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Frontiers in Energy

ISSN 2095-1701 (Print)
ISSN 2095-1698 (Online)
CN 11-6017/TK
Postal Subscription Code 80-972
Formerly Known as Frontiers of Energy and Power Engineering in China
2017 Impact Factor: 0.753

, Volume 13 Issue 1

For Selected: View Abstracts Toggle Thumbnails
Expulsive force in the development of CO2 sequestration: application of SC-CO2 jet in oil and gas extraction
Haizhu WANG, Gensheng LI, Zhonghou SHEN, Zhenguo HE, Qingling LIU, Bin ZHU, Youwen WANG, Meng WANG
Front. Energy. 2019, 13 (1): 1-8.
Abstract   HTML   PDF (1040KB)

With the rapid development of global economy, an increasing amount of attention has been paid to the emission of greenhouse gases, especially CO2. In recent years, dominated by the governments around the world, several significant projects of CO2 sequestration have been conducted. However, due to the huge investment and poor economic effects, the sustainability of those projects is not satisfactory. Supercritical CO2 (SC-CO2) has prominent advantages in well drilling, fracturing, displacement, storage, plug and scale removal within tubing and casing, which could bring considerable economic benefits along with CO2 sequestration. In this paper, based on physicochemical properties of SC-CO2 fluid, a detailed analysis of technical advantages of SC-CO2 applied in oil and gas development is illustrated. Furthermore, the implementation processes of SC-CO2 are also proposed. For the first time, a recycling process is presented in which oil and gas are extracted and the CO2 generated could be restored underground, thus an integrated technology system is formed. Considering the recent interests in the development of enhancing hydrocarbon recoveries and CO2 sequestration, this approach provides a promising technique that can achieve these two goals simultaneously.

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Cathodes with MnO2 catalysts for metal fuel battery
Songbo WEI, He LIU, Ran WEI, Lin CHEN
Front. Energy. 2019, 13 (1): 9-15.
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A series of cathodes with MnO2 catalysts of metal fuel battery were prepared. The catalyst slurry was treated by ultrasonic dispersion under the ultrasonic time of 20 min, 40 min and 60 min. The cathodes were also dried with the temperature of 90°C, 120°C and 150°C. Besides, the microstructures of the cathodes and discharging performance were investigated. The results indicated that the ultrasonic time and drying temperature had a remarkable influence on the electric current densities, but had little effect on the open-circuit voltage. The effects of oxygen on the current density and voltage of cathode were also studied, and it was found that the method of blowing oxygen to cathode could increase the current density of the metal fuel battery.

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Constant temperature control of tundish induction heating power supply for metallurgical manufacturing
Yufei YUE, Qianming XU, Peng GUO, An LUO
Front. Energy. 2019, 13 (1): 16-26.
Abstract   HTML   PDF (2698KB)

The tundish induction heating power supply (TIHPS) is one of the most important equipment in the continuous casting process for metallurgical manufacturing. Specially, the constant temperature control is greatly significant for metallurgical manufacturing. In terms of the relationship between TIH load temperature and output power of TIHPS, the constant temperature control can be realized by power control. In this paper, a TIHPS structure with three-phase PWM rectifiers and full-bridge cascaded inverter is proposed. Besides, an input harmonic current blocking strategy and a load voltage feedforward control are also proposed to realize constant temperature control. To meet the requirement of the system, controller parameters are designed properly. Experiments are conducted to validate the feasibility and effectiveness of the proposed TIHPS topology and the control methods.

