fades with age. A typical concrete has an albedo of about 0.35 to 0.40 when constructed; these values can decrease to about 0.25 to 0.30 with normal usage. With the incorporation of slag or white cement, a concrete pavement can exhibit albedo readings as high as 0.70. As shown in Figure 5, concrete has a significantly higher albedo than asphalt, either new or old. In fact, concrete usually has a higher albedo than almost every other material that is typical to urban areas, including grass, trees, coloured paint, brick/stone and most roofs.

Fig. 5. Albedo ranges of various surfaces typical to urban areas *(Source: NASA, Akbari and Thayer, 2007)*

#### **3. Influence of albedo on global warming**

As previously mentioned, the albedo effect has a significant influence on climate change since approximately 50% of the solar radiation reaches the Earth's surface, where it will be

Albedo Effect and Energy Efficiency of Cities 9

World's population has had a steady trend to urban concentration from the last century. In 1900, the ratio of people who lived in cities represented the 10% of global population, whereas in 2007 United Nations estimated that urban population already exceeded rural people. Projections predict the same trend for the future and, therefore, present situation of

One of the main difficulties that cities will have to face in the future is the energy supply. Despite only representing 2 percent of the world's surface area, cities are responsible for 75 percent of the world's energy consumption. London, for example, requires a staggering 125

London's population is around 7.4 million, so it is nowhere near megacity status yet, but according to the Tyndall Centre, it already consumes more energy than Ireland (and the

A great amount of this energy consumed by cities comes from residential uses, mainly from

**ENERGY CONSUMPTION BY SECTOR**

Residential Industry Transport Agriculture Commercial and public services Other

For this reason, it is essential to adopt measures aiming at reducing energy consumption of buildings within cities. Thermal insulation systems are continuously improving, electrical appliances are becoming more and more efficient and the utilization of energy-efficient light

Fig. 7. World's energy consumption by sector *(Source: International Energy Agency, 2009)*

**Residential; 27,50%**

**Industry; 31,90%**

**4. The albedo and the cities** 

acclimatization of buildings.

**Transport; 25,20%**

bulbs is increasing.

**Agriculture; 2,50%**

**Commercial and public services; 7,80%**

**4.1 Energy demand of cities and buildings** 

cities will worsen and new problems will arise.

times its own area in resources to sustain itself (New Scientist, 2009)

**Other; 5,10%**

same amount as Greece or Portugal) (New Scientist, 2009).

either absorbed or reflected, depending on its albedo. The more radiation the Earth absorbs, the hotter it becomes, favouring global warming.

Nonetheless, this global warming effect can be slowed down by applying our knowledge, namely by providing more reflective surfaces.

The "Heat Island Group", a research group from Berkeley, California, compared the albedo effect and the influence of the concentration of atmospheric CO2 on the net radiation power responsible for global warming. They calculated that an increase by one percent of the albedo of a surface corresponds to a reduction in radiation of 1.27 W/m2. This reduction in radiation has the effect of slowing global warming. Their calculations indicate that delay in warming is equivalent to a reduction in CO2 emissions of 2.5 kg per m2 of the Earth's surface.

According to these results, the potential of this measure would be at the same level as increasing renewable energies up to 20% of the energy mix or implementing CCS technologies in power and industrial plants. Additionally, the cost of this measure would be much more economical. As construction works are continuously being carried out around the World, especially in developing countries where the deficit of infrastructures is considerable, this measure could be easily applied either by using lighter construction materials or by painting surfaces in white or other light colours. Whereas the latter means an extra cost from paint, the former could be deployed at the same price or even cheaper.

Fig. 6. Past and future evolution of worldwide population (Source: Population Division of the Department of Economic and Social Affairs of the United Nations Secretariat, World Population Prospects: The 2006 Revision and World Urbanization Prospects: The 2007 Revision)

#### **4. The albedo and the cities**

Sustainable Development – 8 Energy, Engineering and Technologies – Manufacturing and Environment

either absorbed or reflected, depending on its albedo. The more radiation the Earth absorbs,

Nonetheless, this global warming effect can be slowed down by applying our knowledge,

The "Heat Island Group", a research group from Berkeley, California, compared the albedo effect and the influence of the concentration of atmospheric CO2 on the net radiation power responsible for global warming. They calculated that an increase by one percent of the albedo of a surface corresponds to a reduction in radiation of 1.27 W/m2. This reduction in radiation has the effect of slowing global warming. Their calculations indicate that delay in warming is equivalent to a reduction in CO2 emissions of 2.5 kg per m2 of the Earth's

According to these results, the potential of this measure would be at the same level as increasing renewable energies up to 20% of the energy mix or implementing CCS technologies in power and industrial plants. Additionally, the cost of this measure would be much more economical. As construction works are continuously being carried out around the World, especially in developing countries where the deficit of infrastructures is considerable, this measure could be easily applied either by using lighter construction materials or by painting surfaces in white or other light colours. Whereas the latter means an extra cost from paint, the former could be deployed at the same price or even cheaper.

**EVOLUTION OF GLOBAL POPULATION (IN THOUSANDS)**

1950 1960 1970 1980 1990 2000 2010 2020 2030 2040 2050

RURAL POPULATION URBAN POPULATION

Fig. 6. Past and future evolution of worldwide population (Source: Population Division of the Department of Economic and Social Affairs of the United Nations Secretariat, World Population Prospects: The 2006 Revision and World Urbanization Prospects: The 2007

the hotter it becomes, favouring global warming.

namely by providing more reflective surfaces.

surface.

0

1000000

Revision)

2000000

3000000

4000000

5000000

6000000

7000000

#### **4.1 Energy demand of cities and buildings**

World's population has had a steady trend to urban concentration from the last century. In 1900, the ratio of people who lived in cities represented the 10% of global population, whereas in 2007 United Nations estimated that urban population already exceeded rural people. Projections predict the same trend for the future and, therefore, present situation of cities will worsen and new problems will arise.

One of the main difficulties that cities will have to face in the future is the energy supply. Despite only representing 2 percent of the world's surface area, cities are responsible for 75 percent of the world's energy consumption. London, for example, requires a staggering 125 times its own area in resources to sustain itself (New Scientist, 2009)

London's population is around 7.4 million, so it is nowhere near megacity status yet, but according to the Tyndall Centre, it already consumes more energy than Ireland (and the same amount as Greece or Portugal) (New Scientist, 2009).

A great amount of this energy consumed by cities comes from residential uses, mainly from acclimatization of buildings.

Fig. 7. World's energy consumption by sector *(Source: International Energy Agency, 2009)*

For this reason, it is essential to adopt measures aiming at reducing energy consumption of buildings within cities. Thermal insulation systems are continuously improving, electrical appliances are becoming more and more efficient and the utilization of energy-efficient light bulbs is increasing.

Albedo Effect and Energy Efficiency of Cities 11

**HISTORIC MAXIMUM TEMPERATURES IN MADRID DOWNTOWN AND SURROUNDINGS**

1974

1976

1978

any surface (see figure 10)

rise of the demand of energy.

**4.3 Strategy for cities** 

1980

1982

Agencia Estatal de Meteorología, Spain)

1984

1986

1988

island effect, particularly in arid climates with high radiation levels.

efforts must be made in order to take advantage of this powerful tool.

1990

1992

Fig. 9. Maximum average temperatures in Madrid downtown and surroundings (Source:

energetic balance. Pavements are quantitatively important urban components in what is referred to the horizontal surface exposed to solar radiation (20% of the urban ground approximately) (Rose et al., 2003) and generally they have a high absorptivity and a high thermal capacity. These characteristics made significant contributions to the urban heat

This effect can be easily appreciated in a thermal photography that gives the temperature of

The heat absorbed during the day coming from solar radiation is emitted at night to the relatively cold night sky. The result is the increment of the average temperature within cities in approximately 5ºC, which has a negative effect, mainly during summer time and in those areas where the air conditioning needs are high. The immediate result will be a dramatic

Increasing the albedo of the Earth's surface has a positive effect against global warming independently of the place where this increment is achieved. However, the effect of lightening the surfaces inside cities is much higher due to the indirect effect on urban heat islands and on acclimatization needs. For this reason, it must be in cities where greater

Light roofs and facades have a direct effect on energy demand of buildings. When receiving solar radiation, these buildings reflect more light and, therefore, absorb less energy, thus,

1994

1996

1998

2000

2002

Madrid Downtown Madrid Surroundings

However, there exist measures that are not being considered and whose impact would be much higher than the impact of traditional solutions. Cement and concrete are in the core of these innovative measures, since they can increase the reflectivity of cities, helping to reduce the ambient temperature and, in consequence, the air conditioning needs.

#### **4.2 Urban heat islands**

An urban heat island (UHI) is a metropolitan area which is significantly warmer than its surrounding rural areas. This effect is more noticeable during the night than during the day and it is more apparent when the winds are weak. Seasonally, UHI is seen in both summer and winter.

Fig. 8. Distribution of temperatures due to urban heat island effect (European Concrete Paving Association, 2009)

In the case of Madrid (Spain), two meteorological stations were chosen: one in the city centre, near Retiro Park, and another in Barajas, where the airport is placed. The distance between both stations is less than 15 kilometres, but the difference of temperatures reaches 8ºC. Although Madrid is a dense city where this effect is deeper, it can also be noticed in any other city where building concentration and dark pavements produce this effect.

There are several causes for urban heat islands. The main reason is the modification of the environment by human being, introducing new materials that absorb more heat than natural ones. The solar radiation absorbed by the urban construction materials highly affects the temperature distribution inside cities. The thermo physical properties of these materials, especially the albedo and the infrared emissivity, have an important impact in their Sustainable Development – 10 Energy, Engineering and Technologies – Manufacturing and Environment

However, there exist measures that are not being considered and whose impact would be much higher than the impact of traditional solutions. Cement and concrete are in the core of these innovative measures, since they can increase the reflectivity of cities, helping to reduce

An urban heat island (UHI) is a metropolitan area which is significantly warmer than its surrounding rural areas. This effect is more noticeable during the night than during the day and it is more apparent when the winds are weak. Seasonally, UHI is seen in both summer

Fig. 8. Distribution of temperatures due to urban heat island effect (European Concrete

other city where building concentration and dark pavements produce this effect.

