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Abstract: The pulp and paper industry both uses and produces large amounts of energy and rising fuel prices bring along significant challenges to the sector. Several strategies can be applied in order to remain competitive e.g. an increase in energy efficiency, a switch in fuel and/or a novel energy conversion technology. In this study, we investigate if improved energy conversion strategies can reduce energy costs, primary energy use and CO2 emissions of paper mills within different European countries (The Netherlands, Poland and Sweden). Our results show that differences in history and availability of resources has led to different conversion strategies in the three countries. We found that a natural gas combined cycle, which is largely implemented in The Netherlands due to long term domestic availability of natural gas, has the lowest primary energy demand. Due to a long history of low electricity prices, CHP has not been common in Sweden. Many Swedish mills use biomass as an energy source and due to low CO2 emissions of the national grid the CO2 emission profile of the Swedish paper industry is very low. Our results imply that future conversion routes for the Swedish paper and board industry are again wood based; in case of increasing electricity prices these would be biomass gasification based CHP solutions. With a reduction of 800kg CO2/ton paper on average, a switch from coal to biomass would reduce CO2 emissions in the Polish pulp and paper industry with approximately 0.6Mton/year. A carbon price of 20–25€/ton would, according to our results, be enough to provoke this switch. Due to the high share of natural gas, the CO2 emission reduction potential of the Dutch paper industry (1.5Mton/year) is even larger than in Poland. Due to high biomass prices and relative low CO2 emission profile of natural gas, a carbon prices of more than 60€/ton CO2 would be needed to provoke a switch in The Netherlands. Provided with few alternatives, the most effective strategy in The Netherlands would be an increase in energy efficiency. [Copyright &y& Elsevier]

Abstract: Evolutionary behavior of syngas chemical composition and yield have been examined for paper and cardboard at three different temperatures of 800, 900 and 1000°C using CO2 as the gasifying agent at constant flow rate. Specifically the evolution of syngas chemical composition with time has been investigated. Pyrolysis of the sample was dominant at the beginning of the gasification process as observed from the high initial devolatilization of the sample followed by char gasification of material to form syngas for a long period of time. Results provided the role of gasification temperature on kinetics of the CO2 gasification process. Increase in gasification temperature provided increased conversion of the sample material to syngas. Thus the sample conversion to syngas was low at the low temperature of 800°C while at elevated temperatures of 900 and 1000°C substantial enhancement of the kinetics process occurred. The evolution of extensive reaction rate of carbon-monoxide was calculated. Results show that increase in temperature increased the extensive reaction rate of carbon-monoxide. The global behavior of syngas chemical composition examined at three different temperatures revealed a peak in concentration of H2 to exhibit after few minutes into the gasification that changed with gasification temperature. At 800°C gasification temperature peak in H2 was displayed at 3min into gasification while it decreased to only 2min, approximately, at gasification temperatures of 900 and 1000°C. The effect of reactor temperature on CO mole fraction has also been examined. Increase in the gasification temperature enhances the mole fraction of CO yields. This is attributed to the increase in forward reaction rate of the Boudouard reaction (). The results show important role of CO2 gas for the gasification of wastes and low grade fuels to clean syngas. [Copyright &y& Elsevier]

• Nanogel particles for CO 2 capture with lower cycles (303–348 K) are developed. • Carbon paper as supporter shows higher CO 2 capacity, adsorption and desorption rate. • Avrami's fractional order model accurately predicts the CO 2 uptake behaviors. • The CO 2 capture process is governed by film and intraparticle diffusion resistance. • Carbon paper as supporter shows lower sensible heat and desorption activation energy. Amine-containing nanogel particles with a lower cooling and heating cycles (303–348 K), which is beneficial to limit the degradation and volatile of amine, has been developed as promising absorbents for CO 2 capture. It is extremely important to understand the CO 2 capture kinetics and mechanisms for design and operation of corresponding processes. In present work, poly tetra fluoroethylene and carbon paper were used to support the GPs by filtering and loading method. The CO 2 uptake and release performance of poly tetra fluoroethylene and carbon paper supported nanogel particles was measured. It was found that carbon paper as supporter shows higher CO 2 capacity and desorption rate. A comparison of three different kinetic models shows that carbon paper as supporter gives a more enhanced kinetic behavior. Avrami's fractional order model presents the best fit to experimental data. To further investigate the mechanism of CO 2 uptake on absorbents, interparticle diffusion model, intraparticle diffusion model and Boyd's film diffusion model were also applied. Film diffusion resistance governed the mass transfer rate of CO 2 uptake on studied absorbents at the initial CO 2 uptake stages. In the following stages, intra-particle diffusion resistance plays a major role until the equilibrium is reached. The sensible heat of carbon paper as supporter is about 25% lower than that of poly tetra fluoroethylene as supporter. The desorption activation energy obtained from the Arrhenius equation is 18 kJ/mol for carbon paper as supporter, which is 84% lower than that of the typical aqueous MEA solvent. [ABSTRACT FROM AUTHOR]

This paper proposes a novel compressed CO 2 energy storage system based on 13X zeolite temperature swing adsorption (TSA). Based on 13X zeolite adsorption gas storage and exothermic and desorption heat storage characteristics, the system could accomplish high-density storage of low-pressure CO 2 and efficient heat circulation. Evaluate the system investment by economic analysis model, and apply the law of thermodynamics to perform energy and exergy analysis. Under the design conditions, the round-trip efficiency, the efficiency of the system, the energy storage density, and the investment cost per unit power were 88.88%, 69.30%, 6.23 kWh/m3, and 1.22 k$/kW, respectively, which demonstrates that the system is strongly feasible and has broad engineering application prospects. Sensitivity analysis results suggest that adsorption temperature and desorption temperature positively and negatively affect system performance. The storage pressure and temperature have a trade-off relationship and almost opposite effect on the system. The lower pinch point temperature difference assists in improving the thermodynamic performance of the system but leads to added cost. System thermal and economic performance have a gamble relationship in the equipment efficiency dimension. • A trans-critical compressed CO 2 energy storage system based on 13X zeolite temperature swing adsorption is proposed. • The contact heat exchange solution enables instant internal circulation of heat, eliminating the need for heat storage media and storage tanks. • In this paper, the system feasibility is evaluated in terms of both performance and cost. [ABSTRACT FROM AUTHOR]

