International Journal of Green Energy

This paper discusses the performance investigations of a single-stage metal hydride heat pump (SS-MHHP) working with five different alloy pairs, namely, MmNi4.6Al0.4/MmNi4.6Fe0.4, LaNi4.61Mn0.26Al0.13/La0.6Y0.4Ni4.8Mn0.2, LmNi4.91Sn0.15/Ti0.99Zr0.01V0.43Fe0.09Cr0.05Mn1.5, LaNi4.6Al0.4/MmNi4.15Fe0.85 and Zr0.9Ti0.1Cr0.9Fe1.1/Zr0.9Ti0.1Cr0.6Fe1.4. The performance of the system is predicted by solving the unsteady, two-dimensional coupled heat and mass transfer processes in metal hydride bed of cylindrical configuration using a fully implicit finite volume method. The influences of operating temperatures such as heat source (TH), heat sink (TM) and refrigeration (TC) temperatures on the coefficient of performance (COP) and specific cooling power (SCP) of the system are presented. The predicted hydride bed temperature profiles are compared with the experimental data reported in the literature and a reasonably good agreement is observed between them. The optimum operating temperature ranges of each pair of alloys are suggested. For the selected operating temperatures, a maximum COP of 0.66 is predicted for Zr0.9Ti0.1Cr0.9Fe1.1/Zr0.9Ti0.1Cr0.6Fe1.4 hydride pair, while LmNi4.91Sn0.15/Ti0.99Zr0.01V0.43Fe0.09Cr0.05Mn1.5 hydride pair produces the highest SCP of 53.25 W/kg of total mass of the system.

Accurate prediction of short-term wind power generation is of great importance for wind farm operation, the balance of power grid load, and the optimization of bidding strategy on spot market. In general, wind power generation can be predicted using either direct prediction or indirect prediction approaches. The direct approach is to develop a forecasting model based on the historical wind power generation and then predict the future power generation. The indirect approach is to first obtain a wind speed forecasting model, make the prediction of future wind speed, and then convert wind speed forecast to wind power forecast based on the power curve of a wind turbine. This research compares the performances of the two approaches based on the wind speed and power production data of an offshore 2-MW wind turbine. The mature autoregressive integrated moving average (ARIMA)-family forecasting models are adopted for both approaches. In obtaining the forecasting models, no seasonality is found for both wind speed and wind power generation because of the relative short time span of data collection. Therefore, autoregressive and autoregressive moving average models, i.e., the simplified ARIMA models, turn out to be sufficient. The comparison shows that the direct approach produce significantly more accurate forecasts compared with the indirect approach in terms of both mean absolute error and root mean square error. The main reason is that the power curve only considers the averaged deterministic relationship between wind speed and power generation, while in reality the relationship is stochastic in nature. This variability leads to the lower accuracy in predicting wind power generation using the indirect approach.

This paper attempts to apply Reistad's approach to analyze exergy utilization in Chinese transportation sector that includes five sub-sectors: highways, railways, waterways, airways, and pipeline transport. Unlike previous studies based on historical data, this paper uses the actual data for 2006 and projected data for 2030 under five scenarios to analyze exergy consumption. We find that (1) in 2030, the total exergy consumption will be 17,883-26,698 PJ, which may increase 2.26-3.78 times compared with that in 2006. (2) The effect of advanced technology is much greater than that of the choice of transport mode. (3) Highways will always be the dominant transport mode. In 2030, the percentage of exergy of oil fuels in total exergy consumption of the whole sector will account for more than 97%. (4) The weighted mean energy and exergy efficiencies will show a deteriorating trend over years, i.e., a decreasing tendency with time, except for Scenario 2.

Worldwide energy demand has been growing steadily during the past five decades and most experts believe that this trend will continue to rise. The amount of emitted harmful emission gases increases in parallel with increasing energy consumption. This increase has forced many countries to take various precautions, and various restrictions on emitted emissions have been carried. In this study, effects of addition of oxygen containing nanoparticle additives to biodiesel on fuel properties and effects on diesel engine performance and exhaust emissions were investigated. Two different nanoparticle additives, namely MgO and SiO2, were added to biodiesel at the addition dosage of 25 and 50 ppm. Fuel properties, engine performance, and exhaust emission characteristics of obtained modified fuels were examined. As a result of this study, engine emission values NOx and CO were decreased and engine performance values slightly increased with the addition of nanoparticle additives.

Biomass has the potential to replace a wide variety of fossil-based products within the energy sector: heat, power, fuels, materials, and chemicals. It is considered sustainable and renewable, yet in all the potential applications for biomass, direct and indirect fossil derived inputs are required. Investigating the best possible utilization options for biomass necessitates life-cycle thinking to determine the amount of fossil fuel energy replaced in each system. The methodology and significance of using an energetic and exergetic cradle-to-factory gate assessment is described for common biomass crop production routes and biorefinery layouts using Dutch sugar beet as an expletory crop. Preliminary results indicate that the optimal utilization for biomass is for chemical biorefinery concepts

Bioenergy is considered an option of significant potential for both industrialized and developing countries and its exploitation can strive toward more sustainable energy systems. In this framework, the main scope of this paper is an analysis of three bioenergy options, namely biomass combustion, biomass gasification, and production of biofuels for the transport sector, in terms of their status, benefits, and possible barriers, as well as their future potential. Special attention is given to the perspectives for deployment in the developing world in the context of emerging opportunities provided by the clean development mechanism for sustainable technology transfer.

