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  • Lithium as energy carrier: CFD simulations of LI combustion in a 100 MW slag tap furnace
    Appl. Energy (IF 7.182) Pub Date : 2017-09-19
    Pascal Maas, Martin Schiemann, Viktor Scherer, Peter Fischer, Dan Taroata, Günther Schmid
    更新日期:2017-09-20
  • Thermal transfer performance of a spherical encapsulated PEG 6000-based composite for thermal energy storage
    Appl. Energy (IF 7.182) Pub Date : 2017-09-19
    E.M. Anghel, P.M. Pavel, M. Constantinescu, S. Petrescu, I. Atkinson, E. Buixaderas
    更新日期:2017-09-20
  • Using 3DVAR data assimilation to measure offshore wind energy potential at different turbine heights in the West Mediterranean
    Appl. Energy (IF 7.182) Pub Date : 2017-09-19
    Alain Ulazia, Jon Sáenz, Gabriel Ibarra-Berastegui, Santos J. González-Rojí, Sheila Carreno-Madinabeitia

    In this article, offshore wind energy potential is measured around the Iberian Mediterranean coast and the Balearic Islands using the WRF meteorological model without 3DVAR data assimilation (the N simulation) and with 3DVAR data assimilation (the D simulation). Both simulations have been checked against the observations of six buoys and a spatially distributed analysis of wind based on satellite data (second version of Cross-Calibrated Multi-Platform, CCMPv2), and compared with ERA-Interim (ERAI). Three statistical indicators have been used: Pearson’s correlation, root mean square error and the ratio of standard deviations. The simulation with data assimilation provides the best fit, and it is as good as ERAI, in many cases at a 95% confidence level. Although ERAI is the best model, in the spatially distributed evaluation versus CCMPv2 the D simulation has more consistent indicators than ERAI near the buoys. Additionally, our simulation’s spatial resolution is five times higher than ERAI. Finally, regarding the estimation of wind energy potential, we have represented the annual and seasonal capacity factor maps over the study area, and our results have identified two areas of high potential to the north of Menorca and at Cabo Begur, where the wind energy potential has been estimated for three turbines at different heights according to the simulation with data assimilation.

    更新日期:2017-09-20
  • Semi-physical models to assess the influence of CI engine calibration parameters on NOx and soot emissions
    Appl. Energy (IF 7.182) Pub Date : 2017-09-19
    Xavier Tauzia, Alain Maiboom, Hassan Karaky

    The progressive reduction of authorized emission levels in automotive Diesel engine standards has motivated the development of numerous technologies (exhaust gas recirculation (EGR), high pressure injection systems, sophisticated boosting systems, after-treatment devices, etc.) which, in turn, drastically increases the complexity of engine calibration. In this context the development of reliable simulation tools can help reduce the cost and time required for calibration. After a short introduction analysing the main currently existing models for evaluating engine emissions, this paper presents a novel 0D semi-physical model to assess engine-out NOx and soot emissions. The combustion process is modelled via Barba’s approach, while a thermodynamic two-zone calculation is used to evaluate adiabatic flame temperature. Emissions are modelled with semi-physical sub-models. This rather original approach does not evaluate emission on a crank-angle basis but only at exhaust valve opening (EVO), thus saving calculation time. The main physical parameters influencing pollutant formation are evaluated by the high-frequency 0D model and used as inputs for pollutant sub-models. NOx evaluation relies on a cartography linking NOx to O2 concentration and maximum values of in-cylinder bulk temperature and adiabatic flame temperature. Soot evaluation relies on a global equation, linking soot concentration to the main factors influencing formation and oxidation processes, in particular O2 concentration, in-cylinder pressure, temperatures and durations of some specific phases of the heat release rate (HRR), as well as turbulence intensity. The calibration of the models is thus quite easy and is described in the paper. The results of the models are then compared with measurements (different from those used for model calibration). NOx predictions are within ±20% of measured values for 95% of the tested operating points, with a R2 of 0.99, while for soot prediction a R2 coefficient of 0.93 is obtained and 96% of the tested points are within ±0.005 mg/cycle. Moreover, engine parameters sweeps (at constant engine speed and load) involving EGR rate, boost pressure, injection pressure and timing are performed for five operating points. The agreement with experiments is good on both qualitative and quantitative points of view, as long as a conventional combustion mode is achieved. Although simple and fast, these models are not only able to interpolate between the training points but also to extrapolate with a reasonable accuracy when the engine calibration parameters are changed. This latter property is rarely demonstrated in existing models.

    更新日期:2017-09-19
  • A two-level multi-objective optimization for simultaneous design and scheduling of a district energy system
    Appl. Energy (IF 7.182) Pub Date : 2017-09-18
    Mohammad Sameti, Fariborz Haghighat
    更新日期:2017-09-19
  • Optimal planning of microgrid power and operating reserve capacity
    Appl. Energy (IF 7.182) Pub Date : 2017-09-18
    Mike Quashie, Chris Marnay, François Bouffard, Géza Joós

    This paper proposes a bi–level formulation for a coupled microgrid power and reserve capacity planning problem, cast within the jurisdiction of a distribution system operator(DSO). The upper level problem of the proposed bi–level model represents a microgrid planner whose goal is to minimize its planning and operational cost, while the lower level problem represents a DSO whose primary duty is to ensure reliable power supply. The microgrid planner, pursues its interest by co–optimizing the design configuration and power output of individual distributed energy resources (DERs), while the DSO maximizes the capacity of flexible reserve resources. The proposed model is recast as a mathematical program with equilibrium constraints (MPEC) wherein the decision variables of the two problems are independently controlled. Application of the proposed approach to the energy infrastructure of a Canadian utility network is discussed. Results obtained through its application are compared to an alternative multi–objective planning model and the improved benefits are assigned to the corresponding stakeholders.

    更新日期:2017-09-19
  • Dynamics of China’s carbon prices in the pilot trading phase
    Appl. Energy (IF 7.182) Pub Date : 2017-09-18
    John Hua Fan, Neda Todorova

    This paper is the first to investigate empirically the link between carbon prices and macro risks in China’s cap-and-trade pilot scheme. Using data from four pilot markets in Beijing, Guangdong, Hubei, and Shenzhen from 2014 to 2016, we demonstrate that the carbon price in Hubei is weakly linked to international prices of natural gas. Our results also indicate that energy, utilities, industrial and materials sector indices are positively related to the allowance prices in Shenzhen and Guangdong, suggesting that higher emitters in the region may have factored the carbon price into their production mix. We find no statistically significant relationship in the Beijing pilot. Overall, the findings suggest that China’s carbon market is currently in an early stage of development, as the carbon price fundamentals are weak and the markets are comparatively less efficient than the European trading scheme in an informational sense. The findings of the paper have policy implications for the upcoming integration of regional markets into the national carbon market.

    更新日期:2017-09-19
  • A computationally efficient pseudo-3D model for the numerical analysis of borehole heat exchangers
    Appl. Energy (IF 7.182) Pub Date : 2017-09-18
    Giuseppe Brunetti, Hirotaka Saito, Takeshi Saito, Jiří Šimůnek

    Ground-Source Heat Pump (GSHP) systems represent one of the most efficient renewable energy technologies. Their efficiency is highly influenced by the thermal properties of the ground, which are often measured in-situ using the Thermal Response Tests (TRTs). While three-dimensional mechanistic models offer significant advantages over analytical solutions for the numerical interpretation of TRTs, their computational cost represents a limiting factor. Moreover, most of the existing models do not include a comprehensive description of hydrological processes, which have proven to strongly influence the behavior of GSHP. Thus, in this study, we propose a computationally efficient pseudo-3D model for the numerical analysis and interpretation of TRTs. The numerical approach combines a one-dimensional description of the heat transport in the buried tubes of the exchanger with a two-dimensional description of the heat transfer and water flow in the surrounding subsurface soil, thus reducing the dimensionality of the problem and the computational cost. The modeling framework includes the widely used hydrological model, HYDRUS, which can simulate the movement of water, heat, and multiple solutes in variably-saturated porous media. First, the proposed model is validated against experimental data collected at two different experimental sites in Japan, with satisfactory results. Then, it is combined with the Morris method to carry out a sensitivity analysis of thermal properties. Finally, the model is exploited to investigate the influence of groundwater and lithologic heterogeneities on the thermal behavior of the GSHP.

    更新日期:2017-09-19
  • A data-driven methodology to support pump performance analysis and energy efficiency optimization in Waste Water Treatment Plants
    Appl. Energy (IF 7.182) Pub Date : 2017-09-18
    Dario Torregrossa, Joachim Hansen, Francesc Hernández-Sancho, Alex Cornelissen, Georges Schutz, Ulrich Leopold

    Studies and publications from the past ten years demonstrate that generally the energy efficiency of Waste Water Treatment Plants (WWTPs) is unsatisfactory. In this domain, efficient pump energy management can generate economic and environmental benefits. Although the availability of on-line sensors can provide high-frequency information about pump systems, at best, energy assessment is carried out a few times a year using aggregated data. Consequently, pump inefficiencies are normally detected late and the comprehension of pump system dynamics is often not satisfactory. In this paper, a data-driven methodology to support the daily energy decision-making is presented. This innovative approach, based on fuzzy logic, supports plant managers with detailed information about pump performance, and provides case-based suggestions to reduce the pump system energy consumption and extend pump life spans. A case study, performed on a WWTP in Germany, shows that it is possible to identify energy inefficiencies and case-based solutions to reduce the pump energy consumption by 18.5%.