In the case of Madrid (Spain), two meteorological stations were chosen: one in the city centre, near Retiro Park, and another in Barajas, where the airport is placed. The distance between both stations is less than 15 kilometres, but the difference of temperatures reaches 8ºC. Although Madrid is a dense city where this effect is deeper, it can also be noticed in any

There are several causes for urban heat islands. The main reason is the modification of the environment by human being, introducing new materials that absorb more heat than natural ones. The solar radiation absorbed by the urban construction materials highly affects the temperature distribution inside cities. The thermo physical properties of these materials, especially the albedo and the infrared emissivity, have an important impact in their

the ambient temperature and, in consequence, the air conditioning needs.

**4.2 Urban heat islands** 

Paving Association, 2009)

and winter.

Fig. 9. Maximum average temperatures in Madrid downtown and surroundings (Source: Agencia Estatal de Meteorología, Spain)

energetic balance. Pavements are quantitatively important urban components in what is referred to the horizontal surface exposed to solar radiation (20% of the urban ground approximately) (Rose et al., 2003) and generally they have a high absorptivity and a high thermal capacity. These characteristics made significant contributions to the urban heat island effect, particularly in arid climates with high radiation levels.

This effect can be easily appreciated in a thermal photography that gives the temperature of any surface (see figure 10)

The heat absorbed during the day coming from solar radiation is emitted at night to the relatively cold night sky. The result is the increment of the average temperature within cities in approximately 5ºC, which has a negative effect, mainly during summer time and in those areas where the air conditioning needs are high. The immediate result will be a dramatic rise of the demand of energy.

#### **4.3 Strategy for cities**

Increasing the albedo of the Earth's surface has a positive effect against global warming independently of the place where this increment is achieved. However, the effect of lightening the surfaces inside cities is much higher due to the indirect effect on urban heat islands and on acclimatization needs. For this reason, it must be in cities where greater efforts must be made in order to take advantage of this powerful tool.

Light roofs and facades have a direct effect on energy demand of buildings. When receiving solar radiation, these buildings reflect more light and, therefore, absorb less energy, thus,

Albedo Effect and Energy Efficiency of Cities 13

reducing the inner temperature. As a result of this, the energy demand for acclimatization

Additionally, pavements can also be lighter, which means increasing the global albedo of

Both measures have an indirect effect in cities. Higher albedo means less energy absorption, which helps to combat urban heat islands, reducing the ambient temperature and the energy

There are more advantages coming from the increase of albedo, which is not only accompanied with lower surface temperatures and lower energy use, but also with lower CO2, NOx, VOC and ozone levels. Besides, the probability of smog formation decreases 5%

The most important human action on environments is, with high probability, road construction. Transport has become one of the principal activities of human being and road transport represents 85% of this activity. The consequence has been the construction of more than 30 million kilometres of roads (International Road Federation, 2006), of which 20.3 million kilometres are paved. There are other constructions that also modify the Earth's surface: railways, dams, airports, etc, but their magnitude is far from road construction. This

The principal material used in road pavement construction is asphalt, to the point that more than 95% of roads worldwide are built with this material. As the albedo of asphalt ranges between 5 and 10% (European Concrete Paving Association, 2009), whereas the albedo of exposed soil can be fixed in 35% (European Concrete Paving Association, 2009), the result is an absolute reduction of 25% in the albedo of the surface occupied by the road. Although it has not been quantified, researches carried out in Berkeley have proved that this action have

Lightening asphalt or substituting it by other lighter materials (i.e. concrete) would have the contrary effect. This action would not only reduce the global albedo of the planet but it would increase it in those areas where road runs along forests or other surfaces with

Assuming an average width for paved roads of 10 metres, we can estimate the influence of lightening road pavements on global warming by the application of the following equation:

*TER A ER ES*

ΔA = Increment of Earth albedo by asphalt-concrete substitution in roads ER = Equivalent reduction in CO2 emissions per m2 per 1% increment of albedo

ΔA can be calculated by the application of the equation:

the Earth and reflecting a higher amount of solar energy into the space.

for every 0.25°C fall in daily maximum temperatures above 21°C.

is the reason why the quantification is only focused on roads.

purposes of the building also decreases.

consumption for air conditioning.

**5. Quantification of albedo effect 5.1 Potential of global albedo effect** 

a significant impact on global warming.

medium albedo values.

where:

ES= Earth surface

Fig. 10. Temperatures distribution on top of surfaces built by human being (Source: "Concrete roads: a smart and sustainable choice", European Concrete Paving Association, 2009)

Fig. 11. Direct and direct effects of increasing the albedo of cities (*Source: H. Akbari, 2009*)

Sustainable Development – 12 Energy, Engineering and Technologies – Manufacturing and Environment

Fig. 10. Temperatures distribution on top of surfaces built by human being (Source: "Concrete roads: a smart and sustainable choice", European Concrete Paving Association,

Fig. 11. Direct and direct effects of increasing the albedo of cities (*Source: H. Akbari, 2009*)

2009)

reducing the inner temperature. As a result of this, the energy demand for acclimatization purposes of the building also decreases.

Additionally, pavements can also be lighter, which means increasing the global albedo of the Earth and reflecting a higher amount of solar energy into the space.

Both measures have an indirect effect in cities. Higher albedo means less energy absorption, which helps to combat urban heat islands, reducing the ambient temperature and the energy consumption for air conditioning.

There are more advantages coming from the increase of albedo, which is not only accompanied with lower surface temperatures and lower energy use, but also with lower CO2, NOx, VOC and ozone levels. Besides, the probability of smog formation decreases 5% for every 0.25°C fall in daily maximum temperatures above 21°C.

#### **5. Quantification of albedo effect**

#### **5.1 Potential of global albedo effect**

The most important human action on environments is, with high probability, road construction. Transport has become one of the principal activities of human being and road transport represents 85% of this activity. The consequence has been the construction of more than 30 million kilometres of roads (International Road Federation, 2006), of which 20.3 million kilometres are paved. There are other constructions that also modify the Earth's surface: railways, dams, airports, etc, but their magnitude is far from road construction. This is the reason why the quantification is only focused on roads.

The principal material used in road pavement construction is asphalt, to the point that more than 95% of roads worldwide are built with this material. As the albedo of asphalt ranges between 5 and 10% (European Concrete Paving Association, 2009), whereas the albedo of exposed soil can be fixed in 35% (European Concrete Paving Association, 2009), the result is an absolute reduction of 25% in the albedo of the surface occupied by the road. Although it has not been quantified, researches carried out in Berkeley have proved that this action have a significant impact on global warming.

Lightening asphalt or substituting it by other lighter materials (i.e. concrete) would have the contrary effect. This action would not only reduce the global albedo of the planet but it would increase it in those areas where road runs along forests or other surfaces with medium albedo values.

Assuming an average width for paved roads of 10 metres, we can estimate the influence of lightening road pavements on global warming by the application of the following equation:

$$TER = \Delta A \times ER \times ES$$

where:

ΔA = Increment of Earth albedo by asphalt-concrete substitution in roads ER = Equivalent reduction in CO2 emissions per m2 per 1% increment of albedo ES= Earth surface

ΔA can be calculated by the application of the equation:

Albedo Effect and Energy Efficiency of Cities 15

However, recent researches (Lawrence Berkeley National Laboratory in California, 2009) suggest that urban areas cover between 1.2 to 2.4% of the Earth's land mass. Paved areas in 100 of the world's largest cities cover an area of about 525 billion m2. By using lighter pavements and roofs, it is possible to increase the albedo of urban surfaces in the world's top 100 cities up to 15%. The goal is to positively impact energy use, as well as to reduce

Typical reflectivity of roof fabric is low, especially in residential sector. The average albedo of roofs can be estimated between 10 and 25%. It is possible to increase the albedo of roofs either by using new lighter materials or by placing a white covering on top of current roofs. In case these measures are applied, reflectivity of roofs is estimated to reach 55-60%, which means an absolute increment of 30%. Regarding pavements, long term albedo could be

A study carried out in the United States (Rose et al. 2003) estimated that the total surface occupied by roofs in urban areas is 20% and it can reach up to 25% in dense cities. The same study establishes that the percentage of paved surfaces ranges between 29 and 44%. Since the ratio of surface for vegetation purposes in American areas exceeds the world's average, it can be stated that the ratio of urban surface occupied either by roofs or by pavements is 20

> **Vegetation** 28 % **Roofs** 20 % **Pavements** 40 % **Other** 12%

Table 3. Distribution of surfaces by type inside cities (Source: Rose et al. 2003, partially

Assuming previous figures, an absolute increment of 0.10 in the reflectivity of albedo inside

*Roof* 0,30 20% 0,06 *Pavement* 0,10 40% 0,04

Table 4. Increment of global albedo of cities due to the increment of roofs and pavements

So far, assessing the influence of a 10% increment of albedo of cities has been extremely complicated because numerical models could only use a minimum square grid of 250 km sideway for the evaluation. Computational developments now permit reducing the size of

**albedo Surface ratio Total increment** 

Total 0,10

smog formation, CO2 levels, and ultimately, global warming.

