Product stewardship for solar photovoltaic panels

The uptake of solar photovoltaic (PV) panels for the generation of clean energy has almost exponentially increased over the past 10 years and can be expected to further exponentially increase until 2030. Organisations like the International Renewable Energy Agency have clearly outlined the need and benefits of robust end-of-life (EoL) management legislations, such as a product stewardship scheme or extended producer responsibility, to cope with the significant expected waste volume arising from solar PV panels during the next 30 years or so. However, effective EoL management legislation is still not existing in many countries despite having significant solar PV capacity installed. This article explores a possible strategy for a product stewardship legislation for solar PV panels including options for necessary levies to support an emerging recycling industry for solar panels. Given that currently almost 3 billion solar PV panels are installed worldwide, considerations are also given for a legislation which supports and encourages a second hand economy for solar PV panels.


Introduction
Climate change is a shared global challenge with energy being the heart of the problem and the solution.Oil, coal and natural gas make up 84% of the world's primary energy supply and continue to be the dominant cause of climate change (Dale 2021).The energy supply sector accounted for around 34% (20 GtCO 2 -eq) of the total net anthropogenic greenhouse gas (GHG) emissions in 2019 (Shukla et al 2022).In order to prevent a dangerous rise in global temperatures, the Intergovernmental Panel on Climate Change analysis explicitly stated that net-zero emissions must be achieved over the next several decades (IPCC 2018).The net-zero challenge calls for a paradigm shift in critical areas such as increasing energy efficiency and making low-carbon electricity the primary source.To accomplish this, the dependence on fossil fuels needs to be stopped and investment in clean, accessible, affordable, sustainable, and reliable energy sources needs to speed up (United Nations 2022b).Renewable energy, such as that provided by the sun, wind, and water, can aid in addressing not only climate change but also air pollution and health concerns.In line with the United Nations net zero goals, countries have started transitioning towards renewable energy (United Nations 2022a).With 173 000 TW of solar energy reaching the Earth's surface every minute, solar energy is one of the most abundant sources and the fastest growing renewable energy technology (IRENA 2022).Solar photovoltaic (PV), as a renewable energy source, can help to reduce emissions from fossil fuels.PV systems can reduce CO 2 emissions by 0.53 kg kWh −1 of electricity generated (Shahsavari and Akbari 2018).It is becoming a more appealing choice because of its improving cost competitiveness with respect to conventional energy sources like fossil fuels.
The global installed PV market has experienced tremendous expansion in recent years, and over the next 30 years, that market is estimated to increase by 11 times (Chowdhury et al 2020).Australia has a rapidly expanding solar energy market.According to the Australian PV Institute, as of September 2022, Australia had over 3.27 million solar PV installations with a combined capacity of more than 28.2 GW.With almost one in four households having solar panels, Australia also has one of the highest rates of rooftop solar installations worldwide (Department of Climate Change 2022).According to the Clean Energy Council (2022), solar PV, which is Australia's fastest-growing technology to generate electricity, produced 10% of the country's electricity in 2020-2021.At the moment, more than 30% of homes have rooftop solar, and small-scale solar farms are also expanding rapidly (ARENA 2023).
Renewables are expected to account for nearly 95% of the increase in global power capacity through 2026, with solar PV accounting for more than half (International Energy Agency 2021) making PV modules one of the most important types of electricity generation commodities.In recent decades, there has been a significant increase in the large-scale deployment of PV modules (Heath et al 2020).With an estimated lifetime of 25-30 years, the challenges of dealing with large volumes of end-of-life (EoL) PV modules are emerging.
PV systems emit no scope 1 and scope 2 GHG emissions while providing low-cost electricity (Hsu et al 2012).Yet, as large-scale global PV deployment increases, the problem of how to deal with a plethora of PV modules at the end of their lifespan is surfacing.Despite the significant advancements made in PV module production, there is still a dearth of research on the management and recycling of EoL PV modules (Sica et al 2018).The cumulative mass of EoL PV modules is projected to total 80 million tonnes by 2050 (Weckend et al 2016), and would account for more than 10% of yearly global e-waste (Baldé et al 2017).However, the significantly increased uptake in solar PV installation during the past years has made these predictions obsolete and far too low.
