The PV industry continues to push its credentials as a technology that addresses one of the fundamental challenges of our times – climate change. 5.5 GW of new PV capacity was installed worldwide in 2008, bringing the total installed capacity to 15 GW. And the European Photovoltaic Industry Association (EPIA) predicts 2009 could see 7 GW of new capacity, and total capacity could reach 22 GW by 2013.
First Solar has developed a process for recycling CdTe thin-film modules. The process has been scaled to full production at each of its manufacturing facilities in the US, and is being replicated in Frankfurt an der Oder, Germany.
Under First Solar's pre-funded module collection and recycling programme, First Solar manages the logistics of collecting end-of-life modules, and provides packaging and transportation to a recycling centre.
The recycling process itself must be financed. First Solar finances the programme by setting aside funds for collection and recycling at the time of module sale.
- Modules are shredded into large pieces before being crushed by a hammer mill to pieces typically smaller than 5 mm in order to break lamination bonds;
- Semiconductor films are removed in a slow rating leach drum in a process taking 4–6 hours. Weak sulphuric acid and hydrogen peroxide is added to the glass to achieve an optimal solid-liquid ratio. The films are etched from the glass during the leach cycle;
- Glass is separated from the liquids in a classifier;
- The material is then moved to a vibrating screen separating the glass from the larger ethylene vinyl acetate (EVA) pieces. The EVA is deposited into another conveyor and collected, whereas the glass falls through the screen to a chute where it is taken to the rinsing step;
- After being cleaned, the glass is deposited into containers for recycling and the rinse waters are pumped to a precipitation system for metal recovery;
- The metal compounds are precipitated in three stages at increasing pH using sodium hydroxide. When the solids have settled and been made into a metal rich filter cake, it is sent off for processing by a third party where they can be processed to semiconductor grade raw materials for use in new solar modules.
The process can recover 90% of the glass for use in new products and 95% of the semiconductor materials for use in new solar modules.
According to BNL, the recovery of tellurium is 80% or better and it can be sold as commercial grade (99.7% Te).
However, in its whitepaper Toward a Just and Sustainable Solar Energy Coalition the Silicon Valley Toxics Coalition (SVTC) argues that for solar to be truly green, industry must reduce and eventually eliminate the use of toxic materials and develop environmentally sustainable practices. Further, it maintains that producers must take responsibility for the lifecycle impacts of their products by testing new materials and processes, expanding recycling technologies, and designing products for easy recycling. In short, SVTC argues for extended producer responsibility.
PV modules for example contain substances such as glass, aluminium and semiconductor materials that can be successfully recovered and reused, either in new photovoltaic (PV) modules or other products. And despite such waste volumes being small at present, PV CYCLE, the European voluntary PV recycling initiative, says that the industry must start collection and recycling of PV panels as soon as possible, to be ready for the increase in volume over the next decade.
In November 2007, its commissioned study The Development of the Take Back and Recovery System for Photovoltaic Products, funded by the German Federal Ministry for the Environment, Nature Conservation and Nuclear Safety (BMU) and co-financed by EPIA and BSW, estimated that there will be 35,000 tonnes of PV waste by 2020.
The good news is that recycling of thin-film and silicon modules is already taking place (see boxes within this article on First Solar and SolarWorld recycling schemes).
And PV CYCLE, established by the European PV industry in July 2007, aims “to implement the photovoltaic industry's commitment to set up a voluntary take back and recycling programme for end-of-life-modules and to take responsibility for PV modules throughout their entire value chain.”
The members have signed a joint declaration committing them to these actions, and the goal is to collect a minimum of 65% of PV modules installed in Europe since 1990, and recycle 85% of waste.
PV CYCLE's proposals include obliging producers to clearly label their products, so that owners know how to handle solar panels when decommissioned, and giving information to those receiving and treating the end-of-life panels. One idea that has been put forwards is to state a central telephone number and/or internet address on products.
PV CYCLE is hoping to launch various pilot projects this year, the first having started in May (see Chevetogne dismounting). The organisation also foresees the establishment of a monitoring committee, with officials from the European Parliament and the European Commission and representatives from NGOs, and a separate auditing scheme.
