Journal Sciences News
Ultrasonics
15 May 2018
Controlling district heating and cooling networks to unlock flexibility: A review
Publication date: 15 May 2018
Source:Energy, Volume 151 Author(s): Annelies Vandermeulen, Bram van der Heijde, Lieve Helsen Flexibility in district heating and cooling systems (thermal networks in general) is an important means to cope with the intermittent generation of heat and electricity as the share of renewable energy sources (RES) increases. An important source of flexibility is the thermal energy storage present in district heating and cooling networks, found in the thermal inertia of buildings, storage units and the network itself. To unlock this flexibility and to use it effectively and efficiently, a suitable control strategy is required. In this context, this paper presents a possible definition of flexibility and its sources in a thermal network. It reviews techniques to quantify flexibility and shows the need for a more advanced control strategy; moreover, it discusses the challenges involved in developing such a control strategy. Also, the literature on advanced control in thermal networks is reviewed, by making a distinction between central, distributed and hybrid control. Finally, possible future research topics are identified based on the findings.
15 May 2018
Reverse electrodialysis: Modelling and performance analysis based on multi-objective optimization
Publication date: 15 May 2018
Source:Energy, Volume 151 Author(s): Rui Long, Baode Li, Zhichun Liu, Wei Liu In this paper, we proposed a refined model to describe the RED process by considering the variation of flow rates along the flow direction, and the concentration depended density and viscosity. The model was verified by good accordance between the calculated and experimental measured data. For evaluating the performance of a RED stack for some special applications, the net power density and the energy efficiency are two main criteria. However, they could not achieve their maximum values simultaneously. To achieve such a compromise, an optimization based on Non-dominated Sorting Genetic Algorithm II (NSGA-II) was conducted. Besides, the net power output and energy efficiency under single-objective optimization methods were calculated and compared. Results revealed that compared to the results under the maximum net power density, the net power density under the multi-objective optimization is slightly less than the maximum one, meanwhile the energy efficiency was much greater. The performance under the multi-objective optimization exhibited no obvious disadvantage against that under the maximum energy efficiency, considering the significant increase of the net power density.
15 May 2018
Energy cost analysis of an intelligent building network adopting heat trading concept in a district heating model
Publication date: 15 May 2018
Source:Energy, Volume 151 Author(s): Jonghoon Ahn, Dae Hun Chung, Soolyeon Cho With the help of advanced technologies, district heating systems were gradually improved to increase fuel use efficiency and reduce environmental impacts. Several control strategies focused on the performance improvement of energy generation or distribution in the network. However, most strategies overlooked zone-scaled thermal comfort related to occupant characteristics, and there was lack of studies combined with heat trading concepts. This research presents energy cost analysis of an intelligent network model and heat trading to mitigate increases of energy use and thermal dissatisfaction in a district model. Advanced thermal control algorithms provide optimized supply air conditions responding to occupant characteristics in different buildings. A distribution model contributes to the reduction of energy consumption, and heat trading effects are analyzed to maximize energy cost savings in a district model. In comparison with a conventional model, an intelligent controller improves thermal comfort by about 16.2% for a clinic, 2.4% for an office, and 7.1% for a residential building, respectively. Also, a distribution model with heat trading concept saves total energy costs by about 24.7%, theoretically. In conclusion, the model has advantages that it properly responds to occupant characteristics to mitigate thermal dissatisfaction, and it has a great potential to reduce total energy costs.
15 May 2018
Pressure characteristics during vented explosion of ethylene-air mixtures in a square vessel
Publication date: 15 May 2018
Source:Energy, Volume 151 Author(s): Yong Cao, Bin Li, Kanghua Gao The vented explosion in a 2
15 May 2018
Comparison study of indoor/outdoor experiments of a photovoltaic thermal PV/T system containing SiC nanofluid as a coolant
Publication date: 15 May 2018
Source:Energy, Volume 151 Author(s): Ali H.A. Al-Waeli, Miqdam T. Chaichan, Hussein A. Kazem, K. Sopian, Adnan Ibrahim, Sohif Mat, Mohd Hafidz Ruslan Solar energy technology has been evolving for the better part of the last decade. Worldwide innovation and support have created an alternative energy source that is helping to battle climate change. Photovoltaic thermal (PV/T) converters use various working fluids. Silicon carbide (SiC) nanofluid is employed in this study in the cooling application of a PV/T system. The aim of this study is to assess and evaluate the performance of PV/T collectors when running a SiC nanoparticle dispersed in water as the base fluid for both indoor and outdoor systems. The performance assessment includes thermal, electrical and combined PV/T efficiencies. Indoor and outdoor experimentation is done to accurately assess the performance enhancement hypothesized by the authors. Furthermore, a comparison is made between the indoor and outdoor results to validate each experiment and draw conclusions. The indoor system results were close to the outdoor experiment, suggesting a performance enhancement with an incremental efficiency rise.
