Reforging the Solar Photovoltaic Supply Chain

Executive Summary

Much of the manufacturing base of the global solar supply chain is rooted in the Xinjiang Uyghur Autonomous Region. ^{Laura T. Murphy and Nyrola Elima, In Broad Daylight: Uyghur Forced Labour in Global Solar Supply Chains, Sheffield Hallam University, May 2021, https://www.shu.ac.uk/helena-kennedy-centre-international-justice/research-and-projects/all-projects/in-broad-daylight.}The Xinjiang region’s vast metallurgical-grade silicon smelters and solar-grade polysilicon plants contain ~12% and ~42% of global metallurgical-grade silicon production and solar-grade polysilicon factory capacity, respectively.^{Heidari, Seyed M., and Annick Anctil. “Country-Specific Carbon Footprint and Cumulative Energy Demand of Metallurgical Grade Silicon Production for Silicon Photovoltaics.” Resources, Conservation and Recycling 180 (May 1, 2022): 106171. https://doi.org/10.1016/j.resc..., International Energy Agency, Solar PV Global Supply Chains: An IEA Special Report, July 2022, https://www.iea.org/reports/solar-pv-global-supply-chains.}These facilities have entangled solar PV manufacturing with Chinese government repression of minoritized peoples through forced labor, authoritarianism, and environmental injustice.^{Seaver Wang, Juzel Lloyd, and Guido Núñez-Mujica, Sins of a Solar Empire: An Industry Imperative to Address Unethical Solar Photovoltaic Manufacturing in Xinjiang, The Breakthrough Institute, November 2022, https://thebreakthrough.org/issues/energy/sins-of-a-solar-empire..}

In the coming years, Chinese firms plan to continue expanding solar manufacturing capacity in the Xinjiang region,^{Vincent Shaw and Max Hall, “Xinte Wants to Add Another 200,000 Tons of Polysilicon Capacity,” Chinese PV Industry Brief, pv magazine, March 15, 2022, https://www.pv-magazine.com/20... 15/chinese-pv-industry-brief-xinte-wants-to-add-another-200000-tons-of-polysilicon-capacity/}while also developing new clean tech industrial capacity such as lithium mines, graphite mines, and electric vehicle battery factories. ^{Laura Murphy, Kendyl Salcito, Yalcun Uluyol, Mia Rabkin, et al., Driving Force: Automotive Supply Chains and Forced Labor in the Uyghur Region, Sheffield Hallam University, December 2022, https://www.shu.ac.uk/helena-kennedy-centre-international-justice/research-and-projects/all-projects/driving-force.}Without strong action to exclude Xinjiang-based manufacturers from clean energy technology markets, the global clean energy sector risks normalizing state-sponsored oppression of Uyghur, Kazakh, and Kyrgyz peoples in Xinjiang as acceptable, turning the region into an environmental sacrifice zone.

At the same time, China’s continued dominance in the solar supply chain presents financial risks for the solar industry. Overconcentration of manufacturing capacity in a single country and region increases the solar sector’s vulnerability to supply chain disruptions from unpredictable economic, political, accident-related events.^{IEA, Solar PV Global Supply Chains.}A focused effort to shift away from Xinjiang-based solar commodity production could help ensure a more reliable supply of solar PV commodities, while also promoting greater technological innovation in manufacturing and better shielding the industry from reputational and regulatory risks.

Our previous Sins of a Solar Empire report highlighted the scale of forced labor risks and environmental injustice within the Xinjiang-based solar manufacturing sector, and called upon solar industry actors, policymakers, and climate advocates to redouble efforts to aggressively shift solar PV manufacturing away from the Xinjiang region.^{Seaver Wang, Juzel Lloyd, and Guido Núñez-Mujica, Sins of a Solar Empire.}This memo outlines specific steps and recommendations for each sector of the solar manufacturing industry to accelerate diversification of the global solar supply chain and promote greater social and environmental responsibility.

Main recommendations

• Governments should deploy coordinated, targeted industrial policy to incentivize the expansion of new solar manufacturing capacity beyond China.

• The public sector should support the continued operation of existing solar manufacturing capacity around the world that contributes critically to solar PV supply chain diversification.