PV CYCLE's Managing Director, Jan Clyncke, says there is a real will to recycle in the industry: “It is not a PR event, it is a concrete project. The industry has gathered together and is committed to create a voluntary take-back and recycling scheme and implement it as soon as possible. We want to take responsibility for the entire life-cycle of a PV module. We want to make the photovoltaic industry ‘double green’.”
“Joining the Association will automatically involve agreeing with the environmental agreement and sharing the initial and running cost in a fair way, as said in the PV CYCLE Declaration of December 2008. In addition, the General Assembly of PV CYCLE approved early June 2009, a resolution introducing in January 2010 the payment of a contribution fee for the collection, the recycling, the declaration of and auditing on reported figures and the start of an escrow fund,” Clyncke added.
However, speaking to Renewable Energy Focus, Dustin Mulvaney, Switzer Fellow and contributor to the SVTC report, criticised the voluntary element of PV CYCLE: “There's really nothing that says that the industry actually has to fulfil its [recycling promises] by joining the association.”
SolarWorld has operated a pilot scheme for recycling PV since 2003, where plastic components are removed first by a thermal process before the silicon wafer is recovered through etching. SolarWorld also recovers silicon from broken solar cells.
SolarWorld re-uses the silicon granules, and everything else is either sold or sent for recycling/disposal.
The take-back of modules is organised via a ‘bring-in’ system at SolarWorld.
- Rack-mount modules are incinerated where the plastic components are burnt in a semiconductor-protecting process at 600°C. Remaining materials such as solar cells, glass and metals are separated manually;
- Glass and metals are sent for recycling;
- Solar cells are re-etched to the wafer;
- Glass could be suitable as raw material for float glass recycling.
According to PV CYCLE's 2007 study, both recycled and new wafers are of equal value electrically after having undergone solar cell processing.
SolarWorld's recycling process tries to keep as much of the original wafer thickness as possible.
The process can recover more than 84% of the input module weight with up to 6N purity of the fractions. The glass (>90%) is for use in new products and 95% of the semiconductor materials for use in new solar modules after remelting. The energy of the polymer incineration could be used in other processes or for pre-heating new charges in future productions.
The thermal process recovers 0-98% intact cells depending on prior damage to the modules, type of module structure and the solar cells used. If the cells have edge chippings, micro cracks, etc, they can normally not be recycled into an intact wafer, and would instead be allocated for obtaining silicon raw material.
The lower the thickness of the cells, the lower the yield. Thick wafers (>200 μm) produce less breakage and can often be re-etched from solar cells generating a yield of more than 97%. For wafers with thickness <200 μm, things are more tricky.
So what are the current European incentives?
The 6th Environment Action Programme (EAP) is a decision of the European Parliament and the European Council adopted on 22 July 2002. It sets out the framework for environmental policy-making in the European Union (EU) for the period 2002–2012 and outlines the actions that need to be taken to achieve them. The 6th EAP identifies four priority areas:
- Climate change;
- Nature and biodiversity;
- Environment and health; and
- Natural resources and waste.
When it comes to waste, the revised directive 2008/98/EC sets the basic concepts and definitions related to waste management and lays down waste management principles such as the ‘polluter pays principle# or the ‘waste hierarchy’.
Other examples of European legislation are the EU the Waste Electrical and Electronic Equipment (WEEE) and Restriction of Hazardous Substances (RoHS) directives established in 2003 to minimise the amount of electronic waste heading for landfills and incineration. RoHS restricts the use of certain substances, whilst WEEE regulates the collection, treatment and disposal of products, and places restrictions on their design.
PV panels, though, are not included in this legislation. However, PV CYCLE aims to conclude an Environmental Agreement with the European Union based on the European Commission Communication on Environmental Agreements (COM(2004)412).
Several European Community directives on waste and recycling also detail the principle of extended producer responsibility (EPR), according to which producers take end-of-life responsibility for products. But again, these are not specified for PV.
The US is no better
There is no current federal regulation specifically governing the recycling of PV panels in the USA but, according to the SVTC, they often fall under regulations for waste disposal and hazardous waste, just as in the EU.