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Metal-based direct hydrogen generation as unconventional high density energy
Shuo XU, Jing LIU
Front. Energy. 2019, 13 (1): 27-53.
Abstract   HTML   PDF (4964KB)

Metals are unconventional hydrogen production materials which are of high energy densities. This paper comprehensively reviewed and digested the latest researches of the metal-based direct hydrogen generation and the unconventional energy utilization ways thus enabled. According to the metal activities, the reaction conditions of metals were generalized into three categories. The first ones refer to those which would violently react with water at ambient temperature. The second ones start to react with water after certain pretreatments. The third ones can only react with steam under somewhat harsh conditions. To interpret the metal-water reaction mechanisms at the molecular scale, the molecule dynamics simulation and computational quantum chemistry were introduced as representative theoretical analytical tools. Besides, the state-of-the-art of the metal-water reaction was presented with several ordinary metals as illustration examples, including the material treatment technologies and the evaluations of hydrogen evolution performances. Moreover, the energy capacities of various metals were summarized, and the application potentials of the metal-based direct hydrogen production approach were explored. Furthermore, the challenges lying behind this unconventional hydrogen generation method and energy strategy were raised, which outlined promising directions worth of further endeavors. Overall, active metals like Na and K are appropriate for rapid hydrogen production occasions. Of these metals discussed, Al, Mg and their alloys offer the most promising hydrogen generation route for clean and efficient propulsion and real-time power source. In the long run, there exists plenty of space for developing future energy technology along this direction.

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Performance analysis of cogeneration systems based on micro gas turbine (MGT), organic Rankine cycle and ejector refrigeration cycle
Zemin BO, Kai ZHANG, Peijie SUN, Xiaojing LV, Yiwu WENG
Front. Energy. 2019, 13 (1): 54-63.
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In this paper, the operation performance of three novel kinds of cogeneration systems under design and off-design condition was investigated. The systems are MGT (micro gas turbine) + ORC (organic Rankine cycle) for electricity demand, MGT+ ERC (ejector refrigeration cycle) for electricity and cooling demand, and MGT+ ORC+ ERC for electricity and cooling demand. The effect of 5 different working fluids on cogeneration systems was studied. The results show that under the design condition, when using R600 in the bottoming cycle, the MGT+ ORC system has the lowest total output of 117.1 kW with a thermal efficiency of 0.334, and the MGT+ ERC system has the largest total output of 142.6 kW with a thermal efficiency of 0.408. For the MGT+ ORC+ ERC system, the total output is between the other two systems, which is 129.3 kW with a thermal efficiency of 0.370. For the effect of different working fluids, R123 is the most suitable working fluid for MGT+ ORC with the maximum electricity output power and R600 is the most suitable working fluid for MGT+ ERC with the maximum cooling capacity, while both R600 and R123 can make MGT+ ORC+ ERC achieve a good comprehensive performance of refrigeration and electricity. The thermal efficiency of three cogeneration systems can be effectively improved under off-design condition because the bottoming cycle can compensate for the power decrease of MGT. The results obtained in this paper can provide a reference for the design and operation of the cogeneration system for distributed energy systems (DES).

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Simulation analysis of municipal solid waste pyrolysis and gasification based on Aspen plus
Na DENG, Dongyan LI, Qiang ZHANG, Awen ZHANG, Rongchang CAI, Biting ZHANG
Front. Energy. 2019, 13 (1): 64-70.
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To predict and analyze the municipal solid waste (MSW) pyrolysis and gasification process in an up-draft fixed bed more veritably and appropriately, numerical modeling based on Gibbs energy minimization was executed using the Aspen plus software. The RYield module was combined with the RGibbs module to describe the pyrolysis section, while the RGibbs module was used for the gasification section individually. The proposed model was used to forecast and analyze the target performance parameters including syngas composition, lower heating value (LHV) and carbon conversion rate under different conditions of the gasification temperatures, and ratios and types of gasifying agents. The results indicate that there is a good agreement between the experimental data and the simulated data obtained using this model. The predicted optimum gasification temperature is approximately 750°C, and the best ratio of water vapor as gasifying agent is around 0.4. The mixture of flue gas and water vapor has an economical and recycled prospect among four commonly used gasifying agents.

