Post on 15-Aug-2021
Avaliação de Ciclo de Vida de
uma Central Hidroeléctrica
Central de Frades, caso de estudo na EDP – Energias de Portugal, S.A.
Margarida Machado Boavida Ferreira
Nº51761
Resumo alargado
Orientador IST: Professor Doutor João Carlos Bordado
Orientadores EDP: Engenheiro Filipe Vasconcelos
Engenheira Sara Fernandes
Outubro de 2007
Paper on the Life Cycle Assessment of a hydroelectric plant – Frades Plant, case study on EDP - Energias de Portugal, S.A.
The thesis in which this paper is based on is the Life Cycle Assessment (LCA) of the
Frades hydroelectric plant, which was projected and is explored by EDP - Energias de Portugal,
S.A.. This plant was built in order to allow higher power to the Venda Nova plant, and is located
in The North region of Portugal, Minho, belonging to the Cávado river basin. This plant operates
pumping the water from the lower Salamonde reservoir to the higher Venda Nova reservoir,
when there is an excess on electric energy production (at night, since several thermo plants
keep operating and, besides that, it is very cheap to produce wind energy, therefore they keep
producing). Once the water gains potential energy from the pumping, more energy can be
produced in high consumption hours. By the construction of the excavated Frades plant, the
reservoirs height difference, which is about 400 meters in only 4,5 km, allows a gain of 191,6
MW to the system, using two reversible Francis type groups (EDP, 2006)1.
The ISO 14040 Standards give the guidelines, structure and methodology to well
conduct LCA studies. It defines these processes as the compilation of in and out flows of a
system and the assessment of the environmental impacts associated to a certain product during
its life cycle, which means the successive and interrelated stages of the product, since the
extraction of raw materials until its end of life and deposition in Nature (ISO 14040, A Standard
on Principles and Frameworks, 1st Edition, 2006)2.
The methodology adopted in the Thesis followed the prosecuted in the ISO Standards,
with the relevant particularities of an energy system. On this behalf, on what regards the Goal
and Scope, it’s important to mention that the study is meant to analyze the performance of the
plant, considering all its life cycle stages, in order to identify the aspects which could be
improved on an environmental level, informing decision makers and projectors. On the other
hand, the study intends to allow the comparison of different energy systems or reliable
strategies, improving the EDP´s investments and keeping its policy on Sustainability,
maintaining the Environment in the integrated perspective side by side to the Economical and
Social aspects.
It is very important, according to the ISO 14040, to present a clear definition of the
studied object. Therefore, the chosen object is the Frades Plant, not considering the dam and
reservoir structures, since they were already constructed and belong to the Venda Nova Plant.
Thus, its impacts would exist and be felt whether Frades plant was constructed or not. Despite
this, the decision made allows the future comparison of strategic options: the construction of an
excavated plant such as Frades, or the construction of a plant with dedicated dam and
reservoir.
The definition of the functional unit is also an important aspect in a LCA. By functional
unit it is meant the unit on which the environmental impacts are assessed (FERRÃO, 1998)3. In
this Thesis, the consequential modeling was adopted, meaning that the study intends to support
decision makers, responding to the way resources and emission flows vary according to
decisions, technologic alternatives and strategies. In fact, the Thesis didn’t mean to improve the
data basis quality on electricity, although this approach has got much interest, especially since it
allows the benefit of other LCA studies. Then, it was intended to evaluate the system fulfilling
the society need on power in high consumption hours. Therefore, the chosen functional unit was
the plant power unit, considering its operation until 2050. We could also choose to assess the
impacts on the produced energy unit, it´s a fact. Though, the produced energy is a direct
consequence of the chosen strategy for the plant. Notice once again that the plant was built to
allow a higher power to the system, does not produce on a regular basis, just aiming to cover
the energy demand on high consumption hours.
In order to assess the environmental impacts, the SimaPro 7.0 software was used,
through the Eco-indicator 99 method. Inputting materials and consumptions due to several life
cycle stages, SimaPro generates impact trees, by attributing an eco-indicator which evaluates
the environmental aspects and reveals those which should focus attention, on an environmental
level (GOEDKOOP, 2006)4.