The distribution of surfaces by type inside cities is shown in table 3:

**Potential increment of** 

increased in a 10%.

and 40% respectively.

cities can be achieved (see table 4)

modified)

reflectivity

$$
\Delta A = \frac{PS}{ES} \times \Delta NA
$$

where:

PS = Total paved surface

ΔNA = Difference in albedo between asphalt and concrete

The results of the calculation are shown in table 2:


Table 2. Calculation of global albedo effect estimated in equivalent CO2 emissions

The potential reduction of atmosphere temperature thanks to the substitution of road asphalt by lighter materials is equivalent to withdrawing from the atmosphere 7.6 G tons, which represents 25% of total emissions of CO2 in 2010 (International Energy Agency, 2010)

Obviously, it is not feasible to lighten all paved roads around the World, since the cost of this action is unaffordable. However, this result should make the society focus on the implementation of this measure. In this sense, new roads and preservation works should become a powerful tool against global warming.

#### **5.2 Potential of albedo effect inside cities**

Quantifying the effect of an increment of the albedo inside cities is much more complicated than quantifying the global effect coming from lightening road pavements, mainly due to indirect effects. The principal benefit of increasing the albedo of cities comes from the partial elimination of heat islands, which is difficult to evaluate.

Sustainable Development – 14 Energy, Engineering and Technologies – Manufacturing and Environment

*PS A NA ES* 

**PARAMETER VALUE SOURCE** 

Wikipedia http://en.wikipedia.org/ wiki/Earth

Total length of paved roads 20,301,039 km IRF Statistics, 2006 Average width of roads 10 m Estimated Total paved surface 203,104 km2 Calculated

Ratio paved surface/total surface 0.04 % Calculated Albedo of asphalt 10% EUPAVE, 2010 Albedo of concrete 25% EUPAVE, 2010

and concrete 15% Calculated

concrete substitution in roads 0,006 % Calculated

concrete substitution 7.6 GTn CO2 Calculated

Table 2. Calculation of global albedo effect estimated in equivalent CO2 emissions

per m2 per 1% increment of albedo 2.5 kg/m2 Heat Island Group, 2009

The potential reduction of atmosphere temperature thanks to the substitution of road asphalt by lighter materials is equivalent to withdrawing from the atmosphere 7.6 G tons, which represents 25% of total emissions of CO2 in 2010 (International Energy Agency, 2010) Obviously, it is not feasible to lighten all paved roads around the World, since the cost of this action is unaffordable. However, this result should make the society focus on the implementation of this measure. In this sense, new roads and preservation works should

Quantifying the effect of an increment of the albedo inside cities is much more complicated than quantifying the global effect coming from lightening road pavements, mainly due to indirect effects. The principal benefit of increasing the albedo of cities comes from the partial

where:

PS = Total paved surface

ΔNA = Difference in albedo between asphalt and concrete

Earth's surface 510,072,000 km2

The results of the calculation are shown in table 2:

Difference in albedo between asphalt

Increment of Earth albedo by asphalt-

Equivalent reduction in CO2 emissions

Total equivalent reduction by asphalt-

become a powerful tool against global warming.

elimination of heat islands, which is difficult to evaluate.

**5.2 Potential of albedo effect inside cities** 

However, recent researches (Lawrence Berkeley National Laboratory in California, 2009) suggest that urban areas cover between 1.2 to 2.4% of the Earth's land mass. Paved areas in 100 of the world's largest cities cover an area of about 525 billion m2. By using lighter pavements and roofs, it is possible to increase the albedo of urban surfaces in the world's top 100 cities up to 15%. The goal is to positively impact energy use, as well as to reduce smog formation, CO2 levels, and ultimately, global warming.

Typical reflectivity of roof fabric is low, especially in residential sector. The average albedo of roofs can be estimated between 10 and 25%. It is possible to increase the albedo of roofs either by using new lighter materials or by placing a white covering on top of current roofs. In case these measures are applied, reflectivity of roofs is estimated to reach 55-60%, which means an absolute increment of 30%. Regarding pavements, long term albedo could be increased in a 10%.

A study carried out in the United States (Rose et al. 2003) estimated that the total surface occupied by roofs in urban areas is 20% and it can reach up to 25% in dense cities. The same study establishes that the percentage of paved surfaces ranges between 29 and 44%. Since the ratio of surface for vegetation purposes in American areas exceeds the world's average, it can be stated that the ratio of urban surface occupied either by roofs or by pavements is 20 and 40% respectively.


The distribution of surfaces by type inside cities is shown in table 3:

Table 3. Distribution of surfaces by type inside cities (Source: Rose et al. 2003, partially modified)

Assuming previous figures, an absolute increment of 0.10 in the reflectivity of albedo inside cities can be achieved (see table 4)


Table 4. Increment of global albedo of cities due to the increment of roofs and pavements reflectivity

So far, assessing the influence of a 10% increment of albedo of cities has been extremely complicated because numerical models could only use a minimum square grid of 250 km sideway for the evaluation. Computational developments now permit reducing the size of

Albedo Effect and Energy Efficiency of Cities 17

global warming up to 45%(calculated in this report), which would have an equivalent

Obviously, it is not possible to reach these figures in the short term. Increasing the reflectivity of roofs means placing white materials on top of current buildings and using innovative solutions for new buildings. In the same way, increasing the albedo of pavements means covering all asphalt pavements with other construction materials, mainly

Besides, the actual effect of increasing reflectivity of construction works is not precisely defined. For this reason, it is essential to perform research and demonstration projects to deeply study and evaluate the differences between traditional and new cities with cool roofs

Increasing the reflectivity of urban areas and also of interurban paved roads might have the same effect as the rest of measures considered for combating global warming all together: energy efficiency of industrial processes, CCS technologies, nuclear power plants, renewable sources of energy, etc. This is the reason why increasing albedo of construction materials

*"Combat Global Warming",* pavements4life.com, American Concrete Pavement Association,

*"Energy efficiency in buildings, transforming the market",* World Business Council for

*"Energy Technology Perspectives: Scenarios & strategy to 2050", International Energy Agency,* 

H. Akbari, S. Menon and A. Rosenfeld, *"Global cooling: effect of urban albedo on global* 

H. Akbari and R. Levinson, *"Status of cool roofs standards in the united States*", 2nd PALENC

H. Akbari, *"Global Cooling: increasing worldwide urban albedo to offset CO2"*, Fifth Annual

H. Akbari, M. Pomerantz and H. Taha, "Cool surfaces and shade trees to reduce energy use

I. Ben Hamadi, P. Pouezat and A. Bastienne, "The IRF World Road Statistics", International

L. Rens, *"Concrete roads: a smart and sustainable choice",* European Concrete Paving

*temperature*", 2nd PALENC Conference and 28th AIVC Conference on Building Low energy Cooling and Advance Ventilation Technologies in the 21st Century,

Conference and 28th AIVC Conference on Building Low energy Cooling and

and improve air quality in urban areas", Solar Energy, vol. 70, N.3, Great Britain,

economic saving of more than 500 billion Euros per year during the next 60 years.

concrete (whitetopping) and building new pavements of cities with concrete.

and pavements, quantifying potential benefits and profits.

should be included as a mitigation measure in IPCC reports.

Sustainable Development, Switzerland, 2009.

Road Federation, Switzerland, 2006.

Association, Brussels, 2009.

*European Directive 2002/91/CE: "Directive on the Energy Performance of Buildings"*

Advance Ventilation Technologies in the 21st Century, 2007.

California Climate Change Conference, Sacramento, CA, 2009.

**7. References** 

2007.

2007.

2001.

*OECD/IEA, Paris, 2010*

the grid up to 50-100 km and even less for urban areas. These powerful models predict a fall of global temperature of 0,03 ºC under these assumptions (H. Akbari, 2009):


In case the first assumption is changed and, instead of a perfect reflectivity, a 10% increment of the albedo is considered, the reduction of the global temperature would be 0,01 ºC annually (H. Akbari, 2009). Taking into account that United Nations predict an increment of global temperature of 3ºC in the next 60 years (0,05 ºC per year), the conclusion is that substituting current roof and asphalt pavements by cool roofs and concrete pavements would slow down global warming by 20%.

World's current rate of CO2 emissions is about 30 G tons/year (International Energy Agency, 2010). World's rate of CO2 emissions averaged over next 60 years is estimated at 50 G tons/year (International Energy Agency, 2008). Hence, the 20% delay in global warming is worth 10 G ton CO2 annually.

#### **5.3 Economic impact**

Although economic evaluation of certain measures is always difficult because of the volatility of prices, net potential savings coming from the direct effect on buildings (cooling energy savings minus heating energy penalties) have been estimated in excess of one billion Euros only in United States (H. Akbari, 2007).

Additionally, partial elimination of heat islands would make cities cooler and would improve the quality of air, thus indirectly reducing the consumption of energy for air conditioning (Taha 2002, Taha 2001, Taha et al. 2000, Rosenfeld et al. 1998; Akbari et al. 2001, Pomerantz et al. 1999). Savings of energy and better quality of air would mean a 2 billion Euros profit per year only in United States.

At the moment, the price of a CO2 ton in European emissions market is around 13 €. This price is relatively low due to the current economic and financial crisis. However, it is estimated to rise up to 30 € in the short term. Substituting asphalt by lighter materials in world's paved roads would have the same effect as abating 7,6 G tons of CO2 per year (calculated in this report). Global effect on cities, direct and indirect effect would be equivalent to abating 10 G tons annually (H. Akbari, 2009). The estimated cost (emissions trading) of both effects in the middle term could reach 528 billion Euros.

#### **6. Conclusions**

Results presented in this report show the social and environmental advantages of increasing the reflectivity of roofs and pavements inside cities and in interurban roads. Actually, the potential benefits of this measure are much higher than other actions that are considered as a priority by United Nations and other international organizations.