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Application of AI techniques in monitoring and operation of power systems
David Wenzhong GAO, Qiang WANG, Fang ZHANG, Xiaojing YANG, Zhigang HUANG, Shiqian MA, Qiao LI, Xiaoyan GONG, Fei-Yue WANG
Front. Energy. 2019, 13 (1): 71-85.
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In recent years, the artificial intelligence (AI) technology is becoming more and more popular in many areas due to its amazing performance. However, the application of AI techniques in power systems is still in its infancy. Therefore, in this paper, the application potentials of AI technologies in power systems will be discussed by mainly focusing on the power system operation and monitoring. For the power system operation, the problems, the demands, and the possible applications of AI techniques in control, optimization, and decision making problems are discussed. Subsequently, the fault detection and stability analysis problems in power system monitoring are studied. At the end of the paper, a case study to use the neural network (NN) for power flow analysis is provided as a simple example to demonstrate the viability of AI techniques in solving power system problems.

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Reactive power deployment and cost benefit analysis in DNO operated distribution electricity markets with D-STATCOM
Atma Ram GUPTA, Ashwani KUMAR
Front. Energy. 2019, 13 (1): 86-98.
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The aim of this paper is to analyze unbalanced radial distribution systems (UBRDS) with the distribution static compensator (D-STATCOM). The main objectives of this paper are D-STATCOM allocation in UBRDS with an objective of providing reactive power support to enhance voltage profile and reduce line losses of the distribution network, determination of optimal D-STATCOM rating subjected to minimization of total cost, and impact of D-STATCOM placement on improving power factor and savings in cost of energy loss. The analysis is conducted on a large industrial load model with light, medium and high loading scenarios. Further, the impact of load growth is also considered for better planning of the power distribution system. The results are obtained on standard 25-bus UBRDS to check the feasibility of the proposed methodology.

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A novel flow-resistor network model for characterizing enhanced geothermal system heat reservoir
Jian GUO, Wenjiong CAO, Yiwei WANG, Fangming JIANG
Front. Energy. 2019, 13 (1): 99-106.
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The fracture characteristics of a heat reservoir are of critical importance to enhanced geothermal systems, which can be investigated by theoretical modeling. This paper presents the development of a novel flow-resistor network model to describe the hydraulic processes in heat reservoirs. The fractures in the reservoir are simplified by using flow resistors and the typically complicated fracture network of the heat reservoir is converted into a flow-resistor network with a reasonably simple pattern. For heat reservoirs with various fracture configurations, the corresponding flow-resistor networks are identical in terms of framework though the networks may have different section numbers and the flow resistors may have different values. In this paper, numerous cases of different section numbers and resistor values are calculated and the results indicate that the total number of flow resistances between the injection and production wells is primarily determined by the number of fractures in the reservoir. It is also observed that a linear dependence of the total flow resistance on the number of fractures and the relation is obtained by the best fit of the calculation results. Besides, it performs a case study dealing with the Soultz enhanced geothermal system (EGS). In addition, the fracture numbers underneath specific well systems are derived. The results provide insight on the tortuosity of the flow path between different wells.

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Design of packing cup interference fit value of hypercompressors for low density polyethylene production
Da LEI, Xuehong LI, Yun LI, Xiwen REN
Front. Energy. 2019, 13 (1): 107-113.
Abstract   HTML   PDF (737KB)