During the inventory phase, it was necessary to define the system boundaries.
According to FERRÃO (1998)3, the LCA should consider every mass and energy flow, though,
as all studies have finite resources, the definition of the system boundaries is very important,
and should include the most relevant aspects. On this behalf, several choices have been made.
First of all, the equipments production wasn’t considered, following the advice of several
specialists who participated on a 3 day workshop, provided by United States Environmental
Protection Agency (EPA), on Electricity Data for Life Cycle Inventories. Only the production of
the materials used on the equipments has been considered, as well as all the related transports
(EPA, 2002)5.
The product and waste elimination wasn´t considered as well, since, on one hand, the
demolition phase in hydroelectric plants is not relevant as, most of the times, it simply doesn’t
occur. On the other hand, the real important waste management on electric systems refers to
thermo plants, with the production of fuel ashes (SETTERWALL, 2002)6.
Alike, the manufacture of the auxiliary products, as the machines used during the
construction phase, was not included in the system boundaries, because its life time is much
bigger than the period the machines were used on construction works. The defined boundaries
should only consider the equipments or machines built in order to be used specifically on the
project (EPA, 2002)5.
According to what is recognized in the ISO Standards, criteria should be defined in
order to include, or not, certain aspects on the assessment. On what regards this matter, in the
Thesis, the equipments and its materials were excluded when its joint mass summarized about
5% of the total mass of the plant. However, this exclusion was not precise on a mathematical
level. Yet, it was a result of the consult of several EDP specialists and sensitivity analysis. On
what concerns the energy flows, the inventory tried to be exhaustive, as well as the inventory of
environmentally relevant substances. On what regards the parallel life cycles, meaning the life
cycle of materials and services used directly in the product in which the LCA is focused,
GOEDKOOP (2006)4 says that the foreground data should be obtained considering specifically
the object in study. However, an energetic system is much more complex than a conventional
product and, therefore, it is impossible to perform LCA studies for each material or equipment.
Despite this, in the Thesis, the inventory of materials was specific enough, meaning that most of
the times, in order to inventory the materials used, the real equipments and their catalogues
were analyzed.
In the matter of transports, some difficulties have been needed to be solved. The data
base (Ecoinvent) of the software used to assess environmental impacts hadn’t available for
simulation the 100 tones lorries, only 16, 25 and 40 tones ones. Consequently, by contacting a
Portuguese transportation company, important information was obtained. A full 100 ton lorry
emits about 260 kg CO2/100 km, and consumes 85 L of diesel fuel. When it rides empty the
consumptions decrease to about 60 L/100 km. Therefore, it’s reasonable to assume that the
empty lorry is responsible for the emission of about 180 kg CO2/100 km. Researching the Eco-
invent data base, the needed data about the emissions of the other lorries was obtained. Then,
considering a linear relationship between the lorries load and their CO2 emissions, the following
functions were obtained:
With the information on the previous graphic, the simulations on transportation were
made. Notice that the simulations of the transportations with 100 tones lorries were made using
the 40 tones one, inputting a modified distance, for which the CO2 emissions are equal. It’s a
very simple strategy. The same methodology was used whenever a lorry wasn’t 100% loaded.
One should realize that CO2 may well be a good indicator on the major impacts on transport.
On what regards the construction and equipment production phase of the life cycle, the
inventory was divided in the various supplies that occurred: building work order, including the
excavation works, the construction of the plant, building and other infra-structures. The other
CO2 emissions vs lorries load
y = 0,0014x + 0,6087
y = 0,003x + 0,9624
y = 0,0024x + 0,81
y = 0,008x + 1,8
0
0,5
1
1,5
2
2,5
3
0 20 40 60 80 100
Load (%)
CO2 emissions (kg/km)
16 ton lorry
28 ton lorry
40 ton lorry
100 ton lorry
Figure 1 – CO2 emissons vs lorries load. Reference: CO2 emissions of 16, 28 e 40 t lorries obtained from Ecoinvent; 100 t lorries emissions obtained from Transportes Gonçalo, SA.
supplies were: the hydro mechanical equipments, like duckboards, hydraulic gates of the water
in and outtake, the rolling bridge, with its two cars and structure; the electric transformers, and,
finally, the complementary production installation (CPI), including the centered command and
control installations, the servers and its peripheries, teleregulation command, remote
communication units, level and pressure measure equipments, distributed command and
control installations, pumping and drainage installations, ventilation and air conditioning, and,
finally, the general use installations, such as the illumination system, telecommunication, and
safety installations. The several inventories were prosecuted by studying the documents related
to the project, maintenance manuals, and brochures and catalogues of the equipments used.