• Solar industry actors should adopt social and environmental standards that avoid sourcing of unethical solar commodities on the basis of excluding problematic companies, not individual shipments or batches of product, from upstream manufacturing chains.

• Governments should pass laws that ban the importation of any products manufactured wholly or in part by companies implicated in forced labor, coordinate with one another to standardize import tracing and certification requirements, and advocate outspokenly for fair treatment of labor according to international conventions in multilateral forums.

• Policymakers should make solar PV manufacturing and deployment incentives contingent upon compliance with a low-carbon standard to promote more environmentally responsible solar PV production.

• Industry and the public sector should work jointly to expand research and development of current and alternative solar technologies that could help strand existing unethical production and accelerate efforts to diversify global solar PV supply chains.

The biggest challenge for diversification will be a race against time to expand new manufacturing capacity throughout the industry’s various sectors while meeting future projected demand for solar PV products. However, the solar sector can overcome these challenges and diversify manufacturing chains through a unified international effort to increase transparency, technical collaboration, and factory investments. Swift action to implement the recommendations outlined in this memo can position the solar energy industry for long-term success while advancing a more hopeful and just clean energy transition.

1. Diversify solar manufacturing by establishing new, alternative, responsible manufacturing capacity globally

Approach

Efforts to establish responsible alternative solar PV suppliers will need to consider the main factors that affect the feasibility and costs of building solar manufacturing industry projects:

Low-cost, cleaner electricity

An affordable electricity supply is a key factor in metallurgical-grade silicon, solar-grade polysilicon, and ingot/wafer production. The Chinese solar manufacturing industry has thrived thanks to factories located in the coal-rich Xinjiang province combined with subsidized electricity.^{Seaver Wang, Juzel Lloyd, and Guido Núñez-Mujica, Sins of a Solar Empire.}Any competitor will have to drive down its energy costs and do so with cleaner sources.

Investment costs

For new manufacturing capacity to attain sufficient scale, projects will require promising investment environments that alleviate considerable upfront fixed capital costs. Public policy can create appropriate incentives to help attract such industrial plants. At the same time, such incentives possess limited ability to overcome considerable differences in capital, land, labor, and construction costs that may make certain contexts unsuitable for new projects.

Industry expertise

Technical expertise in developing large-scale solar-grade polysilicon, solar PV cell, and especially monocrystalline silicon ingot/wafer manufacturing plants has become increasingly limited outside of China. Such limitations pose significant challenges for developing new manufacturing capacity elsewhere in the world, but broadly developing related know-how will be a prerequisite for achieving a more global solar supply chain. Nor is specialized knowledge entirely absent outside of Chinese companies—supply chain reorganization efforts can leverage recent technical expertise in Korea, Germany, Malaysia, the United States, Japan, Taiwan, and elsewhere.

Manufacturing costs

New manufacturing plants ultimately will need to offer solar PV commodities for sale at competitive prices, necessitating affordable manufacturing costs. The largest cost components of solar PV manufacturing are generally energy costs, labor costs, and the depreciation of high-cost plant infrastructure assets. Manufacturers can achieve lower costs by taking advantage of economies of scale, integrating plants and processes, and siting facilities in regions with favorable labor and energy costs. Targeted public policy support can also help mitigate production costs.

Recommendations

Establish solar manufacturing tax credits

Public sector incentives can encourage producers to establish new manufacturing output by offsetting significant additional costs that would prevent firms from investing in new capacity under existing market conditions. Policymakers can introduce manufacturing tax credits for each unit of a given solar PV commodity (metallurgical-grade silicon, polysilicon, wafer, cell, module, or thin-film module). The Inflation Reduction Act’s Advanced Manufacturing Production Credit is an example of such a policy, offering tax credits for solar components produced in the US.^{H.R. 5376, 117th Congress (2021-2022), Inflation Reduction Act of 2022, August 16, 2022, http://www.congress.gov/bill/117th-congress/house-bill/5376.}

Extend public support for new factory development

Governments can provide financing support for the construction of new solar facilities, which often involves significant upfront investment in plant infrastructure. Such support can take a number of forms, including public loan guarantees, subsidized equipment purchases, public-private cost sharing, or investment tax credits to incentivize capital investment in the construction of new factories. Non-financial public policy support can include public agency cooperation to facilitate new factory siting, public programs to train a skilled technical workforce, and targeted recruitment of technical experts and project managers with valuable sectoral experience.

