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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 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]

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]

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]

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 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]

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]

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]

• 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]

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]

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]

• 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]

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]

Highlights • A novel adaptive pitch control strategy is proposed. • Fuel consumption, CO 2 , NO x and PM emissions are reduced. • Improved acceleration and consistently limited thermal loading is demonstrated. • The approach can save 5–15% fuel and emissions and reduce acceleration time by 30%. • No more operator input is required to switch between fast and efficient sailing. Abstract Shipping urgently needs to reduce its impact on the environment, both due to CO 2 , NO x and particulate matter (PM) emissions and due to underwater noise. On the other hand, multifunction ships such as offshore support vessels, anchor handling and towing vessels, naval vessels and wind farm construction and support vessels require fast and accurate manoeuvring and need highly reliable systems to support reduced or no crew. Diesel mechanical propulsion with controllable pitch propellers provides high efficiency and low CO 2 emissions, but has traditionally been poor in manoeuvrability, can suffer from thermal overloading due to manoeuvring and requires significant measures to meet NO x and PM emission regulations. The control strategy of diesel mechanical propulsion with fixed combinator curves is one of the causes of the poor manoeuvrability, thermal overloading and cavitation noise during manoeuvring, such as slam start and intermediate acceleration manoeuvres. This paper proposes an adaptive pitch control strategy with slow integrating speed control that reduces fuel consumption, CO 2 , NO x and PM emissions and underwater noise, improves acceleration performance, limits engine loading and prevents engine under- and overspeed. A simulation study with a validated model of a case study Holland class Patrol Vessel demonstrates 5–15% reduction in fuel consumption and CO 2 emissions, compared to the baseline transit control mode in the ship speed range from 6 to 15 kts, during constant speed sailing. Moreover, the adaptive pitch control strategy reduces acceleration time from 0 to 15 kts with the slam start procedure by 32% compared to the baseline manoeuvre control mode and by 84% for an intermediate acceleration from 10 to 15 kts, while preventing thermal overloading of the engine, during straight line manoeuvres. Combining this control strategy with hybrid propulsion, running an electric drive in parallel with the propulsion diesel engine, can potentially further reduce fuel consumption at low speeds while also improving acceleration performance even more. Therefore, hybrid propulsion plants with controllable pitch propellers and adaptive pitch control can provide a significant contribution to the urgent reduction of environmental impact of shipping and to the need for more autonomous and reliable ship systems. [ABSTRACT FROM AUTHOR]

Highlights • A new approach for design optimization of zero/low energy buildings is proposed. • The approach integrates multi-stage sensitivity analysis and design optimization. • An optimization method for buildings without heating in subtropics is developed. • Concern of winter thermal discomfort affects the selection of key design parameters. • Such concern affects the optimal design of buildings without heating in subtropics. Abstract To reduce building energy use and mitigate CO 2 emissions, zero/low energy buildings have attracted increasing attention. However, the impacts of the main design parameters and optimal design for zero/low energy buildings only provided with cooling in subtropical regions are seldom studied, and the objectives for building performance assessment and design optimization in such particular situations are not addressed sufficiently. In this study, the impacts of the main design parameters and optimal design for zero/low energy buildings in subtropical regions are studied. A holistic approach integrating sensitivity analysis and design optimization is developed for zero/low energy buildings. A new optimization objective is proposed, which considers annual energy consumption and winter thermal discomfort, for buildings without heating provision. A multi-stage sensitivity analysis approach is proposed to identify the key design parameters for design optimization. The key building design parameters are optimized to minimize the optimization objective using the genetic algorithm. A case study is conducted, using the zero carbon building (ZCB) in Hong Kong as a reference building, to illustrate the implementation steps and effectiveness of the proposed approach. This paper presents the identification of the key influential design parameters in the subtropical climate and the design optimization method of zero/low energy buildings as well as the procedures and the results of the case study. [ABSTRACT FROM AUTHOR]