The estimated unsustainable levels of waste generation emphasise the importance of a circular economy (Koszewska 2018, Kristensen andMosgaard 2020).The circular economy, which seeks to replace the linear one, considerably lowers waste by prolonging the lifespan of products (Stahel 2019).Often in a circular economy, a product is restored, reused or recycled (Sandin and Peters 2018).By diverting significant amounts of PV waste from landfills and providing valuable source materials for new solar modules, a more circular PV economy would reduce the amount of virgin raw material that would need to be extracted and refined to create a carbon-free energy system (Dreves 2022).Such an approach is critical to keep the technology environmentally friendly even after its typical operational lifetime.
Recycling this volume of EoL PV panel waste is critical to increasing the overall sustainability of solar energy (Corcelli et al 2017).The European Union (EU) has formally recognised this requirement by including EoL PV panels on the list of waste electric and electronic equipment (European Parliament and The Council of European Union 2012).Reuse and recycling have lower environmental impacts than incineration and landfill, while reuse is better for the environment than recycling (Laitala andKlepp 2015, Sandin andPeters 2018).However, the recycling process has a high financial cost and a short-term economic loss, which acts as a deterrent for consumers and industry (D 'Adamo et al 2017, Dias et al 2022).The PV industry need to simultaneously improve its economic viability, practicality, recovery rate, and environmental performance (Chowdhury et al 2020).There is a strong emphasis in European waste legislation on avoiding waste disposal as much as possible and encouraging the re-use of discarded products.In support of a circular economy, the EU set a target for re-use and the recycling of waste to be increased to a minimum of 55%, 60% and 65% by weight by 2025, 2030 and 2035 respectively (European Parliament and The Council of European Union 2012).Extending the useful life of modules through reuse or repair reduces lifecycle environmental impacts by increasing lifetime electricity production for the same energy and material investment in module manufacturing (Heath et al 2020).One key step to implement the circular economy is the formation of second-hand markets (Virgens et al 2022).The value of used products is capitalised in a second-hand market.However, economic inefficiencies develop in market where the quality of a product is invisible to consumers.In markets where one party has more information about the quality of the offered goods, information asymmetries emerge (Stahl and Strausz 2017).The party with this information advantage can determine the quality of the goods, whereas the party with this information disadvantage cannot (Levin 2001).In markets where quality is unobservable to buyers, third-party certification is the instrument used to increase transparency (Stahl and Strausz 2017).The benefits of certification include reduced risk and liability, greater confidence in regulatory compliance, reduced insurance cost, and effective management (Tanner 2000).
A circular PV economy can help reduce the number of new resources that need to be extracted and refined to create a carbon-free energy system by diverting significant amounts of PV waste from landfills and providing valuable source materials for new solar modules (Dreves 2022).There are numerous waste management methods available as solar panels reach the end of their anticipated performance period.They consist of prolonging the performance period through reuse, renovation, or repowering as well as panel decommissioning and recycling (Tsanakas et al 2019).The decommissioned panels automatically enter the waste stream and are either disposed off or, in the best case, recycled.The waste hierarchy triangle mentions several options to treat waste in general, from disposal to preparing for re-use.Moving upwards on the triangle implies an environmentally favourable option.Reuse and recycling have lower environmental impacts than incineration and landfill, while reuse is better for the environment than recycling (Laitala andKlepp 2015, Sandin andPeters 2018).Recycling, while valuable, can create some emissions due to the energy required to breakdown and process the materials (Maani 2020).Reusing solar panels, on the other hand, can help to reduce emissions even further by extending the lifespan on the panels and reducing the need for new manufacturing.