Subsidize electricity for manufacturing plants

Solar PV technology serves a crucial role in the suite of clean energy solutions, providing large public benefits. Given the high electricity intensity of metallurgical-grade silicon and solar-grade polysilicon production, electricity prices significantly influence the operational considerations of solar PV manufacturers. As such, if electricity costs pose a major obstacle to expansion of solar PV manufacturing, the public sector should act to mitigate this key factor. At the same time, Xinjiang-based solar manufacturers’ use of cheap, highly-subsidized coal electricity emphasizes the importance of simultaneously considering the carbon intensity and environmental impacts of consumed electricity.

The IEA’s recent Special Report on Solar PV Global Supply Chains suggested that, on balance, Scandinavia, the United States, and Canada were potentially the most competitive locations for siting new, cleaner MGS, polysilicon, and ingot/wafer production,^{IEA, Solar PV Global Supply Chains.}taking into account both average electricity carbon intensity and industrial electricity costs. Even in these regions, subsidized power could help incentivize added solar PV industry activity, while projects in countries with pricier power might require targeted support as a prerequisite to development. To claim these incentives, manufacturers should meet requirements to adhere to a low life-cycle carbon footprint standard, to ensure the use of low-carbon electricity for manufacturing solar PV products. Policymakers should design subsidy schemes that phase down over time before ending altogether, to reduce the likelihood that such policies discourage long-term innovation and efficiency improvements.

Diversify the geographical production of input raw materials

While most discussions around the solar supply chain focus on the sequence of manufacturing steps between solar-grade polysilicon production and the assembly of the finished module, such conversations have neglected the need to similarly prioritize other key inputs. These notably include quartz rock, metallurgical-grade silicon, aluminum, and solar PV cover glass—inputs with significant Xinjiang-based production for which diversification is a priority^{Seaver Wang, Juzel Lloyd, and Guido Núñez-Mujica, Sins of a Solar Empire.}—and high-purity quartz, a highly limited commodity used for monocrystalline silicon ingot production.^{Jacob Fromer and Cissy Zhou. South China Morning Post. “Xinjiang’s Solar Industry Needs a Rare Form of Quartz — and the US Is Selling,” October 26, 2021. https://www.scmp.com/news/chin....}Such key raw materials for solar PV manufacturing should also benefit from public policy support similar to the measures articulated above.

Invest in R&D to drive innovation in solar manufacturing

Redoubled research and development efforts will be key to matching the low manufacturing costs, good product quality, and significant efficiencies of scale of the Chinese solar PV manufacturing sector. Increased R&D spending should be directed towards establishing effective quality control, improving the energy efficiency and environmental sustainability of industrial processes, and promoting large-scale, commercially-competitive manufacturing of alternative solar technologies (see Section 3). Such innovations can help drive further technological changes in solar PV markets and establish competitive advantages for new manufacturers relative to low-cost incumbent producers in China.

Demonstrate demand for responsible solar manufacturing with public incentives

Public policies can help signal advance large-scale demand for socially and environmentally-responsible solar PV products. For instance, governments can implement bonus tax credits for solar project developers that source solar modules that meet high social and environmental standards. Governments themselves can create demand for ethical solar manufacturing by undertaking public-sector procurement of responsibly-sourced solar commodities for government projects, such as public power projects or small-scale rooftop PV installations for government buildings. Such initiatives will depend upon the promulgation of clear, verifiable industry-wide social and environmental standards for solar PV commodities (see Section 2).

