• Why thin-film PV?

Why thin-film PV?

Life cycle analysis (LCA) provides an invaluable decision support tool for policymakers as a framework for assessing the environmental impacts of a product or process throughout its life cycle; from raw material sourcing to manufacturing, operations and end-of-life disposal or recycling.

Thin-film PV technologies use up to 99% less semiconductor material to convert sunlight into electricity, resulting in lower production costs, higher conversion efficiencies and a smaller environmental footprint.

 

 

Source: MIT, The Future of Solar Energy, 2015.

 

 

In addition, thin-film PV’s minimal resource requirements result in lower manufacturing costs. Innovation in thin-film comes in the form of the unique processes manufacturers use to generate PV modules, with some capable of producing a module in just 3.5 hours. To do so manufacturers avail of  highly-automated processes that have more in common with flat-screen TVs than they do with the production of a conventional crystalline-silicon panel. This also comes in the form of technology-led operations and maintenance processes that set the industry benchmark for optimising utility-scale PV plants in some cases, and other integrated and innovative solutions such as ink-jet solar cells, and building integrated PV modules in others.

PV module cost curve

Source: Bloomberg New Energy Finance 2012 and Green Tech Media 2015.

 

By applying lessons learned from the flat panel display sector, the thin-film PV industry has the potential to further achieve manufacturing cost reductions by using bigger manufacturing equipment to make larger units at a lower cost.

The most interesting attribute of these cells is their high conversion efficiencies, which can surpass 40%. These high efficiencies are obtained, however, at the cost of complex fabrication processes and cell designs and the use of rare elements.

Conventional crystalline silicon technologies are approaching their practical efficiency limit while thin-film technologies have room to grow and innovate. Thin-film PV technologies have the fastest innovation rate in the industry as can be seen in the graph below. The next logical step in technology evolution is fast approaching, with thin-film enhanced silicon technologies being commercialised in the form of tandem cells. Thin-film PV technologies in tandem applications will enable us to overcome conventional efficiency limitations and further improve performance, while also decreasing the cost of photovoltaic electricity generation. The most impressive example of this technology evolution can be seen in the Perovskite technology.

Source: US National Renewable Energy Laboratory: Figure 1 Best Research-Cell Efficiencies Thin Film Technologies

In addition to having the highest theoretical efficiencies among single-junction solar cells, thin-film PV technologies have a proven real-world performance advantage over crystalline silicon modules. Beyond standard testing conditions of 25°C, all PV semiconductor technologies begin to incur increasing performance losses as temperatures rise. However, thin-film technologies have less temperature-related losses due to their low temperature coefficient. As a result, thin-film PV modules generate more energy in hotter field environments.

 

Thin-film PV modules are also less sensitive to shading due to their monolithic design. When shading occurs, typical crystalline silicon technologies turn off disproportionately large portions of the module to protect it from damage. In a thin-film module, only the shaded portion is impacted while the rest of the module will continue to produce power. By producing more usable energy per nameplate watt, thin-film PV modules deliver lower levelised costs of electricity in most climatic conditions.

 

Energy Return on Energy Invested (EROI) is a metric used to quantify the amount of energy produced by an energy source system compared to the amount of energy needed to build and operate the system. EROI is a unitless ratio of the energy produced for society to the energy required to make that energy. An energy source with an EROI of less than 1:1 is not considered viable. Thin-film PV technologies provide the greatest return on energy invested as they require less energy during manufacturing.

 

Life Cycle GHG Emissions of Different Energy Technologies

Source: UNEP (2016) Green Energy Choices: The benefits, risks, and trade-offs of low-carbon technologies for electricity production. Report of the International Resource Panel. E.G.Hertwich, J. Aloisi de Larderel, A. Arvesen, P. Bayer, J. Bergesen, E. Bouman, T. Gibon, G. Heath, C. Peña, P. Purohit, A. Ramirez, S. Suh.

EROI

Source: K. P. Bhandari et al., Energy Payback Time and Energy Return On Energy Invested of Solar Photovoltaic Systems, Renewable and Sustainable Energy Reviews 47, 2015.

PV technology life cycle assessments show that electricity generated from PV has substantially lower greenhouse gas emissions compared to fossil-fuel based electricity generation technologies and that thin-film CdTe and CIGS modules have a lower environmental impact than crystalline silicon technologies in terms of greenhouse gas emissions, air pollutants, ecotoxicity and energy use.

Thin-film PV technologies are particularly lightweight and flexible which allows for their integration into specific applications such as vehicle integrated PV. This has been embraced by companies such as the bus company, FlixBus that in 2020 announced that it installed thin-film PV panels on the roofs of buses to charge the battery. By relieving the alternator of the need to charge the battery using fuel, it is estimated that the thin-film panels save 1.7 litres of diesel per 100km. As the buses travel an average of 600km a day, this represents a daily fuel saving of around 10 litres!

