This conference paper describes the GaInAsN cells that are measured to retain 933% and 894% of their original efficiency after exposure to 5 X 1014 and 1 X 1015 cm-2 1-MeV electrons, respectively. The rate of degradation is not correlated with the performance at beginning of life (BOL). The depletion width remains essentially unchanged, increasing by< 1%. Temperature-coefficient data for GaInAsN cells are also presented. These numbers are used to project the efficiency of GaInAsN-containing multijunction cells. The GaInAsN junction is not currently predicted to increase the efficiencies of the multijunction cells. Nevertheless, GaInAsN-containing multijunction cell efficiencies are predicted to be comparable to those of the conventional structures, and even small improvements in the GaInAsN cell may lead to higher multijunction cell efficiencies, especially for high-radiation applications and when cell operating temperature is low.

Recent advances in solid-state switches have made it feasible to design programmable, high-repetition-rate pulsers for induction accelerators. These switches could lower the cost of recirculating induction accelerators, such as the ''small recirculator'' at Lawrence Livermore National Laboratory (LLNL), by substantially reducing the number of induction modules. Numerical work is reported here to determine what effects the use of fewer pulsers at higher voltage would have on the beam quality of the LLNL small recirculator. Lattices with different numbers of pulsers are examined using the fluid/envelope code CIRCE, and several schedules for acceleration and compression are compared for each configuration. For selected schedules, the phase-space dynamics is also studied using the particle-in-cell code WARP3d.

To assess whether houses can meet performance expectations, the new practice of residential commissioning will likely use flow hoods to measure supply and return grille airflows in HVAC systems. Depending on hood accuracy, these measurements can be used to determine if individual rooms receive adequate airflow for heating and cooling, to determine flow imbalances between different building spaces, to estimate total air handler flow and supply/return imbalances, and to assess duct air leakage. This paper discusses these flow hood applications and the accuracy requirements in each case. Laboratory tests of several residential flow hoods showed that these hoods can be inadequate to measure flows in residential systems. Potential errors are about 20% to 30% of measured flow, due to poor calibrations, sensitivity to grille flow non-uniformities, and flow changes from added flow resistance. Active flow hoods equipped with measurement devices that are insensitive to grille airflow patterns have an order of magnitude less error, and are more reliable and consistent in most cases. Our tests also show that current calibration procedures for flow hoods do not account for field application problems. As a result, a new standard for flow hood calibration needs to be developed, along with a new measurement …

This conference paper describes the analysis of the potential of GaInP/GaAs/1-eV/Ge four-junction solar cell to improve on the efficiency of the state-of-the-art GaInP/GaAs/Ge benchmark. We emphasize three factors: (1) The newly proposed terrestrial concentrator spectrum has a lower ratio of red to blue light than does the old AM1.5 direct standard spectrum. (2) Standard two-layer antireflection coatings do not provide near-zero reflectance over the full spectral range of interest for these devices. (3) GaInNAs junctions used to date for the 1-eV junction have quantum efficiencies less than {approx}75%. These factors all limit the device current, adversely affecting the four-junction efficiency. We discuss strategies for ameliorating this problem, including going to alternate structures such as a GaInP/GaAs/0.9-eV three-junction device.

Large-grained (5-20 ..mu..m) polycrystalline silicon layers have been grown at intermediate temperatures of 750-950C directly on foreign substrates without a seeding layer by iodine vapor transport at atmospheric pressure with rates as high as 3 mm/min. A model is constructed to explain the atypical temperature dependence of growth rate. We have also used this technique to grow high-quality epitaxial layers on heavily doped CZ-Si and on upgraded MG-Si substrates. Possible solar cell structures of thin-layer polycrystalline silicon on foreign substrates with light trapping have been examined, compared, and optimized by two-dimensional device simulations. The effects of grain boundary re-combination on device performance are presented for two grain sizes of 2 and 20 mm. We found that 104 cm/s recombination velocity is adequate for 20-m m grain-sized thin silicon, whereas a very low recombination velocity of 103 cm/s must be accomplished in order to achieve reasonable performance for a 2- mm grain-sized polycrystalline silicon device.