Protect existing solar manufacturing capacity and expertise

Governments should place a high priority on maintaining all existing manufacturing capacity outside of China. Some of the only large-scale solar manufacturing plants operating outside of China are currently located in Germany, Korea, Japan, Malaysia, and Taiwan. Their longevity is increasingly threatened by low-cost competition from Chinese firms, coupled with other factors like high energy prices in Germany.^{Kurmayer, Nikolaus J. “Germany’s Wounded Chemical Industry Causes Concern in Berlin.” www.euractiv.com, November 3, 2022. https://www.euractiv.com/secti....}These firms represent important repositories of industry technical know-how, and will form a key part of the foundation for any efforts to expand solar PV manufacturing internationally. Preserving these surviving plants will also reduce the scale of the challenge of reorganizing the global solar PV supply chain.

What Level of Investment Is Required to Establish New Manufacturing at Scale?

Projecting the magnitude of necessary investment required to diversify the solar supply chain depends on the scale of the target. The following calculations estimate total capital investment required to meet 30%, 50% and 100% of non-Chinese global solar PV demand in 2030 with new manufacturing capacity operating outside of China. The wide range of diversification targets accounts for a possibility that in practice, particularly indifferent customers overseas may continue to purchase Chinese-produced solar PV products out of cost convenience, while some governments may seek to preserve favorable trade and economic relations with China by refraining from imposition of import restrictions on ethical grounds.

This simple calculation considered the costs of recently constructed and announced solar manufacturing facilities inside and outside of China. We assumed that in 2030, the needed annual manufacturing capacity outside of China at each step in the solar PV supply chain (polysilicon, ingot, cell and module) is 565 GW/yr, accounting for a factory utilization factor of 80%. The lower-bound investment limit assumed the lower value, in millions of US dollars (2022) per gigawatt per year, of either 1.3 times the lowest China-based total capital cost estimate, or the lowest non-China total capital cost estimate. For the upper-bound limit, we used an aggressive higher value of either quadruple the highest China-based total capital cost estimate or the highest non-China total capital cost estimate, all accounting for exchange rates and inflation since the original factory announcement.

Overall, the solar manufacturing industry would need to make significant investments to expand manufacturing outside of China, with the largest capital expenditures expected to be in wafer and cell production. Currently, these components are made almost entirely in China,^{Paul Basore and David Feldman, Solar Photovoltaics: Supply Chain Deep Dive Assessment, U.S. Department of Energy, February 24, 2022,https://www.energy.gov/sites/d... Solar%20Energy%20Supply%20Chain%20Report%20-%20Final.pdf.}thereby increasing the absolute costs of diversifying these supply chain steps.

This calculation does not explicitly consider other links of the solar PV supply chain such as quartz rock, aluminum, or solar PV cover glass whose current market structure and existing distribution of factory capacity are less clear. Given human rights concerns in Xinjiang, industry actors and policymakers should also place emphasis on utilizing quartz deposits outside of China for polysilicon production, preferably in contexts with proven social and environmental accountability for mining operations. Given the large investments required, many private sector companies may be reluctant to move forward with supply chain diversification efforts given current market dynamics and potential risks. In this case, it may be more practical for governments to offer innovative loan and incentive programs that support the private sector in taking the lead to expand manufacturing capacity.

2. Establish Strong Standards for Solar Commodity Markets and International Trade

Approach

A call for solar sector companies to enact strong social and environmental standards in response to ethical solar supply chain concerns is simple in principle. However, formulating and standardizing industry-wide standards is by no means easy in practice. Furthermore, corporations that seek to ensure the supply chains from which they purchase do not include forced labor can expect to encounter a number of challenges. One of the main challenges will involve obstacles that prevent verification of the authenticity of labor, environmental, and supplier contract documentation, such as difficulties enforcing transparency from Chinese companies operating in Xinjiang.

The resources required to obtain trustworthy and reliable information come with inherent costs for industry actors, which may in turn drive higher prices for solar equipment and solar developments. Industry information-sharing and supporting government policies can help offset such information costs. In any case, some of the costs associated with increased supply chain transparency are necessary to eliminate risks of human rights abuse within the solar manufacturing industry.

Recommendations

Avoid suppliers complicit in exploiting forced labor

Solar sector companies should end supply contracts with and avoid purchasing products from corporations confirmed to be partaking in either or both of these roles: 1) operating any manufacturing facilities that are located in the Xinjiang Uyghur Autonomous Region and/or utilize forced labor. 2) directly sourcing any commodities or products from companies in the first group and refusing to end such supplier arrangements.