The major inventory was, as expected, the CPI’s, since it is very large and complex. On the
other hand, some needed information wasn’t available on the documents which access has
been given. Therefore, through advisory and several meetings with EDP specialists, for those
equipments on which data wasn’t as complete as desirable, materials proportions were
assumed. The table presented bellow shows all these assumptions:
Equipment Materials proportion
Electric equipment 60% - Iron; 20% PVC; 20% - Copper
Batteries 90% - Plumb; 10% - PVC + Electrolyte fluid (30% electrolyte and
70% destilled water)
Circuit breakers 50% - Iron; 50% - Copper
Transformers with oil 70% - Iron; 20% - Oil; 10% - Insulator (70% paper and 30% wood)
Transformers 40% - Iron; 60% - Copper
Disconnectings 60% - Iron; 20% - Copper; 20% - Chain
Reactances 90% - Copper; 10% - Iron
Ventilators 90% - Iron; 10% - Copper
Electropumps 80% - Iron; 20% - Copper
Accessory on drainage installation 20% of the pipe weight
Lamp armours 60% - Iron; 30% - Copper; 10% - PVC
The materials of other equipments were more easily obtained through the documents
researched. The whole inventory of this supply was made through the definition of categories of
equipment, in which the materials and their proportional was alike. For instance, one of the
categories was electronic equipment, which included, computers in general, servers, etc..
The data related to electric cables was obtained with direct contact with the suppliers of
the CPI. Since there wasn’t available any information, on a digital or other format, that
information couldn’t be obtained other way. Notice the importance of cables in an excavated
plant like this: in this case study, the cables length is about 187 km, meaning a very relevant
amount of Copper, Aluminium and PVC.
The amount of materials of drainage and air conditioning pipes was obtained simply by
checking the nominal diameter and the pipe lengths, and then, it was quite simple to get the
amount of PVC and Steel.
Table 1 – Equipment materials and their proportion
On what regards the plant operation stage, the fixed and variable consumptions were
identified. On what concerns the SF6 used as electric insulator on transformers, a research has
been made in order to predict its use, during the exploration phase. The table below shows the
emission factors considered:
Equipment Life cycle stage
Emission factor
Uncertainty factor
Majorated emission factor
Observations
SF6
production
0,1% 50% 0,15% -
Circuit Breakers production, installation
and comissioning
29% 50% 43,5% After 1995; before that, the
leakage was higher.
Leakage and maintenance
20% 50% 30% -
Circuit breakers
Majorated emission factor
considered
~74% Since there were unconsidered impacts, the choice was to major
these.
SF6
production
0,1% 50% 0,15% Not relevant.
GIS equipment production, installation
and comissioning
12% 25 + 25 = 50%
18% 6 % refer to prodcution emissions
and the remainers refer to emissions on site.
Leakage and maintenance
3% 25% 3,75%
Since the equipment are new (after 1980). Leakage rates of
about 0,5% per year, considereing 30 years of life time.
GIS (gas-insulated Switcgear) equipments
Majorated emission factor
considered
21,9 ~ 22% Since there were unconsidered impacts, the choice was to major
these.
Still relating the operation life cycle stage, it is relevant to mention that the equipment
substitution, since it is highly speculative, wasn’t considered, with the exception of electronic
equipment, which substitution is absolutely predictable. On what regards the lamps substitution,
it’s important to notice that, although there are hundreds of lamps in Frades plant, since there
are many km of illuminated excavated tunnels, this particularity is well represented considering
the electric energy used during operation. Therefore, and once the lamps life cycle was
revealed to be insignificant, the lamps substitution wasn’t modelled.
