Conductivité thermique de matériaux poreux humides: évaluation théorique et possibilité de mesure

We develop here a mathematical model of simultaneous heat and mass transfer in unsaturated porous media. We put forward the influence of the total pressure gradient in the gaseous phase on the mass transfer contrary to the classical models where only two driving forces are taken into account: a temperature and a moisture gradient. We use this model on the one hand to investigate the theoretical notion of the apparent thermal conductivity of a wet porous medium and on the other hand to simulate a hot plate measurement and an unsteady state one (“flash” method). We show the great importance of both the total pressure gradient and the boundary conditions, that is to say of the measurement technique on the results.     

Price determination in the EU ETS market: Theory and econometric analysis with market fundamentals

We investigate the price determination of the European Union emission allowance (EUA) of the European Union emissions trading scheme (EU ETS). We postulate an uncertain permit price and risk-averse firms which have the possibility to hedge in the forward market. The firms produce final goods, abate their emissions and trade permits in the permit market. The dependence of the equilibrium permit price on exogenous variables is studied in a permit market model. We test our theoretical findings with empirical data from 2005 to 2010 in the EU ETS market. We use daily forward prices of EUA as our dependent variable. We use several econometric models with multiple stationary time series to discover that there is a strong relationship between the fundamentals, such as German electricity prices and gas and coal prices, with the price of EUA. We find that the EUA forward price depends on fundamentals, especially on the price of electricity as well as on the gas–coal difference, in a statistically significant way.     

The determination of unknown thermal coefficients through phase change process with temperature-dependent thermal conductivity

We study the determination of unknown thermal coefficient of a semi-infinite material through a phase-change process with an overspecified condition on the fixed face with temperature-dependent thermal conductivity. We determine necessary and sufficient conditions on data in order to obtain the existence of the solution. We also give formulae for the unknown coefficients.     

Mind the gap The vicious circle of measuring automobile fuel use

We review the circularity between estimates of automobile use, fuel consumption and fuel intensity. We find that major gaps exist between estimates of road gasoline, the quantity most often used to represent automobile fuel use in economic studies of transport fuel use, and the actual sales data of gasoline, diesel and other fuels used for automobiles. We note that significant uncertainties exist in values of both the number of automobiles in use and the distance each is driven, which together yield total automobile use. We present our own calculations for total automobile fuel use for a variety of OECD countries. We comment briefly on the impact of these gaps on econometric estimates of the price and income elasticities of automobile fuel use. We show that improper use of the circularity often leads to gross errors in estimating fuel intensity and other indicators of energy use for personal transport.     

Decomposing changes in competition in the Dutch electricity market through the residual supply index

We propose to assess the influence of a number of events on the degree of competition in the Dutch electricity wholesale market over the period 2006–2011 through a decomposition method based on the residual supply index. We distinguish regulatory market-integration events, firm-level events and changes in the level of residual demand. We conclude that market-integration measures to improve competition have been effective, but that changes in residual demand appear to have been equally important. Firm-level events have only had a minor impact on the intensity of competition.     

Density functional and bonding study of hydrogen and platinum adsorption on B2-FeTi (111) slab

We performed a density functional theory study (DFT) of hydrogen interaction with Pt on the B2-FeTi (111) surface. The DFT is employed to trace the relevant orbital interactions and to discuss the electronic changes of incorporating H on the Fe–Ti bonding. We determined the optimal location for Pt and then for adsorbed hydrogen. We also followed the density of states and the changes in the chemical bonding for both adsorbed atoms on the surface. The overlap population analysis reveals metal–metal bond breaking after hydrogen adsorption, being this bond the more affected.     

Optimal timing in the privatisation of a utility in an emerging country: the case of electricity distribution in Delhi

Privatisation of utilities in emerging countries is impeded by informational problems. We analyse privatisation of utilities as a process, focusing on the creation of information that arises both before and after the transfer of property. We take the example of the privatisation of electricity in Delhi (Section 1). We examine the interest in creating as much information as possible before the transfer of property, and propose a model based on a trade-off between the potential benefits of creating information prior to selling of assets, vs. facing the costs of delays associated with the risks of a state's failure in creating this information prior to privatisation. We operationalise the model in the case of Delhi and argue that, in similar conditions, it is reasonable and profitable to invest a few years in information building (Section 2). We test the robustness of this model with what risks to be the most stringent critique: the inefficiency of the state (Section 3). We conclude that this simple model is fit for a clear and transparent decision-making on privatisation and reforms.     

