**6. Energy and economic performances**

It is possible to evaluate the competitiveness of PV systems in terms of economic and energy performances. The prominent economic parameters are the global cost of the PV systems and the price of the solar energy generated while energy profitability is estimated in terms of the Energy Pay-Back Time [EPBT] as well as the Energy Return Factor [ERF].

Two realities affect the photovoltaic market: a) growth has been spectacular in just a few years and b) the price of the energy produced remains the most expensive (Aladjidi & Rolland, 2010). Thus, when a price per Wp is announced, it only reflects the price of the solar unit when it leaves the plant. The overall cost of the PV solar energy includes an entire series of parameters, such as the cost of the initial investment, the operating lifespan of the system, the energy performance during operation, the cost of maintenance and whether or not storage batteries are integrated (Goetzberger & Hoffman; PVResources, 2011).

The crucial parameter that will condition price fluctuations is certainly the maturity of the market, even more than the type of application for which the photovoltaic system is used. Thus, countries such as Germany and Spain are considered, as a result of their precocious commitment to the development of solar energy, the driving forces behind the growth of the PV market (Labouret & Villoz, 2009).

The cost of the initial investment, depending on the power desired, includes several elements, in particular the retail price of the unit and the various components of the system, the feasibility study, planning, and the cost of installing the equipment. The various components vary according to the type of system. Those connected to the network, in residential segments on rooftops or facades or in solar fields, require more assembly structures, a cabling system and eventually grounding work (EPIA/Greenpeace, 2011). On the other hand, in addition to storage batteries, autonomous systems include load controllers which, although they represent only 5% of the initial investment, are essential for protecting the systems against solar overloads and discharges (Labouret & Villoz, 2009).

In 2009, the price of PV installations varied from 3.5 to 5 Euros/Wp for 1 Kw of power with projections of 0.7-0.9 Euro/Wp in 2030 and even 0.56 Euro/Wp in 2050 (PVResources, 2011; EPIA/Greenpeace, 2011). The price of the photovoltaic unit is the most important factor in determining the cost of the initial investment. It is still rather high and is currently estimated at between 40% and 60% of the total cost, depending on the technology used, although it has decreased significantly over the past five years (EPIA/Greenpeace, 2011).

Since silicon dominates the PV market, the retail price of the units made using crystalline silicon reflects fluctuations in the price of the raw material, which is closely related with the production capacities of the industry. The spectacular overproduction of silicon noted in 2009, particularly as a result of the opening of an Asian PV market, although it destabilized the supply and demand through the multiplication of the number of independent producers, helped to remove the spectre of a silicon shortage (EPIA, 2011).

The other issue with respect to autonomous systems concerns the nature of the batteries, which are essentially lead-based. The lead battery has two disadvantages: the most particular concern is the potential effect on public health and safety and its impact on the environment, mainly resulting from the presence of lead, a toxic heavy metal. Concerns are not only to the manufacture and handling of this type of battery but also to end-of-life

It is possible to evaluate the competitiveness of PV systems in terms of economic and energy performances. The prominent economic parameters are the global cost of the PV systems and the price of the solar energy generated while energy profitability is estimated in terms

Two realities affect the photovoltaic market: a) growth has been spectacular in just a few years and b) the price of the energy produced remains the most expensive (Aladjidi & Rolland, 2010). Thus, when a price per Wp is announced, it only reflects the price of the solar unit when it leaves the plant. The overall cost of the PV solar energy includes an entire series of parameters, such as the cost of the initial investment, the operating lifespan of the system, the energy performance during operation, the cost of maintenance and whether or

The crucial parameter that will condition price fluctuations is certainly the maturity of the market, even more than the type of application for which the photovoltaic system is used. Thus, countries such as Germany and Spain are considered, as a result of their precocious commitment to the development of solar energy, the driving forces behind the growth of the

The cost of the initial investment, depending on the power desired, includes several elements, in particular the retail price of the unit and the various components of the system, the feasibility study, planning, and the cost of installing the equipment. The various components vary according to the type of system. Those connected to the network, in residential segments on rooftops or facades or in solar fields, require more assembly structures, a cabling system and eventually grounding work (EPIA/Greenpeace, 2011). On the other hand, in addition to storage batteries, autonomous systems include load controllers which, although they represent only 5% of the initial investment, are essential for protecting the systems against solar overloads and discharges (Labouret &

In 2009, the price of PV installations varied from 3.5 to 5 Euros/Wp for 1 Kw of power with projections of 0.7-0.9 Euro/Wp in 2030 and even 0.56 Euro/Wp in 2050 (PVResources, 2011; EPIA/Greenpeace, 2011). The price of the photovoltaic unit is the most important factor in determining the cost of the initial investment. It is still rather high and is currently estimated at between 40% and 60% of the total cost, depending on the technology used, although it has