Meanwhile, inventoried all materials, energy consumption and other relevant
environmental aspects, impacts could finally be assessed. In order to do that, as previously
Table 2 – SF6 emission factors, Reference: adapted from Revised
1996 IPCC Guidelines for National Greenhouse Inventories 7
mentioned, the SimaPro 7.0, by Pre-Consultants, was used. The following graphics show the
obtained results for the most relevant Frades plant supplies:
On what concerns the explosives, it is relevant to mention that the software used hadn’t
the explosions available on its data base. Therefore, a research has been made. Table 3 is the
result of it, and its contents were used to create the process, filling it in the data base:
Emission factors
Explosive Composition
Carbon
monoxide
(kg/ton)
Nitrogen
oxides
(kg/ton)
Metane
(kg/ton)
Hidrogen
sulfur
(kg/ton)
Sulphur
dioxide
(kg/ton)
Gelamonite 20-100% de nitrogliceryn
52 26 0,3 2 1
Amonite Amonium Nitrate
34 8 - - 1
Relative contribution from environmental aspects
of the construction works on its impacts
0%
10%
20%
30%
Reinforcing
steels
Portland
Cement
Lorry
transportations
Electricity
Diesel burning
Explosives life
cycle
Diesel life cycle
Ship
transportation
Gelamonite
explosions
Amonite
explosions
Environmental aspect
Contribution
Figure 2 – Relative contribution from environmental aspects of the construction works on its impacts, Reference: adapted from SimaPro 7.0, Eco-indicator 99 method output
Table 3 – Emission factors of the used explosives, Reference: National Pollutant Inventory, Australian
Government, Emission estimation technique manual for Explosion Detonation and Firing Ranges 8
Relative contribution from environmental aspects
of the complementary production installation on its impacts
0%10%20%30%40%50%60%70%80%
Copper
Inox Steel
PVC
Iron
Aluminium alloy
Lorry transportation
Steel
Electronic equipment
Environmental aspect
Contribution
Finally, it might be interesting, on what regards the construction and equipment
production phase, to observe the relative impacts of each supply on the general impact of this
life cycle phase. Therefore, the following figure is presented:
Figure 3 – Relative contribution from environmental aspects of the complementary production installation on its impacts, Reference: adapted from SimaPro 7.0, Eco-indicator 99 method output
Relative contribution from environmental aspects
of the reversible groups on its impacts
0%
10%
20%
30%
40%
50%
60%
70%
Steel Lorry
transportation
Inox Steel Ship
transportation
Iron
Environmental aspect
Contribution
Figure 4 – Relative contribution from environmental aspects of the reversible groups on its impacts, Reference: adapted from SimaPro 7.0, Eco-indicator 99 method output
It is also interesting to analyse the direct output of the Software, on what concerns the
attribution of the Eco-indicator.
One can see that the major supply, on
what concerns environmental aspects, is the
construction works, specially, as we can conclude
from the study of Figure 2, as a consequence of
the use of reinforcing steels and Portland cement.
The worse impact category is the fossil fuel one,
and we can clearly see, by watching figures 3, 4
Environmental aspect Contribution
Electricity consumption 97,20%
Diesel burning 1,19%
Electronic material substitution 0,47%
SF6 use in GIS equipment 0,46%
Plastics consumption 0,42%
Diesel life cycle until storage 0,39%
Lubrificant oils 0,29%
Use of detergents 0,08%
Figure 6 – Relative contribution of every supply on the impacts of the construction and equipment production phase, and the single score on every impact category, Reference: SimaPro 7.0, Eco-indicator 99 method output; In order of appearance:
construction works, hydro mechanical equipment, reversible groups, CPI, rolling bridge, transformers
Table 4 – Relative contribution of environmental aspects on impacts from the operation phase,Reference: adapted from
SimaPro 7.0, Eco-indicator 99 method output
Relative contribution of every supply on the impacts of the
construction and equipment production phase
Construction works; 72,40%
Reversible Groups; 13,40%
CPI; 11,40%Rolling brigde; 0,44%
Hydro mechanical equipment; 0,81%
Transformers; 1,66%
Figure 5 – Relative contribution from supplies on the global production stage impacts, Reference: adapted from SimaPro 7.0, Eco-indicator 99 method output
and the previous one, that the category of minerals is represented mainly from the reversible
groups and CPI supply, because of the use of steel and copper, respectively.