Increasing urban albedo in a 10% would allow saving up to 3 billion Euros in electricity only in the United States (H. Akbari, 2009) thanks to direct effects and also to the elimination of urban heat islands. Additionally, its influence on global temperature could slow down Sustainable Development – 16 Energy, Engineering and Technologies – Manufacturing and Environment

the grid up to 50-100 km and even less for urban areas. These powerful models predict a fall

In case the first assumption is changed and, instead of a perfect reflectivity, a 10% increment of the albedo is considered, the reduction of the global temperature would be 0,01 ºC annually (H. Akbari, 2009). Taking into account that United Nations predict an increment of global temperature of 3ºC in the next 60 years (0,05 ºC per year), the conclusion is that substituting current roof and asphalt pavements by cool roofs and concrete pavements

World's current rate of CO2 emissions is about 30 G tons/year (International Energy Agency, 2010). World's rate of CO2 emissions averaged over next 60 years is estimated at 50 G tons/year (International Energy Agency, 2008). Hence, the 20% delay in global warming

Although economic evaluation of certain measures is always difficult because of the volatility of prices, net potential savings coming from the direct effect on buildings (cooling energy savings minus heating energy penalties) have been estimated in excess of one billion

Additionally, partial elimination of heat islands would make cities cooler and would improve the quality of air, thus indirectly reducing the consumption of energy for air conditioning (Taha 2002, Taha 2001, Taha et al. 2000, Rosenfeld et al. 1998; Akbari et al. 2001, Pomerantz et al. 1999). Savings of energy and better quality of air would mean a 2 billion

At the moment, the price of a CO2 ton in European emissions market is around 13 €. This price is relatively low due to the current economic and financial crisis. However, it is estimated to rise up to 30 € in the short term. Substituting asphalt by lighter materials in world's paved roads would have the same effect as abating 7,6 G tons of CO2 per year (calculated in this report). Global effect on cities, direct and indirect effect would be equivalent to abating 10 G tons annually (H. Akbari, 2009). The estimated cost (emissions

Results presented in this report show the social and environmental advantages of increasing the reflectivity of roofs and pavements inside cities and in interurban roads. Actually, the potential benefits of this measure are much higher than other actions that are considered as

Increasing urban albedo in a 10% would allow saving up to 3 billion Euros in electricity only in the United States (H. Akbari, 2009) thanks to direct effects and also to the elimination of urban heat islands. Additionally, its influence on global temperature could slow down

trading) of both effects in the middle term could reach 528 billion Euros.

a priority by United Nations and other international organizations.

of global temperature of 0,03 ºC under these assumptions (H. Akbari, 2009):

2. The rest of the Earth's surface (98%) maintained its natural albedo.

would slow down global warming by 20%.

Euros only in United States (H. Akbari, 2007).

Euros profit per year only in United States.

is worth 10 G ton CO2 annually.

**5.3 Economic impact** 

**6. Conclusions** 

1. Urban areas (2% of total Earth's surface) are perfectly white (albedo equal to 1).

global warming up to 45%(calculated in this report), which would have an equivalent economic saving of more than 500 billion Euros per year during the next 60 years.

Obviously, it is not possible to reach these figures in the short term. Increasing the reflectivity of roofs means placing white materials on top of current buildings and using innovative solutions for new buildings. In the same way, increasing the albedo of pavements means covering all asphalt pavements with other construction materials, mainly concrete (whitetopping) and building new pavements of cities with concrete.

Besides, the actual effect of increasing reflectivity of construction works is not precisely defined. For this reason, it is essential to perform research and demonstration projects to deeply study and evaluate the differences between traditional and new cities with cool roofs and pavements, quantifying potential benefits and profits.

Increasing the reflectivity of urban areas and also of interurban paved roads might have the same effect as the rest of measures considered for combating global warming all together: energy efficiency of industrial processes, CCS technologies, nuclear power plants, renewable sources of energy, etc. This is the reason why increasing albedo of construction materials should be included as a mitigation measure in IPCC reports.

#### **7. References**


*Ocean and Mechanical Engineering Department, Florida Atlantic University* 

The development of cleaner and efficient energy technologies and the use of new and renewable energy sources will play an important role in the sustainable development of a future energy strategy. The promotion of renewable sources of energy and the development of cleaner and more efficient energy systems are a high priority, for security and diversification of energy supply, environmental protection, and social and economic

Sustainable energy is to provide the energy that meets the needs of the present without compromising the ability of future generations to meet their needs. Sustainable energy has two components: renewable energy and energy efficiency. Renewable energy uses renewable sources such biomass, wind, sun, waves, tides and geothermal heat. Renewable energy systems include wind power, solar power, wave power, geothermal power, tidal power and biomass based power. Renewable energy sources, such as wind, ocean waves, solar flux and biomass, offer emissions-free production of electricity and heat. For example, geothermal energy is heat from within the earth. The heat can be recovered as steam or hot water and use it to heat buildings or generate electricity. The solar energy can be converted into other forms of energy such as heat and electricity and wind energy is mainly used to generate electricity. Biomass is organic material made from plants and animals. Burning biomass is not the only way to release its energy. Biomass can be converted to other useable forms of energy, such as methane gas or transportation fuels, such as ethanol and biodiesel (clean alternative fuels). In addition to renewable energy, sustainable energy systems also include technologies that improve energy efficiency of systems using traditional non renewable sources. Improving the efficiency of energy systems or developing cleaner and efficient energy systems will slow down the energy demand growth, make deep cut in fossil fuel use and reduce the pollutant emissions. For examples, advanced fossil-fuel technologies could significantly reduce the amount of CO2 emitted by increasing the efficiency with which fuels are converted to electricity. Options for coal include integrated gasification combined cycle (IGCC) technology, ultra-supercritical steam cycles and pressurized fluidized bed combustion. For the transportation sector, dramatic reductions in CO2 emissions from transport can be achieved by using available and emerging energy-saving vehicle technologies and switching to alternative fuels such as biofuels (biodiesel, ethanol). For industrial applications, making greater use of waste heat, generating electricity on-site, and putting in place more efficient processes and equipment could minimize external energy demands from industry. Advanced process control and greater reliance on biomass

**1. Introduction** 

cohesion (International Energy Agency, 2006).

Chaouki Ghenai

*USA* 

*"Technology Roadmap: Energy efficient buildings: heating and cooling equipment", International Energy Agency, France, 2009.* **2** 

Chaouki Ghenai

*Ocean and Mechanical Engineering Department, Florida Atlantic University USA* 

#### **1. Introduction**

Sustainable Development – 18 Energy, Engineering and Technologies – Manufacturing and Environment

*"Technology Roadmap: Energy efficient buildings: heating and cooling equipment", International* 

The development of cleaner and efficient energy technologies and the use of new and renewable energy sources will play an important role in the sustainable development of a future energy strategy. The promotion of renewable sources of energy and the development of cleaner and more efficient energy systems are a high priority, for security and diversification of energy supply, environmental protection, and social and economic cohesion (International Energy Agency, 2006).

Sustainable energy is to provide the energy that meets the needs of the present without compromising the ability of future generations to meet their needs. Sustainable energy has two components: renewable energy and energy efficiency. Renewable energy uses renewable sources such biomass, wind, sun, waves, tides and geothermal heat. Renewable energy systems include wind power, solar power, wave power, geothermal power, tidal power and biomass based power. Renewable energy sources, such as wind, ocean waves, solar flux and biomass, offer emissions-free production of electricity and heat. For example, geothermal energy is heat from within the earth. The heat can be recovered as steam or hot water and use it to heat buildings or generate electricity. The solar energy can be converted into other forms of energy such as heat and electricity and wind energy is mainly used to generate electricity. Biomass is organic material made from plants and animals. Burning biomass is not the only way to release its energy. Biomass can be converted to other useable forms of energy, such as methane gas or transportation fuels, such as ethanol and biodiesel (clean alternative fuels). In addition to renewable energy, sustainable energy systems also include technologies that improve energy efficiency of systems using traditional non renewable sources. Improving the efficiency of energy systems or developing cleaner and efficient energy systems will slow down the energy demand growth, make deep cut in fossil fuel use and reduce the pollutant emissions. For examples, advanced fossil-fuel technologies could significantly reduce the amount of CO2 emitted by increasing the efficiency with which fuels are converted to electricity. Options for coal include integrated gasification combined cycle (IGCC) technology, ultra-supercritical steam cycles and pressurized fluidized bed combustion. For the transportation sector, dramatic reductions in CO2 emissions from transport can be achieved by using available and emerging energy-saving vehicle technologies and switching to alternative fuels such as biofuels (biodiesel, ethanol). For industrial applications, making greater use of waste heat, generating electricity on-site, and putting in place more efficient processes and equipment could minimize external energy demands from industry. Advanced process control and greater reliance on biomass

gross energy demand of the European Union to be contributed from renewable by 2010. In the last 25 years the global wind energy had been increasing drastically and at the end of 2009 total world wind capacity reached 159,213 MW. Wind power showed a growth rate of 31.7 %, the highest rate since 2001. The trend continued that wind capacity doubles every

In the year 2012, the wind industry is expected for the first time to offer 1 million jobs. The USA maintained its number one position in terms of total installed capacity and China became number two in total capacity, only slightly ahead of Germany, both of them with around 26,000 Megawatt of wind capacity installed. Asia accounted for the largest share of new installations (40.4 %), followed by North America (28.4 %) and Europe fell back to the third place (27.3 %). Latin America showed encouraging growth and more than doubled its installations, mainly due to Brazil and Mexico. A total wind capacity of 203,000 Megawatt will be exceeded within the year 2010. Based on accelerated development and further improved policies, world wide energy association WWEA increases its predictions and sees a global capacity of 1,900,000 Megawatt as possible by the year 2020 (World Wide Energy Association report, 2009). The world's primary energy needs are projected to grow by 56% between 2005 and 2030, by an average annual rate of 1.8% per year (European Wind Energy

A wind turbine is a rotary device that extracts the energy from the wind. The mechanical energy from the wind turbine is converted to electricity (wind turbine generator). The wind turbine can rotate through a horizontal (horizontal axis wind turbine – HAWT) or vertical (VAWT) axis. Most of the modern wind turbines fall in these two basic groups: HAWT and VAWT. For the HAWT, the position of the turbine can be either upwind or downwind. For the horizontal upwind turbine, the wind hits the turbine blade before it hits the tower. For the horizontal downwind turbine, the wind hits the tower first. The basic advantages of the vertical axis wind turbine are (1) the generator and gear box can be placed on the ground and (2) no need of a tower. The disadvantages of the VAWT are: (1) the wind speeds are very low close to ground level, so although you may save a tower, the wind speeds will be very low on the lower part of the rotor, and (2) the overall efficiency of the vertical axis wind turbine is not impressive (Burton et al., 2001). The main parts of a wind turbine parts (see

 **Blades**: or airfoil designed to capture the energy from the strong and fast wind. The blades are lightweight, durable and corrosion-resistant material. The best materials are

**Rotor**: designed to capture the maximum surface area of wind. The rotor rotates around

**Gear Box**: A gear box magnifies or amplifies the energy output of the rotor. The gear

**Generator:** The generator is used to produce electricity from the rotation of the rotor.

**Nacelle:** The nacelle is an enclosure that seals and protects the generator and gear box

three years. The wind sector employed 550,000 persons worldwide.