Dual-source solar-air heat pumps represent a promising solution for overcoming the limitations associated with single-source utilization, thereby enhancing heat pump performance. However, running the heat pump by alternatively employing the more advantageous source requires the integration of a controller capable of continuously monitoring and predicting the heat pump's performance in response to dynamic environmental and operational variables. Even so, a selective alternate operation does not allow to get the maximum possible performance from the use of the two heat sources. A different approach to address this challenge is the simultaneous utilization of the two sources, by properly combining two evaporators in the CO 2 circuit. This paper presents an experimental investigation of a dual-source heat pump using CO 2 as refrigerant, which can operate in three different evaporation modes: air-mode (using a finned-coil evaporator), solar-mode (using a photovoltaic-thermal PV-T evaporator), and simultaneous-mode (using both the evaporators simultaneously). The novel solution presented here does not require to split the refrigerant flow rate between the two evaporators and at the same time it solves the problem of possible maldistribution at the inlet of the evaporators. Experimental data indicate that the heat pump operating in simultaneous-mode allows to increase the evaporation pressure and the coefficient of performance compared to operation in air-mode or solar-mode. The measurements have been employed for validating a model of the system, capable of predicting steady-state and dynamic performance under various environmental and operational conditions. Simulation results show that the simultaneous-mode operation can be outperformed by the solar-mode only at high irradiance and low air temperature, when the evaporation temperature gets higher than the air temperature. Finally, the impact of the number of PV-T collectors and solar irradiance on the heat pump performance has been simulated and discussed. On this regard, the simultaneous use of the two heat sources adds more flexibility to the system and its design, because even the availability of a small solar area can contribute enhancing the performance over the mere air source heat pump. • A dual source CO2 heat pump with PV-T evaporators has been experimentally investigated. • The simultaneous use of the two evaporators adds more flexibility to the system and its design. • The availability of a small solar area can contribute enhancing the performance over the mere air source. • A dynamic numerical model of the heat pump has been realized in Matlab environment. • The model is used to study the heat pump's performance varying solar irradiance and number of collectors. [ABSTRACT FROM AUTHOR]

This paper examines the potential for synergistic benefits of co-utilizing three waste streams of pinewood, spent fluid catalytic cracking (sFCC) catalyst, and waste CO 2 via thermochemical conversion. For this, a lab-scale fixed-bed semi-batch scale reactor facility is utilized to investigate the impact of using sFCC catalyst and its reusability on the syngas output, quality, and energy during pyrolysis and CO 2 -assisted gasification of pinewood 800–900 °C. Results are reported on the pyrolysis and CO 2 -assisted gasification of pinewood, as well as the impact of using sFCC catalyst and its reusability on syngas output, quality, and energy. Incorporating the catalyst without direct contact with the solid feedstock resulted in syngas enhancement and reusing this catalyst led to <5 wt% char formation from the gasification at 900 °C. The addition of FCC catalyst improved the total CO yield and its rate with an increase in temperature due to improved cracking of volatiles and their simultaneous reforming using CO 2. In addition, the syngas and energy yields decreased when the catalyst was in direct contact with the solid biomass which also acted as a barrier between the feedstock and gasifying agent, leading to lower CO production. Catalytic gasification at 900 °C using CO 2 provided combustible gas output that was 1.4 times higher than the feedstock mass which suggests that at least 0.4 g of CO 2 consumption for combustible gases, such as H 2 and CO. This points to the synergistic potential in co-utilization of waste streams of biomass, spent FCC catalyst, and CO 2 that provided not only waste management and energy recovery but also energy efficient carbon sequestration. Temperature programmed oxidation of the char residue left from the pyrolysis and gasification tests and coke that forms on the sFCC catalyst revealed conversion of about 0.1 g of the feedstock to coke that was significantly more resistant to oxidation than the char formed. • Investigated synergistic utilization of pinewood, CO 2 and spent FCC catalysts. • Examined pyrolysis and CO 2 -assisted gasification of pinewood and sFCCs at 800–900 °C. • Avoiding catalyst feedstock contact resulted in syngas enhancement. • CO 2 consumption of at least 0.4 g/g feedstock was converted into combustible syngas. • Reusing sFCCs for gasification resulted in coke deposition led reduction in activity. [ABSTRACT FROM AUTHOR]

The use of ejectors in transcritical CO 2 refrigeration systems is of key significance for improving system performance, and the investigation of ejectors is particularly important. In this paper, a CO 2 two-phase numerical model considering non-equilibrium phase change is established to investigate the two-phase flow characteristics and entrainment performance in the ejector under different operating conditions. In particular, this study is devoted to the trade-off analysis of internal mass transfer and energy utilization efficiency. After a series of tests, the accuracy of the numerical model has been validated, and with the increase of primary inlet pressure, the entrainment performance first increases and then decreases, while the entrainment performance is greatly improved with the increase of primary temperature. There is a critical back pressure, beyond which the entrainment performance drops rapidly. If the pressure reaches 8.46 MPa and the corresponding temperature is set at 303.7 K, the efficiency of the ejector is 27%. When the temperature rises to 313 K, the efficiency increases to 31%, and the ratio of exergy destruction decreases from 48.3% to 10.2%. However, when the back pressure drops to 4.0 MPa, the working efficiency is only 1.8%, which fails to work normally. Effectively balancing the inlet conditions with energy utilization is a key strategy for optimizing ejector use. • CO 2 two-phase model using phase change for CO 2 ejector in refrigeration systems. • Two-phase flow behavior and entrainment performance of the ejector are analyzed. • Exergy destruction and working efficiency under different conditions are calculated. • The efficiency increases up to 31% while the primary temperature rises to 313.7 K. • With the back pressure of 4.0 MPa, the exergy destruction ratio is as high as 72.9%. [ABSTRACT FROM AUTHOR]

This paper delves into an econometric analysis to uncover the differences between Nordic European Countries - NEC (Norway, Denmark, Finland, Sweden) and South-East European Countries - SEEC (Greece, Bulgaria, Romania, Hungary). The focus is on exploring the interplay among electricity generation from Renewable Energy Sources (RES), CO 2 emissions, urban population and GDP per capita in these two European regions. The study employs cross-sectional dependence, first and second-generation panel unit root tests, Pedroni panel and Westerlund panel cointegration tests, ARDL, Dumitrescu-Hurlin causality test to establish the relation among variables. The findings reveal that in both regions, CO 2 emissions are significantly influenced by GDP per capita, urbanization and RES generation. Furthermore, urbanization plays an important role. When examining causality in SEEC, three bidirectional relationships are observed: urbanization and CO 2 , urbanization and GDP, urbanization and generation from RES, and two unidirectional causalities: CO 2 and GDP, generation from RES and CO 2. In contrast, for the NEC, there are two bidirectional causalities: urbanization and CO 2 , urbanization and generation from RES, and two unidirectional causalities: GDP and CO 2 , generation from RES and CO 2. These results highlight the nuanced and varied nature of environmental and economic dynamics across various European regions. • Relationship between CO 2 emissions, GDP per capita and electricity production from RES. • Investigating two groups of EU countries located in the North and SE Europe. • Estimations with Fully Modified and Dynamic Ordinary Least Squares. • Causality and cointegration between variables. [ABSTRACT FROM AUTHOR]