    更新日期:2017-09-19
  • Numerical modeling study of a man-made low-permeability barrier for the compressed air energy storage in high-permeability aquifers
    Appl. Energy (IF 7.182) Pub Date : 2017-09-18
    Yi Li, Lehua Pan, Keni Zhang, Litang Hu, Jinsheng Wang, Chaobin Guo

    Compressed air energy storage (CAES) is a grid-scale energy storage technology for intermittent energy, as proven by the decades-long successful operation of two existing compressed air energy storage in cavern (CAESC) power plants. Because of the limited availability of salt domes appropriate for CAESC, the more widely available aquifers (compressed air energy storage in aquifers, CAESA) have recently attracted considerable attention as candidates for CAES. An ideal aquifer for CAESA is highly permeable around the well to facilitate easy injection and withdrawal of air, but the high-permeability region is surrounded by low-permeability zones to minimize the loss of injected air and decrease in energy efficiency. However, such ideal geological structures are not always available in nature. Therefore, the potential of creating man-made low-permeability barrier in high-permeability aquifers is very interesting. In this paper, we investigate the feasibility of man-made low-permeability barriers in high-permeability aquifers using the numerical simulator TOUGH2/Gel to calculate the three-component flow (including a miscible gelling liquid). The simulation results show that an expected low-permeability barrier can be created by injecting grout with certain properties, and the altered aquifer performs well for CAESA. Additional sensitivity studies are also performed to reveal the effects of the various factors on the success of the low-permeability barrier creation, including the critical solidification concentration, the scale factor of the time dependence of the grout viscosity, the relative density of the grout, and the volume of the follow-up water injection. The results indicate that, in a horizontal aquifer, low critical solidification concentrations, and small scale factors are generally preferred and the density of grout should be close to that of the in situ water. For the given volume of the injected grout, there is an optimal follow-up water injection that will create the largest storage space without damaging the barrier. These results may help to extend the candidate sites for CAESA and the prospect of large scale energy storage.

    更新日期:2017-09-19
  • Quantification of heat losses through building envelope thermal bridges influenced by wind velocity using the outdoor infrared thermography technique
    Appl. Energy (IF 7.182) Pub Date : 2017-09-18
    Małgorzata O'Grady, Agnieszka A. Lechowska, Annette M. Harte

    Improving the thermal performance of the existing building stock is essential to significantly reduce the overall energy consumption in the building sector. A key objective is the retrofitting of the existing building envelope. A necessary first step in the building envelope optimization process is the assessment of its actual thermal performance. This assessment should be repeated after retrofitting to clearly define the improvements that were made and the heat loss reduction that was achieved. In this study, an efficient, non-destructive, in-situ measurement method, based on an outdoor infrared thermographic survey, is developed to determine the thermal bridging performance. As wind velocity significantly influences the heat losses through the building envelope, this study includes quantification of the wind velocity impact on the Ψ-value. This was assessed by undertaking ITT of the same thermal bridge at various wind velocities, in a controlled environment, in a hot box device. The results showed that the Ψ-value is highly dependent on wind velocity so that measurement of the Ψ-value taken at different wind conditions cannot be directly compared. An adjustment procedure is proposed that can be used to convert the Ψ-value measured at any wind velocity to a standard value corresponding to a velocity of 4 m/s. From a practical point of view, this adjustment procedure makes the methodology widely applicable.

    更新日期:2017-09-19
  • Challenges and uncertainties of ex ante techno-economic analysis of low TRL CO2 capture technology: Lessons from a case study of an NGCC with exhaust gas recycle and electric swing adsorption
    Appl. Energy (IF 7.182) Pub Date : 2017-09-18
    Mijndert van der Spek, Andrea Ramirez, André Faaij

    this work addresses the methodological challenges of undertaking techno-economic assessments of very early stage (technology readiness level 3–4) CO2 capture technologies. It draws lessons from a case study on CO2 capture from a natural gas combined cycle with exhaust gas recycle and electric swing adsorption technology. The paper shows that also for very early stage technologies it is possible to conduct techno-economic studies that give a sound first indication of feasibility, providing certain conditions are met. These conditions include the availability of initial estimates for the energy use of the capture technology, either from bench scale measurements, or from rigorous process models, and the possibility to draw up a generic (high level) equipment list. The paper shows that for meaningful comparison with incumbent technologies, the performance of very early stage technologies needs to be projected to a future, commercial state. To this end, the state of the art methods have to be adapted to control for the development and improvements that these technologies will undergo during the R&D cycle. We call this a hybrid approach. The paper also shows that CO2 capture technologies always need to be assessed in sympathy with the CO2 source (e.g. power plant) and compression plant, because otherwise unreliable conclusions could be drawn on their feasibility. For the case study, it is concluded that electric swing adsorption is unlikely to become economically competitive with current technologies, even in a highly optimised future state, where 50% of the regeneration duty is provided by LP steam and 50% by electricity: the net efficiency of an NGCC with EGR and optimised ESA (49.3%LHV; min–max 45.8–50.4%LHV) is lower than that of an NGCC with EGR and standard MEA (50.4%LHV). Also, investment and operational costs are higher than MEA, which together with ESA’s lower efficiency leads to an unfavourable levelised cost of electricity: 103 €/MWh (min–max 93.89–117.31 €/MWh) for NGCC with ESA, versus 91 €/MWh for NGCC with MEA.

    更新日期:2017-09-19
  • Uncertainties in corn stover feedstock supply logistics cost and life-cycle greenhouse gas emissions for butanol production
    Appl. Energy (IF 7.182) Pub Date : 2017-09-18
    Nawa Raj Baral, Carlos Quiroz-Arita, Thomas H. Bradley

    The success and sustainable operation of a commercial cellulosic biorefinery are highly dependent on price, quality, and availability of feedstocks. Currently, corn stover is a primary feedstock choice for cellulosic ethanol production and the same feedstock can be used for butanol production, which is a potential alternative biofuel. However, butanol production requires different levels of feedstock and logistical resources when compared to ethanol due to about 20% lower theoretical yield. A thorough analysis of cost, life-cycle energy use and life-cycle greenhouse gas emissions associated with a feedstock supply logistics system for butanol production is yet to be done. Additionally, quality standards for corn stover feedstock are yet to be determined, which could determine cost of the feedstock for commercial applications. Thus, this study aimed to fulfill these research gaps using techno-economic analysis and life-cycle assessment methodologies. Variability in logistical resources and other input parameters gathered from recent literature were used for analyses in this study. Average corn stover supply logistics cost ($/metric ton(t), dry), life-cycle energy use (MJ/t, dry) and life-cycle greenhouse gas emissions (kg CO2e/t, dry) were 86.9, 1073.7 and 83.8, which could increase at 95% certainty to 159–504, 1672–3817 and 138–271, respectively, depending on the types of probability distributions of the input parameters. However, the mode value of logistics cost ($/t, dry), life-cycle energy use (MJ/t, dry) and life-cycle greenhouse gas emissions (kg CO2e/t, dry) of 80–120, 913–1231 and 79–120, respectively, closely represents the results of the static model. The average estimated feedstock cost for butanol production was about 1.3 times and the minimum 95% certainty value is about 2 times more than the targeted feedstock cost ($/metric ton, dry) of 66.4, excluding preprocessing. Overall, the location of the biorefinery, quality of corn stover, sustainable agricultural practices, and optimum utilization of transportation resources were key factors that enable a sustainable feedstock supply logistics system.

    更新日期:2017-09-19
  • Effect of land use change for bioenergy production on feedstock cost and water quality
    Appl. Energy (IF 7.182) Pub Date : 2017-09-18
    Jia Zhong, T. Edward Yu, Christopher D. Clark, Burton C. English, James A. Larson, Chu-Lin Cheng
    更新日期:2017-09-19
  • The effects of flow-field orientation on water management in PEM fuel cells with serpentine channels
    Appl. Energy (IF 7.182) Pub Date : 2017-09-18
    Moosa Ashrafi, Mehrzad Shams

    A numerical scheme for the effect of flow-field orientation on water management in PEM fuel cell is developed. Since there are limitations on the location of proton exchange membrane fuel cell such as portable applications, different configurations are used for proper water management. Therefore, the best configuration must be chosen for the most efficient and stable operation of the fuel cells. In this research, a 3D numerical model is proposed based on the VOF method in order to simulate the effects of gravity on the gas–liquid two-phase flow in a full-scale single-serpentine flow-field. This model, which is validated by the experimental results, considers the microstructure of the gas diffusion layer by two square pores in every cross section along the channels. The simulations are done for the vertical and horizontal fuel cells. The effects of water coverage ratios and flow regimes on pressure drop and the resulting parasitic power loss are investigated for different configurations. In the vertical orientation, the channels are placed horizontally or vertically in each configuration. The results reveal that in the vertical cells, when the channels are located horizontally and the inlet manifold is embedded on the upper side of the flow-field, the pressure drop is the lowest. The reason is that the film flow is formed in the channels and the gravity assists in the water removal. However, when both the cell and channels are vertical and the cathode inlet manifold is placed on the bottom of the flow-field, the pressure drop and the resulting parasitic power is the highest. This is due to the gravity is against the water purging from the elbows leading to formation of long plugs along the channels. The present numerical model can be used for simulation of two-phase flow in channels of the serpentine flow-field at any cell orientation angle by changing the gravity direction in the model.

    更新日期:2017-09-19
  • Effects of oxygen carrier mole fraction, velocity distribution on conversion performance using an experimentally validated mathematical model of a CLC fuel reactor
    Appl. Energy (IF 7.182) Pub Date : 2017-09-18
    R. Ben-Mansour, H. Li, M.A. Habib

    Due to the severity of the worldwide climate change problem and the ocean acidification problem, chemical looping combustion (CLC) technology is studied worldwide by researchers in order to meet the urgency of carbon emission reduction after its concept has been put forward. An experimentally validated computer model has been implemented in Ansys-Fluent code with the most appropriate kinetic model implemented in User Define Functions. The validated model has been used to carry out a numerical study on a model fuel reactor using CaSO4 as oxygen carrier and H2 as fuel; is conducted in the present work. Effects of mole fraction of CaS, operating temperature, superficial feeding velocity magnitude of fuel and the diameter of oxygen carrier particles were discussed. The results indicate that the superficial feeding velocity of gaseous fuel has significant effects on the flow condition with fuel reactor and conversion performance, while operating temperature mainly affects the fuel conversion. The effects of particle diameter on flow condition within FR are obvious but insignificant on conversion performance of fuel. The mole fraction of CaS has the least effect among these three parameters. Several velocity distributions are also studied. The rectangle-trianble distributor results in better bubbles distributions, but the gain of higher fuel conversion rate is insignificant due to the low chemical activity of OC used in this study.

