NASA Scientific and Technical Aerospace Reports

micrographs as triangular and trapezoidal with sides inclined at 43 and 47 degrees to the base depending on the above
observation directions, respectively. The dimension of these pyramids varies depending on growth method (50-1000
Angstrom), but the angle between the base and their sides remain the same. The direction from the tip of the pyramid to its
base (and from the shorter to the longer base for trapezoidal defects) is along the Ga to N matrix bond direction. Analysis of
the reconstructed exit wave phase image from the pyramid side indicates a shift of Ga atomic column positions from the matrix
to the N position within the pyramid. In this way a 0.6(+-)0.2 Angstrom displacement can be measured on the pyramid side
between Ga positions in the matrix and within the pyramid.
NTIS
Crystal Growth; Defects; Electron Microscopy; Polarity; Transmission Electron Microscopy; Magnesium; Gallium Nitrides
20060002336 California Univ., Lawrence Berkeley National Lab., Berkeley, CA, USA
Atomic-Resolution 3D Electron Microscopy with Dynamic Diffraction
O’Keefe, M.; Downing, K. H.; Wenk, H. R.; Meisheng, H.; January 2005; 8 pp.; In English
Report No.(s): DE2005-842049; LBNL-57522; No Copyright; Avail.: Department of Energy Information Bridge
Achievement of atomic-resolution electron-beam tomography will allow determination of the three dimensional structure
of nanoparticles (and other suitable specimens) at atomic resolution. Three dimensional reconstructions will yield ‘section’
images that resolve atoms overlapped in normal electron microscope images (projections), resolving lighter atoms such as
oxygen in the presence of heavier atoms, and atoms that lie on non-lattice sites such as those in non-periodic defect structures.
NTIS
Atoms; Diffraction; Electron Beams; Electron Microscopy; Tomography; Dynamical Systems
20060002348 National Renewable Energy Lab., Golden, CO USA
Performance and Reliability of a 1-kW Amorphous Silicon Photovoltaic Roofing System
Adelstein, J.; Sekulic, B.; Feb. 2005; 12 pp.; In English
Contract(s)/Grant(s): DE-AC36-99GO10337
Report No.(s): DE2005-15016395; NREL/CP-520-36583; No Copyright; Avail.: National Technical Information Service
(NTIS)
The National Renewable Energy Laboratory (NREL) has been monitoring the performance of a 1- kWAC United Solar
Systems Corporation (USSC) roofing system over the 6-year period from October 1998 to September 2004. This paper will
investigate the performance and reliability of this system. The annual degradation and seasonal fluctuation of the system’s
power output are calculated using the PVUSA power rating regression model. The system performance is also examined using
the additional performance parameters of yield, reference yield, and performance ratio, which allows for a somewhat less
complicated data collection and analysis. The data indicate that the system has exhibited stable performance over time, with
an overall degradation rate comparable to that found in crystalline silicon systems.
NTIS
Amorphous Silicon; Photovoltaic Conversion; Reliability; Renewable Energy; Solar System
20060002349 National Renewable Energy Lab., Golden, CO USA
Closed-Form Solutions and Parameterization of the Problem of Current-Voltage Performance of Polycrystalline
Photovoltaic Modules Deployed at Fixed Latitude Tilt
Del Cueto, J. A.; Feb. 2005; 12 pp.; In English
Report No.(s): DE2005-15016396; NREL/CRP-520-36565; No Copyright; Avail.: National Technical Information Service
(NTIS)
One obstacle to wider market penetration for thin-film polycrystalline photovoltaic (PV) modules is the lack of field
performance data, notably temperature-coefficient data for the current-voltage (I-V) characteristics over all irradiance levels
encountered in the field. Generally, tem-perature coefficient and performance data are available only in a restricted range of
illumination around 1-sun in-tensity. In this paper, the I-V performance data are pre-sented, analyzed, and parameterized
across a wide range of illumination levels and temperatures, allowing the mod-eling of the performance for three
polycrystalline PV tech-nologies: cadmium telluride, copper indium diselenide, and polycrystalline silicon. The data are
scrutinized for clear-sky and diffuse-illumination conditions.
NTIS
Attitude (Inclination); Deployment; Electric Potential; Latitude; Parameterization; Photovoltaic Cells; Photovoltaic
Conversion; Polycrystals; Thin Films
194