Life Cycle Ass of 2.7 kWp German

7/31/2019 Life Cycle Ass of 2.7 kWp German

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Life cycle assessment study of solar PV systems: An example

of a 2.7 kWp distributed solar PV system in Singapore

R. Kannan a, K.C. Leong a,*, R. Osman a, H.K. Ho a, C.P. Tso b

a School of Mechanical and Aerospace Engineering, Nanyang Technological University,

50 Nanyang Avenue, Singapore 639798, Singaporeb Faculty of Engineering and Technology, Multimedia University, Jalan Ayer Keroh Lama, 75450 Melaka, Malaysia

Received 30 July 2003; received in revised form 23 March 2005; accepted 5 April 2005

Available online 13 June 2005

Communicated by: Associate Editor Aaron Sanchez-Juarez

Abstract

In life cycle assessment (LCA) of solar PV systems, energy pay back time (EPBT) is the commonly used indicator to

justify its primary energy use. However, EPBT is a function of competing energy sources with which electricity from

solar PV is compared, and amount of electricity generated from the solar PV system which varies with local irradiation

and ambient conditions. Therefore, it is more appropriate to use site-specific EPBT for major decision-making in power

generation planning. LCA and life cycle cost analysis are performed for a distributed 2.7 kW p grid-connected mono-

crystalline solar PV system operating in Singapore. This paper presents various EPBT analyses of the solar PV systemwith reference to a fuel oil-fired steam turbine and their greenhouse gas (GHG) emissions and costs are also compared.

The study reveals that GHG emission from electricity generation from the solar PV system is less than one-fourth that

from an oil-fired steam turbine plant and one-half that from a gas-fired combined cycle plant. However, the cost of

electricity is about five to seven times higher than that from the oil or gas fired power plant. The environmental uncer-

tainties of the solar PV system are also critically reviewed and presented.

2005 Elsevier Ltd. All rights reserved.

Keywords: Solar PV; Greenhouse gas emissions; Life cycle assessment; Life cycle cost analysis; Distributed generation

1. Introduction

Global warming caused by greenhouse gas (GHG)

emissions from combustion of fossil fuels has become

an important environmental issue in the global arena.

Unlike in the 1970s, the motivation now has been

changed from the perceived fossil fuel depletion to

global warming concerns. As a result, non-fossil energysources are explored, and power generation from solar

photovoltaic (PV) systems plays a prominent role.

Although the operation of solar PV system is free from

fossil fuel use, a considerable amount of energy is con-

sumed in the manufacturing of solar PV modules. To

quantify the energy consumed in the manufacturing of

solar PV modules, numerous life cycle assessment

(LCA) studies have been carried out (Hagedorn, 1989;

Phylipsen and Alsema, 1995; Nieuwlaar et al., 1996;

0038-092X/$ - see front matter 2005 Elsevier Ltd. All rights reserved.

doi:10.1016/j.solener.2005.04.008

* Corresponding author. Tel.: +65 6790 5596; fax: +65 6792

2619.

E-mail address: [email protected] (K.C. Leong).

Solar Energy 80 (2006) 555563

www.elsevier.com/locate/solener
mailto:[email protected]:[email protected]


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Kato et al., 1997; GEMIS, 2002; Karl and Theresa,

2002; Gagnon et al., 2002). These studies expressed the

energy use in terms of energy pay back time (EPBT),

which is the time required for the solar PV module to

generate the equivalent amount of energy consumed in

its manufacturing processes. A wide variation in the

EPBT is found in these studies. Corkish (1997) andKarl and Theresa (2002) also provided summaries of

EPBT of solar PV modules. As an alternative index,

Gagnon et al. (2002) used the energy payback ratio

which is the ratio between energy produced during the

normal life span of the power generation system and

energy required to build, maintain and fuel the genera-

tion equipment.

From a broad view, EPBT is a function of the

amount of energy used for manufacturing solar PV

modules, quantity of electricity generated from the solar

PV system and competing energy sources with which

electricity from the solar PV system is compared.Although the energy consumption during manufactur-

ing of solar PV modules does not vary significantly with

geographical location, the quantity of electricity gener-

ated from a solar PV system depends on its geographical

location, e.g. solar irradiation and ambient temperature.