Require rigorous supply chain transparency

Governments should implement strong tracing and documentation requirements to restrict the importation of solar PV products that may, with a reasonable probability, contain content from manufacturers operating factories in Xinjiang. Such restrictions should be expanded as needed to screen commodities from other regions or companies should evidence of labor exploitation emerge. Governments should exercise proactive international collaboration to standardize transparency requirements and thus facilitate compliance processes. Meanwhile, solar PV developers and solar equipment firms should work with suppliers to establish full upstream supply chain tracing that extends to the raw materials used to produce every component of the final cell or module.

Enact and enforce general fair labor standards in international trade

Generally, governments should seek to improve global labor conditions by adopting and upholding fair labor standards such as those outlined in the fundamental and priority conventions of the International Labor Organization,^{International Labor Organization. “Conventions and Recommendations.” Accessed January 6, 2023. https://www.ilo.org/global/sta....}and hold peer governments accountable by supporting representations and complaints against employers and member states that fail to respect such principles.

However, private sector actors—solar equipment manufacturers, solar project developers, and renewable energy companies—also carry a pivotal responsibility to hold themselves and business partners accountable for good labor practices. Many other industries have adopted conventions to improve labor conditions and strengthen worker’s rights. For instance, the Responsible Mining Index Framework (RMI)^{Responsible Mining Foundation. “Responsible Mining Index Framework 2022” September 2021. https://www.responsibleminingf....}provides specific, actionable guidelines for companies to mitigate the possibility of forced labor within their supply chains. International auditing firms have also developed forced labor risk tools that utilize companies’ operational information to measure potential exposure to forced labor risks using supply chain audits.

Well-designed private systems for promoting supply chain responsibility should include strong transparency and complaint-based mechanisms, giving workers added stakeholder power and improving the ability of third-party actors to hold employers accountable.^{Marx, Axel, and Jan Wouters. “Redesigning Enforcement in Private Labour Regulation: Will It Work?” International Labour Review 155, no. 3 (September 2016): 435–59. https://doi.org/10.1111/j.1564-913X.2015.00040.x.}Symbolic industry commitments to fair labor such as the Solar Energy Industry Association’s Solar Industry Forced Labor Prevention Pledge^{Solar Energy Industries Association. “Solar Industry Forced Labor Prevention Pledge.” Accessed January 12, 2023. https://www.seia.org/sites/def....}could evolve into a more structured initiative that includes requirements for verifiable transparency and complaint protocols.

Deny market access to firms that exploit forced labor

Governments should enact bans on the importation of goods from any companies complicit in forced labor practices, thereby sending a clear and distinct message of zero tolerance for forced labor within the supply chain. Policymakers could also enforce other penalties like investment bans on companies abroad that persist in their exploitation of forced labor, whether directly or by sourcing components.

Develop public and industry guidance to accelerate supply chain diversification

Government should provide support for industry supply chain reorganization efforts, coordinating with a network of partner countries to help match solar sector companies with equipment and raw material producers that meet standards for social and environmental responsibility. Partner nations could, for instance, include Korea, Malaysia, India, Canada, Germany, which possess established solar manufacturing industries. These and similar resources and assistance can help aid companies that discover they were unknowingly sourcing components used with forced labor in correcting their supply chain practices. In parallel with this effort, companies should pool industry resources and share knowledge across the industry to help ensure a supply chain insulated from forced labor.

Establish low-carbon standards for solar PV products to promote environmental responsibility

Governments should enforce a low-carbon standard for manufacturing operations so that the benefits of clean technologies are not diluted by the use of carbon-intensive energy production.^{“Ultra Low-Carbon Solar Alliance,” accessed October 21, 2022, https://ultralowcarbonsolar.or....}This could include tax credits for imported products that do meet the low-carbon standard or carbon taxes on those that fail to do so. Leniency should be exercised for international development assistance (IDA) eligible countries seeking to increase their solar manufacturing capacity that possess much less fiscal ability to do so while observing low-carbon standards.