Agency, 2006)

Figure 1) are:

**2.1 Fundamental concept of wind turbine** 

composites of fiberglass and reinforced plastic.

from the other elements.

the generator through the low speed shaft and gear box.

box is situated directly between the rotor and the generator.

Generators come in various sizes, relative to the desired power output.

and biotechnologies for producing fuels, chemicals and plastics could further reduce energy use and CO2 emissions. Energy use in residential and commercial buildings can be substantially reduced with integrated building design. Insulation, new lighting technology and efficient equipment are some of the measures that can be used to cut both energy losses and heating and cooling needs. Solar technology, on-site generation of heat and power, and computerized energy management systems within and among buildings could offer further reductions in energy use and CO2 emissions for residential and commercial buildings.

This Chapter will focus on wind energy. Electric generation using wind turbines is growing very fast. Wind energy is a clean and efficient energy system but during all stages (primary materials production, manufacturing of wind turbine parts, transportation, maintenance, and disposal) of wind turbine life cycle energy was consumed and carbon dioxide CO2 can be emitted to the atmosphere. What is the dominant phase of the wind turbine life that is consuming more energy and producing more emissions? What can be done during the design process to reduce the energy consumption and carbon foot print for the wind turbine life cycle? The first part of this chapter will include a brief history about the wind energy, the fundamental concepts of wind turbine and wind turbine parts. The second part will include a life cycle analysis of wind turbine to determine the dominant phase (material, manufacturing, use, transportation, and disposal) of wind turbine life that is consuming more energy and producing more CO2 emissions.

#### **2. Wind energy**

The use of wind as an energy source begins in antiquity. Mankind was using the wind energy for sailing ships and grinding grain or pumping water. Windmills appear in Europe back in 12th century. Between the end of nineteenth and beginning of twentieth century, first electricity generation was carried out by windmills with 12 KW. Horizontal-axis windmills were an integral part of the rural economy, but it fell into disuse with the advent of cheap fossil-fuelled engines and then the wide spread of rural electrification. However, in twentieth century there was an interest in using wind energy once electricity grids became available. In 1941, Smith-Putnam wind turbine with power of 1.25 MW was constructed in USA. This remarkable machine had a rotor 53 m in diameter, full-span pitch control and flapping blades to reduce the loads. Although a blade spar failed catastrophically in 1945, it remains the largest wind turbine constructed for some 40 years (Acker and Hand, 1999). International oil crisis in 1973 lead to re-utilization of renewable energy resources in the large scale and wind power was among others. The sudden increase in price of oil stimulated a number of substantial government-funded programs of research, development and demonstration. In 1987, a wind turbine with a rotor diameter of 97.5 m with a power of 2.5MW was constructed in USA. However, it has to be noted that the problems of operating very large wind turbines, in difficult wind climates were underestimated. With considerable state support, many private companies were constructing much smaller wind turbines for commercial sales. In particular, California in the mid-1980's resulted in the installation of very large number of quite small (less than 100 KW) wind turbines. Being smaller they were generally easy to operate and also repair or modify. The use of wind energy was stimulated in 1973 by the increase of price of fossil-fuel and of course, the main driver of wind turbines was to generate electrical power with very low CO2 emissions to help limit the climate change. In 1997 the Commission of the European Union was calling for 12 percent of the Sustainable Development – 20 Energy, Engineering and Technologies – Manufacturing and Environment

and biotechnologies for producing fuels, chemicals and plastics could further reduce energy use and CO2 emissions. Energy use in residential and commercial buildings can be substantially reduced with integrated building design. Insulation, new lighting technology and efficient equipment are some of the measures that can be used to cut both energy losses and heating and cooling needs. Solar technology, on-site generation of heat and power, and computerized energy management systems within and among buildings could offer further reductions in energy use and CO2 emissions for residential and commercial buildings.

This Chapter will focus on wind energy. Electric generation using wind turbines is growing very fast. Wind energy is a clean and efficient energy system but during all stages (primary materials production, manufacturing of wind turbine parts, transportation, maintenance, and disposal) of wind turbine life cycle energy was consumed and carbon dioxide CO2 can be emitted to the atmosphere. What is the dominant phase of the wind turbine life that is consuming more energy and producing more emissions? What can be done during the design process to reduce the energy consumption and carbon foot print for the wind turbine life cycle? The first part of this chapter will include a brief history about the wind energy, the fundamental concepts of wind turbine and wind turbine parts. The second part will include a life cycle analysis of wind turbine to determine the dominant phase (material, manufacturing, use, transportation, and disposal) of wind turbine life that is consuming

The use of wind as an energy source begins in antiquity. Mankind was using the wind energy for sailing ships and grinding grain or pumping water. Windmills appear in Europe back in 12th century. Between the end of nineteenth and beginning of twentieth century, first electricity generation was carried out by windmills with 12 KW. Horizontal-axis windmills were an integral part of the rural economy, but it fell into disuse with the advent of cheap fossil-fuelled engines and then the wide spread of rural electrification. However, in twentieth century there was an interest in using wind energy once electricity grids became available. In 1941, Smith-Putnam wind turbine with power of 1.25 MW was constructed in USA. This remarkable machine had a rotor 53 m in diameter, full-span pitch control and flapping blades to reduce the loads. Although a blade spar failed catastrophically in 1945, it remains the largest wind turbine constructed for some 40 years (Acker and Hand, 1999). International oil crisis in 1973 lead to re-utilization of renewable energy resources in the large scale and wind power was among others. The sudden increase in price of oil stimulated a number of substantial government-funded programs of research, development and demonstration. In 1987, a wind turbine with a rotor diameter of 97.5 m with a power of 2.5MW was constructed in USA. However, it has to be noted that the problems of operating very large wind turbines, in difficult wind climates were underestimated. With considerable state support, many private companies were constructing much smaller wind turbines for commercial sales. In particular, California in the mid-1980's resulted in the installation of very large number of quite small (less than 100 KW) wind turbines. Being smaller they were generally easy to operate and also repair or modify. The use of wind energy was stimulated in 1973 by the increase of price of fossil-fuel and of course, the main driver of wind turbines was to generate electrical power with very low CO2 emissions to help limit the climate change. In 1997 the Commission of the European Union was calling for 12 percent of the

more energy and producing more CO2 emissions.

**2. Wind energy** 

gross energy demand of the European Union to be contributed from renewable by 2010. In the last 25 years the global wind energy had been increasing drastically and at the end of 2009 total world wind capacity reached 159,213 MW. Wind power showed a growth rate of 31.7 %, the highest rate since 2001. The trend continued that wind capacity doubles every three years. The wind sector employed 550,000 persons worldwide.

In the year 2012, the wind industry is expected for the first time to offer 1 million jobs. The USA maintained its number one position in terms of total installed capacity and China became number two in total capacity, only slightly ahead of Germany, both of them with around 26,000 Megawatt of wind capacity installed. Asia accounted for the largest share of new installations (40.4 %), followed by North America (28.4 %) and Europe fell back to the third place (27.3 %). Latin America showed encouraging growth and more than doubled its installations, mainly due to Brazil and Mexico. A total wind capacity of 203,000 Megawatt will be exceeded within the year 2010. Based on accelerated development and further improved policies, world wide energy association WWEA increases its predictions and sees a global capacity of 1,900,000 Megawatt as possible by the year 2020 (World Wide Energy Association report, 2009). The world's primary energy needs are projected to grow by 56% between 2005 and 2030, by an average annual rate of 1.8% per year (European Wind Energy Agency, 2006)

#### **2.1 Fundamental concept of wind turbine**

A wind turbine is a rotary device that extracts the energy from the wind. The mechanical energy from the wind turbine is converted to electricity (wind turbine generator). The wind turbine can rotate through a horizontal (horizontal axis wind turbine – HAWT) or vertical (VAWT) axis. Most of the modern wind turbines fall in these two basic groups: HAWT and VAWT. For the HAWT, the position of the turbine can be either upwind or downwind. For the horizontal upwind turbine, the wind hits the turbine blade before it hits the tower. For the horizontal downwind turbine, the wind hits the tower first. The basic advantages of the vertical axis wind turbine are (1) the generator and gear box can be placed on the ground and (2) no need of a tower. The disadvantages of the VAWT are: (1) the wind speeds are very low close to ground level, so although you may save a tower, the wind speeds will be very low on the lower part of the rotor, and (2) the overall efficiency of the vertical axis wind turbine is not impressive (Burton et al., 2001). The main parts of a wind turbine parts (see Figure 1) are:


 **Upwind/Downwind wind turbines designs:** The upwind wind turbines have the rotor facing the wind. The basic advantage of upwind designs is that one avoids the wind shade behind the tower. By far the vast majority of wind turbines have this design. The

 **Number of blades:** Most modern wind turbines are three-bladed designs with the rotor position maintained upwind using electrical motors in their yaw mechanism. The vast majority of the turbines sold in world markets have this design. The two-bladed wind turbine designs have the advantage of saving the cost of one rotor blade and its weight. However, they tend to have difficulty in penetrating the market, partly because they