Collection of accurate wind speed data is one of the more problematic elements in conducting wind turbine power performance tests. IEC 61400-12 specifies meteorological tower placement between two and four rotor diameters upwind of the test turbine. However, use of an upwind meteorological tower can be difficult at some sites. In some cases, complex terrain near the turbine may make placement of an upwind tower impossible. In addition, purchase and erection of a meteorological tower can be expensive, particularly as the hub height of large turbines increases. Because of these concerns, wind farm owners and turbine manufacturers have expressed interest in the use of turbine nacelle-mounted anemometers for collection of wind speed data. The U.S. Department of Energy (DOE)-Electric Power Research Institute (EPRI) Wind Turbine Verification Program (TVP) has performed data collection and power performance tests at wind energy facilities located in the United States. The purpose of this paper is to evaluate the data gathered from the Big Spring, Texas; Algona, Iowa; and Springview, Nebraska, facilities to determine whether a meaningful relationship can be derived between meteorological-tower and nacelle-anemometer wind speed measurements for Vestas V47 and V66 turbines (Big Spring) and Enron Z-50 turbines (Algona and Springview).

The region between the well-confined plasma and the vessel walls of a magnetic confinement fusion research device, the scrape-off layer (SOL), is typically rich in atomic and molecular physics processes. The most advanced magnetic confinement device, the magnetically diverted tokamak, uses a magnetic separatrix to isolate the confinement zone (closed flux surfaces) from the edge plasma (open field lines). Over most of their length the open field lines run parallel to the separatrix, forming a thin magnetic barrier with the nearby vessel walls. In a poloidally-localized region, the open field lines are directed away from the separatrix and into the divertor, a region spatially separated from the separatrix where intense plasma wall interaction can occur relatively safely. Recent data from several tokamaks indicate that particle transport across the field lines of the SOL can be somewhat faster than previously thought. In these cases, the rate at which particles reach the vessel wall is comparable to the rate to the divertor from parallel transport. The SOL can be thin enough that the recycling neutrals and sputtered impurities from the wall may refuel or contaminate the confinement zone more efficiently than divertor plasma wall interaction. Just inside the SOL is a confinement …

High-resolution transmission electron microscopy (HRTEM) employing focus-variation phase-reconstruction methods is used to image the atomic structure of grain boundaries in a silicon nitride ceramic at a resolution of 0.8 Angstrom

Previous papers on small wind turbines have shown that the ratio of battery capacity to wind capacity (known as battery-wind capacity ratio) for small wind systems with battery storage has an important effect on wind turbine energy output. Data analysis from pilot project performance monitoring has revealed shortcomings in wind turbine energy output up to 75% of expected due to the effect of a''weak'' battery grid. This paper presents an analysis of empirical test results of small wind battery systems, showing the relationships among wind turbine charging rate, battery capacity, battery internal resistance, and the change in battery voltage. By understanding these relationships, small wind systems can be designed so as to minimize''dumped'' or unused energy from small wind turbines.

During summer 2001, Californians reduced electricity usage by 6 percent and average monthly peak demand by 8 percent, compared to summer 2000. These load reductions played an important role in avoiding the hundreds of hours of rotating power outages predicted several months prior. Many factors affected electricity use and peak demand in summer 2001, including weather, changes in the State's economy, and deliberate consumer responses to a variety of stimuli associated with the crisis. This paper assesses the roles played by these contributing factors, with a special focus on the extraordinary efforts made by Californians to reduce electricity consumption. We review the role of media coverage and informational campaigns on public awareness and the impact of rate increases and a variety of publicly funded programs in reducing electricity consumption. We also draw lessons for other regions that may be faced with the prospect of electricity shortages.

The availability of wind energy certificates in Pennsylvania's retail electricity market has made a critical difference in the economic feasibility of developing 140 MW of new wind energy projects in the region. Certificates offer important benefits to both green power suppliers and buyers by reducing transaction barriers and thus lowering the cost of renewable energy. Buyers also benefit through the increased flexibility offered by certificate products. The experience described in this paper offers important insights for selling green power certificates and achieving new wind energy development in other areas of the country.

Over the past several years, there has been considerable development and application of wind forecasting models. The main purpose of these models is to provide grid operators with the best information available so that conventional power generators can be scheduled as efficiently and as cost-effectively as possible. One of the important ancillary services is reserves, which involves scheduling additional capacity to guard against shortfalls. In a recent paper, Strbac and Kirschen[1] proposed a method to allocate the reserve burden to generators. Although Milligan adapted this technique to wind plants[2], neither of these papers accounts for the wind forecast in the reliability calculation. That omission is rectified here. For the system studied in this paper, we found that a reserve allocation scheme using 1-hour forecasts results in a small allocation of system reserve relative to the rated capacity of the wind power plant. This reserve allocation is even smaller when geographically dispersed wind sites are used instead of a large single site.