Abstract: Synthetic natural gas (SNG) production from dry black liquor gasification (DBLG) system is an attractive option to reduce CO2 emissions replacing natural gas. This article evaluates the energy conversion performance of SNG production from oxygen blown circulating fluidized bed (CFB) black liquor gasification process with direct causticization by investigating system integration with a reference pulp mill producing 1000 air dried tonnes (ADt) of pulp per day. The direct causticization process eliminates use of energy intensive lime kiln that is a main component required in the conventional black liquor recovery cycle with the recovery boiler. The paper has estimated SNG production potential, the process energy ratio of black liquor (BL) conversion to SNG, and quantified the potential CO2 abatement. Based on reference pulp mill capacity, the results indicate a large potential of SNG production (about 162MW) from black liquor but at a cost of additional biomass import (36.7MW) to compensate the total energy deficit. The process shows cold gas energy efficiency of about 58% considering black liquor and biomass import as major energy inputs. About 700ktonnes per year of CO2 abatement i.e. both possible CO2 capture and CO2 offset from bio-fuel use replacing natural gas, is estimated. Moreover, the SNG production offers a significant fuel replacement in transport sector especially in countries with large pulp and paper industry e.g. in Sweden, about 72% of motor gasoline and 40% of total motor fuel could be replaced. [Copyright &y& Elsevier]

Power cycles running on carbon dioxide at supercritical pressure and temperature were introduced in the late ninety-sixties but, after a warm welcome to the theoretical performance announced, they were later abandoned in favour of standard combustion gas turbines. Nevertheless, the technology was brought forward about a decade ago and has since captured significant attention from the scientific and industrial community. The number of publications has risen exponentially and there are several experimental projects under development today. The performances of these cycles have been deeply analysed in literature, proving to be theoretically competitive. This paper reviews all the works published in the topic to date. Different cycle concepts (stand-alone and in combination with other cycles using the same or different technologies), layouts, fuels, applications (power only or combined heat and power) and operating conditions are reviewed and categorised according to the configuration of the cycle. This latter feature is thought to be an interesting added value of this paper since, rather than just listing the past work in the area of sCO 2 power cycles, it also organises the numerous cycles in different categories and provides a comparison of the claimed performance of each one of them. This comparison between the performances of the various configurations is based on the values declared in the original papers and thus applies to very different boundary conditions. Obviously, this great heterogeneity of the available data (in particular the temperatures and pressures considered) makes it impossible to establish a fair comparison between the configurations reviewed. Therefore, a future study seems to be mandatory where the performances of all cycles should be compared for the same set of operating conditions. [ABSTRACT FROM AUTHOR]

Natural refrigerants are recognised as the most promising working fluids to replace conventional HFCs in food refrigeration systems. Due to its negligible GWP, zero ODP and attractive thermo-physical properties, the CO 2 working fluid has grown in popularity over the last decade, especially in supermarket refrigeration systems. These systems can be classified into three main categories: indirect, cascade and all CO 2 transcritical booster structures. However, the appropriate control and design optimisation of such systems require further investigation. This paper presents an experimental investigation into the performance of CO 2 finned-tube gas coolers/condensers with different designs in a CO 2 booster system. The heat exchangers were mounted in a specially designed test facility that allowed the control of different test conditions and parameters, including air on temperatures and flow rates, approach temperatures and CO 2 operation pressures. The integrated refrigeration system can provide specified CO 2 fluid parameters at the heat exchanger inlet, through which the system efficiency can be calculated. Subsequently, extensive measurements were recorded from this test rig, with insightful indications into system performance and the most influential parameters for system optimisation. These include heat exchanger designs, air on temperatures and flow rates, supercritical and subcritical pressure controls and cooling capacity controls, which are described in the paper. [ABSTRACT FROM AUTHOR]

Hydrogen produced from renewables-fuelled electrolysis has the potential to provide deep decarbonisation for sectors that are the most difficult to decarbonise, but the intermittency of renewable sources may result in low electrolyser utilisation and, consequently, high costs. This study determines the greenhouse gas (GHG) emissions and levelised cost of hydrogen (LCOH) associated with blending wind electricity with the grid to increase electrolyser utilisation. A novel cost model was developed to determine the production performance, costs and embodied CO 2 emissions of an electrolyser with hybrid fuel supply (wind and grid) considering dynamic load constraints of alkaline (ALK) and Proton exchange membrane (PEM) electrolysers and using high-resolution historical weather data to determine wind production profiles in two case study regions: northern (Bayannur) and southern (Pingtan) China. The results show that using 52% of grid electricity in an ALK electrolyser in Bayannur reduces LCOH by 11%, increasing hydrogen production by 74% but with 17.4 kg CO 2 / kg H 2 generated in CO 2 emissions. When a carbon price is accounted for, the optimal electrolyser utilisation is reduced to 40%, with the LCE 44% reduced. Emissions of 9.8 kg CO 2 /kg H 2 are lower than for stream methane reforming with carbon capture. In Southern China (Pingtan), LCOH is higher than Bayanur because of the high electricity cost. The economic benefits of increasing grid power depend primarily on the total CAPEX cost, grid power cost, and carbon tax. By altering the carbon tax, the optimal blend of wind/ grid differs. The grid contribution to the optimal blend diminishes as a carbon tax approaches 35 USD/ t CO 2. • This paper analyses the value of adding grid electricity to a pure wind-powered H 2 production plant. • The LCOH and CO 2 life-cycle emissions are obtained for Alkaline and PEM electrolysers. • We are introducing the novel ICOH metric to optimise the trade-off of LCOH and CO 2 emission on H 2 production. • Using only 52% of grid electricity in an ALK electrolyser, H 2 production can increase by 75%. [ABSTRACT FROM AUTHOR]

Electric vehicles (EVs) are widely recognized as promising solutions to reduce carbon emissions from the transportation sector. The rapid proliferation of EVs intensifies the interdependency between the power distribution system (PDS) and transportation system (TS). This paper proposes a distributed low-carbon economic dispatch scheme for the integrated power and transportation system (IPTS). Carbon emissions from the TS are quantified by a carbon dioxide calculation model, and the emissions from the PDS are determined by the electricity generation of fossil-fueled generators and the carbon reduction of carbon capture and storage (CCS) devices. An integrated model reformulation method is employed to transform the original non-convex model into a tractable one. Then a distributed solution method based on the spectral penalty parameter based adaptive alternating direction method of multipliers (SPPA-ADMM) is developed to protect the privacy of the PDS and TS. The reformulated model is solved iteratively, and the penalty parameter of the SPPA-ADMM is adjusted adaptively to improve the convergence performance of the method. Numerical results on three test systems demonstrate the effectiveness of the proposed scheme in achieving low-carbon economic dispatch of IPTS. Moreover, case studies validate the superiority of the SPPA-ADMM based distributed solution method in computation performance. • A low-carbon economic dispatch scheme for integrated power and transportation system is proposed. • An integrated model reformulation method is designed to transform the non-convex model into a tractable one. • The SPPA-ADMM based distributed solution method is used to protect the privacy and improve computation efficiency. • Effects of the proliferation of EVs on costs and carbon emissions are discussed in sensitivity analysis. [ABSTRACT FROM AUTHOR]