Since silicon dominates the PV market, the retail price of the units made using crystalline silicon reflects fluctuations in the price of the raw material, which is closely related with the production capacities of the industry. The spectacular overproduction of silicon noted in 2009, particularly as a result of the opening of an Asian PV market, although it destabilized the supply and demand through the multiplication of the number of independent

decreased significantly over the past five years (EPIA/Greenpeace, 2011).

producers, helped to remove the spectre of a silicon shortage (EPIA, 2011).

of the Energy Pay-Back Time [EPBT] as well as the Energy Return Factor [ERF].

not storage batteries are integrated (Goetzberger & Hoffman; PVResources, 2011).

recycling (Vest, 2002).

**6. Energy and economic performances** 

PV market (Labouret & Villoz, 2009).

Villoz, 2009).

In addition to readjusting the silicon market as a condition for stability requiring the consolidation of firms, the real issue with respect to reducing the price of the units involves improving the manufacturing process through automation. Thus, major efforts should be made to improve refining capacity, reduce the thickness of silicon wafers and increase conversion performances through an equitable manufacturing process that respects specific standards (Aladjidi & Rolland, 2010; EPIA/Greenpeace, 2011).

Although there are still good days ahead for silicon, the development of various emerging technologies in the field of photovoltaics would necessarily have a most beneficial effect since they would either use less silicon, as in the case of amorphous or micro-crystalline cells, or they would use innovative materials other than silicon (Aladjidi & Rolland, 2010).

The lifespan of the PV systems is a key parameter not only for the assessment of the overall cost of the systems but also for estimating the EPBT and ERF. Most of the manufacturers of PV units provide performance guarantees, namely a life span between 20 and 25 years at 80% of the minimum nominal power for both crystalline and cadmium telluride units, while stating that this average would be a minimum estimate and not a definitive value since it would be estimated at 40 years in 2020 (Labouret & Villoz, 2009; EPIA/Greenpeace, 2011).

The improvement in lifespan is both technological and technical in nature since it is closely related to the stability of the PV systems in use elsewhere, which are negatively impacted by a deterioration process that affects both the solar units, despite the encapsulation of the cells, and the support frame. This degradation can result from the aging of the semiconductors, the delamination or loss of adhesiveness between the solar cells and from the intrusion of humidity. The fragility of the systems has a major impact on the energy performance during operation. However, only few studies were done on the estimation of losses, while a decrease in performance of 1%-2% per year was observed for some systems (Goetzberger & Hoffman, 2005).

The cost of maintenance, including the ongoing control of the performance and the appearance of the systems as well as their cleaning, remains low and is estimated to be between 0.01 and 0.1 Euro/kWh (PVResources, 2011). However, integrating storage batteries in the autonomous systems, which are characterized by a decrease in lifespan of a factor of 2 for every 10 degrees Celsius as a result of corrosion, leads to a long-term increase in the cost of the investment as seen earlier (Labouret & Villoz, 2009).

The average price of the solar electricity generated depends, among other things, on the initial installation costs and the rate of sunshine and is estimated at 0.22 Euro/kWh in Europe and remains, despite a significant decrease of 40% between 2007 and 2009, less competitive than the electricity generated using fossil fuels, which is evaluated between 0.09 and 0.27 Euro/kWh (EPIA/Greenpeace, 2011). However, there is no shortage of programs intended to make PV systems profitable, such as investment contributions (subsidy, green loan), tax benefits (reduction, exoneration) and direct pricing support, including the compensatory redemption rate systems in place in several European Union countries, particularly Germany and Italy (Goetzberger & Hoffman, 2005).

Germany was the first country to implement a law giving priority to renewable energy and has been a powerful driving force behind the development of PV programs. This law, and others which have been based on it, establishes the right to inject solar energy into the public network and to be reimbursed per PV kWh (EPIA/GREENPEACE, 2011; PVResources, 2011).

Photovoltaic Conversion: Outlook at the Crossroads

and liquid waste.

PVPS, 2011).

2011; Held & Ilg, 2011).

