Solar PV as an Energy System and a Material System
Solar photovoltaics are a major renewable energy technology. PV systems convert sunlight into electricity and can reduce greenhouse-gas emissions when solar electricity displaces electricity from fossil fuels. PV deployment therefore plays an important role in many energy-transition pathways.
PV systems also require raw materials, refining, manufacturing, global supply chains, land, labor, supporting infrastructure, maintenance, waste management, and end-of-life planning. Solar panels do not burn fuel during operation, but PV systems still have life-cycle impacts. Those impacts begin with extraction and continue through processing, manufacturing, transportation, installation, operation, decommissioning, recycling, and disposal.
Central Question: How should the goals and scope of a life cycle assessment shape the ethical evaluation of solar photovoltaics?
Lesson 5 at a Glance
Lesson Element | Focus |
|---|---|
| Duration | Two weeks |
| Technology | Solar photovoltaic cells, modules, arrays, and complete systems |
| Methodological center | Life Cycle Assessment: goal and scope, functional unit, system boundary, impact categories, assumptions, and harmonization |
| Material context | Critical minerals, material flows, manufacturing, supply-chain concentration, toxicity, and end of life |
| Ethics method | Ethics Matrix C: embedded choices in boundaries, categories, assumptions, proxies, exclusions, and priorities |
| Applied cases | PV payback; PV materials, toxicity, and pollution; PV procurement and supply chains |
| Final task | A goals-and-scope framework and approximately 1,000-word ethical analysis supported by Matrix C |
Why PV Requires Life-Cycle Thinking
PV systems can appear clean when analysis begins and ends with electricity generation. Point-of-use analysis does not capture the full system. Life-cycle thinking asks where materials come from, how they are processed, which energy sources power manufacturing, what emissions and wastes are produced, who experiences mining and refining impacts, how modules perform over time, and what happens when equipment is damaged or reaches the end of its useful life.
Life-Cycle Stage | Examples | Ethical Questions |
|---|---|---|
| Extraction and refining | Silicon feedstocks, silver, copper, aluminum, glass inputs, cadmium, tellurium, and other materials | Which communities, workers, and ecosystems bear extraction and processing impacts? |
| Manufacturing | Wafers, cells, modules, inverters, wiring, frames, racking, and supporting equipment | Which electricity mix, labor conditions, chemicals, emissions, and controls shape production? |
| Transport and installation | Freight, land preparation, structures, foundations, grid interconnection, and construction | Which infrastructure and land-use effects belong within the system boundary? |
| Operation and maintenance | Electricity generation, degradation, cleaning, monitoring, repairs, and replacements | How do lifetime, solar resource, performance, and replacement assumptions change the result? |
| End of life | Reuse, refurbishment, recycling, recovery, transport, disposal, and residual waste | Who is responsible for collection, financing, recovery, and remaining harms? |
Critical Minerals and Material Flows
PV supply chains include silicon, silver, copper, aluminum, glass, polymers, cadmium, tellurium, indium, gallium, and other inputs depending on module type and system design. Some materials are abundant but energy-intensive to process. Other materials raise concerns about scarcity, refining concentration, environmental harm, labor conditions, toxicity, trade dependence, or competition with other energy technologies.
Critical-Minerals Question | Why It Matters |
|---|---|
| Availability and competing demand | Rapid deployment can increase pressure on materials used across multiple clean-energy technologies. |
| Mining and refining location | Environmental and social burdens may be concentrated far from the place where electricity is consumed. |
| Supply-chain concentration | A small number of countries or firms may control important manufacturing and refining stages. |
| Labor and occupational health | Workers may face exposure, coercion, weak protections, or limited ability to challenge unsafe conditions. |
| Community consent and distribution | Local communities may bear land, water, pollution, or infrastructure burdens without proportionate benefits. |
| Recycling and circularity | Recovery can reduce virgin-material demand, but technical recyclability does not guarantee actual collection or recovery. |
| Transparency and traceability | Weak visibility across tiers makes environmental and labor claims difficult to verify. |
Lesson Structure
Page | Primary Focus | Questions to Carry Forward |
|---|---|---|
| Part 1: Introduction to Solar Photovoltaics | Basic PV science, system components, technology types, performance, and material implications | What counts as the PV system? Which technical choices change material and life-cycle results? |
| Part 2: Life Cycle Assessment of Photovoltaic Systems | Goal and scope, functional unit, boundaries, impact categories, harmonization, data, and assumptions | What can this LCA legitimately claim, and what remains outside its boundary? |
| Case 1: Does PV Pay Back? | Financial, energy, greenhouse-gas, and industry-level payback | Which boundary, baseline, comparison case, and time horizon define “payback”? |
| Case 2: PV Materials, Toxicity, and Pollution | Hazard, exposure, risk, manufacturing impacts, trace metals, waste, and end of life | Which substances, pathways, populations, and life-cycle stages are included or omitted? |
| Case 3: Where Should I Buy My PV? | Procurement, global supply chains, quality, labor, critical minerals, transparency, installers, and end-of-life responsibility | Which values and evidence should shape purchasing decisions? |
Lesson Objectives
By the end of Lesson 5, you should be able to:
- explain the basic science behind photovoltaic systems;
- describe PV systems as both energy systems and material systems;
- identify the major stages in the PV life cycle;
- distinguish Life Cycle Assessment from Life Cycle Cost Assessment;
- define an appropriate goal and scope for a PV LCA;
- distinguish cradle-to-grave, cradle-to-gate, gate-to-gate, and cradle-to-cradle boundaries;
- explain why functional units, comparison cases, and harmonization matter;
- identify ethical issues involving critical minerals, mining, manufacturing, toxics, supply chains, labor, and end-of-life management;
- explain how LCA assumptions and exclusions shape ethical conclusions; and
- apply Ethics Matrix C to the goals and scope of a possible PV life cycle assessment.