15 May 2018
Influence of exhaust heat distribution on the performance of dual-loop organic Rankine Cycles (DORC) for engine waste heat recovery
Publication date: 15 May 2018
Source:Energy, Volume 151 Author(s): Haozhong Huang, Juan Zhu, Wei Deng, Tiancheng Ouyang, Bo Yan, Xu Yang In this paper, two Dual-loop Organic Rankine Cycles (DORC) were used to recycle the waste heat from both engine exhaust and coolant. The two cycles were defined as S1 and S2, respectively. Both cycles have a high-temperature loop and low-temperature loop. In S1, both high-temperature and low-temperature loops recycled the waste heat from engine exhaust, while in S2, only the high-temperature loop recycled the waste heat. Water, methanol, toluene, R245fa, and pentane were the candidate working fluids of the high-temperature loop, while R143a was the working fluid in the low-temperature loop. The influence of exhaust heat distribution on the performance of dual-loop organic Rankine cycles(DORC) for engine waste heat recovery was studied in this paper. Net output power, exergy efficiency, sum of products of heat transfer coefficient and heat transfer surface area of the heat exchanger (UA), and unit electricity production cost of the system (EPC) were selected as the objective functions. The results show that the lower the proportion of waste heat from the exhaust distributed to low-temperature loop, the better the system performance. When the waste heat from exhaust was completely recycled by high-temperature loop, the system performance reached its best, namely, S2 performed the best. Methanol-based S2 cycle performed the best and the net output power, exergy efficiency, UA, and EPC were 117.46
15 May 2018
Techno- Economic evaluation of milk chilling unit retrofitted with hybrid renewable energy system in coastal province
Publication date: 15 May 2018
Source:Energy, Volume 151 Author(s): M. Edwin, S. Joseph Sekhar Renewable energy based hybrid energy cooling system is an economic and convenient option for rural milk preservation in remote coastal province in southern part of India. In this work, a model is presented for the techno-economic evaluation of hybrid renewable energy operated chilling system to fulfil the preservation requirements of isolated coastal sites where the bio resources and solar energy are plenty available. A milk chilling plant operated by vapour absorption cooling system which obtains thermal energy from various combinations of existing renewable energy sources has been studied and to predict the effect of different energy proportions of existing renewable energy resources on the overall system performance and economical parameters. From the analysis, it can be concluded that the Gobar gas/Biomass/Biogas/Solar (0.5:0.25:0.125:0.125) has been recommended for the suitable combination. The analysis reveals that the proposed hybrid renewable energy based chilling system can show the overall system performance as 0.18–0.19 with lowest Payback period (4 years 6 months to 5 years 3 months), life cycle cost (INR 16.8–19.5 million) and positive net present value. The sensitivity analysis show that the energy conversion efficiency and interest rate significantly influences the overall COP and capital cost, running cost and payback period.
15 May 2018
Optimization analysis of structure parameters of steam ejector based on CFD and orthogonal test
Publication date: 15 May 2018
Source:Energy, Volume 151 Author(s): Yifei Wu, Hongxia Zhao, Cunquan Zhang, Lei Wang, Jitian Han One-dimensional theoretical methods are always utilized for analysis of performances of a steam ejector but they commonly have certain limitations. Numerical simulation and analysis were carried out by means of CFD method to the flow field inside a steam ejector for recovery of waste heat; moreover, the single-factor analysis was performed to see how the ejector was affected by those single-factors such as the diameter of the nozzle outlet, the distance between the nozzle outlet to the inlet of the mixing chamber and diameters of the contraction section of the mixing chamber and the diffuser chamber, respectively, while other conditions are fixed. Multi-factor analysis was then carried out to investigate the performances of the ejector and its structures were optimized by means of the five-factor and four-level orthogonal tests to gain the sensitivity for each factor to performances of the ejector. Results indicate that the optimized ejector has much better performances and the diameter of the nozzle outlet is the most sensitively influencing factor on performances of the ejector. This study may provide a new way of thinking for optimization of structure parameters of any steam ejector and have certain values for design and application of steam ejectors.