The hypercompressor is one of the core facilities in low density polyethylene production, with a discharge pressure of approximately 300 MPa. A packing cup is the basic unit of cylinder packing, assembled by the interference fit between an inner cup and an outer cup. Because the shrink-fitting prestresses the packing cup, serious design is needed to gain a favorable stress state, for example, a tri-axial compressive stress state. The traditional method of designing the interference fit value for packing cups depends on the shrink-fit theory for thick-walled cylinder subject to internal and external pressure. According to the traditional method, critical points are at the inner radii of the inner and external cup. In this study, the finite element method (FEM) has been implemented to determine a more accurate stress level of packing cups. Different critical points have been found at the edge of lapped sealing surfaces between two adjacent packing cups. The maximum Von Mises equivalent stress in a packing cup increases after a decline with the rise of the interference fit value. The maximum equivalent stress initially occurs at the bore of the inner cup, then at the edge of lapped mating surfaces, and finally at the bore of the outer cup, as the interference radius increases. The traditional method neglects the influence of axial preloading on the interference mating pressure. As a result, it predicts a lower equivalent stress at the bore of the external cup. A higher interference fit value accepted by the traditional method may not be feasible as it might already make packing cups yield at the edge of mating surfaces or the bore of the external cup. Along with fatigue analysis, the feasible range of interference fit value has been modified by utilizing FEM. The modified range tends to be narrower and safer than the one derived from the traditional method, after getting rid of shrink-fit values that could result in yielding in a real packing cup.

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Development of a supercritical and an ultra-supercritical circulating fluidized bed boiler
Junfu LYU, Hairui YANG, Wen LING, Li NIE, Guangxi YUE, Ruixin LI, Ying CHEN, Shilong WANG
Front. Energy. 2019, 13 (1): 114-119.
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The supercritical circulating fluidized bed (CFB) boiler, which combines the advantages of CFB combustion with low cost emission control and supercritical steam cycle with high efficiency of coal energy, is believed to be the future of CFB combustion technology. It is also of greatest importance for low rank coal utilization in China. Different from the supercritical pulverized coal boiler that has been developed more than 50 years, the supercritical CFB boiler is still a new one which requires further investigation. Without any precedentor engineering reference, Chinese researchers have conducted fundamental research, development, design of the supercritical CFB boilers independently. The design theory and key technology for supercritical CFB boiler were proposed. Key components and novel structures were invented. The first 600 MWe supercritical CFB boiler and its auxiliaries were successfully developed and demonstrated in Baima Power Plant, Shenhua Group as well as the simulator, control technology, installation technology, commissioning technology, system integration and operation technology. Compared with the 460 MWe supercritical CFB in Poland, developed in the same period and the only other supercritical one of commercial running in the word beside Baima, the 600 MWe one in Baima has a better performance. Besides, supercritical CFB boilers of 350 MWe have been developed and widely commercialized in China. In this paper, the updated progress of 660 MWe ultra-supercritical CFB boilers under development is introduced.

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Planning and analysis of the demonstration project of the MVDC distribution network in Zhuhai
Lu QU, Zhanqing YU, Qiang SONG, Zhichang YUAN, Biao ZHAO, Dawei YAO, Jianfu CHEN, Yao LIU, Rong ZENG
Front. Energy. 2019, 13 (1): 120-130.
Abstract   HTML   PDF (1938KB)

The DC distribution system is an important development direction of the distribution system, which can improve the reliability and the quality of the power supply, and support the new energy, the energy storage, the electric vehicles, and the flexible access of AC and DC loads to grid. To realize the demonstration application of the DC distribution technology, China’s first demonstration project of the medium voltage DC distribution network will be built in Zhuhai, Guangdong Province to support the construction of the city energy internet. First, this paper analyzes the demand of the DC distribution network project, and puts forward the construction content and construction target. Then, it designs and analyzes the electrical connection mode, system operation mode, and startup and shutdown mode of the DC distribution network, and proposes the overall project construction plan. Finally, it conducts the specific project design and analysis, which mainly include the selection of equipment such as inverters, DC transformers and DC circuit breakers, the design and analysis of the DC control and protection system, the design and analysis of the over-voltage protection and the configuration scheme of the lightning arrester, and analysis of the system transient characteristics. The design and analysis of the engineering program is a combination of China’s distribution network engineering practice and technical characteristics, which lays a solid foundation for the advancement of the DC power distribution technology in China, and has reference value and demonstration effect for the design and construction of other projects.