A diffuse interest on cycle modifications for R744 applications that allow to achieve better CO 2 cycles performance can be inferred from the literature. The parallel compression cycle in flash tank configuration seems to be an interesting solution and the authors conducted an experimental campaign to estimate the critical parameters that influence its performance in an actual cycle. Previous to that a thermodynamic analysis was lead to investigate the expectable performance of the cycle and the influence of key parameters such as compressors volumetric flow ratio and separator efficiency. The thermodynamic model designed also allowed the definition of the limit conditions for an optimal operability of the cycle of interest. The experiments showed that the theoretically reachable improvements in terms of refrigerating capacity and coefficient of performance are threatened by several phenomena which may occur in a real system. These detrimental effects are described and commented in the paper. The paper also includes experimental data obtained during the experimental activity for operating conditions typical of commercial refrigeration applications. [ABSTRACT FROM AUTHOR]

This paper investigates the effect of adding H 2 and CO to a syngas on oxy-MILD combustion. This work employs a Perfectly Stirred Reactor (PSR) model to calculate the autoignition temperature and the critical oxygen concentration for different component fuels under oxy-MILD conditions. Our investigation obtains the critical O 2 concentration for oxy-MILD combustion of various H 2 /CO/CH 4 component fuels. The results indicate that adding H 2 to CH 4 significantly reduces the minimum O 2 concentration required for achieving the MILD state while adding CO has little effect. Furthermore, using the novel PCA method, we analyze characteristic chemical time scales for oxy-MILD combustion for different fuel ratios. We conclude that the mixture containing H 2 and CO can be used as fuel for oxy-MILD combustion, as its characteristic chemical time scale is comparable to the turbulent time scale, resulting in Da number close to unity. However, achieving a steady MILD combustion state is more challenging than methane due to reduced ignition delay times. Moreover, syngas with various ratios of H 2 /CO presents the potential for controlling the MILD combustion process. • The critical value of oxygen concentration for oxy-MILD combustion of syngas with various CH 4 /H 2 /CO ratios is revealed. • Kinetic analysis of the effects of H 2 and CO in syngas on MILD combustion is presented. • A new method is proposed to calculate characteristic chemical reaction time scales by PCA method for MILD combustion. [ABSTRACT FROM AUTHOR]

Liquid carbon dioxide (CO 2) energy storage (LCES) system is emerging as a promising solution for high energy storage density and smooth power fluctuations. This paper investigates the design and off-design performances of a LCES system under different operation strategies to reveal the coupling matching regulation mechanism of the charging and discharging processes. An off-design performance prediction model is developed based on preliminary designs of turbomachinery components and heat exchangers to evaluate the feasibility of the LCES system. The performances of the charging and discharging processes are analyzed under different load levels with two operation strategies: constant pressure charging and constant pressure discharging (CP-CP) operation strategy, and constant pressure charging and sliding pressure discharging (CP-SP) operation strategy. Results show that the LCES system has a round trip efficiency of 61.83% and an energy storage density of 21.92 kW·h·m−3 under the rated condition. As the input load level increases from 80% to 120%, the maximum charging time of the system decreases from 5.15 h to 3.36 h under the constant pressure operation strategy. When the output load level increases from 70% to 120%, the maximum discharging time of the system decreases from 5.48 h to 3.31 h under the constant pressure operation strategy and from 5.60 h to 3.30 h under the sliding pressure operation strategy. Besides, the round trip efficiency of the LCES system increases first and then decreases as both input and output load levels rise, while the energy storage density of the system follows a parabolic curve only with an increase in the output load levels. For better system performance, the CP-SP operation strategy and CP-CP operation strategy are more suitable for the system with output load levels of 70–100% and 100–120%, respectively. These achievements will provide a valuable reference for the stable operation of the LCES under off-design conditions. • An off-design performance model is developed for the liquid CO 2 energy storage system. • Charging and discharging performances are studied under different load levels. • Two operation strategies are proposed to examine the part-load performance of the system. • The optimal load ranges of operation strategies are determined. [ABSTRACT FROM AUTHOR]

• Earlier phase-out of coal is not the best answer to achieve energy transition. • The 2050 plan and historical RES investments maxima are not enough to reach climate neutrality. • What is the effect of regional RES limits over Nationwide RES limits. • Where will be the states in Germany having major RES deployment. • Myopic optimization reveals new challenges for energy policy. This paper will introduce the open-source model MyPyPSA-Ger, a myopic optimization model developed to represent the German energy system with a detailed mapping of the electricity sector, on a highly disaggregated level, spatially and temporally, with regional differences and investment limitations. Furthermore, this paper will give new outlooks on the German federal government 2050 emissions goals of the electricity sector to become greenhouse gas neutral by proposing new CO 2 allowance strategies. Moreover, the regional differences in Germany will be discussed, their role and impact on the energy transition, and which regions and states will drive the renewable energy utilization forward. Following a scenario-based analysis, the results point out the major keystones of the energy transition path from 2020 to 2050. Solar, onshore wind, and gas-fired power plants will play a fundamental role in the future electricity systems. Biomass, run of river, and offshore wind technologies will be utilized in the system as base-load generation technologies. Solar and onshore wind will be installed almost everywhere in Germany. However, due to the nature of Germany's weather and geographical features, the southern and northern regions will play a more important role in the energy transition. Higher CO 2 allowance costs will help achieve the 1.5-degree-target of the electricity system and will allow for a rapid transition. Moreover, the more expensive, and the earlier the CO 2 tax is applied to the system, the less it will cost for the energy transition, and the more emissions will be saved throughout the transition period. An earlier phase-out of coal power plants is not necessary with high CO 2 taxes, due to the change in power plant's unit commitment, as they prioritize gas before coal power plants. Having moderate to low CO 2 allowance cost or no clear transition policy will be more expensive and the CO 2 budget will be exceeded. Nonetheless, even with no policy, renewables still dominate the energy mix of the future. However, maintaining the maximum historical installation rates of both national and regional levels, with the current emissions reduction strategy, will not be enough to reach the level of climate-neutral electricity system. Therefore, national and regional installation requirements to achieve the federal government emission reduction goals are determined. Energy strategies and decision makers will have to resolve great challenges in order to stay in line with the 1.5-degree-target. [ABSTRACT FROM AUTHOR]

Abstract: In the current uncertain context that affects both the world economy and the energy sector, with the rapid increase in the prices of oil and gas and the very unstable political situation that affects some of the largest raw materials’ producers, there is a need for developing efficient and powerful quantitative tools that allow to model and forecast fossil fuel prices, CO2 emission allowances prices as well as electricity prices. This will improve decision making for all the agents involved in energy issues. Although there are papers focused on modelling fossil fuel prices, CO2 prices and electricity prices, the literature is scarce on attempts to consider all of them together. This paper focuses on both building a multivariate model for the aforementioned prices and comparing its results with those of univariate ones, in terms of prediction accuracy (univariate and multivariate models are compared for a large span of days, all in the first 4 months in 2011) as well as extracting common features in the volatilities of the prices of all these relevant magnitudes. The common features in volatility are extracted by means of a conditionally heteroskedastic dynamic factor model which allows to solve the curse of dimensionality problem that commonly arises when estimating multivariate GARCH models. Additionally, the common volatility factors obtained are useful for improving the forecasting intervals and have a nice economical interpretation. Besides, the results obtained and methodology proposed can be useful as a starting point for risk management or portfolio optimization under uncertainty in the current context of energy markets. [Copyright &y& Elsevier]

