The field performance of photovoltaic systems has been studied extensively for many applications and a number of databases exist in the United States and internationally. However, these databases focus almost exclusively on the system elecrical performance. Published information on the operation and maintenance (O&M) experience and costs for photovoltaic systems is almost nonexistent. At a time when photovoltaics is being considered as a viable option for distributed energy generation, it is critical that maintenance experience be captured to identify lifecycle costs and/or levelized energy costs for these systems, as well as to identify areas for system and component improvements. This paper addresses the data collection, analysis and results of an offgrid residential customer service program offered by the Arizona Public Service (APS) Company over a six-year period from 1997 through 2002. Standardized, packaged photovoltaic systems were offered and operated by APS through a lease arrangement with customers throughout the state of Arizona. The operation and maintenance records for these systems were carefully tracked and analyzed. The O&M costs, database development, cost drivers, lifecycle cost implications, and lessons learned are presented and discussed. Published in 2004 by John Wiley & Sons, Ltd.key words: photovoltaic systems; operation and maintenance; off-grid residential; utility photovoltaics; database; field experience INTRODUCTION R eductions in the manufacturing costs of photovoltaic (PV) modules 1 coupled with improvements in the balance-of-system hardware 2 have made PV systems an increasingly viable alternate energy option for a variety of applications. 3 Electrical field performance of a number of installed systems has been examined extensively and performance databases 4-6 have been developed. However, as PV attempts to expand into potential markets, questions regarding PV system lifecycle cost (LCC) are bringing a renewed interest in the operation and maintenance (O&M) experience and cost from installed systems. A recent study 7 of grid-tied and stand-alone systems installed throughout the United States over the period [1995][1996][1997][1998][1999][2000][2001][2002] concludes that 50% of the systems were installed improperly, having deficiencies in safety, durability, and/or performance. The impact Contract/grant sponsor: US DOE National Nuclear Security Administration; contract grant number: DE-AC04-94AL85000. Applicationsof these deficiencies on the long-term viability of PV systems is yet another compelling reason to gather and analyze O&M data. Unfortunately, published information on O&M field experience and cost is nearly nonexistent. Why is this information so important? Compiling and analyzing field maintenance events (component and system reliability, scheduled and unscheduled maintenance) are invaluable both from a business and from an engineering standpoint. On the business side, it enables the determination of the LCC for PV systems. The O&M costs coupled with the initial system c...
Two heliostats representing the state-of-the-art in glass-metal designs Ibr central receiver (and photovoltaic tracking) applications were tested and evaluated at the National Solar Thermal Test Facility in Albuquerque, New Mexico from 1986 to 1992. These heliostats have collection areas of 148 and 2(X) m2 and represent lowcost designs for heliostats that employ glass-metal mirrors.The evaluation encompassed the pcrfom_ance and operational characteristics of the heliostats, and examined heliostal beam quality, lhc effect of elevated wincks on beam quality, helioslat drives and controls, mirror mtxlule reflectance and durability, and the overall operational and maintenance characteristics of lhc two heliostats.A comprehensive presentalion of lhc results of these and other tests is presented. The resulls arc prefaced by a review of the development (in the United States) of helioslat leclmology. MTEP,_iSTFitBLITION OF THiS DOOUMENT 16 UNLIMITED ACKNOWLEDGMENTS The authors are indebted to .lake VanDerGeest tbr his enthusiastic and tireless assistance in the testing and evalualion of the prototype heliostats. We are grateful lo Daniel Alpert who guided our efforts and provided invaluable assistance in the interpretation of our test results, including the performance of HELIOS code simulations of collector performance. Our thanks also go to Bob Edgar, Sam Dunk.in, "JJ" Kelton, Larry Yellowhorse, and Winn Erdman for their assistance in numerous technical tasks. The manufacturers of the large-area heliostats provided valuable technical supporl and many useful suggestions throughout the evaluation period; we thank David Gorman (Advanced Thermal Systems, Inc.) and Daryl Bielenberg (Solar Power Engineering Company, Inc.).
In 1993, the mirror facets of one of Sandia's point-focusing solar collectors, the Test Bed Concentrator #2 (TBC-2), were reconditioned. The concentrator's optical performance was evaluated before and after this operation. This report summarizes and compares the results of these tests. The tests demonstrated that the concentrator's total power and peak flux were increased while the overall flux distribution in the focal plane remained qualitatively the same.
Through an international cryomodule collaboration, ASTeC at Daresbury Laboratory has taken the primary responsibility in leading the development of an optimised Superconducting RF (SRF) cryomodule, operating in CW mode for energy recovery facilities and other high duty cycle accelerators. For high beam current operation, Higher Order Mode (HOM) absorbers are critical components of the SRF Cryomodule, ensuring excessive heating of the accelerating structures and beam instabilities are effectively managed. This paper describes some of the cold tests conducted on the HOM absorbers and other critical components during the construction phase, to ensure that the quality and reliable cryomodule performance is maintained.
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