The manufacture of solar panels necessary for such a huge increase in solar power production will require an enormous surge in the mining of raw materials. There are myriad problems that exist with the mining of silicon, silver, aluminum, and copper needed to make solar panels. Can governments and companies ensure that workers in the solar supply chain benefit from safe, just, and well-compensated livelihoods—and that the communities most affected are involved as active collaborators, treated with respect and dignity?
(To understand how those raw materials are put together into electricity-producing panels, check out
How Are Solar Panels Made.)
According to the US Department of Energy (DOE), about 12% of all silicon metal produced worldwide (also known as “metallurgical-grade silicon” or MGS) is turned into polysilicon for solar panel production. China produces about 70% of the world’s MGS and
77% of the world’s polysilicon. Converting silicon to polysilicon requires very high temperatures, and in China it’s coal that largely fuels these plants. Xinjiang—a region in China of abundant coal and low electricity prices—produces
45% of the world’s polysilicon.
Reports indicate that some Xinjiang polysilicon plants have employed forced labor of
Uyghurs, an intensely persecuted Muslim ethnic minority. In June 2021, a
US Withhold Release Order prevented imports containing silicon from Hoshine Silicon Industry Co. Ltd and its subsidiaries from entering the US until importing companies could prove they were not made with forced labor. The December 2021
Uyghur Forced Labor Prevention Act expanded the mandate that all US companies importing silicon from Xinjiang confirm supply chains free of forced labor.
A Gleeson Quarries silica mine in Ireland. Photo credit: CDE Global/Flickr.
Ten percent of the world’s
silver is used for solar panels just today, and that brings its own share of problems to the supply chain. By 2050, in a 100% renewable energy scenario that assumes current solar technology and current recycling rates, solar power’s demand for silver could be more than
50% of the world's reserves.
Silver mining, based mainly in Mexico, China, Peru, Chile, Australia, Russia, and Poland, can sometimes cause heavy metal contamination and community displacement. In Guatemala, the Indigenous
Xinka community collected more than
85,000 signatures calling on Pan American Silver to avoid restarting its dormant operations due to water contamination, failure to justly consult the community, and potential involvement in threats directed at nonviolent protesters. In La Libertad, Peru, a 17-year-old mine
stopped operating in 2012 after five emergency declarations of high levels of metal contamination in the Moche River.
While silicon and silver are the materials for which solar represents a substantial slice of the market, it’s critical to ensure sustainable, ethical sourcing of the other materials, even if only a fraction of global usage. For example, solar panels use a small amount of aluminum, which is sourced from bauxite found near the Earth’s surface. Mining it requires
lots of land, often encroaching on Indigenous land, as in Australia, where 28% of the world’s bauxite is produced, and smallholder farmland, as in Guinea, where
22% of it is produced. China produces 22% of the world’s bauxite, and processes 56% of global bauxite into aluminum via a very energy-intensive process.
A former bauxite mine in Hungary. Photo credit: Wikimedia Commons.
Copper has similar land use challenges as aluminum. According to United States Geological Survey, 27% of copper production occurs in Chile, 10% in Peru, 8% in China, and 8% in the Democratic Republic of Congo. In a 100% renewable energy by 2050 scenario,
copper demand for solar projectsmay almost triple, according to the International Energy Agency (IEA).
The Institute for Human Rights and Business reports that of
the top 300 undeveloped copper ore reserves in the world, 47% are located on or in Indigenous lands, 65% are in high water risk areas, and 65% are in or near biodiversity conservation areas.
The world’s largest open-pit copper mine is in Chile. Photo credit: Martyn Unsworth/Imaggeo.egu.eu.
There are three parts of a solar panel that need to be manufactured: the silicon wafer, the solar cell, and the photovoltaic module. Very little of this is manufactured domestically, representing big opportunities for new and pioneering US innovation.
The wafer is the thin metal slice that is turned into a solar cell, and 97% of them are produced in China. A decade ago, the US was producing enough silicon wafers to supply 80% of domestic demand. As of February 2022, there was
no domestic production of wafers due to far lower prices abroad and Chinese tariffs, but a few US sites have announced
plans to come online in the next several years.
Boron and phosphorous are added to wafers during the manufacturing process. The wafers are then wired with silver, which turns them into solar cells capable of transforming captured sunlight into electricity. While the first US crystalline silicon solar cell plants have announced plans to open in the next few years,
no cells are produced
in the US today; most are made in South Korea, Malaysia, China, and Vietnam.
