General Framework

The "Industry Roadmap," was updated in December 2002, but continues to unify the vision, long-term strategies and goals for the PV industry through 2020. The vision goals are geared toward the electrical/energy consumer, competitive and environmentally friendly energy products, and services from a thriving U.S.-based solar electric power industry. The “U.S. DOE PV Technology Plan” (5-year plan) was revised, but remained in concert with the “Industry Roadmap” to help guide the national PV R&D activities to reflect the systems-driven approach.

The NCPV, an alliance of organizations, continued to serve as the focal point for the nation’s capabilities in PV. The R&D goals and strategies were formulated in concert with the “Industry Roadmap” and through the NCPV “Annual Operating Plan.The "Annual Operating Plan" was coordinated with the solar energy technical plan called "U.S. DOE Solar Technology Program Multi-year Technical Plan for 2003-2007 and Beyond." It will be used to coordinate work in the long term for PV and Solar Thermal Technologies.

PV technologies for thin-film devices expanded its partnership program in 2003. The “Thin-Film Partnership Program” collaborated with manufacturers on technology issues that were common to all manufacturing processes and non-proprietary, with an added focus on reliability.

The U.S. DOE Million Solar Roofs Initiative was earmarked for funding in 2003. The initiative sponsored state and local partnerships, financial tools, consumer awareness, and support with codes, standards, and certification programs.
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National Programme

Non-conventional and breakthrough technologies were often accomplished as fundamental research at universities. Laboratory and university researchers worked with industry on high-volume, low-cost manufacturing, such as increasing deposition rates to grow thin-film layers, improving materials utilization, reducing cost, improving reliability and using in-line monitoring to increase yield and performance.

Specific goals through 2006 have not changed and are:

• Reduce the direct manufacturing cost of PV modules by 30 percent to USD 1,75/W;
• Identify and develop leap-frog technologies with the potential for cost reduction;
• Establish greater than 20-year lifetimes for PV systems by improving the reliability of balance-of-system components and reducing recurring costs by 40 percent;
• Work with the PV industry to facilitate achievement of its roadmap goals of 1 GW cumulative U.S. sales (export and domestic) by 2006.

The National PV R&D activities were directed through the U.S. Department of Energy with headquarters in Washington, DC, and by research centers at the National Renewable Energy Laboratory (NREL) and Sandia National Laboratories (Sandia). Overreaching goals of the U.S. PV activities remained the “acceleration of the development of PV as a national and global energy option,” “assurance of the technology” and “global market leadership for the nation.” The dissemination of information pertaining to PV technologies is handled through printed reports, web sites, conferences and workshops. Two direction-related workshops for inverters and energy storage were held in 2003.

The National Solar Program shared the costs in areas of fundamental research, technology development and advanced materials and devices. The authorized funding for PV was categorized into three major areas for FY2003. They were as shown in the following.

The total FY2003 federal budget for the Photovoltaic component of the National PV Subprogram totaled $ 64 million dollars with additional congressional earmarks of $ 10,7 million dollars to fund the Million Solar Roofs Program, an inverter initiative, and various PV installations. Substantial funding for PV-related projects also came through state and local governments, partnerships, PV industry cost sharing, and utilities.

The NCPV relies on the core expertise of NREL and Sandia to create, develop, and deploy PV and related technologies. Other national PV resources that the NCPV draws on are Brookhaven National Laboratory, two Regional Experiment Stations (the Florida Solar Energy Center and the Southwest Technology Development Institute), and U.S. DOE Centers of Excellence at the Georgia Institute of Technology and the University of Delaware (Institute of Energy Conversion). In addition, more than 90 university, industry and utility research partnerships across the country are linked together to function in a unified way. The NCPV awards most of its federal funds through competitive procurements to industry, universities, and other research centers.
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Research, Development and Demonstration

• Research on Thin-film Photovoltaics
  Thin-film devices and materials development were a major part of the PV program and were administered through the NCPV and the “Thin-film Partnership Program.” Thin-film device support ranged from amorphous silicon (a-Si), copper indium diselenide (CIS), copper indium gallium diselenide (CIGS), cadmium telluride (CdTe), thin-film silicon and others. Responding to sustained research efforts, the efficiency of thin-film devices continues to rise. New research to address failure mechanisms, reliability and long-term performance was initiated through a “Thin-film Module Reliability Team.”

