Download - LCA of a Small Wind Farm
UCD SCHOOL OF BIOSYSTEMS ENGINEERING
Life Cycle Assessment of a Small Wind Farm
BSEN 40440 – Life Cycle Applications
Luke Martin
5/26/2015
1
Contents Goal and Scope ....................................................................................................................................... 3
Goal ..................................................................................................................................................... 3
Renewable Energy System to be studied ............................................................................................ 4
Function of the system ....................................................................................................................... 4
Functional Unit .................................................................................................................................... 5
System Boundary ................................................................................................................................ 5
Allocation procedure .......................................................................................................................... 6
LCIA methodology and impacts .......................................................................................................... 6
Interpretation to be used.................................................................................................................... 6
Data Requirements ............................................................................................................................. 8
Assumptions ........................................................................................................................................ 9
Value Choices ...................................................................................................................................... 9
Limitations .......................................................................................................................................... 9
Data Quality Requirements ............................................................................................................... 10
Type of Critical Review ...................................................................................................................... 10
Type and format of the report .......................................................................................................... 11
Life Cycle Inventory ............................................................................................................................... 12
Data Collection .................................................................................................................................. 12
Data Calculation ................................................................................................................................ 14
Validation of data .............................................................................................................................. 16
Relating data to the function unit ..................................................................................................... 17
Refining the system boundary .......................................................................................................... 17
Allocation .......................................................................................................................................... 17
Life Cycle Impact Assessment ............................................................................................................... 18
General .............................................................................................................................................. 18
Selection of impact categories, category indicators and characterization models .......................... 18
Assignment of LCI results to selected impact categories ................................................................. 20
Calculation of category indicator results: ......................................................................................... 20
Resulting data after characterization: .............................................................................................. 21
Normalisation.................................................................................................................................... 22
Grouping ........................................................................................................................................... 22
Data Quality Analysis ........................................................................................................................ 22
Life Cycle Interpretation ....................................................................................................................... 24
2
Significant Issues ............................................................................................................................... 24
Evaluation ......................................................................................................................................... 28
Conclusions ....................................................................................................................................... 29
Limitations and Recommendations .................................................................................................. 29
Critical Review ....................................................................................................................................... 31
Appendices ............................................................................................................................................ 32
Appendix 1 - Raw material extraction and manufacturing ............................................................... 32
Appendix 2 – Turbine assembly and deconstruction ........................................................................ 34
Appendix 3 – Turbine maintenance and use phase .......................................................................... 35
Reference List ........................................................................................................................................ 36
3
Life Cycle Assessment of a Wind Turbine
Goal and Scope The wind energy sector is Ireland’s strongest growing renewable energy sector with 222
wind farms located on the island (IWEA, 2015). The popular adoption of this technology is
largely due to the pursuit of low-carbon intensive energy forms and to ease reliance on
fossil fuels (Martinez et al, 2008).
“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” (Ghenai, 2012). Based
on the premise of utilising the kinetic energy of the wind to generate a clean form of
electricity, wind power appears to be the ideal solution to this issue. However the
technology has recently come under scrutiny due to questions raised about wind power’s
relative sustainability when manufacture, transport and disposal processes are taken into
account (Tremeac & Meanier, 2009). Considering that these turbines are made from a
combination of metals, concrete and fibreglass, a considerable amount of energy derived
from fossil fuels is required during these stages of its lifecycle.
Life cycle analysis is a tool which can be utilized to determine the environmental impacts of
all of the stages of a renewable energy system life span and facilitates a more accurate
comparison of a RES with a conventional energy system. This study intends to apply this tool
to a wind turbine based on data sought from a wind farm in north county Dublin and assess
the emissions associated with its life cycle.
Goal
As stated in the introduction, a life cycle analysis is being carried out on a wind farm in Lusk
Co. Dublin. This site was chosen for the sake of simplicity; the farm consists of one Enercon
E-48 turbine and has a primary energy demand in the form of a food packaging plant.
This study aims to determine three things;
1. Are there any stages in particular within the turbine’s life cycle which has
considerable impacts on the environment?
2. How does a wind turbine’s associated environmental impacts compare to
conventional grid electricity use?
3. When all aspects of this wind turbine’s life cycle are quantified and converted into
the respective impact categories does it warrant the label of a “sustainable
technology”?
4
The results are intended for an audience who are adept in life cycle analysis and have a
good understanding of the wind energy industry. The results are not intended to be used for
comparative assertion given the author’s lack of experience in the area of LCA however, the
results derived from this study may be compared to those in the literature in order to assess
their accuracy.
Renewable Energy System to be studied
In order to assess the true sustainability of wind energy
a site in Lusk Co. Dublin was selected for this study for
two main reasons;
The wind farm consists of only one turbine,
making the gathering of activity data and the
scaling of the model easier for the inexperienced
LCA practitioner.
A certain degree of familiarity is associated
between the author and this site given that the
wind mill can be seen from his house.
This site is owned by a company called “Country Crest” a
commercial farming company which recently expanded
its business to include packaged and processed foods. The
electricity generated from the on-site turbine is
predominantly used to power these processes. When the wind is not blowing at sufficient
speeds, the factory is powered by the Irish grid.
By enlisting in the help of GaBi, it is expected that a cradle-to-grave analysis will be
successfully executed. This expectation is made because a considerable amount of time will
be saved by the use of this software seen as it does all the calculations for the user. Hence
the study considers all stages of development of an “Enercon E48” turbine. Figure.2 has
segregated the system into several phases including raw material extraction, truck and ship
transport, component manufacture, turbine assembly, use phase, maintenance phase,
decommissioning and final disposal of turbine parts. The only exception is the recycling
phase; the reason for this phase’s omission will be discussed in the “limitations” section.
Function of the system
The function of the system is to convert kinetic energy derived from wind into rotational
kinetic energy in a turbine and subsequently into usable electricity to power on-site
functions. This is depicted in the following equation albeit a simplified version:
𝑃𝑤 = 1
2∗ 𝑝𝐴𝑉³
Where Pw= Wind Power
Figure 1: Enercon E-48 turbine (Country Crest.ie, 2015)
5
p = Air Density A = Swept Area (m²) V = Wind Speed (m/s)
Obviously the wind does not blow at the same speed constantly and each turbine model has
a unique range rotor efficiencies at different wind speeds known as the power coefficient.
The model will include a number of scenarios which manipulate the inputs of this equation
along with the power coefficient, with data derived from a Weibull wind frequency
distribution specific to the site, in order to demonstrate the wind turbine’s effect on
emissions by offsetting the use of the Irish grid.
Functional Unit
The functional unit chosen for this study is the production of one MW of electricity. The
amount of goods packaged during the use phase has been manipulated to demand this
amount of power. All material quantities have been scaled to this unit.