15 May 2018
Multi-layer perception based model predictive control for the thermal power of nuclear superheated-steam supply systems
Publication date: 15 May 2018
Source:Energy, Volume 151 Author(s): Zhe Dong, Zuoyi Zhang, Yujie Dong, Xiaojin Huang Nuclear superheated-steam supply systems (Su-NSSS) produces superheated steam flow for electricity generation or process heat. Although the current Su-NSSS control law can guarantee satisfactory closed-loop stability, which regulates the neutron flux, primary coolant temperature and live steam temperature by adjusting the control rod speed as well as primary and secondary flowrates, however, the control performance needs to be further optimized. Motivated by the necessity of optimizing the thermal power response, a novel multi-layer perception (MLP) based model predictive control (MPC) is proposed in this paper, which is constituted by a MLP-based prediction model and the control input designed along the direction opposite to the gradient of a given performance index. It is proved theoretically that this MLP-based MPC guarantees globally-bounded closed-loop stability. Finally, this newly-built MLP-based MPC is applied to the thermal power control of a Su-NSSS, whose implementation is given by forming a cascaded feedback control loop with the currently existing Su-NSSS power-level control in the inner loop for stabilization and with this new MPC in the outer loop for optimization. Numerical simulation results verify the correctness of theoretical result, and show the satisfactory improvement in optimizing the thermal power response.
15 May 2018
Ammonia production from black liquor gasification and co-gasification with pulp and waste sludges: A techno-economic assessment
Publication date: 15 May 2018
Source:Energy, Volume 151 Author(s): Maryam Akbari, Adetoyese Olajire Oyedun, Amit Kumar The economic feasibility of producing ammonia through the gasification of three different feedstocks produced in pulp and paper mills is investigated in this paper. The first case uses black liquor, the main by-product of the kraft pulping process, as the feedstock, and in the other two cases pulp sludge (PS) and waste sludge (WS) are co-gasified with black liquor. For all three cases, a process model in which mass and energy balances were calculated was developed. The model results were used to estimate the equipment size and estimate costs. Techno-economic models were developed and ammonia production costs were calculated. A case study for Alberta, a western Canadian province, was conducted. The results indicated that for a 10% discount rate (or internal rate of return [IRR]), ammonia production in all three cases is cost competitive with current ammonia prices. The cost of production (COP) of ammonia for all three cases ranges from 743 to 748 \$/t. Sensitivity and uncertainty analyses were conducted on the estimated COP, and the results show that the COP is the most sensitive to the capital cost, discount rate, electricity price and plant lifetime.
15 May 2018
A practical model for energy dispatch in cogeneration plants
Publication date: 15 May 2018
Source:Energy, Volume 151 Author(s): Maria Izabel Santos, Wadaed Uturbey This paper focuses on the development of a dispatch model for cogeneration systems in industrial plants. The proposed model schedules thermal and electrical outputs of the cogeneration units by minimizing total operating costs in the plant while satisfying operational constraints. The work presents a practical model that depends on easily available data in the industrial environment, i.e., efficiency data available from equipment manufacturers or machine tests. The power to heat ratio is modeled using equipment efficiency data that depends on the cogeneration unit output. This approach allows to represent feasibility regions and supplementary firings without complex thermodynamic relations that require additional data. In order to illustrate the application of the model in real systems, a potassium production plant in Brazil is studied. This case study involves two cogeneration units with supplementary firings and a boiler. Results indicate that the model allows obtaining a dispatch strategy with reduced operating costs when compared with the traditional planning used by plant operators. Three scenarios are simulated and cost savings obtained with the optimized strategy vary between 2.0% and 4.0%, when compared with the corresponding unplanned strategy.
