What Is The Carbon Footprint Of Producing Solar Panels?
Solar panels, also known as photovoltaic (PV) panels, are devices that convert sunlight into electricity. They have become an increasingly popular source of renewable energy due to benefits such as zero emissions during operation, reduced reliance on fossil fuels, and lower energy bills for consumers. The demand for solar panels has grown rapidly in recent years, with global production reaching 379 gigawatts in 2022, up from 115 gigawatts in 2016.
With the large-scale manufacturing and adoption of any technology comes implications for the environment. The carbon footprint refers to the total greenhouse gas emissions caused directly and indirectly by a product or activity throughout its lifecycle. Assessing the carbon footprint of solar panels allows us to understand their impact on climate change and identify areas for improvement.
What is a Carbon Footprint?
A carbon footprint is the total amount of greenhouse gases (GHGs) released into the atmosphere by a person, product, company, or event1. The main GHGs that contribute to carbon footprints are carbon dioxide (CO2) and methane (CH4). These gases trap heat in the atmosphere and contribute to climate change.
Some of the main sources of greenhouse gas emissions that contribute to carbon footprints include:
- Burning fossil fuels like coal, oil, and natural gas for electricity, heat, and transportation
- Agriculture and livestock farming
- Deforestation and land use changes
- Industrial processes and manufacturing
When assessing the impact of products like solar panels, it’s important to consider their full lifecycle carbon footprint. This includes emissions from raw material extraction, manufacturing, transportation, installation, use, and end-of-life disposal or recycling. Comparing the carbon footprint of solar panels versus traditional fossil fuel energy sources provides a more complete picture of their environmental impact.
Carbon Footprint of Solar Panel Production
The manufacturing of solar panels involves several energy-intensive processes that generate greenhouse gas emissions, contributing to the overall carbon footprint. The main stages of solar panel production that generate emissions are:
Silicon Purification – Producing the ultra-pure silicon wafers for solar cells requires high heat processes that consume significant electricity. This accounts for around 45% of a panel’s embodied carbon (LabPro Inc, 2023).
Panel Assembly – The assembly of solar cells into panels uses electricity for soldering, lamination, and other processes. Transportation between manufacturing facilities also contributes emissions.
Materials Sourcing – Producing the aluminum, glass, plastics, and other raw materials requires energy for extraction and refining. The country of origin and transportation distances impact emissions.
Variations in manufacturing techniques, energy sources, and supply chains cause differences in carbon footprints between panel products and companies. But solar power still compares favorably to fossil fuel electricity sources over the life cycle despite emissions during upfront production.
Silicon Production
Silicon production is a very energy intensive process and accounts for a significant portion of solar panel manufacturing emissions. Silicon must be heated to very high temperatures, over 2,000°C, to extract and purify it from silica. This requires large amounts of electricity, most of which comes from fossil fuels like coal and natural gas.
Studies show that silicon manufacturing accounts for around 6.0 kg CO2e/kg per silicon metal made [1]. It is estimated that 11 grams of silicon are needed per cell [2]. So for a typical 60-cell residential solar panel, silicon production would account for around 660 grams of CO2 equivalent emissions.
Companies are working to reduce emissions by improving energy efficiency in manufacturing and using more renewable electricity. For example, REC has reduced energy use per kg of silicon by over 40% since 2008. Wacker Chemie uses hydroelectric power for up to 60% of its silicon production. Continued progress in these areas can lower the carbon footprint of silicon substantially.
Panel Assembly
The assembly of solar panels involves multiple steps to combine all the components into a finished product. According to the Solar Energy Industries Association, the main steps include[1]:
- Assembling the photovoltaic cells into circuits and arrays
- Laminating the circuits between sheets of glass or plastic
- Adding aluminum frames and junction boxes
- Connecting wiring harnesses
- Mounting and encapsulating solar cell modules
- Performing quality inspections and testing
The energy used in assembly comes mainly from electricity to power manufacturing equipment and facilities. Sources of carbon emissions include the fossil fuels burned to generate this electricity. According to one analysis, panel assembly accounts for around 15% of a solar panel’s total manufacturing emissions[2]. Using renewable energy at manufacturing facilities could help reduce these emissions.