System Boundary
Figure.2 depicts the system boundary in green. This study begins with raw material
extraction depicted as “metal” and “other material” extraction phases. This step can rely on
pre-existing processes in the GaBi database. The raw materials emerge from their respective
extraction phases as refined material ready to be manipulated into the desired parts. The
next step involves transporting these refined materials to either the turbine manufacturer in
Picardie, France or, in the case of concrete, directly to the assembly site in Dublin, Ireland.
Transported materials are processed into the respective turbine components via a number
of industrial processes such as casting, forging or stamping (Ghenai, 2012), summarised in
the “manufacturing phase”. Following this phase, the finished wind mill parts are exported
via truck and ship transport from Picardie to Dublin where the “assembly phase” takes place
involving a crane process, an excavator process and a bolting/drilling process to build the
wind mill.
Adjacent to this phase is the “use phase”, shaded in green in figure.2. In scenarios with
optimum wind conditions and frequencies (≈6-12 m/s) wind power can completely satisfy
the 1MW power demand however any scenario outside this range requires the use of the
Irish grid. The “Irish Grid” process is a pre-existing process within GaBi which is more than
acceptable to use in this project as outlined in the life cycle inventory.
The end-of-life phases are split into three phases in figure.3. The “decommissioning phase”
involve the dismantling and sorting of turbine components into the respective raw materials
of steel, iron, aluminium, copper, PVC and glass fibre. Following the methods of Tremeac &
Meanier (2009), concrete is assumed to be covered over in top soil and left in the ground
hence a landfill of concrete process should adequately represent the end-of-life activity of
this material.
6
While accurate activity data on the proportion of each of these materials going to landfill or
recovery was secured, there was an issue with how the model dealt with recycling (depicted
by broken green lines). This phase had to be omitted from the original system boundary due
to time constraints. This point is further elaborated on in the “limitations section”.
Allocation procedure
According to Martinez et al (2008), allocation is not a major issue in wind turbine LCA’s and
any possible impacts on final results are minimal; hence all processes within the system
boundary are assumed to have only one function to avoid this issue.
LCIA methodology and impacts
The first two objectives of this study; the sustainability of a wind turbine and how it
compares to the Irish grid will be assessed on their impacts towards global warming
potential (GWP), resource depletion and water use. The third objective which investigates
any processes with a particularly high impact to the environment may consider other
impacts such as acidification or eutrophication impacts.
CML 2001 was chosen as the characterisation method for this project based on the premise
that it uses midpoints over endpoints. Endpoint impact information is considered more
useful to policy-makers, especially those without a scientific background, as it expresses
impacts in a form that is easier understood. For example Eco-indicator 99 expresses the
impact of acidification processes as the amount of species extinct per m² per year.
According to Bare et al (2000), the majority of LCA experts believe that extending impact
categories as far as end point reduces the integrity of results because the availability of
reliable data remains too limited. Considering the target audience of this report are adept in
LCA and wind energy, it can be reasonably assumed that they have scientific backgrounds
hence mid-point indicators are used to express process emissions in this study.
While GaBi conveniently affords the user the opportunity of using multiple characterisation
methods the CML 2001 method is considered to be particularly reliable in its
characterisation methods especially with respect to European datasets.
Interpretation to be used
Following ISO14044:2006 standards; the interpretation will involve an analysis of the LCI
and LCIA results in order to identify the key contributors within the wind turbine’s life cycle
to the aforementioned impact categories. The interpretation will also assess the integrity of
the methods used to obtain these results and will consider the potential drawbacks with the
software, sampling errors and data quality.
7
Concrete Iron Copper
Steel Aluminium Concrete Glass Fibre
Nacelle Rotor Substructure
Inverter Cables
Wind Mill
Maintenance
Metal Extraction Phase Other Material Extraction Phase
Copper Iron PVC
Manufacturing Phase
Truck Transport
Assembly Phase
Site
Infrastructure
Truck and Ship Transport
Wind Energy
Irish Grid
Energy
Food Packaging
(1MW demand)
Tower
Use Phase
(Including
upstream
processes)
Decommissioning Phase
Steel Aluminium Glass Fibre
PVC
Truck Transport
Recycling Phase
Landfill Phase
Credit for
Plastic/Metal
Recovery
Plastic/Metal/
Concrete to Landfill
Waste Flow
Mass Flow
Emission Flow
Refined System Boundary
Power Flow
Figure 2: System boundary of the “Country Crest” wind farm, Lusk Co.Dublin. Original System Boundary
8
Data Requirements
For data relating to raw materials, electricity generation and waste processes, pre-existing
processes from the GaBi database are acceptable. Seeking specific data on these aspects of
the model are not likely to have a significant impact on the overall environmental emissions
of the system. For example the GaBi database contains cradle-to-gate processes for all
respective raw material extraction and refinement phases of the model. These pre-existing
processes rely on data gained from global averages. This is acceptable at this point in the
model as this phase is so far removed from the conversion technology itself.
In a similar vein, the use of pre-existing processes are generally favoured over user-created
ones for the majority of the manufacturing phase. There are a lot of emissions associated
with these processes and the pre-existing processes are likely to represent the process in
reality than a user created one, especially a user lacking experience in specific industry
techniques such as casting or forging. There are a few occasions when either a user-created
process or an edited existing process can be included in the model. Bolting and drilling for
example, are assumed to have emissions associated primarily with the electricity they use
hence this process will require little activity data, reducing the likelihood of error.
In some cases, pre-existing processes are present which are based on regional averages. The
French, German and Irish grids are all present in the GaBi database for example; and these
processes rely on grid mix data from November 2014. Given the up-to-date accuracy of
these electricity processes, the pre-existing “Irish Grid” process was selected to power site
process in the absence of ideal wind speed as shown in figure.2. This process will have a
significant impact on the results of the model.
High precision, site-specific data is required for the wind-mill’s size specifications as such
data will have a direct impact on the turbine’s ability to generate electricity. This data will be
sought from the Enercon website. In addition, wind speed data for the site must be of high
temporal and geographical accuracy as this parameter will also have a profound effect on
the model.
As outlined in assumptions, the most direct route is always chosen when compiling distance
data. This will be calculated using the distance function in google maps. Pre-existing GaBi
transport processes will used to represent material and goods transport while exact
distances will be inserted into the model using parameters within these processes.
Finally, specific data will be utilised within the end-of-life stages of the model to determine
the proportions of material going to landfill or recycling. Pre-existing landfill and recycling
processes will be applied when possible. In the event when a material-specific landfill
process is not available, an existing landfill/recycling process will be manipulated to accept
the material in question.