 **Mechanical and aerodynamics noise:** sound emissions from wind turbines may have two different origins: Mechanical noise and aerodynamic noise. The mechanical noise originates from metal components moving or knocking against each other may originate in the gearbox, in the drive train (the shafts), and in the generator of a wind turbine. Sound insulation can be useful to minimise some medium- and high-frequency noise. In general, it is important to reduce the noise problems at the source, in the structure of the machine itself. The source of the aerodynamic sound emission is when the wind hits different objects at a certain speed, it will generally start making a sound. For example, rotor blades make a slight swishing sound at relatively low wind speeds. Careful design of trailing edges and very careful handling of rotor blades while they are

Commercial wind farms are constructed to generate electricity for sale through the electric power grid. The number of wind turbines on a wind farm can vary greatly, ranging from a single turbine to thousands. Large wind farms typically consist of multiple large turbines located in flat, open land. Small wind farms, such as those with one or two turbines, are often located on a crest or hill. The size of the turbines can vary as well, but generally they are in the range of 500 Kilowatts to several Megawatts, with 4.5 Megawatts being about the largest. Physically, they can be quite large as well, with rotor diameters ranging from 30 m to 120 m and tower heights ranging from 50 m to 100 m. The top ten wind turbine manufacturers, as measured by global market share in 2007 are listed in Table 1. Due to advances in manufacturing and design, the larger turbines are becoming more common. In general, a one Megawatt unit can produce enough electricity to meet the needs of about 100- 200 average homes. A large wind farm with many turbines can produce many times that amount. However, with all commercial wind farms, the power that is generated first flows

into the local electric transmission grid and does not flow directly to specific homes.

conversion mainly depends on the wind speed and the swept area of the turbine:

The Wind turbines work by converting the kinetic energy in the wind first into rotational kinetic energy in the turbine and then electrical energy. The wind power available for

(1)

downwind wind turbines have the rotor placed on the lee side of the tower.

require higher rotational speed to yield the same energy output.

mounted, have become routine practice in the industry.

**2.3 Wind farm** 

**2.4 Wind turbine power** 

 **Tower:** The tower of the wind turbine carries the nacelle and the rotor. The towers for large wind turbines may be either tubular steel towers, lattice towers, or concrete towers. The higher the wind tower, the better the wind. Winds closer to the ground are not only slower, they are also more turbulent. Higher winds are not corrupted by obstructions on the ground and they are also steadier.

Fig. 1. Wind turbine parts

#### **2.2 Wind turbine design**

During the design of wind turbines, the strength, the dynamic behavior, and the fatigue properties of the materials and the entire assembly need to be taken into consideration. The wind turbines are built to catch the wind's kinetic energy. Modern wind turbines are not built with a lot of rotor blades. Turbines with many blades or very wide blades will be subject to very large forces, when the wind blows at high speed. The energy content of the wind varies with the third power of the wind speed. The wind turbines are built to withstand extreme winds. To limit the influence of the extreme winds and to let the turbines rotates relatively quickly it is generally prefer to build turbines with a few, long, narrow blades.

 F**atigue Loads (forces)**: If the wind turbines are located in a very turbulent wind climate, they are subject to fluctuating winds and hence fluctuating forces. The components of the wind turbine such as rotor blades with repeated bending may develop cracks which ultimately may make the component break. When designing a wind turbine it is important to calculate in advance how the different components will vibrate, both individually, and jointly. It is also important to calculate the forces involved in each bending or stretching of a component (structural dynamics).

Sustainable Development – 22 Energy, Engineering and Technologies – Manufacturing and Environment

 **Tower:** The tower of the wind turbine carries the nacelle and the rotor. The towers for large wind turbines may be either tubular steel towers, lattice towers, or concrete towers. The higher the wind tower, the better the wind. Winds closer to the ground are not only slower, they are also more turbulent. Higher winds are not corrupted by

During the design of wind turbines, the strength, the dynamic behavior, and the fatigue properties of the materials and the entire assembly need to be taken into consideration. The wind turbines are built to catch the wind's kinetic energy. Modern wind turbines are not built with a lot of rotor blades. Turbines with many blades or very wide blades will be subject to very large forces, when the wind blows at high speed. The energy content of the wind varies with the third power of the wind speed. The wind turbines are built to withstand extreme winds. To limit the influence of the extreme winds and to let the turbines rotates relatively quickly it is generally prefer to build turbines with a few, long, narrow

 F**atigue Loads (forces)**: If the wind turbines are located in a very turbulent wind climate, they are subject to fluctuating winds and hence fluctuating forces. The components of the wind turbine such as rotor blades with repeated bending may develop cracks which ultimately may make the component break. When designing a wind turbine it is important to calculate in advance how the different components will vibrate, both individually, and jointly. It is also important to calculate the forces

involved in each bending or stretching of a component (structural dynamics).

obstructions on the ground and they are also steadier.

Fig. 1. Wind turbine parts

**2.2 Wind turbine design** 

blades.


#### **2.3 Wind farm**

Commercial wind farms are constructed to generate electricity for sale through the electric power grid. The number of wind turbines on a wind farm can vary greatly, ranging from a single turbine to thousands. Large wind farms typically consist of multiple large turbines located in flat, open land. Small wind farms, such as those with one or two turbines, are often located on a crest or hill. The size of the turbines can vary as well, but generally they are in the range of 500 Kilowatts to several Megawatts, with 4.5 Megawatts being about the largest. Physically, they can be quite large as well, with rotor diameters ranging from 30 m to 120 m and tower heights ranging from 50 m to 100 m. The top ten wind turbine manufacturers, as measured by global market share in 2007 are listed in Table 1. Due to advances in manufacturing and design, the larger turbines are becoming more common. In general, a one Megawatt unit can produce enough electricity to meet the needs of about 100- 200 average homes. A large wind farm with many turbines can produce many times that amount. However, with all commercial wind farms, the power that is generated first flows into the local electric transmission grid and does not flow directly to specific homes.

#### **2.4 Wind turbine power**

The Wind turbines work by converting the kinetic energy in the wind first into rotational kinetic energy in the turbine and then electrical energy. The wind power available for conversion mainly depends on the wind speed and the swept area of the turbine:

$$P\_W = \frac{1}{2}\rho A V^3 \tag{1}$$

life-cycle analysis (Ashby, 2005, Ashby et al., 207, Granta Design, 20090). The steps for life

1. Define the goal and scope of the assessment: Why do the assessment? What is the

2. Compile an inventory of relevant inputs and outputs: What resources are consumed?

4. Interpretation of the results of the inventory analysis and impact assessment phases in relation of the objectives of the study: What the result means? What is to be done about

The life cycle analysis studies examine energy and material flows in raw material acquisition; processing and manufacturing; distribution and storage (transport, refrigeration…); use; maintenance and repair; and recycling options (Gabi, 2008, Graedel,

The first step is to develop a tool that is approximate but retains sufficient discrimination to differentiate between alternative choices. A spectrum of levels of analysis exist, ranging from a simple eco-screening against a list of banned or undesirable materials and processes

The second step is to select a single measure of eco-stress. On one point there is some international agreement: the Kyoto Protocol committed the developed nations that signed it to progressively reduce carbon emissions, meaning CO2 (Kyoto Protocol, 1997). At the national level the focus is more on reducing energy consumption, but since this and CO2 production are closely related, they are nearly equivalent. Thus there is certain logic in basing design decisions on energy consumption or CO2 generation; they carry more conviction than the use of a more obscure indicator. We shall follow this route, using energy as our measure. The third step is to separate the contributions of the phases of life because subsequent action depends on which is the dominant one. If it is that a material production, then choosing a material with low "embodied energy" is the way forward. But if it is the use phase, then choosing a material to make use less energy-intensive is the right

For selection to minimize eco-impact we must first ask: which phase of the life cycle of the product under consideration makes the largest impact on the environment? The answer guides material selection. To carry out an eco-audit we need the bill of material, shaping or manufacturing process, transportation used of the parts of the final product, the duty cycle during the use of the product, and also the eco data for the energy and CO2 footprints of

The Life-Cycle Analysis has now become a vital sustainable development tool. It enables the major aspects of a product's environmental impact to be targeted, prioritization of any improvements to be made to processes, and a comparison of two products with the same

The eco audit or life cycle analyis and selection strategies for guiding the design are:

subject and which bit (s) of its life are assessed?

to a full LCA, with overheads of time and cost.

approach, even if it has a higher embodied energy.

function on the basis of their environmental profiles.

materials and manufacturing process.

(bill of materials) What are the emissions generated?

3. Evaluate the potential impacts associated with those inputs and outputs

cycale analysis are:

them?

1998, and Fiksel, 2009).