Life time and expected waste volume
According to industry data, a solar PV panel should have a physical life time of at least 25 years.However, it is well recorded that the majority of panels go to waste, because they are replaced by newer panels with high capacity to ensure more electricity generation across a given surface area such as the roof of a dwelling.In addition, predominantly weather events cause many panels not to reach an operational life of 25 years (Majewski et al 2021).Therefore, considering possible reasons for early replacement, it can be assumed that the actual average lifespan of solar panels is less than 25 years.
International Renewable Energy Agency Capacity Statistics 2023 (ARENA 2023) shows an almost exponential increase in solar PV capacity worldwide between 2012 and 2022.In 2022 the overall capacity of solar PV has already surpassed 1 TW and, at the current trend of uptake, a capacity of 7 TW is expected to be achieved by 2030 (figure 1).Based on the overall capacity of solar PV power worldwide, and average weight of a panel of 18.5 kg and at an expected life time of a panel of 20 years, a cumulative waste volume of more than 40 million tonnes can be expected by 2040 and more than 300 million tonnes by 2050 (figure 2).

Product stewardship
It is crucial to make sure that solar panel waste is correctly managed to safeguard the environment and general welfare of the society.Legislated EoL management schemes like a product stewardship scheme or extended producer responsibility (EPR) are essential for reducing waste and to ensure that products have limited impacts on the environment and human health throughout the life-cycle and across the supply chain (Jensen and Remmen 2017).
The level of governmental regulations defines the forms of product stewardship schemes.Product stewardship schemes run by the industry stakeholders are considered voluntary.Their outcomes are usually reported to governments to proof their effectiveness.Mandatory product stewardship schemes are strictly legislated by the government and require industry to adhere to regulations of the schemes.Co-regulatory schemes are also legislated and approved by the government.They are run by an independent administrator or product stewardship organisation (PSO) on behalf of the involved industry.The PSO must ensure all reasonable steps are taken to meet outcomes specified in the regulations.Overall, product stewardship schemes provide better control and oversight for the government in regards to EoL management processes than an EPR (Jensen and Remmen 2017).
An EPR requires from a producer of a product to have the full or partial environmental and/or economical responsibility for a product during its whole life cycle which, therefore, includes the EoL management and a producer has to take responsibility for what needs to be done with the product at the end of its useful life (OECD 2001).An EPR ensures that the producer is not relying on landfilling of the product once it is out of use, because the scheme integrates the environmental characteristics of products throughout the product's life cycle including its manufacturing (OECD 2001).An EPR scheme requires that a price of pollution is embedded in the supply chain and, therefore, polluters have to pay for the environmental impact of a product.EPRs are designed to ensure that the responsibility for recycling and waste disposal rests with the industry and, eventually, the customers.As a consequence, the costs of EoL management are part of the prices of the product and not requested in form of levy at the time of purchase.
Many countries including China and India, have a weak or non-existent policy management system related to waste PV modules (Wu et al 2019).Lack of proper product EoL management can cause environmental problems and loss of recovery materials.In the EU solar panels are included into the general waste legislation, the European Waste Electrical and Electronic Equipment (WEEE) Directive (European Parliament and The Council of European Union 2012).This legislation, however, does not demand recycling and says that EoL management processes for solar panels are to be established and implemented at a member state level (European Parliament and The Council of European Union 2012).Despite the growing concern, there is limited research on optimal EoL management considering recycling and/or re-use due to the long operational lifetime of PV modules and the limited predictability of defects or failures in fielded PV components (Tsanakas et al 2019).
In order to create a long-lasting and competitive market for used PV models, research and development activities as well as business focus has significantly shifted towards sustainable EoL management for PV installation and repair-reduce procedures.

Regulatory environment considerations
The majority of existing EPRs are mandatory rather than voluntary and favour take-back requirements, which vary in scope and extend.Through mandatory targets, and less often through voluntary targets, compliance in regard to collection and recycling of the related product is ensured (OECD 2001).The ultimate goal for EPRs and product stewardship schemes is the reduction of waste and, if possible, to encourage and incentive the design of easy to recycle products containing as little as possible difficult to recycle materials.Consequently, considering EoL legislation, it could be argued that encouraging re-use of solar panels and its components might have a merit.Therefore, the re-use of the frame, glass panel, and junction box of a solar panel and efforts to further increase the lifespan of solar panels like the DuraMAt program of the US Department of Energy (US Department of Energy 2016) should be encouraged by an EoL legislation.
Landfilling is often the cheapest EoL process available and, therefore, alternative EoL processes cannot compete.To address this, some European countries and other jurisdictions like the state of Victoria in Australia have banned solar PV panels from landfills or reduced the landfilling.As a consequence, economically and ecologically reasonable recycling and re-use processes of the panels is under development.This example shows that more stringent regulatory measures like landfill ban can be a powerful tool to change behaviour.It is obvious that such regulatory measures need additional legislations that inhibits circumventing such measures through e.g.exporting waste to other jurisdiction with less stringent regulations.
According to Leyton et al (2022), serial number tracking can provide information about the number of panels installed, where they are installed, who dismantled the panels, and where the panels were recycled.Serial number tracking would provide regulators and governments a powerful tool to monitor recycling rates.
The ownership of the panels also needs regulatory clarification.When the panels are removed from the place of operation, e.g. the rooftop of a private dwelling, and picked up for disposal, it is necessary to define ownership of the panel and responsibility for the EoL processes while in transport to the recycler.
In case of solar PV panels of a commercial solar farm, it can be expected that business agreements between solar PV manufacturers and solar farm operators clarify the ownership for the panels in transit.