Sustainable ecosystems can be designed to eliminate environmental toxins and reduce pathogen loads through the direct and indirect consequences of plant and microbial activities. We present an approach to the bioremediation of disturbed environments, focusing on petroleum hydrocarbon (PHC) contaminants. Treatment consists of incorporating a plant-based amendment to enhance ecosystem productivity and physiochemical degradation followed by the establishment of plants to serve as oxidizers and foundations for microbial communities. Promising amendments for widespread use are entire plants of the water fern Azolla and seed meal of Brassica napus (rapeseed). An inexpensive byproduct from the manufacture of biodiesel and lubricants, rapeseed meal is high in nitrogen (6% wt/wt), stimulates >100-fold increases in populations of resident Streptomyces species, and suppresses fungal infection of roots subsequently cultivated in the amended soil. Synergistic enzymatic and chemical activities of plant and microbial metabolism in root zones transform and degrade soil contaminants. Emphasis is given to mechanisms that enable PHC functionalization via reactive molecular species.

In this study an optimisation method for the design of combined solar and pellet heating systems is presented and evaluated. The paper describes the steps of the method by applying it for an example system. The objective of the optimisation was to find the design parameters that give the lowest auxiliary energy (pellet fuel + auxiliary electricity) and carbon monoxide (CO) emissions for a system with a typical load, a single family house in Sweden. Weighting factors have been used for the auxiliary energy use and CO emissions to give a combined objective function. Different weighting factors were tested. The results show that extreme weighting factors lead to their own minima. However, it was possible to find factors that ensure low values for both auxiliary energy and CO emissions, and suitable weighting factors are suggested.

This study examines parametric approaches to the calculation of refrigerant-based CO2 emissions in different cooling areas. Both the exergy analyses of refrigerants, used in domestic, commercial, transportation and industrial applications, and the environmental performances regarding exergetic irreversibility are investigated separately. Then, CO2 emissions caused by systems are examined via two different parameters, I°) Environmental Impact Factor and ıı°) Integrated Impact Factor (CIF). The study is based on a vapor compression cooling cycle model, commonly preferred by cooling applications, and the analyses have been made for 1 kW cooling capacity in relation to evaporator temperatures of the systems. In all cooling application, R134A gas stands out among the others in terms of coefficient of performance and exergy efficiency. Moreover, both emission analyses show that it has the lowest emission value. The paper concludes with an evaluation of the reasons for the refrigerant choice, the design and the selection of such a system, and why exergetic and environmental parameters should be preferred.

This study examines energetic and exergetic performances of display cases’ units used in market applications depending on different refrigerants. Besides CO2 emission potential of each refrigerant based on exergetic irreversibility obtained from analyses is calculated by the method of Total Equivalent Warming Impact (TEWI). In this study, 1 kW cooling capacity and vapor compression cooling cycle is taken as reference and refrigerants of R-22, R-134a, R-404A, and R-507 together with alternative refrigerant R-407C and R152a are examined separately. According to analyses, R-404A gas, used widely in market applications, has low performance with average COP 3.89 and average exergy efficiency 55.20%. R-152a gas has the best performance by the thermodynamics parameters including COP 4.49, exergy efficiency 63.79%, and 0.23 kW power consumption and emission parameter 14097.490 ton CO2/year. Although COP is used as a criterion to evaluate the systems, this study finally emphasizes the importance of exergy analysis and TEWI method which are important methods to determine irreversibility and emission potential of the systems.

Considering the increased trend to use renewable energy to meet electrical energy demands, a reliable performance also should be adopted in transmitting the generated power through the stable transmission and subtransmission systems for which nowadays Flexible AC Transmission System (FACTS) controllers are used extensively. Transient stability is one of the most important issues in power system stability analysis. FACTS devices have confirmed their capabilities in various aspects in power networks. In this paper, to improve transient stability of power systems, a shunt connected FACTS devices have been introduced, i.e., Static VAR compensators (SVCs). The SVC has the most diversified branches among FACTS devices. The main aim of this work is to study and analyze the impact of eight branches of SVC on improvement of transient stability and to choose the best of them. Simulations are performed in MATLAB/SIMULINK environment.