    更新日期:2017-09-19
  • Influence of the vertical wind and wind direction on the power output of a small vertical-axis wind turbine installed on the rooftop of a building
    Appl. Energy (IF 7.182) Pub Date : 2017-09-18
    Kung-Yen Lee, Shao-Hua Tsao, Chieh-Wen Tzeng, Huei-Jeng Lin

    The goal of this study is to investigate the performance of a small vertical-axis wind turbine at an environment with the turbulence intensity more than 30%, particularly on the influence of the vertical wind, the vertical angle, the wind with the unknown direction, the horizontal wind speed, and the turbulence intensity on the power output, which are seldom reported before. The results show that more than 90% of the power is generated when the vertical angle is less than or equal to 45°. The vertical wind speed has the obvious influence on the power when the horizontal wind speed is between 5 m/s and 8 m/s. The percentage of the power generated by the wind with the unknown direction decreases from 31.1% to 8.4% as the horizontal wind speed increases from 4 m/s to 9 m/s. The efficiency is over 40% only when the horizontal wind speed is over 8 m/s. The higher turbulence intensity increases the power at the lower wind speed, but decreases the power at the higher wind speed. Furthermore, the results can be used as a reference for the improvement of aerodynamic characteristics, efficiency, CFD simulation and the location selection of a vertical-axis wind turbine.

    更新日期:2017-09-19
  • Dynamic modeling and control analysis of a methanol autothermal reforming and PEM fuel cell power system
    Appl. Energy (IF 7.182) Pub Date : 2017-09-18
    Dimitris Ipsakis, Martha Ouzounidou, Simira Papadopoulou, Panos Seferlis, Spyros Voutetakis

    In the present study, a rigorous dynamic and control-oriented model is developed towards accurately describing the autonomous operation of a methanol reforming-fuel cell power system (up to 5 kWel). The system consists of an autothermal steam reformer that provides hydrogen to a polymer electrolyte membrane (PEM) fuel cell. A purification stage (preferential oxidation reactor) intercedes between the steam reformer and the fuel cell and maintains CO levels below 10–50 ppm, while a heat-exchanging network (comprising of two coolers and a burner) is employed towards managing a well-balanced autothermal operation. The proposed dynamic model is developed on the basis of describing accurately the evolving chemical and electrochemical interactions between the subsystems and utilizes a group of partial/ordinary differential equation (reactors and heat exchangers) along with a set of non-linear equations (reaction kinetics and current-voltage dependence). Based on the system main operating features, a control structure through the implementation of PI controllers is proposed for the control of (a) the reformer feed and exit temperature through methanol burning and steam reformer feed flowrate manipulation respectively, (b) CO concentration through O2/CO feed ratio manipulation, (c) power production (specified by the fuel cell operation current) through methanol reformer feed and (d) subsystem exit temperatures through coolant flowrate manipulation. An overall simulation case study reveals the proper selection of system manipulated and controlled variables towards achieving the applied operating set-points, where it is shown that the system sustains a flexible operation, along with fast start-up and dynamic transients.

    更新日期:2017-09-19
  • Electrical power generation under policy constrained water-energy nexus
    Appl. Energy (IF 7.182) Pub Date : 2017-09-18
    Blaže Gjorgiev, Giovanni Sansavini

    Water-energy nexus refers to the interdependence between water resources and energy conversion, and it encompasses the multiple phases of electric power generation and water processing and distribution. Current policies for the utilization of freshwater resources in electric power generation regulate the thermal discharges and their effect on the aquatic life. Water withdrawals and consumption polices are mainly prescribed at the regional level instead. This paper focuses on the effects of water policy constraints on electric power generation in changing climate conditions. A river basin is simulated, which hosts two hydraulically linked power generating stations, namely an upstream hydropower plant with reservoir and a downstream thermal power plant. Two alternative cooling designs are tested for the thermal power plant, i.e. once-through and wet tower cooling. Severe drought conditions leading to small river flows and high water temperatures are analyzed, and the limitations to the energy conversion at the thermal plant stemming from the water policies are quantified. The results show that some small flexibility in the water policy constraints during extreme droughts can secure a significant amount of energy to the power system, which would have been curtailed otherwise. Remarkably, the relaxation of 1.5 °C in the water policy constraints prevents the curtailment of 42% of the generation capacity of a 1000 MWe thermal plant during the analyzed 24 h drought scenario. In general, the type and the required amount of constraint relaxation depend on the environmental conditions and are to be judged case-by-case. Furthermore, the smart scheduling of water resources grants a 7% increase of the energy converted during droughts in the hydraulically linked hydro and thermal power plants. Finally, the analysis shows that once-through cooling systems are extremely sensitive to changes in water flow and temperature opening space for less sensitive technologies, i.e. wet cooling towers.

    更新日期:2017-09-19
  • Simultaneous production of CH4-rich syngas and high-quality tar from lignite by the coupling of noncatalytic/catalytic pyrolysis and gasification in a pressurized integrated fluidized bed
    Appl. Energy (IF 7.182) Pub Date : 2017-09-18
    Zhaohui Chen, Shiqiu Gao, Guangwen Xu

    An integrated fluidized bed (IFB) reactor with a two-stage configuration has been developed to process small-size coal particles for the simultaneous production of CH4-rich syngas and high-quality tar, in which coal pyrolysis occurred in an upper transport bed (TB) within an atmosphere mixing steam and syngas generated by steam-oxygen gasification of coal or char in a lower fluidized bed (FB). The coupling effect was investigated by combining non-catalytic/catalytic pyrolysis and gasification in a pressurized IFB. Having TB pyrolysis obviously raised CH4 yield (also its content in producer gas) and tar yield. The respective contributions to CH4 formation from the TB pyrolysis and FB gasification were mainly relevant to operating pressure and Ca(OH)2 catalyst. Raising pressure facilitated CH4 formation. When lignite was treated without catalyst, the contribution from TB pyrolysis was greater than that from FB gasification as hydropyrolysis was intensified by pressure in H2-rich gas atmosphere from the FB gasifier. Adding catalyst into lignite reversed their contributions. The FB catalytic gasification formed more CH4 because Ca(OH)2 functioned well as a catalyst for CH4 formation in pressurized gasification. With elevated pressure or/and the addition of Ca(OH)2, pyrolysis tar yield decreased in different degrees but its quality was improved. With the combination effect of pressure and Ca(OH)2, producer gas from the tested IFB reactor was highly rich in CH4 to reach 10.8 vol%, with as well a high H2/CO ratio of 2.3 that is suitable for making SNG. The obtained tar had its light tar content as high as 95 wt%.

    更新日期:2017-09-19
  • Thermionic energy conversion for concentrating solar power
    Appl. Energy (IF 7.182) Pub Date : 2017-09-15
    Gang Xiao, Guanghua Zheng, Min Qiu, Qiang Li, Dongsheng Li, Mingjiang Ni

    Concentrating solar power (CSP) is a mainstream of solar energy utilization, and thermionic emission is a potential way to convert concentrated solar radiation into power with a theoretical efficiency of 50–70%, surpassing both Shockley-Queisser limit and photo-thermal limit. This literature attempts to provide a comprehensive understanding of and an insight into solar thermionic energy conversion. The fundamentals of electron emission from electrodes and electron transport in vacuum gap are presented, as well as the state of the art of solar thermionic energy conversion technologies, including heat-induced thermionics and photon-enhanced thermionics. The former is driven by thermal energy, whereas the latter takes advantage of both quantum photon energy and thermal energy. Burgeoning research indicates that photon-enhanced thermionic conversion is a promising technology for concentrating solar power due to the high efficiency and simple operating mode. Now, it is important to develop novel materials and coating technologies to facilitate electron emission and reduce space charge effect in interelectrode vacuum. Structural design of thermionic converters and top–bottom configuration of solar-electricity systems are suggested for practical applications.

    更新日期:2017-09-15
  • Leading-edge serrations for performance improvement on a vertical-axis wind turbine at low tip-speed-ratios
    Appl. Energy (IF 7.182) Pub Date : 2017-09-15
    Zhenyu Wang, Mei Zhuang
    更新日期:2017-09-15
  • Synergistic engine-fuel technologies for light-duty vehicles: Fuel economy and Greenhouse Gas Emissions
    Appl. Energy (IF 7.182) Pub Date : 2017-09-15
    Kai Morganti, Marwan Al-Abdullah, Abdullah Alzubail, Gautam Kalghatgi, Yoann Viollet, Robert Head, Ahmad Khan, Amir Abdul-Manan

    Advanced engine technologies will play a central role in achieving future greenhouse gas (GHG) emissions targets for light-duty vehicles. However, these technologies will place greater emphasis on optimizing the engine and fuel as a synergistic system, since many technologies will require higher octane gasolines to realize their full social and environmental benefits. The most extreme example of a synergistic engine-fuel system is the Octane-on-Demand concept. This technology platform makes use of an oil-derived fuel at low and intermediate loads where the octane requirement of the engine is comparatively low, while a second high octane fuel is introduced at higher loads to suppress knock. This paper presents the first comprehensive study of vehicle fuel economy and well-to-wheel GHG emissions for the Octane-on-Demand concept with respect to a regular grade E10 gasoline (RON 93) and a high octane E30 gasoline (RON 101). Experimental fuel consumption maps are first used to evaluate the drive cycle fuel economy and GHG emissions for a light-duty vehicle equipped with two alternative powertrains. The upstream GHG emissions arising from the production of the fuels are then quantified, with consequent uncertainties assessed using Monte Carlo analysis based on probability distribution functions for critical input parameters. The results demonstrate that the Octane-on-Demand concept used in conjunction with either methanol or ethanol generally provides comparable well-to-wheel GHG emissions to the high octane E30 gasoline, with up to a 10% improvement in the vehicle fuel economy. The use of a non-traditional engine calibration strategy that maximizes the trade-off between thermal efficiency and fuel energy density also enables the amount of high octane fuel required to suppress knock to be reduced significantly. This increases the distance that the vehicle can be driven before the secondary tank requires refueling by a considerable margin, but comes at the expense of marginally higher well-to-wheel GHG emissions than could otherwise be achieved. These findings are shown to be largely insensitive to uncertainties in the upstream fuel production GHG emissions, with the exception of the land use change (LUC) for bioethanol. Overall, this study has implications for the design of engine-fuel systems for future light-duty vehicles.

