CEA-INES: ‘It is necessary and urgent to redefine system thinking about materials use in the PV industry’

In 2016, CEA-INES held the very first Eco-PV workshop in Chambery, France. The EU commission, industrial stakeholders, investors and research institutes were invited to discuss topics of solar sustainability, like eco-design, lifecycle assessment and recycling in the PV industry.

The fourth workshop was set to be held this March 10-11 in Lyon. Due to the Coronavirus pandemic, which continues to sweep the world, it has been reworked into a virtual format, and is now scheduled to be held between March 9-11, 2021. Claire Agraffeil, project manager at CEA-INES speaks to pv magazine about the most pressing issues facing solar sustainability, what the institute hopes to achieve via the workshop, and the work it is currently focusing on.

pv magazine: Which sustainability issues do you see as the most pressing for the PV industry at large?

Claire Agraffeil: Industrial PV manufacturers are clearly aware of the opportunities related to the growing potential of PV energy in the next decades and of the central role they will play. They also understand the challenge of the new era coming that implies and requires renewable energies to be exemplary in contributing efficiently to the carbon neutral paradigm.

Already, strong efforts have been made to assess and lower environmental impacts in the manufacturing stages. However, there is still room for improvement in terms of environmental performance, and manufacturers are willing to invest in and develop more sustainable solutions. Some technologies, such as heterojunction, offer improved efficiency and fewer processing steps, while for all technologies, improvements are still expected regarding chemicals and water use or electricity consumption during the production phase. Steps forward are also needed to manage manufacturing waste – wafers, cells, glass sheets, for example – that generally end up being landfilled.

At the product level, investigations on materials innovation are also key at this stage as primary resources are not endlessly accessible. Innovations include the development of new materials/structures replacing hazardous or scarce materials, the reduction of materials consumption (silver (Ag) and indium (In), for instance) or the use of recycled secondary raw materials possibly combined with virgin materials.

At the system level, inverters, mounting structures and storage systems should be also included in the process loop of material use in the PV industry; while at the installation stage, it is very important to re-think the practices looking at the huge amount of packaging – wood, steel, plastic, cardboard, etc. – required for the installation of power plants.

Ultimately, waste management at end-of-life will be crucial in the coming decades, in order to redesign the PV industry within circular models.

How important is it for competing manufacturers to work together to solve such issues?

Looking at the big picture, the most important issue today is to ensure the safe and sustainable deployment of solar energy with common incentives to contribute to a green recovery. For this, it is fundamental to secure the market and generate fair solutions and competitiveness while promoting the most sustainable routes.

A collective effort though transparent processes from manufacturers are certainly needed to push forward innovation and orient the market toward sound, green solutions facilitating electricity access over the world. Doable strategies to minimize the levelized cost of electricity (LCOE) and favoring quality PV products mitigating environmental impacts should be supported by the PV industry at large and become the future market trends.

Raw material extraction is a critical sustainability issue – and this will grow if we look at the volumes needed for the required energy transition to renewables. Is it time to think of a new model when it comes to material use?

Yes, definitely. Critical, scarce and valuable materials are embodied in PV devices for 25-30 years, which might have been acceptable until now. Looking at the resources needed in the future, highlighted by Pierre Verlinden in pv magazine’s Sustainability Roundtable this June, these could represent a significant share of the worldwide materials production. The most worrying is the amount of silver required for 1TW, which is equivalent to 94% of the current worldwide production. It is necessary and urgent to redefine entirely our system thinking about materials use in the PV industry.

In this regard, efficient recovery and recycling are the cornerstones when it comes to sustainability ambition in the PV value chain. Although substitution can offer some solutions, recycling remains the best available approach to secure the supply of raw materials and make it durable. Silicon (Si), In and Gallium (Ga) are listed as critical materials by the European Commission, and Lithium (Li) has been added in the updated 2020 version. The End-of-Life Recycling Input Rate (EOL-RIR) assessed in the report on Critical Raw Materials and the Circular Economy 2018 for materials such as Si, In or Ga count for 0% in Europe, which shows the current situation and the degree of resource “efficiency”. Not to mention that the extraction of primary raw materials is one of the costliest steps in terms of environmental impacts in the PV value chain and at large in the industry.