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Intelligent hybrid power generation system using new hybrid fuzzy-neural for photovoltaic system and RBFNSM for wind turbine in the grid connected mode
Front. Energy. 2019, 13 (1): 131-148.
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Photovoltaic (PV) generation is growing increasingly fast as a renewable energy source. Nevertheless, the drawback of the PV system is intermittent because of depending on weather conditions. Therefore, the wind power can be considered to assist for a stable and reliable output from the PV generation system for loads and improve the dynamic performance of the whole generation system in the grid connected mode. In this paper, a novel topology of an intelligent hybrid generation system with PV and wind turbine is presented. In order to capture the maximum power, a hybrid fuzzy-neural maximum power point tracking (MPPT) method is applied in the PV system. The average tracking efficiency of the hybrid fuzzy-neural is incremented by approximately two percentage points in comparison with the conventional methods. The pitch angle of the wind turbine is controlled by radial basis function network-sliding mode (RBFNSM). Different conditions are represented in simulation results that compare the real power values with those of the presented methods. The obtained results verify the effectiveness and superiority of the proposed method which has the advantages of robustness, fast response and good performance. Detailed mathematical model and a control approach of a three-phase grid-connected intelligent hybrid system have been proposed using Matlab/Simulink.

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Prediction of cost and emission from Indian coal-fired power plants with CO2 capture and storage using artificial intelligence techniques
Naushita SHARMA, Udayan SINGH, Siba Sankar MAHAPATRA
Front. Energy. 2019, 13 (1): 149-162.
Abstract   HTML   PDF (1939KB)

Coal-fired power plants are one of the most important targets with respect to reduction of CO2 emissions. The reasons for this are that coal-fired power plants offer localized large point sources (LPS) of CO2 and that the Indian power sector contributes to roughly half of all-India CO2 emissions. CO2 capture and storage (CCS) can be implemented in these power plants for long-term decarbonisation of the Indian economy. In this paper, two artificial intelligence (AI) techniques—adaptive network based fuzzy inference system (ANFIS) and multi gene genetic programming (MGGP) are used to model Indian coal-fired power plants with CO2 capture. The data set of 75 power plants take the plant size, the capture type, the load and the CO2 emission as the input and the COE and annual CO2 emissions as the output. It is found that MGGP is more suited to these applications with an R2 value of more than 99% between the predicted and actual values, as against the ~96% correlation for the ANFIS approach. MGGP also gives the traditionally expected results in sensitivity analysis, which ANFIS fails to give. Several other parameters in the base plant and CO2 capture unit may be included in similar studies to give a more accurate result. This is because MGGP gives a better perspective toward qualitative data, such as capture type, as compared to ANFIS.

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Flame-retardant properties of in situ sol-gel synthesized inorganic borosilicate/silicate polymer scaffold matrix comprising ionic liquid
Kumar Sai SMARAN, Rajashekar BADAM, Raman VEDARAJAN, Noriyoshi MATSUMI
Front. Energy. 2019, 13 (1): 163-171.
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This paper focuses on the superiority of organic-inorganic hybrid ion-gel electrolytes for lithium-ion batteries (LiBs) over commercial electrolytes, such as 1 M LiPF6 in 1:1 ethylene carbonate (EC): dimethyl carbonate (DMC) {1 M LiPF6-EC: DMC}, in terms of their flame susceptibility. These ion-gel electrolytes possess ionic liquid monomers, which are confined within the borosilicate or silicate matrices that are ideal for non-flammability. Naked flame tests confirm that the organic-inorganic hybrid electrolytes are less susceptible to flames, and these electrolytes do not suffer from a major loss in terms of weight. In addition, the hybrids are self-extinguishable. Therefore, these hybrids are only oxidized when subjected to a flame unlike other commercial electrolytes used in lithium-ion batteries. Supplementary analyses using differential scanning calorimetric studies reveal that the hybrids are glassy until the temperature reaches more than 100°C. The current results are consistent with previously published data on the organic-inorganic hybrids.

