Keeping pace with PV growth

Every new terawatt of PV has a physical footprint. It requires tons of silicon and glass, kilometers of copper cable, and much smaller – but potentially more critical – quantities of silver, indium and tin. Those material flows have become enormous as global PV capacity has tripled from 1 TW in 2022 to today’s 3 TW and continues to move toward several tens of terawatts.

How enormous depends on where solar deployment eventually ends up. Scenarios examined in a new IEA-PVPS analysis range from 29 TW to 75 TW of silicon-based PV by 2050, with 29 TW and 63 TW representing the study’s main low- and high-deployment pathways

Such growth raises an uncomfortable question: can material supply keep up? The answer is more interesting than a simple “yes” or “no.” Some materials could indeed come under considerable pressure, but PV technology is not standing still. Cells are becoming more efficient, wafers thinner, silver contacts narrower, and material substitution more widespread. At the same time, an enormous stock of materials is accumulating in PV systems that will eventually become available for recycling.

Future tech

“PV in 2050 will not look like PV today. PV material compositions will change in the race to make PV electricity even more cost effective and sustainable” said Rutger Schlatmann, chair of the European Technology and Innovation Platform (ETIP) PV.

Rather than assuming a fixed amount of material for every watt installed until 2050, researchers model a PV industry in continuous development. A key basis for this is the International Technology Roadmap for Photovoltaics (ITRPV), coordinated by German engineering industry association VDMA, which tracks expectations for the development of crystalline-silicon PV.

The roadmap looks at where the technology is heading with cell and module efficiencies, wafer thicknesses, metallization technologies, silver consumption, and the changing market shares of different cell architectures. The IEA-PVPS analysis incorporates these developments through 2035 and extends the trends toward 2050, while testing some of the largest uncertainties separately.

As the chart below shows, the mass of materials locked into operating PV systems grows dramatically in both the lower and higher deployment pathways. The systems may become more material-efficient, but that efficiency should aim to counter an installed fleet expanding into the tens of terawatts. And not every material follows the same trajectory.

Silver substitution

Silver is perhaps the clearest example of the industry’s ability to engineer its way out of a potential material constraint.

Silver is an excellent conductor and has long played a central role in silicon solar-cell metallization. But silver is also expensive and finite. Once annual PV manufacturing reaches terawatt scale, tiny amounts multiplied across billions of cells become substantial quantities. Under the central technology assumptions used in the IEA-PVPS analysis, PV could cumulatively consume up to 200,000 metric tons (MT) of silver between 2025 and 2050. That is equivalent to roughly 15% to 30% of today’s estimated global silver reserves.

“The amount of silver used per solar cell has been declining for years and the PV industry is in the process of switching to copper based ­metallization,” said Radovan Kopecek, co-founder and director of ISC Konstanz. Based on the trajectory depicted in the ITRPV, the IEA-PVPS study assumes that copper-based metallization technologies increase their combined market share from only 7% in 2024 to 74% by 2035. Copper screen printing still uses some silver, while copper plating can remove silver from the metallization altogether.

The effect is striking. When the IEA-PVPS researchers vary the future share of silver screen printing, cumulative silver demand to 2050 ranges from roughly 50,000 MT to 600,000 MT. The sensitivity analysis shows that technology choice has a stronger influence than the difference between the deployment scenarios themselves.

That makes silver less a story about an unavoidable shortage and more about the pace of an industrial transition. However, this transition leads directly to another question. If copper helps solve the silver problem, how much copper will the solar industry itself need?

System demands

A solar cell uses comparatively little copper. A solar power system is another matter. Between 2025 and 2050, PV could require a cumulative 145 million MT to 280 million MT of copper. Annual demand could reach 7 million MT to 15 million MT in the mid-2040s – equivalent to roughly 30% to 65% of current annual global mining production.

But copper metallization is not what drives those numbers upward. The additional copper needed for metallization remains small compared with the amounts already required elsewhere in a PV system. About three-quarters of the copper requirement comes from cables, with another 13% associated with inverters.

This is one of the more important findings for an industry accustomed to focusing on modules. Material efficiency in cables and ­inverters, and the availability of copper to the wider energy transition, become part of the solar scaling challenge. Substituting copper cables with less scarce aluminum cables, which are already being deployed for as cables for AC applications, could lessen this copper challenge.

Indium issues

The scenarios for indium look quite different. Indium tin oxide (ITO) is used as a transparent conductive layer in some of the cell architectures expected to play a larger role in future high-efficiency PV – including silicon heterojunction, some back contact architectures, and perovskite-silicon tandems.