Key Concepts
PV and Materials | LCA Methods | Ethics and Decision Context |
|---|---|---|
| PV cell, module, array, and system | Goal and scope | Critical minerals |
| Crystalline-silicon and thin-film PV | Functional unit | Material flows |
| Efficiency, degradation, and lifetime | System boundary | Toxicity, exposure, and risk |
| Balance-of-system components | Cradle-to-grave / gate / cradle | Supply-chain concentration |
| Energy and greenhouse-gas payback | Impact categories and inventory data | Transparency and traceability |
| Manufacturing electricity mix | Harmonization and sensitivity | Procurement ethics |
| Recycling and end of life | Uncertainty and limitations | Embedded assumptions and exclusions |
Assigned Readings and Review Materials
Complete the assigned readings during the week indicated. The readings define the evidence base for the lesson and should be used directly in your Yellowdig discussion and goals-and-scope analysis.
Week 1 Readings
Reading | Assigned Portion | Use in the Lesson |
|---|---|---|
| 1. Stucki, Matthias, Michael Götz, Mariska de Wild-Scholten, and Rolf Frischknecht. 2024. Environmental Life Cycle Assessment of Electricity from PV Systems: 2023 Data Update. IEA Photovoltaic Power Systems Programme, Task 12. | Read the complete 22-slide deck. | LCA framework and current PV environmental results. Use it to identify current life-cycle results, system assumptions, technology differences, and comparative patterns. |
| 2. Smith, Brittany L., Ashok Sekar, Heather Mirletz, Garvin Heath, and Robert Margolis. 2024. An Updated Life Cycle Assessment of Utility-Scale Solar Photovoltaic Systems Installed in the United States. NREL/TP-7A40-87372. | Read the Executive Summary; Section 2.1; Sections 2.4.1-2.4.3; Sections 4 and 5; and Section 5.3. | Applied U.S. utility-scale PV LCA. Use it to examine goal and scope, U.S.-specific assumptions, life-cycle greenhouse-gas results, uncertainty, and interpretation. |
Week 2 Readings
Reading | Assigned Portion | Use in the Lesson |
|---|---|---|
| 3. National Renewable Energy Laboratory. 2026. Solar Photovoltaic Module Facts and Trends. | Read the full fact sheet. | Module materials, trace metals, manufacturing trends, module design, and end-of-life context. Use it especially with Case 2. |
| 4. International Energy Agency. 2022. Solar PV Global Supply Chains. Paris: IEA. | Read the Executive Summary and the sections on the major manufacturing stages. | Supply-chain concentration and procurement context. Use it to trace polysilicon, wafer, cell, and module manufacturing and to evaluate concentration across the supply chain. |
| 5. International Energy Agency. 2025. Global Critical Minerals Outlook 2025 — Executive Summary | Read the Executive Summary. | Current critical-minerals conditions and outlook. Use it to place PV material demand within wider supply, concentration, investment, recycling, and geopolitical trends. |
How the Readings Connect to the Lesson Pages
Lesson Page or Case | Most Directly Relevant Readings |
|---|---|
| Part 2: Life Cycle Assessment of PV Systems | Stucki et al. (2024) and Smith et al. (2024) |
| Case 1: Does PV Pay Back? | Stucki et al. (2024) and Smith et al. (2024) |
| Case 2: PV Materials, Toxicity, and Pollution | NREL (2026), with supporting LCA results from Stucki et al. (2024) and Smith et al. (2024) |
| Case 3: Where Should I Buy My PV? | IEA (2022), IEA (2025), and NREL (2026) |
What to Look for in the Readings
LCA or Ethics Choice | Questions to Ask |
|---|---|
| Goal of the assessment | What decision is the study intended to support, and who is the intended audience? |
| Functional unit | What service is being compared, and does the unit permit a fair comparison? |
| System boundary | Which stages and supporting systems are inside or outside the analysis? |
| Comparison case | What baseline or alternative is being used, and is the comparison compatible? |
| Impact categories | Which environmental or social effects are quantified, and which remain outside the result? |
| Data and geography | Where and when were the data collected, and how well do they match the case? |
| Uncertainty and sensitivity | Which assumptions most strongly influence the results? |
| Stakeholder visibility | Whose benefits, burdens, exposures, or responsibilities become visible through the chosen scope? |
Ethics Matrix C: Embedded Choices in LCA Design
Ethics Matrix C is the primary ethics method for this lesson. Matrix C helps identify how technical analysis embeds values through problem definitions, boundaries, categories, assumptions, proxies, exclusions, comparison criteria, and priorities.