Abstract: This paper reports an artificial neural networks (ANN) modelling programme for a light-duty diesel engine powered using blends of various biodiesel fuels with conventional fossil diesel. ANN was used here to predict nine different engine-out responses, namely carbon monoxide (CO), carbon dioxide (CO2), nitrogen monoxide (NO), unburned hydrocarbon (UHC), maximum pressure (P max), location of maximum pressure (CAD P max), maximum heat release rate (HRRmax), location of maximum HRR (CAD HRRmax) and cumulative HRR (CuHRR). Four pertinent engine operating parameters, engine speed, output torque, fuel mass flow rate and biodiesel fuel types and blends, were used as the input parameters for this modelling work. The feasibility of using ANN in predicting the relationships between these inputs and outputs were assessed. Simulated results were first validated against data from parallel engine test-bed study. Key effects of ANN “model” and “model parameter” such as type of transfer function, training algorithm and number of neurons, along with the methods of optimising the network settings were also presented in this paper. [Copyright &y& Elsevier]

Abstract: The application of Carbon Capture and Storage (CCS) technology to energy-intensive processes is starting to attract attention, presenting an opportunity for developing multi-user CO2 transportation networks. Recognising that most industrial facilities have not been designed with CCS in mind, this paper begins by looking at the practical issues associated with retrofitting CCS to industrial facilities. It then explores the technical and legal issues associated with building a CO2 network. This is followed by an analysis of the costs involved. Having identified the key issues, a case study from North East England is presented as an example of what is possible in an area of high CO2 emissions. The paper concludes by considering the issues involved in sizing a CO2 network which can evolve to meet future needs and linking that to the development of policy. [Copyright &y& Elsevier]

Abstract: Black liquor gasification (BLG) for bio-fuel or electricity production at the modern pulp mills is a field in continuous evolution and the efforts are considerably driven by the climate change, fuel security, and renewable energy. This paper evaluates and compares two BLG systems for methanol production: (i) oxygen blown pressurized thermal BLG; and (ii) dry BLG with direct causticization, which have been regarded as the most potential technology candidates for the future deployment. A key objective is to assess integration possibilities of BLG technologies with the reference Kraft pulp mill producing 1000air dried tonnes (ADt) pulp/day replacing conventional recovery cycle. The study was performed to compare the systems’ performance in terms of potential methanol production, energy efficiency, and potential CO2 reductions. The results indicate larger potential of black liquor conversion to methanol from the pressurized BLG system (about 77million tonnes/year of methanol) than the dry BLG system (about 30million tonnes/year of methanol) utilizing identical amount of black liquor available worldwide (220million tDS/year). The potential CO2 emissions reduction from the transport sector is substantially higher in pressurized BLG system (117million tonnes/year CO2 reductions) as compared to dry BLG system (45million tonnes/year CO2 reductions). However, the dry BLG system with direct causticization shows better results when considering consequences of additional biomass import. In addition, comparison of methanol production via BLG with other bio-refinery products, e.g. hydrogen, dimethyl ether (DME) and bio-methane, has also been discussed. [Copyright &y& Elsevier]

• Thermochemical energy storage of methane reforming using slag is researched. • High temperature slag can be used as energy source and catalyst bed. • Thermochemical storage efficiency first rises and then drops during reforming. • Optimal flow rate and slag bed length exist for maximum energy storage efficiency. In iron and steel industry, production process is accompanied by a large amount of residual heat as high temperature slag. Methane reforming with carbon dioxide is one of the typical chemical energy storage processes, and it can be applied to use residual heat and reduce carbon dioxide emission. In this paper, thermochemical energy storage performance of methane reforming using high temperature slag is researched. According to experimental and numerical results, high temperature slag can be used as energy source and catalyst for thermochemical energy storage process by methane reforming. Slag is almost non-porous material, and its activation energy is higher than that of common catalyst, so slag only has high catalytic activity under high temperature. During methane reforming process, methane conversion and thermochemical storage efficiency first increases and then decreases with reaction rate dropping, and the position with maximum reaction rate gradually changes from front of slag bed to the end. Many factors including inlet conditions and reactor structure can affect thermochemical storage performance. Increase of slag initial temperature can improve methane conversion and thermochemical energy storage efficiency. As reactant flow rate decreases or slag bed length rises, methane conversion gradually increases, while thermochemical energy storage efficiency first increases and then decreases. With suitable conditions, thermochemical energy storage efficiency of slag can be higher than 60%. [ABSTRACT FROM AUTHOR]

• Integrated model of ICE and CTPC in GT-SUITE calibrated against experimental data. • Performance prediction of four CTPC system layouts under a cruise driving cycle. • Control structure of mode switch module and PID controllers are proposed. • CTPC systems show strong robustness against highly transient heat sources. • Enhancing pump and turbine performance facilitates CTPC integration with ICE. Carbon dioxide transcritical power cycle (CTPC) systems are considered a new and particularly interesting technology for waste-heat recovery. In heavy-duty truck engine applications, challenges arise from the highly transient nature of the available heat sources. This paper presents an integrated model of CTPC systems recovering heat from a truck diesel engine, developed in GT-SUITE software and calibrated against experimental data, considers the likely fuel consumption improvements and identifies directions for further improvement. The transient performance of four different CTPC systems is predicted over a heavy-heavy duty driving cycle with a control structure comprising a mode switch module and two PID controllers implemented to realize stable, safe and optimal operation. Three operating modes are defined: startup mode, power mode, and stop mode. The results demonstrate that CTPC systems are robust and able to operate safely even when the heat sources are highly transient, indicating a promising potential for the deployment of this technology in such applications. Furthermore, a system layout with both a preheater and a recuperator appears as the most promising, allowing a 2.3% improvement in brake thermal efficiency over the whole driving cycle by utilizing 48.9% of the exhaust and 72.8% of the coolant energy, even when the pump and turbine efficiencies are as low as 50%. Finally, factor analysis suggests that important directions aimed at improving the performance and facilitating CTPC system integration with vehicle engines are: (1) ensuring long-duration operation in power mode, e.g., by employment in long-haul trucks; and (2) enhancing pump and turbine performance. [ABSTRACT FROM AUTHOR]

