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Abstract This paper describes the point of view of a gas utility regarding systems for cooling and heating by solid sorption. Indeed, the context is favorable to the emergence of such systems first, of course, due to the regulatory constraints on certain refrigerant fluids, but also for their specific technical characteristics (the storage capacity, for example). The gas utilities have in fact shown an increasingly keen interest in all types of sorption systems, as a way of diversifying natural gas utilization, particularly in the summer. After a review of that context, this paper highlights the advantages of solid sorption and describes the criteria for choosing an installation in air conditioning and cooling production applications. Finally, it discusses the difficulties likely to be encountered in developing sorption systems, as well as the prospects for the future.

Biomethane is a flexible energy vector that can be used as a renewable fuel for both the heat and transport sectors. Recent EU legislation encourages the production and use of advanced, third generation biofuels with improved sustainability for future energy systems. The integration of technologies such as anaerobic digestion, gasification, and power to gas, along with advanced feedstocks such as algae will be at the forefront in meeting future sustainability criteria and achieving a green gas supply for the gas grid. This paper explores the relevant pathways in which an integrated biomethane industry could potentially materialise and identifies and discusses the latest biotechnological advances in the production of renewable gas. Three scenarios of cascading biomethane systems are developed.

Rivers are important sources of freshwater and nutrients for the Mediterranean and Black Sea. We present a reconstruction of the spatial and temporal variability of these inputs since the early 1960s, based on a review of available data on water discharge, nutrient concentrations and climatic parameters. Our compilation indicates that Mediterranean rivers suffer from a significant reduction in freshwater discharge, contrary to rivers of the Black Sea, which do not have clear discharge trends. We estimate this reduction to be at least about 20% between 1960 and 2000. It mainly reflects recent climate change, and dam construction may have reduced discharge even further. A similar decrease can also be expected for the fluxes of dissolved silica (Si), strongly controlled by water discharge and potentially reduced by river damming as well. This contrasts with the fluxes of nitrogen (N) and phosphorus (P) in Mediterranean and Black Sea rivers, which were strongly enhanced by anthropogenic sources. Their total inputs to the Mediterranean Sea could have increased by a factor of >5. While N still remained at elevated levels in 2000, P only increased up to the 1980–1990s, and then rapidly dropped down to about the initial values of the 1960s. With respect to the marine primary production that can be supported by the riverine nutrient inputs, Mediterranean and the Black Sea rivers were mostly phosphorus limited during the study period. Their anthropogenic nutrient enrichment could only have had a fertilizing effect before the general decline of the P loads. When also considering Si as a limiting element, which is the case for siliceous primary producers such as diatoms, silica limitation may have become a widespread phenomenon in the Mediterranean rivers since the early 1980s. For the Black Sea rivers, this already started the late 1960s. Gross primary production sustained by rivers (PPR) represents only less than 2% of the gross production (PP) in the Mediterranean, and less than 5% in the Black Sea. Possible ecological impacts of the changing river inputs should therefore be visible only in productive coastal areas, such as the Gulf of Lions, where PPR can reach more than two thirds of PP. Reported ecosystem changes both in the Adriatic Sea and the Black Sea are concomitant with major changes in the reconstructed river inputs. Further work combining modelling and data collection is needed to test whether this may also have been the case for coastal ecosystems at other places in the Mediterranean and Black Sea.

This paper discusses the influence of time horizon on dynamic optimization of small-size wastewater treatment plants alternating aerobic and anoxic processes. The optimization problem consists in determining the aeration policy (air-on and air-off periods) that minimizes the energy dissipated by the aeration system subject to both effluent and operating constraints. Optimization over short time horizons is first considered and reductions of the energy consumption up to 30% are obtained with respect to the usual operating mode of the process. But the application of such aeration strategies eventually results in a biomass wash-out when applied over long time periods. Here, it is shown that long time horizon optimized policies guarantee a durable functioning of the treatment plant. The resulting energy consumption savings are however lower (up to 15%), but are still important.

Abstract The oil and gas industry produces large quantities of sour gases. In the perspective of the geological storage of acid gases in deep aquifers, the solubility of CO2 + H2S mixtures in pure water and in a 2 M NaCl solution was studied under conditions typical of geological storage. Phase equilibrium measurements were undertaken at a temperature of 120 °C and pressures ranging from 1.7 to 35 MPa. Homogeneous mixtures of CO2 + H2S with H2S volume fractions of (0, 1/4, 1/3, 1/2, 2/3 and 1) were placed in contact with solution, and solubility was measured by continuous sampling of the solution. The protocol used was validated by comparison of the results obtained on pure gases with literature data. The mutual interaction between the gases in the mixture has a substantial influence on their respective solubilities. Equation-of-state models reproduce the decrease of CO2 solubility in the presence of H2S, but underestimate the exclusion of H2S by CO2.

Abstract This study investigates the drivers of energy consumption in Sub-Saharan African countries. It applies the bounds testing approach to cointegration to time series data at individual country levels over the period from 1970 to 2011. The study finds that energy consumption is cointegrated with real GDP per capita, industrial output, imports, foreign direct investment, credit to private sector, urbanization and population. Furthermore, the sign and magnitude of long-run estimates vary significantly for a single country and across countries depending on the energy consumption variable used. Overall, the findings confirm the leading role of economic growth, industrial output, population and urbanization. Economic growth, industrial output and population have positive effects on energy consumption in the majority of countries. Given the urgent need to address climate change, African countries should adopt policies to improve energy efficiency and accelerate transition toward renewable energy. The African Renewable Energy Initiative launched at the 21st session of the United Nations Conference of the Parties (COP21) is an opportunity for African countries to provide and maintain widespread access to reliable and affordable environmentally cleaner energy to meet the requirements of rapid economic growth and improved living standards.

The structure of the atmospheric surface layer above the sea is analysed from aircraft turbulence measurements. The data are issued from two experiments performed in 1990 above the Mediterranean sea: Crau and PYREX, and correspond to moderately unstable conditions and to wind velocities ranging from 6 to 20 m/s. Low-altitude straight and level runs were used to compute the variances of the wind components, as well as of the temperature and moisture. Their dependence on the stability index —z/L is analysed. The turbulent fluxes of momentum, sensible heat and latent heat, calculated by the eddy-correlation technique, are used to estimate the neutral bulk coefficients: drag coefficient, Stanton number and Dalton number. The neutral drag coefficient clearly exhibits a dependence on the windspeed, which could be well fitted by the Charnock relation, with a constant of 0.012.

Abstract This work is dedicated to the study of the properties of ethanol blended fuels and evaluates their behavior in conventional Diesel combustion and advanced combustion such as Low Temperature Combustion (LTC). The addition of ethanol into Diesel fuel affects some key properties such as the blend stability, the cetane number or the flash point, the fuel formulation was thus improved. The remaining weak ignitability of the blends requires an engine settings optimization, which associated to the high oxygen content allows a combine reduction of smoke levels and NOx emissions, with a contained fuel consumption penalty. These oxygenated fuels also lead to an extended LTC operating range and improved maximum power output.