In LCA studies, the efficiency of the solar PV module is

considered to be its efficiency under the standard test

conditions (STC) of 1000 W/m2 and 25 C. However,

in actual operation of a solar PV system, STC do not

prevail, particularly under tropical high humidity

weather conditions where the ambient temperature is

often above 30 C. It has been recorded that solar PV

modules reached a temperature higher than 60 C during

peak radiation hours in equatorial Singapore. Thus, its

actual operating efficiency is lower than that at STC.

Therefore, none of the above factors can be considered

in isolation, and it is more appropriate to use EPBT

from local studies for more informed decision making.

Thus, there is a need for site-specific life cycle evaluation

to generate insights, at least to represent a region. This

paper describes a LCA study carried out for a grid-

connected 2.7 kWp mono-crystalline solar PV system,

which has been operating in Singapore since May 2002.

To consider its economic implications, a life cycle cost

analysis (LCCA) is also included in this study. The LCAand LCCA results are compared with that of an oil-fired

steam turbine and gas fired combined cycle plant.

2. Singapore power sector

Singapore is one of the most industrialised and

urbanised economies in South-East Asia with an area

of 697 km2 and a population of 4.18 million. In 2003,

the countrys gross domestic product was about

US$100 billion (Singapore Department of Statistics,

2004). Singapores total electricity consumption in 2003

was about 32 TWhe (EMA, 2004a) and is projected to

grow at an annual rate of 35% during 20032013

(APERC, 2003). About 97% of its power is generated

from imported oil and natural gas while the rest is from

waste incineration plants. In 2003, Singapore had

8919 MW installed power generating capacity consisting

of 53% steam turbine and 30% combined cycle plants(EMA, 2003). However, electricity generation from nat-

ural gas-fired combined cycle plants accounted for 61%

(EMA, 2004b). Singapores wholesale electricity market

(National Electricity Market of SingaporeNEMS) be-

gan its operations in 2003 (EMC, 2003). In the deregu-

lated electricity market, the power sector faces

heightened competition and market demands for cost-

effective power generation.

Due to Singapores small geographical area, non-fos-

sil based energy sources for the power generation are

limited. The only known source of renewable energy is

solar radiation. The country receives an annual solarradiation of 1635 kWh/m2 (at Changi Airport [1 22 0

N, 103 59 0 E]) (Meteorological Service Singapore,

1997). However, large-scale power generation from solar

PV systems is limited because of constraints in space.

Thus, only small-scale solar PV systems can be consid-

ered for distributed generation. As a demonstration

cum research project, the Building and Construction

Authority (BCA) of Singapore installed an 8.9 kWpgrid-connected solar PV system comprising 2.7 kWpmono-crystalline, 3.066 kWp poly-crystalline and 3.12

kWp CIS thin-film to study their operational perfor-

mances and cost-effectiveness (BCA, 2004). This study

is based on the 2.7 kWp mono-crystalline solar PV

system.

2.1. Description of the solar PV system

The 2.7 kWp solar PV system consists of 36 mono-

crystalline modules (12 V, 75 Wp) mounted on a build-

ing rooftop with aluminium supporting structures and

concrete blocks for the base (see Fig. 1). The 12 mod-

ules are connected in series to generate 204 V DC

(900 Wp) at their rated voltage (under STC). Three

strings, each having 12 modules, are connected to three

inverters of 1.5 kVA capacity. The AC output from theinverters is connected to the three phases of the grid.

Control units are installed in such a way as to use

the electricity from the solar PV system firstly for the

local load, i.e., within the building. Since electricity

generated from the solar PV system is a small fraction

of the buildings power demand, all the generated elec-

tricity is consumed within the building and hardly any

electricity is exported (sold) to the grid. A data logger

is installed to record electrical (power, voltage, current,

power factor, etc.) and meteorological data (radiation,

temperatures, wind speed, rain fall, humidity, etc.).

Three phases of the inverters DC inputs and AC out-

556 R. Kannan et al. / Solar Energy 80 (2006) 555563


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puts are measured, and six sensors are installed to mea-

sure the temperature of the mono-crystalline solar PV

modules.