9
Assumptions
The largest assumption made in this model is that all power generated from wind is utilized
by on-site processes. In reality, the turbine provides power for approximately 150 local
households during optimum wind conditions. Since the main objectives of the study are
focused on the renewable energy system itself, this assumption is acceptable as these
households are well and truly outside the system boundary.
For raw material and component transport, it is assumed that the most direct route
suggested by Google maps is taken. In addition it is assumed the port nearest the terrestrial
site (Dublin) is used for component import.
Waste generated in the form of scrap during the “manufacturing phase” is assumed to be
100% recycled as the waste is generated on site and could theoretically be used in
subsequent component manufacture. (e.g. the “steel bending and stamping” process has a
5% scrap parameter attached to it)
Value Choices
This study is concerned primarily with GHG emissions, water usage and energy usage. In the
event that a process is identified with a formidable effect on another impact category such
as acidification potential, that impact category will also be discussed in the interpretation
phase. However upon making suggestions on how a process could minimize the turbine’s
overall environmental impact, the first three impact categories will override the latter.
Limitations
Design and development of the wind turbine will be omitted from the study due the fact
that this process itself does not make a significant physical contribution to emissions of this
now mass produced technology in comparison to the other phases in the life cycle (Rebitzer
et al, 2004).
Specific data for the quantity of materials used in an Enercon E-48 turbine could not be
located. The material quantities per MW of a wind turbine with a steel tower were taken
from Wilburn (2011) to overcome this limitation. The main drawback with this substitution
is that this data is based on American turbines however it offered the most precise data on
the quantities of materials scaled to 1 MW hence was ideal for this study.
Picking up on the omission of the recycling phase from the system boundary; the user did
not anticipate how GaBi dealt with the recycling of materials. The omission of this process is
not ideal as it does not come under the cut-off criteria of the model. A considerable amount
of material was recyclable hence the recycling phase was likely to reduce the overall
emissions associated with the wind turbine manufacture stage significantly. The pre-existing
“credit for recycling” processes within the database only function when linked to the
manufacturing phase earlier on in the model. This model used a hierarchical structure to
10
encapsulate the renewable energy system which did not allow the recycling processes,
located in the disposal phase, to link up with the manufacturing phase upstream.
In order to overcome this issue, the entire model would have to have been redesigned. This
was not possible due to time constraints, with the model deadline fast approaching. As a
slight consolation, the recyclable portion of the waste was successfully diverted from landfill
within the model. As a result, the contribution of the disposal phase to life cycle emissions
has been muted slightly hence the results are still considered somewhat robust and should
allow for the objectives of this project to be achieved albeit with higher uncertainty.
Finally, the model is being created on an educational version of GaBi. This version has a
limited number of unit and system processes available to the user. This will require the
input of data gathered from industry and the literature. This information can be difficult to
locate hence there are likely to be gaps in the model due to this.
Data Quality Requirements
Close to the energy conversion source, data is expected to be up-to-date, geographically
relevant, technologically precise and relatively complete. Ideally manufacturer specific date
will be required in and around the use phase.
Background processes need not be as site specific. There are hundreds of LCA studies on
wind turbines hence any datasets obtained from the respective LCA databases can be
considered relatively robust. Hence In the event where data for a specific unit process or
raw material cannot be obtained, LCA data for a similar process or material will suffice as
opposed to omitting the parameter altogether. For example, for disposal and raw material
phases it is acceptable to use non-specific data from a similar study as the results are
unlikely to deviate significantly from results derived from site specific data.
Failing to find a suitable substitute process (i.e. in the case of recycling), the system
boundary will be altered to avoid the process’s inclusion. While the specific data in this
circumstance is available, it is difficult to determine a way to incorporate it into the model
hence a zero value is technically assigned. As highlighted in the limitations section, this zero
value is significant in the sense that it contributes to the muting of landfill values. It is clear
that if recycling had of been successfully included in the model, emissions from
manufacturing should also have been muted slightly.
Type of Critical Review
The critical review will assess whether the results and interpretation of the LCA satisfied the
goal and scope outlined by the author, whether there are any discrepancies or omissions in
the data or whether the author gave a well-rounded view of the subject. Ideally the project
should be reviewed by another LCA practitioner to ensure the absence of bias and personal
errors one might not be aware of.
11
Type and format of the report
The format of the report will strictly adhere to ISO 14040 standards including a goal and
scope; inventory analysis, impact assessment and interpretation and will be written to cater
for an audience with a solid grounding in LCA and wind energy.
12
Life Cycle Inventory
Data Collection
Raw Material Inputs Quantities of raw materials required per MW of electricity are acquired from Wilburn
(2011). Table.1 shows the exact quantities of steel, concrete, iron, fibreglass, copper and
plastic.
Table 1: Raw Material Quantities (Wilburn, 2011)
Material Proportion of turbine Mass per FU (kg/MW)
Stainless Steel 20% 116,800
Concrete 71% 402,000
Cast Iron 4.4% 24,925
Fibreglass 1.9% 10,780
Aluminium 1.4% 8,100
Copper 0.5% 2,800
PVC 0.08% 500
Transport Table.2 shows the distances the various parts required for turbine assembly need to travel
from the respective material merchants to the Enercon manufacturing facility in Picardie.
The parts are assumed to be sourced from the merchant closest to the Enercon facility
according to google maps. Within the model, these parts are represented by system
processes hence all upstream transport emissions from extraction source to processing
facility have been estimated and are included within the dataset. Parameter explorer will be
utilized to investigate the significance of increasing these transport distances.
Table 2: Refined material transport (google maps, 2015)
Material Truck Transport per FU (km)
Stainless Steel 184
Concrete 65
Cast Iron 184
Fibreglass 71
Aluminium 81
Copper 77
PVC 100
Table.3 displays the distances the turbine components are required to travel from Picardie
to the assembly site in Lusk, Co. Dublin. Again, google maps are used to estimate distances
and it is assumed that the most direct route was taken.
13
Table 3: Distances of component transport from manufacturing plant to assembly site
Turbine Component Truck [France and Ireland] (km)
Ship (km)
Tower 442 880
Nacelle 442 880
Rotor 442 880
Inverter 442 880
Cable 442 880
Concrete 100 0
End-of-life transport is summarised in table.4. Material for landfill is assumed to be
exported to the nearby landfill at Balleally, Lusk while recyclable material is assumed to go
to a sorting centre in Malahide, Co. Dublin.
Table 4: End-of-life transport
Waste Treatment Method Distance (km)
Landfill 3
Recycling 15
Energy Inputs Industry averages derived from the GaBi database or from online sources are sufficient for
the use of electrical and thermal energy in processes such as welding, casting and forging
are utilised in this LCA. Table 5 shows the total energy required for each manufacturing
stage along with the conversion process used in real life and the process used to mimic this
in GaBi.