Transportation
Transporting raw materials and finished solar panels can contribute significantly to the carbon footprint through greenhouse gas emissions from planes, ships, trains, and trucks. Most solar panels are produced in China and other parts of Asia, requiring long distance shipping to markets in North America, Europe, and elsewhere. Shipping raw silicon and other heavy materials requires a lot of fuel.
Localized production and supply chains can greatly reduce transportation emissions associated with solar panels. Building manufacturing facilities closer to where the panels will be installed cuts down on shipping distances. Regional sourcing of raw materials also helps lower transportation mileage. Some companies are bringing production to Europe and North America to reduce transport footprint.
Innovations in packaging and transport efficiency are also lowering emissions from shipping finished panels. But localized production and regional/domestic supply chains provide the biggest opportunities for reducing the transportation carbon footprint of solar panel systems.
Installation & Maintenance
Installing and maintaining solar panels over their lifetime does result in some carbon emissions. Constructing large solar farms requires the use of heavy machinery and vehicles which burn fossil fuels. According to Solaris Renewables, the construction of a 10MW solar farm emits around 2,000 metric tons of CO2. However, these emissions are quickly offset once the solar farm becomes operational.
Maintenance activities over the 25+ year lifetime of solar panels also result in some emissions from transportation to the sites, and any electricity used for cleaning the panels. However, solar panels generally require very little maintenance. Routine cleaning, inverter replacements, and repairs make up less than 5% of the lifetime emissions of a solar panel, according to the National Renewable Energy Laboratory. With proper maintenance, solar panels can operate efficiently for decades.
Recycling & Disposal
Solar panels have a lifespan of around 30 years. At the end of their useful life, it’s important that solar panels are recycled properly to avoid sending toxic materials to landfills. Most solar panels contain hazardous materials like lead and cadmium that can contaminate soil and water if not disposed of correctly.
Recycling processes allow about 80-90% of a solar panel’s materials to be recovered and reused. The glass, aluminum, and silicon can all be extracted and made into new products. Some companies are also developing innovative ways to recycle more difficult components like the encapsulant and backsheet.[1]
Recycling solar panels reduces waste and environmental contamination. It also decreases the need for new raw material extraction. As more panels reach end-of-life in coming years, improving recycling processes and infrastructure will be an important sustainability goal for the solar industry.
Comparisons to Fossil Fuels
When examining the carbon footprint of solar panels versus fossil fuels, it’s important to look at the full lifecycle emissions rather than just the upfront manufacturing emissions. Although producing solar panels does involve greenhouse gas emissions, solar panels generate clean, renewable energy over their lifespan with very minimal emissions. Multiple studies have shown that the lifecycle carbon emissions from solar energy are far lower than fossil fuels.
According to a report by the World Resources Institute, solar panels have a carbon footprint that is up to 20 times lower than coal and 12 times lower than natural gas per unit of electricity generated over the panel’s lifetime. The emissions from manufacturing solar panels are typically paid back within 1-4 years of operation through the clean electricity they generate after that point. Fossil fuels, on the other hand, continue emitting greenhouse gases whenever they are burned for energy.
Transitioning to solar energy provides significant benefits in reducing yearly carbon emissions and meeting climate goals. One analysis found that generating 1 MWh of electricity from coal releases 960 kg of CO2, while solar panels only release 48 kg for the same energy output. As solar continues to expand its share of electricity generation, the avoided emissions compared to fossil fuels add up dramatically.
While fossil fuels are ultimately finite resources, solar panels can go on generating clean power for 25+ years. Expanding solar energy is a key long-term strategy to curb fossil fuel use, improve public health through reduced air pollution, and mitigate climate change.
Improvements & Innovations
There are several promising strategies to further reduce the carbon footprint of solar panel production and use in the future:
Improving manufacturing efficiency and minimizing waste can reduce emissions from production. Some solar companies are working to streamline processes and recycle more materials.[1]
Using more renewable energy in manufacturing facilities lowers fossil fuel use. Many panel producers are installing solar and wind to power operations.[2]
Developing higher efficiency panels means generating more electricity from the same footprint. Ongoing research aims to improve cell design and performance.[3]
Optimizing panel orientation, spacing and tracking systems can increase power yield per panel. Smart solar designs maximize sunlight capture.
New thinner, flexible panel technologies use less materials and enable creative mounting options.
Future projections estimate solar manufacturing emissions decreasing by up to 48% by 2050 as methods improve.[2] With these innovations, solar’s life cycle footprint could shrink dramatically.
