Bio-oil instability, or aging, is a significant problem for the long-term storage of fast pyrolysis oils. We investigated bio-oil aging at the molecular level using Fourier-transform ion cyclotron resonance mass spectrometry. Petroleomic analysis suggests that bio-oil aging is resulted from the oligomerization of phenolic lignin products whereas 'sugaric' cellulose/hemicellulose products have negligible effect.

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Thin film materials for photovoltaics such as cadmium telluride (CdTe), copper-indium diselenide-based chalcopyrites (CIGS), and lead iodide-based perovskites offer the potential of lower solar module capital costs and improved performance to microcrystalline silicon. However, for decades understanding and controlling hole and electron concentration in these polycrystalline films has been extremely challenging and limiting. Ionic bonding between constituent atoms often leads to tenacious intrinsic compensating defect chemistries that are difficult to control. Device modeling indicates that increasing CdTe hole density while retaining carrier lifetimes of several nanoseconds can increase solar cell efficiency to 25%. This paper describes in-situ Sb, As, and P doping and post-growth annealing that increases hole density from historic 1014 limits to 1016–1017 cm−3 levels without compromising lifetime in thin polycrystalline CdTe films, which opens paths to advance solar performance and achieve costs below conventional electricity sources.

The temperature and intensity dependence of Voe in CdTe and Cu(lnGa)(SeS)2 polycrystalline thin film solar cells was examined.Voe was measured from 100-330K and from 0.1 to 1 sun illumination. Two distinct regimes of temperature dependence are commonly observed: a linear regime at higher temperatures with slope -0.5 to -3 mV/K and a logarithmic intensity dependence; and a saturation regime at lower temperatures, with little intensity or temperature dependence. The T=O K intercept extrapolated from the linear regime around 300K is related to the activation energy of the dominant recombination mechanism and is equal to the absorber bandgap for Shockley-Read-Hall recombination, or in some cases, from heterojunction interface recombination, which is less than the absorber bandgap. In this work, the temperature dependence of Voe will be characterized for CdTe and Cu(lnGa)Se2 devices with differences in composition and processingconditions. Analysis will focus on the activation energy of the recombination mechanism and saturation at lower temperatures which indicates a maximum separation of the quasi Fermi levels as thermally activated SRH recombination is frozen out. The saturation voltage is -1 V for a typical CdTe device (E g=1.45 eV), -1V for low bandgap Cu(lnGa)Se2 (Eg=1.15), and -1.

Pig in pipelines performs operations for cleaning the pipe interior and internal inspection. In the past few years many 1D models have been developed to simulate the process because of their reduced computational cost; however, they rely on simplifications which are not always valid. In this paper, the results of a three-dimensional (3D) numerical investigation of the interaction between a waxy-oil and a dynamic sealing pig in a pipeline are presented. The results are obtained at a reduced computational cost by using a moving frame of reference, and an "injection" boundary condition for the wax deposited on the wall. The effect of the temperature and the wax particles' size has been investigated. The 3D results show the structure assumed by the debris field in front of the pig. In particular, a lubrication region at the bottom of the pipe, whose dimensions are temperature dependent, is shown. This information cannot be deduced from 1D modeling. The influence of the oil on the mixture viscosity and the internal bed dynamics are discussed. This work provides insights into the interaction between the debris field in front of the pig and pipeline hydraulics.