A solar PV panel or “module” is made by assembling an array of solar cells, ranging from
36 to 144 cells, on top of a strong plastic polymer back sheet with a sheet of tempered glass added on top. More than three-quarters of PV modules are made in China. It currently costs 30-40% more to manufacture a solar panel in the US. There are about 20 US-owned,
US-based solar module and shingle manufacturers, with 10 based in California, and others based in New York, Ohio, Texas, Indiana, New Jersey, and Arizona.
As described above, there are many challenges associated with the materials mining and manufacturing processes needed to make solar panels. But effective policy and technology solutions can ensure that we continue to increase solar power supply and move towards responsible, sustainable solar supply chains, but this movement requires succinct legislation which has not been yet formulated.
Here are four strategies (among many others) that governments and industry can employ to reduce the environmental, social, and energy challenges of solar panel production.
- Ensure ethical supply chains. When sourcing raw materials, governments and solar companies can commit to ensuring that mining and refining companies obtain the free, prior, and informed consent (FPIC) of the communities in which they operate. Companies can participate in regulation and evaluation standards such as the Silicon Valley Toxics Coalition Solar Scorecard.
- Decarbonize manufacturing processes. Fortunately, new innovations are already reducing the electricity required to make polysilicon. For example, a new polysilicon production process called the “fluidized bed reactor” could use 80-90% less energy than the more widely used Siemens process. Additionally, choosing to produce solar panels in places with cleaner energy sources—along with strategic policy to encourage such siting—can go a long way to reduce the carbon intensityof the process. The recent passage of the Inflation Reduction Act with its tax credits for solar panel-producing companies, and the Biden administration’s 2022 invocation of the Defense Production Act to spur on a domestic solar panel manufacturing industry, are two examples of strategic policy that can accelerate the decarbonization of this industry.
- Improve panel, material, and process efficiency. Improving the energy generation efficiency of solar panels means that customers can generate more electricity from fewer panels—which would be easier on the wallet and would require less raw materials in the solar supply chain. While solar panels can last for decades, research and innovation into further extending the lifetime of solar panels can also help customers avoid needing to replace them. Designing panels and solar business models to support easy, affordable, and accessible refurbishment can also extend panel lifetimes. Plus, technological innovation can reduce the amount of raw materials needed in solar panels. For example, engineers have lowered the amount of silver needed in each solar cell by 67% from 2007 to 2016, and it is expected to drop further.
- Increase recycling and reuse. Here lies the biggest “silver” lining in the solar panel life cycle story. The two big challenges—raw material sourcing issues and the accumulation of solar panel waste—can help solve one another. Higher numbers of retired solar panels means more recyclable raw materials will be available to supplement increasingly scarce, costly, and international supply chains. Because solar panel reuse and recycling research is still nascent, there are many opportunities for new initiatives and companies to make a big impact. Policy and investment in a new era of circular renewable energy technologies will ensure that the transition to clean power worldwide is as responsible, sustainable, and circular as possible.
And what happens at a solar panel’s
end-of-life? Today, we’re installing 50-60 million panels per year, which will generate a
million metric tons of solar panel waste when the panels are eventually retired. By 2030,
experts estimate we could be installing over 250 million panels per year. This is huge news for accelerating the clean energy transition. It also raises the stakes for ensuring sustainable materials sourcing and end-of-life management. Where will the panels go 20-30 years later when they reach the end of their lifespan? Are there opportunities to achieve a circular solar panel supply chain?
The US solar industry was valued at $33 billion in 2021, employed more than 230,000 people, and continued to grow in power capacity at an average rate of 33 percent per year.
Solar panels generated
almost 4 percent of electricity in the US in 2021, up from less than 1 percent in 2015. In some places that number is much higher; for example,
17% of California’s electricity generation came from solar in 2021. Almost half of all new energy capacity added to the US grid in 2021 came from solar. Even more encouraging, by 2030, the solar industry aims to generate
nearly a third of US electricity.
With so many solar panels planned for the coming years, you might be wondering: what exactly are solar panels and how are they made?
There are two types of solar technology for electricity generation. The most common are
photovoltaic (PV) panels or modules, which use the sun’s light to make electricity. Another technology,
concentrating solar power (CSP), uses the sun’s heat instead.