Turkey has a drastic potential in terms of biomass energy and it would be of utmost importance for our energy mix if this huge amount of energy is to be utilized. Thermochemical conversion is the most dominant one among the energy conversion processes. The carbonization process is the key point in determining the kinetic parameters of the fuels utilized. Thereafter, the kinetic parameters obtained from carbonization would be utilized in designing the thermochemical conversion equipments. In this study, the thermal decomposition behavior of hazelnut shells was investigated via dynamical thermogravimetry (TG) under N2 atmosphere. In order to determine the effects of heating rate and gas flow rate, the experiments were performed in four different heating rates of 5, 20, 50, and 100 K/min and two different nitrogen flow rates of 50 and 100 cm3/min. As the heating rate was increased, peak temperature was increased, maximum temperature shifted to the right (higher T zones) and the maximum rate of weight loss was increased. In addition, lignin decomposition temperature interval was decreased whereas; cellulose decomposition temperature interval was increased. Increasing the heating rate from 5 to 20 K/min, hemicellulose decomposition temperature interval was increased. Total weight loss was slightly increased by the increase of gas flow rate. Kinetic parameters were calculated according to Coats Redfern method. It was found that activation energies of thermal decomposition reactions of hazelnut shell varied between 1.30 and 32.19 kJ/mol.

In this paper, membrane electrode assemblies were constructed using catalyst-coated membranes to investigate proton-exchange membrane fuel cell water flooding. Two major fuel cell hardware variations, namely flowfield design and Teflon loading of the gas diffusion layer (GDL), were tested to explore their effects on water flooding. A flowfield with triple serpentine flow channels showed heavier water flooding than that with single serpentine flow channels. Increasing the Teflon loading in the GDL reduced water flooding effectively. Several fuel cell operating conditions, including air stoichiometry, current density, relative humidity (RH), backpressure, and temperature, were also tested to identify their effects on water flooding. It was observed that the water flooding severity increased with decreasing air stoichiometry, as well as with increasing temperature, RH, backpressure, and current density. Among these operation conditions, air stoichiometry (or air flow rate) and RH played more important roles in reducing water flooding. yes yes

Large amounts of free fatty acids in oil used for the production of biodiesel cause the problems of soap formation and very low yield of biodiesel. To overcome these problems, free fatty acids must be esterified to their esters in the presence of an acid catalyst prior to alkaline-catalyzed transesterification. Sulfated metal oxides are an interesting group owing to their very high acidity. In this study, sulfated aluminium-tin mixed oxide (SO42−/Al2O3-SnO2) catalysts were synthesized and used for esterification of free fatty acids in crude palm oil for the first time. The SO42−/Al2O3-SnO2 catalysts were prepared from different Al precursors, calcination temperatures, and sulfate concentrations. Characterization of the catalysts included X-ray diffraction (XRD) and X-ray fluorescence (XRF) techniques, nitrogen adsorption, Fourier transform infrared spectroscopy (FTIR), and potentiometric titration. The results show that the SO42−/Al2O3-SnO2 catalyst has very strong acid sites. Different Al precursors lead to different activities of the SO42−/Al2O3-SnO2 catalysts. Al2(SO4)3 is the best precursor whereas Al(NO3)3 is the worst one to prepare the SO42−/Al2O3-SnO2 catalyst. The optimum calcination temperature is 450°C. The activity of the SO42−/Al2O3-SnO2 catalyst increases with sulfate concentration. Introducing Al2O3 to SO42−/SnO2 increases its stability during the reusability process. Therefore, SO42−/Al2O3-SnO2 is a better candidate than SO42−/SnO2 for catalyzing the esterification of free fatty acids in crude palm oil.

Energy needs are mainly covered by fossil fuels leading to pollutant emissions, mostly responsible for global warming. Among the different possible solutions for the greenhouse-effect reduction, hydrogen has been proposed for energy transportation. Hydrogen can be seen as a clean and efficient future energy carrier. However, the major challenges regarding hydrogen energy is its storage. Of the known methods for hydrogen storage (compressed gas, cryogenic liquid, and metal hydrides), metal hydrides offer the best compromise considering both safety and efficient storage capacity. In this study, a nano structured V–Ni alloy has been synthesized by using high-energy ball milling route. The synthesized alloy is characterized by scanning electron microscope, energy dispersive spectrometer, and X-ray diffraction tools. The mean particle size of this alloy is measured as 12.5 ± 2.90 μm, and the crystallite size is computed as 8.75 ± 0.54 nm. The hydriding–dehydriding characteristics of this alloy are studied using Sievert's principle. The maximum hydrogen absorption in the synthesized V–Ni alloy is measured as 1.92 mass% at only 83°C charging temperature, and release of 1.04 mass% of H2 at discharging temperature of 210°C.