Table 1. Top ten wind commercial wind turbines manufactures in 2007

Where is the air density (Kg/m3), A is the swept area (m2) and V the wind speed (m/s). Albert Betz (German physicist) concluded in 1919 that no wind turbine can convert more than 16/27 (59.3%) of the kinetic energy of the wind into mechanical energy turning a rotor (Betz Limit or Betz). The theoretical maximum power efficiency of any design of wind turbine is 0.59 (Hau, 2000 and Hartwanger and Horvat, 2008). No more than 59% of the energy carried by the wind can be extracted by a wind turbine. The wind turbines cannot operate at this maximum limit. The power coefficient Cp needs to be factored in equation (1) and the extractable power from the wind is given by:

$$P = \frac{1}{2}C\_P \rho A V^3 \tag{2}$$

The Cp value is unique to each turbine type and is a function of wind speed that the turbine is operating in. In real world, the value of Cp is well below the Betz limit (0.59) with values of 0.35 - 0.45 for the best designed wind turbines. If we take into account the other factors in a complete wind turbine system (gearbox, bearings, generator), only 10-30% of the power of the wind is actually converted into usable electricity. The power coefficient Cp, defined as that the power extracted by rotor to power available in the wind is given by:

$$C\_p = \frac{P}{\frac{1}{\alpha} \rho A V^3} = \frac{Power \times \text{Extracted by Rotor}}{Power \, Avaailable \, in \, the \, \mathcal{V}\bar{v}nd} \tag{3}$$

#### **3. Life cycle analysis and selections strategies for guiding design**

The material life cycle is shown in Figure 2. Ore and feedstock, drawn from the earth's resources, are processed to give materials. These materials are manufactured into products that are used, and, at the end of their lives, discarded, a fraction perhaps entering a recycling loop, the rest committed to incineration or land-fill. Energy and materials are consumed at each point in this cycle (phases), with an associated penalty of CO2 , SOx, NOx and other emissions, heat, and gaseous, liquid and solid waste. These are assessed by the technique of Sustainable Development – 24 Energy, Engineering and Technologies – Manufacturing and Environment

Where is the air density (Kg/m3), A is the swept area (m2) and V the wind speed (m/s). Albert Betz (German physicist) concluded in 1919 that no wind turbine can convert more than 16/27 (59.3%) of the kinetic energy of the wind into mechanical energy turning a rotor (Betz Limit or Betz). The theoretical maximum power efficiency of any design of wind turbine is 0.59 (Hau, 2000 and Hartwanger and Horvat, 2008). No more than 59% of the energy carried by the wind can be extracted by a wind turbine. The wind turbines cannot operate at this maximum limit. The power coefficient Cp needs to be factored in equation (1)

The Cp value is unique to each turbine type and is a function of wind speed that the turbine is operating in. In real world, the value of Cp is well below the Betz limit (0.59) with values of 0.35 - 0.45 for the best designed wind turbines. If we take into account the other factors in a complete wind turbine system (gearbox, bearings, generator), only 10-30% of the power of the wind is actually converted into usable electricity. The power coefficient Cp, defined as

The material life cycle is shown in Figure 2. Ore and feedstock, drawn from the earth's resources, are processed to give materials. These materials are manufactured into products that are used, and, at the end of their lives, discarded, a fraction perhaps entering a recycling loop, the rest committed to incineration or land-fill. Energy and materials are consumed at each point in this cycle (phases), with an associated penalty of CO2 , SOx, NOx and other emissions, heat, and gaseous, liquid and solid waste. These are assessed by the technique of

that the power extracted by rotor to power available in the wind is given by:

**3. Life cycle analysis and selections strategies for guiding design** 

(2)

(3)

Table 1. Top ten wind commercial wind turbines manufactures in 2007

and the extractable power from the wind is given by:

life-cycle analysis (Ashby, 2005, Ashby et al., 207, Granta Design, 20090). The steps for life cycale analysis are:


The life cycle analysis studies examine energy and material flows in raw material acquisition; processing and manufacturing; distribution and storage (transport, refrigeration…); use; maintenance and repair; and recycling options (Gabi, 2008, Graedel, 1998, and Fiksel, 2009).

The eco audit or life cycle analyis and selection strategies for guiding the design are:

The first step is to develop a tool that is approximate but retains sufficient discrimination to differentiate between alternative choices. A spectrum of levels of analysis exist, ranging from a simple eco-screening against a list of banned or undesirable materials and processes to a full LCA, with overheads of time and cost.

The second step is to select a single measure of eco-stress. On one point there is some international agreement: the Kyoto Protocol committed the developed nations that signed it to progressively reduce carbon emissions, meaning CO2 (Kyoto Protocol, 1997). At the national level the focus is more on reducing energy consumption, but since this and CO2 production are closely related, they are nearly equivalent. Thus there is certain logic in basing design decisions on energy consumption or CO2 generation; they carry more conviction than the use of a more obscure indicator. We shall follow this route, using energy as our measure. The third step is to separate the contributions of the phases of life because subsequent action depends on which is the dominant one. If it is that a material production, then choosing a material with low "embodied energy" is the way forward. But if it is the use phase, then choosing a material to make use less energy-intensive is the right approach, even if it has a higher embodied energy.

For selection to minimize eco-impact we must first ask: which phase of the life cycle of the product under consideration makes the largest impact on the environment? The answer guides material selection. To carry out an eco-audit we need the bill of material, shaping or manufacturing process, transportation used of the parts of the final product, the duty cycle during the use of the product, and also the eco data for the energy and CO2 footprints of materials and manufacturing process.

The Life-Cycle Analysis has now become a vital sustainable development tool. It enables the major aspects of a product's environmental impact to be targeted, prioritization of any improvements to be made to processes, and a comparison of two products with the same function on the basis of their environmental profiles.

Table 2. Bill of Materials for the 2 MW Wind Turbines

Fig. 2. Material Life cycle analysis

#### **4. Results: Life cycle analysis of 2.0 MW wind turbine**

Life cycle analysis (LCA) of 2.0 MW wind turbine is presented in this chapter. The LCA addresses the energy use and carbon foot print for the five phases (materials, manufacturing, transportation, use and disposal) through the product life cycle (Martinnez et al., 2009 and Nalukowe et al., 2006). Power generation from wind turbine is a renewable and sustainable energy but in a life cycle perspective wind turbines consumes energy resources and causes emissions during the production of raw materials, manufacturing process, its use, transportation and disposal. In order to determine the impacts of power generation using wind turbine, all components needed for the production of electricity should be include in the analysis including the tower, nacelle, rotor, foundation and transmission.

The bill of materials for a 2 MW land-based turbine (Elsam Engineering, 2004, Nordex, 2004, and Visat, 2005) is listed in Table 2. Some energy is consumed during the turbine's life (expected to be 25 years), mostly in primary materials production, manufacturing processes, and transport associated with maintenance. The energy for the transportation of small and large parts of the wind turbine and the nergy used for maintenace was calculated from information on inspection and service visits in the Vestas report (Elsam Engineering, 2004, Nordex, 2004, and Visat, 2005) and estimates of distances travelled (entered under "Static" use mode as 200 hp used for 2 hours 3 days per year). The manufacturing process for the wind turbine parst are summarized in Table 3.

Sustainable Development – 26 Energy, Engineering and Technologies – Manufacturing and Environment

Fig. 2. Material Life cycle analysis

wind turbine parst are summarized in Table 3.

transmission.

**4. Results: Life cycle analysis of 2.0 MW wind turbine** 

Life cycle analysis (LCA) of 2.0 MW wind turbine is presented in this chapter. The LCA addresses the energy use and carbon foot print for the five phases (materials, manufacturing, transportation, use and disposal) through the product life cycle (Martinnez et al., 2009 and Nalukowe et al., 2006). Power generation from wind turbine is a renewable and sustainable energy but in a life cycle perspective wind turbines consumes energy resources and causes emissions during the production of raw materials, manufacturing process, its use, transportation and disposal. In order to determine the impacts of power generation using wind turbine, all components needed for the production of electricity should be include in the analysis including the tower, nacelle, rotor, foundation and

The bill of materials for a 2 MW land-based turbine (Elsam Engineering, 2004, Nordex, 2004, and Visat, 2005) is listed in Table 2. Some energy is consumed during the turbine's life (expected to be 25 years), mostly in primary materials production, manufacturing processes, and transport associated with maintenance. The energy for the transportation of small and large parts of the wind turbine and the nergy used for maintenace was calculated from information on inspection and service visits in the Vestas report (Elsam Engineering, 2004, Nordex, 2004, and Visat, 2005) and estimates of distances travelled (entered under "Static" use mode as 200 hp used for 2 hours 3 days per year). The manufacturing process for the


Table 2. Bill of Materials for the 2 MW Wind Turbines

Fig. 3. Life Cycle Analysis of Wind Turbine - With and Without Wind Turbine Material

Table 4. Energy and CO2 Footprint Summary – Wind Turbine

Recycling


Table 3. Manufacturing Processes

The net energy demands of each phase of life are summarized in Figure 3. The life cycle analysis was performed first without recycled wind turbine materials sent to landfill). The second analysis was performed with recycled wind turbine materials (the wind turbine materials that can be recycled were sent to recycling at the end life of the wind turbine). Figure 3 and Table 4 show clearly that the dominant phase that is consuming more energy and produccing more CO2 emisions is the material phase. More energy is consumed and high amount of CO2 is released in the atmosphere during the primary material production of the wind turbine parts. The second dominant phase is the manufacuring process when the parts of turbine are sent to landfill at the end life of the turbine. The results also show the benefits of recycling the materials at the end life of the wind turbine. If all the materials are sent to landfill at the end of life of the wind turbine, 2.18 E+011 J of energy (1.1 % of the total energy) is needed to process these materials and 13095.71 Kg of CO2 (0.9% increase of the total CO2) are released to the atmosphere at the end of life of the turbine. If the material of the wind turbine are recycled, a total energy of 6.85E+012 J representing 54.8% of the total energy is recovered at the end life of the material. A net reduction of C02 emissions by 495917.28 Kg (55.4% of the total CO2 emission) is obtained by recycling the wind turbine material (see Table 4).