Adjusting productivity measures for CO2 emissions control: Evidence from the provincial thermal power sector in China

We examine productivity changes by the types of environmental regulations used to control CO₂ emissions in the provincial, thermal power sector of China from 2009 to 2016. We derive a Törnqvist-type productivity index in which CO₂ emissions are undesirable outputs. The shadow price of CO₂, required for calculating the index, is estimated based on the duality between a revenue and a directional output distance function. Productivity changes are measured using both estimated shadow prices and the actual trading prices of CO₂ in six pilot emissions trading systems. We find that productivity measurement is highly dependent on the choice of CO₂ prices. We also investigate the impact of emission intensity and emissions per se on productivity measurement. We show that productivity measurement depends on the choice of environmental standard.     

Technical change and the marginal cost of abatement

We address one aspect of the treatment of technical change in the environmental economics literature: how technical change impacts the marginal cost of abatement. We review a selection of papers that employ a variety of representations of technical change, and show that these representations have quite different, and sometimes surprising, effects on the marginal costs of pollution reductions. We argue that these varied representations in fact correspond to a variety of different technology options. We then present results indicating that this representation matters — the impacts of technical change on the marginal cost of abatement can crucially impact policy analysis.     

Energy efficiency actions related to the rollout of smart meters for small consumers, application to the Austrian system

Smart meters (SM) may provide large benefits to all stakeholders by providing the information required to implement certain sets of demand response actions. Benefits produced by SM related actions depend on the features of these actions, the system and the targeted consumer group.We first lay out an analytical framework to analyze the application of Demand Response (DR) actions. Based on this framework, we describe a way to determine the response of domestic load in a system to the implementation of DR actions. We propose determining the overall change in the consumption behavior of domestic load based on previously obtained estimates of the peak load and overall consumption reduction for different types of consumers in different types of systems resulting from the application of each set of actions. We have carried out a comprehensive literature review to provide here such estimates.We apply the analytical framework and methodology developed to characterize the reaction of consumers in the Austrian system to different SM related actions. Finally, we provide guidelines on which DR actions to implement in this system and how to implement them. The use of advanced indirect feedback on consumption behavior, critical peak prices and simple time-of-use tariffs is advocated.     

Global Stabilization for Systems Evolving on Manifolds

We show that any globally asymptotically controllable system on any smooth manifold can be globally stabilized by a state feedback. Since we allow discontinuous feedbacks, we interpret the solutions of our systems in the “sample and hold” sense introduced by Clarke, Ledyaev, Sontag, and Subbotin (CLSS). We generalize their theorem which is the special case of our result for systems on Euclidean space. We apply our result to the input-to-state stabilization of systems on manifolds with respect to actuator errors, under small observation noise. 2000 Mathematics Subject Classification. 93B05.     

Improving the mechanical processing of titanium by hydrogen doping: A first-principles study

Solute H in Ti alloys has an important effect on their deformation and ductility, therefore changing the mechanical properties and improving the mechanical processing. We have performed first-principles calculations to investigate the effects of H on the mechanical properties of the hexagonal close packed α-Ti and the body centered cubic β-Ti, and make an attempt to understand how the solute H improves the mechanical processing. We compute the structural parameters, elastic properties, and the generalized stacking fault energies for α- and β-Ti with and without the H addition. We find H decreases the shear moduli and the unstable stacking fault energies of α-Ti, enhancing the deformation tendency, while these quantities are increased by H in β-Ti. We predict the H effect on the ductility using different criteria, and find H makes α-Ti more ductile, but raises the brittleness of β-Ti. Our results indicate H may have a favorable effect on improving the mechanical processing of Ti alloys.     