Table 5: Energy use by model processes
Component Manufacturing Process
GaBi Process Energy required (MJ)
Tower Forging, Rolling Steel Bending 13703 Electrical Nacelle Forging, Rolling Steel Bending, Cast
Iron System Process 54342 Electrical
Rotor Composite Forming Welding, Cast Iron System Process
17600 Electrical
Inverter Forging, Rolling Copper bending, Aluminium die cast
28285 Electrical 15390 Thermal
Cable Polymer extrusion Rod formation/ Assembly (us-o)
1440 Electrical 1264 Thermal
Concrete Construction System Process (Diesel; Covered in Transport)
14
Emissions to air, water, soil GaBi is highly depended on for this aspect of the model. The pre-existing system and unit
processes within the database have associated emissions embodied within them. When a
user-process is created the associated emissions have to be input individually into the
process. While every effort was taken to ensure the accurate location and input of these
emissions, this inevitably leads to uncertainty due to the scant availability of such data on
the internet. Whenever possible, the practice of copying and editing an existing unit process
within GaBi is preferred to creating a new one provided it is at least similar in some way to
the process in real life.
Waste Table.6 shows the proportion of each material which is available for recovery or destined for
landfill. These proportions are taken from Martinez et al (2008) as precise activity data for
this particular site was not readily available.
Table 6: Proportion of materials for waste or recovery
Material Recycling (%) Landfill (%)
Stainless Steel 97 3 Concrete 0 100 Cast Iron 95 5 Fibreglass 48 52 Aluminium 35 65 Copper 28 72 PVC 72 28
Data Calculation
The main data calculations associated with this model are related to the “use phase”. The
function of this phase is to demonstrate the environmental effect of displacing fossil fuel
electricity generation with wind energy. In this model, a pre-existing system process of the
Irish grid mix is selected as the alternative power source to wind at this site. This process
consists of electricity generation from a combination of natural gas, peat, coal and a small
proportion of wind. When the wind is blowing at a velocity of 9 or 10 m/s, the turbine
operates at its highest efficiency and can completely satisfy the on-site energy demands.
The wind however, is a highly variable resource and does not blow consistently at these
optimum speeds. Table.7 shows the three main variables which determine the power
output of a wind turbine; wind speed, power coefficient and wind hours. The power
coefficient data, unique to this E-48 turbine and was acquired from Enercon (2012).
15
Table 7: Weibull Wind Speed Distribution
Wind Speed Power Coefficient Weibull Wind Hours
m/s Cp hr
0 0 0 0
1 0 0.039992 350.32992
2 0 0.075234 659.04984
3 0.17 0.101903 892.67028
4 0.35 0.117783 1031.77908
5 0.43 0.122525 1073.319
6 0.46 0.117466 1029.00216
7 0.47 0.105108 920.74608
8 0.48 0.088447 774.79572
9 0.5 0.070333 616.11708
10 0.5 0.05303 464.5428
11 0.45 0.038 332.88
12 0.39 0.025925 227.103
13 0.32 0.016862 147.71112
14 0.27 0.010466 91.68216
15 0.22 0.006205 54.3558
16 0.18 0.003515 30.7914
17 0.15 0.001905 16.6878
18 0.13 0.000987 8.64612
19 0.11 0.00049 4.2924
20 0.09 0.000233 2.04108
21 0.08 0.000106 0.92856
22 0.07 4.16E-05 0.364416
23 0.06 1.92E-05 0.168192
24 0.05 7.96E-06 0.0697296
25 0.05 2.95E-06 0.025842
The wind-hours data was calculated using hourly wind frequency data from the Dublin
Airport weather station provided by Met Eireann (2015). The key to achieving the second
objective of this project is to incorporate this data into the model. This was facilitated with
the use of parameter explorer in which a number of wind speed scenarios were created to
include each of the rows in table.6. Figure.7 illustrates an “electricity chooser” process
which switches grid supply on and off pending on wind conditions. The current wind
scenario in this figure is set to 10 m/s; hence the grid is making no contribution to the 3.6
MJ (1MW) of power demanded by the “site processes”.
16
Figure 3: Wind energy vs grid energy to satisfy energy demand
Validation of data
Table.8 shows a compilation of consistency checks carried out within each plan in the
model. There is one major outlier which will be discussed in the interpretation.
Table 8: Mass Balance Consistency Check
Process Mass In (kg) Mass Out (kg) Difference (%)
Tower Manufacture 74800 74700 -0.13368984
Nacelle Manufacture 35000 35000 0
Rotor Manufacture 27700 27700 0
Inverter Manufacture 9600 9600 0
Cable Manufacture 3250 3250 0
Site Infrastructure 402000 452000 12.43781095
Site Maintenance 13650 13650 0
Electricity Generation 566000 566000 0
Turbine Decommission 566000 566000 0
17
Relating data to the function unit
All material quantities and by extension all energy inputs have been scaled to the functional
unit of one MW of electricity produced by the tactical collection of activity data as outlined
in table.6. The entire model is scaled to the “site processes” unit process in the use phase
which creates a demand for 1 MW of electricity. Obviously the wind turbine only generates
electricity when the wind is blowing at sufficient speeds so this factor is covered by
inputting the Weibull distribution specific to this site (Table.7) as a parameter in the model.
When the wind is not blowing at sufficient speed to satisfy the demand, power from the grid
makes up the difference as shown in appendix.3. The emissions associated with the Irish
grid have been modelled in order to demonstrate how these emissions are offset by wind
energy at this site.
Refining the system boundary
As stated in the “limitations” section it was necessary to refine the system boundary to
exclude the recycling phase of the model as outlined in figure.2. This was not down to a lack
of available activity data, as is usually the case when refining a system boundary but down
to an oversight made by the inexperienced user when designing the model. Due to time
constraints it was not possible to rectify the model to include recycling. As previously stated,
this will have a significant impact on the results however it does not render them useless.
Allocation
Allocation was avoided in two circumstances within the model by using two separate
techniques.
1. Waste flows associated with scrap of various metals during the “manufacturing
phase” were assumed to be 100% recycled. Despite this being an incorrect
assumption to make, the effect that this assumption will have on the model is well
below the cut-off criteria of the model; hence it will not have a significant effect on
the overall results.
2. During the “disposal phase” allocation was avoided by system expansion. Here a
“sorting” process was created which assigned exact proportions of waste materials
to their respective end-of-life process based on activity data gained from Martinez et
al (2008).
18
Life Cycle Impact Assessment
General
This phase of the LCA, which assigns characterisation factors to the data compiled during
the inventory phase, will be carried out by GaBi. While the program offers a variety of
options to the user for completing this step it is necessary to select an appropriate
characterisation method, taking the scope of the project into account.