Two issues could be outlined in the PV waste management and that should be overcome at this stage. The first is the longer lifespan of PV modules compared to other electronic and electrical equipment (EEEs). “We’ve got time to handle it” may have been true in the past decades as the volume of PV waste remained quite low; but now it is time to move forward. In 2019, PV Cycle France collected almost 5,000 tons of waste. The second issue is that there have been lots of efforts in the past to implement regulatory frameworks, which is great. However, if we look at the European directive (2012/19/EU) that requires 80% of recycling and 85% of recovery, these ratios can be easily reached by recycling only the junction boxes, frames and glass front sheets. It does not encourage or boost recycling practices to recover the valuable and critical materials embodied in EOL PV modules.

Circular solar manufacturing practices and business models are gaining traction. What are your thoughts on this?

The “circular economy” is a concept born in the early 1970s. Since then, many investigations in diverse fields have been undertaken, and the circular model has become a commonly used expression. However, it is not that easy to move forward from paper and modelling to the business reality. This requires a rethink and redesign of the models to be turned in new logics and approaches, which is a long-term job.

This is why CEA has implemented a specific research area dedicated to the circular economy. Regarding the solar industry, CEA has been a pioneer on the topic as coordinator of the EU Horizon 2020 project CABRISS (implementation of a circular economy based on recycled, reused and recovered indium, silicon and silver materials for PV and other applications), which enabled us to map out the first guidance. The project has monitored progress looking at the big picture over the whole PV value chain to identify the hotspots related to sustainability issues and to implement circular models.

CEA is also involved in the CIRCUSOL (Circular business models for the solar power industry) project, which is addressing circular business opportunities in the PV value chain, particularly in re-use and repair scenarios, among other topics. In a more general way, implementing a circular economy over the PV value chain implies that we bring together various stakeholders from manufacturing to waste management, as well as the end-users of secondary raw materials.

To achieve visibility and help collectively coordinate strong models, it is essential to bridge the different sectors, particularly the PV industry to waste collectors and recyclers. As there are huge gaps between them in terms of technological and business approaches, we need to create common incentives to shift to circular models together. This is also very important to open the prospects and links to other inter-related or inter-disciplinary value chains when it comes to re-injecting back the secondary raw materials. Indeed, circular business logic considers commercial viability carefully as a priority trade-off to implementing bankable solutions. It is via this vision that CEA is currently working on setting up future projects on circular strategies.

Furthermore, policies and regulatory frameworks will be necessary to support and launch a set of actions that is coherent between the different initiatives and legislations, such as the Waste Electrical and Electronic Equipment (WEEE) and Ecodesign/Energy Label directives.

CEA-INES will hold a workshop in March 2021 titled Photovoltaics: Towards a sustainable industry. What do you hope to achieve here?

The fourth edition of the ECO-PV workshop aims to cover the topics that foster sustainable PV development. It intends to bring together all the communities involved, including manufacturers, recyclers, policymakers and experts from organizations, like the JRC European Commission, IEA-PVPS, and research institutes to exchange views, and trade information and knowledge to develop a collective vision for the future of solar energy. Through eight sessions over two and a half days, the workshop will address the following topics: PV sustainability and the circular economy as a global topic, economic and environmental analysis, quality and reliability issues, eco-design and recycling alternatives.

We believe there are urgent matters to be considered when it comes to redefining system thinking throughout the PV value chain for the future deployment of solar energy. The motivations of such meeting are numerous:

1. To inform and share information on the current issues and options at every level (manufacturing, installation, maintenance, decommissioning and regulations);
2. To discuss and identify solutions to develop and drive the critical improvements that are needed to redesign PV energy as a global and sustainable industry; and
3. To provide an overview in the field and broaden standpoints and insights beyond with actors from different horizons.

From the program, recycling is a special focus for CEA. What are the current and future challenges of PV recycling from your perspective?