    更新日期:2017-09-15
  • Free piston expander-linear generator used for organic Rankine cycle waste heat recovery system
    Appl. Energy (IF 7.182) Pub Date : 2017-09-15
    Xiaochen Hou, Hongguang Zhang, Fei Yu, Hongda Liu, Fubin Yang, Yonghong Xu, Yaming Tian, Gaosheng Li

    This study presents an experimental investigation of a free piston expander-linear generator (FPE-LG) used for organic Rankine cycle (ORC) waste heat recovery system. A FPE-LG test rig using compressed air as working fluid is established. The motion characteristics, dynamic characteristics and the indicated efficiency of FPE-LG are analyzed. The motion characteristics and power output performance for different valve timings are studied. The degree of symmetry is defined to evaluate the asymmetry motion characteristics of the free piston assembly. The coefficient of cycle-to-cycle variation (COV) is presented to evaluate the cycle-to-cycle variation characteristics of the FPE-LG. Experimental results show that the free piston assembly displacement profile is similar to a sinusoidal wave and the free piston assembly can operate at high and relatively constant speed at the middle portion of the stroke. The maximum power output of 19 W can be achieved when the intake pressure is 2.0 bar and the operation frequency is 2.5 Hz. The valve timing and intake pressure demonstrate a significant influence on the asymmetric motion and the power output performance of the FPE-LG. The indicated efficiency of the FPE (left cylinder) decreases with the increase in the intake pressure. The maximum indicated efficiency reaches 92.8% when the intake pressure is 1.4 bar and the operation frequency is 2.0 Hz. The indicated efficiency firstly increases and then decreases with the increase in the operation frequency. The COV of the FPE-LG decreases with increasing the intake pressure. The motion stability of FPE-LG improves with the increase in the intake pressure. Valve timing and valve train should be optimized in the near future.

    更新日期:2017-09-15
  • A boundary layer scaling technique for estimating near-surface wind energy using numerical weather prediction and wind map data
    Appl. Energy (IF 7.182) Pub Date : 2017-09-15
    D.J. Allen, A.S. Tomlin, C.S.E. Bale, A. Skea, S. Vosper, M.L. Gallani

    A boundary layer scaling (BLS) method for predicting long-term average near-surface wind speeds and power densities was developed in this work. The method was based on the scaling of reference climatological data either from long-term average wind maps or from hourly wind speeds obtained from high-resolution Numerical Weather Prediction (NWP) models, with case study applications from Great Britain. It incorporated a more detailed parameterisation of surface aerodynamics than previous studies and the predicted wind speeds and power densities were validated against observational wind speeds from 124 sites across Great Britain. The BLS model could offer long-term average wind speed predictions using wind map data derived from long-term observational data, with a mean percentage error of 1.5% which provided an improvement on the commonly used NOABL (Numerical Objective Analysis of Boundary Layer) wind map. The boundary layer scaling of NWP data was not, however, able to improve upon the use of raw NWP data for near surface wind speed predictions. However, the use of NWP data scaled by the BLS model could offer improved power density predictions compared to the use of the reference data sets. Using a vertical scaling of the shape factor of a Weibull distribution fitted to the BLS NWP data, power density predictions with a 1% mean percentage error were achieved. This provided a significant improvement on the use of a fixed shape factor which must be utilised when only long-term average wind speeds are available from reference wind maps. The work therefore highlights the advantages that use of a BLS model for wind speed and NWP data for power density predictions can offer for small to medium scale wind energy resource assessments, potentially facilitating more robust annual energy production and financial assessments of prospective small and medium scale wind turbine installations.

    更新日期:2017-09-15
  • Performance investigation on polymeric electrolyte membrane-based electrochemical air dehumidification system
    Appl. Energy (IF 7.182) Pub Date : 2017-09-15
    Ronghui Qi, Dujuan Li, Li-Zhi Zhang
    更新日期:2017-09-15
  • Indoor thermal comfort assessment using different constructive solutions incorporating PCM
    Appl. Energy (IF 7.182) Pub Date : 2017-09-14
    António Figueiredo, Romeu Vicente, José Lapa, Claudino Cardoso, Fernanda Rodrigues, Jérôme Kämpf

    Sustainable energy and thermal retrofit design of buildings or districts has a strong global impact in the viewpoint of economies and energy-efficiency perspectives. Several aspects such as architectonic design, building materials, construction technology, mechanical systems and outdoor climate determines the thermal behaviour of buildings and their ability to provide indoor thermal comfort to occupants. The use of geothermal energy and phase change materials (PCMs) in the construction systems are an opportunity that may attenuate indoor air temperature fluctuation as well as overheating risk. This paper presents the results of a study on indoor thermal comfort and energy efficiency regarding the PCM’s positive role when applied to new constructive solutions, inside a building with a geothermal system linked to the air conditioning system. The PCM study was based on real and simulated investigations in two rooms of a new university department at the Aveiro campus. Higrothermal monitoring (indoor air temperature) of two rooms in which one of them has PCM panels incorporated into gypsum board partition wall and into a suspended ceiling. The scope was driven to investigate the potential of these solutions for overheating mitigation. The numerical study was conducted by using an evolutionary algorithm coupled with the software EnergyPlus® used in simulations. In the scope of this optimization process, constructive solutions with the incorporation of different types of PCM with different melting temperatures and enthalpy, and different flow rates of natural ventilation were combined to investigate the potential and the payback time of these novel solutions.The results for the room measurements show that the indoor thermal comfort of the rooms, present long periods of discomfort namely in overheating. However, it was proved that the PCM application in one of the rooms lead to an overheating reduction of 7.23% representing a PCM efficiency of 35.49%. After the optimization process an overheating reduction of about 34% was attained by the use of PCM in one of the rooms. Regarding the economic analysis of the use of the PCM for cooling demand reduction, a payback time of 18 years was attained.

    更新日期:2017-09-15
  • Modeling a new energy harvesting pavement system with experimental verification
    Appl. Energy (IF 7.182) Pub Date : 2017-09-14
    Lukai Guo, Qing Lu

    A novel design of an energy harvesting pavement system (EHPS) is introduced in this paper. The basic concept behind this design is to transform asphalt layers into a piezoelectric energy harvester to collect dissipated vehicle kinetic energy in a large-scale system. This EHPS design consists of two conductive asphalt layers and one piezoelectric material layer. To verify the feasibility of the design, this ongoing study theoretically analyzed the EHPS via a three-degree-of-freedom electromechanical model and practically tested a prototype in the laboratory. As a result, voltage outputs measured in the laboratory from the prototype design matched those estimated from the electromechanical model. Through testing the effects of several components in the EHPS on electricity generation, this study confirms that using more flexible conductive asphalt mixtures and arranging more piezoelectric elements with a higher piezoelectric stress constant can increase electrical outputs from the EHPS. Regarding specific external vibration conditions, a high frequency of external vibration can lead to a dramatic effect of each piezoelectric element’s capacitance on increasing electrical outputs, but also can reduce the benefit from adding more piezoelectric elements to produce higher electrical outputs. After optimizing this EHPS prototype by adding more piezoelectric elements with higher piezoelectric stress constant and improving the flexibility of conductive asphalt mixtures, the maximum electric power from the proposed EHPS can be increased from approximately 1.2 mW to 300 mW under a high frequency (30 Hz) external vibration. The levelized cost of electricity of this EHPS can be $19.15/kWh on a high-volume roadway within a 15-year service life.

    更新日期:2017-09-15
  • Factors affecting methane loss from a water scrubbing based biogas upgrading system
    Appl. Energy (IF 7.182) Pub Date : 2017-09-14
    Rimika Kapoor, P.M.V. Subbarao, Virendra Kumar Vijay, Goldy Shah, Shivali Sahota, Dhruv Singh, Mahesh Verma

    Biogas upgrading is a vital step to produce high quality fuel called biomethane with above 90% methane (CH4). Among the various technologies available for biomethane production, water scrubbing is the most extensively implemented technology around the world. However, during the process of biogas upgrading, a some amount of CH4 is separated as CH4 loss through the water flowing out of the water scrubbing column. In this paper, various factors affecting CH4 loss from water scrubbing method are analysed. Some factors such as pressure, water flow rate and CH4 concentration in input gas are dependent upon the solubility and partial pressures of the gases are generally known. Apart from these factors CH4 losses due to bubble entrainment due to high pressure difference between water scrubbing column and desorption tank and gas short circuiting of the gas through the bottom section of the column due to no water sealing and water level maintencence also contribute to CH4 losses. Therefore, CH4 losses during the water scrubbing process due to these factors have been experimentally studied in this paper. A pilot scale water scrubbing system for biogas upgradation was used for the study. It was observed that CH4 % (v/v) in the upgraded biogas and CH4 loss % from the desorbed gas increased with the increase in pressure and increase in the concentration of CH4 in the input gas. Increase in water flow rates caused removal of larger quantities of water containing more absorbed CH4 and CO2 from the scrubbing column, thereby increasing CH4 loss of the system. Highest CH4 loss % of 9.9% (±0.1%), was obtained with raw biogas sample when water was desorbed at atmospheric pressures in the desorption tank, i.e. when pressure difference between the water scrubbing column and desorption tank was highest. A pressure vessel was installed in between scrubbing column and desorption tank to reduce the pressure difference for water leaving the column by varying the pressure in the pressure vessel from 1 to 9 bar. With the increase in pressure in the pressure vessel, the pressure difference for water decreased which led to a saving in overall CH4 loss of the system. Water sealing and water level maintenance in the bottom section of the column also affected CH4 losses of the system. All the factors discussed in the article contribute to the CH4 losses from the scrubbing column and cannot be solely credited to a single factor.