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Major applications of heat pipe and its advances coupled with sorption system: a review
Yang YU, Guoliang AN, Liwei WANG
Front. Energy. 2019, 13 (1): 172-184.
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Heat pipe utilizes continuous phase change process within a small temperature drop to achieve high thermal conductivity. For decades, heat pipes coupled with novel emerging technologies and methods (using nanofluids and self-rewetting fluids) have been highly appreciated, along with which a number of advances have taken place. In addition to some typical applications of thermal control and heat recovery, the heat pipe technology combined with the sorption technology could efficiently improve the heat and mass transfer performance of sorption systems for heating, cooling and cogeneration. However, almost all existing studies on this combination or integration have not concentrated on the principle of the sorption technology with acting as the heat pipe technology for continuous heat transfer. This paper presents an overview of the emerging working fluids, the major applications of heat pipe, and the advances in heat pipe type sorption system. Besides, the ongoing and perspectives of the solid sorption heat pipe are presented, expecting to serve as useful guides for further investigations and new research potentials.

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Performance analysis of solar absorption-subcooled compression hybrid refrigeration system in subtropical city
Xiangyang YE, Liming LIU, Zeyu LI
Front. Energy. 2019, 13 (1): 185-192.
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Solar absorption-subcooled compression hybrid refrigeration system is a new type of efficient and economical solar refrigeration device which always meets the demand of cooling load with the change of solar irradiance. The performance of the hybrid system is higher due to the improvement of evaporator temperature of absorption subsystem. But simultaneously, the variation of working process as well as performance is complicated since the absorption and compression subsystems are coupled strongly. Based on the measured meteorological data of Guangzhou, a subtropical city in south China, a corresponding parametric model has been developed for the hybrid refrigeration system, and a program written by Fortran has been used to analyze the performance of the hybrid system under different external conditions. As the condensation temperature ranges from 38°C to 50°C, the working time fraction of the absorption subsystem increases from 75% to 85%. Besides, the energy saving fraction also increases from 5.31% to 6.02%. The average COP of the absorption subsystem is improved from 0.366 to 0.407. However, when the temperature of the absorption increases from 36°C to 48°C, the average COP of hybrid system decreases from 2.703 to 2.312. Moreover, the working time fraction of the absorption subsystem decreases from 80% to 71.7%. The energy saving fraction falls from 5.67% to 5.08%. In addition, when the evaporate temperature increases from 4°C to 14°C, the average COP of the absorption subsystem decreases from 0.384 to 0.365. The work of the compressor decreases from 48.2 kW to 32.8 kW and the corresponding average COP of the absorption subsystem is improved from 2.591 to 3.082.

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Modeling analysis on solar steam generator employed in multi-effect distillation (MED) system
Zhaorui ZHAO, Bao YANG, Ziwen XING
Front. Energy. 2019, 13 (1): 193-203.
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Recently the porous bilayer wood solar collectors have drawn increasing attention because of their potential application in solar desalination. In this paper, a thermodynamic model has been developed to analyze the performance of the wood solar collector. A modeling analysis has also been conducted to assess the performance and operating conditions of the multiple effect desalination (MED) system integrated with the porous wood solar collector. Specifically, the effects of operating parameters, such as the motive steam temperature, seawater flow rate, input solar energy and number of effects on the energy consumption for each ton of distilled water produced have been investigated in the MED desalination system combined with the bilayer wood solar steam generator. It is found that, under a given operating condition, there exists an optimum steam generation temperature of around 145°C in the wood solar collector, so that the specific power consumption in the MED system reaches a minimum value of 24.88 kWh/t. The average temperature difference is significantly affected by the solar heating capacity. With the solar capacity increasing from 50 kW to 230 kW, the average temperature difference increases from 1.88°C to 6.27°C. This parametric simulation study will help the design of efficient bilayer wood solar steam generator as well as the MED desalination system.

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18 articles