The annual net electricity generated from the solar

PV system during June 2002 to May 2003 was

2623 kWhe and 2581 kWhe during June 2003 to May

2004. For the calculation of life cycle energy use, emis-

sions and cost, an average annual power generation of

2600 kWhe is used. The average net conversion effi-

ciency of the solar PV system (solar radiation to AC

power output) varied between 7.3% and 8.9% while the

measured efficiency of the inverter is about 90%. Based

on the manufacturers specifications, the efficiency of

the solar PV module under STC is 11.86%.

3. Life cycle assessment of the 2.7 kWp solar PV system

In this study, the conventional LCA procedure viz.

goal and scope definition, life cycle inventory, impact

assessment and improvement assessment, is used. Theresearch methodology is described in detail in the

authors previous paper (Kannan et al., 2004). The aim

of this LCA study is to quantify the non-renewable pri-

mary energy use and GHG emissions from electricity

generation from the solar PV system. All indicators of

the study such as energy use, emissions and cost are in-

dexed based on the functional unit which is defined as 1

kW h of AC electricity. Manufacturing of solar PV mod-

ules and balance of the system (BOS) such as inverters,

supporting structures and their accessories, are included

in the system boundary. Fig. 2 shows the LCA

boundary.

4. Life cycle inventory

The life cycle of the solar PV system is considered in

three phases, viz. construction, operation and

decommissioning.

4.1. Material inventory

In the construction phase, solar PV modules, invert-

ers and aluminium and concrete supporting structures

are the major components. Fig. 3 shows the materials

used for the solar PV system. In the operation and

decommissioning phases, hardly any material inflow is

involved.

4.2. Life cycle energy use

As can be seen from the material use, the construc-

tion phase is material intensive and therefore energy

intensive. Numerous studies have been carried out to

estimate the energy consumption in the manufacturingof mono-crystalline solar PV modules (Hagedorn,

1989; Kato et al., 1997; GEMIS, 2002; Karl and The-

resa, 2002; Mathur et al., 2002). These are summarised

in Table 1. It can be seen that the energy consumption

for manufacturing of solar PV modules varied between

11 and 45 MWht/kWp. The variations can be attributed

to technological assumptions and system boundary. The

study of Karl and Theresa (2002) is specific to the solar

PV module used in the solar PV system and its specific

energy consumption is 16 MWht/kWp. This value is

adopted for this LCA study. For aluminium and con-

crete supporting structures, the energy use is estimated

Fig. 1. Solar PV modules mounted on the building rooftop.

R. Kannan et al. / Solar Energy 80 (2006) 555563 557


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based on their specific energy consumptions (GEMIS,

2002). The specific energy consumption for productionof inverters is 0.17 MWhe/kWp (Kato et al., 1997).

Although the energy consumption data of Kato et al.

(1997) are denominated as electrical energy (MWhe), it

is assumed to be the same magnitude in thermal energy

(MWht) as corroborated by other studies shown in

Table 1.

In the operational phase, there is no external source

of energy supply. Though control systems are installed,

they draw energy from the solar PV module itself.

In the decommissioning phase, it is assumed that

the solar PV module would be landfilled after removing

the aluminium frames (see Section 6). Therefore, in the

decommissioning phase, energy would be used for recy-

cling of aluminium supporting structures and module

frames. 10% of the module weight is considered as the

aluminium frame (Phylipsen and Alsema, 1995). It is as-

sumed that 90% of the aluminium would be recycled

with 90% recovery rate. The recovered aluminium is

debited from the construction phases aluminium use.

Thus, the energy used of recycling of aluminium is

shown separately (see Fig. 4).

Energy used in transporting of all the materials asso-

ciated with the solar PV system is estimated based on

specific transportation energy (MJ/t-km) from GEMIS

(2002). The solar PV modules and inverters were im-

ported from the USA and Germany, respectively and as-

sumed to be transported by ship. The other materialswere obtained locally and transported by trucks.

From the sum of the energy used in the three life

cycle phases and transportation, energy use per func-

tional unit (kW he) is calculated as 2.94 MJt/kWhe.

The manufacturing of solar PV modules accounted for

81% of the life cycle energy use. Fig. 4 shows the distri-

bution of life cycle energy use.

