Solar-powered electrochemical production of hydrogen through water electrolysis is an active and important research endeavor. However, technologies and roadmaps for implementation of this process do not exist. In this perspective paper, we describe potential pathways for solar-hydrogen technologies into the marketplace in the form of photoelectrochemical or photovoltaic-driven electrolysis devices and systems. We detail technical approaches for device and system architectures, economic drivers, societal perceptions, political impacts, technological challenges, and research opportunities. Implementation scenarios are broken down into short-term and long-term markets, and a specific technology roadmap is defined. In the short term, the only plausible economical option will be photovoltaic-driven electrolysis systems for niche applications. In the long term, electrochemical solar-hydrogen technologies could be deployed more broadly in energy markets but will require advances in the technology, significant cost reductions, and/ or policy changes. Ultimately, a transition to a society that significantly relies on solar-hydrogen technologies will benefit from continued creativity and influence from the scientific community.

Magnesium borohydride (Mg(BH4)2) is one of the most promising hydrogen storage materials. Its kinetics of hydrogen desorption, reversibility, and complex reaction pathways during decomposition and rehydrogenation, however, present a challenge, which has been often addressed by using transition metal compounds as additives. In this work the decomposition of Mg(BH4)2 ball-milled with CoCl2 and CoF2 additives, was studied by means of a combination of several in-situ techniques. Synchrotron X-ray diffraction and Raman spectroscopy were used to follow the phase transitions and decomposition of Mg(BH4)2. By comparison with pure milled Mg(BH4)2, the temperature for the γ → ε phase transition in the samples with CoF2 or CoCl2 additives was reduced by 10–45 °C. In-situ Raman measurements showed the formation of a decomposition phase with vibrations at 2513, 2411 and 766 cm−1 in the sample with CoF2. Simultaneous X-ray absorption measurements at the Co K-edge revealed that the additives chemically transformed to other species. CoF2 slowly reacted upon heating till ~290 °C, whereas CoCl2 transformed drastically at ~180 °C.

The effect of transition metal fluorides on the decomposition of NaBH4 has been investigated for NaBH4 ball milled with TiF3, MnF3 or FeF3. The compounds were examined by thermal programmed desorption with residual gas analysis, thermo gravimetric analysis and volumetric measurements using a Sieverts-type apparatus. The phase formation process during thermal decomposition was studied by in situ synchrotron radiation powder X-ray diffraction on the as-milled powders. NaBF4 was among the products in all mechano-chemical reactions. (11)B-NMR spectra analysis gave NaBF4 : NaBH4 ratios of 1 : 150 for Na-Ti, 1 : 40 for Na-Mn, and 1 : 10 for Na-Fe. Pure NaBH4 possessed a hydrogen release onset temperature of 430 °C. The hydrogen release in the NaBH4-MnF3 system began as low as 130 °C. FeF3 decreased the onset temperature to 161 °C and TiF3 to 200 °C. TiF3 reacted completely with NaBH4 below 320 °C. All the examined systems have negligible emissions of diborane species. H-sorption studies performed at selected temperatures above 300 °C exhibited relatively fast desorption kinetics. Partial hydrogen re-absorption was observed for the Na-Mn and Na-Fe samples.

Effective prediction of calcite scaling requires a reliable thermodynamic model for the prediction of the scaling tendency, a kinetic model for the prediction of scaling rate and a transport model to simulate flow in a porous medium. The accurate prediction of the scale deposition can warn the engineers to "treat" the formation around the wellbore in time. In addition, the prediction of the distribution of the scale deposition can direct the engineers to ensure the placement of the inhibitors into the formation zones where the deposition is expected, thus maximizing the probability of successful prevention of formation damage and minimizing at the same time the amount of the required inhibitors. In this contribution, we present a geochemical computational model that combines existing thermodynamic and kinetic models for CaCO3 precipitation, with treatments of flow and diffusion in electrolyte systems, in an one-dimensional porous medium. The geochemical model has the ability to predict the distribution of scale deposition along and around the production wells, as well as the distribution of formation damage (pore blocking, permeability reduction) around the wells.

We use multifractal analysis as a tool for the characterization of geological well log signals. The signals investigated come from dipmeter microresistivity log devices. It is suggested that the multifractal spectra computed from these signals could be used to distinguish geological formations and lithofacies containing different types of oil reservoir heterogeneities.

Nanoscale hydride systems have recently gained increased attention for their possible energy storage applications. In the present work, nanoscale particles of Mg((BD4)-B-11)(2) infiltrated into an activated carbon scaffold were studied by small-angle scattering techniques, and their behavior was compared with that of the bulk powders. Upon heating to 400 degrees C, under dynamic vacuum, the nanoconfined particles maintain their size distribution, and the decomposition affects only the morphology of the particle surface. On the contrary, the bulk powders showed a significant modification of both particle size and surface morphology under the same conditions. The carbon scaffold therefore serves to ensure both the desired nanoscale organization of the magnesium borohydride and stabilization in size of the incorporated material.

Screening experiments were performed in order to investigate the formation of Al-based quaternary hydrides on the basis of multi-component mixtures treated by reactive ball milling under hydrogen pressure. The data indicated that the milling parameters and in particular the milling speed and milling time are of great importance to the formation of any new phase obtained by reactive ball milling. Indeed, a higher milling speed was shown to favour the formation of the new phases. In the case of (MgH2 + Al + LiH) and (MgH2 + LiAlH4) mixtures, the formation of a new phase was observed, which exhibits relatively fast decomposition kinetics.