Highlights • We build a model to evaluate the multi-dimensional effects of urbanization on CO 2 emissions. • We apply a balanced and stepwise city panel data model in our study. • Land urbanization and economic urbanization positively stimulate CO 2 emissions. • Population urbanization and social urbanization exert a negative impact on CO 2 emissions. Abstract Urbanization has been viewed as an important factor in soaring energy consumption and rapidly increasing CO 2 emissions, globally. While much existing literature has explored the effects of urbanization on CO 2 emissions, little work has been undertaken to examine how differences in the urbanization process itself affect the impact that urbanization has on such emissions. In order to supplement the shortness of existing literature, this paper empirically investigates the multiple effects of urbanization on CO 2 emissions, by addressing four different aspects of the urbanization process—namely, economic urbanization, population urbanization, land urbanization, and social urbanization, and expects that these four aspects of urbanization will conduct multiple effects on CO 2 emissions. A balanced city panel remote sensing and socioeconomic data and stepwise panel data model were used in the study, which examined the period of 1990–2013 in the Pearl River Delta, an economically developed region in China that has experienced rapid urbanization since the country’s economic reforms. Our empirical results show that urbanization exerts two opposing effects on CO 2 emissions: land urbanization and economic urbanization positively affects emissions due to transformation from non-built to built-up area and wealth accumulation respectively, while population urbanization exerts a negative impact on CO 2 emissions as a result of improvement in energy consumption mode and efficiency. Social urbanization decreased emissions mainly through cultivating the awareness of energy-saving. Surprisingly, the industrial structure and social consumption had positive but not significant impacts on CO 2 emissions in the Pearl River Delta. This finding suggests that urbanization, if measured by different indicators, does have different effects on CO 2 emissions. In addition, we note the remarkable positive influence of energy intensity, indicating that lower energy efficiency tends to increase emissions. Furthermore, the impact of FDI was found to be positive, and R&D was not found to have performed any significant negative effect on CO 2 emissions. These findings provide a useful insight into the relationship between urbanization and CO 2 emissions that can support policy makers and urban planners. [ABSTRACT FROM AUTHOR]

Highlights • Technoeconomic analysis of solar-assisted chemical looping plants is performed. • Exhaust heat utilization can significantly improve the CLC system efficiency. • Cooling by absorption chilling process results in better system performance. • Cost of electricity is very sensitive to the fuel cost. • Solar-assisted CLC plants are economically more feasible at high fuel cost. Abstract Chemical looping combustion (CLC) is a promising technique for CO 2 capture with low energy penalty and low cost. In addition to capturing CO 2 , the solar-assisted CLC process results in the production of significant amount of exhaust waste heat which could be utilized for a variety of purposes. This paper outlines a detailed techno-economic analysis of a solar-assisted natural gas fired CLC power plant with waste heat utilization for absorption chilling purpose. This is particularly important for hot regions such as the United Arab Emirates (UAE) where a significant amount of energy is used for cooling purposes. The power plant studied is about 550 MWe net output power. The study was conducted by developing an Aspen Plus system model. The model was used to calculate the heat recovery efficiency, the absorption chilling system coefficient of performance and the plant efficiency. The economic performance of the plant was analyzed by calculating the cost of electricity, the return on investment and the cost of CO 2 capture. The analysis shows that the poly-generation solar-assisted CLC system had a plant efficiency of 63.4%, waste heat utilization of 49%, electricity cost of 4.9 cents/kWh and the return on investment of 3.98 years at prevalent prices of the plant input materials and a capacity factor of 85 percent. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The phase splitting occurred upon CO 2 absorption into DETA/sulfolane hybrid. • Most of the absorbed CO 2 was concentrated in the upper layer and the lower layer was sulfolane. • DETA/sulfolane achieved an absorption rate 100% higher than that of MEA. • DETA/sulfolane-based process reduced the heat duty by 19% compared with MEA. • The viscosity of DETA/sulfolane was over 20 times lower than the other phase splitting absorbents. Abstract The phase splitting solvent as a promising alternative to MEA for CO 2 capture has received an increasing attention due to its low energy consumption. In this paper, the mixture of diethylenetriamine (DETA) and sulfolane was employed to absorb CO 2 from the simulated flue gas. Its phase splitting behavior was investigated. The species in each separated phase were identified using nuclear magnetic resonance (NMR), revealing that the upper layer was a CO 2 -rich phase and mainly consisted of DETA and DETA-carbamate. Whereas, the lower layer was CO 2 -lean phase with the sulfolane presented individually. The CO 2 absorption kinetics was also measured in a wetted-wall column as a function of temperatures, CO 2 loadings, and gas flow rate. Their impacts on the enhancement factor and mass transfer resistance were calculated by the Vapor-Liquid Equilibria (VLE) model, implying that the main CO 2 mass transfer resistance gradually transferred from the gas side to the liquid side with the CO 2 loading increasing from 0 to 2.21 mol L−1. During the CO 2 absorption process, sulfolane acted as an inert solvent for substituting the role of water and separated from the absorption product. Consequently, the sensible heat and vaporization heat were substantially decreased by 59% and 12%, respectively. Hence the total heat duty was lowered by 19% which might noticeably advance the CO 2 capture technology. [ABSTRACT FROM AUTHOR]