Considering there are currently no efficient recycling solutions, the situation is quite alarming. Legislative initiatives in Europe (Directive 2012/19/EU), the United States (Washington state) and starting elsewhere (Japan, Korea, Australia, India) will strongly support the treatment of EOL devices and promote the incentives to develop new solutions as well. The Extended-Producer-Responsibility (EPR) is also a good drive to finance and nurture progress in the field, requiring all producers supplying PV panels to the EU market to contribute to the cost of collecting and recycling of EOL panels to avoid burden environmental issues (like landfill).

However, until now PV waste management has been mainly handled in WEEE or metal/glass recycling facilities in Europe. The most common approach remains the shredding/crushing process and further sorting. This generally leads to downcycling assuming – due to the lack of data reported – the very low quality of raw materials produced and partially landfilled. Indeed, the few outcomes in terms of materials recovery is usually not satisfactory.

A PV module contains both useful conventional resources (aluminum, copper, glass) and critical/valuable materials (Si, Ag, In, Ga, etc.) as well as hazardous materials (lead, cadmium, selenium). The polymer fractions are usually recovered as energy fuel at best or landfilled at worst, while the external components, such as the frame and the junction box are easily disassembled and recycled. For sure, the critical and valuable materials count only for a very little share in percentage by mass. However, it is more than significant if we look at the million tons of PV waste. If we do not move forward to more efficient solutions, we risk dramatic outcomes, such as toxic material dispersion and irreversible loss of valuable and scarce materials.

To take up the challenges of recovering higher quality and purity materials, there are two issues that need to be addressed. The first is to separate selectively the PV sheet (glass frontsheet/solar cells/backsheet) to avoid mixing materials and, so contamination. The second is to extract the metals from the solar cells to enable the recovery of silicon, silver, copper and other metals.

Many ideas and smart solutions have popped up, like mechanical cutting, and thermal or chemical separation, and further metal extraction or wafer recovery. However, the challenge is to fit in a reliable and positive business case to attract further investments. And providing solutions that mitigate environmental impacts. The task is quite challenging.

As an R&D organization, our role here is to be the driving force creating new ecosystems of innovation working together with the industrial actors to find out and implement robust solutions. Indeed, to provide economic incentives and develop the business, we need to investigate new technological solutions for efficient and sustainable PV recycling routes that can enter the market. We are well aware that the challenge is ambitious, and we are ready to tackle it.

CEA-INES primarily focuses on c-Si research. What are your thoughts on the use of toxic materials like lead?

The International Technology Roadmap for Photovoltaic 2020 has mapped out almost 50% lead-free cell interconnection by 2030. This is meant to represent the market share of the strategies using either lead-free soldering (~30%) or Electric Conductive Adhesive (~20%). CEA has been using lead-free soldering since 2014 and this has become a common practice, as we mostly use SnAgCu or SnAg-based ribbons to operate cell interconnections.

For Heterojunction Technology (HJT), which requires low temperature processing, several lead-free alternatives, such as SmartWire Connection Technology (SWCT) or Electric Conductive Adhesive (ECA) have been developed. While the ECA interconnection strategy offers characteristics with low thermo-mechanical stress using lead-free textured ribbons, the related cost remains a disadvantage. Indeed, the cost driven by the composition (Ag-based) and the efficiency (about 10mg ECA/BB) could be reduced by lowering the ECA amount at a similar performance level.

CEA is currently working on the topic and aims to lower the required ECA mass/BB (busbar) by at least 50%. This would represent a major improvement and develop new opportunities and perspectives also for other Si-based technologies. Indeed, ECA interconnection could prevent from using lead-containing soldering, mitigate the thermo-mechanical stress and lower Ag consumption per BB. In a more global way, CEA strives in considering any improvement or step forward related to efficient material use and preventing from hazardous materials at most.

Claire Agraffeil holds a PhD in materials Science and process engineering dedicated to microelectronic applications. She has worked in this field at CEA as researcher and project manager for seven years in process development and materials characterization. She joined the Solar Technology department (CEA-INES) in 2017 as project manager in charge of the topics related to waste management and eco-design of PV system. She is involved in several international working groups such as the International Energy Agency – Photovoltaic Power Systems Programme task12 and European Technology & Innovation Platform WG5-ECO  to develop and support solutions for PV sustainability.