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.