4.3. EPBT analysis of the solar PV system

Electricity generated from the solar PV system is

compared with that from a 250 MW (centralised) oil-

Supporting

structures

Solar PV

modules

Construction

phase

Operational

phase

Decommissioning

phase

Electricity

Material (steel,

glass, aluminium,

cement, etc.)

production

Invertors

System boundary

Solar

radiation

Metal

recycling

Wastes

disposal

Silicon production

PV cell

manufacturing

Fabrication of PV

modules

Energy

Natural

resources

GHG*

Emissions

*All the input streams have their corresponding GHG emission output streams

Energy

Energy

Energy

Energy

Fig. 2. LCA boundary of the solar PV system.

Fig. 3. Material use in the solar PV system.



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fired steam turbine plant with a net efficiency of 33%.

The EPBT of the solar PV system is calculated to be

6.74 years. Compared to the solar PV modules lifetime

(expected to be 25 years), the solar PV system could still

generate substantial amount of electricity.

In Singapore, hidden1 energy use in electricity gener-

ation from oil-fired steam turbine plant is about 8.8% of

operational phase fuel consumption (Kannan et al.,

2004). If the hidden energy use is considered in the

EPBT calculation, then the EPBT becomes 6.19 years.Since the solar PV system is used as a distributed

power system, no transmission and distribution (T&D)

loss is incurred. If the T&D loss, which is about 4% in

Singapore (World Bank, 2004), and energy used for

development of T&D networks are accounted, the

EPBT will be lower. When the 4% T&D loss alone is

considered, then the EPBT will be 5.87 years. In other

words, the solar PV system consumes about 23% of

the primary energy consumed in oil-fired steam turbineplant.

If the electricity from the solar PV system is com-

pared with a natural gas-fired combined cycle plant with

a net efficiency of 50%, then the EPBT will be 10.2 years.

It can be seen that the EPBT varies with type of

power generation technologies with which solar PV is

compared and their operational boundary. Therefore,

due consideration should be given when comparing

EPBT with other studies.

4.4. Life cycle GHG emission

In the life cycle of solar PV system, GHG emission

potentially occurs from the energy used for the manufac-

turing of solar PV modules and the BOS. Since primary

sources of energy usage are unknown, CO2 emission is

estimated based on the average emission factor (IPCC,

1996) of coal, oil and gas as in the studies by van Mar-

greet et al. (1994) and Phylipsen and Alsema (1995).

CH4 or N2O emissions are ignored due to uncertainties

in primary sources of energy use and its relatively insig-

nificant magnitude. The GHG emission from electricity

generation from the solar PV system is about 217 g-

CO2/kWhe.

The life cycle GHG, namely CO2, CH4 and N2Oemission from the oil-fired steam turbine is 937 g-CO2/

kW he (Kannan et al., 2004). When the T&D loss is in-

cluded, it would be about 976 g-CO2/kWhe. If the

GHG emission from the solar PV system is compared

with the oil-fired steam turbine plant, it is less than

one-fourth of the latter system.

The life cycle emission from natural gas-fired com-

bined cycle with a net efficiency of 50% is estimated to

be 493 g-CO2/kWhe including the T&D loss (Kannan

et al., 2005). If the emission from the solar PV system

is compared with the combined cycle plant, it is less than

one-half of the latter system.

Table 1

Life cycle energy use in manufacturing of mono-crystalline solar PV module

Source Primary energy use Processes included in the study

Hagedorn (1989) 1117.5 MWht/kWpa Exploitation and preparation of raw materials, process energy, hidden energy

of input materials and production equipment

Kato et al. (1997) 17.70 MW he/kWpb From quartz (production of MG silicon) to module fabrication

12.4 MW he/kWp Off-grade silicon (from semiconductor industry) to module fabrication

Mathur et al. (2002) 40.55 MW ht/kWp Manufacturing of silicon wafers to modules fabrication

Karl and Theresa (2002) 16 MWht/kWpc From growth of the silicon crystalline ingot to module fabrication

GEMIS (2002) 13.78 MW ht/kWpd From mineral sand to module fabrication

a In different technology level in different time frame.b Based on this study, the energy pay back time was 15.5 years for 1427 kWh/m2/year solar radiation.c For Siemens SP 75 module that is adopted for this LCA study.d Estimated from the energy requirement for production of mono-crystalline module (131.23 MWh t/ton) and the module require-

ment (105 ton/MWp).

Fig. 4. Distribution of life cycle primary energy use in solar PV

system.

1 It is the energy used in the construction of power plant,

manufacturing of plant equipment and upstream processes of

fuel-oil production.



