On 4th March 2020, the European Commission announced that Europe will plan to be climate neutral (net-zero greenhouse gas emissions) by 2050. Europe’s energy market will decarbonize into a renewable energy market where solar, hydro and wind energy provide most of Europe’s energy demands. Similar efforts are being made in London, where the Mayor has committed for London to be a zero carbon city by 2050. The International Energy Agency (IEA) has also forecasted that solar energy will be the main driver of growth in global electricity over the next decade with the onshore and offshore wind taking second and third place, respectively. All of these are good news but since solar and wind power are relatively young technologies, there exists a real concern of waste- often overlooked. What happens when the renewable energy generators reach the end of their lifetime and is there a way to recycle solar photo-voltaic (PV) modules and wind turbines?
SOLAR POWER
According to IEA, in 2018, solar power generation globally was 570 TWh. In 2019, solar PV generation increased 22% (+131 TWh). With this growth rate, it is expected to reach more than 3000 TWh of solar PV power generation by 2030. According to a future energy market scenario, 60% of Europe would derive its daily power from sun before 2050.
All these estimates suggest that a large number of solar PV modules are going to be produced in the coming decades. According to a report by the U.S. Department of Energy, the PV panel waste could total 78 million tonnes globally by 2050. Putting all this waste into landfills is neither practical nor possible as the PV cells contain a certain amount of toxic substances; and land is already a very valuable resource which has a very competitive market.
Solar panels have, on average, a lifespan of 25 years. Recycling or repurposing these solar PV panels can unlock a large stock of raw materials and other valuable components. The recovered materials could be worth more than USD 15 billion by 2050. And if recycled, this amount of waste could be used to produce further 2 billion new panels. As of 2016, there was a cumulative global PV waste of 250,000 tons. With respect to the regulations, PV panel waste still falls under the general waste but the European Union (EU) has defined it as e-waste and set certain standards for the disposal of PV waste.
- Recycling Silicon Based PV:
It is a common myth that solar panels cannot be recycled. Studies have shown numerous ways to recycle solar panels with up to 96% efficiency. The process requires time to be implemented widely and needs collaboration within the designing and recycling units.
Figure 1 Composition of silicon based solar modules and thin-film based modules.
Figure 1 shows the waste generated from the two main types of solar panels: silicon based, and thin-film based. Majority of the PV panels are made of glass- thin-film PVs have 89% of glass in them compared to 76% for silicon based PVs. There is proportionally more plastic and aluminum in silicon-based PV panels. The rest of the composition is often trace metals which comprises approximately 1% of the entire module.
Figure 2 (shown below) illustrates the process of recycling both the PV panels. The left side of the figure shows the steps involved in recycling silicon based solar panels. The first step involves disassembling the actual product to separate aluminum and glass parts where almost all (95%) of the glass can be reused. All the external metal parts are used for re-molding cell frames. The remaining materials are treated at 500°C in a thermal processing unit to break the binding between the cell elements. The plastic which evaporates is reused as a heat source for further thermal processing. The green hardware is physically separated and 80% of these can be readily reused. The remaining silicon particles, called wafers, are etched away using acid. The wafers are then melted to be used again (recycling rate of 85% of the silicon) for manufacturing of new silicon modules.
Figure 2 Steps involved in the recycling process of solar PV.
- Recycling thin-film based solar panel:
The process for recycling thin-film based PV modules is more involved as shown on the right side panel of Figure 2. The first step involves putting the PV panels into a shredder and ensuring that all the particles are no longer than 4-5mm with a hammermill. Unlike the silicon based PV, the remaining substance consists of both solid and liquid material. They are separated with a rotating screw where the solid parts are rotating inside a tube while the liquid drips into a container. The process of precipitation and dewatering is done to the liquids to ensure its purity. And the solid substance goes through metal processing to separate the different semiconductor materials. On average, 95% of the semiconductor material is reused through this process. To extract the glass, the solid matters which are contaminated with so-called interlayer materials are removed through a vibrating surface. After that, the material is rinsed and pure glass is left behind. This process saves 90% of the glass elements which can be easily reused.
These recycling methods for both silicon based and thin-film based solar PV modules are predicted to generate $450 million worth of recycled materials by 2030. 60 million new solar panels can be manufactured from the old recycled solar panels by 2030 and about 2 billion new panels from 2050. These upcycled solar panels can generate an extra capacity of 630 GW.
WIND POWER
As of 2019, the combined onshore and offshore wind power generation was about 1400 TWh which is more than twice that of solar power. Despite having the largest absolute increase in renewable growth, according to IEA, it is not on track to reach the sustainable development scenario. China has the most onshore wind capacity additions in the world at 23.8 GW (for 2019) and the growth is increasing every year. On the other hand, India, Brazil and the EU have a decreasing onshore wind capacity additions per year.
Like solar panels, wind turbines have a lifespan of about 25 years. At the end of its lifetime, the wind turbines can be recycled. Currently, they have a recycling rate of 85% to 90%. These recyclable components of the wind turbine include the foundation, tower, components of the gearbox and generator. The wind turbine blades are non-recyclable. They are built of composite materials which can withstand hurricane winds. Therefore, they cannot be easily crushed, recycled or repurposed.
Since the beginning of 2020, about 2.5 million tonnes of composite material are in use in the wind sector globally. As the first wave of commercial wind turbine installations now approaches their end of life, the problem of blade disposal is beginning to emerge as a significant factor for the future. About 14,000 wind turbine blades will be decommissioned in Europe in the next five years. It is estimated that 800,000 tonnes of blade material will need to be recycled annually by 2050. Figure 3 illustrates how most of the wind turbine blades are sent to landfills.
Recycling wind turbines:
Despite there being no commercially viable options to recycle wind turbines with 100% efficiency, certain companies are coming up with innovative ways to address this issue.
- Global Fibreglass Solutions based in Washington has been transforming fibreglass composites into small pellets, called EcoPoly. The pellets, as shown in Figure 4, can be used as injectable plastics, or highly waterproof boards that can be used in construction.
- Veolia, a French recycling group is researching how to use pyrolysis on a laboratory scale to recycle turbine blades. At about 450-700°C, the chopped up blades go through pyrolysis where the composite fibres are broken up. The recovered fibres can be reused in other industries to make glues, paints and concrete.
- Wikado, a children’s playground of 1,200sq m in the Dutch city of Rotterdam, is made from unwanted wind turbine blades. It consists of a slide tower, tunnels, ramps, and slides all made from five discarded wind turbine blades as shown in Figure 5.
Figure 5 Old turbine blades turned into a playground, Wikado.
- Since Europe has restrictions on the disposal of wind turbine blades, similar playground and outdoor seats are built in the Dutch city of Terneuzen, two bus stops in Almere, a seat beside Rotterdam’s famous Erasmusbrug bridge.
- In Denmark’s city of Ålborg, an architect from Rotterdam’s Superuse Studios is currently waiting for planning permission to turn two 55m blades into a bridge.
As mentioned before, these solutions are not commercially viable and cannot be replicated on a large scale yet. But as the governments start to put restrictions on the disposal of wind turbine waste, more innovations are being made to recycle 100% of the wind turbines. Currently, Europe has started to think creatively but as other countries start to make similar regulations and as the wind turbine waste keeps increasing, there will be more viable innovations to dispose of the waste properly and it will allow existing technologies like EcoPoly to grow.
Planet Rescue 101 