On what regards the operation stage, the most relevant impacts identified were the
consumption of electric energy, as the table 4 proves.
Finally, it’s important to know the relative contribution, on the global impact, of the
construction and equipment production and operation phases. In order to do that, the graphic
presented bellow gives a useful idea:
We can also analyse
the relationship between the
life cycle stages and the
impact categories. Notice that
the electric energy
consumption is the major
responsible on the impacts
related to fossil fuels.
Figure 7 – Relative contribution of the two phases on the global impacts, Reference SimaPro 7.0, Eco-indicator 99 method output; From top and from left to right: 1 MW of Frades plant life cycle, Construction and Equipment Production stage, operating stage, Construction works, Reversible Groups and CPI.
Figure 7 – Relative contribution of the two phases on the global impacts and single score, Reference SimaPro 7.0, Eco-indicator 99 method output; From left to right: construction and equipment production phase, operating phase .
As a conclusion, the following topics are interesting to discuss:
- On the construction and equipment production phase, the most relevant supply was the
construction works one, specially because of the use of reinforcing steel and Portland cement,
follwed by the supply of Reversible groups and CPI, because of the consumption of steel and
copper, respectively;
- The inventory of the CPI is the most difficult one, as it involves variable components.
However, the impacts from this supply weren’t that relevant, considering the whole life cycle
(5% of global impacts). Therefore, it might be a good choice not to consider this inventory,
majoring the final result in about 5%;
- Notice that the relative contribution of the two life cycle phases depend on the plant life time
one assume. Consequently, the result has to be used with that knowledge;
- It’s also important to have in mind that, since the chosen functional unit was the power unit,
the impacts assessed increase with the plant life time assumed. In fact, that really doesn’t
happen, since as long as the plant operates, there is no need to build another one. Thus, the
result has to be used carefully and the comparisons shall be made only with plants with the
assumption of an identical life time. Otherwise, one can evaluate the impacts per year of
operation;
- The electric energy used does not include the energy used to pump the water (300 GWh per
year). The energy used to do so is energy that is already produced in thermo plants (they
can’t stop even during low consumption hours) or in wind turbines. Therefore, it is not correct
to input those impacts. However, it would be interesting to perform a LCA on electricity
production, in order to assess the impacts, on every kWh produced at high consumption
hours, considering the energy that is also produced at night, imputing those impacts;
- According to RIBEIRO (2003)9, the major contribution on the impacts of a hydroelectric station
is the construction phase one. In this study, this didn’t happen (only 44% of the impacts
referred to this phase), but there are some good explanations for that. First of all, the dam and
reservoir structure wasn’t considered, for the reasons previously mentioned. On the other
hand, this plant, being excavated, has several particularities. About 23% of the electricity
consumption (the major environmental aspect of the operation stage) is due to those
particularities: tunnels illumination, drainage, and ventilation.
References
- 1 – EDP, Centros Produtores, 2006;
- 2 – INTERNATIONLA STANDARD, ISO 14040, Environmental Management – Life Cycle
Assessment – Principles and Framework, 2nd edition, 2006;
- 3 - FERRÃO, Paulo Cadete, Introdução à Gestão Ambiental – A avaliação de ciclo de vida de
produtos, IST Press, 1998;
- 4 - GOEDKOOP, Introduction to LCA with SimaPro 7, Pre-consultants, 2006;
- 5 - EPA, Report on the International Workshop on electricity data for life cycle inventories,
2002;
- 6 – SETTERWALL, input to the EPA Report on the international workshop on electricity data
for life cycle inventories, 2002;
- 7 – IEA/OECD 1996 IPPC Guidelines for National greenhouse gas inventories, Paris, 1996;
- 8 – ENVIRONMENT AUSTRALIA, NPI, Emission Estimating Technique manual for explosives
for detonation and firing ranges, 1999;
- 9 – RIBEIRO, Inventário de ciclo de vida da geração hidreléctrica no Brasil – usina de Itaipu:
primeira aproximação, 2003.