Demand rises if those technologies expand as expected. Under the main scenarios, cumulative solar-sector demand reaches around 60,000 MT to 160,000 MT by 2050, while annual demand grows particularly rapidly toward 2040.

Here again, the headline number conceals the industry’s room to maneuver. Sensitivity analysis produces cumulative requirements ranging from only around 10,000 MT to as much as 300,000 MT, depending heavily on the share of ITO-containing technologies.

For context, the most recent authoritative indium reserve and resource estimate available to researchers is around 50,000 MT. That figure dates back to 2009 and should not be treated as a hard geological limit since reserves evolve with exploration, economics and extraction technology. Nevertheless, the comparison makes the direction of the challenge clear.

Under the IEA-PVPS study’s high-deployment assumptions, ITO-based technologies would need to remain below roughly 15% market share for solar PV demand alone to stay within that historical estimate, whereas under a low deployment scenario, market share could actually go up to 30%. And that leaves no indium for competing applications, such as digital screens, laptops and smartphones.

The implication is not that heterojunction or tandem PV cannot scale. Rather, large-scale deployment strengthens the case for reducing indium intensity, improving deposition efficiency and developing alternative transparent conductive materials. In other words, material availability becomes another parameter to optimize alongside efficiency, cost, and reliability.

Material recovery

Tin attracts far less attention than silver or copper, but its numbers are also worth watching. PV uses tin mainly in solder alloys for cell interconnections, with smaller quantities associated with ITO layers. Cumulative demand between 2025 and 2050 could reach around 1 million MT to 3 million MT.

Measured against current reserves, that becomes significant. The IEA-PVPS study calculates that cumulative PV demand alone could represent approximately 30% to 64% of estimated global tin reserves reported for 2024. However, solder compositions and interconnection technologies are evolving, meaning today’s tin intensity is not necessarily tomorrow’s.

The millions of metric tons of materials flowing into PV systems do not disappear once a module leaves the factory. They accumulate in power plants and rooftop systems around the world.

“Recycled materials from PV module waste could play a significant role in material supply for PV module production and other industries,”said PV recycling expert Keiichi Komoto.

For now, there is a timing problem. PV is growing so quickly that far more material is entering the system than leaving it. Modules installed during the current boom will typically remain in operation for decades.

Up to 2050, materials contained in decommissioned PV systems correspond to only around 15% to 20% of the cumulative demand for the materials analyzed.

And that is a theoretical maximum. The modeling assumes every retired system is collected, and 100% of its materials are recovered. Real recycling systems inevitably lose material through incomplete collection, contamination and processing.

Using the EU electronic waste targets as an example, an 85% collection target combined with an 80% recycling target translates into an effective recovery of around 68% of end-of-life module mass – already roughly one-third below the theoretical maximum.

Cara Libby, another leading PV recycling expert, said that “new data from PV recyclers demonstrate measurable advances in performance, including higher material recovery rates, improved process yields, and higher output purity.”

Recycling cannot supply the materials needed for the first phase of massive PV expansion. But that balance begins to shift as the installed fleet matures.

Silver is a particularly interesting example. Because the silver content of new cells is expected to decline sharply, silver recovered from older modules becomes large relative to the amount required for new ones. The study estimates that silver contained in end-of-life PV could theoretically cover around 30% to 45% of cumulative silver demand between 2025 and 2050.

Indium is almost the opposite story. ITO-containing technologies enter the market later, meaning much of their indium is still sitting inside operating modules in 2050. End-of-life flows provide only around 5% of cumulative indium demand over the study period.

Scaling challenges

There is an important difference between a challenge and a limit. Researcher Benjamin Sprecher, an expert on critical raw materials, notes the “energy transition will require substantially less material mining than the current fossil system.”

The material requirements of PV are not fixed. They have changed before and, according to the technology trajectories underlying the IEA-PVPS analysis, will continue to change. Silver provides perhaps the clearest demonstration in that a potential resource constraint can be reduced dramatically through lower material loading and substitution. Indium shows where similar innovation may be needed next. Copper highlights the importance of looking beyond modules to complete systems. And recycling represents an increasingly important secondary resource – even if the age profile of the rapidly growing PV fleet means its biggest contribution comes later.

The industry has several levers available: use less material per watt, substitute materials where supply could become constrained, improve manufacturing yields, develop technologies with material availability in mind, and recover more of what has already been put into service.

PV’s next few dozen terawatts will unquestionably require more materials. The task for the industry is to make sure that material demand grows much more slowly than the solar fleet itself. That is a substantial challenge, but the technology trends already under way suggest it is one the industry has the tools to address.

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