【PVPMC】Sandia-Stein-改善光伏组件和系统的技术手段

Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525. Technical Opportunities for Improving PV Modules and Systems – The Path to a 5 0 yr ModuleJoshua S. Stein Sandia National LaboratoriesSAND2019-14779 C What is the World Facing?§ IEA 2 0 1 9 World Energy Outlook Report – Everyone should read this.§ Current Policies Scenario – Too scary to talk about.§ Stated Policies Scenario – Emissions continue to rise well past 2 0 4 0 , Temp increases above 2 ° C§ Sustainable Development Scenario – Defines path to keep global temperature increases 1 8 0 million people displaced by floods worldwide). Far more will be affected indirectly.§ In 2 0 1 7 there were about 6 6 million displaced people in the world (1 7 million refugees in exile). How Do We Solve This Problem?§ There is not one solution, but solar PV is part of that solution.§ We must use one of the most innovative developments in human history….Money§ We need to make solar energy much less expensive than conventional generation sources.§ This would promote rapid adoption and allow for the economic early retirement of existing fossil power plants.§ Reducing LCOE is still needed.§ We need to lots of other things too: (electrify energy, biofuels, hydrogen, energy storage, energy efficiency, smart grids, etc… 3 SunShot 2 0 3 0 LCOE Targets for the US 4 27¢ 7¢ 6¢ 3¢051015202530 1 2 3 4 At 3¢/kWh solar would be among the lowest cost options for new generation— and below the variable costs of existing fuel plants.* LCOE progress and targets for utility-scale PV are for average U.S. climate and without the ITC or state/local incentives. The 2016 number is for a system with one-axis tracking. LCOE in cents/kWh (20 16 $)* SunShot Launch2010 2016 SunShot2020 SunShot2030 A Pathway to 3 Cents per kWh 52016Benchmark Improve Lifetime:30 to 50 yearsand Lower Degradation Rate:0.75% to 0.2% /yearLower Sustainable Module Price:$0.65 to $0.30/W Lower OM:$14 to $4/kW-yrLower Balance of System Hardware and Soft Costs$0.85 to $0.55/W SunShot 2030Goal100 MW(DC) One-Axis Tracking Systems With 1,860 kWh(AC)/kW(DC) First-Year Performance. Includes 5 Year MACRS. Cost of capital is 7% and inflation is 2.5%. Improve efficiency while decreasing cost Speed up installation and interconnection processes, reduce balance of system hardware costs (and improve module efficiency) Improve upon today’s best-in-class reliability in low-cost modules Employ automation and data analytics Why are 5 0 -yr Modules so Appealing? 6All scenarios assume: 7% cost of capital, 2.5% inflation, $0.85/W system cost, $4/kW-yr OM, 21% capacity factor$ 0 .0 0$ 0 .1 0$ 0 .2 0$ 0 .3 0 $ 0 .4 0$ 0 .5 0$ 0 .6 0 1 0 % 1 5 % 2 0 % 2 5 % 3 0 % 3 5 % 4 0 % 50 yr life0.2%/yr degAll curves represent 3¢/kWh LCOE in average U.S. climateModule Price ($/Wdc) 30 yr life0.2%/yr deg20 yr life 1%/yr deg Total-Area Module Efficiency50 yr module provides multiple opportunities to reach SunShot 2030 goals.• Ultra low cost modules (~$0.12/Wdc), lower efficiency (17%).• Low cost ($0.30/Wdc), high efficiency (25%)• Higher cost ($0.40/Wdc), very high efficiency (35%)Alternatives for 30 and 20 yr lifetimes require such low module prices that it is hard to believe they would ever achieve LCOE goals.50 yr module reduces future waste streams How to Increase Lifetimes and Decrease Degradation Rates? § Understand why modules degrade and fail.§ Choose designs and materials that minimize degradation and failures.Choices can be climate specific! 7Module fielded for 8 years in a hot dry climate. Cell cracks are severe. No signs of corrosion. Module fielded for 8 years in a tropical climate. Fewer cell cracks. Significant corrosion along busbars. Causes of Failure and Degradation § Damage during shipping or installation§ E.g., Cracked cells§ Optical degradation of materials§ UV degradation of encapsulants (“yellowing”, “browning”)§ Coatings wearout, scratches in topsheet§ Mechanical stress§ Wind, snow loading, hail  cracked cells, broken glass, bent frame§ Thermal cycling, Freeze-Thaw of water§ Chemical transport§ Water ingress, Acetic acid formation § Corrosion§ Failure of accessories§ J-box, cables, connectors 8 Prevent damage due to shipping and installation§ Mechanical analysis of stresses from vibration, shock, drop, etc. should be made for various packing solutions.§ Accelerometers installed on pallets – Data used to design package § Vertical vs. horizontal stacking§ Frame vs. frameless§ Effect of glass thickness§ Proper training and equipment needed for installers§ Field methods for checking that installation is damage free.