Solar Futures STUDY SEPTEMBER 2021 Disclaimer This work was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, nor any of their contractors, subcontractors or their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or any third party’s use or the results of such use of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof or its contractors or subcontractors. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof, its contractors or subcontractors. i Solar Futures Study Letter from the Director The Solar Futures Study is the result of extensive analysis and modeling conducted by the National Renewable Energy Laboratory to envision a decarbonized grid and solar’s role in it. It’s designed to guide and inspire the next decade of solar innovation by helping us answer questions like: How fast does solar need to increase capacity and to what level? How would such a large amount of solar energy impact the grid, the economy, and the solar industry? What technical advances are needed? How do we ensure access for all Americans? Since the Department of Energy announced the SunShot Initiative in 2011, we’ve been working to answer these big, economy-wide questions through a series of vision studies—SunShot Vision Study (2012), On the Path to SunShot (2016), and now the Solar Futures Study (2021). Just as we found from the first study, technology development and cost declines continue to play a critical role in the future of solar. In fact, continued cost reductions in solar (as well as wind, batteries and other renewable technologies) are essential to making decarbonization affordable. In addition, we can no longer look at solar technologies in isolation—we must look at how they interact with the full energy system. For example, technologies like power electronics and storage have the potential to reshape how energy is produced and consumed, enabling renewable microgrids that can keep the lights on after a major storm or shift energy consumption to maximize cost savings. As solar deployment grows, engagement with local communities becomes increasingly important. Solar deployment, especially on the distribution system, can bring jobs, savings on electricity bills and enhanced energy resilience. It is critical that these benefits are distributed equitably, and that communities have a voice in the where solar projects are located and how the benefits are allocated. The past decade was transformative for solar, with rapid cost reductions and subsequent increases in deployment. It is now possible to envision—and chart a path toward—a future where solar provides 40% of the nation’s electricity by 2035. This growth is necessary to limit the impacts of climate change, and our work to realize this vision could not be more urgent. There are many challenges to address, requiring diverse skill sets and approaches and extensive collaboration. If you are not already part of the solar community, we hope you will be inspired to join us in this work. Thank you for taking the time to read our vision for solar’s bright future! Becca Jones-Albertus Director, U.S. Department of Energy Solar Energy Technologies Office ii Solar Futures Study List of Acronyms 5G fifth-generation AC alternating current AEO Annual Energy Outlook AI artificial intelligence ANM active network management ARPA-E Advanced Research Projects Agency–Energy ATB Annual Technology Baseline BA balancing area BIPV building-integrated PV BoM bill of materials BOS balance of systems CAISO California Independent System Operator CapEx capital expenditures CARE California Alternate Rates for Energy CC combined cycle CCS carbon capture and sequestration CCUS carbon capture, utilization, and sequestration CDR carbon dioxide removal CdTe cadmium telluride CE circular economy c-Si crystalline silicon CSP concentrating solar power CT combustion turbine DC direct current Decarb Decarbonization Decarb+E Decarbonization with Electrification DER distributed energy resource DERMS DER management systems DfC design for circularity dGen Distributed Generation (model) DMS distribution management systems DOE U.S. Department of Energy DPV distributed photovoltaics DR demand response DSO distribution system operator DUPV distributed utility-scale PV EFS Electrification Futures Study EOL end of life ERCOT Electric Reliability Council of Texas EV electric vehicle EVA ethylene-vinyl acetate FCEV fuel cell electric vehicle FERC Federal Energy Regulatory Commission FFR fast-frequency response FPV floating PV iii Solar Futures Study FRCC Florida Reliability Coordinating Council GDP gross domestic product GFM grid-forming inverter GHG greenhouse gas GIS geographic information systems Gt gigaton(s) GW gigawatt(s) HDV heavy-duty vehicle HHV higher heating value HVAC heating, ventilation, and air conditioning IAS integrated agricultural systems IBC interdigitated back contact IBR inverter-based resource IEA International Energy Agency ILR inverter-loading ratio IRP integrated resource planning IT information technology ITRPV International Technology Roadmap for Photovoltaics LCA life cycle analysis LCOE levelized cost of energy LCOS levelized cost of storage LDV light-duty vehicle Li-ion lithium-ion LMI low- and medium-income MDV medium-duty vehicle MISO Midcontinent Independent System Operator ML machine learning MLPE module-level power electronics Mt million metric ton(s) NG natural gas NOx nitrogen oxides NREL National Renewable Energy Laboratory NWS non-wires solutions NYISO New York Independent System Operator O&M operations and maintenance OT operational technology PERC passivated emitter and rear cell PFR primary frequency response PII permitting, inspection, and interconnection PM particulate matter POLO polycrystalline silicon on oxide PRAS Probabilistic Resource Adequacy Suite PSH pumped-storage hydropower PSS product service system PV photovoltaic(s) PV ICE PV in Circular Economy tool iv Solar Futures Study PWh petawatt-hour Quad quadrillion Btus R&D research and development RA resource adequacy RCRA Resource Conservation and Recovery Act RE renewable energy RE-CT renewable energy combustion turbine ReEDS Regional Energy Deployment System SCADA supervisory control and data acquisition SCC social cost of carbon sCO2 supercritical carbon dioxide SEIA Solar Energy Industries Association SETO Solar Energy Technologies Office SHJ silicon heterojunction SIPH solar industrial process heat SO2 sulfur dioxide SPP Southwest Power Pool SVTC Silicon Valley Toxics Coalition T&D transmission and distribution TCLP toxicity characteristic leaching procedure TES thermal energy storage TLS transport layer security TOPCon tunnel oxide passivated contact TRP Technical Review Panel TSO transmission system operator UPV utility-scale photovoltaics USMCA United States–Mexico–Canada Agreement VACAR Virginia-Carolinas VRE variable renewable energy WAC watts alternating current WDC watts direct current WH water heating WHEJAC White House Environmental Justice Advisory Council WRF Weather Research and Forecasting v Solar Futures Study EXECUTIVE SUMMARY Executive Summary Dramatic improvements to solar technologies and other clean energy technologies have enabled recent rapid growth in deployment and are providing cost-effective options for decarbonizing the U.S. electric grid. The Solar Futures Study explores the role of solar in decarbonizing the grid. Through state-of-the-art modeling, the study envisions deep grid decarbonization by 2035, as driven by a required emissions-reduction target. It also explores how electrification could enable a low-carbon grid to extend decarbonization to the broader energy system (the electric grid plus all direct fuel use in buildings, transportation, and industry) through 2050. The Solar Futures Study uses a suite of detailed power-sector models to develop and evaluate three core scenarios. The “Reference” scenario outlines a business-as-usual future, which includes existing state and federal clean energy policies but lacks a comprehensive effort to decarbonize the grid. The “Decarbonization (Decarb)” scenario assumes policies drive a 95% reduction (from 2005 levels) in the grid’s carbon dioxide emissions by 2035 and a 100% reduction by 2050. This scenario assumes more aggressive cost-reduction projections than the Reference scenario for solar as well as other renewable and energy storage technologies, but it uses standard future projections for electricity demand. The “Decarbonization with Electrification (Decarb+E)” scenario goes further by including large-scale electrification of end uses. The study also analyzes the potential for solar to contribute to a future with more complete decarbonization of the U.S. energy system by 2050, although this analysis is simplified in comparison to the grid-decarbonization analysis and thus entails greater uncertainty. Even under the Reference scenario, installed solar capacity increases by nearly a factor of 7 by 2050, and grid emissions