Influence of the underneath cavity on buoyant‐forced cooling of the integrated photovoltaic panels in building roof: a thermography study

Airflow around building‐integrated photovoltaics (BIPV) has a significant impact on their hygrothermal behavior and degradation. The potential of reducing the temperature of BIPV using an underneath cavity is experimentally and numerically investigated in literature. Most of the models are oversimplified in terms of modeling the impact of 3D flow over/underneath of PV modules, which can result in a non‐uniform surface temperature and consequently a non‐homogenous thermal degradation. Moreover, the simultaneous presence of radiation and convection related to upstream wind, in addition to the combined impact of back‐ventilation and surface convection, is barely addressed in literature. However, these simplifications can result in the unrealistic loading climate conditions. This paper aims to present a unique experimental setup to provide more realistic climate conditions for investigating the ventilation potential of the underneath. The setup consists of a solar simulator and a building prototype with installed PV, placed inside an atmospheric wind tunnel to control upstream wind velocity. Thermography is performed using an infrared camera to monitor the surface temperature of the BIPV. The potential of an underneath cavity with various cavity heights and PV arrangement is further investigated in this paper. The outcome would be eventually useful in the development of practical guidelines for BIPV installation. Copyright © 2013 John Wiley & Sons, Ltd.     

The excess current in cyclic voltammetry arising from the presence of an electrode edge

The popular inlaid disc electrode suffers from an edge effect that is usually, and sometimes unwarrantedly, ignored in analyzing transient voltammograms. This study addresses the role played by the edge in linear scan and cyclic voltammetries when the electron transfer is reversible or quasi-reversible. A simulation models the concentrations, current densities and currents in two circumstances—when the edge in important and when it is absent—simultaneously, and thereby the evolving edge current is quantified. Special attention is paid to the effect that the edge has on the heights and positions of the voltammetric peaks. It is demonstrated that disregarding the edge may lead to the bogus classification of a reversible electrode reaction as quasi-reversible.     

Demonstration of the monolithic interconnection on CIS solar cells by picosecond laser structuring on 30 by 30 cm2 modules

In this paper, we present the selective structuring of all three patterns (P1, P2 and P3) of a monolithic interconnection of CIS (Cu(In,Ga)(S,Se)₂) thin film solar cells by picosecond laser pulses at a wavelength of 1064 nm. We show results for single pulse ablation threshold values and line scribing of molybdenum films on glass (P1), CIS on molybdenum (P2) and zinc oxide on CIS (P3). The purposes of these processes are the p‐type isolation (P1), cell interconnect (P2) and n‐type isolation (P3), which are required for complete cell architecture. The half micron thick molybdenum back electrode can be structured with a process speed of more than 15 m/s at about 15 W average power without detectable residues and damage by direct induced laser ablation from the back side (P1). The CIS layer can be structured selectively down to the molybdenum at process speeds up to 1 m/s at about 15 W average power, due to the precision of direct laser ablation in the ultrashort pulse regime (P2). The ZnO front electrode layer is separated by clean trenches with straight side walls at process speeds of up to 15 m/s at about 10 W average power, as a result of indirect induced laser ablation (P3). A validation of functionality of all processes is demonstrated on CIS solar cell modules (30 × 30 cm²). By replacing one state‐of‐the‐art process by a picosecond laser process at a time, solar efficiencies could be increased for P1 and P2 and stayed on a similar level for P3. After an optimization of the patterning processes in the R&D pilot line of AVANCIS, we achieved a new record efficiency for an all‐laser‐patterned CIS solar module: 14.7% as best value for the aperture area efficiency of a 30 × 30 cm² sized CIS module was reached. Copyright © 2014 John Wiley & Sons, Ltd.     

Near-Enantiopure Trimerization of 9-Ethynylphenanthrene on a Chiral Metal Surface

Enantioselectivity in heterogeneous catalysis strongly depends on the chirality transfer between catalyst surface and all reactants, intermediates, and the product along the reaction pathway. Herein we report the first enantioselective on-surface synthesis of molecular structures from an initial racemic mixture and without the need of enantiopure modifier molecules. The reaction consists of a trimerization via an unidentified bonding motif of prochiral 9-ethynylphenanthrene (9-EP) upon annealing to 500 K on the chiral Pd₃-terminated PdGa{111} surfaces into essentially enantiopure, homochiral 9-EP propellers. The observed behavior strongly contrasts the reaction of 9-EP on the chiral Pd₁-terminated PdGa{111} surfaces, where 9-EP monomers that are in nearly enantiopure configuration, dimerize without enantiomeric excess. Our findings demonstrate strong chiral recognition and a significant ensemble effect in the PdGa system, hence highlighting the huge potential of chiral intermetallic compounds for enantioselective synthesis and underlining the importance to control the catalytically active sites at the atomic level.     

Charge-Tagged DNA Radicals in the Gas Phase Characterized by UV/Vis Photodissociation Action Spectroscopy

Adenosine radicals tagged with a fixed-charge group were generated in the gas phase and structurally characterized by tandem mass spectrometry, deuterium labeling, and UV/Vis action spectroscopy. Experimental results in combination with Born–Oppenheimer molecular dynamics, ab initio, and excited-state calculations led to unambiguous assignment of adenosine radicals as N-7 hydrogen atom adducts. The charge-tagged radicals were found to be electronically equivalent to natural DNA nucleoside radicals.