Between Technological Challenges and Eco-Strategic Issues 323

As a result of the accelerated growth of the PV industry, a rigorous assessment of the environmental impacts of the systems has become necessary, conducted through a life cycle assessment (LCA) integrating all of the manufacturing, operating, collection and waste recycles. The LCA is an orderly process that analyzes the input/output impact of the PV industry from the "cradle to grave", with the inputs referring to the materials and energy consumed and the outputs illustrated by greenhouse gas (GHG) type emissions and solid

A form of environmental management that is as exhaustive as possible, the LCA is a series of tools and techniques for which the ultimate objective, beyond the descriptive and quantitative aspect of the environmental profile, is to reinforce the sustained effort to limit the environmental impacts in a context of sustainable development (Fthenakis et al., 2005a; IEA-PVPS, 2011). The key factor that will determine the pertinence and the credibility of the LCA will be the voluntary and transparent cooperation of the manufacturers with respect to the accurate and full disclosure of the various inputs/outputs (Fthenakis et al., 2005a;

In addition to the energy considerations previously illustrated by the calculation of the EPBT and the ERF, the parameter most frequently estimated for the LCA assessment is the ecological footprint describing and quantifying the entire greenhouse gases (GHG) released during the lifespan of the PV system and expressed in carbon dioxide equivalents per kWh. The environmental gain expected by the reduction of GHG related to the operation of PV electricity has also to be taking into account. These two assessments are always determined in comparison with the emissions attributed to fossil energies (Fthenakis et al., 2005a; IEA-

The estimate of the GHG attributed to PV systems is an increasingly complex exercise since it includes criteria that are as diversified as the technology used, the choice of manufacturing processes and the type of energies consumed, the techniques for assembling the cells and units, the power generated, the transportation of raw materials and the finished product, the components required for the installation of the units (Balance Of System/BOS) as well as the recycling processes. The BOS will, in turn, depend on the applications, the dimensions, the orientations and, above all, the location selected (Krauter

A major distinction is acknowledged between indirect emissions, which concern the overall energy, electricity included, needed to manufacture the units, and the direct emissions, which concern all of the chemical compounds, raw materials included, that are involved in the manufacturing process and are a potential source of GHG (Reich et al., 2011). It is essential to point out that the GHG emission estimates for PV systems are not absolute since they are subject to a certain number of constraints, particularly the quality of the information provided by the manufacturers involved throughout the life cycle. Thus, the estimates are subject to future revisions as are the EPBT and ERF calculations (Reich et al.,

With respect to the direct emissions of the silicon industry, three critical phases are identified: the development of metallurgical-grade silicon from silica, its transformation into solar-grade silicon and the development of a structure and framework in the form of panels. While the production of metallurgical-grade silicon requires the consumption of roughly 14 kWh per kg of metallurgical-grade silicon whole releasing 3 tons of CO2 equivalents for one

**7. Life cycle of photovoltaic systems and ecological footprint** 

Stoppato, 2008; IEA-PVPS, 2009; Ecoinvent , 2010; IEA-PVPS, 2011).

& Rüther, 2004; Stoppato, 2008; Fthenakis & Kim, 2011; Reich et al., 2011).

Photovoltaics consume necessarily energy throughout a system's life cycle, i.e. during the manufacturing of modules, their installation and, at the end of their useful life, disassembly and recycling. The energy balance is defined by two common parameters: the EPBT, meaning the time required for PV energy to repay its energy debt, and the ERF or how many times the consumed energy is reproduced. These two parameters are determined by the rate off sunshine, the purpose and design of the PV system, and the type of technology (International Energy Agency-Photovoltaic Power Systems Program [IEA-PVPS], 2006; EPIA/Greenpeace, 2011).

The energy balance is closely related to the lifespan of the systems. A 2006 study gives an EPBT of between 1.6 and 3.3 years for systems installed on roofs and 2.7 to 4.7 years for those integrated into facades. The ERF, estimated for a business life of 30 years, is between 8 and 18 for roofs and from 5.4 to 10 for facades (IEA-PVPS, 2006). Data collected in 2009 for systems integrated into roofs in southern Europe indicate an EPBT of nearly 1.75 years for systems that use silicon cells, except for silicon ribbon, which is estimated at just over one year. Thin film technologies remain effective with nearly 0.7 years for cadmium telluride systems (EPIA/Greenpeace, 2011), which was adjusted to 0.7 to 1.1 years by the Held team from Germany (Held & Ilg, 2011).

Preliminary results related to commercial applications for solar concentrators present an EPBT of 0.8 to 1.9 years (Wild-Scholten et al., 2010). It appears that the silicon wafer industry is highly energy intensive and that the development of thin-film technologies, which require few materials, would be more compatible with an energy gain reducing the EPBT, maximizing the ERF and consequently optimizing the energy efficiency (Wild-Scholten et al., 2010; EPIA/Greenpeace, 2011).

