Growth Route Toward III-V Multispectral Solar Cells on Silicon

To date, high efficiency multijunction solar cells have been developed on Ge or GaAs substrates for space applications, and terrestrial applications are hampered by high fabrication costs. In order to reduce this cost, we propose a breakthrough technique of III-V compound heteroepitaxy on Si substrates without generation of defects critical to PV applications. With this technique we expect to achieve perfect integration of heterogeneous Ga1-xInxAs micro-crystals on Si substrates. In this paper, we show that this is the case for x=0. GaAs crystals were grown by Epitaxial Lateral Overgrowth on Si (100) wafers covered with a thin SiO2 nanostructured layer. The cristallographic structure of these crystals is analysed by MEB and TEM imaging. Micro-Raman and Micro-Photomuminescence spectra of GaAs crystals grown with different conditions are compared with those of a reference GaAs wafer in order to have more insight on eventual local strains and their cristallinity. This work aims at developping building blocks to further develop a GaAs/Si tandem demonstrator with a potential conversion efficiency of 29.6% under AM1.5G spectrum without concentration, as inferred from our realistic modeling. This paper shows that Epitaxial Lateral Overgrowth has a very interesting potential to develop multijunction solar cells on silicon approaching the today 30.3% world record of a GaInP/GaAs tandem cell under the same illumination conditions, but on a costlier substrate than silicon.Comment: Preprint of the 28th EUPVSEC proceedings, September 2013, Paris, France. (5 pages

EVAPORATION OF VOLATILE LIQUID POOLS UNDER FORCED CONVECTION: EXPERIMENTAL APPROACH FOR MULTI-COMPONENT LIQUIDS AND VALIDATION OF A VAPORIZATION MODEL

ABSTRACT The evaporation of pools of volatile liquids under dynamic conditions is gaining interest as an engineering subject. Indeed there is an increasing need to optimize the control of thermal or chemical processes and to cope with more and more stringent Environmental, Health and Safety (EHS) regulations applicable to the handling of hazardous liquids, especially those relating to stationary gas turbine installations. A specific issue, tied with flammable substances, comes from the fact that the transition from a flame to an explosion is not sufficiently well controlled due to the difficulty in modeling complex installations. Therefore, the current approach used to address explosion risks consists in quantifying the flux of vapors emitted by the pool and evaluating the mechanical effect entailed by a potential ignition of the flammable cloud generated. It is therefore of paramount importance to accurately know, under variable vaporizing conditions, how much of the volatile matter is extracted by the ventilation stream from the liquid pool and how these vapors get diluted downstream of the source. A survey of the literature shows that while pool evaporation of water has been extensively covered by experimentation, most organic liquids including hydrocarbons, alcohols, ethers, etc. have been insufficiently studied. In order to fill this gap, the authors have combined an experimental approach enabling to quantify the source of vapors with a dedicated Computational Fluid Dynamics (CFD) approach describing the 1 mixing/dilution phenomena in the gas phase. This dual approach has proved very fruitful as it leads to realistic spatial distributions of the species downstream of the source. Therefore it has been utilized to develop experimentally 1 [email protected] verified data for the evaporation rate of single and multicomponent liquids. This paper presents the original experimental rig developed to quantify the vaporization rates. The elaboration of the CFD model and the results obtained when coupling both approaches will be the matter of a next paper

SOx trapping performances of cuo based silica mesoporous adsorbents for desulfurization of industrial flue gas stream

In the present work, CuO/SBA-15 SOx regenerable adsorbents were elaborated. Synthesis conditions were controlled in order to obtain highly dispersed Cu2+ species assumed to be Cu-O-Si species. Materials were evaluated as SOx adsorbents through multicycle adsorption/regeneration experiments. Their performances decrease along cycles due to copper species sintering and there is an optimal copper loading for a maximal SOx adsorption efficiency. Please click Additional Files below to see the full abstract

SOx trapping performances of cuo based silica mesoporous adsorbents for desulfurization of industrial flue gas stream

In the present work, CuO/SBA-15 SOx regenerable adsorbents were elaborated. Synthesis conditions were controlled in order to obtain highly dispersed Cu2+ species assumed to be Cu-O-Si species. Materials were evaluated as SOx adsorbents through multicycle adsorption/regeneration experiments. Their performances decrease along cycles due to copper species sintering and there is an optimal copper loading for a maximal SOx adsorption efficiency. Please click Additional Files below to see the full abstract