    更新日期:2017-09-15
  • Offshore wind farm repowering optimization
    Appl. Energy (IF 7.182) Pub Date : 2017-09-14
    Peng Hou, Peter Enevoldsen, Weihao Hu, Cong Chen, Zhe Chen

    Decommissioning is usually the last stage of the offshore wind farm life cycle. Due to the challenges of the decommissioning process, such as the impact on the marine environment, severe weather conditions, vessel limitations and lack of operational experience, the decommissioning strategy should be planned to avoid complications, which ultimately can cause radical changes to the levelized cost of energy (LCoE) and the wind farm owner’s business case. Instead of dismantling, repowering may be a sustainable alternative solution to extend the lifetime of a wind farm. In this paper, the research is focused on optimization of offshore wind farm repowering, which is one option for the wind farm owner at end of life for the offshore wind farm. The LCoE is used as the evaluation index to identify whether it is economical to invest in such a way. In an optimized repowering strategy, different types of wind turbines are selected to replace the original wind turbines to reconstruct the wind farm, which is demonstrated to be better than the refurbishment approach which replaces the old wind turbines with the same type. The simulations performed in this research reveal that the reconstructed wind farm, which consists of multiple types of wind turbine, has a smaller LCoE (10.43%) than the refurbishment approach, which shows the superiority of the proposed method. This research contributes an optimization tool to the wind industry, which consequently drives down the cost of energy produced by offshore wind turbines.

    更新日期:2017-09-15
  • A comparison of radial-flow and axial-flow packed beds for thermal energy storage ☆
    Appl. Energy (IF 7.182) Pub Date : 2017-09-14
    J.D. McTigue, A.J. White

    Packed-bed thermal reservoirs are an integral component in a number of electrical energy storage technologies. The present paper concentrates on packed beds where the heat transfer fluid travels along the radial co-ordinate. The governing energy equations and various mechanisms that cause exergetic losses are discussed. The radial-flow packed bed is compared to a dimensionally similar axial-flow packed bed. This approach provides a fair assessment of the underlying behaviour of the two designs. Multi-objective optimisation allows a wide range of design variables to be considered, and is employed to compare optimal radial-flow and axial-flow stores. Axial-flow stores that have been segmented into layers are also considered. The results indicate that radial-flow stores have a comparable thermodynamic performance, but that the additional volume required for by-pass flows leads to higher capital costs.

    更新日期:2017-09-14
  • Comparative study of the transient natural convection in an underground water pit thermal storage
    Appl. Energy (IF 7.182) Pub Date : 2017-09-14
    Chun Chang, Zhiyong Wu, Helena Navarro, Chuan Li, Guanghui Leng, Xiaoxia Li, Ming Yang, Zhifeng Wang, Yulong Ding
    更新日期:2017-09-14
  • Quantitative analysis on the impact of nuclear energy supply disruption on electricity supply security
    Appl. Energy (IF 7.182) Pub Date : 2017-09-13
    Shoki Kosai, Hironobu Unesaki

    Improvement of power supply security is of paramount importance to sustain human activities. Technical and engineering failures of power grid system have been analyzed to evaluate power system reliability hitherto. However, after Fukushima nuclear accident, the sudden electricity supply disruption particularly associated with nuclear energy utilization brings upon a new risk of electricity supply security arising from societal issues, or nuclear vulnerability. As such, a methodology of quantifying nuclear vulnerability is firstly established under varying both the magnitude and time instant of sudden stoppage of nuclear power operation. Through the nuclear vulnerability analysis, a new electricity supply security index dedicated for nuclear power utilization, named System Interruption Nuclear Vulnerability Index (SINVI) is developed. SINVI could be used to predict the risk of electricity supply disruption arising from the sudden stoppage of nuclear power operation corresponding to the different capacity combination of various energy sources. Finally, the widely proposed dimensions of energy security for undisturbed electricity supply – diversification and redundancy – are incorporated with nuclear vulnerability to design the more secured power system taking into account the risk of nuclear energy utilization. The established algorithm can be readily implemented in any other electricity grid network including nuclear power technology.

    更新日期:2017-09-14
  • Flame height of axisymmetric gaseous fuel jets restricted by parallel sidewalls: Experiments and theoretical analysis
    Appl. Energy (IF 7.182) Pub Date : 2017-09-13
    Qiang Wang, Fei Tang, Zheng Zhou, Huan Liu, Adriana Palacios

    This study reports experimental results and correlations for axisymmetric gaseous fuel jets restricted by parallel sidewalls at various separation distances. Although many investigations have been conducted to elucidate the flame height evolution of diffusion flames in an unrestricted environment; the restriction effect of sidewalls on diffusion flames, which occasionally occurs in accidental leakages of city natural gas pipelines, has received little attention. The underlying interaction dynamics of axisymmetric gaseous fuel jets with two parallel sidewalls at various separation distances has not been fully elucidated. In this work, a series of experiments on this issue were carried out with 3-, 6- and 10-mm nozzles. The sidewall separation distances were varied from 10 to 50 cm with a corresponding free condition. A series of new results and their interpretation are presented in this work. The results show that the flame height changes little when the sidewall separation distance reduces from +∞ to a critical value (Scri). Further reductions on the sidewall separation distance from Scri disturbed the evolution process of uprising vortexes and hindered air entrainment, leading to significant changes to the jet-flame shape by enlarging the flame height. The maximum flame heights had a linear relation with the critical separation distance of the sidewalls at the critical conditions, being consistent with the scaling analysis of the flow field. The dimensionless critical separation distance was found to be well correlated with the dimensionless heat release rate, View the MathML source Q ̇ D ∗ , with a 2/5 power law. A global model, characterizing the variation of the flame height with the dimensionless heat release rate, was proposed, showing good agreement with the experimental results. The results and the expressions obtained in this study contribute to a better understanding of jet fires, allowing a better prediction of flame height, relevant to the design of gas fuel storage systems and transportation systems in the city.

    更新日期:2017-09-14
  • Evaluation and comparison of product yields and bio-methane potential in sewage digestate following hydrothermal treatment
    Appl. Energy (IF 7.182) Pub Date : 2017-09-13
    C. Aragón-Briceño, A.B. Ross, M.A. Camargo-Valero

    In recent years, sewage sludge management has been considered one of the biggest concerns in the wastewater industry for the environmental impacts linked to its high content of pollutants. Hydrothermal Treatments are a good option for converting wet biomass such as sewage sludge into high-value products. The digestate following anaerobic treatment of sewage sludge has high organic matter content despite initial conversion into biogas and is normally spread on land or composted; however, this does not fully harness its full potential. In fact, the digestate is a potential feedstock for hydrothermal processing and this route may produce higher value products. In this study, the potential of hydrothermal processing as a novel alternative to treat the digestate has been be evaluated. The effect of temperatures is evaluated with respect to product yields, biomethane potential and solubilisation of organic carbon. Three different temperatures were evaluated: 160, 220 and 250 °C at 30 min reaction time. The hydrochar yields obtained were 73.42% at 220 °C, 68.79% at 250 °C and 56.75% at 160 °C treatment. The solubilisation of carbon was increased from 4.62% in the raw feedstock to 31.68%, 32.56% and 30.48% after thermal treatments at 160, 220 and 250 °C, respectively. The thermal treatment enhanced the potential methane production in all products up to 58% for both, the whole fraction (hydrochar + processed water) and processed waters. The Boyle’s and Buswell’s equation were used to calculate theoretical methane yields for all hydrothermal products. Theoretical methane yields were compare with experimental data from biomethane potential (BMP) tests and it was found that the Boyle’s equation had closer agreement to BMP values.

    更新日期:2017-09-14
  • Evaluation and comparison of an adaptive method technique for improved performance of linear Fresnel secondary designs
    Appl. Energy (IF 7.182) Pub Date : 2017-09-13
    Madeline Hack, Guangdong Zhu, Tim Wendelin

    As a line-focus concentrating solar power (CSP) technology, linear Fresnel collectors have the potential to become a low-cost solution for electricity production and a variety of thermal energy applications. However, this technology often suffers from relatively low performance. A secondary reflector is a key component used to improve optical performance of a linear Fresnel collector. The shape of a secondary reflector is particularly critical in determining solar power captured by the absorber tube(s), and thus, the collector’s optical performance. However, to the authors’ knowledge, no well-established process existed to derive the optimal secondary shape prior to the development of a new adaptive method to optimize the secondary reflector shape. The new adaptive method does not assume any pre-defined analytical form; rather, it constitutes an optimum shape through an adaptive process by maximizing the energy collection onto the absorber tube. In this paper, the adaptive method is compared with popular secondary-reflector designs with respect to a collector’s optical performance under various scenarios. For the first time, a comprehensive, in-depth comparison was conducted on all popular secondary designs for CSP applications. It is shown that the adaptive design exhibits the best optical performance.

    更新日期:2017-09-14
  • Non-intrusive load monitoring by using active and reactive power in additive Factorial Hidden Markov Models
    Appl. Energy (IF 7.182) Pub Date : 2017-09-13
    Roberto Bonfigli, Emanuele Principi, Marco Fagiani, Marco Severini, Stefano Squartini, Francesco Piazza

    Non-intrusive load monitoring (NILM) is the task of determining the appliances individual contributions to the aggregate power consumption by using a set of electrical parameters measured at a single metering point. NILM allows to provide detailed consumption information to the users, that induces them to modify their habits towards a wiser use of the electrical energy. This paper proposes a NILM algorithm based on the joint use of active and reactive power in the Additive Factorial Hidden Markov Models framework. In particular, in the proposed approach, the appliance model is represented by a bivariate Hidden Markov Model whose emitted symbols are the joint active-reactive power signals. The disaggregation is performed by means of an alternative formulation of the Additive Factorial Approximate Maximum a Posteriori (AFAMAP) algorithm for dealing with the bivariate HMM models. The proposed solution has been compared to the original AFAMAP algorithm based on the active power only and to the seminal approach proposed by Hart (1992), based on finite state machine appliance models and which employs both the active and reactive power. Hart’s algorithm has been improved for handling the occurrence of multiple solutions by means of a Maximum A Posteriori technique (MAP). The experiments have been conducted on the AMPds dataset in noised and denoised conditions and the performance evaluated by using the F1 F 1 -Measure and the normalized disaggregation metrics. In terms of F1 F 1 -Measure, the results showed that the proposed approach outperforms AFAMAP, Hart’s algorithm, and Hart’s with MAP respectively by +14.9% + 14.9 % , +21.8% + 21.8 % , and +2.5% + 2.5 % in the 6 appliances denoised case study. In the 6 appliances noised case study, the relative performance improvement is +25.5% + 25.5 % , +51.1% + 51.1 % , and +6.7% + 6.7 % .