• A high spatial resolution CO 2 emissions inventory of 280 Chinese cities was compiled. • Three methods were compared to evaluate the carbon efficiency of Chinese cities. • The best and worst-performing cities were consistent regardless of different methods. • Top-ranking cities were located in the coastal regions of China. • Lagging-behind cities were located in the central and western regions of China. Comprehensive and accurate city-level carbon dioxide emissions inventory is key to success in China's pursuit of low-carbon development. Based on a high-resolution gridded data, this paper evaluates and benchmarks the carbon emissions efficiency of 280 Chinese cities using three different methods, i.e., composite index, data envelopment analysis and stochastic frontier analysis. The comparative analysis reveals that the average carbon emissions efficiency of Chinese cities is about 70–90%, with only 9 efficient cities (3%). Although the ranking of intermediate cities varies greatly according to the method employed, the most and least carbon-efficient cities remain consistent. While the best-performing cities are found in the coastal regions, the worst-performing cities are located in the central and western regions, which suggests an imbalanced low-carbon development in China. Guided by the results, local governments are encouraged to compete and learn from similar ranking benchmarks in a new regime of "Top Runner City". Finally, the scores of carbon emissions efficiency can provide a scientific basis for the bottom-up allocation of carbon emissions rights to boost the development of the nationwide carbon market in China. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • We incorporate a variety of principles and indicators into an improved ZSG-DEA model. • We conduct a multi-criteria allocation of China's CEA by 2030 to provincial shares. • We measure the total and per capita space for carbon emissions by province. • All provinces reach the DEA frontier with different CEA ranging from 4.21 to 16.77 Gt. • Differentiated provincial reduction policies are the key to achieving China's INDCs. Abstract Accelerating global warming has suggested the importance of controlling greenhouse gas emissions associated with human activities. In striving to fulfill the Paris Agreement, China has announced its Intended Nationally Determined Contributions (INDCs) aimed at reducing its carbon dioxide (CO 2) emission intensity by 60–65% in 2030 against the level of 2005. However, China's INDCs cannot be fulfilled without formulating appropriate schemes for the allocation of carbon emission allowance (CEA) at sub-national scales. To help close the gap in our knowledge, this paper starts with measuring the overall CEA of China by 2030, and then proposes a science-based scheme for CEA allocation by developing an improved zero sum gains-data envelopment analysis (ZSG-DEA) model. It demonstrates that the final CEA of some northern provinces can be cut down as compared to their initial shares and, conversely, most southern provinces experience an increase in their CEA. Comparing the final share of CEA by province with current carbon emissions, we observe that provinces with abundant energy reserves, such as Shanxi, Inner Mongolia and Shaanxi, tend to be operating in a state of overshoot in terms of space for carbon emissions (SCE). In contrast, there remains SCE when it comes to Guangdong, Hunan, Fujian, etc. The remaining provinces, such as Heilongjiang, Hebei and Ningxia, are close to the break-even point. In view of the differing SCE of individual provinces, common but differentiated policies for CO 2 emission control would be the key to achieving China's INDCs. The research findings lay a scientific basis for the Chinese government to make its INDCs come true through inter-provincial collaboration on emission reduction, but also serve as a reference for fueling further scientific discussions and development of schemes for the allocation of responsibility for carbon emissions at multiple scales within and beyond China. [ABSTRACT FROM AUTHOR]

Highlights • A recuperative heat pump using zeotrope with a large temperature glide is proposed. • Good application for water heater with a large temperature glide of 84 K is verified. • Operating conditions of air-conditioning and refrigeration (<2 MPa) is obtained. • N -hexane/propene and R4310mee/R32 is a superior alternative to CO 2 heat pump. • Off-the-shelf components of air-conditioning and refrigeration can be used. Abstract The heat sinks with a finite capacity and a large temperature glide bring about new challenges of efficient heat pump. This paper presents a modified subcritical zeotropic mixture recuperative high-temperature heat pump cycle for the above heat sinks by introducing a modified recuperation process of zeotropic mixtures with a large temperature glide in gas-liquid phase change region. Performance analysis and optimizations are performed by genetic algorithm in MATLAB connecting HYSYS considering COP as an objective function for hot water supply from 15 °C to 99 °C with an air source using five candidate binary zeotropic mixtures. The study presents the effects of pressures and mixture compositions on cycle COP and exergy utilization. The results show that the modified cycles using n -hexane/propene and R4310mee/R32 efficiently improve COP and exergy utilization by enabling a good temperature match of heat sink with refrigerant under the optimal conditions. Furthermore, compared with CO 2 transcritical cycle, CO 2 /R32, CO 2 /R143a and CO 2 /R41 result in about 8.88%, 6.55% and 4.95% increases of COP, while n -hexane/propene and R4310mee/R32 recuperative cycles bring about 4.35% and 3.28% increases of COP. Interestingly, the operating pressures of n -hexane/propene (1409.5 kPa/704.0 kPa) and R4310mee/R32 (1968.0 kPa/980 kPa) are far lower than those of pure CO 2 and CO 2 blends, which are consistent with those of conventional air-conditioning and refrigeration. A preliminary cost comparison result reveals the low-cost advantage of the modified zeotropic mixture recuperative cycle because off-the-shelf air-conditioning and refrigeration products can be used. It is concluded that n -hexane/propene and R4310mee/R32 subcritical recuperative heat pump cycles can be superior alternatives to CO 2 heat pump cycle. [ABSTRACT FROM AUTHOR]