The study presents the results of investigations carried out on a four-cylinder, four-stroke, direct injection diesel engine operated with tea seed (Camellia sinensis) oil biodiesel. The oil from tea seeds was extracted from grounded seeds using the Soxhlet extraction apparatus. The biodiesel was produced by transesterification of tea seed oil with methanol in the presence of a catalyst (NaOH). After being blended with regular diesel fuel (D), the fuel properties of tea seed biodiesel (B) was determined according to ASTM and EN standards. The fuel mixtures (biodiesel content at the volumetric ratios of 10%B–90%D (B10), 20%B–80%D (B20), and 100%B (B100)) were tested in a direct injection diesel engine at full load condition. The results indicated a decrease in the observed power output with the increase in biodiesel content in the mixture. Specific fuel consumption (SFC) values were increased depending on the amount of biodiesel in the test fuels. While CO and CO2 emissions were reduced, NOx emissions were increased with increasing biodiesel contents in the mixture. It can be concluded that, tea seed oil, as an agricultural crop, might be a reasonable raw material for the biodiesel production. It was also shown that, up to 20% volumetric content of tea seed biodiesel could be effectively used in fuel mixture serving the purpose of reduction in diesel fuel usage.

The current prevailing energetical utilization of grass silage is based on anaerobic fermentation. However, huge fermentors and long retention times are needed because only a part of the organic matter undergoes the anaerobic fermentation. System of complex energetical utilization of the grass silage based on partition of easily accessible organic matter was verified on a commercial scale. It was confirmed that the separation of the accessible organic matter from the ballast enables minimization of the anaerobic fermentor dimensions from thousands to tens of cubic meters and reduced retention times from months into hours. In addition, the waste energy obtained from the cogeneration of the methane was used to run the overall technology and the charcoal kiln to produce charcoal from the ballast.

Based on constructal theory, entropy generation minimization, and second law efficiency, equations are formulated for tree-shaped counterflow-imbalanced heat exchanger for fully developed laminar and turbulent fluid flow. Entropy generation number, rational efficiency, and effectiveness behavior with respect to changes in number of pairing levels and different tube length-to-diameter ratios of constructal heat exchanger are analyzed analytically. Different values of capacity ratio and Reynolds number for fully developed laminar and turbulent fluid flow are considered to study the influence of pressure drop and flow imbalance irreversibilities of constructal heat exchanger. Values of tube length-to-diameter ratio and number of pairing levels of constructal heat exchanger can be obtained for lower entropy generation number and higher second law efficiency which includes both irreversibilities due heat transfer and pressure drop. The analysis reveals the improvements in the performance of constructal heat exchanger compared to conventional single-tube-dimensioned heat exchanger.

Over two-thirds energy of fuel consumed by a diesel engine is discharged to the surroundings. The application of thermal barrier coatings reduces the heat losses through the engine cooling systems and increases the efficiency and exhaust energy. This energy available in the exit stream of the low heat rejection (LHR) engine goes waste, if not recovered. In the present work, the combustion chamber of a single cylinder diesel was coated with aluminum titanate. A waste heat recovery system was developed using a thermoelectric power generation module. Experiments were carried out on the conventional diesel engine and insulated (400-μm coating thickness on the cylinder head, valves and 300, 400, and 500-μm thicknesses on the piston top surface) diesel engine. The highest brake thermal efficiency of 26% was obtained with the 400-μm thickness of alumina-titania insulation in the combustion chamber, as compared with that of the standard engine. A maximum module efficiency of 2.87% was obtained with the 400-μm thickness insulation. A maximum of 20.6% of waste heat available in the exhaust was recovered at full-load condition with the insulation of 400-μm thickness.

Current commercial photovoltaic (PV) conversion efficiency (flat plate modules) is about 6--20%, depending on the materials used for the module construction. Since only a small fraction (water module) the solar cells and improve their electricity production efficiency. This article describes the design and numerical simulation of a PVT system for producing electricity and hot water in a student hostel in Singapore. The nominal electrical power output is 10 kWp (kilowatt peak). Thermal models were developed based on basic energy balance equations and average climatic conditions for Singapore over a typical year were used. A survey of the hot water usage pattern over a typical week was carried out and used in the simulation. The optimum mass flow rate in the collectors is found to be 0.039 kg/(s m2) and the optimum storage tank capacity for hot water is 2500 kg for a showering load of around 6000 kg/day. The average thermal and electrical efficiency of the system are 43% and 12%, respectively. The requirement of auxiliary electric energy for water heating is predicted to be reduced by 94%.

The Romanian PV Systems Strategy stated as a target 260 MW installed power by 2020. Here, we discuss the potential of two hypothetical investors (the effective and the distributed) and three more realistic potential investors, i.e. the local administration, the small/medium enterprises (SMEs,) and the large national companies, respectively. From the point of view of evaluating the amount of electrical energy generated, the best strategy is that of the effective investor. However, the best realistic strategy is that of stimulating investments by large companies. The other three strategies give rather comparable (worse) results. The initial investments are similar, in first approximation, for all the five strategies. Without governmental or European subsidies, the project is not economically profitable. In practice, various governmental and European subsidies exist that are different for local administration, SMEs, and national companies, respectively. This makes the strategy based on investments by local administration the most attractive, followed by the strategy based on investments by SMEs. A combination of the three strategies, with focus on local administration, can be recommended for practical implementation.