Embedded Choice | PV LCA Example | Ethical Consequence |
|---|---|---|
| Problem definition | Defining the question as greenhouse-gas reduction rather than total environmental or social performance | Other impacts may become secondary or disappear from the analysis. |
| System boundary | Ending the study at the factory gate or excluding recycling infrastructure | Upstream or downstream stakeholders and burdens may be omitted. |
| Functional unit | Comparing one module rather than one kilowatt-hour of delivered electricity | Differences in efficiency, lifetime, and output may be distorted. |
| Impact categories | Reporting carbon but excluding toxicity, water stress, labor, or land use | A technology may appear preferable because unmeasured impacts remain invisible. |
| Data and proxy choices | Using generic global data for a specific manufacturing location | Local conditions and vulnerable populations may be poorly represented. |
| Allocation and recycling credits | Assigning recovered-material benefits to the original product or a future product | The apparent environmental performance changes with the allocation rule. |
| Comparison and weighting | Prioritizing cost, emissions, supply security, or domestic content differently | Different values can support different procurement conclusions. |
Assignment Focus
You will not conduct a complete technical LCA. A complete LCA requires more data, modeling, and technical detail than this assignment allows. Your task is to define and ethically evaluate the goals and scope of a possible PV life cycle assessment.
Your Framework Should Establish | Your Analysis Should Explain |
|---|---|
| The PV case or decision being evaluated | Why the selected goal and scope fit the decision |
| The question the LCA is intended to answer | How the functional unit and comparison case shape the result |
| An appropriate functional unit | Which stakeholders and values become visible |
| The system boundary | Which stakeholders or impacts may remain outside the boundary |
| The life-cycle stages included | How assumptions and exclusions influence interpretation |
| Any excluded stages and the reasons for exclusion | How Matrix C changes or strengthens the proposed framework |
| The most relevant impact categories | What evidence would be needed for a defensible assessment |
| Likely data sources and uncertainties | What the proposed LCA could and could not legitimately claim |
Two-Week Work Plan
Week | Complete | Produce or Submit |
|---|---|---|
| Week 1 | Read Part 1, Part 2, and Case 1. Complete Stucki et al. (2024) and the assigned sections of Smith et al. (2024). Participate in Yellowdig. | Develop a draft goals-and-scope framework for a possible PV LCA. |
| Week 2 | Read Cases 2 and 3. Complete NREL (2026), IEA (2022), and the IEA (2025) Executive Summary. Continue Yellowdig participation. | Complete Ethics Matrix C and submit the completed matrix with an approximately 1,000-word LCA goals-and-scope analysis in Canvas. |
Guiding Questions
Questions 1-6 | Questions 7-12 |
|---|---|
| 1. What counts as the PV system being evaluated? | 7. Which impact categories belong inside the assessment? |
| 2. Where should the life-cycle boundary begin and end? | 8. Which impacts or stakeholders may be left outside the assessment? |
| 3. What functional unit should be used? | 9. Who benefits from the selected boundary? |
| 4. What comparison case is appropriate? | 10. Who may be made invisible by the selected boundary? |
| 5. Which life-cycle stages matter most for the ethical question? | 11. Which assumptions are most uncertain or consequential? |
| 6. Which critical minerals or material inputs deserve special attention? | 12. How would a different goal, scope, or comparison change the ethical interpretation of PV? |
Questions?
Use Canvas email for questions about readings, assignment expectations, or your specific Matrix C analysis. You are also encouraged to help classmates clarify course concepts through Yellowdig when appropriate.