3. Accelerate Research, Development, and Deployment of Alternative Solar Technologies

Approach

In the last decade, the solar PV manufacturing chain has coalesced around specific technologies that have emerged as the most low-cost, scalable means of solar PV module production—solar-grade polysilicon production via the Siemens process, followed by monocrystalline silicon ingot pulling using the Czochralski method, followed by monocrystalline passivated emitter rear contact (PERC) solar cell production.^{Basore and Feldman, Solar Photovoltaics.}

Competing approaches and technologies, such as fluidized bed reactor polysilicon production, thin-film solar cells, or concentrating solar power have not been able to match the increasing cost-competitiveness of mono-Si PERC solar PV, and have consequently lost market share over time. However, some of these alternatives offer unique sustainability and manufacturing advantages, and could play a supporting role in efforts to diversify global solar supply chains. At a minimum, added investment into alternative solar technologies could drive annual production equivalent to perhaps several GW/yr, marginally facilitating the challenge of supply chain diversification. Yet the possibility also exists that new investment into alternative technologies could produce fresh breakthroughs that help them better match mono-PERC solar PV in cost-competitiveness, thus dramatically altering the dynamics of solar PV markets writ large.

Recommendations

Increase investment in cleaner solar manufacturing technologies and techniques

Given the ever-rapid pace of technical advances in solar PV manufacturing, efforts to diversify the solar PV supply chain could also benefit from investments in diverse manufacturing approaches for producing solar commodities. Such techniques may offer better energy efficiency, reduced environmental impacts, cost improvements, and other advantages that could benefit the industry over the long term.

Some may argue that existing solar PV manufacturing approaches have already converged on a highly successful model, rendering investment in alternative techniques meaningless. However, the solar manufacturing sector has long been characterized by costly, risky investments in fixed infrastructure that may rapidly face obsolescence. Indeed, nothing might strand unethical solar PV manufacturing in Xinjiang faster than industry developments that leave these factories technically out-of-date. As manufacturing processes and solar cell design continue to advance, new manufacturing entrants must consider a broad suite of future technological possibilities, recognizing that novel approaches certainly involve considerable investments and risks of their own.

• The fluidized bed reactor approach (FBR) suspends small polysilicon seed particles in a reactor amidst an ascending flow of silane gas and hydrogen, with gaseous silicon accumulating on the growing seed particles. This method allows near-continuous production of solar-grade polysilicon production, with new seed particles and gasses entering the reactor while grown particles and process gasses exit. Compared to the leading Siemens method, the whole-process FBR approach requires only around half the electricity per unit of polysilicon produced, and also yields fewer potentially harmful chemical byproducts.^{Bye, Gøran, and Bruno Ceccaroli. “Solar Grade Silicon: Technology Status and Industrial Trends.” Solar Energy Materials and Solar Cells 130 (November 1, 2014): 634–46. https://doi.org/10.1016/j.solm....}

  While viewed as a distant runner-up to the dominant Siemens technology, the FBR process has enjoyed a resurgence of interest in the wake of large capacity expansions at Chinese manufacturer GCL-Poly^{Vincent Shaw. pv magazine International. “Chinese PV Industry Brief: Canadian Solar Starts Production of Independently Developed Inverters.” Accessed January 6, 2023. https://www.pv-magazine.com/2022/10/25/chinese-pv-industry-brief-canadian-solar-starts-production-of-independently-developed-inverters/.}and an imminent restart of production at REC Silicon’s US-based factory,^{Max Hall. pv magazine International. “REC Silicon to Restart Poly Production at Moses Lake in 2023.” Accessed January 6, 2023.}demonstrating its continued market potential. The FBR approach does introduce some quality control concerns, while the technology itself remains proprietary to a small number of producers.^{Bye, Gøran, and Bruno Ceccaroli, 2014.}Nevertheless, the process not only represents a noteworthy alternative production method with operational and sustainability advantages, but also could help drive further advances in FBR techniques more generally, with useful applications in sectors like low-carbon chemicals^{Bellan, Selvan, Nobuyuki Gokon, Koji Matsubara, Hyun Seok Cho, and Tatsuya Kodama. “Numerical and Experimental Study on Granular Flow and Heat Transfer Characteristics of Directly-Irradiated Fluidized Bed Reactor for Solar Gasification.” International Journal of Hydrogen Energy 43, no. 34 (August 23, 2018): 16443–57. https://doi.org/10.1016/j.ijhydene.2018.06.033.}or end-of-life solar module recycling.^{Wang, Shuai, and Yansong Shen. “Particle-Scale Modelling of the Pyrolysis of End-of-Life Solar Panel Particles in Fluidized Bed Reactors.” Resources, Conservation and Recycling 183 (August 1, 2022): 106378. https://doi.org/10.1016/j.resconrec.2022.106378.}