The paper reports the production of syngas from dry reforming of methane (DRM) over La1−xCexNi1−yFeyO3 (x, y = 0–0.4) perovskites. A series of La1−xCexNi1−yFeyO3 were designed by central composite design (CCD) and synthesized by a sol–gel auto combustion method. Artificial neural network (ANN) approach was used to determine the relationship between preparation and operational parameters on the performance of the catalysts in the DRM process. Nickel mole fraction, lanthanum mole fraction, calcination temperature, and reaction temperature were considered as input variables, and conversion of methane was considered as the output variable. An ANN model with nine neurons in the hidden layer was the suitable in predicting conversion of methane. The genetic algorithm (GA) was subsequently used to determine the optimal preparation condition for enhancing the conversion of methane. La0.6Ce0.4Ni0.99Fe0.01O3 catalyst, calcined at 756°C was obtained to be the most active catalyst owing to the optimal composition of nickel and lanthanum in the catalyst formulation.

Catalytic activity of palladium supported on strongly acidic aluminum fluoride or on much less acidic magnesium fluoride has been the subject of current research. Both catalysts were synthesized by non-aqueous sol-gel method with subsequent two-stage activation: post-fluorination and reduction. The catalytic behavior of prepared Pd/HS-AlF3 and Pd/HS-MgF2 in the hydrodechlorination reactions of chlorinated hydrocarbons was investigated. It was found that differences in support acidity and catalyst’s activation protocol strongly effect the catalytic performance.

The performance of proton electron membrane fuel cells (PEMFCs) is affected by many factors, including the relative humidity and pressure of the inlet gases, the temperature of the fuel cell stack, the transport of the reactants and byproducts, the dissipation of the reaction heat, and so on. Thus, to optimize the PEMFC performance over a range of operating conditions, the various components within the PEMFC system must be appropriately controlled. Accordingly, the present study proposes a sophisticated control system for a 1.0 kW PEMFC system comprising a fuel cell stack, an auxiliary power supply, a DC--DC (direct current--direct current) buck converter, and a DC--AC (direct current--alternating current) inverter. The control system is implemented using a programmable logic controller and is designed to optimize the system performance and safety in both the start-up phase and the long-term operation phase. Uniquely, the control system is interfaced with a user friendly human--machine interface, which not only permits the PEMFC system to be operated by individuals with no experience in the field, but also provides access to the controller via the Internet such that the system can be maintained and tuned by a qualified technician in a remote location. Overall, the PEMFC system and associated control scheme proposed in this study have considerable potential for commercialization as a reliable, low-cost solution for meeting the power supply requirements of small-scale residential and office users.

Centrifugal compressor is a typical air compressor, which is an important subcomponent of the air supply system in fuel cell system. Optimizing the designing structure of centrifugal compressor plays significant influence on the output performance of fuel cell systems. However, existing experimental and numerical methods suffer from much economic and time cost and are inadequate for designing optimized centrifugal compressor. Thus, we develop a novel artificial intelligence (AI) framework integrated the data-driven surrogate model and stochastic optimization algorithm to achieve multi-objective optimization of the centrifugal compressor impeller. With the database obtained from the constructed three-dimensional (3D) steady-state centrifugal compressor model, the data-driven surrogate model based on Support Vector Machine (SVM) is trained. Then, the surrogate model coupled with a non-dominated sorting Genetic Algorithm (NSGA-III) is used to obtain the optimal solution of structural parameters. Compared with the original compressor design based on the established 3D model, the optimized compressor is comprehensively verified. Within the working range of the centrifugal compressor, the pressure ratio and isentropic efficiency of the optimized compressor have been significantly improved. The proposed optimized method is effective for the performance improved in fuel cell centrifugal compressor.

This paper presents the performance of the solid-oxide fuel cell/gas turbine hybrid power generation system with heat recovery waste unit based on the energy and exergy analyses. The effect of air inlet temperature and air/fuel ratio on exergy destruction and net-work output is determined. For the numerical calculations, air inlet temperature and air fuel ratio are increased from 273 to 373K and from 40 to 60, respectively. The results of the numerical calculations bring out that total exergy destruction quantity increases with the increase of air inlet temperature and air/fuel ratio. Furthermore, the maximum system overall first and second law efficiencies are obtained in the cases of air inlet temperature and air/fuel ratio equal to 273 K and 60, respectively, and these values are 62.09% and 54.91%.

This paper presents a theoretical comparison between fuel cell (FC) power train and conventional petrol driven propulsion system. FC has potential to reduce the CO2-emissions from road. However, FC power trains require energy storing device, to meet the peak power during extreme drive situations and also able to recover the kinetic energy of the vehicle during break operation. The proposed system includes a polymer electrolyte membrane fuel cell (PEMFC) based drive train and a super capacitor connected in parallel. The system is designed and dimensioned for a conventional petrol driven propulsion system of the Mercedes B-Class160. The feasibility study also includes comparison between the existing conventional systems. It is shown that although FC power train is heavier compared to existing system, urban performance is better and produces no CO2 and other harmful emissions.