Highlights • Major losses include thermodynamic, kinetic and electrical aspects. • Acid-base interface for the specific setting of a PMEC is simulated. • The elevated reactor performance is validated experimentally and numerically. Abstract This paper reports a mathematical model for calculating various losses in a pH differential microfluidic electrolytic cell (PMEC) for CO 2 to formic acid conversion. The microfluidic characteristics of the cell were examined, and in respect of electro-chemical equilibrium states, major limiting factors such as mass transfer constraints, kinetic losses and overpotentials, were considered and acid–base interface and neutralisation losses therein identified. Losses of electrical resistance on electrodes and within micro-channels were quantified, and computational results were validated against previous experimental data. To the best of our knowledge, the model is the first for determining dual electrolyte arrangements and associated losses and can be used to develop parametric optimisation strategies. [ABSTRACT FROM AUTHOR]

Highlights • Experiment in a power generation system with CO 2 transcritical power cycles (T-CO 2 ). • Preliminary test results from the T-CO 2 power generation system. • Model development and validation of the tested T-CO 2 power generation system. • Some important operating parameters on system performance are identified. • The research outcomes can be used to instruct the system control and operation. Abstract Globally, there are vast amounts of low-grade heat sources from industrial waste and renewables that can be converted into electricity through advanced thermodynamic power cycles and appropriate working fluids. In terms of the working fluid’s environmental impact, temperature match of cycle heat processes and system compactness, CO 2 transcritical power cycles (T-CO 2 ) were deemed more applicable for low-grade heat to power conversion. However, the system thermal efficiency of a T-CO 2 requires further improvement. Subsequently, a test rig of the small-scale power generation system with T-CO 2 power cycles was developed with essential connected components. These include a plate thermal coil CO 2 supercritical heater, a CO 2 transcritical turbine, a plate recuperator, an air-cooled finned-tube CO 2 condenser and a CO 2 liquid pump. Various preliminary test results from the system measurements are demonstrated in this paper. Meanwhile, the system model has been developed and applied to predict system performance at different operating conditions. The simulation results can therefore instruct further design and optimisation of system and components. [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]

• A novel decarbonization concept applied to offshore natural gas wells benefiting CCUS technology. • A comprehensive CFD model considers real gas EOS and the behaviours of gas, droplets, liquid film. • Compatible with pure CO 2 and CH 4 -CO 2 models to study condensation and separation characteristics. • The maximum CO 2 condensation amount under high pressure and low temperature is 10.33 ton/h. • The maximum CO 2 capture capacity is 4.43 ton/h with high heterogeneous droplet mass concentration. Carbon capture, utilisation and storage (CCUS) is of unique significance for building a green and resilient energy system, and it is also a key solution to tackle the climate challenge. The concept of supersonic decarburization, a joint product of non-equilibrium condensation and swirling separation, can contribute to CCUS technology in a clean way. In this paper, a numerical model is established and validated to investigate the complex physical phenomena of supersonic decarbonization in a high-pressure environment based on the real gas equation of state. The model is compatible with the pure CO 2 model and CH 4 -CO 2 model. Through the simulation of the supersonic nozzle and supersonic separator, the condensation and separation performance of supersonic decarbonization technology was evaluated. For the condensation performance of carbon dioxide, the results show that higher pressure makes it much easier to achieve the condensation process. When the pressure is supercritical, the decrease of inlet temperature or the increase of inlet mole fraction of CO 2 leads to a higher liquid fraction. For separation performance, when the mass concentration of inlet heterogeneous droplets increases from 0.1 kg/m3 to 7.5 kg/m3, the carbon separation amount increases from 3.33 ton/h to 4.43 ton/h, while the exergy loss of condensed CO 2 drops from 436.57 kJ/kg to 329.56 kJ/kg. It demonstrates that the decarburization process is easier, and exergy required for condensation decreases when the concentration of the foreign core is larger. This new concept is beneficial to CCUS technology and can be applied to carbon capture in offshore natural gas processing. [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]