  Photovoltaic devices using CdTe can be manufactured using potentially low-cost techniques such as spraying, electro deposition, and high-rate evaporation. Achieving high laboratory efficiencies using these low-cost techniques is an important objective of the National PV Program. To date, more than ten techniques have been used to grow CdTe. First Solar, LLC has continued to advance ultrahigh-rate vapor transport deposition through collaboration with the NCPV.

  A major goal for CIS research is to transfer years of government-sponsored research to industry for pilot-scale manufacturing and to produce commercial modules. New performance heights have been reached for multi-junction solar cells of an unconventional lattice mismatched GaInP/GaInAs/Ge design, establishing this type of cell as a contender for the most efficient type of cell. The 31,3 % one-sun efficiency measured for such metamorphic cells is greater than the previous efficiency record, and would have been the highest one-sun efficiency yet measured had it not been exceeded by a 32,0 % lattice-matched 3-junction cell in the same fabrication run.

  A new record concentrator cell efficiency of 35,2 % under (air mass) AM 1,5, direct, low-AOD (low aerosol-optical-depth) spectrum has been achieved at Spectrolab. Careful consideration of receiver design and the cell package assembly process has resulted in a robust concentrator system, allowing reliable outdoor operation of high-efficiency multi-junction concentrator cells under continuous illumination at high concentration.

  Shell Solar and Global Solar sold non-concentrating commercial products using CIS alloys in 2003. Shell Solar produced 5- to 40-W PV modules made of CIS alloys. Global Solar continued to produce flexible modules for a variety of field applications.

• Research and Development of the Balance-of-System
  Research within the industry and the national laboratories continued to explore improved solid-state switching methodologies for inverters, new control firmware and software, new balance-of-system hardware designs, and entire PV systems that are cost effective. Inverter development included high reliability, universal/modular inverters and conformance with anti-islanding and code requirements. Three contractors were selected to complete a Phase I project aimed at determining designs, feasibility, and market analysis for a high reliability inverter suitable for PV and other renewable energy applications. Issues pertaining to environment, safety and health remained an essential aspect of working with the balance-of-system industry and were included in all work sponsored by the National Solar Program. Phase II of the high reliability initiative was begun in 2003. Prototype hardware from this phase is scheduled for delivery in 2004.

  Sandia National Laboratories’ Distributed Energy Technologies Laboratory (DETL) performed numerous evaluations and performance studies of PV inverters ranging in size from 100 Wac to 100 kWac. Inverter evaluations involve two types of products. They were readily available hardware and developmental prototypes where the manufacturers are seeking assistance. Historically there has been no single document providing design requirements for utility-interactive photovoltaic (UIPV) inverters. Standardized test protocols were developed at the DETL in order to bring diverse requirements together. The DETL grid-tied test protocol included tests for compliance to today’s standards. Examples are IEEE Std. 519 for harmonic distortion, FCC Part 15 for radio-frequency emissions, and IEEE/ANSI 62,41 for surge voltages in low voltage ac power circuits. The grid-tied test plan was designed to evaluate the performance and utility compatibility of UIPV inverters.

• Research on High Performance and Concentrating PV
  The High-Performance Photovoltaic (HiPerf PV) initiative continued exploring the limits of the performance of existing PV technologies, with the aim to nearly double sunlight-to-electricity conversion efficiencies. There was also a goal to demonstrate a high-efficiency III-V cell in a pre-commercial concentrator module.

  To accomplish HiPerf's objective, the National Center for Photovoltaics (NCPV) directed in-house and subcontracted research through the "High Performance PV-Exploring and Accelerating Ultimate Pathways" solicitation in high-performance polycrystalline thin films and multi-junction concentrators. Two specific objectives of this research included bringing efficiencies for thin-film cells toward 25 %, and for modules toward 20 % and creating 33 %-efficient multi-junction concentrators. It is expected that the project's three phases will steer high-efficiency technologies toward commercial, prototype products. Each phase of the project focuses on a specific approach to solving the problems associated with high efficiencies. Phase I entitled "Identifying Critical Paths" continued to identify problems, approaches, and alliances. In 2003, the first HiPerf PV subcontract solicitation was completed.