Potential product stewardship scheme
A mandatory product stewardship scheme for solar PV panels or a co-regulatory scheme requires participation of all involved industry appears to be more applicable in light of the constantly increasing number of panels and manufacturers, and to avoid free riders which benefit from a product stewardship scheme, but do not contribute to its operation.A potential scheme can be set up to deal with panels from private as well as commercial users (figure 3).In case of commercially used panels the EU's WEEE Directive's legislation business-to-business (B2B) model (European Parliament and The Council of European Union 2012) is very practical in this scenario.Products for professional use only like medical equipment, industrial machines, large manufacturing equipment, servers, is allocated as B2B WEEE or when it became waste as B2B WEEE.Under a B2B WEEE agreement the producer has the obligation to declare that adequate resources are available to finance adequate EoL management processes for the product.This declaration is part of the submission of waste management plans and reports by the producer.The waste management plan is main tool for the legislator to have a clear understanding of the planned EoL processes and to monitor that collection, storage, reuse, treatment and recovery, or as appropriate, disposal of the waste is carried out by the participants of the B2B agreement in accordance with all relevant legislation and best practice.The existence of a waste management plan can be a requirement for the approval of the development of a commercial solar farm.
Enterprise agreements between manufacturers and solar PV recyclers should be encouraged through a product stewardship scheme in case that the manufacturer is not prepared to take panels back.Such agreements can be especially attractive to overseas manufacturers who are expected to ensure that the EoL management processes for their panels adhere to legislation of the jurisdiction with a related product stewardship scheme.Such a model of collaboration between manufacturers and recycler may also be a workable model in jurisdictions where export bans on waste exist.
EoL management of panels from private users is also shown in figure 3.This part of a legislation process can be much simpler compared to a B2B model.To be disposed panels are collected from private dwelling by installers and transferred to recyclers for EoL processing.
For ensuring that disposed panels are processed according to legislation and for documentation of recycling rates, the product stewardship scheme needs to require that retailers and recyclers provide the serial numbers of panels to the regulator or PSO.
Many product steward schemes use weight to legislate recycling rate and recovery.The EU in their WEEE Directive has set specific targets for the recovery and recycling of PV waste to minimise its environmental impact and conserve natural resources.Specifically, the directive requires that at least 85% of the weight of a PV module must be recovered, and at least 80% of the weight of a PV module must be recycled.However, a scheme for solar panels needs to consider the weight of the various components.Silicon PV panels, which account for roughly 95% of the PV market are layered devices whose sides are framed by an aluminium profile (IEA-PVPS 2020, Salim et al 2019).The two components, aluminium frame and glass cover, combined account for ∼80 wt%.Depending on the size of the panel, this number could be even higher.Therefore, a recovery target purely based on weight may have the unintended consequence that only some particular materials are recycled like the frame and glass, and others not, like the solar cells and electric connectors.