Highlights • Local CO 2 emission factors of China's coal chemical products are published. • The total CO 2 emission from China's coal chemical industry was 607 Mt in 2015. • The spatial disparity of CO 2 emission from China's coal chemical industry is great. • CO 2 emission from modern coal chemical industry is predicted to be 417 Mt in 2020. • Carbon capture, utilization, and storage has great potential to reduce its emission. Abstract As the largest producer of coal chemical products in the world, China faces tremendous pressure to reduce its carbon emission. An accurate quantification of the carbon dioxide (CO 2) emission of coal chemical industry in China is therefore necessary. However, due to the variety of coal chemical products and limitations of CO 2 emission factors, the total CO 2 emission of coal chemical industry has yet to be determined. In this study, local CO 2 emission factors of coal chemical products in China are published based on first hand data from twenty-three coal chemical enterprises and the total CO 2 emission of China's coal chemical industry is extrapolated. The provincial-level spatial distribution of the CO 2 emission of coal chemical industry is presented to assist the government in identifying key emission reduction areas. Additionally, scenario analysis of CO 2 emission for China's modern coal chemical industry in 2020 is conducted to determine whether the development of the modern coal chemical industry will have a significant impact on future CO 2 emission, as well as the effect of carbon capture, utilization and storage technologies on the reduction in carbon emission. The estimate shows that the total CO 2 emission of the coal chemical industry in 2015 was 607 million tonnes (Mt), accounting for approximately 5.71% of China's total CO 2 emission. The figure is higher than the total annual CO 2 emission of a country such as Canada (555 Mt) or Brazil (486 Mt). Quantifying the emission of the coal chemical industry is therefore critical to understand the global carbon budget. The spatial distribution shows that Shandong, Inner Mongolia and Shanxi release one-third of the coal chemical industry's total CO 2 emission. Considering the development of the modern coal chemical industry, its CO 2 emission is predicted to be as high as 416.52 million tonnes in 2020. However, the CO 2 emission could be reduced by 317.98 million tonnes when carbon capture, utilization and storage are applied to process and energy systems simultaneously. This paper quantifies the CO 2 emission of the coal chemical industry in China for the first time, identifies key chemical products and the provinces in which they are produced, explores the carbon reduction potential by scenario analysis, and provides specific data to support the assessment of effective CO 2 reduction policy. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Examined thermochemical conversion CO 2 to CO using Mg, Fe, Al based mixed oxides. • Layered double hydroxide derived metal oxides were prepared via co-precipitation. • Mg/Fe/Al based oxygen carrier provided high and stable CO production over 5 cycles. • High surface area of Mg/Fe/Al provided up to 80% of total oxidation on its surface. Abstract Carbon monoxide generation from the splitting of CO 2 is of greater importance now than ever before due to continuous increase in CO 2 levels in the atmosphere and concerns on the sustainability of energy and environment. This paper examines the conversion of CO 2 to CO via thermochemical redox looping of metal oxides. Oxides of Mg/Fe and Mg/Al/Fe prepared from layered double hydroxide (LDH) were explored to aid in the conversion of CO 2 to CO. The prepared metal oxides from LDH offered superior stability of porous metal structure and sustained redox capability at moderate to high temperatures required for conversion. The formations of these metal oxides from LDH were analyzed using thermogravimetric analysis (TGA). The results showed 635 µmol CO/g of Mg/Fe oxides as compared 557 µmol CO/g from Mg/Al/Fe. Continuous operation resulted in some sintering effects with deteriorated redox performance. The redox capability of Mg/Fe oxide over multi-cycle operations was lower as compared to Mg/Al/Fe oxides, which showed significant thermal stability while maintaining high CO yield and redox capability over extended redox cycles. The specific LDH derived metal oxides produced CO three times higher than those reported previously in the literature using Zr-doped ceria and other perovskites per unit mass of the oxygen carriers. While the surface area was reduced in Mg/Al/Fe the yield after the first cycle remained unchanged; both the surface area and yield decreased in Mg/Fe oxides. Mixed-metal oxide prepared from co-precipitation provided highly porous Mg/Al/Fe oxide compared to Mg/Fe or Mg/Al. High porosity enhanced the surface oxidation of Mg/Al/Fe that contributed to more than 85% oxidation from fast surface reactions. After two cycles, the redox rates changed little with further increase in the number of cycles to reveal surface area stability of Mg/Al/Fe. Multiple cycle operation suggested superior redox kinetics of Mg/Al/Fe than Mg/Fe. These LDH derived mixed metal (Mg/Al/Fe) oxide provided high and sustained CO production rates compared to those reported in the current literature used other materials so that the examined materials have good potential to serve as oxygen carrier for CO 2 splitting to CO. [ABSTRACT FROM AUTHOR]

Abstract: This paper aims at probing into the topic of power units’ operation and dispatch based on Carbon Dioxide (CO2) trading scheme. The trading cost of CO2 emission is embedded into the traditional economic dispatch model, which will be solved by the New Particle Swarm Optimization (NPSO). By considering the CO2 trading scheme, the influences of the various strategies for unit’s dispatch are simulated and analyzed in this paper. The proposed method, NPSO is developed in such a way that PSO with Constriction Factor (PSO-CF) algorithm is applied as a based level search. NPSO introduces two operators, “Random Particles” and “Fine-Tuning” into the PSO-CF algorithm to improve the drawback of searching global optimum and make the search method more efficient at the end of search. The efficiency and ability of NPSO is demonstrated by the six generating units. Simulation results indicated that reasonable solutions provide a practical and flexible framework for power sectors. They can be also used for generating alternatives and thus help decision makers to obtain the goals of minimal operation cost under their desired emission’s policies. [Copyright &y& Elsevier]

Abstract: This paper aims to present an economic overview of the opportunities for energy renovation of single-family houses in Denmark financed over the long term. The paper focuses on the economic difference between energy savings and the repayment of investment. Taking out the average remaining 20% equity in long-term property mortgage loans and utilising it for extensive energy renovation improves both the economy and the extent of included measures. Approximately 30% of energy consumption in Denmark is used for space heating. The existing 1 million single-family houses account for approximately half of this, thus making energy renovation a key factor for the reduction of CO2 emissions. The conclusions were that in average the possible budget for renovation varied between €20,000 and 40,000 per single-family house. The equity of the house was particularly dependant on geographical location and construction period. Different energy renovation measures were analysed in terms of economy showing that a wide range of specific measures had a positive economic balance for the homeowner from year 1. The economic balance between saved energy and repayment of the investment is however very dependent on the assumed future energy price. An example showed that a typical house from 1925, still in its original form, could yield annual savings for the homeowner of approximately €2600, assuming a future energy price of 0.2 €/kWh. At the current energy price level of 0.1 €/kWh energy renovation in general is almost economically neutral for the homeowner. [Copyright &y& Elsevier]

Highlights • RDE were measured over urban, rural and motorway routes with variable road grade. • Road grade greatly influences NOx and CO 2 emissions of Euro 5 diesel vehicles. • Linear and symmetric correlation was found between CO 2 and road grade. • NOx as function of road grade is best fitted by a 2th order polynomial law. Abstract On-road real driving emissions (RDE) testing was used to study the effects of many parameters not taken into account by laboratory testing but which can greatly influence vehicle pollutant emissions. Among these, road grade plays a key role. This paper investigates the effects of positive and negative road grades on the exhaust emissions of two Euro 5 diesel vehicles. Both vehicles were tested in the laboratory on the chassis dynamometer and on the road along a mixed route in Naples (Italy). The circuit includes urban, extra-urban and motorway driving in order to comply with Euro 6 RDE requirements. Laboratory testing aimed to assess emissions during current type approval driving cycles; on-road tests using portable analysers were used to determine real emissions as a function of road gradient. Vehicle Specific Power (VSP) analysis revealed that with respect to positive road grades, negative ones explain a higher share of total VSP. For −4% to +5% road gradients, the percentage variation of carbon dioxide emissions is linearly correlated with variations in slope. The same correlation for nitrogen oxides is vehicle dependent and well explained by a second-order polynomial function. [ABSTRACT FROM AUTHOR]

Highlights • World's first chemical looping pilot plant utilizing moving bed reactors. • Achieved near-full conversion of coal-derived syngas in the moving bed reducer. • Achieved 99% purity hydrogen production with in-situ carbon capture. • Validated operational results by ASPEN process simulation. Abstract Chemical looping combustion (CLC) is an advanced technology for converting fossil fuel while achieving in-situ CO 2 capture. The high purity CO generated in the combustion product stream is sequestration/utilization ready, which makes chemical looping one of the most attractive carbon emission control technology. In this paper, the authors present the design, simulation and experimental operation results of the 250 kW th high pressure syngas chemical looping (SCL) pilot plant. The pilot plant's unique countercurrent moving bed design allows near-full conversion of coal-derived syngas with simultaneous production of high purity, carbon-free H 2. Critical aspects of the design efforts, including heat and material balances, reactor sizing approach and solid flow control and measurement devices are presented. An ASPEN Plus® model is constructed to predict the gas and solid conversions of the SCL process the gas and solid conversions of the SCL process under different experimental conditions. The highest syngas conversion achieved was 97.95% with 16.03% oxygen carrier conversion, which were close to the thermodynamic limits for both the gas and solid phases in the reducer. Differences between the experimental results and predicted conversion values were more significant under conditions with lower oxygen carrier to fuel ratio. Greater than 99% purity H 2 was produced from the moving bed oxidizer, and the scalability and feasibility of SCL process were successfully demonstrated. [ABSTRACT FROM AUTHOR]