• Upgraded metallurgical-grade (UMG) silicon is another alternative route to solar-grade polysilicon production, using various metallurgical refining methods as opposed to a chemical vapor deposition approach to achieve high-purity poly-Si. UMG technologies may offer advantages in terms of lower capital expenditure and improved energy efficiency even relative to FBR methods per unit of polysilicon produced.^{Bye, Gøran, and Bruno Ceccaroli, 2014.}However, this method currently yields polysilicon with a higher-than-desired concentration of electron charge carriers, requiring co-blending with other polysilicon feedstock or further chemical tuning to avoid negative impacts on product quality. UMG approaches are also not currently employed at commercial scale, and thus do not represent a near-term supply chain solution.

Explore the full potential of alternative solar technologies

• Thin-film Cadmium Telluride solar modules utilize an entirely different supply chain separate from crystalline silicon-based solar PV technologies. Cadmium telluride (CdTe) solar modules produced by First Solar are the most common thin-film solar technology on the market currently,^{Basore and Feldman, Solar Photovoltaics.}followed by a small quantity of copper indium gallium selenide (CIGS) thin-film solar module production. A major advantage of thin-film solar manufacturing is that First Solar’s CdTe production process features high vertical integration, with nearly all manufacturing processes co-located at the same factory site. As such, investments into new thin-film manufacturing facilities may allow more rapid scaling of new solar manufacturing capacity than may be possible for crystalline silicon-based solar. Thin film market share is 4% as of 2020,^{Basore and Feldman, Solar Photovoltaics.}although the sector itself has continued growing. Levelized cost for utility scale thin-film falls in a range of $0.028 - $0.037/kWh while that of conventional, crystalline utility scale solar stands at $0.03 - $0.041/kWh as of 2021.Lazard.com. “Levelized Cost Of Energy, Levelized Cost Of Storage, and Levelized Cost Of Hydrogen.” Accessed January 6, 2023. http://www.lazard.com/perspect....^{Lazard.com. “Levelized Cost Of Energy, Levelized Cost Of Storage, and Levelized Cost Of Hydrogen.” Accessed January 6, 2023. http://www.lazard.com/perspect...}But while thin-film solar modules boast cheaper equipment costs, they currently operate at lower efficiencies, are not as easily physically adaptable to rooftop mounts due to their heavier weight, and are subject to shorter module lifetimes. Scaling up cadmium and tellurium supply chains to accommodate an increase in thin-film solar manufacturing may also present challenges.

• Thin-film silicon-based solar, such as ultrathin monocrystalline silicon solar wafer designs, show notable potential for competitive solar cell efficiency relative to conventional silicon-based solar PV modules while significantly facilitating the manufacturing process and reducing wafer costs. For instance, the firm NexWafe has developed a gas-to-wafer manufacturing process that greatly reduces energy and material usage compared to traditional wafer manufacturing.^{Uma Gupta. pv magazine International. “Reliance Industries to Invest $29 Million in Nexwafe.” Accessed January 6, 2023. https://www.pv-magazine.com/2021/10/13/reliance-industries-to-invest-29-million-in-nexwafe/.}Thin-film silicon-based solar in general requires less pure silicon to produce each cell and can still be used for a variety of applications, but may differ from conventional crystalline silicon cells in efficiency and operational lifetime. Overall, significant further research, development, and investment will be required to determine whether these technologies can compete with existing commercial solar PV equipment at scale.