Relationship between childhood physical abuse and clinical severity of treatment-resistant depression in a geriatric population

Introduction: We assessed the correlation between childhood maltreatment (CM) and severity of depression in an elderly unipolar Treatment-Resistant Depression (TRD) sample. Methods: Patients were enrolled from a longitudinal cohort (FACE-DR) of the French Network of Expert TRD Centres. Results: Our sample included 96 patients (33% of the overall cohort) aged 60 years or above, with a mean age of 67.2 (SD = 5.7). The majority of the patients were female (62.5%). The Montgomery and Asberg Depression Rating Scale (MADRS) and Quick Inventory Depression Scale-Self Report (QIDS-SR) mean scores were high, 28.2 (SD = 7.49) [MADRS score range: 0–60; moderate severity≥20, high severity≥35] and 16.5 (SD = 4.94) [IDS-SR score range: 0–27; moderate severity≥11, high severity≥16], respectively. Mean self-esteem scores were 22.47 (SD = 6.26) [range 0–30]. In an age- and sex-adjusted model, we found a positive correlation between childhood trauma (CTQ scores) and depressive symptom severity [MADRS (β = 0.274; p = 0.07) and QIDS-SR (β = 0.302; p = 0.005) scores]. We detected a statistically significant correlation between physical abuse and depressive symptom severity [MADRS (β = 0.304; p = 0.03) and QIDS-SR (β = 0.362; p = 0.005) scores]. We did not observe any significant correlation between other types of trauma and depressive symptom severity. We showed that self-esteem (Rosenberg scale) mediated the effect of physical abuse (PA) on the intensity of depressive symptoms [MADRS: b = 0.318, 95% BCa C.I. [0.07, 0.62]; QIDS-SR: b = 0.177, 95% BCa C.I. [0.04, 0.37]]. Preacher & Kelly’s Kappa Squared values of 19.1% (k2 = 0.191) and 16% (k2 = 0.16), respectively for the two scales, indicate a moderate effect. Conclusion: To our knowledge, this is the first study conducted in a geriatric TRD population documenting an association between childhood trauma (mainly relating to PA) and the intensity of depressive symptoms

The Fuel Flexibility of Gas Turbines: A Review and Retrospective Outlook

Land-based gas turbines (GTs) are continuous-flow engines that run with permanent flames once started and at stationary pressure, temperature, and flows at stabilized load. Combustors operate without any moving parts and their substantial air excess enables complete combustion. These features provide significant space for designing efficient and versatile combustion systems. In particular, as heavy-duty gas turbines have moderate compression ratios and ample stall margins, they can burn not only high- and medium-BTU fuels but also low-BTU ones. As a result, these machines have gained remarkable fuel flexibility. Dry Low Emissions combustors, which were initially confined to burning standard natural gas, have been gradually adapted to an increasing number of alternative gaseous fuels. The paper first delivers essential technical considerations that underlie this important fuel portfolio. It then reviews the spectrum of alternative GT fuels which currently extends from lean gases (coal bed, coke oven, blast furnace gases…) to rich refinery streams (LPG, olefins) and from volatile liquids (naphtha) to heavy hydrocarbons. This “fuel diet” also includes biogenic products (biogas, biodiesel, and ethanol) and especially blended and pure hydrogen, the fuel of the future. The paper also outlines how, historically, land-based GTs have gradually gained new fuel territories thanks to continuous engineering work, lab testing, experience extrapolation, and validation on the field

METHOD FOR PRODUCING ELECTRICAL AND/OR MECHANICAL ENERGY FOR A CONSUMER SYSTEM, AND ASSOCIATED PRODUCTION SYSTEM

Said method is implemented via a power generation unit (14) comprising at least one combustion turbine (16) configured to generate, at defined site conditions, without cooling or heating the incoming air stream (20), a defined site electrical or/and mechanical power lower than a predefined maximum required electrical or/and mechanical power. The method comprises the following steps: - cooling the incoming air stream (20) when the power requested by the consumer system is greater than the defined site power of the power generation unit (14) at the defined site conditions, and is lower than or equal to the predefined maximum required power; - heating the incoming air flow (20) when the power requested by the consumer system is lower than the defined site power of the power generation unit (14) at the defined site conditions

PERFORMANCES OF GAS TURBINES IN OIL & GAS APPLICATIONS: SIMPLE THERMODYNAMIC METHODS HELP PREDICT MAJOR TRENDS

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