End of life disposal of solar panels is based on the Federal Resource Conservation and Recovery Act (RCRA), and on state policies like California's Hazardous Waste Control Law (HWCL).
In order to be deemed ‘hazardous’ by regulators, decommissioned or defective solar panels must fail to meet the US Environmental Protection Agency (EPA) Toxicity Characteristic Leaching Procedures (TCLP) standards in accordance with the RCRA, or on applicable state policies like the Californian HWCL.
California's HWCL is stricter than federal regulation for hazardous waste but, according to SVTC, “of the 73 Bills related to the solar PV industry that were introduced in the California Legislature during 2007 and 2008, none addressed the manufacturing or end-of-life hazards discussed in [their white paper]. Most of the Bills focused on installation targets and tax incentives/rebates for photovoltaic adoption.”
Mulvaney warns that companies could choose to move their business elsewhere if they are laden with too much red tape, a big issue for the Californian semiconductor industry at the moment. However, he also suggests that since the solar industry receives generous Government subsidies, there is a case for holding it to higher standards.
How are PV panels recycled?
Panels must be taken down and collected before recycling can take place. V.M. Fthenakis and P.D. Moskowitz – at the Brookhaven National Laboratory, National Photovoltaics Environmental Research Center in the USA – have proposed three collection models in The Value and Feasibility of Proactive Recycling, available on the BNL website.
- Utility paradigm: large end users (utilities) are the primary owners and servicers and are therefore responsible for getting end-of-life modules to recyclers. Costs are embedded in the rates charge by the utility;
- Battery paradigm: manufacturers are collectively responsible for collecting and transporting modules to recyclers through the incorporation of a collectively supported PV-module recycling entity;
- Electronics model: manufacturers are individually responsible for collecting, consolidating, and transporting obsolete modules to the recyclers. Recycling services could be paid for by the generator, the manufacturer, or an escrow fund set aside when the PV systems were originally purchased.
At the beginning of May, PV CYCLE took part in its first major dismantling of end-of-life solar panels in Europe together with partners Provincial Domain of Chevetogne and the electricity installer Nizet.
Chevetogne was one of the first major solar heating systems in Europe, and one of the first 16 PV pilot plants initiated and supported by the European Commission in 1983. The dismantling will serve as a learning experience for PV CYCLE, which plans to have its recycling scheme in place across Europe by 2015.
“The solar modules installed here have supplied clean, renewable energy for the past 26 years. Now that they have reached their end of life, PV CYCLE takes the responsibility to collect and recycle them. This is a first major documentation of the voluntary programme we are about to roll out across Europe. In doing so, we make photovoltaic energy truly double green,” Clyncke said at the dismantling.
Mulvaney points out that the chosen collection model will affect the overall cost of recycling: “We're working with the industry [in the USA] to find out exactly what model is going to work best on the collection side… if we want to set up a recycling policy, we need to know which model it is going to be based on, because they are all going to have different costs associated with them.”
From a purely technical perspective, recycling is certainly viable today. As Mulvaney explained to Renewable Energy Focus: “One of the things working in favour of the solar industry is that the products – once you get down to the semiconductor – are pretty uniform.” (See First Solar and SolarWorld for examples)
He warns, however, against the dangers of intellectual property monopolies: “The problem would be that if one company figures this out first and they patent the process, that keeps any of the other companies from having access to the technology.” This is exactly what PV CYCLE wants to avoid – and has to avoid – due to European competition regulations.
On the other hand an open recycling industry could cause other intellectual property issues: “If one company starts collecting all of the industry's panels… the competitors start seeing where their other competitors' modules are failing.” Mulvaney does not believe that this is enough to push companies to start in-house recycling. “They would probably just not recycle at all,” he added.
Which brings us to the economic aspects of recycling – is it really financially viable?
“Currently, economic incentives may be inadequate to move the PV industry into voluntary recycling. However, this may change in the future, as more economic incentives may be given to developing clean technologies, preventing pollution and reducing CO2 emissions,” Fthenakis and Moskowitz conclude.