Understanding the thermophysical properties for mixtures of CO 2 and hydrocarbons at reservoir conditions is very important for the correct design and optimization of CO 2 -enhanced oil recovery and carbon storage in depleted oil or gas fields. In this paper, we present a comprehensive thermodynamic study of the prototype system (CO 2  + n-heptane) comprising highly-accurate measurements of the saturated-phase densities, compressed-fluid densities, and bubble and dew points at temperatures from 283 K to 473 K and pressures up to 68 MPa over the full range of composition. We use these results to examine the predictive capability of two leading thermodynamic models: the Predictive Peng-Robinson (PPR-78) equation of state and a version of the Statistical Associating Fluid Theory for potentials of the Mie form, known as SAFT-γ Mie. Both of these models use group contribution approaches to estimate interaction parameters and can be applied to complex multi-component systems. The comparison shows that both approaches are reliable for the phase behavior. Neither model is entirely satisfactory for density, with each exhibiting absolute average relative deviations (AARD) from the experimental data of about 4% for the saturated-phase densities and 2% for the compressed-fluid densities; however, SAFT-γ Mie is found to be much more accurate than PPR-78 for the compressibility, with an overall AARD of 6% compared with 18% for PPR-78. [ABSTRACT FROM AUTHOR]

Fluidised bed (FB) technology can be advantageously used for the gasification of solid fuels. Calcined carbonate materials, such as limestone or dolomite, can be used directly in the fluidised bed of the gasification reactor to reform tars in situ and to enhance carbon conversion and cold gas efficiency of the gasification process. However, they exhibit poorer mechanical stability, they tend to be attrited and carried over from the reactor, and their catalytic activity decreases over time. Therefore, a portion of the material has to be replenished continuously or periodically. To decrease the amount of carbonate material that has to be replenished, a lower amount of lime (calcined limestone or dolomite) can be used in the FB, diluted by a mechanically robust material, such as silica sand or olivine. According to the literature, even concentrations in the order of 10–35% wt. of carbonate material in the FB of silica sand have a substantial effect on the decomposition of tars during steam or air gasification. However, the effect of the concentration of lime in the FB has not yet been described for CO 2 gasification. In this paper, we focus on the effect of the ratio of calcined dolomitic limestone and silica sand in the FB (0%, 25%, 50% and 100% vol. of dolomitic limestone) for CO 2 +O 2 gasification of biomass and compare it with H 2 O+O 2 gasification at the temperature of 850 °C. The experiments were performed in a semi-autothermal spouting FB reactor, gasifying 1.4 kg h −1 of woody biomass. The effects of the concentration of dolomitic lime in the fluidised bed differed for H 2 O+O 2 and CO 2 +O 2 gasification. When gasifying with H 2 O+O 2 , optimal results were found with 50% vol. (35% wt.) lime in the FB, when the yield of tar was similar to the use of pure lime in the FB. When gasifying with CO 2 +O 2 , a substantial decrease in tar yield was observed when using 50% vol. (35% wt.) lime in the FB (compared to the use of pure silica sand); nevertheless, the use of undiluted lime in the FB remains the best option to attain minimal tar yield when gasifying with a CO 2 +O 2 gasifying agent. In this case, the tar yield was decreased 8.7-fold, and the tar dew point was decreased by 124 °C (to 71 °C) compared to the non-catalysed case with silica sand being the fluidised bed of the gasifier. [ABSTRACT FROM AUTHOR]

The paper is focused on the development and techno-economic assessment of a sustainable process for the production of valuable hydrocarbons from CO 2 and H 2 O. With help of process modeling tools an advantageous and highly integrated process design is identified. The application of co-electrolysis for direct syngas production as well as the implementation of advanced heat integration concepts allow for an energetic efficiency of η en  > 0.6. Additionally, the amount of reactors and heat exchangers in the proposed process is reduced in comparison to other Power-to-X concepts. The high efficiency and the focus on valuable products like waxes is also beneficial for the economic feasibility of the process. The implications of product value as well as availability and costs of renewable electricity are discussed in the context of a potential market entry of Power-to-X technologies. [ABSTRACT FROM AUTHOR]