Highlights • India's emissions and intensity are driven by private consumption, followed by investment and exports. • India's emission increase comes from final demand and production structure changes. • India's increase of household indirect emissions mainly comes from per capita income increase. • India's aggregate embodied intensity by final demand category all increased. • India's aggregate embodied intensity changes mainly determine by production structure changes. Abstract India is the second largest developing country and fourth largest carbon emitter in the world. It has registered the rapid economic growth (7–9%) in the last decade. However, both its total carbon emissions and emission intensity (CO 2 emissions per GDP) kept increasing during period 2007–2013. There are few studies using input-output (I-O) analysis for India's energy/emissions in the literature. This paper tries to fill in the gap by using I-O framework to study India's total emissions and intensity changes and its driving forces with the latest data available and newly proposed techniques. The results show that India's carbon emission were mainly driven by private consumption (50–55%), followed by investment (25–26%) and exports (14–19%). During period 2007/08–2013/14, India's total emissions increased by 56.6%, where total final demand change resulted in emissions increasing and the shift of demand from raw material industry to high-value added manufacturing industry helped to reduce the emissions. When measuring India's relative emission efficiency, its aggregate embodied intensity (AEI) indicator in aggregate was mainly determined by private consumption (47–49%), followed by investment (23–24%) and exports (15–18%). From 2007/08 to 2013/14, the AEI values in aggregate and by final demand category all increased except the AEI of inventory change, mainly caused by production structure change. The emission efficiency improvements helped to reduce India's total emissions and carbon intensity, but the contributions were small. The policy implications of our findings are also discussed. [ABSTRACT FROM AUTHOR]

Highlights • Sabatier-based CO 2 methanation plant modelling and simulation. • Plant optimization through Pinch Analysis. • Sabatier conversion yield improvement. • Thermoeconomic analysis and identification of critical plant components. • Sensitivity analysis of electricity cost, CO 2 emission trades and CO 2 sequestration costs on methane cost. Abstract The present global energy scenario has to face the technical and economic challenges of the global CO 2 emissions mitigation. The two main technological paths followed are on one hand the increase of renewable share and on the other the implementation of carbon capturing and storage solutions. While the main drawback of the first one is the need to include an energy storage to compensate for the fluctuations of the sources, the one of the latter is related to the high CO 2 sequestration costs. Sabatier based power-to-gas systems are potential answers for both the above described issues. Object of this paper is the modelling, process design and simulation of a CO 2 methanation plant based on the Sabatier reaction. Since the main issue of power-to-methane storage technology is its low overall conversion efficiency, the pinch analysis approach has been applied to enhance the energy recovery that represents a key factor in the increase of the plant global efficiency. An exergy and thermoeconomic analysis of the proposed plant was performed in order to evaluate the main sources of irreversibility and to calculate the CH 4 production costs as a function of the main plant parameters. A Sabatier conversion yield of 93.48% has been obtained producing 0.42 kg of CH 4 per each kg of captured CO 2 with an improved cost of 53 €/MWh. The results of the study have shown the great potentials of this solution as an "energy storage" and CO 2 capture facility. [ABSTRACT FROM AUTHOR]

Highlights • Spatial heterogeneous impacts of households on CO 2 emissions are analyzed. • Clarify the responsibility of CO 2 emissions reduction in Chinese provinces. • Unequal impacts on CO 2 emissions among different income households are identified. • The Chinese provinces demanding high-income household specific policies are listed. • Key sectors for shrinking unequal impacts of households on emissions are identified. Abstract As unequal carbon dioxide emissions exist among households with diverse consumption patterns resulting from different income and spatial contexts, the same carbon emission reduction policies for households will go against the principle of social equality. Though a lot of attention has been paid to estimating the emissions from different income households in previous literature, the full impacts of households on carbon emissions of production sectors through changing income are not well captured. Therefore, for better supporting the fair but different carbon emission reduction policy design for households and provinces, this paper investigates the unequal impacts of households on total emissions and sectoral emissions by specifically taking into account the heterogeneity among different income households in different provinces under the empirical context of China. A combination of semi-closed input-output model and hypothetical extraction method is used here to quantify the unique effect of each income class of households. We find five aspects of seriously unequal impacts of different income households among Chinese provinces: (1) the more responsibility for reducing carbon emissions should be allocated to Shandong, Hebei, Jiangsu, Inner Mongolia, Henan, Guangdong, Shanxi and Liaoning; (2) more unequal impacts on total provincial emissions between urban and rural households in Beijing, Tianjin, Inner Mongolia, Liaoning, Jilin, Heilongjiang, Shanghai, Zhejiang, Guangdong and Chongqing; (3) unequal impacts of urban (or rural) households on total provincial emissions exist among provinces; (4) unequal impacts of households on total provincial emissions exist among income classes and among provinces; (5) unequal impacts of urban households on emissions of sectors exist among provinces. These pictures of the inequality can provide more evidence for making fair but distinguishing carbon emission reduction policies for different income households across Chinese provinces. [ABSTRACT FROM AUTHOR]

Highlights • Modeling of coal-to-liquids (CTL) process with different entrained flow gasifiers was conducted. • Thermodynamic analysis of CTL process was presented. • Locations and magnitudes of exergy inefficiencies were identified and quantified. • Techno-economic and CO 2 emissions analysis of CTL process were conducted. Abstract For the coal-to-liquids (CTL) plant, the most important unit is gasification, which determines the composition of the crude syngas, and affects CO 2 emissions and investment of the CTL process. This paper conducts a detailed plant-wide modeling of CTL process with different entrained flow gasifiers. The model is compared with the literature data. Three cases of CTL process with different entrained flow gasifiers (GSP, Shell and Texaco) are researched through thermodynamic, techno-economic and CO 2 emissions analysis. Case GSP represents the CTL process with GSP gasifier, Case Shell represents that with Shell gasifier, and Case Texaco represents that with Texaco gasifier. For a typical CTL process, Case GSP can produce FT liquids of 277.49 t/h, Case Shell can produce 246.25 t/h, and Case Texaco can provide 232.93 t/h. The energy efficiencies of Case GSP, Shell and Texaco are 50.85%, 48.18% and 41.09%, respectively. The exergy efficiencies are 49.89%, 47.20% and 40.44%, respectively. The exergy inefficiencies of the subsystem are quantified. The economic performance and CO 2 emissions of the three cases are also discussed. [ABSTRACT FROM AUTHOR]