Selection of impact categories, category indicators and characterization
models
According to ISO standards, it is acceptable to select a category indicator anywhere along an
environmental chain between intervention and endpoint (Guinee et al. 2002). Hence the
aims set out in goal and scope play a large part in choosing the appropriate method. On the
basis that the intended audience of this study are assumed to be scientifically proficient, a
mid-point approach to characterisation of LCI emissions data is selected for the life cycle
impact assessment. The use of mid-point indicators over end-points is considered to be
more accurate as they are closer in the cause-and-effect chain to the source of emissions.
Many LCA practitioners are of the opinion that the availability of data is too limited to
extend an impact as far as an end-point such as the “amount of species killed per unit area
per year” (Bare et al, 2000).
Fundamentally, what the various impact assessment methods do is multiply the inventory
results by the appropriate characterisation factors yielding the “environmental profile”
which is then normalised (Guinee et al, 2002). The scope of this project only requires focus
on global warming potential, resource depletion and water usage however acidification will
also be included. Although a midpoint impact method is being deployed to characterise LCI
data, ISO 14044 standards require that the potential endpoint impacts must be explicitly
stated in the report. The endpoints associated with global warming potential are polar ice-
cap melting, sea-level rise and alteration prevailing weather patterns. Resource depletion
exhibits endpoints related to unsustainability with a decrease of these resources available to
future generations. An endpoint in this category might look like “amount of persons per
square metre unable to meet electricity requirements”. With an endpoint as speculative as
this it is easy to see why LCA practitioners believe that the current records are not robust
enough to extend an impact as far as endpoints (Bare et al, 2000). Water usage can result in
endpoints associated with drought, crop failure and species extinction for example “species
depleted per square meter per unit time” as the “EcoIndicator 99” characterisation method
in GaBi illustrates.
Table.9 details the key contributors within the life cycle of a wind turbine to each of these
respective impact categories.
19
Table 9: Sources of significant environmental impact within the wind turbine's life cycle
Unit Process Global Warming Resource Depletion Acidification Water Usage
Tower Manufacture Steel rolling/forging, material transport, electricity use
Steel extraction, diesel/oil use during transport.
Release of acidic gases during production/ combustion
Cooling during industrial processes, emissions to water.
Rotor Manufacture Cast iron/fibreglass processing, material transport, electricity use
Iron/Ferro-metals extraction, diesel/oil use during transport.
“ “ “ “
Nacelle Manufacture
Steel/Cast iron casting, material transport, electricity use
Steel/Iron extraction, diesel/oil use during transport
“ “ “ “
Inverter Manufacture
Copper/Aluminium processing, material transport, electricity use
Copper/Aluminium extraction, diesel/oil use during transport
“ “ “ “
Cable Manufacture PVC/Copper/Steel processing/casting, material transport, electricity use
Plastic derivative/Copper/Steel extraction, diesel/oil use during transport
“ “ “ “
Site Infrastructure Cement mixing/concrete casting, material transport, electricity use
Sand/Lime/Rock extraction, diesel/oil use during transport and earth works
“ “ Water used in concrete mix, emissions to water
Turbine Assembly Bolting/drilling/welding parts together.
Crane and JCB use of diesel
“ “ Emissions to water
Turbine Maintenance
Involves a combination of all the aforementioned manufacturing processes in scaled down form
Lubricating oil, diesel oil use during transport and site maintenance visits
“ “ Involves a combination of all the aforementioned manufacturing processes in scaled down form
Turbine Deconstruction
Electricity/diesel use in deconstruction, emissions from landfill
Diesel use in transport and crane/JCB processes
Release of acidic emissions during decomposition/ combustion
Emissions from landfill
20
Assignment of LCI results to selected impact categories
Table.9 shows that each of the unit processes contributes in some way to each of the four
impact categories chosen for this study. Characterisation factors will be assigned to each of
the emissions associated with these processes to express results as an environmental
impact quantity. This will be carried out using CML-2001.
Calculation of category indicator results:
Based on the fact that midpoint indicators are to be utilised to characterise GWP, resource
depletion and water usage in this model, the CML-2001 characterisation method was
deemed most appropriate for this study. This method created by scientists from Leiden
University in The Netherlands, is the most up-to-date method available in the educational
version of GaBi and was selected on the basis of its high ranking on Hauschild et al’s (2013)
assessment of the most reliable midpoint impact characterisation methods.
This model expresses GWP (100 year time horizon) in as a midpoint in terms kg of CO₂
equivalent. The CML characterisation factor is based on data from the Intergovernmental
Panel on Climate Change (BRE, 2005).
Resource depletion is related to the extraction of scarce minerals and fossil fuels and is
expressed as “abiotic resource depletion” in units of kg Sb equivalent. This unit takes into
account calculations of remaining reserves and the rate of extraction (BRE, 2005).
Acidification potential is expressed as kg SO₂-eq. Endpoints of this category are attributed to
acid rain and ecosystem impairment. Acidic gases such as NOx and SOx, released during the
various life cycle stages can react with moisture in the atmosphere, resulting in acid rain.
CML’s midpoint of “freshwater aquatic eco-toxicity”, measured in kg of dichlorobenzene
equivalent (kg of DCB-eq) to indicate how toxic releases from the life cycle of the wind
turbine can affect freshwater environments.
21
Resulting data after characterization:
Table.10 shows the values given by the CML-2001 characterisation method while figure.4
expresses these values as relative contributions.
Table 10: Life cycle impact assessment values
Global Warming (GWP100)
Abiotic Resource Depletion
Acidification Potential
Freshwater Aquatic Eco-Toxicity
Units kgCO₂-eq Kg Sb-eq Kg SO₂-eq kgDBC-eq
Tower Manufacture
63,600 3.03 298 1080
Rotor Manufacture 36,900 0.9 130 189
Nacelle Manufacture
30,000 1.22 126 479
Inverter Manufacture
75,300 12.8 322 707
Cable Manufacture 6,750 8.36 29.9 189
Site Infrastructure 59,100 0.0611 137 94.5
Turbine Maintenance
14,300 2.99 67 220
Turbine Deconstruction
1800 0.000182 6.7 9.18
Other 49350 0.0289 77.1 41.5
Total 337,000 29.4 1190 3010
Figure 4: Relative contribution of major turbine components per impact category
0% 20% 40% 60% 80% 100%
Global Warming(GWP100)
Abiotic ResourceDepletion
Acidification Potential
Freshwater Aquatic Eco-Toxicity
18.9
10.3
25.0
35.9
10.9
0.2
10.9
6.3
8.9
4.1
10.6
15.9
22.3
43.5
27.1
23.5
2.0
28.4
2.5
6.3
17.5
0.2
11.5
3.1
4.2
10.2
5.6
7.3
0.5
0.0
0.6
0.3
14.6
3.0
6.5
1.4 Tower
Rotor
Nacelle
Inverter
Cable
Site
Maintenance
End of life
Other
22
Normalisation
Normalisation is the expression of this profile relative to a given geographical region. In this
project it is acceptable to use a region as broad as Europe or even the world for this
purpose. This facilitates a clearer understanding of the magnitude of LCI results as they are
related to a specific population and time frame. CML-2001 carries this out automatically
hence all results are already normalised according to global (GWP) and European (Resource
depletion, acidification and water pollution) standards.