• Research on Crystalline Silicon
  Fabricating record high-efficiency ribbon silicon solar cells with screen-printed and photolithography-defined contacts was completed in 2003. Optimized rapid thermal firing (RTP) enhanced SiNx-induced hydrogenation helped to achieve record-high efficiency screen-printed edge-defined film-fed growth (EFG) (15,9 %) and “String Ribbon” (15,6 %) cells and a high efficiency “String Ribbon” cell (16,6 %). A two-step RTP firing process was critical in achieving high efficiency screen-printed cells. Step 1 provided SiNx induced hydrogenation and formed an aluminum doped back surface field. Step 2 was designed for silver-grid firing and included rapid cooling to retain hydrogen introduced in Step 1. A selective emitter solar cell design that enhances single-crystal silicon solar cell efficiency by 0,43 % absolute over conventional co-fired cells was developed.

  Other areas of crystalline R&D included large-scale PV module manufacturing using ultra-thin polycrystalline silicon solar cells, innovative approaches to low-cost module manufacturing of string ribbon silicon PV modules, EFG technology and diagnostics R&D for large-scale PV manufacturing, and development of an in-line minority-carrier lifetime monitoring tool for process control during fabrication for crystalline silicon solar cells.

• Research on Plug-and-Play Concepts
  Information on a new concept called the AC PV Building Block was disseminated to industry. This concept is expected to fill an important market niche for code-compliant, retrofit and building-integrated applications. One manufacturer began a feasibility study in 2003. Studies to determine inverter, materials, thermal-management and reliability requirements were initiated.

• Demonstration Programs
  No major national demonstration programs were active during 2003. Several programs were sponsored by various sectors of state governments and utilities, most notably California. Deregulation of the electric utilities and localized energy shortages have spurred several state programs that require installation of PV energy systems along with new R&D efforts aimed at fielded PV systems.

Implementation

• Industry Roadmap and Technical Plans
  Success of PV for the National Solar Program depends on the direction, resources, best scientific and technological approaches, use of the best technologies and continued efforts of the best and brightest among industry, federal laboratory and university partners. The NCPV worked in concert with the industry to lay the groundwork for a “Systems-Driven Approach” to guide new PV work that meets the goals of the industry roadmap and that will be funded by the U.S. DOE.

• Photovoltaic Manufacturing
  To maintain technology leadership and market share, improvements in PV products must move from laboratories to the world marketplace. Against this backdrop of a growing market, the PV Manufacturing R&D Project continued its support through “Photovoltaic Manufacturing R&D - In-line Diagnostics and Intelligent Processing in Manufacturing Scale-Up.” This solicitation encouraged teams to share the cost of high-risk research to develop intelligent processing for larger scale manufacturing that will be the foundation for achieving the goals set out in the U.S. Photovoltaic Industry Roadmap. A new solicitation, “PV Manufacturing R&D - Large-Scale Module and Component Yield, Durability, and Reliability,” was announced and processed in 2003. Its goals were to continue to strive for manufacturing improvements with increased focus on systems and component reliability. Subcontracts are tentatively scheduled for 2004.

  United Solar’s roll-to-roll machine now simultaneously processes six stainless-steel webs at an annual manufacturing capacity of 25-30 MWp. The new machine is not only enhancing throughput capacity, but also has increased the power of each cell by 5-10 %. The most suitable application for United Solar’s product may be in PV-shingle or metal roofing-integrated applications. The new factory in Auburn Hills is not only set up to produce solar cells, but also for the robotic assembly of large roofing laminates.

  Energy Photovoltaics (EPV) operated a prototype manufacturing line in New Jersey. The device is a same-bandgap a-Si:H/a-Si:H double-junction module having an aperture area of 0,75 m 2 and a power rating of 40 Wp. This module has been reported as possibly the lowest-cost commercially available today, being offered at $ 2,25/Wp. Under the Thin-Film Partnership, EPV is also developing technology to manufacture a-Si:H/nc-Si:H (“micro-morph”) cells and, later, modules to enhance the performance of the a-Si product. Iowa Thin Film (ITF) manufactured a-Si cells using roll-to-roll deposition on polymer foils. It is established as a successful niche player making lightweight flexible PV generators for a variety of consumer applications.