 

Alongside integration into vehicles, the flexibility and great aesthetic appeal of thin-film PV technologies enables building integrated PV (BIPV). This can allow for the use of the full surface area of buildings  in the production of renewable energy, rather than just using the roof-mounted solar PV.

Manz AG Gebäudeintegrierte Photovoltaik3

©Manz: Building-Integrated CIGS PV Application

Thin-film PV technologies contribute to the circular economy by providing a secondary use for mining by-products that would otherwise be disposed of. Cadmium, gallium, germanium, indium, selenium, and tellurium are sourced as by-products from the production of aluminium, zinc, lead, copper and coal. At the end of their 25+ years, useful lifetime, thin-film PV modules can be recycled to recover glass and semiconductor metals for reuse in new thin-film modules and glass products. With over 500 GW of PV installed worldwide and a probable trajectory to multi TW deployment, proven high-value PV module recycling solutions are important for all solar technologies. In addition to PV Cycle, there are several innovative high-value thin-film PV recycling initiatives operational worldwide, that are helping to close the loop.

FS recycling process

First Solar’s high-value recycling process currently recovers over 90% of the semiconductor material for reuse in new CdTe PV modules and 90% of the glass for use in new glass products. First Solar recycling facilities are operational in the U.S., Germany, and Malaysia.

According to the International Energy Agency, thin-film cadmium telluride (CdTe) modules have been recycled for over 10 years, reaching over 4,500 tonnes in 2017.

Image17

Source: Keiichi Komoto, Workshop on PV Life Cycle Management & Recycling, Amsterdam, the Netherlands, 23 September 2014.

Discover the projects that are implementing circular economy.

Thin-film PV technologies provide the industry’s most ecological solutions due to their low material consumption, efficient manufacturing processes and fast energy payback times. By using less electricity during production, thin-film PV technologies generate the amount of energy required to produce them up to 3.5 times faster than crystalline silicon PV technologies.

 

Policymakers have begun to incorporate PV LCA results in energy tendering systems. In order to award volumes to technologies with the lowest environmental impact, the French Environment and Energy Management Agency (ADEME) included carbon footprint assessment as a component in recent French PV tenders. As a result, the carbon footprint advantage of thin-film PV technologies is increasingly translating into increased business opportunities. Additionally, in the EU an EU Ecolabel tool is currently being considered to help professionals and consumers assess PV technologies based on reliability as well as technical and environmental performance. Internationally, the American National Standard Institute (ANSI), and the Green Electronics Council (GEC) are developing sustainability leadership standards, including for PV and inverter technology. These aim to establish product sustainability performance criteria and corporate performance metrics that exemplify sustainability leadership in the market. ANSI has developed the NSF 457 certification, while GEC is finalising its EPEAT performance tiers (bronze to gold) for PV and inverters.

Energy security is a complex issue, which is only likely to worsen if no action is taken. Thin-film PV technologies can be part of the solution by generating sustainable and affordable energy across the globe.

 

• 1 in 6 people do not have access to electricity and emerging economies face growing energy needs

• IEA projects electricity demand will rise 70% by 2035 with India and China accounting for half

• PV contributes to a more resilient grid and minimizes the risk of fuel price volatility by delivering reliable and cost competitive electricity

• PV technology decouples electricity generation from fuel supply chains, and due to the versatility of thin-film PV this advantage can be applied almost everywhere

The EU’s proposal for a Climate Law commits it to achieving climate neutrality by 2050. Thin-film PV technologies can contribute to this change by generating clean electricity, due to their high efficiency rates and low energy requirements for production – translating directly into a very high carbon displacement efficiency (insert hyperlink to watttime blog post).

 

• The power sector is the world’s largest consumer of fossil-fuels and accounts for over 40% of energy-related CO2 emissions
• PV generates clean electricity for 25+ years with no carbon emissions or other air pollutants

According to the World Wildlife Fund, water covers 70% of the planet but only 3% of that is fresh water, much of which is stored in glaciers or unavailable for use. It is estimated that 1.1 billion people lack access to water and 2.7 billion find water scarce for at least one month of the year. The current situation could continue to worsen, by 2025 it is estimated that 2/3 of the global population may face water shortages.

 

• Global energy generation accounted for approximately 15% of the world’s total water withdrawals in 2010 or 583 billion cubic meters per year

• In the U.S. and Europe, thermal power plants account for more than 40% of total water withdrawals

• PV uses up to 300 times less water than conventional energy by directly converting sunlight to electricity without the use of water

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