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4.5. Improvement assessment

Three scenarios are studied for reducing the primary

energy use of the solar PV system. These are (i) technol-

ogy improvement in the manufacturing of solar PV

modules, (ii) using alternative supporting structures

and (iii) achieving better solar PV module efficiency.For these three options, the EPBT of the solar PV sys-

tem are estimated with reference to the oil-fired steam

turbine with a net efficiency of 33%.

4.5.1. Technology improvement

Manufacturing of the solar PV modules accounted

for 81% of the life cycle energy use (see Fig. 4). Improve-

ment in solar PV module production technology or mass

production would lead to a reduction in energy usage.

According to the manufacturers, energy usage could be

reduced by 50% if the production is doubled. If the pri-

mary energy use in the manufacturing of solar PV mod-ule were to be reduced by 50%, then the life cycle

primary energy use would reduce to 1.7 MJt/kWhe and

the EPBT would be 3.5 years. In such a case, the

GHG emission would be about 129 g-CO2/kWhe.

4.5.2. Changing of supporting structure

The aluminium supporting structure accounted for

about 10% of the life cycle energy use and the recycling

of aluminium also accounted for another 7% (see Fig. 4).

Instead of the aluminium structure, a concrete structure

could be used and energy use could be further reduced.

If the aluminium usage for supporting structure were to

be reduced to 10% of the current aluminium use, then

the life cycle primary energy use would decrease to

2.38 MJt/kWhe and the EPBT would be 4.8 years. The

GHG emission would be about 177 g-CO2/kWhe. Alter-

natively, solar PV modules can be integrated into the

building thereby minimising energy use and cost of sup-

porting structure.

4.5.3. Efficiency improvement

Under the STC, the efficiency of the solar PV module

used in the solar PV system is 11.86%. However, its ac-

tual operational efficiency is between 7.3% and 8.9%

including inverter and line losses of 10%. A lower oper-ating efficiency could be due to high ambient- and mod-

ule temperatures, with the latter reaching above 60 C

during peak radiation hours. The power output of a

solar PV module decreases by about 0.5% for every

degree Celsius rise in cell temperature (BCA, 2004). If

the efficiency of the solar PV system were to be increased

to 10.6% by natural cooling of modules or other means,

the life cycle energy use would reduce to 2.2 MJt/kWheand the EPBT would be 4.5 years. The GHG emission

would be about 165 g-CO2/kWhe.

From the above three scenarios, it can be seen that

there is a potential to reduce the life cycle primary en-

ergy use. Life cycle energy use, EPBT and GHG emis-

sion from the solar PV system under the various

combinations of the above scenarios are presented in

Table 2. It can be seen that if all the above three scenar-

ios were to be achieved, the primary energy use would

reduce to as low as 0.9 MJt/kWhe and the EPBT would

be 1.8 years.

5. Life cycle cost analysis

Costs involved in the three life cycle phases of the so-

lar PV system are categorised as capital, operation and

maintenance (O&M) and decommissioning costs (see

Kannan et al., 2004 for LCCA formula). For the cost

of the solar PV system, the current market prices of 5

US$/Wp for solar PV modules and 0.83 US$/Wp for

inverters are used (Solarbuzz, 2005). The costs of sup-

porting structures and installations are adopted fromthe actual project costs (@ 1.63 S$ = 1 US$) (BCA,

2004). The total capital cost of the solar PV system

works out to be about 7.5 US$/Wp and its breakdown

is shown in Fig. 5. For the capital cost, an annual inter-

est of 5% payable over the solar PV system s operational

life time of 25 years is used in LCCA.

Since there is no fuel consumption in the operational

phase, no energy costs occur in this phase. Although the

solar PV system does not require regular maintenance,

fortnightly cleaning of the solar PV module is carried

out to reduce dust or dirt deposition on the solar PV

modules. The cost of fortnight cleaning was estimated

based on a large number of installations to minimise

the manpower cost. It worked out to be 0.17% of the cap-

ital cost, which took into account an annual escalation

rate of 1%. Cost involved in the dismantling of the solar

PV system is estimated to be about US$ 7502. I t is

assumed that the solar PV modules would not have any

salvage value. Instead, there may be costs in disposing the

solar PV module. However, such costs are not considered

due to a dearth of information. Nonetheless, a salvage

value of US$ 4603 is used which took into account the

aluminium supporting structures and aluminium frames

of the solar PV modules. The net cost incurred in the

decommissioning phase which took into account a dis-count rate of 1%.