  BP Solar ceased operation of its 10-MW/year a-Si plant with enhanced throughput that produced tandem-junction modules. BP also closed its manufacturing facilities for CdTe in 2003. BP continued to manufacture its multi-crystalline PV modules.

  AstroPower was developing an advanced photovoltaic module product based on thin-silicon on ceramic substrates throughout 2003. Recent results included an efficiency of 9,1 %, with a 1,0 cm 2 , single element device and a 5,5 % efficient monolithically interconnected four segment, 5,6 cm 2 , mini-module. This advanced product requires features such as silicon layers grown on a low cost ceramic, total silicon layers 100 µm thick, light trapping and back-surface passivation.

  These performance design features, combined with the use of low-cost continuous processing equipment, are expected to lead to high performance, low-cost photovoltaic panels. The thin-silicon device structure allows for the use of imperfect materials and increased doping levels, and lowers cost by minimizing the use of expensive feedstock material.

• Systems Development and Evaluations
  Sandia National Laboratories led the “Systems Engineering” program that included a balance-of-system program. Its goals were to accelerate evolutionary changes to power processing hardware that would result in improved reliability and performance. Improved reliability of inverters and required switchgear was also funded with Phase I of the high reliability inverter initiative begun in 2003. The initiative continues working with industry to improve "Total Quality Management" programs in the manufacturing and assembly areas. Sandia also urged industry to participate in “Highly Accelerated Life Tests (HALT™)” and “Highly Accelerated Stress Screens (HASS™)” to improve quality and reliability of hardware. The test facilities at Sandia and NREL continued to contribute significantly to all of the reliability-improving programs.

  Sandia and NREL conducted module performance and durability studies for manufacturers based on data from several test sites. For new modules or for those that have operated in the field for years, researchers collect data on electrical performance, physical properties, integrity of solder joints, and properties of encapsulants.
  Tests included outdoor electrical performance, dark current/voltage (I-V), infrared (IR) imaging, ultraviolet (UV) inspection, solder-joint metallurgy, and ultrasonic characterization, as well as destructive testing for specific failure modes.

  An inverter test facility at Sandia provided for characterization, benchmarking, surge testing and accelerated life testing. The 30 kW hybrid test bed for inverters, designed for grid-connected or stand-alone PV systems was in operation as the Distributed Energy Test Laboratory (DETL). It included a complete mini-grid control unit and a 75 kVA micro turbine; a 90 kVA diesel; and load banks that are resistive, inductive, and capacitive in nature. This DETL was used to study the effects of any distributed generation system (including PV and PV hybrid systems) on electrical utility operation, to verify proposed tests in standards and to help establish a certification test protocol for inverters.

  NREL maintained the Outdoor Test Facility (OTF) to test performance and reliability of solar cells, modules, and small (1–5 kW) systems. The OTF also calibrated primary reference cells for use in-house, by other national laboratories, by industry, and by universities. Researchers at the OTF measured performance in actual outdoor tests and using solar simulators indoors. Indoors at the OTF, modules were tested for failure and performance in conditions of high voltage, high heat, high humidity, flexing, static loading, and simulated hail strikes. Outdoors, the test beds at the OTF measured long-term performance and stability. Two test beds performed stress tests of modules under accelerated conditions of high voltage and high sunlight concentration.

• Reliability, Codes and Standards
  Although manufacturers are now offering 10- to 20-year warranties on PV modules, PV systems that operate reliably for 25 years are a major goal of the PV system activities. To reach that goal, the program is supporting research and analysis using field data and models to identify areas for further technical development. Sandia’s “PV System Reliability Plan,” drafted in consultation with industry, is guiding hardware and system development. The plan recommends continuation of several activities such as developing a reliability database to improve understanding of the performance of real systems; examining PV systems and components after extended operation in the field to identify sources of performance degradation or failures that could be prevented by changes in manufacturing; modeling system performance to identify fault-tolerant designs, sensitivities to component failure, and cost-effective component replacement strategies; and working with industry and users to resolve technical or institutional barriers to system reliability. As more installations of PV systems occur, the electrical and personnel safety of the systems are undergoing more thorough examinations by designers, installers, inspectors and users. Vital utility and industry issues, such as codes and standards, were continuing activities in the National Solar Program. The program supported work to provide a consensus of industry input into the National Electrical Code® (NEC®), listing and certification standards, and numerous standards activities in both the domestic and the international arenas. An "Industry Forum" proposed 24 changes in Article 690 of the NEC for the upcoming 2005 Code. The 2005 code cycle input was completed in 2003.