The most common type of PV panel is made using crystalline-silicon (c-SI). That technology accounts for
84% of US solar panels, according to the US Department of Energy. Other types include cadmium telluride, copper indium gallium (di)selenide panels, and thin-film amorphous silicon. Because c-SI panels compose most of the US and global market, I focus on them in this blog.
By weight, the typical crystalline silicon solar panel is made of about 76% glass, 10% plastic polymer, 8% aluminum, 5% silicon, 1% copper, and less than 0.1% silver and other metals, according to the Institute for Sustainable Futures. Graphic: UCS.
Building a crystalline silicon solar panel is a bit like building a sand castle, because
silicon comes from sand! Beach sand is silicon dioxide, aka silica. (If beach patrol put that on a warning sign, I bet no one would step foot on the beach!). Silicon, in the form of silicon dioxide sand and gravel, is the second most abundant element on Earth, next to oxygen.
Before it’s used in a solar panel, silicon dioxide
must be turned into pure “metallurgical grade silicon” (MGS). This process uses a lot of energy: producing 1 kilogram of metallurgical grade silicon requires
14-16 kWh of power, which is roughly equivalent to using your
home oven for seven hours. Still, over their lifetimes, solar panels emit
25 times less carbon dioxide equivalent per kilowatt hour than coal-powered electricity.
Chemistry break! The recipe for cooking up metallurgical grade silicon is
Add 1 part silicon dioxide (gravel) and 2 parts carbon (sourced from coal, charcoal, or wood chips) to an electric arc furnace
Crank up the heat to 2200 degrees Celsius (this is a third of the temperature of the sun!!)
Ta-da! You’re left with 99% pure silicon and carbon monoxide (that’s from the carbon we added, bonded to the oxygen we removed from the silicon dioxide)
But solar panels are perfectionists; they demand silicon to be close to 100% purity. To achieve that, we need to upgrade the silicon into an even more pure polysilicon metal using a process that involves dangerous and poisonous hydrochloric acid and hydrogen gas. (Fun fact: about
12% of the world’s silicon production is currently processed into polysilicon for solar panels.)
Source:
UCS
After adding the acid and gas, we are left with chunks of polysilicon metal, which are typically melted down again in a roughly 5-meter-long cylindrical mold.
Boron is added to give the metal a positive electric charge on one side. The hot, melty silicon cools and forms a single crystal (“monocrystalline”) structure as a cylindrical ingot. Ingots are any material cast into a rectangular shape, like bars of gold.
(Another process is used to make “polycrystalline” silicon wafers, in which multiple crystals form. This process tends to lead to less efficient panels but can reduce the cost of wafers.)
Next, a wire saw cuts the pure metal blocks of polysilicon into paper-thin, typically 7-inch by 7-inch flat slices called wafers.
Source:
UCS
The wafers are heated in an oven and a thin layer of phosphorous is added, giving one side (the opposite of the positive boron side) a negative charge. Next, an
anti-reflective coating is added to the wafers because without it these shiny disks reflect sunlight—and we want them to absorb it instead. At this stage, the wafers are now capable of absorbing the sun’s energy and
converting it into electrons. Now we need to add silver metal conductors so those electrons can get turned into an electrical current that devices can use!
Silver—the most conductive element in the world—intercepts the electrons in the silicon wafers and turns them into current. The silicon wafers now form a conductive solar cell. Each solar panel, usually containing 60 or 72 cells, uses about 20 grams of silver—a fraction of the panel’s weight but
about 10% of its total cost.
Copper metal conductors and wiring connect the solar cells together into one big solar panel, giving it the classic matrix appearance. Copper is a good electrical conductor and very malleable, making it a great material for forming the wiring that moves the current through the panel.
Multiply the above by about 60 million for the US alone,
each year.
And then speed it up because we need solar to play an ever-growing role in achieving our clean energy and climate goals.
See:
https://blog.ucsusa.org/charlie-hoffs/mining-raw-materials-for-solar-panels-problems-and-solutions/
See: See:
https://blog.ucsusa.org/charlie-hoffs/how-are-solar-panels-made/
Will clean energy be achieved without the destroying our planet in the process? This appears the issue we are hurtling toward. And no individual, corporation or country should be exempt from honest manufacture and recycling. Crony capitalism must be avoided at all costs.
Hartmann352