The life cycle cost of electricity generation from the

solar PV system is 57 cents/kWhe and its distribution

is shown in Fig. 6. The capital cost accounted for 96%

of the life cycle cost. Due to huge capital cost of the solar

PV system, the interest on the capital plays a significant

2 Cost data was obtained from the system suppliers through

personal communication.3 Based on market value of recyclable aluminum @ US$ 860

per tonne.



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role in deciding the cost of electricity. A scenario is stud-

ied for a range of interest rates as shown in Fig. 7. It can

be seen that the cost of electricity is about 33 cents/kWhe

at zero interest rate.The prices of solar PV system have been historically

declining at about 4% per annum and this decline is ex-

pected to continue (Solarbuzz, 2005). A scenario is stud-

ied to estimate the life cycle cost of electricity generation

from the solar PV system at various solar PV system

costs. Although the solar PV module and inverter costs

would decline in the future, the cost of supporting struc-

ture or installation cost or O&M cost would not change

significantly. Thus, the cost scenario is studied by chang-

ing the cost of solar PV modules and inverters while the

rest of the costs remain unchanged. The results are pre-

sented in Fig. 7. In the legend of Fig. 7, costs of the solar

PV module and inverter are shown in US$/Wp while

BOS is the cost of supporting structures and installa-

tion cost i.e. about 1.68 US$/Wp.

5.1. Solar PV versus conventional power generation

Life cycle cost of electricity generation from the oil-

fired steam turbine plant is about 7.03 cents/kW he based

on current market price of fuel-oil price of 200 US$ per

tonne (Kannan et al., 2004; 10X Group, 2005). There-

fore, the cost of electricity generation from the solar

PV system is about eight times higher than that from

the oil-fired steam plant. Since, the solar PV system is

used as a distributed power generation system, there is

no T&D loss or costs involved in the establishment of

the T&D network. In Singapore, the low tension (LT)

flat rate transmission cost is about 3.4 cents/kWh (Sin-gapore Power, 2004). If it is considered as the T&D cost,

then the cost of electricity generation from the solar PV

system is about 5.5 times that of the oil-fired power

plant.

The life cycle cost of electricity from the natural gas-

fired combined cycle plant is about 4.94 per kWhe at a

gas price4 of US$ 5.34 per MMBTU (Kannan et al.,

2005). It would be 8.34 per kWhe if the T&D cost is

included. The cost of electricity from the solar PV sys-

tem will then be about seven times higher than the

gas-fired combined cycle plant.

In late 2004, oil prices surged to a new high of US$55per barrel (The Straits Times, 2004) while the fuel oil

price was about US$ 218 per tonne (10X Group,

2005). To consider any such price shocks, a scenario is

studied by assuming that fuel-oil prices would be double

that of its current market price while the price of solar

PV modules and inverter would reduce to half of their

current price. In such a case, the cost of electricity would

be 16.5 cents/kWhe from the oil-fired steam turbine

Table 2

Improvement assessment of the solar PV system

Scenarios Energy

(MJt/kWhe)

EPBTa

(years)

CO2 emission

(g/kWhe)

Base case 2.91 5.87 217

A. Energy use for manufacturing of solar PV module reduced by 50% 1.72 3.48 129

B. Use of concrete supporting structure, i.e. aluminum use reduced to 10% 2.38 4.81 177

C. Efficiency of the solar PV system increase to 10.6% 2.21 4.47 165

A + B 1.20 2.42 89

B + C 1.81 3.66 135

A + C 1.31 2.65 98

A + B + C 0.91 1.84 68

a Reference to oil-fired steam turbine with a net efficiency of 33%. Hidden energy use and T&D loss are also accounted.

Fig. 5. Capital cost distribution of solar PV system.

Fig. 6. Life cycle cost distribution of electricity generation from

solar PV system.

4 For a fuel-oil price of 200 US$ per tonne, natural gas price is

about $ 5.34 per MMBTU as the natural gas price in Singapore

is pegged to fuel-oil price (The Business Times, 2004).