A single-screw expander has been designed and manufactured independently. Based on this prototype, testing system has been built and performance experiment has been made. In this article, compressed air was used as working fluid and performance test for the prototype was finished at conditions including different rotational speed and different inlet pressure. From the experimental data, it is shown that when inlet pressure less than 0.8MPa the output power increases with the increase of rotational speed because of not enough expansion; when inlet pressure more than 0.8MPa, the every biggest output power is appeared in the condition of rotational speed 2600 rpm. The test results also show that the total efficiency is influenced by rotational speed obviously, and the highest total efficiency of this machine is 69.64% in the condition of 3000 rpm and 15 bar.

Based on panel data of 31 provincial capital cities in the country from January 21 to November 20, 2020, this research empirically analyzes the impacts of daily newly confirmed cases and daily new deaths from COVID-19 on PM10, PM2.5, SO2, CO, and NO2 emissions form green energy consumption by using the method of System Generalized Moments (SYS-GMM). We conclude that the COVID-19 pandemic has an inhibitory effect on all types of emissions, in that a greater number of confirmed cases and deaths brings about more stringent anti-epidemic policies, fewer emissions, and better air quality in China. Moreover, we use the methods of sample segmentation, cross-sectional regression, and pollutant emissions of the top three cities in terms of GDP to test their robustness. Overall, our evidence advances the debate over air quality after COVID-19, and that evidence from China provides beneficial experiences that correlate to its provincial data.

The COVID-19 epidemic has caused a severe impact on global financial markets. Considering that solar energy is an important basis for future energy development, it is particularly imperative to study the destructive effect of COVID-19 on solar energy development. This research thus explores the long-run relationship between COVID-19 and solar enterprises’ stock prices in 24 countries from December 31, 2019 to June 4, 2020. We not only use the number of confirmed cases to measure the severity of the COVID-19 epidemic, but also introduce the government response stringency index to capture the severity of the epidemic. Overall, our evidence indicates a cointegration relation between COVID-19 confirmed cases and the stock prices of solar enterprises, as well as between government response stringency and their stock prices. We also confirm that the COVID-19 epidemic has depressed the stock prices of most solar energy sources according to the long-run parameter estimation, especially with the implementation of a government’s prevention policy toward COVID-19. It is worth noting in the NON-OECD subsample that the negative impacts of the government response stringency index and confirmed cases on solar stock prices are not significant. Therefore, investors can adopt a hedging strategy to reduce losses caused by any fluctuation of these prices, while policymakers should take several measures such as tax deduction to reduce the negative impact of COVID-19 pandemic on the sustainable development of the solar energy sector.

To investigate the influences of structural parameters on output performances and further quantify the degree of influences, a one-dimensional transient multiphase proton exchange membrane fuel cell (PEMFC) model and a global sensitivity analysis model were established. After rigorous model validation, structural parameters such as the thickness of proton exchange membrane (MEM), catalytic layer (CL), micro-porous layer (MPL), and gas diffusion layer (GDL) as well as the porosity of CL, MPL, and GDL were studied. The ionomer volume fraction of cathode and anode were also studied. Increasing the thickness of MEM and CL decreases the membrane water content and increases the ohmic voltage loss. The increase of thickness leads to longer reaction gas transfer path and increase of transfer resistance. The increase of porosity increases the concentration of the reaction gas . However, too high porosity will reduce the effective ion conductivity . The increase of ionomer volume fraction is beneficial to electrochemical reaction. Based on quantitative sensitivity analysis, the MEM thickness and the anode ionomer volume fraction are defined as highly sensitive parameters. The MPL thickness and the GDL porosity are defined as insensitive parameters. The sensitivity of MEM thickness, CL thickness, and anode ionomer volume fraction becomemore prominent in large current density regions.

This paper’s purpose is to predict China’s uranium resources demand from 2016 to 2030 based on experimental modeling. In addition, we discuss the future supply structure of China’s uranium resources by analyzing the domestic and foreign supply capacity of China’s uranium resources. According the forecast results, Chinese uranium resource demand will reach 21385 tU in 2030 under a medium scenario. Due to the poor endowment of uranium resources, China’s domestic uranium production will increase slowly. It can be calculated that the total demand of uranium resources in China during 2016–2030 will be 216581 tU, the cumulative production of domestic production will be 37900 tU, the overseas production will be 41950 tU, and the international market purchases will be 130574 tU. Hence, the cumulative degree of dependence on foreign resources is approximately 80%. China’s foreign dependence on uranium will be greater than for oil, and the situation will become extremely serious. Therefore, we put forward several suggestions to ensure the supply of China’s uranium resources: (1) strengthening mineral exploration and increasing domestic production, (2) actively operating the “going out” strategy, (3) enhancing the enterprise competition ability, and (4) establishing uranium resource reserves. By these means, China could efficiently guarantee the domestic uranium resource security and respond to the competition of India’s uranium resources demand increased.