§ Field imaging of modules (EL, PL, IR, IV, UVF) 9 Preventing Optical Degradation 1 0Encapsulant Additive Compounds• UV-stabilizers absorbers – absorb UV and dissipate as heat• Radical scavengers – antioxidants that remove peroxy, alkoxy, hydroxyl, and alkyl radicals• Crosslinking agents – curing agents that help to form covalent bonds between polymer molecules• Adhesion promoters – coupling agents (typically organosilanes) that help dissimilar materials to bond (e.g. glass, PV cells, encapsulants, backsheets). • Polymers degrade when exposed to UV radiation• Additives are used to absorb UV and thus protect polymer from degradation.• Very hard to measure additive concentration.• Current method relies on qualification testing (time consuming and does not have full coverage)• We need better controls and assurances on UV durability of polymers.• We need to know if/how various formulations affect durability and physical properties. Preventing degradation of Glass coatings§ We need to better understand how different coatings degrade.§ Accelerating ageing studies combined with detailed laboratory characterization is a good first step.§ Uncertain whether common coatings can last for more than a few years in the field. 1 1AS AR UncoatedDSM Study in Gobi DesertSEM cross-section of KhepriCoat Designing for Mechanical Stresses§ Multiple cell interconnect methods available§ Role of encapsulant physical properties§ Modulus vs. temperature (glass transition temp)§ Thickness§ Glass-backsheet vs. glass-glass designs 1 2 Strain gauges attached to PV cells within laminate FEA predicted cell strains @ 2400 Pa Module deflected using LoadSpot Wide Variety of PV Cell Interconnection Approaches 1 3Shingling, Conductive Adhesive (ECA) Soldered busbars MultiwireMetal Wrap Through,Conductive backsheetEach method differs in many ways that may affect durability and lifetime• Soldered Busbars have a long history.• Stress focused at cell edge• Different thermal expansion coefficients  solder bond fatigue. • Shingling and MWT use ECAs which are relatively new in PV.• ECAs can distribute stress but will they last for 50 years?• MWT is a flat design which minimizes local stress. • Not widely adopted We need more independent studies on how different cell interconnect methods respond to mechanical loading. Managing Chemical Transport within a PV Module§ Two general approaches to excapsulation:§ 1 . Allow some transport in and out of the module. § EVA + UV Acetic acid§ Permeable backsheet allows acetic acid to diffuse out§ Water can diffuse in at night and out during the day when module is hot§ 2 . Severely limit transport of water into module.§ Glass-glass modules with edge seals (e.g., desiccant filled polyisobutylene)§ Use encapsulant that does not produce acetic acid (e.g., polyolefin) § More studies of these two approaches are needed. 1 4H2O Failure of accessories – J-Box, Connectors, Cables 1 5Hot Connector(common) Really Hot Connector(not common) Cold Connector(common) • Connectors are a common source of failure, but are also field replaceable.• Compatible ≠ Compatible• Junction boxes provide housing for bypass diodes or power electronics• Pathway for moisture to enter module.• Adhesives must be reliable and durable.• Durability and abrasion resistance of cables (wind)Innovation: Investigations into alternative ways of interconnecting connecting modules, (e.g., wireless power transfer). Edge-mounted J-Box for glass-glass modules Summary and Conclusions§ There are significant economic and environmental benefits to extending the lifetime of PV systems. § There is a wide variety of module designs and materials used in PV modules.§ Each design choice impacts lifetime differently in different climates.§ More laboratory and field studies are needed to optimize module and system designs.§ Ensure no damage during shipping and installation§ Choose encapsulants and coatings that will withstand UV exposure, wind, dust, snow, etc.§ Design to minimize mechanical and thermomechanical strains§ More investigations comparing cell interconnection strategies are needed. § Glass-backsheet or glass-glass?) – Can any water transport be tolerated in a 5 0 yr module?§ Connectors, cables, and J-box are weak parts of the module. Alternatives?§ How to maintain or reduce costs while designing for longer lifetimes? 1 6 Thank you!Upcoming Events§ 2 0 2 0 PV Reliability Workshop, Lakewood, CO USA (February 2 5 -2 7 , 2 0 2 0 )§ PV Materials, Modules, and Systems Reliability§ SiliconPV2 0 2 0 BifiPV 2 0 2 0 Workshop, Hangzhou, China (March 3 0 -April 3 , 2 0 2 0 )§ 1 4 th PV Performance Modeling Workshop in Salt Lake City, UT USA (May 1 9 -2 0 , 2 0 2 0 ) § PV Measurement, Modeling, Monitoring and Integration§ IEEE PVSC, Calgary, Canada (June 1 4 -1 9 , 2 0 2 0 )§ bifiPV Workshop 2 0 2 0 in Walnut Creek, California, USA (July 2 0 2 0 )§ Bifacial cells, modules, systems, modeling, and characterization 1 7