Grouping
Figure.4 has an “other” category highlighted in a green colour. This consists of an aggregate
of all electricity, thermal energy and transport processes utilised throughout the model.
Following a gravity/pareto analysis it was observed that these processes contributed a
negligible amount of emissions individually however when grouped together their impact
could be significant especially in terms of GWP (fig.4).
Data Quality Analysis
Gravity Analysis Figure.5 shows a pareto analysis of the wind turbine life cycle ranking the cumulatively
highest contributors to the left of the graph and the lowest contributors to the right.
Superimposed on top of this graph are the relative material quantities for each component
(orange line).
0
5
10
15
20
25
30
35
40
45
50
Pe
rce
nta
ge C
on
trib
uti
on
to
em
issi
on
s (%
)
Global Warming(GWP100)
Abiotic ResourceDepletion
AcidificationPotential
Freshwater AquaticEco-Toxicity
Figure 5: Pareto Analysis of the major turbine components
23
Despite having the highest amount of material input (71.1%), the “site” infrastructure ranks
only third on the list with a GWP contribution of 17.5%. The “tower” component ranks only
second in all categories except for “freshwater eco-toxicity” despite having a 13.3% share of
material inputs. The “inverter” production process ranks highest on the list despite having
only a 1.7% share of material inputs. This process along with the “cable” manufacturing
process ranks particularly highly in the abiotic resource depletion category.
Uncertainty Analysis Taking GWP as an example, Table.9 compares the emissions calculated from this study to
those in the literature. After a brief analysis it becomes evident that the overall emissions
have been grossly underestimated in this study.
Table 10: Comparative analysis with other wind turbine studies
This Study (2015)
Tremeac & Meunier (2009)
Ghennai (2012)
Crawford (2009)
Abeliotis et al (2014)
Unit kg CO₂-eq kg CO₂-eq kg CO₂-eq kg CO₂-eq kgCO₂-eq
Total emissions 337,000 820,467 1,400,000 1,844,000 872,000
Turbine Assembly 311,000 705,111 1,200,000 N/A 928,300
Turbine Maintenance
13400 N/A N/A N/A 405
Turbine Deconstruction
1710 -48.88888889 13095 N/A -70,200
Functional Unit 1 MW 1 MW 1MW 1MW 1MW
24
Life Cycle Interpretation
Significant Issues
Reiterating the goal of this project, the primary objective was to identify and analyse any
aspects of the wind turbine’s life cycle which have a considerable impact on the
environment. In order to address this, the analysis will follow the structure of the gravity
analysis carried out in the LCIA.
Secondly, the project set out to determine the benefits of offsetting grid use; and ultimately
intends to conclude whether the construction of a wind turbine is a worthwhile investment
in terms of saving on emissions. This will be explained using a scenario analysis outlining the
gradual increase in emissions as the Irish grid supplements the energy demand.
Inverter (and cable) manufacture: Aluminium and copper The gravity analysis carried out in figure.5 revealed that despite a minuscule share (1.7%) of
the overall amount of input materials, the production of the inverter component of the
turbine proved to be the costliest aspect of the life cycle in terms of emissions. At first
glance this outlier appeared to be the result of experimental error however another study
also noted that copper usage is particularly detrimental in terms of emissions. Figure.6
hones in further on the inverter process to reveal that a “copper from electrolysis” process
and an “Aluminium ingot” process are responsible for the poor environmental performance
of this component.
Figure 6: Relative contribution to emission for Inverter manufacture
Aluminium is responsible for the majority of acidification and GWP emissions. Despite being
the third most common element on Earth (hence its low contribution to resource
depletion), the extraction process for aluminium is extremely energy intensive
0
20
40
60
80
100
120
Acidification Abiotic resourcedepletion
GWP Freshwater eco-toxicity
Pe
rce
nta
ge C
on
trib
uti
on
of
em
issi
on
s (%
)
DE: Copper mix(99,999% fromelectrolysis) PE
EU-27:Aluminiumingot mix PE
25
(Environmental Literacy Council, 2015). According to the Environmental Literacy Council
(2015) copper is also extremely rare in its pure form (hence its high contribution to resource
depletion) and the electrolysis process used to purify is extremely energy intensive. This
observation can be reiterated by looking at the “cable” process in figure.5, which also has a
resource depletion outlier attributable to copper use. Wilburn (2011) notes the importance
of reducing the amount of copper in future wind turbines to improve their environmental
appeal. Despite this Wilburn did not report as large an anomaly as noted in this study.
Steel vs concrete This is where the experimental error comes in, the copper and aluminium processes used in
Gabi (appendix.1_inverter manufacture) are cradle-to-gate processes involving purification
of the two elements from electrolysis. Furthermore aluminium extraction requires large
amounts of strip mining and heavy industrial processes to separate it from the mineral
bauxite. The copper and aluminium used in industry is generally sourced from recycled scrap
to eliminate these costly processes from the supply chain (Environmental Literacy Council,
2015), something this model failed to do. With a pound-for-pound environmental
performance this low, it might go some way to explaining why some of the studies used to
compare against (Tremeac & Meunier,2009, Abeliotis et al, 2014), omitted the modelling of
the inverter component altogether. Green-washing?
Moving on to the next largest emitter, the “tower” process, accounting for only 13.3% of the
total amount of material yields the highest contribution overall to freshwater eco-toxicity.
This process also contributes higher in all impact categories over “site infrastructure” which
accounts for 71.1% of the total material inputs. Figure.7 identifies pre-cast concrete as the
main component of site infrastructure while steel is the predominant component of the
tower manufacture. Clearly steel has a more significant impact to the environment due to a
complex production process along with the use of rarer earth materials however it
maintains a much lower pound-for-pound environmental burden than aluminium or copper.