    更新日期:2017-09-13
  • Tolerance analysis of electrified vehicles on the motor demagnetization fault: From an energy perspective
    Appl. Energy (IF 7.182) Pub Date : 2017-09-12
    Hongwen He, Nana Zhou, Jinquan Guo, Zheng Zhang, Bing Lu, Chao Sun

    Due to possible overheat, abrasion or mechanical vibrations, demagnetization fault is inevitable in permanent magnet synchronous motors (PMSMs), which could greatly decrease the motor’s efficiency and hence an electrified vehicle’s performance. This paper, from an energy efficiency point of view, proposes to analyze the tolerance ability of different electrified vehicles on motor demagnetization faults, via PMSM flux density degradation modeling, efficiency estimation and dynamic programming (DP) based powertrain energy management. The relationship between different demagnetization levels and resultant motor efficiencies is obtained, and analyzed according to the motor operation area. Demagnetized PMSM is adopted in a pure electric vehicle (PEV), a hybrid electric vehicle (HEV) and a plug-in hybrid electric vehicle (PHEV) for energy efficiency analysis. Tolerance analysis indicates that the powertrain efficiency decrease caused by motor demagnetization is more severe under urban driving conditions, especially with PEV and PHEV configurations compared with HEV. A demagnetization threshold investigation is also given in this paper.

    更新日期:2017-09-12
  • Multi-objective optimization design and performance evaluation for plug-in hybrid electric vehicle powertrains
    Appl. Energy (IF 7.182) Pub Date : 2017-09-12
    Xingyu Zhou, Datong Qin, Jianjun Hu

    This study provides an optimal selection methodology for plug-in hybrid electric vehicle (PHEV) powertrain configuration by means of optimization and comprehensive evaluation of powertrain design schemes. The challenge of this study is to reveal each powertrain configuration performance potential in different situations of object trade-off and solve the control-physical integrated optimization problem of the PHEV powertrain design. To determine performance potential, a configuration-sizing-control strategy integrated multi-objective powertrain optimization design is proposed and applied to series, parallel pre-transmission (P2), output power-split, and multi-mode power-split powertrain configurations. Firstly, considering simultaneous optimization of fuel economy, electric energy consumption, and acceleration capacity, the parameters of the powertrain components and vehicle performance of each configuration are optimized based on global optimal control in different situations of object trade-off. Then, the Pareto optimal selection of powertrain configuration and its corresponding optimal component parameters are obtained by performance comparison and non-domination sorting. The results suggest that the P2 configuration and its optimal sizing can be selected when the goal is to optimize acceleration capacity, the multi-mode power-split configuration and its optimal sizing can be selected when the goal is to optimize electric energy efficiency, and the output power-split configuration and its optimal sizing can be selected when the fuel economy needs to be optimized.

    更新日期:2017-09-12
  • A multi-scale framework for simultaneous optimization of the design and operating strategy of residential CHP systems
    Appl. Energy (IF 7.182) Pub Date : 2017-09-12
    Abigail Ondeck, Thomas F. Edgar, Michael Baldea

    The expected increase in energy demand in the United States has led to the pursuit of more efficient methods to generate thermal and electrical energy for the residential sector. One possible approach that could both increase generation efficiency and reduce CO2 emissions is Combined Heat and Power (CHP). CHP plants, powered by natural gas, can act as an integrated residential utility supplier by producing the thermal and electrical energy needed to meet the heating, cooling, and electricity demands of a (future) residential neighborhood. However, a CHP plant operating in island (i.e., grid-disconnected) mode must be optimally sized to maximize efficiency and to lower the capital and marginal costs. In this paper, we describe a novel simultaneous optimization of design and operating strategies for a CHP plant as a utility producer for a residential neighborhood. The plant, operating in island mode, integrates distributed residential photovoltaic solar power generation, and is optimized to meet a time-dependent energy demand profile characteristic of residential energy use. To accurately capture the variability (hourly and seasonal) and uncertainty in residential energy demand and rooftop photovoltaic generation, a vast amount of energy data were incorporated in the problem formulation. The multi-scale optimization problem was solved using a temporal Lagrangean decomposition method, generating the design of a CHP plant that can efficiently meet all residential utility demands, taking into consideration the long-term (design) and short-term (operational) costs.

    更新日期:2017-09-12
  • Designing efficient distribution network charges in the context of active customers
    Appl. Energy (IF 7.182) Pub Date : 2017-09-11
    Ibtihal Abdelmotteleb, Tomás Gómez, José Pablo Chaves Ávila, Javier Reneses

    The transformation of electricity network users from passive to active agents, as a result of decreasing costs of distributed energy resources, requires several adaptions, one of which is revising the distribution network charges. Often current network charge designs do not ensure network cost recovery and lack to incentivize efficient network investments and usage. New network charge methodologies are required to guide and incentivize customers in an efficient way while maximizing system economic efficiency. This paper proposes an efficient methodology that ensures network cost recovery while promoting efficient usage of the network as well as efficient network investments. The proposed network charge design consisting of two components: a peak coincidence network charge (PCNC) and fixed charge. The PCNC is a forward-looking charge as it considers the cost of future network reinforcements required and assigned to customers during peak hours of the network utilization. Fixed charges allocate the residual of the network costs following Ramsey-pricing principles. This paper compares the outcome from economic optimum customers’ response to four different network charges: (i) volumetric charges (ii) fixed charges (iii) peak demand charge (iv) PCNC plus fixed charges. Two case studies for two different load profiles are simulated using linear programming to minimize their total costs within each charges design, considering the possibility of buying electricity from the grid and investing on onsite generation or curtail load. Finally, the paper highlights through the case studies how customer’s response is highly influenced by different network charge designs, and compares the consequences of these responses in terms of network cost recovery and total system costs. The paper concludes with practical issues that need to be considered for the implementation of the proposed network charges design.

    更新日期:2017-09-11
  • Evaluation of energy efficient hybrid hollow plaster panel using phase change material/xGnP composites
    Appl. Energy (IF 7.182) Pub Date : 2017-09-09
    Seunghwan Wi, Su-Gwang Jeong, Seong Jin Chang, Jongki Lee, Sumin Kim
    更新日期:2017-09-10
  • Performance assessment of a hybrid SOFC/MGT cogeneration power plant fed by syngas from a biomass down-draft gasifier
    Appl. Energy (IF 7.182) Pub Date : 2017-09-09
    Alessandra Perna, Mariagiovanna Minutillo, Elio Jannelli, Viviana Cigolotti, Suk Woo Nam, Kyung Joong Yoon

    Hybrid systems combine two or more power generating devices and make use of the synergism to generate maximum power and offer very high efficiencies.The aim of this work is to investigate the performance achievable from a small-scale hybrid power plant based on the integration between a micro gas turbine (MGT) and a solid oxide fuel cell (SOFC) fed by the syngas generated by a biomass downdraft gasifier (BG). The thermal energy needed to reach the turbine inlet temperature is supplied by the exhausts coming from a catalytic burner in which the SOFC anode and cathode off-gases are burnt.The hybrid BG-SOFC/MGT plant, based on a simplified configuration and realized considering components commercially available, is designed for optimizing not only the electric power generation, but also the thermal power production, in accordance with the promotion of decentralized CHP plants.The performance assessment has been carried out by means of a numerical model, based on thermodynamic/thermochemical approaches and realized by integrating the models of each plant section, developed by using the Aspen Plus software package. The models validation, performed by using experimental data, demonstrates that the results produced are close to those obtained from each unit, so that the overall integrated model can provide a sufficiently accurate prediction of the expected actual hybrid power plant.The effects of some operating parameters on cogeneration performances, such as the MGT pressure ratio and the S/C (steam to carbon) in the SOFC unit, have been evaluated and analyzed.Results show that the best performances are achieved by assuming the MGT pressure ratio equal to 4.5 and the S/C equal to 0. In this case the electric power is 262 kW (SOFC supplies 180 kW), the thermal power is 405 kW and the electric (AC) and cogeneration efficiencies are 35% and 88%, respectively.

    更新日期:2017-09-10
  • Demand forecast of PV integrated bioclimatic buildings using ensemble framework
    Appl. Energy (IF 7.182) Pub Date : 2017-09-09
    Muhammad Qamar Raza, Mithulananthan Nadarajah, Chandima Ekanayake

    Buildings are one of the major sources of electricity and greenhouse gas emission (GHG) in urban areas all around the world. Since a large integration of solar energy is observed in the form of rooftop photovoltaic (PV) units, electricity use of buildings is highly uncertain due to intermittent nature of solar output power. This leads to poor energy management for both network operators and building owners. In addition, uncertain metrological conditions, diversity and complexity of buildings are big hurdles to accurate prediction of the demand. To improve accuracy of load demand forecast of PV integrated smart building, a hybrid ensemble framework is proposed in this paper. This is based on a combination of five different predictors named as backpropagation neural network (BPNN), Elman neural network (EN), Autoregressive Integrated Moving Average (ARIMA), feed forward neural network (FNN), radial basis function (RBF) and their wavelet transform (WT) models. WT is applied to historical load data to remove the spikes and fluctuations. FNN and RBF network were trained with particle swarm optimization (PSO) for higher forecast accuracy. The output of each predictor in the ensemble network is combined using Bayesian model averaging (BMA). The proposed framework is tested using real data of two practical PV integrated smart buildings in a big university environment. The results indicate that the proposed framework show improvement in average forecast normalized root mean square error (nRMSE) around 17% and 20% in seasonal daily and seasonal weekly case studies, respectively. In addition, proposed framework also produces lowest of nRMSE about 3.88% in seasonal monthly forecast of smart buildings with rooftop PV as compared to benchmark model. The proposed forecast framework provides consistent forecast results for global change institute (GCI) and advance engineering building (AEB) during seasonal daily and weekly comparison.