On the other hand, Dr Karsten Wambach, Manager at Sunicon, the silicon subsidiary of SolarWorld, told Renewable Energy Focus that the financially viability of recycling is a question of supply: “The waste streams are very small … therefore recycling is hardly viable today. In the future, with larger waste streams, it will be a must. The PV producers are well aware of the producers' responsibility and will take care for appropriate recycling on a voluntary basis. The system will be scaled up with future needs ensuring high recycling standards and best practice approaches with certified and monitored service providers.”
SVTC has identified the following emerging PV technologies:
- Dye-sensitised solar cells, which release electrons from (in one particular case) titanium dioxide covered in a pigment that effectively absorbs sunlight;
- Organic solar cells made of biodegradable materials, which often suffer from the degrading of materials during operation, making them unstable and not yet commercially viable; and
- Hybrid cells, which combine various technologies, and therefore present all the production hazards associated with their constituent semiconductors.
The photovoltaic industry is successfully developing lead-free soldering used for the electrodes of the cell, wiring material and terminal boxes of the modules. For instance, Mitsubishi Electric introduced its new UD5 series of 100% lead-free solder PV modules in July 2007. Sharp completely eliminated lead solder in new products released after April 2005 in North America, Europe, China and Japan. Kyocera has developed lead-free solar modules using tin-based solder since 2004.
Mulvaney shares Wambach's assessment that PV recycling is not economically viable today, in the absence of a carbon price: “It's not quite clear that [it's] a profitable thing for a company to be reusing the panels. A lot obviously depends on some sort of carbon tax or carbon pricing, because what makes it inefficient economically to recycle right now is that it is cheaper to use the raw material, even though [using the raw material] is far more energy intensive. … If energy is correctly priced, [i.e. includes carbon pricing] it could be economically competitive.”
Recycling of thin-film panels may be more feasible: “With the CIS [copper indium selenide] and CIGS [copper indium gallium selenide] and the CdTe [cadmium telluride] – the thin-films – [those players are] going to have to use recycling in the industry, because indium and tellurium are rare. They're not found in sufficient quantities in mines and crust to scale these technologies up sufficiently.”
This is in contrast to ‘traditional’ PV, as silicon is an abundant raw material. The market bottleneck experienced in recent years is clearing, with the markets even currently being oversupplied.
Mulvaney suggests that companies may use recycling more as a branding exercise, gaining indirectly, rather than from the recycling itself. As buyers of solar panels tend to already be converted to the ‘green cause’, he believes branding emphasising recycling credentials could increase companies' market competitiveness. “Recycling may become a requirement put into local solar financing rules or power purchase agreements. So those who do not take back or recycle will be shut out of those markets.”
PV CYCLE's Jan Clyncke believes the recycling of PV modules is already economically and technically viable. “The volume of production waste could ramp up the PV recycling market much faster than expected. Within ten years time this leverage could be more than sufficient to replace the decreasing amount of production waste by the increasing amount of end-of-life PV modules,” he told Renewable Energy Focus. “There are not many companies that recycle and there are already PV modules to recycle such as the damaged ones. In addition, slowly, the oldest PV generators [are reaching] their end-of-life and have to be recycled…this is expected to be a growing trend, with a significant increase after 2020.”
So what legislation and incentives need to be in place to make the recycling of PV panels viable?
The SVTC argues that legislating extended producer responsibilities, such as manufacture take-back requirements, “will be key to ensuring that these complex and diverse solar PV products can be safely recycled.” Making manufacturers responsible for the lifecycle impacts of their products would give them an incentive to design and produce solar panels in such a way as to make recycling and disposal easier.
In its 2007 study, PV CYCLE urges producers to “continue to look for technical solutions which would solve the conflict between manufacturing modules with a very long shelf life and the issue of environmental impact and recycling-compatible construction.”
PV CYCLE's Clyncke remarked at the beginning of 2009: “We will only be able to say that solar energy has become truly sustainable when the life cycle of photovoltaic modules is closed, allowing the industrial use of recycled raw materials necessary to their manufacturing.”
Estimated waste quantities (Source PV CYCLE, November 2007)
|In t (1 MWp equals 75 t)
Proportions of various technologies of waste expected to be generated in Europe (Source: PV CYCLE)
|In t (1 MWp equals 75 t)