Mass-production of large size a-Si modules and future plan

We have achieved stable 8% module efficiency with large area monolithic amorphous silicon pin single-junction cell on 910 mm×455 mm glass substrate. Utilizing this type of modules, we have designed, developed and tested photovoltaic modules integrated with roofing material for personal house. We proved that the modules are suitable for roofing purpose, through the detailed designing, actual installation and the performance evaluation. We will start to produce mass-production of amorphous modules with 20 MW/yr capacity in October 1999 in Toyooka-city, Hyogo-prefecture where we establish Kaneka Solartech Corporation as the production subsidiary. We also achieved 11.3% stable efficiency of hybrid solar cell (25 cm²) with amorphous Si and poly-Si thin film. We will introduce this hybrid cell technologies to Toyooka Plant by adding the CVD for thin-film poly-Si till 2003.     

Photovoltaic properties of octithiophene-based Schottky and p/n junction cells: Influence of molecular orientation

We report here on the photovoltaic properties of Schottky and p/n junction cells based on octithiophene (8T). In the solid state, 8T is an elongated planar molecule with efficient p-type transport properties. We investigate in particular the influence of molecular orientation of 8T films on light absorption, I/V characteristics and photocurrent spectra. We show that a substantial increase of the photocurrent density is obtained by aligning the 8T molecules horizontally and parallel to each other on the substrate by means of a simple rubbing technique. This improvement is attributed to a more efficient light absorption rather than to an improvement of the charge transport properties in the sandwich devices.     

Thin film silicon solar cells on glass by substrate thinning

We report on the fabrication of thin film Si solar cells on glass by substrate thinning. We use thin Si films grown on thick Si substrates by either liquid phase epitaxy or chemical vapour deposition. A novel solar cell device fabrication process is then applied to the structure, in which the Si is thinned down to 20–30 μm leaving the grown Si film as the majority of the active material of the structure. We obtain a conversion efficiency of 14.4% for such a thin film Si solar cell on glass.     

Accounting for quality: Issues with modeling the impact of R&D on economic growth and carbon emissions in developing economies

The literature on climate policy modeling has paid scant attention to the important role that R&D is already playing in industrializing countries such as China, where R&D investments are targeting not only productivity improvements but also enhancements in the quality and variety of products. We focus here on the effects of quality-enhancing innovation on energy use and GHG emissions in developing countries. We construct an analytical model to show that efficiency-improving and quality-enhancing R&D have opposing influences on energy and emission intensities, with the efficiency-improving R&D having an attenuating effect and quality-enhancing R&D having an amplifying effect. We find that the balance of these opposing forces depends on the elasticity of upstream output with respect to efficiency-improving R&D, the elasticity of downstream output with respect to upstream quality-enhancing R&D occurring upstream, and the relative shares of emissions-intensive inputs in the costs of production of upstream versus downstream industries. We employ a computable general equilibrium (CGE) simulation of the Chinese economy to illustrate the difficulties that arise in incorporating these results into models for climate policy analysis, and we offer a simple remedy.     

Statistical learning for wind power: A modeling and stability study towards forecasting

We focus on wind power modeling using machine learning techniques. We show on real data provided by the wind energy company Maïa Eolis that parametric models even following closely the physical equation relating wind production to wind speed are outperformed by intelligent learning algorithms. In particular, the CART‐Bagging algorithm gives very stable and promising results. Besides, as a step towards forecast, we quantify the impact of using deteriorated wind measures on the performances. We show also on this application that the default methodology to select a subset of predictors provided in the standard random forest package can be refined, especially when there exists among the predictors one variable, which has a major impact.     

Physical market determinants of the price of crude oil and the market premium

We analyze the determinants of the real price of crude oil by means of an equilibrium correction model over the last two decades where we focus on the aspects of the physical market that impact on the clearing price. We find that two cointegrating relations affect the changes in prices: one refers to OPEC's behavior, attempting to control prices using its market power and quotas; the other to the coverage rate of OECD expected future demand using inventory behaviors. We derive a forecasting equation for the change in oil prices which we use to assess the speculative elements of the price increases of the period 2000–05. We show that worries alien to the physical markets were the causes of the increase in oil prices and we quantify their overall impact.