• Concentrating solar power (CSP) has generated interest among policymakers and clean energy researchers for years, but has consistently confronted technical challenges and high costs that have stalled large-scale adoption. Tower-based CSP designs also pose some ecological risks, killing substantial numbers of local birds and insects that fly through the highly concentrated sunlight reflected by onsite mirrors.^{Mulvaney, Dustin. Solar Power: Innovation, Sustainability, and Environmental Justice. Oakland, California: University of California Press, 2019.}At the same time, CSP technology is not polysilicon-based, and therefore does not rely upon existing crystalline silicon solar PV supply chains. Additionally, CSP offers some tantalizing theoretical advantages in terms of its higher capacity factor and potential for integrated molten salt energy storage. Trough-based and enclosed trough-based CSP concepts also reduce risks to wildlife while offering durability advantages. The cost of CSP has decreased by 50% in the past decade due to increased efficiency—and despite more widespread incorporation of thermal storage systems.^{Office of Energy Efficiency & Renewable Energy, U.S. Department of Energy, “Solar Futures Study”, September 2021. https://www.energy.gov/sites/default/files/2021-09/Solar%20Futures%20Study.pdf.}Current levelized cost stands at a range of $0.126 -$0.156 per kilowatt-hour as of 2021.^{Lazard.com. “Levelized Cost Of Energy, Levelized Cost Of Storage, and Levelized Cost Of Hydrogen.” Accessed January 6, 2023. http://www.lazard.com/perspect....}Additional investment into R&D and demonstration projects may be warranted.

• Perovskites are crystalline molecular compounds whose structures enable unique optical and electrical properties that are quite useful for solar cells.^{Office of Energy Efficiency & Renewable Energy, U.S. Department of Energy, “Perovskite Solar Cells.” Accessed January 6, 2023. https://www.energy.gov/eere/so...,Mohan, Minu. “Perovskite Photovoltaics.” In Perovskite Photovoltaics, 447–80. Elsevier, 2018. https://doi.org/10.1016/B978-0-12-812915-9.00014-9.}They have received a lot of attention thus far due to their high power conversion rates and high affordability.^{Wang, Rui, Muhammad Mujahid, Yu Duan, Zhao Kui Wang, Jingjing Xue, and Yang Yang. “A Review of Perovskites Solar Cell Stability.” Advanced Functional Materials 29, no. 47 (November 2019): 1808843. https://doi.org/10.1002/adfm.2...}However, degradation and material instability have prevented perovskites from being scaled commercially. Continuous research and development support will be needed to provide the breakthroughs needed to get perovskites onto the PV market. Research and development efforts might be directed in particular towards improving perovskite/silicon tandem solar cell design and establishing low-cost manufacturing methods, as this is a more likely near-term commercialization pathway for perovskite solar products.

Conclusion

The global solar supply chain can shift away from Chinese manufacturers who serve as the dominant suppliers of solar PV equipment today. However, this shift can only occur if policymakers and industry actors adopt a firm stance against unethical solar manufacturing in Xinjiang and take an active hand in rapidly expanding alternative, socially and environmentally responsible solar commodity production elsewhere.

Policymakers and customers that care about supply chain justice^{Thea Riofrancos, “Shifting Mining from the Global South Misses the Point of Climate Justice,” Foreign Policy, February 7, 2022, https://foreignpolicy.com/2022/02/07/renewable-energy-transition-critical- minerals-mining-onshoring-lithium-evs-climate-justice/.}will need to prioritize investments in responsibly-sourced solar products as the new, global standard and thereby contest the market share of Chinese manufacturers as much as possible. Companies will need to devote major effort to trace products and materials throughout their supply chain, with the support of government partners and pooled industry knowledge. Policymakers and industry actors will need to make large-scale public and private investments into building a better solar manufacturing sector. Finally, governments should enact stringent laws against the importation of products that carry high forced labor risks, to compel greater overall industry compliance with social and environmental standards.

By pursuing the policy recommendations outlined in this memo, solar sector companies and governments can help oppose crimes against humanity in Xinjiang, while helping the world advance towards a clean energy future that does not inflict unjust wrongdoing upon workers and communities.