Reducing local and global emissions is one of the drivers behind the promotion of renewable energy technologies (RETs). Some RET projects (e.g. solar, marine power, and some biomass and wind) usually require supplemental income from carbon credits in order to make them economically viable. This paper presents the mathematical development of nodal marginal CO 2 emission metrics for hydrothermal systems. These metrics are obtained from optimal power flow and hydrothermal dispatch models considering hydro uncertainty. The proposed model allows a more accurate assessment of the emission reduction effect of RET projects and the provision of efficient carbon signals to the system. Modeling of hydro reservoirs and intertemporal constraints also allows incorporating the emission mitigation potential of water storage. The concepts of marginal CO 2 emissions for hydrothermal systems are first exemplified using a small test system, and then simulations on a real hydrothermal system illustrate how these metrics can inform investment and operational decisions. Theoretical and simulation results show that transmission and hydro storage constraints neglect may provide wrong signals for RET investors, missing the incentives to install in areas where the potential for emissions reduction is higher (where renewable energy displaces a larger amount of coal or diesel). Policy makers can use the proposed model to assess the cost-effectiveness of emission reduction policies. [ABSTRACT FROM AUTHOR]

The incidence of climate change policy is of great interests to economists, policy makers, producers and consumers. Using the daily market data for a 65-month period of 01/01/2011–05/31/2016, this empirical paper documents that the California Independent System Operator’s day-ahead prices have a CO 2 premium approximately equal to natural-gas-fired generation’s marginal cost of CO 2 emissions. This finding prevails in the six time-of-day periods developed to match the pricing periods used by the state’s local distribution companies and the bilateral trading of wholesale electricity in the Western Interconnection, a large electricity grid serving the western portion of North America and a Mexican state. Our findings suggest that the California cap-and-trade (C&T) program is effective in internalizing CO 2 emission costs of the in-state natural-gas-fired generation. However, the program’s economic efficiency is compromised by the unintended consequence of power laundering under inter-regional trading of wholesale electricity. While the program encourages the Pacific Northwest’s hydro export that displaces California’s natural-gas-fired generation, it also induces output increases by non-California coal- and natural-gas-fired generators in the Western Interconnection. Hence, reducing the overall CO 2 emissions in the Western Interconnection requires expanding the program’s geographic scope to meaningfully address the global warming problem. [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]

The primary objective of the study presented in this paper was a thermodynamic and ecological analysis of coal-fired power plants integrated with carbon dioxide capture installations working in different technologies (pre-combustion, oxy-combustion and post-combustion) and a comparison of these systems with reference systems, i.e. ones not-integrated with CO 2 capture. Calculations were performed using our own developed mathematical models for the integrated units. The article quantitatively demonstrates that the integration of a carbon dioxide capture installation with a power plant causes a significant decrease in the net power and efficiency in relation to the reference system (without capture). In the case of a conventional coal unit working in the post-combustion technology and integrated with an absorption CO 2 capture installation and compression of carbon dioxide to 15 MPa, the net efficiency decreases in relation to the reference plant by 11.75 percentage points. The oxy-combustion unit was characterized by a decrease in efficiency (in relation to the power plant operating in the air combustion technology not integrated with Carbon Capture and Storage (CCS) installation) equal to 7.85 percentage points. In the unit working in pre-combustion technology (Integrated Gasification Combined Cycle (IGCC) system) integrated with a membrane CO 2 separation installation the efficiency decrease relative to the unit without capture was equal to 16.89 percentage points. The main advantage of those systems integrated with carbon dioxide capture installations is the significant reduction of emissions to the atmosphere (environmental effect). This effect significantly depends on the separation method and the obtained effect of separation. Implementation of the capture plant in the analyzed post-combustion system allowed for a reduction of the value of the average annual CO 2 emission rate aggravating unit of net electricity produced from nearly 735 kg CO 2 /MWh to 100.77 kg CO 2 /MWh. In the case of the unit working in IGCC technology integrated with membrane CO 2 capture, this rate was equal to 89 kg CO 2 /MWh. The lowest value was obtained for the power plant working in oxy-combustion technology, for which the emission rate was obtained at 19 kg CO 2 /MWh. [ABSTRACT FROM AUTHOR]