Construction of a 2.5-MeV linac injector, the Front-End (FE) for the Spallation Neutron Source (SNS) project, was completed in the spring of 2002. Of the major FE subsystems, the rf-driven H- ion source, the electrostatic LEBT, and the first of four RFQ modules had been commissioned by the spring of 2001, and commissioning of the remaining RFQ modules as well as the full system including the elaborate MEBT was carried out in Jan. through May, 2002. The Front End will be shipped to Oak Ridge, starting in June, 2002, and re-commissioned after installation at the SNS site. This paper gives an overview of FE major design features and experimental results obtained during the commissioning process at LBNL.

This conference paper describes the performance data for 14 photovoltaic modules deployed at fixed-latitude tilt in the field are presented and compared. Module performance is monitored continuously for optimum power characteristics. Flat-plate module technologies representative of crystalline, amorphous, and polycrystalline silicon, and cadmium telluride and copper indium diselenide, are scrutinized for energy production, effective efficiency and performance ratio-ratio of effective to reference efficiency. Most performance ratios exhibit seasonal fluctuations largely correlated to air or module temperatures, varying between 80% and 100%. These ratios tend toward larger values during winter and vise versa, except for amorphous silicon and cadmium telluride modules. In a-Si cases, the situation appears reversed: better performance ratios are exhibited during late summer. The effective efficiency and average daily and yearly energy production are analyzed and quantified.

The U.S. General Services Administration Pacific Rim Region (Region 9), manages over 20 million gross square feet of federally owned office space, plus additional leased office space, for the federal government in California, Nevada, Arizona, Hawaii and the Pacific territories. To assist in this real estate management the Pacific Rim Region is developing the GSA Energy and Maintenance Network, or GEMnet. GEMnet is a collection of information technology initiatives, including remote monitoring and control to reduce operational costs by improving energy efficiency, reducing peak demand, and optimizing maintenance in buildings. Ultimately the various systems use a common database platform. This paper describes the status and plans for GEMnet, focusing on how it compares with related monitoring and information technology currently used in nonresidential buildings. This paper will also report on recent activities within the GEMnet purview, demand-shedding and retro-commissioning. For example, two large GSA office buildings in the San Francisco Bay Area participated in the California Independent System Operator (ISO) demand relief program (DRP) during the summer of 2001, shedding nearly 1 MW when called upon. In conjunction with the fielding of GEMnet related programs, a series of retro-commissioning projects is being implemented, scoped to the needs of particular buildings. …

Dilation-balloon expandable coronary stents are commonly made of implant grade stainless steels conforming to ASTM F138/F139, e.g., Biodur? 316LS (UNS S31673). Typical of such stents is the Boston Scientific/Interventional Technologies? (BS/IVT) LP-StentTM. In 2000, BS/IVT determined that the addition of 5 to 6 wt % platinum to Biodur 316LS produced a stainless steel with enhanced radiopacity to make their stents more visible radiographically and thus more effective clinically. A goal of the program was to ensure platinum additions would not adversely affect the corrosion resistance of Biodur 316LS. The corrosion resistance of 5-6 wt % PERSS? alloys and Biodur 316LS was determined using electrochemical tests for general, pitting, crevice and intergranular corrosion. Experimental methods included ASTM A262E, F746, F2129, and potentiodynamic polarization. The 6 wt % PERSS? alloy (IVT 78) had a resistance to pitting, crevice and intergranular corrosion that was similar to the Biodur 316LS base material. IVT 78 was a single-phase austenitic alloy with no evidence of inclusions or precipitates. It was more resistant to pitting corrosion than 5 wt % PERSS? alloys. Performance of the PERSS? alloys was not a function of alloy oxygen content in the range 0.01 to 0.03 wt %.

Using the covariant spectator theory and the transversity formalism, the unpolarized, coincidence cross section for deuteron electrodisintegration, d(e, e'p)n, is studied. The relativistic kinematics are reviewed, and simple theoretical formulae for the relativistic impulse approximation (RIA) are derived and discussed. Numerical predictions for the scattering in the high Q{sup 2} region obtained from the RIA and five other approximations are presented and compared. We concluded that measurements of the unpolarized coincidence cross section and the asymmetry A{sub phi}, to an accuracy that will distinguish between different theoretical models, is feasible over most of the wide kinematic range accessible at Jefferson Lab.

This conference paper investigates which reference spectrum should be used to design GaInP/GaAs/Ge triple-junction cells (at 300 K) in order to optimize their performance outdoors (at elevated temperatures). The outdoor performance is simulated using direct spectra from the recently proposed Module Energy Rating Procedure. We find that triple-junction cells designed for AM1.5D, low-AOD and AM1.5G standard spectra at 300 K all work well for maximizing daily energy production at elevated temperatures. AM1.5G cells are the best choice for midday power production, whereas AM1.5D cells are the best choice for power production during the morning and evening. Performance of cells optimized for a newly proposed Low-AOD spectrum is intermediate between these two extremes.