However, a low EPBT does not always equate low energy efficiency and this finding makes perfect sense when applied to autonomous systems, which are of great use in developing countries. These systems are somewhat not considered in these calculations since few studies reinforce this reality, except one with an EPBT of 3.5 to 6 years due to the presence of storage batteries that must be regularly renewed and excess energy during periods of strong sunlight (Kaldellis et al., 2010).

These energy assessment calculations include the end-of-life recycling of systems. Although the first large-scale PV applications were installed in the 1990s, increasing growth of the market will require that more systems be disassembled and recycled. Once disassembled, in terms of waste to be treated, PV modules represent about 2,300 t in 2007, over 7,500 t in 2011 and a forecast of 132,000 t in 2030 considering average annual growth of 17%. Silicon modules currently represent over 80% of this waste. But if trends in thin film and emerging technologies continue, by 2030 they could account for over 65% of waste generated (Sander et al., 2007).

The era of waste collection and recycling PVs is still in its infancy despite voluntary measures in the PV industry (PVCycle, 2011) and the ongoing search for more efficient recycling techniques, both energy and economic, for all types of modules (Radziemskai et al., 2010). The recent integration of PV in the Waste Electrical and Electronic Equipment (WEEE) directive (Council of European Commission, 2011a) is only a first step and a strong legislative framework underpinned by sustained efforts is required in order to structure PV waste management, generalize the most competitive recycling processes for all system components, including batteries, and make them applicable to the extent of PV installations worldwide (PVCycle, 2011).

Photovoltaics consume necessarily energy throughout a system's life cycle, i.e. during the manufacturing of modules, their installation and, at the end of their useful life, disassembly and recycling. The energy balance is defined by two common parameters: the EPBT, meaning the time required for PV energy to repay its energy debt, and the ERF or how many times the consumed energy is reproduced. These two parameters are determined by the rate off sunshine, the purpose and design of the PV system, and the type of technology (International Energy Agency-Photovoltaic Power Systems Program [IEA-PVPS], 2006;

The energy balance is closely related to the lifespan of the systems. A 2006 study gives an EPBT of between 1.6 and 3.3 years for systems installed on roofs and 2.7 to 4.7 years for those integrated into facades. The ERF, estimated for a business life of 30 years, is between 8 and 18 for roofs and from 5.4 to 10 for facades (IEA-PVPS, 2006). Data collected in 2009 for systems integrated into roofs in southern Europe indicate an EPBT of nearly 1.75 years for systems that use silicon cells, except for silicon ribbon, which is estimated at just over one year. Thin film technologies remain effective with nearly 0.7 years for cadmium telluride systems (EPIA/Greenpeace, 2011), which was adjusted to 0.7 to 1.1 years by the Held team

Preliminary results related to commercial applications for solar concentrators present an EPBT of 0.8 to 1.9 years (Wild-Scholten et al., 2010). It appears that the silicon wafer industry is highly energy intensive and that the development of thin-film technologies, which require few materials, would be more compatible with an energy gain reducing the EPBT, maximizing the ERF and consequently optimizing the energy efficiency (Wild-Scholten et

However, a low EPBT does not always equate low energy efficiency and this finding makes perfect sense when applied to autonomous systems, which are of great use in developing countries. These systems are somewhat not considered in these calculations since few studies reinforce this reality, except one with an EPBT of 3.5 to 6 years due to the presence of storage batteries that must be regularly renewed and excess energy during periods of strong

These energy assessment calculations include the end-of-life recycling of systems. Although the first large-scale PV applications were installed in the 1990s, increasing growth of the market will require that more systems be disassembled and recycled. Once disassembled, in terms of waste to be treated, PV modules represent about 2,300 t in 2007, over 7,500 t in 2011 and a forecast of 132,000 t in 2030 considering average annual growth of 17%. Silicon modules currently represent over 80% of this waste. But if trends in thin film and emerging technologies continue, by 2030 they could account for over 65% of waste generated (Sander

The era of waste collection and recycling PVs is still in its infancy despite voluntary measures in the PV industry (PVCycle, 2011) and the ongoing search for more efficient recycling techniques, both energy and economic, for all types of modules (Radziemskai et al., 2010). The recent integration of PV in the Waste Electrical and Electronic Equipment (WEEE) directive (Council of European Commission, 2011a) is only a first step and a strong legislative framework underpinned by sustained efforts is required in order to structure PV waste management, generalize the most competitive recycling processes for all system components, including batteries, and make them applicable to the extent of PV installations

EPIA/Greenpeace, 2011).

from Germany (Held & Ilg, 2011).

al., 2010; EPIA/Greenpeace, 2011).

sunlight (Kaldellis et al., 2010).

worldwide (PVCycle, 2011).

et al., 2007).