Sustainable Development – 28 Energy, Engineering and Technologies – Manufacturing and Environment

Component **Manufacturing Process** 

**Tower structure** Forging, rolling

**Nacelle, gears** Forging, rolling **Nacelle, generator core** Forging, rolling **Nacelle, generator conductors** Forging, rolling **Nacelle, transformer core** Forging, rolling

**Nacelle, cover** Composite forming

**Rotor, blades** Composite forming

**Rotor, spinner** Composite forming

**Rotor, spinner** Casting **Foundations, pile & platform** Construction

**Foundations, steel** Forging, rolling

**Transmission, insulation** Polymer extrusion

The net energy demands of each phase of life are summarized in Figure 3. The life cycle analysis was performed first without recycled wind turbine materials sent to landfill). The second analysis was performed with recycled wind turbine materials (the wind turbine materials that can be recycled were sent to recycling at the end life of the wind turbine). Figure 3 and Table 4 show clearly that the dominant phase that is consuming more energy and produccing more CO2 emisions is the material phase. More energy is consumed and high amount of CO2 is released in the atmosphere during the primary material production of the wind turbine parts. The second dominant phase is the manufacuring process when the parts of turbine are sent to landfill at the end life of the turbine. The results also show the benefits of recycling the materials at the end life of the wind turbine. If all the materials are sent to landfill at the end of life of the wind turbine, 2.18 E+011 J of energy (1.1 % of the total energy) is needed to process these materials and 13095.71 Kg of CO2 (0.9% increase of the total CO2) are released to the atmosphere at the end of life of the turbine. If the material of the wind turbine are recycled, a total energy of 6.85E+012 J representing 54.8% of the total energy is recovered at the end life of the material. A net reduction of C02 emissions by 495917.28 Kg (55.4% of the

total CO2 emission) is obtained by recycling the wind turbine material (see Table 4).

**Nacelle, main shaft** Casting **Nacelle, other forged components** Forging, rolling **Nacelle, other cast components** Casting

**Rotor, iron components** Casting

**Transmission, conductors – Copper** Forging, rolling **Transmission, conductors – Aluminum** Forging, rolling

Table 3. Manufacturing Processes

**Tower, Cathodic Protection** Casting

**Nacelle, transformer conductors – Copper** Forging, rolling **Nacelle, transformer conductors – Aluminum** Forging, rolling

Fig. 3. Life Cycle Analysis of Wind Turbine - With and Without Wind Turbine Material Recycling



Table 4. Energy and CO2 Footprint Summary – Wind Turbine

The results of life cycle analysis of the 2.0 MW wind turbine show the problem with the energy consumed and carbon foot print was for the material phase. More energy and more emissions are produced during the primary material production of the wind turbine parts. The manufacturing process is the second dominant phase. The energy consumption and carbon foot print are negligible for the transportation and the use phases. The results also show clearly the benefits of recycling the wind turbine parts at the end of life. The life cycle analysis of the 2.0 MW wind turbine show that 54.8% of the total energy is recovered and a net reduction of C02 emissions by 55.4% is obtained by recycling the wind turbine materials

Acker, T.; Hand, M., (1999), "Aerodynamic Performance of the NREL Unsteady

Ashby, M.F., (2005) "Materials Selection in Mechanical Design", 3rd edition, Butterworth-

Ashby, M.F. Shercliff, H. and Cebon, D., (2007), "Materials: engineering, science, processing

Burton T., Sharpe D., Jenkins N. and Bossanyi E, (2001), Wind Energy Handbook, John

European Wind Energy Agency, VV.AA. Annual report. Technical report, EWEA, European

Fiksel, J., Design for Envirnment, (2009), A guide to sustianble product development,

Graedel, T.E., (1998), Streamlined life cycle assessment, prentice Hall, ISBN 0-13-607425-1 Granta Design Limited, Cambridge, (2009) (www.grantadesign.com), CES EduPack User

Hartwanger, D. and Horvat, (2008), A., 3D Modeling of a wind turbine using CFD, NAFEMS UK Conference, Cheltenham, United of Kingdom, June 10-11, 2008

Elsam Engineering A/S, (2004) "Life Cycle Assessment of Offshore and Onshore Sited Wind Farms", Report by Vestas Wind Systems A/S of the Danish Elsam Engineering International Energy Agency, VV.AA, (2006), Wind energy annual report, Technical report,

Kyoto protocol, United Nations, Framework Convention on Climate Change, (1997),

Martinnez E., Sanz, F., Pellegrini, s., Jimenez e., Blanco, j., (2009), Life cycle assessment of a multi-megawatt wind turbine, Renewable Energy 34 (2009) 667–673 Nalukowe B.B., Liu, J., Damien, W., and Lukawski, T., (2006), Life Cycle Assessment of a

and design", Butterworth Heinemann, Oxford UK, Chapter 20.

Aerodynamics Experiment (Phase IV) Twisted Rotor", AIAA-99-0045, Prepared for the 37th AIAA Aerospace Sciences Meeting and Exhibit, Reno, NV, January 11-14,

at the end of life of the wind turbine.

Heinemann, Oxford, UK, Chapter 16

McGraw Hill, ISBN 978-0-07-160556-4 Gabi, PE International, (2008), www.gabi-sofwtare.com

Wiley & Sons Ltd: Chichester.

Wind Energy Agency, 2006

Hau E, (2000), Wind turbines. Springer: Berlin.

IEA, International Energy Agency.

Wind Turbine, Report 1N1800

Document FCCC/CP 1997/7/ADD.1

Nordex N90 Technical Description, Nordex Energy (2004)

p. 211-221.

Guide

**6. References** 


Table 5. Construction Energy, Wind Turbine Energy Output and Energy Pay Back Time

The turbine is rated at 2 MW but it produces this power only with the right wind conditions. In a best case scenario the turbine runs at an average capacity factor of 40% giving an annual energy output of 7.0 x 106 kWhr /year. The total energy generated by the turbine over a 25 year life is 175 x 106 kWhr (see Table 5). The total energy generated by the turbine over 25 year life time is about 32.32 times the energy required to build and service it (5.41 106 kWhr) if the turbine materials are sent to landfill at the end of life of the turbine. If the materials are recycled, the total energy generated by the turbine over 25 year life time is about 50.43 times the energy required to build and service it (3.47 106 kWhr). With a wind turbine capacity factor of 40 %, the energy payback time is about 9.27 months if the wind turbine materials are sent to landfill at the end life of the turbine and is only 5.94 months if the materials are recycled. The results show clearly the benefits of recycling parts of the wind turbine at the end life of the turbine.

#### **5. Conclusions**

The development of cleaner and efficient energy technologies and the use of new and renewable energy sources will play an important role in the sustainable development of a future energy strategy. Power generation from wind turbine is a renewable and sustainable energy but in a life cycle perspective wind turbines consumes energy resources and causes emissions during the production of raw materials, manufacturing process, transportation of small and large parts of the wind turbines, maintenance, and disposal of the parts at the end life of the turbines. To determine the impacts of power generation using wind turbine, all components needed for the production of electricity should be include in the analysis including the tower, nacelle, rotor, foundation and transmission.

In eco aware wind turbine design, the materials are energy intensive with high embodies energy and carbon foot print, the material choice impacts the energy and CO2 for the manufacturing process, the material impacts the weight of the product and its thermal and electric characteristics and the energy it consumes during the use; and the material choice also impacts the potential for recycling or energy recovery at the end of life. The eco aware wind turbine design has two-part strategy: (1) Eco Audit: quick and approximate assessment of the distribution of energy demand and carbon emission over a product's life; and (2) material selection to minimize the energy and carbon over the full life, balancing the influence of the choice over each phase of the life (selection strategies and eco informed material selection).

The results of life cycle analysis of the 2.0 MW wind turbine show the problem with the energy consumed and carbon foot print was for the material phase. More energy and more emissions are produced during the primary material production of the wind turbine parts. The manufacturing process is the second dominant phase. The energy consumption and carbon foot print are negligible for the transportation and the use phases. The results also show clearly the benefits of recycling the wind turbine parts at the end of life. The life cycle analysis of the 2.0 MW wind turbine show that 54.8% of the total energy is recovered and a net reduction of C02 emissions by 55.4% is obtained by recycling the wind turbine materials at the end of life of the wind turbine.

#### **6. References**

Sustainable Development – 30 Energy, Engineering and Technologies – Manufacturing and Environment

Table 5. Construction Energy, Wind Turbine Energy Output and Energy Pay Back Time

end life of the turbine.

**5. Conclusions** 

material selection).

The turbine is rated at 2 MW but it produces this power only with the right wind conditions. In a best case scenario the turbine runs at an average capacity factor of 40% giving an annual energy output of 7.0 x 106 kWhr /year. The total energy generated by the turbine over a 25 year life is 175 x 106 kWhr (see Table 5). The total energy generated by the turbine over 25 year life time is about 32.32 times the energy required to build and service it (5.41 106 kWhr) if the turbine materials are sent to landfill at the end of life of the turbine. If the materials are recycled, the total energy generated by the turbine over 25 year life time is about 50.43 times the energy required to build and service it (3.47 106 kWhr). With a wind turbine capacity factor of 40 %, the energy payback time is about 9.27 months if the wind turbine materials are sent to landfill at the end life of the turbine and is only 5.94 months if the materials are recycled. The results show clearly the benefits of recycling parts of the wind turbine at the

The development of cleaner and efficient energy technologies and the use of new and renewable energy sources will play an important role in the sustainable development of a future energy strategy. Power generation from wind turbine is a renewable and sustainable energy but in a life cycle perspective wind turbines consumes energy resources and causes emissions during the production of raw materials, manufacturing process, transportation of small and large parts of the wind turbines, maintenance, and disposal of the parts at the end life of the turbines. To determine the impacts of power generation using wind turbine, all components needed for the production of electricity should be include in the analysis

In eco aware wind turbine design, the materials are energy intensive with high embodies energy and carbon foot print, the material choice impacts the energy and CO2 for the manufacturing process, the material impacts the weight of the product and its thermal and electric characteristics and the energy it consumes during the use; and the material choice also impacts the potential for recycling or energy recovery at the end of life. The eco aware wind turbine design has two-part strategy: (1) Eco Audit: quick and approximate assessment of the distribution of energy demand and carbon emission over a product's life; and (2) material selection to minimize the energy and carbon over the full life, balancing the influence of the choice over each phase of the life (selection strategies and eco informed

including the tower, nacelle, rotor, foundation and transmission.


**Sustainable Engineering and Technologies** 

Vestas (2005) "Life cycle assessment of offshore and onshore sited wind turbines" Vestas Wind Systems A/S, Alsvij 21, 8900 Randus, Denmark (www.vestas.com) **Part 2** 