    更新日期:2017-09-09
  • Water-energy nexus: A review of methods and tools for macro-assessment
    Appl. Energy (IF 7.182) Pub Date : 2017-09-07
    Jiangyu Dai, Shiqiang Wu, Guoyi Han, Josh Weinberg, Xinghua Xie, Xiufeng Wu, Xingqiang Song, Benyou Jia, Wanyun Xue, Qianqian Yang

    Over the past decade, analyzing issues within the ‘water-energy nexus’ has become a topic of increasing attention for the scientific and policy communities. Based on an extensive survey of recent scientific literature on the water-energy nexus, 70 studies were identified and 35 were selected as comprehensive case studies for review. The reviewed studies were classified and assessed according to groupings based on both geographic scale and their ‘nexus scope’. In addition to providing a depository summary of a wide range of current existing methods and tools for water-energy nexus analysis, the paper discusses these approaches based on their main purposes. From this review, it is clear that the research on water-energy nexus has seen a significant increase in both the number of studies and the capacity of the scientific community to productively assess water and energy interlinkages at a higher resolution. At the same time, this review has also concluded that, while many studies aim to develop new methods and frameworks to comprehensively assess interactions between water, energy and other elements, none can or do provide a singular framework for performing a “nexus study”. Furthermore, many researches are at the “understanding” stage with an emphasis on the quantitative analysis of the water-energy nexus. Fewer approaches are designed to support governance and implementation of technical solutions, and this is considered to a priority challenge area for the scientific community if it aims to achieve greater impact on resource policy and management. There is a clear need to improve our ability to classify and compare the capacities, strengths and weaknesses between existing approaches. This would better enable a wider group of stakeholders to utilize existing knowledge to improve their effective management of water and energy resources. It could also help focus the scientific community to more effectively improve upon the existing knowledge base and to increase focus on “governing” and “implementing” the nexus.

    更新日期:2017-09-07
  • A new reliability assessment approach for integrated energy systems: Using hierarchical decoupling optimization framework and impact-increment based state enumeration method
    Appl. Energy (IF 7.182) Pub Date : 2017-09-06
    Yunkai Lei, Kai Hou, Yue Wang, Hongjie Jia, Pei Zhang, Yunfei Mu, Xiaolong Jin, Bingyan Sui

    A new reliability assessment approach to Integrated Energy Systems (IESs) is introduced in this paper. The optimal load curtailment (OLC) algorithm and reliability assessment algorithm are both improved in the proposed approach. For the OLC problem, this paper develops a hierarchical decoupling optimization framework for both the energy hub optimal dispatch and the optimal power flow problems. This feasible solution can make the OLC calculation more efficient and accurate. For the reliability assessment algorithm, an impact-increment based state enumeration (IISE) method is accommodated for IESs to accelerate the reliability assessment process. Also, a reduction technique of higher order contingencies is presented for the reliability evaluation of IESs to further enhance the computational efficiency. Case studies are performed on an IESs test case combined the IEEE-33 bus system with 14-node gas system and a practical case combined the IEEE 118-bus power system with Belgian natural gas network Numerical results demonstrate the efficient and robust performance of the proposed approach. Besides, the impacts of energy conversion process and energy hubs on IESs reliability are analyzed in detail.

    更新日期:2017-09-07
  • Modeling constraints to distributed generation solar photovoltaic capacity installation in the US Midwest
    Appl. Energy (IF 7.182) Pub Date : 2017-09-05
    Tyson Cook, Lee Shaver, Paul Arbaje
    更新日期:2017-09-06
  • Optimization problem for meeting distribution system operator requests in local flexibility markets with distributed energy resources
    Appl. Energy (IF 7.182) Pub Date : 2017-09-01
    Pol Olivella-Rosell, Eduard Bullich-Massagué, Mònica Aragüés-Peñalba, Andreas Sumper, Stig Ødegaard Ottesen, Josep-Andreu Vidal-Clos, Roberto Villafáfila-Robles

    The increasing penetration of distributed energy resources in the distribution grid is producing an ever-heightening interest in the use of the flexibility on offer by said distributed resources as an enhancement for the distribution grid operator. This paper proposes an optimization problem which enables satisfaction of distribution system operator requests on flexibility. This is a decision-making problem for a new aggregator type called Smart Energy Service Provider (SESP) to schedule flexible energy resources. This aggregator operates a local electricity market with high penetration of distributed energy resources. The optimization operation problem of SESP is formulated as an MILP problem and its performance has been tested by means of the simulation of test cases in a local market. The novel problem has also been validated in a microgrid laboratory with emulated loads and generation units. The performed tests produced positive results and proved the effectiveness of the proposed solution.

    更新日期:2017-09-04
  • Receding horizon optimization-based approaches to managing supply voltages and power flows in a distribution grid with battery storage co-located with solar PV ☆
    Appl. Energy (IF 7.182) Pub Date : 2017-09-01
    Elizabeth L. Ratnam, Steven R. Weller

    In this paper we propose two optimization-based algorithms for coordinating residential battery storage to balance increases in daily operational savings that accrue to residential customers with the management of bi-directional power flows in the distribution grid. Bi-directional power flows are managed to improve the supply voltage for residential customers with rooftop solar PV, in addition to alleviating (potentially infrequent) congestion that occurs in the evening when PV production is unavailable. Our objectives are threefold: (1) to reduce reverse power flow leading to significant voltage rise; (2) to reduce peak loads creating sustained under-voltages and/or approaching a network thermal capacity; and (3) to increase operational savings for the residential customer. To achieve our objectives we present a Distributed-Receding Horizon Optimization (D-RHO) algorithm, wherein charge and discharge rates of residential battery storage are coordinated so as to directly influence power flows along a distribution feeder. We also present an Adaptive-Receding Horizon Optimization (A-RHO) algorithm, in which charge and discharge rates of residential battery storage are coordinated to more directly manage supply voltages. To assess the distributor benefit, both RHO-based algorithms are applied to a publicly available model of an Australian distribution region located in Elermore Vale. The results of this case study confirm that the A-RHO algorithm improves supply voltages in a low voltage network, and that the D-RHO algorithm offers a peak load reduction of 32% along the Elermore Vale medium voltage feeder.

    更新日期:2017-09-04
  • Optimal coordinated energy dispatch of a multi-energy microgrid in grid-connected and islanded modes
    Appl. Energy (IF 7.182) Pub Date : 2017-08-31
    Zhengmao Li, Yan Xu

    This paper proposes a system-wide optimal coordinated energy dispatch method for a multi-energy microgrid in both the grid-connected and islanded modes. The studied microgrid consists of multiple energy carriers covering the controllable generation units (fuel cell, electric boiler, combined cooling, heat and power plant and electric chiller), uncontrollable generation units (wind turbine and photovoltaic cell) and energy storage devices (battery storage, heat storage tank and ice storage tank). The proposed energy dispatch method aims to minimize the microgrid net operating cost and enhance the dispatch flexibility in supplying power, heat and cooling in the day-ahead energy market. For both the grid-connected and islanded microgrid, their dispatch models are formulated as the mixed-integer linear programming problems, which can be efficiently solved by the commercial solvers. Comprehensive case studies are performed to evaluate the effectiveness of the proposed method and then compared with the traditional dispatch methods which supply power and heat/cooling energies separately. Simulation results demonstrate that the proposed method can achieve much higher operating efficiency.

    更新日期:2017-09-04
  • Coupling detailed radiation model with process simulation in Aspen Plus: A case study on fluidized bed combustor
    Appl. Energy (IF 7.182) Pub Date : 2017-08-31
    Yukun Hu, Jihong Wang, CK Tan, Chenggong Sun, Hao Liu

    While providing a fast and accurate tool for simulating fluidized beds, the major limitations of classical zero-dimensional ideal reactor models used in process simulations become irreconcilable, such as models built into commercial software (e.g. Aspen Plus®). For example, the limitations of incorporating heat absorption by the water wall and super-heaters and inferring thermal reciprocity between each reactor model/module. This paper proposes a novel modelling approach to address these limitations by incorporating an external model that marries the advantages of the zone method and Aspen Plus to the greatest extent. A steady state operation of a 0.3 MW atmospheric bubbling fluidized-bed combustor test rig was simulated using the developed modelling approach and the results were compared with experimental data. The comparison showed that the predictions were in agreement with the measurements. Further improvement is to be expected through incorporating more realistic zoned geometry and more complex reaction mechanisms. In addition, the developed model has a relatively modest computing demand and hence demonstrates its potential to be incorporated into process simulations of a whole power plant.

    更新日期:2017-09-04
  • How will sectoral coverage affect the efficiency of an emissions trading system? A CGE-based case study of China
    Appl. Energy (IF 7.182) Pub Date : 2017-08-31
    Yaqian Mu, Samuel Evans, Can Wang, Wenjia Cai

    This study contributes to the existing literature on optimal carbon mitigation policy by quantifying the impacts of various sectoral coverage options for the emissions trading systems (ETS) used to achieve China’s Intended Nationally Determined Contribution (INDC) targets for the Paris Agreement on climate change. The CHEER model, a computable general equilibrium (CGE) model of China with detailed representation of electricity and other energy intensive sectors, as well as a complete CO2 emissions accounting module and carbon market, is used in this study. Results show several important findings. First, China’s INDC targets can be achieved through an economy-wide ETS at an economic cost of 2.1% of real GDP by 2030. Second, including only the eight sectors proposed for initial implementation of the ETS in China is likely to result in a much larger mitigation cost than the economy-wide approach, estimated to be as high as 10.5% of 2030 real GDP. Thirdly, this study further indicates that the mitigation costs can be reduced to 3.3% of real GDP in 2030 if other energy-intensive sectors, accounting for additional 24.8% of total emissions, are included in the ETS. As a result, not all sectors are required to get close to the first-best mitigation option so long as critical sectors are not excluded. In addition, the temporal dimension of mitigation costs and air pollution co-benefits under different sectoral schemes of China’s ETS gives policy-makers a degree of short-run flexibility in terms of phasing in additional industries over time.