This article is suggesting some empirical correlations to calculate the freeboard entrainment heights and the average heat transfer coefficients for a horizontal tube over the freeboard region of high temperature fluidized bed combustors. The correlations are tested against some published experimental measurements for silica sand 465 μm and limestone 1,400 μm diameters in fluidized beds for temperatures up to 750°C. The height of a fluidized bed over the static bed is defined as the entrainment height; first a correlation is used to calculate the entrainment heights in order to determine the extent of the freeboard region at different bed temperatures and gas velocities. The heat transfer occurs by radiation, gas convection, and particle contact mechanisms in a high temperature fluidized bed combustor. Contribution of these heat transfer mechanisms to the overall heat transfer is described in detail over the freeboard region of fluidized beds by using empirical correlations. These correlations can be used to calculate the heat transfer characteristics in the design of fluidized bed combustors. The relative contribution of radiation increases with increasing freeboard elevation and approaches a constant fraction of the total average heat transfer.

An organic Rankine cycle (ORC) is generally used for converting low-grade heat into electricity. In this study, an extensive literature survey was conducted to identify current research gaps on experimental ORC systems. Specifically, there is limited experimental data and limited details on thermal and expander efficiencies of ORC systems. In order to address these gaps, the objective of this study included developing a turbine ORC with a power output exceeding 50 kW and thermal efficiency exceeding 8% for a heat source temperature < 120°C. The experimental results indicated that the system achieved a net power output of 242.5 kW and a thermal efficiency of 8.3% (the highest value for a turbine ORC system for the heat source temperature below 120°C). Thus, the study addressed the gaps identified in the research area of ORCs.

In this paper, a wet chemical method is used to coat LiNi0.8Co0.1Mn0.1O2 (NCM811) cathode material by Li2O-2B2O3 (LBO) layer for Lithium-ion batteries (LIBs). For performance optimization, the effects of different contents (thicknesses) of LBO coating layers on NCM811 particle surface on the morphologies, structures, compositions, and electrochemical properties of the corresponding LIBs are studied using XRD, SEM, TEM, and electrochemical measurements. Coin LIBs are assembled with such coated NCM811 cathode materials for performance validation. Results show that LBO coating layer does not change the original lattice structure of the bulk material, it can only adhere to the surface of the bulk material. After coating, NCM811 shows a good crystallinity and the ordered layered structure. TEM images show that the thickness of LBO coating is increased with increasing LBO content, and that the appropriate LBO coating thickness and uniform coating state are conducive to the improvement of the electrochemical properties of NCM811 cathode materials. Particularly, NCM811 with LBO coating content of 1000 ppm shows the best performance compared to other coating contents. In this case, the coating thickness is relatively uniform, which is about 40～100 nm, giving a good first charge-discharge capacity of 214.1mAh/g, and a high Coulomb efficiency of 90.06%. After 50 cycles, the capacity retention rate of LIBs still keeps as high as 99.64%. Therefore, LBO coating can improve the performance of NCM811 and then the lithium-ion batteries.

In the present study, an ejector-assisted dual-evaporator organic flash refrigeration cycle (EADEOFRC) is integrated with a single flash geothermal steam cycle (SFGSC). The EADEOFRC also consists of a two-phase expander extracting power from the high pressure fluid before the flashing. Isopentane and n-pentane are used as the working fluid of the EADEOFRC. It is observed that EADEOFRC can be operated at an organic fluid flash pressure corresponding to which refrigeration effects of both evaporators are equal. Corresponding to this operating condition of EADEOFRC, the integrated cycle yields higher second law efficiency compared to that of the SFSC. However, this yielded second law efficiency is lower than that of the dual flash steam cycle (DFSC). In the absence of the flash chamber, the ejectors and the evaporators, the EADEOFRC becomes merely a trilateral cycle (TLC), yielding only power output. Integration of SFSC and TLC yield substantially higher second law efficiency compared to that of the DFSC. Performance of the combined cycle slightly improves if n-pentane is used as the working fluid instead of isopentane.

Bio-oil from pyrolysis of biomass is an important renewable source for liquid fuel and/or for chemicals. However, the application of bio-oil was severely restricted due to its high viscosity, acidity, and low heating value. Hence, it is necessary to upgrade the bio-oil for deoxygenation or for chemicals by catalytic reactions. In this paper, the catalytic behaviors of SAPO-34, ZSM-5, and Y zeolite on pyrolysis of cellulose were investigated via pyrolyzer combined with gas chromatography and mass spectrometer (Py-GC/MS) method in Py-mode. The results showed that ZSM-5 and Y zeolite could promote the conversions of oxygen-containing components to gases, water, aromatics, and phenols. Comparatively, more gas and water were generated under the catalysis of Y zeolite at lower temperatures, while at temperatures above 700°C, the effect of ZSM-5 became more distinct; aromatics were more generated under the catalysis of ZSM-5, while Y zeolite exerted a more distinct role in promoting the formation of phenols. The effect of SAPO-34 caused more water and furfural derivatives, less aromatics and phenols, and exerted a weak influence on gases.