  The new IEEE1547 “Standard for Interconnecting Distributed Resources With Electric Power Systems” was accepted as an IEEE standard in 2003. Three additional tasks for the standard continued to be developed. Underwriters Laboratories began new updates for the UL1741 "Standard for Static Inverters and Charge Controllers for Use in Photovoltaic Power Systems" and expanded the standard to include inverters for all distributed generation.

  The Arizona State University PV Testing Laboratory (PTL) conduced additional module certification tests based on the accreditation certificate they received from the American Association of Laboratory Accreditation. Module models have been qualified to IEEE1262/IEC61215 or IEEE1262/IEC61646 standards since the work began in 1996. The PTL continues to test module types to the UL1703 PV module standard to determine their suitability for listing and has a reciprocity arrangement with European testing organizations. The PTL plans to perform preliminary “Inverter and Systems Certification Tests” within the next year.

  A “National Voluntary Certification Program” for PV installers was developed with the support of the U.S. DOE PV Program and was launched in 2003 with nearly 100 applicants in the first round of testing. State funding was also continued in 2003 with cost sharing by New York.

Industry status

There are several inverter manufacturers serving the U.S. market. They all have complementary markets for inverters, and some export a large percentage of their product. Much of the U.S. inverter industry has been consolidated under Xantrex of Canada. Many new inverter manufacturers emerged in 2003. The new products are being listed and were commercialized in 2003. The new PV inverter manufacturers included Ballard, Solectria, Magnetek, OutBack Power, and others close on the horizon. In 2001 SMA (Germany) opened a sales office (SMA America) in the U.S. and now sells its UL-listed grid-connected residential inverters for U.S. applications.
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Market development

Sandia National Laboratories hosted a Solar Energy Technologies Systems Symposium in 2003 where 180 participants shared systems-related issues and developments. System performance, reliability, energy surety systems-driven approach applications and marketing were some of the key topics.

Barriers to the 50 MW rural electrification market for PV systems were addressed when NCPV personnel provide analysis and technical assistance to organizations such as the U.S. Department of Agriculture’s Rural Utility Service, the U.S. Department of Defense, the U.S. Agency for International Development, the Florida Solar Buildings Program, the U.S. Bureau of Reclamation, Mexico’s Agricultural Secretariat, the Salt River Project, and the Navajo Tribal Utility Authority.

International work included continuation of the Mexico Renewable Energy Program that is sponsored by the U.S. Agency for International Development (USAID) and supported by the U.S. Department of Energy to institutionalize the use of renewable energy technologies. This program had been honored as one of the most successful renewable energy programs for USAID and now serves as a model for increasing the use of renewables in other parts of the world. These projects were implemented in partnership with local Mexican organizations in each geographical or political area to purchase, finance, install and maintain the sustainable systems. This program is resulting in wide-scale system replication, through increased awareness of the benefits of renewable energy technologies, and improved private sector capacities to serve the market.

The NCPV support, such as training and technical assistance in Bolivia, Brazil, China, Ghana, Guatemala, Honduras, India, Indonesia, Kenya, Mexico, Morocco, Nigeria, Pakistan, the Philippines, Russia, South Africa, and Venezuela, has helped U.S. companies continue to make inroads into the international market.

The U.S. DOE Million Solar Roofs Initiative promoted the use of PV and solar thermal to reduce the energy demands of buildings. It enabled businesses and communities to install solar systems on one million rooftops across the U.S. The Million Solar Roofs Initiative was designed to support states and local communities as they developed a strong commitment to the sustained deployment of solar energy technologies. Thirty-five MSR state and local partnerships received grants in 2003, totaling more than $ 1,6 million. MSR partners will use these grants to break down barriers to deploy more solar in the U.S. More than 70 proposals were submitted for the highly competitive grants.
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Future outlook

Footnotes

1. "Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000."

Further reading about the USA

• USA - Country information