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plant at fuel-oil price of 400 US$/tonne, including the

T&D cost, and 36.15 cents/kWhe from the solar PV sys-

tem at solar PV module and inverter price of 3 US$/Wp

(see Fig. 7). It can be seen that the cost of electricityfrom the solar PV system would now be about two times

higher than that from the oil-fired steam plant.

6. Environmental uncertainties of solar PV system

From the life cycle energy use and GHG emission

perspectives, the solar PV system is a good choice for

power generation. However, studies have shown that

large-scale exploitation of solar PV could lead to other

types of undesirable environmental impacts in terms of

material availability and waste disposal (Phylipsen and

Alsema, 1995; Nieuwlaar et al., 1996; Fthenakis, 2000,

2004).

Silver requirement for manufacturing solar PV mod-

ules could contribute to the depletion of silver resources.

To meet 5% of the world electricity production from

solar PV modules, their production would require about

30% of the current silver production (Phylipsen and Al-

sema, 1995).

At the end of the life cycle, the solar PV system gener-

ates a substantial amount of waste (used module). The

study of Phylipsen and Alsema (1995) revealed that

weather-resistant encapsulation of the modules is a major

bottleneck for reuse or recycling of the silicon wafers.Due to encapsulations, the glass waste from modules

may contain too much plastics (EVA foil) to be accepted

by glass recyclers. As can be seen from this study, a 1 MW

solar PV plant could generate as much as 90 tonnes of

used solar PV modules, which may have to be landfilled.

Since the anticipated lifetime of the solar PV is about 25

years, waste generation will lag behind the installations of

solar PV modules. As we increase the rate of installation

of solar PV modules, large-scale disposal of solar PV

module may be another problem in the future.

The presence of small amounts of regulated materials

(e.g. Ag, Pb and Cd) (Fthenakis, 2000) in solar PV pan-

els may also cause undesirable environmental impacts

when they are landfilled.

So far, no proven technology has been developed for

large-scale disposal of solar PV modules. The studies ofFthenakis (2000, 2004) concluded that recycling is tech-

nologically and economically feasible, but not without

careful forethought. People in the solar PV industry

are claiming that there should not be any environmental

problem in disposing the solar PV panels because no

hazardous material is expected to be released by the pan-

els. However, we have seen that environmental problems

could come in any form such as global warming from

CO2, a non-hazardous gas. Therefore, the negative ef-

fects of solar PV technology must be studied to ensure

its environmental sustainability.

7. Conclusions

LCA and LCCA are performed for a solar PV system

in Singapore. From the perspectives of fossil energy use

and GHG emission, the solar PV system is a good choice

to address current energy-environmental issues. How-

ever, the cost of electricity generation from solar PV sys-

tems is not comparable with fossil fuel-based

technologies, particularly at the current market price.

If environmental externalities were to be accounted, then

solar PV systems would compete favourably with fossil

fuel based power generation. A reliable externality costis unfortunately not yet established. Nonetheless, cost

should not be the sole criterion in decision making be-

cause climate change may become a more serious risk.

Oil price and political uncertainties may be even more

critical for oil importing countries. Therefore, efforts

should be taken to explore all possible means to harness

available solar radiation.

Although there are constraints in space for installa-

tion of solar PV systems in Singapore, built-up areas

can be used effectively and annually about 1000 GWhecould be easily tapped. This would require an installed

capacity of about 1000 MWp and costs several billions

15

30

45

60

75

0% 1% 2% 3% 4% 5% 6% 7%

Interest on capital cost

Lifecyclecostofelectricity(/kWh)

5.83 US$/Wp (Current market

price) + BOS (1.68 US$/Wp)

6.5 US$/Wp + BOS

5 US$/Wp + BOS

4.5 US$/Wp + BOS

3 US$/Wp + BOS

2 US$/Wp + BOS

Fig. 7. Life cycle cost of electricity from solar PV system.



9/9

of dollars. Eventually, it would be less than 3% of the to-

tal electricity demand. Also, the disposal possibilities of

solar PV modules have to be studied in the Singapore

context due to the limited land availability for

landfilling.

Acknowledgements

The Building and Construction Authority, Singapore

provided the data for this work. The authors gratefully

acknowledge the extensive support of Mr. C.M. Bok

and Mr. K.S. Cheong and their comments on this paper.

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