Figure 7: Concrete vs Steel emissions contribution
0
5
10
15
20
25
30
35
40
45
GWP Acidification ResourceDepletion
Freshwater Eco-toxicity
Re
lati
ve C
on
tib
uti
on
to
em
issi
on
s (%
)
EU-27: Pre-cast concretePE
DE: Steelbillet (100Cr6)PE
26
Expected trend and Nacelle anomaly For the most part the remaining processes in the life cycle appear to yield straight-forward
results. Figure.5 illustrates that low emissions coincide with low material inputs. The
processes such as turbine maintenance, nacelle and rotor manufacturing have relatively less
intensive production processes also, keeping emission low. End-of-life is not shown in this
figure as the associated emissions were below the cut-off point in this instance. There is a
slight blip in the maintenance stage which is also attributable to copper and aluminium
replacement parts.
The only anomaly worth investigating further is the nacelle’s relatively high contribution to
freshwater eco-toxicity. Steel appears to be the main culprit according to figure.8 which
seems to follow the trend set by this material in figure.7.
Figure 8: Nacelle Freshwater contribution
Wind energy compared to grid use Up until this point, there has been little mention of emissions associated with the Irish grid.
This is due to the default scenario of the turbine operating at optimum conditions hence
there was no input from the Irish grid. Besides saving money and increasing energy security
the main reason for an Irish enterprise to invest in a wind turbine is to reduce their
environmental impact during the generation of electricity. In order to provide an answer to
this question figure.9 shows a comparison between wind and grid energy emissions.
Flow s
Diagram:Nacelle_Manufacture - Inputs/Outputs
DE
: S
teel b
illet (1
00C
r6)
PE
DE
: C
ast iron p
art
(auto
motiv
e)
PE
<p-a
gg>
FR
: E
lectr
icity
grid m
ix (
pro
ductio
n m
ix)
CM
L2001 -
Apr.
2013, F
reshw
ate
r A
quatic
Ecoto
xic
ity P
ot. (
FA
ET
P in
f.)
[kg D
CB
-Equiv
.]
450
400
350
300
250
200
150
100
50
0
27
These graphs change according to wind speed, rotor efficiency and wind-hours for each
respective scenario. The data for each scenario is available in table.7. Figure.9 displays a
slight reduction in emissions as wind speed increases from 3-6 m/s representing less of a
reliance on the grid. From 6-13 m/s the turbine is operating at optimum conditions and
100% of the energy demand is being supplied by wind power. The emissions associated with
these speeds are the total emissions from the turbine life cycle. At 14-m/s onwards, the
rotor efficiency reduces and the wind frequency lowers meaning the grid kicks in to
0
100
200
300
400
500
600
700
3m/s
4m/s
5m/s
6m/s
7m/s
8m/s
9m/s
10m/s
11m/s
12ms
13m/s
14m/s
15m/s
16m/s
Re
lati
ve c
on
trib
uti
on
to
em
ssio
ns
(%)
Wind Speed scenario
GWP
Acidification
Freshwater Eco-toxicity
Resource Depletion
0
2000
4000
6000
8000
10000
12000
14000
16000
14 m/s 15 m/s 16 m/s 17 m/s 18 m/s 19 m/s 20 m/s 21 m/s
Re
lati
ve c
on
trib
uti
on
to
em
issi
on
s (%
)
Wind Speed Scenario
GWP
Acidification
FreshwaterEco-Toxicity
Resourcedepletion
Figure 9: Wind speed scenarios impact on emissions
28
supplement energy demand. In each scenario thereafter, acidification, resource depletion
and GWP emissions increase dramatically shooting up to between 10,000 and 14,000%.
Figure.10 shows absolute values for the influence of wind speed on the four impact
categories. At 13 m/s all emissions are purely from wind energy but from 15 m/s onwards,
the emission values increase over 1000 times to that of wind energy.
Table 11: Influence Irish grid has on emissions.
Units 13 m/s 15 m/s 17 m/s 19 m/s 21 m/s 23 m/s
GWP kg CO2-Equiv.
337296.6 1002049 3517279 13973946 65032255 359535158.8
Acidification pot.
kg SO2-Equiv.
1192.054 3125.94 10443.2 40863.55 189401.5 1046164.071
Freshwater Eco-Tox
kg DCB-Equiv.
3007.201 3358.496 4687.695 10213.63 37195.92 192829.0055
Resource Depletion
kg Sb-eq 2957556 11119319 42001060 1.7E+08 7.97E+08 4413153312
Evaluation
The results show favourable emissions data for the wind energy industry however there is a
major issue with the results of this study which must be taken into account before
conclusions can be made.
I. Completeness As noted in table.10, this study has grossly underestimated life cycle emissions for a wind
turbine and a functional unit 1MW of electricity. The results from this study are between 3-8
times lower than those calculated by recent studies on wind turbines using GWP as a
reference.
This error is most likely due to the over-simplification of the model. The nacelle for example
consists of 1000 different parts in real life. This study attempts to quantify these parts by
categorising them into their core material. This leads to the omission of a vast amount of
processes, which adds to the overall emissions. In addition, the use of stamping and bending
processes in replacement of forging and casting processes probably underestimates
emissions also.
Another inconsistency associated with this model is the improper modelling of recycling.
Had the recycling phase been executed properly, the emissions for the likes of copper and
aluminium would have been lowered significantly improving the integrity of the model.
Referring back to table.10 once more, some of the studies have minus figures for end-of-life
phase which represents credit for recycling.
29
II. Sensitivity The sensitivity analysis used to demonstrate the impact of grid emissions proves that the model responds as it is supposed to with respect to changes in its parameters. Wind speed, rotor efficiency and wind hours all alter according to the site specific Weibull distribution outlined in table.7. Figure.9 and table.10 demonstrate how the emissions steadily rise as the three parameters used in the sensitivity analysis alter.
III. Consistency Every effort was taken to ensure spatially and temporally accurate data was utilised
whenever possible. Many of the pre-existing processes in GaBi allow the user to select
geographically relevant processes. The Irish and French grid mixes for example are derived
from data as recent as November 2014. Some of the production processes however were
from the NREL database and hence were based on American data.
With regards to impact categories, the CML-2001 method should have accurately
normalised data to the relevant spatial standard for each impact category.
Conclusions
Despite a significant degree of experimental error, hotspots could be identified in
the wind turbine’s life cycle. Aluminium and copper proved to be among the most
notorious material for emissions in GWP, resource depletion, water eco-toxicity and
acidification due to their energy-intensive extraction processes and electrolysis
processes used for purification.
Steel was the second highest emitter and this was more proportionate to the
amount of this material required.
According to these results wind energy can definitely be considered a green
technology when the entire life-cycle is taken into account.
This observation is marred by the fact that the model grossly underestimated overall
emissions.
Substituting the overall GWP emissions from this study with those from Crawford
(2009), the Irish grid yields emissions 195 times greater than total emissions from
wind energy. Based on these figures, wind energy unequivocally deserves the title of
a “green technology”.