This paper presents an integrated numerical framework to co-optimize EOR and CO 2 storage performance under uncertainty in the Farnsworth Unit (FWU) oil field in Ochiltree County, Texas. The framework includes a field-scale compositional reservoir multiphase flow model, an uncertainty quantification model and a neural network optimization process. The reservoir flow model has been constructed based on the field geophysical, geological, and engineering data. Equation of state parameters were tuned to achieve field measured fluid properties and subsequently used to predict the minimum miscible pressure (MMP). A history match of primary and secondary recovery processes was conducted to estimate the reservoir and multiphase flow parameters as the base case for analyzing the effect of recycling produced gas, infill drilling and water alternating gas (WAG) cycles on oil recovery and CO 2 storage. A multi-objective optimization model was defined for maximizing both oil recovery and CO 2 storage. The uncertainty quantification model comprising the Latin Hypercube sampling, Monte Carlo simulation, and sensitivity analysis, was used to study the effects of uncertain variables on the defined objective functions. Uncertain variables include bottom hole injection pressure, WAG cycle, injection and production group rates, and gas-oil ratio. The most significant variables were chosen as control variables to be used for the optimization process. A neural network optimization algorithm was utilized to optimize the objective function both with and without geological uncertainty. The vertical permeability anisotropy (Kv/Kh) was selected as one of the uncertain parameters in the optimization process. The simulation results were compared to a scenario baseline case that predicted CO 2 storage of 74%. The results showed an improved approach for optimizing oil recovery and CO 2 storage in the FWU. The optimization model predicted that about 94% of CO 2 would be stored and most importantly, that this increased storage could result in about 25% of incremental oil recovery. The sensitivity analysis reduced the number of control variables to decrease computational time. A risk aversion factor was used to represent results at various confidence levels to assist management in the decision-making process. The defined objective functions were shown to be a robust approach to co-optimize oil recovery and CO 2 storage. [ABSTRACT FROM AUTHOR]

Oxy-fuel combustion is one of the routes to have carbon dioxide as the main component of the combustion products stream, enabling carbon capture and sequestration. However, oxy-fuel combustion presents challenges in terms of higher temperatures and flame speed, dictating the need for dilution using entrainment of non-reactive diluents. This need for dilution presents opportunities for developing oxy-fuel combustion using distributed combustion technique. Distributed combustion has been investigated in different configurations and geometries, demonstrating near zero emissions, uniform thermal field and much reduced combustion noise. Key element to achieve distributed combustion is mixture preparation with controlled entrainment of hot reactive species from within the combustor and their subsequent mixing with the fresh reactants to form reduced oxygen concentration-high temperature oxidizer to achieve distributed combustion in the combustor. This necessary entrainment can be beneficial in oxy-fuel combustion as it satisfies the need to utilize CO 2 back into the reaction zone for dilution. In this paper, distributed combustion was investigated with focus on oxy-methane combustion. Experiments were performed on a swirl flame combustor with oxygen concentration ranging between 40 and 21% of the oxidizer mixture. Results showed the possibility of achieving distributed combustion using oxy-fuel combustion. This is demonstrated through OH ∗ chemiluminescence wherein the reaction zone extended to cover larger portion of the combustor as opposed to that of a traditional swirl flame. Emissions measurements showed the elimination of NO emission with low CO emissions, demonstrating the benefits of incorporating distributed combustion concept using oxy-fuel combustion for carbon capture with the product stream containing mostly CO 2 . [ABSTRACT FROM AUTHOR]

[Display omitted] • We propose a multi-lateral horizontal well with a dual-tubing (MLHW-DT) system to improve CO 2 storage security and reduce CCS cost. • The MLHW-DT reinjects produced brine to enhance the horizontal CO 2 flow more than the typical CCS with brine extraction. • The MLHW-DT system outperforms other CO 2 injection/brine production systems in terms of CO 2 storage security and CCS cost. • This study suggests that operating an onshore MLHW-DT system is effective for a small-to-mid scale saline aquifer. This paper proposes a multi-lateral horizontal well with a dual-tubing (MLHW-DT) system to improve CO 2 storage security and reduce the cost of carbon capture and storage (CCS) at a saline aquifer. In CCS, the production and re-injection of brine are efficient methods of relieving overpressure and improving the CO 2 storage security simultaneously. In our previous study, a horizontal well with a dual-tubing (HW-DT) system operating on an onshore platform reduced CCS cost. In this study, the proposed MLHW-DT system is designed to implement the concept of the re-injection of produced brine to improve CO 2 storage security while supplementing the shortcomings of the conventional brine production system by reducing CCS cost. When we vary the vertical-horizontal permeability ratio and dip angle of a saline aquifer, the CO 2 storage security of the MLHW-DT system is improved compared with that of the overall HW-DT system because the re-injected brine induces the CO 2 plume migration in the lateral direction. Furthermore, the CCS cost of the MLHW-DT system is reduced by 69.4% compared with that of the conventional brine production system if the MLHW is operated on an onshore platform. Based on these results, the MLHW-DT is a safe and economical operation system for a CCS project. [ABSTRACT FROM AUTHOR]