Considering a second hand economy for solar PV panels
The preferred option for the EoL management of solar PV is recycling, but it is worth to explore whether an intermediate strong second hand economy for used solar PV panels can play a viable role in the reduction of the waste legacy of solar PV panels, (Agovino et al 2018, Sadik-Zada, Loewenstein 2020).
According to a report by NREL, solar panels degrade at a rate of less than 1% per year, meaning that many obsolete panels might still be functional enough to be reused (Deline et al 2022).The declining efficiency rate of about 1% per year would only reduce panel's efficiency to 80%, compared to its original efficiency, after 20 years of operation (Sharma and Chandel 2013).In fact, according to recent data from testing around 1450 solar panels at the Rockhampton council collecting facility in Queensland, more than 31% of the retired panels can be reused instead of being recycled (Peacock 2022).It can be expected that many panels are damaged during their removal, rather than being damaged while in operation on the rooftop.Therefore, it can be assumed that many panels, which go to waste, are still in good working order and could be re-used.
However, the current re-use scenario for solar panels is a niche business that is viewed as unappealing for a number of reasons.Studies show that the development of second life activities is constrained by (i) financial feasibility for both the supply and demand sides, (ii) legal regulations, (iii) operational issues, and (iv) market acceptance (Pareek 2021, Heide et al 2022).The absence of a secondary solar market suggests the requirement for proof of quality standard adherence.However, economic inefficiency develops in marketplaces where quality is invisible to consumers due to asymmetrical information.In markets where there is an imbalance of information between the negotiating parties about the quality of the offered goods, information asymmetries emerge (Stahl and Strausz 2017).The issue is especially acute in secondary product markets where 'lemons' (inferior quality goods) are difficult to identify (Akerlof 1970).Due to these shortcomings, there is a need for third-party certifications that can promote market transparency by confirming product quality.Programmes that offer certification typically have more straightforward and reliable means for preserving visibility (King et al 2011).Prior research suggests that consumers have high willingness to pay when the products offer positive environmental attributes (Peattie and Crane 2005, Drozdenko et al 2011).However, in some cases, the positive environmental value of the circular product might not be able to outweigh the negative perceived risk of purchasing a product that may be of inferior quality.This issue can be overcome by the support of third-party product certification.Even though there are a few independent businesses conducting various tests to ensure that the used solar panels fulfil safety, quality, and performance standards, there is no set process for certification of second hand panels (Tsanakas et al 2019).Re-certification, which covers installation and maintenance requirements as well as safety and performance efficiency testing, is necessary due to consumers ′ scepticism about the efficiency and safety of used panels.The current literature around secondary solar panel market point towards the lack of certification and a formal business scenario (Tsanakas et al 2019).
Product certification serves as evidence that a given product satisfies all conditions or requirements specified in a contract or by a private, public, or international entity.Product certification informs markets and clients that a certain product is safe to use, and the quality control and performance tests were passed.In fact, consumers ′ willingness to pay increases when the claims are supported by a third-party certification since labels help increase credibility of product claims (Aguilar andVlosky 2007, Darnall et al 2018).Certification guarantees adherence to all necessary rules and performance evaluations and the procedure is governed by national and international rules and regulations depending on the intended market.
In order to make sure that the solar panels being utilised meet the performance and safety requirements established by industry-wide norms and are capable of delivering the advertised performance, solar panel certification is required.Third party organisations like the International Electrotechnical Commission or Underwriters Laboratories provide certification for newly manufactured panels giving buyers the certainty that the solar panel system is secure, dependable, and will function as intended.However, there is no such institution present for the secondary solar panel market (Heide et al 2022) hindering the growth of the reused PV market.
Before a panel enters the second hand market an electric safety and compliance certificate or equivalent needs to be provided by a certified electrician or equivalent.The remaining capacity and age of the second hand panel needs to be certified, so, consumers can be guaranteed that the second hand panel provides a minimum capacity in watts.Again, this certificate would need to be provided by a certified individual or organisation to ensure legal compliance before the panel enters the second hand economy.Complying with the principles of a circular economy and as part of product assurance processes, such certification should communicate with a solar panel tracking platform.It is, therefore, recommended that the second-hand solar panel certification standards should be part of a solar panel EoL legislation.However, unless a simple and cheap testing regime for solar panels is established, the costs of testing may be an impediment for the re-use of functional solar panels.Nevertheless, if the testing is reduced to just measuring the operating voltage and current to establish the remaining power of the panel in watts, the costs can be very limited.If the tests require establishing the mechanical stability and weather proofing of the panel the costs may be economically not feasible considering the cost of new solar panels.In addition to mechanical stability and weatherproofing assessments, electrical insulation testing, such as Megger insulation testing, presents another layer of complexity in the refurbishment process of solar panels.
While reduced testing that measures only the operating voltage and current could potentially lower costs (Enslin et al 1997, Chung et al 2003, Podder et al 2019), the assertion that costs can be very limited is speculative without comprehensive cost projections.Future research should aim to establish detailed economic analyses of testing processes.Such analyses will be vital in understanding the true cost implications and in developing supportive policies that could make the reuse and refurbishment of solar panels more economically viable.