This conference paper describes the in-depth understanding of the defect formation and resulting changes in material quality occurring during the Cu(In,Ga)Se2 growth process is vital to the successful and widespread use of this photovoltaic material. In an attempt to develop such an understanding, we investigated the growth of Cu(In,Ga)Se2 thin-films from (In,Ga)2Se3 precursors. This was achieved by using energy- and time-resolved photoluminescence spectroscopies to characterize a series of thin-films, each removed at a different point along the reaction pathway of the''three-stage'' growth process. The resulting thin-films are representative of the absorber layer as it proceeds from a Cu-rich to In(Ga)-rich state. The experimental results support a growth model incorporating defect changes in the dominant defect states and improvement in the recombination lifetime during this final stage of the growth process as the material transitions to a Cu-poor phase.

This conference paper describes the Dark current transients measured by changing the voltage bias in a stepwise fashion on CdTe cells results in minutes-long transients after each step. Transients measured at room temperature are controlled by carrier trapping that corresponds to the well known voltage transient phenomena[1]. Transients measured on the same CdTe cell at elevated temperature (60C and 90C) show a much slower decay process. We associate this physical process with''shunt'' current paths induced with reverse bias and removed with forward bias. A different back contact process may produce an opposite voltage dependence. The lack of these transients may be required for the fabrication of ''stable'' thin-film CdTe solar cells.

The pi{sup 0} {yields} gamma gamma decay width is analyzed within the combined framework of Chiral Perturbation Theory and the 1/N{sub c} expansion up to order(p{sup 6}) and order(p{sup 4} x 1/N{sub c}) in the decay amplitude. The eta' is explicitly included in the analysis. It is found that the decay width is enhanced by about 4% due to the isospin-breaking induced mixing of the pure U(3) states. This effect, which is of leading order in the low energy expansion, is shown to persist nearly unchanged at next to leading order. The chief prediction Gamma{sub pi}0{sub {yields}gamma gamma} = 8.10 eV is estimated to have an uncertainty of less than 1%. Observations on the eta and eta' can also be made, especially about their mixing, which is shown to be significantly affected by next to leading order corrections.

This conference paper describes the electronic properties of ZnO/CdS/Cu(In,Ga)Se2 (CIGS)/Mo/SLG polycrystalline thin-film solar cells with compositions ranging from Cu-rich to In-rich were investigated by deep level transient spectroscopy and capacitance-voltage (C-V) measurements. This compositional change represents the evolution of the film during growth by the three-stage process. Four thin-film CIGS samples with different Cu content were obtained. The Cu/(In+Ga) ratio ranges from 1.24 (Cu-rich)to 0.88 (In-rich), whereas the Ga/(In+Ga) ratio ranges from 0.19 (Cu-rich)to 0.28 (In-rich).The Cu-rich sample exhibits a shallow majority-carrier trap with an activation energy of 0.12 eV and another deeper trap with an activation energy of 0.28 eV, whereas the In-rich sample has a shallow minority-carrier trap with an activation energy of 0.12 eV. The two samples show evidence of a deeper trap at higher temperature. C-V measurements showed that the average carrier concentration (N values) around the junction of the cell changed as the film transitions from Cu-rich to In-rich. DLTS shows that acceptor-like traps are dominant in samples where CIGS grains did not go through the Cu-rich to In(Ga)-rich transition. While donor-like traps are dominant in the In(Ga)-rich samples.

This conference paper describes the deep-level transient spectroscopy (DLTS) measurements have been performed on the quaternary semiconductor InGaAsN. A series of as-grown, metal-organic chemical vapor deposited samples having varying composition were grown and measured. A GaAs sample was used as a baseline for comparison. After adding only In to GaAs, we did not detect significant additional defects; however, adding N and both N and In led to larger hole-trap peaks and additional electron-trap peaks in the DLTS data. The samples containing about 2% N, with and without about 6% In, had electron traps with activation energies of about 0.2 and 0.3 eV. A sample with 0.4% N had an electron trap with an activation energy of 0.37 eV.

I will review the basic physical principles underlying the formation energy of various intrinsic defects in common photovoltaic materials. I then use the above principles to explain why doping of semiconductors is, in general, limited and which design principles can be used to circumvent such limits. This work can help design strategies of doping absorber materials as well as explain how TCOs work. Recent results on the surprising stability of polar (112)+ surfaces of CIS will also be described in this context.