    更新日期:2017-09-04
  • Predictive air-conditioner control for electric buses with passenger amount variation forecast☆
    Appl. Energy (IF 7.182) Pub Date : 2017-08-31
    Hongwen He, Mei Yan, Chao Sun, Jiankun Peng, Menglin Li, Hui Jia

    Air-conditioners (AC) usually consume the most electricity among all of the auxiliary components in an electric bus, over 30% of the battery power at maximum. On-board passengers carried by the electric bus are important but random heat sources, which are obsessional disturbances for the cabin temperature control and energy management of the AC system. This paper aims to improve the AC energy efficiency via passenger amount variation analysis and forecast in a model predictive control (MPC) framework. Three forecasting approaches are proposed to realize the passenger amount variation prediction in real-time, namely, stochastic prediction based on Monte Carlo, radial basis function neural network (RBF-NN) prediction, and Markov-chain prediction. A sample passenger number database along a typical bus line in Beijing is built for passenger variation pattern analysis and forecast. A comparative study of the above three prediction approaches with different prediction lengths (bus stops in this case) is conducted, from both the energy consumption and temperature control perspectives. A predictive AC controller is developed, and evaluated by comparing with Dynamic Programming (DP) and a commonly used rule-based control strategy. Simulation results show that all the three forecasting methods integrated within the MPC framework are able to achieve more stable temperature performance. The energy consumptions of MPC with Markov-chain prediction, RBF-NN forecast and Monte Carlo prediction are 6.01%, 5.88% and 5.81% lower than rule-based control, respectively, on the Beijing bus route studied in this paper.

    更新日期:2017-09-04
  • Life cycle sustainability assessment of grid-connected photovoltaic power generation: A case study of Northeast England
    Appl. Energy (IF 7.182) Pub Date : 2017-08-31
    Tianqi Li, Anthony Paul Roskilly, Yaodong Wang

    This paper proposes a comprehensive sustainability assessment model incorporating (a) life cycle approach and sustainability theory. In the model, sustainability is assessed from three categories: techno-economic, environmental and social. A total of thirteen indicators were included in the proposed model, with five evaluating the techno-economic performance, six evaluating the environmental performance, and two examining the social impact. The effectiveness of this model is then demonstrated through its application to a case study of solar photovoltaic in the North East region of England. Three types of the most commonly deployed solar photovoltaic electricity generation systems are included in the case study: monocrystalline (s-Si), polycrystalline (p-Si) and Cadmium telluride (CdTe) thin film.The multi-silicon solar photovoltaic system is found to be the most sustainable option for its high performance in the techno-economic and environmental categories; the CdTe based system is the least-favoured option across all three categories; and the polycrystalline system has the best performance across all categories. Energy conversion efficiency appears to be one of the most influential factors for the solar photovoltaic system’s sustainability performance. Despite being the least costly system among the three, the CdTe system appears to be the least financially viable option mainly due to its low energy-conversion efficiency.This study estimates the environmental impact of selected technologies using the CML2001 method and then employs ReCiPe method to cross-validate the estimated results. Identical results were found for all indicators apart from eutrophication potential, due to the difference in impact quantification methods between CML and ReCiPe.

    更新日期:2017-09-04
  • Effects of increased spark discharge energy and enhanced in-cylinder turbulence level on lean limits and cycle-to-cycle variations of combustion for SI engine operation
    Appl. Energy (IF 7.182) Pub Date : 2017-08-31
    Dongwon Jung, Kosaku Sasaki, Norimasa Iida

    Improving the thermal efficiency of spark ignition (SI) engines is strongly required due to its widespread use but considerably less efficiency than that of compression ignition (CI) engines. Although lean SI engine operation can offer substantial improvements of the thermal efficiency relative to that of traditional stoichiometric SI operation, the cycle-to-cycle variations of combustion increase with the level of air dilution, and become unacceptable. For improving the thermal efficiency by extending the lean-stability limit, this study examines the effects of spark discharge energy and in-cylinder turbulence level on lean limits and cycle-to-cycle variations of combustion for SI engine operation. The spark discharge energy was increased by a high-energy inductive ignition system using ten spark coils and the in-cylinder turbulence level was enhanced by a custom adapter installed in the intake port.The results show that increased spark discharge energy by ten spark coils is effective at shifting the lean-stability limit to leaner operation, compared to that of a single spark coil. With shift of the lean-stability limit, significant improvement of thermal efficiency is observed, relative to that of stoichiometric operation. Furthermore, a combination of increased spark discharge energy and enhanced in-cylinder turbulence level makes it possible to allow stable operation at more extended lean-stability limit. This is mainly attributed to shortening the durations of spark timing-to-CA5 and CA10-to-CA90 by both increased spark discharge energy and enhanced in-cylinder turbulence level. However, the cycle-to-cycle variations of SI combustion increase with increasing excess-air ratio even for operation by ten spark coils with the intake port adapter. Finally, the relationship between the spark discharge energy and the SI combustion is examined and compared for ultra-lean operation without and with the intake port adapter. Although indicated thermal efficiency is improved by increased spark discharge energy, the variations of the spark discharge energy do not relate to the variations of the combustion, since total spark discharge energy does not affect both durations of the spark timing-to-CA5 and the CA10-to-CA90, and eventually the heat-release efficiency.

    更新日期:2017-09-04
  • Thermophotovoltaic power conversion using a superadiabatic radiant burner
    Appl. Energy (IF 7.182) Pub Date : 2017-08-31
    H. Wu, M. Kaviany, O.C. Kwon

    A new configuration of a 5–10 W thermophotovoltaic (TPV) device integrated with a porous superadiabatic radiant burner (SRB) is suggested and experimentally studied. The silicon carbide (SiC) SRB (emitter) consists of a small-pored upstream section (PM1) and a large-pored downstream section (PM2). PM1 is the section where the incoming fuel-air mixture is preheated internally and PM2 is the section where flame is established. Also, a separate preheater is attached on the SRB to externally recover heat from the exiting flue gas and preheat the inlet air for the burner, and radiation rods are embedded at the interface between the PM1 and PM2 to extract heat from the flame and transfer it to radiating disk surfaces. Radiation from the disk surface is used for the TPV power conversion, reaching gallium antimonide photovoltaic cells (PVCs) with proper quantum efficiencies (up to 80%) through a quartz plate for preventing direct convectional heat transfer from the exhaust gas onto the PVCs. Under optimized conditions, uniform radiation provides adequate TPV performance, particularly indicating reasonable emitter efficiencies (up to 32%) with the enhanced disk temperature even for fuel-lean condition. Thus, the present configuration of the SRB-integrated TPV device can be used in practical applications, avoiding high-level noise without any moving parts.

    更新日期:2017-09-04
  • Mixed-integer linear programming-based optimal configuration planning for energy hub: Starting from scratch
    Appl. Energy (IF 7.182) Pub Date : 2017-08-31
    Yi Wang, Ning Zhang, Zhenyu Zhuo, Chongqing Kang, Daniel Kirschen
    更新日期:2017-09-04
  • Economic and energetic analysis of biofuel supply chains
    Appl. Energy (IF 7.182) Pub Date : 2017-08-31
    Rex T.L. Ng, Christos T. Maravelias
    更新日期:2017-09-04
  • Maximizing intermittency in 100% renewable and reliable power systems: A holistic approach applied to Reunion Island in 2030 ☆
    Appl. Energy (IF 7.182) Pub Date : 2017-08-30
    Nadia Maïzi, Vincent Mazauric, Edi Assoumou, Stéphanie Bouckaert, Vincent Krakowski, Xiang Li, Pengbo Wang

    Technical constraints related to power systems management may limit the high integration of variable renewable energy sources in the power mix. This issue is addressed for the Reunion Island, which aims to reach energy independence by 2030 using 100% 100 % renewables. To that end, a long-term power system analysis is proposed using a comprehensive and coherent approach based on a bottom-up TIMES model providing future production mixes according to different scenarios. A transient reliability indicator based on kinetic energy is proposed and endogenized within the model. In addition, a dedicated Kuramoto model describes the synchronism condition required for aggregating the kinetic energy embedded in the whole power system. For the case of Reunion island, this methodology draws the following conclusions: (i) to achieve the 100% 100 % renewables target, the capacity to invest in the energy sector is doubled, and the level of reliability decreases considerably; (ii) the loss of reliability induced by higher intermittency— typically 50% 50 % —in the power mix can be counter balanced and leveraged by implementing flexibility solutions (demand response and storage).

    更新日期:2017-08-31
  • The potential impact of Brexit on the energy, water and food nexus in the UK: A fuzzy cognitive mapping approach
    Appl. Energy (IF 7.182) Pub Date : 2017-08-30
    Guy Ziv, Elizabeth Watson, Dylan Young, David C. Howard, Shaun T. Larcom, Andrew J. Tanentzap

    Energy is one of the cornerstones essential for human life, along with other services such as water and food. Understanding how the different services in the energy-water-food (EWF) nexus interact and are perceived by different actors is key to achieving sustainability. In this paper, we derive a model of the EWF nexus using fuzzy cognitive mapping (FCM). Data were collected in a two-step approach from workshops with researchers and stakeholders involved in the three focal sectors. Four FCMs were developed; one for each of the EWF sectors, and one for the interactions that create the nexus between EWF. The FCM represents the combined views of the groups who participated in the workshops, the importance and limitations of which is discussed. To demonstrate its effectiveness, the aggregated FCM was applied to predict the impacts on the EWF nexus of four scenarios under which the United Kingdom would depart from the European Union (i.e. Brexit). The FCM indicated that energy-related concepts had the largest influence on the EWF nexus and that EWF demand will decrease most under a ‘hard-Brexit’ scenario. The demand for energy was shown to decline relatively less than other services and was strongly associated with gross domestic product (GDP), whereas UK population size had a stronger effect on water and food demand. Overall, we found a threefold change across all concepts in scenarios without freedom of movement, contribution to the EU budget, and increased policy devolution to the UK.

    更新日期:2017-08-31
Some contents have been Reproduced with permission of the American Chemical Society.
Some contents have been Reproduced by permission of The Royal Society of Chemistry.
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