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This paper aims to quantify the relation between real GDP, CO2 emissions, renewable and nonrenewable energy consumption, tourism development and labor force for France and Germany as these two countries are pioneer countries pushing Paris agreement within and outside the European Union. The time spans have been used for the period of 1995–2015 according to data availability. In the presence of cross-sectional dependency, several first and second-generation unit root tests confirm the unit root problem while Pedroni and Westernlund confirm the cointegration. Results reveal an inverted U-shape relation between CO2 emissions and real GDP in long run confirming the validity of environmental Kuznets curve for the group of France and Germany. Results declare that renewable energy significantly reduces carbon emissions while nonrenewable energy consumption adds to carbon emissions. Tourism sector was found helpful in carbon reduction that appeals to attract more tourists for the development of sustainable tourism industry by taking energy conservation and emissions reduction in relevant industries in the full consideration. • This paper explores the determinants of carbon emissions for France and Germany. • An inverted U-shape relation was found between carbon emissions and real GDP in long run. • Results reveal renewable energy helps in carbon emissions reduction. • Nonrenewable energy consumption was adding in CO2 emissions. • Tourism sector was found supportive in carbon reduction. [ABSTRACT FROM AUTHOR]

While current climate targets demand substantial reductions in greenhouse gas emissions, the potentials to further reduce carbon dioxide emissions in traditional primary steel-making are limited. One possible solution that is receiving increasing attention is the direct reduction (DR) technology, operated either with renewable hydrogen (H 2) from electrolysis or with conventional natural gas (NG). DR technology makes it possible to decouple steel and H 2 production by temporarily using overcapacities to produce and store intermediary products during periods of low renewable electricity prices, or by switching between H 2 and NG. This paper aims to explore the impact of this decoupling on overall costs and the corresponding dimensioning of production and storage capacities. An optimization model is developed to determine the least-cost operation based on perfect-foresight. This model can determine the minimum costs for optimal production and storage capacities under various assumptions considering fluctuating H 2 and NG prices and increasing H 2 shares. The model is applied to a case study for Germany and covers the current situation, the medium term until 2030, and the long term until 2050. Under the assumptions made, direct reduced iron (DRI) storage mainly serves as long-term storage for several weeks, similar to usual balancing storage capacities. Storing H 2 , on the contrary, is used for short-term fluctuations and could balance H 2 demand in the hourly range until 2050. From an economic perspective, DRI production using NG tends to be cheaper than using H 2 in the short term, and potential savings from the flexible operation with storages are initially small. However, in the long term until 2050, NG and H 2 could achieve similar total costs if buffers are used. Otherwise, temporarily occurring electricity price spikes imply substantial increases in total costs if high shares of H 2 need to be achieved. [Display omitted] • Investigation of the use of renewable hydrogen in primary steel-making. • Analyses of flexible operation with natural gas and hydrogen in direct reduction. • Modeling optimal dimensions and minimum costs under increasing renewable shares. • Case study on optimal hydrogen and direct-reduced iron storages. [ABSTRACT FROM AUTHOR]

The flexible coupling of sectors in the energy system, for example via battery electric vehicles, electric heating or electric fuel production, can contribute significantly to the integration of variable renewable electricity generation. For the implementation of the energy system transformation, however, there are numerous options for the design of sector coupling, each of which is accompanied by different infrastructure requirements. This paper presents the extension of the REMix energy system modelling framework to include the gas sector and its application for investigating the cost-optimal design of sector coupling in Germany's energy system. Considering an integrated optimisation of all relevant technologies in their capacities and hourly use, a path to a climate-neutral system in 2050 is analysed. We show that the different options for flexible sector coupling are all needed and perform different functions. Even though flexible electrolytic production of hydrogen takes on a very dominant role in 2050, it does not displace other technologies. Hydrogen also plays a central role in the seasonal balancing of generation and demand. Thus, large-scale underground storage is part of the optimal system in addition to a hydrogen transport network. These results provide valuable guidance for the implementation of the energy system transformation in Germany. • Combination of all options for flexible sector coupling has high synergy potential. • Flexible hydrogen production is a key enabler of renewable energy system integration. • Hydrogen storage and transport networks are important future energy infrastructures. • Climate targets require a timely acceleration of sector coupling implementation. [ABSTRACT FROM AUTHOR]

Geothermal Organic Rankine Cycle (ORC) power plants have tremendous worldwide potential for the utilization of low- and medium-temperature geothermal resources. However, monitoring of such a system is associated with special challenges for plant operators since the generated electrical power fluctuates strongly, which is caused by mainly two reasons: Firstly, due to the changing condensation conditions caused by air-cooled condensers, and secondly, due to the formation of scaling and fouling. Therefore, the process parameters of a geothermal ORC plant are highly variable, both in terms of diurnal and seasonal fluctuations. Considering the currently applied control software in commercial ORC plants, these fluctuations result in challenges regarding a reliable identification of potential degradation processes within the ORC process. This paper presents a novel analytical and data-based methodology for advanced monitoring of the main components of a two-staged subcritical geothermal ORC system in Southern Germany. These components are the heat exchanger, turbine and air-cooled condenser. For this purpose, operational data from more than three years were preprocessed and evaluated. For the shell-and-tube evaporator, this work applies an equation-based simulation model for the calculation of the thermal resistance due to scaling and fouling. For the turbine and condenser, polynomial functions of various degrees and different objective functions for the numerical computation of regression coefficients are examined. Regression models for three years of operation of the investigated geothermal plant were computed and compared with each other. The results indicate that there are no significant negative changes in the operational performance of most ORC main components during the investigated time period. However, negative operational changes are detected over a three-year period for one turbine of the ORC system. The detailed evaluation of the turbine data reveal a decrease of the normalized isentropic efficiency by 10%, which is significantly higher than the calculated RMSE of the developed correlations, thus indicating a clear performance reduction of the turbine. The developed advanced monitoring methodology allows the operator detailed and accurate assessment of the ORC components conditions, which can not be provided by the software solutions of the commercial ORC manufacturer. Furthermore, the presented methodology can also be applied to other thermal cycle systems with similar components, such as the Kalina Cycle. Finally, a user-friendly software application, developed with the MATLAB® App Designer, is presented. The developed software tool facilitates operators to easily and precisely monitor the operation of the main components of a geothermal ORC plant. • Novel analytical and data-based methodology for advanced monitoring of ORC systems • Equation-based simulation model for shell-and-tube evaporators of ORC systems • Data-based simulation model for turbines and condensers of ORC systems • Development of a software application for advanced monitoring of ORC systems [ABSTRACT FROM AUTHOR]