Embodied energy of Sliver® modules

Sliver® solar cells, invented and developed at the ANU, allow a reduction in the consumption of silicon by a factor of 5 to 12 compared with state of the art conventional crystalline silicon modules, resulting in a decrease in the number of wafers that need to be processed to produce a kW rated system by a factor of 15 to 30. Both of these features reduce the embodied energy of Sliver® modules. We have calculated an energy payback time of 1.5 years for Sliver® modules compared to 4.1 years for conventional crystalline silicon modules. The equivalent greenhouse gas emissions embodied in Sliver® modules also compares favourably to emissions from fossil fuel sources used for the generation of electricity in Australia

A dark energy multiverse

We present cosmic solutions corresponding to universes filled with dark and phantom energy, all having a negative cosmological constant. All such solutions contain infinite singularities, successively and equally distributed along time, which can be either big bang/crunchs or big rips singularities. Classicaly these solutions can be regarded as associated with multiverse scenarios, being those corresponding to phantom energy that may describe the current accelerating universe

A Comparison of Spectroscopic versus Imaging Techniques for Detecting Close Companions to Kepler Objects of Interest

(Abbreviated) Kepler planet candidates require both spectroscopic and imaging follow-up observations to rule out false positives and detect blended stars. [...] In this paper, we examine a sample of 11 Kepler host stars with companions detected by two techniques -- near-infrared adaptive optics and/or optical speckle interferometry imaging, and a new spectroscopic deblending method. We compare the companion Teff and flux ratios (F_B/F_A, where A is the primary and B is the companion) derived from each technique, and find no cases where both companion parameters agree within 1sigma errors. In 3/11 cases the companion Teff values agree within 1sigma errors, and in 2/11 cases the companion F_B/F_A values agree within 1sigma errors. Examining each Kepler system individually considering multiple avenues (isochrone mapping, contrast curves, probability of being bound), we suggest two cases for which the techniques most likely agree in their companion detections (detect the same companion star). Overall, our results support the advantage the spectroscopic deblending technique has for finding very close-in companions ($\theta \lesssim$0.02-0.05") that are not easily detectable with imaging. However, we also specifically show how high-contrast AO and speckle imaging observations detect companions at larger separations ($\theta \geq$0.02-0.05") that are missed by the spectroscopic technique, provide additional information for characterizing the companion and its potential contamination (e.g., PA, separation, $\Delta$m), and cover a wider range of primary star effective temperatures. The investigation presented here illustrates the utility of combining the two techniques to reveal higher-order multiples in known planet-hosting systems.Comment: Accepted to AJ. 40 pages, 12 figure

Characterisation of the thermal response of Silver® cells and modules

Sliver cells, invented and developed at The Australian National University, are long, thin, narrow, and bifacial. They are constructed from high-grade mono-crystalline silicon. Solar modules that incorporate Sliver cells are significantly different in their construction and performance characteristics to conventional crystalline silicon modules. In Sliver modules, the cells are usually spaced apart to make use of the bifacial nature of the Sliver cells. A scattering reflector on the rear of the module is used to trap most of the incident light within the module structure. However, a fraction of the incident sunlight will not be absorbed by the cells and will instead be coupled out of the module. While this loss of incident radiation results in a reduction in module efficiency, it also results in a proportional reduction in heat generation within the module. This leads to lower module operating temperatures compared with conventional modules of similar efficiencies

Modelling of silver modules incorporating a lambertian rear reflector

Modules incorporating cells which are bifacial and narrow can make use of rear reflectors to capture most of the incident sunlight while covering only a fraction of the module area with cells. Sliver® cells, invented and developed at the ANU, meet these criteria. In this paper we analyse the performance limits of such modules for the case where a diffuse (lambertian) reflector is used. The analysis is carried out for various cell thicknesses, cell spacings and reflectivities of the lambertian reflector. The results show that excellent performance can be realised despite the simplicity of the structure. A module with a 50% coverage with 70µm thick cells can capture up to 84% of the light entering the module. Importantly, the performance of this kind of module is insensitive to module orientation. The results of the analytical model are compared with ray tracing studies and measurements and are shown to be in good agreement. It is concluded that significant module cost reductions can be achieved for only modest reductions in performance by covering half or less of the module surface with cells

The effect of bifacial Sliver® Module orientation on energy production

The Sliver® solar cell technology has the principal features of reduced silicon consumption (down by a factor ~12), a reduced number of wafers that need to be processed per kW (down by a factor of ~30), high efficiency (~19%) and perfect bifacial response. The bifacial response of cells allows a wide range of innovative Sliver® module designs that cannot be achieved using conventional technology (monofacial modules). This work examines the relative performance of monofacial and bifacial modules in a variety of mounting configurations

Influence of reactive ion etching on the minority carrier lifetime in P-type Si

Quasi-steady-state photoconductance (QSSPC) and deep level transient spectroscopy (DLTS) were used to characterize the recombination properties of reactive ion etched p-type Si. The effective lifetime of the plasma-processed samples degraded after etching, with the densities of recombination centers increasing linearly with etch time, before reaching a plateau. Evidence is provided for the long-range (> 2 µm) migration of defects in the samples plasma-etched at room temperature. The relationship between rf power and lifetime degradation is also discussed. A defect with energy position at (0.31 ± 0.02) eV was detected by DLTS in RIE p-Si, whereas no defect level was measured in n-type Si. We demonstrate that this energy level could be used to adequately model the injection-dependence of the measured carrier lifetimes using the Shockley-Read-Hall model

Observations of Binary Stars with the Differential Speckle Survey Instrument. V. Toward an Empirical Metal-Poor Mass-Luminosity Relation

In an effort to better understand the details of the stellar structure and evolution of metal poor stars, the Gemini North telescope was used on two occasions to take speckle imaging data of a sample of known spectroscopic binary stars and other nearby stars in order to search for and resolve close companions. The observations were obtained using the Differential Speckle Survey Instrument, which takes data in two filters simultaneously. The results presented here are of 90 observations of 23 systems in which one or more companions was detected, and 6 stars where no companion was detected to the limit of the camera capabilities at Gemini. In the case of the binary and multiple stars, these results are then further analyzed to make first orbit determinations in five cases, and orbit refinements in four other cases. Mass information is derived, and since the systems span a range in metallicity, a study is presented that compares our results with the expected trend in total mass as derived from the most recent Yale isochrones as a function of metal abundance. These data suggest that metal-poor main-sequence stars are less massive at a given color than their solar-metallicity analogues in a manner consistent with that predicted from the theory