In this paper, taking 37000DWT asphalt ship as the research object, three different comprehensive cold energy utilization schemes are proposed. Through simulation analysis and evaluation of three different schemes, genetic algorithm is used for optimization and comparative analysis. The results show that from the perspective of energy utilization, supply–demand matching and economic benefits, the scheme of using all the cold energy of LNG for power generation is the best among the three schemes. Its exergy efficiency reaches 56.32%, and the net annual interest rate is CNY557,000, and the investment equipment cost is about CNY5.246917 million. It takes about 9.4 years to recover the cost.

The flow channel design significantly affects the operating performance of the vanadium redox flow battery (VRB). Serpentine flow channels enable uniform distribution of electrolyte concentration, which are widely used in flow channel design. However, this design leads to high electrolyte pressure drop and increased pump losses, thus reducing operating efficiency. To solve this problem, this paper proposes a novel composite serpentine channel design. The flow channel can significantly reduce the problem of excessively high electrolyte pressure drop inside the cell. In this paper, based on conservation laws of momentum, mass, charge and reaction kinetics, a three-dimensional model of a composite serpentine flow channel vanadium redox flow battery is developed to analyze the electrolyte behavior the COMSOL Multiphysics platform. The simulation results show that the pressure drop of the composite serpentine flow channel is largely reduced compared with that of the serpentine flow channel. The novel design can effectively reduce the pressure drop, and thus reduce the pump loss, which provides a guidance for VRB flow channel design.

Wind farm layout optimization that considers the wake effect is crucial to improve the power generation and wind energy efficiency of a wind farm. In this study, a state-of-the-art three-dimensional (3D) wake model is used to optimize the layout of wind turbines (WTs) in a wind farm. A surrogate model based on a back propagation neural network(BPNN) is developed to simplify the complex process of calculating the wake deficits. Furthermore, discrete particle swarm algorithm is used for optimizing the wind farm layout while considering different hub heights. The results show that the surrogate model significantly reduces the computation time. The optimization of the layout of WTs with different hub heights in a wind farm substantially reduces the wake effect.

Natural refrigerant ammonia R-717 and synthetic azeotropic refrigerant R-507 (a blend containing 50% R-143a and 5% R-125 by weight) are used in a wide range of refrigeration systems especially in low temperature applications. R-717 and R-507 are ozone friendly refrigerants, which have no Ozone Depletion Potential (ODP). Global Warming Potential (GWP) of R-717 and R-507 is equal to zero and 3300 respectively. The high amount of R-507 GWP demonstrates its negative effect on the earth’s climate change. In this study, a refrigerated warehouse located in Cincinnati, Ohio was modeled and the total energy demand and Coefficient of Performance (COP) was evaluated by eQUEST using two scenarios. The R-717 and R-507 were used as refrigerant in the first and second scenarios, respectively. The results showed that using R-717 in the refrigeration system leads to a 15% energy saving and a higher COP compared to R-507 in all working conditions. The only exception is that at an evaporating temperature below −35°C which COP values of both refrigerants are approximately equal.

Fermentative hydrogen production is considered as a promising source of renewable energy, and bacterial strain is an essential factor influencing hydrogen production. In this study, a high hydrogen-producing fermentative strain was isolated from a sugar plant, and identified as Clostridium sp. 5A-1 by 16S rRNA analysis. Strain 5A-1 was found to be a robust hydrogen-producing fermentative bacterium, which could produce hydrogen under a wide range of temperature (25°C–50°C) and initial pH (pH 5–9). The optimum culture temperature and initial pH for hydrogen production was 43°C and pH 7.5, respectively. The glucose concentration of 10 g/L resulted in the highest hydrogen production (1847 mL/L) and hydrogen production rate (231 mL/L.h), and 7 g/L glucose was the optimum substrate concentration for hydrogen yield (1.92 mol/mol glucose). Thus, Clostridium sp. 5A-1 is a potential candidate for fermentative hydrogen production.

To increase reliability and electrical performance, shallow-trench isolation (STI) (or called the field-oxide (FOX)) structures were inserted in the bulk-contact region of 60-V high-voltage p-channel lateral-diffused MOSFET (pLDMOS) devices in this study. As the FOX ratio increased with the addition of the FOX segments, the secondary breakdown current (It2) value was enhanced. Therefore, the anti-electrostatic discharge ability of a pLDMOS device can be efficiently improved using this novel method. In addition, when the weighting ratio of FOX structures increased, variation in the trigger voltage (Vt1) and holding voltage (Vh) values of the corresponding sample remained within the range of approximately 1–4 V. The Ron value decreased because of more uniform conduction. The experimental data for the FOX structures added to the bulk revealed that the It2 value was improved by approximately 13.98%, Vh values were greater than 60 V (which is favorable for latch-up immunity), and the Ron value was decreased by approximately 12.62% compared with a reference device under test (without FOX segments in the bulk-contact region).