• The proposed proactive 2-stage demand-controlled ventilation (P2S-DCV) method improves the DCV performance. • A deep neural network -based prediction model is proposed to predict future indoor CO 2 and applies ventilation control in advance. • A reinforcement learning-based method is proposed to achieve accurate and rapid airflow control. • The fan pressure and damper positions are optimized to minimize energy consumption. • The proposed P2S-DCV method has good generalization ability under various conditions. This paper presents a novel method, named proactive 2-stage demand-controlled ventilation (P2S-DCV) method, to maintain indoor air quality (IAQ) and reduce the energy consumption of multi-zone ventilation systems. The proposed P2S-DCV method applies a proactive control scheme, which predicts future indoor CO 2 concentration and supplies proper ventilation to each zone. The method includes two stages. In Stage I, a DNN prediction model is established to predict the future CO 2 concentration to calculate the corresponding demand airflow. In Stage II, a reinforcement learning method is designed to achieve rapid and accurate control, and further reduce the energy consumption by optimizing the fan pressure and damper positions. A 5-zone ventilation system is established to validate the proposed P2S-DCV method. The experiment verifies that: a) it can maintain comfortable IAQ via predicting the change of future indoor CO 2 and applying effective ventilation control in advance; b) it can improve the control performance, the accuracy is maintained within 8 % (satisfied the ASHRAE Standards), and the control time is maintained within minutes. It can reduce the regulating time by 83.62 % compared with ASHRAE Ratio method, and up to 51.68 % compared with PID method; c) it can reduce the fan energy consumption by 16.4 % compared with ASHRAE Ratio method, and up to 21.8 % compared with PID method; d) it has good generalization ability for various IAQ requirements and ventilation systems with different topologies. [ABSTRACT FROM AUTHOR]

This paper quantifies the impacts of policy objectives on the composition of an optimum new passenger vehicle fleet. The objectives are to reduce individually absolute energy use and associated emissions of CO 2 , NO x and PM 2.5 . This work combines a top down, diversity-led approach to fleet composition with bottom-up models of 23 powertrain variants across nine vehicle segments. Changing the annual distance travelled only led to the smallest change in fleet composition because driving less mitigated the need to shift to smaller vehicles or more efficient powertrains. Instead, managing activity led to a ‘re-petrolisation’ of the fleet which yielded the largest reductions in emissions of NO x and PM 2.5 . The hybrid approach of changing annual distance travelled and increasing willingness to accept longer payback times incorporates management of vehicle activity with consumers’ demand for novel vehicle powertrains. Combining these changes in behaviour, without feebates, allowed the hybrid approach to return the largest reductions in energy use and CO 2 emissions. Introducing feebates makes low-emitting vehicles more affordable and represents a supply side push for novel powertrains. The largest reductions in energy use and associated emissions occurred without any consumer behaviour change, but required large fees (£79–99 per g CO 2 /km) on high-emitting vehicles and were achieved using the most specialised fleets. However, such fleets may not present consumers with sufficient choice to be attractive. The fleet with best diversity by vehicle size and powertrain type was achieved with both the external incentive of the feebate and consumers modifying their activity. This work has a number of potential audiences: governments and policy makers may use the framework to understand how to accommodate the growth in vehicle use with pledged reductions in emissions; and original equipment manufacturers may take advantage of the bottom-up, vehicle powertrain inputs to understand the role their technology can play in a fleet under the influence of consumer behaviour change, external incentives and policy objectives. [ABSTRACT FROM AUTHOR]