Photovoltaics show excellent promise in the supply of renewable, clean energy. In addition, advances in technology make this energy source more accessible and affordable. However, they still have some challenges to overcome, such as the environmental impacts of thin films.
This article addresses the impact of thin films and the toxic materials which they may comprise. We will analyze the effect over the entire life cycle of thin film solar cells from the initial production processes through to their disposal.
We will discuss if the benefits of using solar energy over fossil fuels outweigh the adverse side effects of using highly toxic materials to collect energy.
Thin Films and Renewable Energy
Thin film technology represents a significant step forward in renewable energy development. While the materials making up the cells prove potentially bad for the environment, the film allows for a more efficient and cost-effective solar energy collection.
Thanks to these advances, solar power is within reach of the standard household at a reasonable cost. In addition, the delicate nature of the film minimizes the use of harmful materials, thereby limiting the environmental impacts of thin films.
While these do not represent ideal components, they allow for far cleaner energy production than traditionally possible. As a result, they do not have the same negative environmental impact as burning fossil fuels.
The statistics on the environmental impact of thin film and traditional energy production speak for themselves:
- Thin film photovoltaics typically emit 20 g CO2/kWh instead of a fossil fuel plant’s 500 to 1,000 g CO2/kWh output.
- Photovoltaic cells release only 2% to 4% of priority pollutants compared to fossil fuel plants.
- On the downside, manufacturers use several heavy metals, such as cadmium, to create solar cells. However, the glass encapsulating the components renders them harmless, with 99.5% to 99.96% of the heavy metal contained within it.
- Replacing grid power with solar cells reduces GHGs emissions by 89% to 98%.
Gases Leading to Hazardous Waste
While the performance of photovoltaic systems is relatively clean, their manufacture is not. One of the primary environmental impacts of thin films relates to the toxic materials the manufacturer uses when making the film.
Thin film cells use more harmful substances than the older silicon technology. The substances at play include:
- Hydrogen Flouride
- Nitric Acid
- Hydrochloric Acid
- Sulfuric Acid
The high-heat deposition process causes results in the release of harmful gases. These gases pose a health risk to workers and the surrounding community if the manufacturer does not handle them properly.
The issue of what happens when the cells reach the end of their lifecycle also remains. Breaches in the cells could potentially lead to releasing toxic gas and compounds.
Such compounds could contaminate the air, food, and water supply without proper management.
However, there is some light at the end of the tunnel. Researchers using the Toxic Characteristic found that the cells are relatively safe and that the harmful compounds are unlikely to leak out unless something breaches the capsule.
The researchers found that even the molten glass in vintage cells held up against much pressure. The results highlight the importance of recycling panels at the end of their lifecycle rather than trashing them.
Being Aware of Energy Consumption
The current industry trend focuses on manufacturing techniques that improve capacity. The available processes include the following:
- Ion-assisted deposition
- Plasma immersion ion implementation
- Vacuum arc deposition
- High-power impulse magnetron sputtering
- Laser ablation and deposition
Achieving the optimal balance between energy consumption and material utilization efficiency is important.
Research shows that material utilization efficiency correlates with higher temperatures and lower pressure. By contrast, energy efficiency lowers at optimal material utilization levels and improves with lower temperatures and higher pressure.
Researchers peg the ideal reaction condition at 623K, 500Pa, to reach the optimal energy efficiency of 0.083%. To achieve the result, however, you must sacrifice material utilization efficiency, which drops to 0.5%.
Scientists must address this catch-22 situation. Balancing optimal energy usage with maximum material utilization would reduce both the amount of energy and harmful materials necessary during the manufacturing process.
For now, however, manufacturers focus on energy efficiency as it pertains to ion bombardment as this leads to:
- Better adhesion
- Lower substrate temperatures
- Reduction of intrinsic stress
- Optimization of texture, solid-state surface processes, and plasma processes.
Disposal of Thin Films
The most challenging aspect of thin films comes when dealing with their disposal. Fortunately, the modules have a lifespan of 20 to 30 years, meaning they only need replacing sometimes. However, when the time comes, it’s essential to consider the impact of heavy metals.
With the increasing popularity and accessibility of thin film solar cells, a pertinent issue involves how to encourage the general public to dispose of cells responsibly.
Large businesses replacing hundreds of solar panels might look for ways to recoup some of their investment through recycling. The average homeowner, however, may prefer the convenience of using a landfill.
Residential panels will likely become an issue in much the same way as Ni/Cd batteries have. Today in America, much of the cadmium in landfills originates from Ni/Cd batteries.
Solar panels have an advantage as many also contain tellurium. The value of this compound makes recycling a potentially lucrative option. Coordinating the collection of boards and incentivizing their recycling makes for an important project moving forward.
Key Takeaways and Further Reading
The use of heavy metals and toxic compounds during the manufacture of photovoltaic cells is troubling. However, the deposition process effectively encapsulates these compounds and prevents leaching. For more information on this process, read Thin Film Deposition Explained.
For now, it’s imperative to focus on reducing the environmental impacts of thin films by incentivizing or encouraging recycling.
Thanks to the use of heavy metals during manufacture, solar energy appears less clean than some might think. However, compared to fossil fuel usage, it is light years ahead of the pack. Photovoltaic power is renewable, cleaner, and sustainable. Researchers have some work to do to improve this energy source, but it is a distinct improvement over coal or oil.
Fthenakis V. 2009. Sustainability of photovoltaics: The case for thin-film solar cells. Science Direct.
Manova, D., Gerlach, J.W., and Mandl S. 2010 Thin Film Deposition Using Energetic Ions. National Library of Medicine.
Nkuissi H.J.T, Konan F.K., Hartiti B. and Ndjaka J.M. 2019. Toxic Materials Used in Thin Film Photovoltaics and Their Impacts on Environment. Intechopen.
Wanga, F. Zhua, N., Lia T. and Hong-Chao Zhanga, B. 2014. Material and Energy Efficiency Analysis of Low Pressure Chemical Vapor Deposition of TiO2 Film. Science Direct.
Fthenakis V.M. and Moskowitz P.D. Thin-film Photovoltaic Cells: Health and Environmental Issues in their Manufacture, Use and Disposal. U.S. Department of Energy.