Carbon cones (CCs) are the fifth form of carbon discovered in the so-called Kværner Carbon Black & H2 Process (CB&H). Under well-defined conditions, CB&H produces a carbon material composed of microstructures, which are flat carbon nano discs (CND) (80%) and carbon nano cones (CNC) (20%). The carbon cones consist of curved graphite sheets: in ordinary periodic graphite, each layer consists of hexagonally arranged carbon atoms, and the five different angles observed are consistent with the incurrence of one to five pentagons at the cone. CNDs consist of stacked graphite sheets, with average radii between 0.4 and 1.5 µm and thickness between 20 and 50 nm. According to the quantum theory of nanographite, the characteristic geometry of the CNDs implies high mechanical and chemical stability in addition to the sensitive electrical properties required by transducers for nano-sensors with low detection limit and fast kinetics. This new material is expected to open new and high risk perspectives in nano-sensor technology by overcoming the major limitations of currently available nanostructures which consist of wires or tubes (including carbon nano-tubes) by improving their kinetics and sensitivity.

Combinations of alkali, alkaline earth hydrides and alanates or aluminium were ball milled under high hydrogen pressures (100bar). Powder X-ray diffraction, volumetric measurements and dynamic high-pressure differential scanning calorimetry (HP-DSC) were used in order to explore reaction mechanisms, formation of new phases and provide answers to the question of reversibility. Ball milling parameters, in particular the milling speed, were found to be important for the reaction paths. Among the studied systems, the formation of new unidentified peaks, however with lack in reversibility, has been found in the mixtures Mg–Al–Ca–H, Ca–Al–Li–H and Ca–Al–Na–H.

In this work Mg- and K-containing alanates have been investigated as possible hydrogen storage materials. Ball milling was carried out under argon or at moderate/high hydrogen pressure in order to obtain an improved driving force for the formation of potential new alanate phases. Powder X-ray diffraction and volumetric measurements were used in order to identify reaction mechanisms and phases forming in these systems. New unidentified peaks were detected for the mixtures 2MgH2+3Al+KH and 2CaH2+Al+2KH. However, they do not seem to belong to reversible hydride phases.

SF6 and PFC are being used as state-of-the-art tracers in tracer-technology programmes aimed at efficient oil recovery in the North Sea. This study aimed at specifying sources of leakage and quantifying emission levels of such gases and at evaluating their effect on global warming. To satisfy these goals, quantification of SF6 and PFC combustion by-products under different realistic flame/temperature conditions (turbine, refinery, power plant, households and car engine) has been performed. The PFC compounds studied were PMCP (CF3C5F9), PMCH (CF3C6F11) and 1, 2-PDMCH ((CF3)2C6F10). Three-dimensional transport atmospheric modelling has been carried out using UAM-AERO for four different tracers' emissions scenarios (Base scenario, one including maximum emissions of tracers and two scenarios including overestimated emissions during loading processes and distribution over the land of Norway). The results showed a significant increase in the background concentrations of SF6 and PFC in the last two mentioned scenarios up to 6 km height approximately. These concentration profiles have been used as input to radiative models. In addition to SF6 spectral data obtained from HITRAN2K complemented with new band measurements, newly obtained data with quantitative spectral analysis for the specific PFC have been used in the line-by-line (GENLN2) and broadband models.

We demonstrate how texture logs computed from multifractal analysis of dipmeter microresistivity signals can be used for characterizing geological formations (lithofacies) in combination with conventional well logs. In particular, we show that the generalized dimension D(1) (entropy dimension) can be considered as a heterogeneity index providing information on the spatial distribution (amounts of clustering) of heterogeneities in geological sediments. In addition, D(1) logs provide complementary information, compared to the conventional GR-log. This is illustrated by comparing core images of two intervals with similar GR responses and differing D(1) responses. Moreover, the method is equally valid if applied to the texture parameter D1(1) computed by generalized multifractal analysis. In this way, we propose a tool for extracting textural information from well logging signals, which provides valuable information suitable for integration with data obtained from conventional well logging tools.

This paper is an attempt to assess more precisely the scope of the multifractal approach for textural characterization. We perform a series of numerical experiments to reconstruct black and white images from the multiscale moments of a measure defined by a reference image. The reconstructed images, obtained by simulated annealing, have multifractal statistics identical to the reference image. A comparison of the reconstructions with the related reference image reveals some of the strengths and limitations of the multifractal characterization.

We introduce a method to generate statistical textural transforms that improves the treatment of non-stationarity and leads to a sharper detection of the boundaries between distinct textures (texture segmentation). This method is based on a sliding window processing with fixed size. The basic idea proposed by the authors is to readjust the measuring window around each pixel so as to maximize homogeneity. We use this method with the dimensions D-n(q) that are derived from the Generalized Multifractal Analysis formalism to show that the D-n(q)s can detect and quantify departures from multifractality, while providing the analogue of the classical generalized dimension if the measure is multifractal.

This paper describes a numerical model developed for the computation of tracer flow in hydrocarbon reservoirs and underground water aquifers. The tracer equations are solved using advanced numerical methods for the reduction of numerical dispersion including a second-order numerical scheme and separate grid refinement. Furthermore the model can handle partitioning and adsorbing tracers and includes hydrodynamic dispersion and molecular diffusion. The results of this study confirm the benefit of the advanced solution methods for tracer flow and illustrate the applicability of the model for the analysis of partitioning tracer flow.