Limitations and Recommendations
The key limitation with this study is that the model is not of a sufficient resolution to
represent the life cycle of a wind turbine accurately. A key recommendation is that more
accurate activity data be sought for the wind farm in Lusk Co. Dublin as well as on industry
data on the wind turbine process itself.
Secondly the layout of the model in GaBi requires a rethink in order to incorporate recycling
phases appropriately.
30
A second or third sensitivity analysis should have been carried out to analyse other portions
of the model however due to a modelling over-sight this proved too difficult to perform. The
oversight consisted of leaving transport and recycling processes out of the naming hierarchy
applied to manufacturing phases. This meant that when a sensitivity analysis was attempted
the respective transport processes were indecipherable meaning it was impossible to know
which leg of the transport was being edited. To rectify this would have meant to go back
and redevelop the model/ There was insufficient to perform this hence only one sensitivity
analysis will suffice.
31
Critical Review The purpose of this study was to apply the LCA technique to a wind turbine in Co. Dublin to
determine whether wind energy is worthy of its title of a “green technology”. The aims were
to highlight any significant processes in the life cycle with considerable environmental
effects as well as demonstrating the amount of fossil fuel emissions offset by this
technology. The project initially set out to cover all process cradle-to-grave however due to
a modelling error, the system boundary had to be refined to exclude the recycling phase.
This omission along with the rationale behind it was illustrated very clearly and explicitly.
The system diagram makes good use of colour to illustrate clearly the various unit processes
and how they link up.
The life cycle inventory phase seems to be executed reasonably well with an abundance of
tables outlining the inputs to the model. The activity is predominantly derived from
secondary sources from industry analyses. All sources are clearly referenced.
The model itself appears to be the biggest issue with the project, the user had difficulty
executing the end-of-life phase hence credit for recycling cannot be included in the model.
In addition, the model is too simplified hence not all emissions are accounted for. These
errors are clearly documented.
The LCIA phase adequately described the endpoint categories and stated which midpoints
were to be used in the project. The CML-2001 characterisation method was selected on
recommendation from a journal article. Results were compiled neatly on an innovative
graph which clearly shows material inputs against impact categories.
The interpretation highlighted aluminium and copper as the key impacts to the turbine life
cycle. Some of these anomalous figures were attributed to modelling error however some
studies in the literature back this observation up to suggest these material have a relatively
large environmental impact. These sources were reference appropriately.
Despite an abundance of experimental errors, the study can confidently conclude wind
energy is a green technology; with emissions approximately 195 times lower than the Irish
grid mix. Hence the objectives of the study were accomplished.
Appropriate recommendations for improvements were made and screenshots of the model
were included in the appendices, adding to the transparency of the project, leaving it open
to a more honest interpretation.
32
Appendices
Appendix 1 - Raw material extraction and manufacturing
33
34
Appendix 2 – Turbine assembly and deconstruction
35
Appendix 3 – Turbine maintenance and use phase
At optimum wind speed of 10
m/s, site processes 100% powered
by wind energy
At a less efficient wind speed of
15 m/s, site processes only ~40%
powered by wind energy
36
Reference List Abeliotis, K & Pactiti, D. (2014) ‘Assessment if the Environmental Impacts of a Wind Farm in Greece
during its Life Cycle’, International Journal of Renewable Energy Research. 4, no.3.
Arvesen, A. Tveten, A.G. Hertwich, E.G. Stromman, A.H. (2010) ‘Life-cycle assessments of wind energy systems’, Industrial Ecology Programme, Tronheim, Norway.
Building Research Establishment (BRE). (2005) Green Guide to Specification - BRE materials industry briefing Note 3a: Characterisation. Available from: http://www.bre.co.uk/greenguide/files/CharacterisationBriefingDocumentFinal.pdf [Accessed 24 April 2015].
Country Crest. (2015) Country Crest.ie. Available from: http://countrycrest.ie/Our-Green-Ethos [Accessed 15 April 2015].
Enercon. (2012) ENERCON Product overview. Available from: http://www.enercon.de/en-en/Produktuebersicht.htm. [Date Accessed: 27 Jan 2015]
Environmental Literacy Council. (2015) Enviroliteracy.org. Available from: http://enviroliteracy.org/article.php/1029.html [Accessed 24 April 2015].
Ghenai, C. (2012). Life Cycle Analysis of Wind Turbine, Sustainable Development - Energy, Engineering and Technologies - Manufacturing and Environment, Prof. Chaouki Ghenai (Ed.), ISBN: 978-953-51-0165-9, InTech, Available from: http://www.intechopen.com/books/sustainable-development-energy-engineering-andtechnologies-manufacturing-and-environment/life-cycle-analysis-of-wind-turbine
Guinee, J.B. Gorree, M. Heijungs, R. Huppes, G. Koning, A. van Oers, L. Sleeswijk, A.W. Suh, S. Udo de Haes, H.A. (2004) Handbook on Life Cycle Assesment. Kluwer Academic publishers, Dordrecht.
Hauschild, M. Z. Goedkoop, M. Guinee, J. Heijungs, R. Huijbregts, M. Jolliet, O. Margni, M. De Schryver, A. Hmbert, S. Laurent, A. Sala, S. Pant, R. (2013) ‘Indentifying best existing practice for characteriization medeling in life cycle impact assessment’, Life Cycle Assess, 18, 683-697.
Iso14044. (2006) ‘Environmental management- Life cycle Assessment- Requirements and guidelines’, British Standard, UK.
Martinez, E. Sanz, F. Pellegrini, S. Jimenez, E. Blanco, J. (2009) ‘Life cycle Assessment of a multi-megawatt wind turbine, Renewable Energy, 34, 667-673.
Pennington, D., Potting, J., Finnveden, G., Lindeijer, E., Jolliet, O., Rydberg, T. and Rebitzer, G. (2004) 'Life cycle assessment Part 2: Current impact assessment practice', Environment international, 30(5), 721-739.
Rebitzer, G., Ekvall, T., Frischknecht, R., Hunkeler, D., Norris, G., Rydberg, T., Schmidt, W.-P., Suh, S., Weidema, B. P. and Pennington, D. (2004) 'Life cycle assessment: Part 1: Framework, goal and scope definition, inventory analysis, and applications', Environment international, 30(5), 701-720.
Tremeac, B. Meunier, F. (2009) ‘Life Cycle Analysis of 4.5 MW and 250 MW wind turbines’, Renewable and Sustainable Energy Reviews, 13, 2104-2110.
37
Wilburn, D.R (2011) ‘Wind energy in the United States and materials required for the land-based turbine industry: From 2010 through 2030’, United States Geological Survey, Scientific Investigations report, 5036.