Financing EoL processes for solar PV panels
It is well established that consumers prefer collection of unwanted products without paying a levy at disposal of the product.This is an important factor to increase collection rate and decrease illegal disposal.(Sasaki 2004, Monier et al 2014).An example is the comparison of the Japanese and Swedish EPR systems for e-waste.The Japanese scheme has mandatory targets for recycling and requires that the consumer pay a recycling fee at disposal while the Swedish system does not.The Swedish scheme achieves a higher collection rate, whereas the Japanese system has greater recycling rates for collected materials.This indicates that besides the levy other factors are affecting the recycling rate depending on the jurisdiction (Sasaki 2004, Monier et al 2014).Therefore, an upfront levy like an advanced disposal fee (ADF) for supporting a product stewardship scheme for solar PV panels is recommended.The ADF can be charged at retail for consumer convenience and to avoid unlawful disposal of panels.However, due to the presumably large number of retailers and/or installers raising a levy at retail will probably cause a rather extensive administrative burden.A levy at point of import or distribution from the local manufacturer may also be possible.Such a scheme reduces administrative burden due to the smaller number of organisations involved at this point in the supply chain.However, in case of such an import tax, it is necessary to avoid implications with trade agreements or raising the suspicion of protecting locally produced panels against international competition.
It has also been demonstrated that high collection rates are achieved where a fully funded PSO is overseeing the product stewardship scheme This would require that the levy is set at a level which not only allows to support collection and recycling of the panels, but also provides funds to support the operations of an effective PSO (Monier et al 2014).
At the current stage, the level of the levy is difficult to define as it will need to consider also financing EoL managing processes for existing panels.Considering existing product stewardship schemes for other products, a levy of few per cent of the current sales value of solar PV panels seems appropriate.Considering the capacity increase in solar PV output (IRENA 2023) it can be estimated that additional 500 million panels were installed in 2022 worldwide with, of course, significant variations between the various nations.This calculation does not take into account the replacement of existing panels.Therefore, there is surely some capability to define an appropriate levy, especially in nations with a significant per capita uptake of solar power like Australia.Nevertheless, it will be prudent to continuously monitor and, if necessary, adjust the levy to guarantee high collection and recycling rates over time (Dias et al 2018).
B2B agreements between commercial consumers of panels and manufacturers will define EoL processes and the related cost sharing, so, a levy does not apply.However, if panels are not recycled by the manufacturer, but given to a recycler, a levy needs to be paid to the PSO.

Conclusion
Various examples of robust and successful EoL legislation exist worldwide and demonstrate the benefit of having circularity of materials and related waste reduction.For solar PV panels, an EoL legislation, if properly designed, can address existing and new panels and supports the creation of a second hand economy for the panels.Like in case of exiting EoL management schemes it will be essential to have a levy on the panels preferably at purchase to subsidies costs for the recycling industry and finance an effective producer responsibility organisation, which regulates the scheme.About 3 billion solar PV panels are installed worldwide containing about 1.8 million tonnes of high grade silicon, the current value of which is about USD 7.2 billion.Considering this, recycling of solar PV panels has the potential to be commercially successful.Considering that almost 3 billion solar panels are installed worldwide, it conceivable that a viable second hand economy for reusable solar PV panels will be established in future.However, this requires a product stewardship scheme that encourages a second hand economy for solar panels and regulates measures that provide quality guarantees for consumers of second hand solar PV panels.Additionally, to realise this vision, it is imperative to conduct a comprehensive feasibility assessment that addresses technical, economic, and logistical challenges (Gippsland Climate Change Network 2021).A thorough cost analysis should be undertaken to evaluate the expenses involved in collecting, refurbishing, testing, and distributing second-hand panels.This analysis will provide a clearer understanding of the viability of a second-hand economy in terms of both economic and environmental benefits.While the potential for a second-hand economy for solar panels is substantial, it is essential to approach this endeavour with a long-term vision.To harness this potential, a detailed feasibility assessment, including a thorough cost analysis of refurbishing, is imperative.Recognising that achieving this goal may require incremental steps, technological advancements, and ongoing refinements, we must ensure that the pathway to success is both economically feasible and environmentally impactful.A future where the reuse of solar PV panels is a practical reality, needs to be backed by policies that ensure economic and environmental benefits.

Figure 1 .
Figure 1.Expected capacity increase for solar PV until 2030.

Figure 2 .
Figure 2. Cumulative waste volume of solar PV panels until 2050 based on panel's life time of 20 years and weight of 18.5 kg.

Figure 3 .
Figure 3. Flow chart of possible product stewardship scheme for solar PV panels.