15 May 2018
Analysis of Road Curvature’s Effects on Electric Motorcycle Energy Consumption
Publication date: 15 May 2018
Source:Energy, Volume 151 Author(s): Alireza Farzaneh, Ebrahim Farjah Concerns over carbon emissions have motivated motorcycle producers to explore the use of electric energy instead of gasoline. Due to battery capacity limitations, electric energy consumption should be optimized to extend the range of Electric Motorcycles (EMCs). Road curvature is an inevitable part of motorcycle travel, and this paper proposes a detailed electric motorcycle model to calculate electric energy consumption on both straight curved roads. Simulation results show that road curvature has a significant effect on energy consumption, so a Dynamic Programming (DP) optimization strategy was used to calculate EMC optimized speed over curved roads.
15 May 2018
Growth of industrial CO2 emissions in Shanghai city: Evidence from a dynamic vector autoregression analysis
Publication date: 15 May 2018
Source:Energy, Volume 151 Author(s): Boqiang Lin, Bin Xu Carbon dioxide (CO2) is one of the main sources of global warming, rising sea levels, and frequent outbreaks of extreme weather. China is now one of the largest energy consumer and CO2 emitters in the world. As one of China's economic centers, Shanghai city has a perfect industrial system with large industrial scale. The industrial sector is an energy– and emission–intensive industry, which contributes the significant part of CO2 emissions in Shanghai city. Therefore, an in–depth investigation of the main driving forces of CO2 emissions in the industrial sector is essential to reduce CO2 emissions in the city. This study uses Vector Autoregressive model to analyze the main factors causing the increase in CO2 emissions in the industrial sector. The results show that economic growth leads to an increase in CO2 emissions in the short run, but is conducive to reducing CO2 emissions in the long run, due to the differences in fixed–asset investment and export trade. Energy consumption structure leads to a growing CO2 emissions in the short term, and is beneficial to mitigate CO2 emissions in the long term, owing to the gradual optimization of energy consumption structure. However, urbanization helps to reduce CO2 emissions in the short term, but leads to an increase in CO2 emissions in the long term, because of urban real estate and infrastructure construction investments as well as vehicle use. Energy efficiency leads to an increase in CO2 emissions both in the short and long run since the scale effect exceeds the technical effect. Industrial structure produces a positive effect in the short run, but the impact is gradually narrowing in the long run.
15 May 2018
Improved harmony search algorithm for electrical distribution network expansion planning in the presence of distributed generators
Publication date: 15 May 2018
Source:Energy, Volume 151 Author(s): Abdollah Rastgou, Jamal Moshtagh, Salah Bahramara Distribution network expansion planning problem is carried out to supply the forecasted demand of distribution network in a certain time in which optimal size and location of distribution substations and feeders should be determined. In this paper, this problem in the presence of different types of distributed generators is addressed. For this purpose, a new approach is applied to model several practical aspects such as pollution, investment and operation costs of distributed generators, purchased power form the main grid, dynamic planning, and uncertainties of load demand and electricity prices. The uncertainties are modeled using the probability distribution function and Monte-Carlo simulation is applied to insert them into the planning problem. Because the problem involves many variables and constraints and is a non-convex and large-scale one, improved harmony search algorithm is used to solve it. To show the effectiveness of the proposed model and solving approach, it is applied to the 9-node and 69-node standard radial distribution networks and a real system of western part of Iranian national 20
15 May 2018
Managerial flexibility in levelized cost measures: A framework for incorporating uncertainty in energy investment decisions
Publication date: 15 May 2018
Source:Energy, Volume 151 Author(s): John E. Bistline, Stephen D. Comello, Anshuman Sahoo Many irreversible long-run capital investments entail opportunities for managers to respond flexibly to changes in the economic environment. However, common levelized cost measures used to guide decision-making, such as the levelized cost of electricity, implicitly assume that the values of random economic variables are known with certainty when investment decisions are made. This assumption implies, often incorrectly, that managerial flexibility carries zero value. This paper improves levelized cost measures by deriving an expansion that accounts for both uncertainties in relevant variables and the value of managerial flexibility in responding to them. This method is applied to quantify the value of flexibility in two example decision problems. In one, an operator of a natural gas electricity generation facility evaluates whether to invest in carbon capture capabilities. Another considers retirement decisions for U.S. nuclear plants. These examples illustrate that simplified cost metrics can inaccurately guide decision-making by inflating cost estimates relative to the proposed levelized cost measure that accounts for uncertainty and flexibility.
15 May 2018
Improved harmony search algorithm for the solution of non-linear non-convex short-term hydrothermal scheduling
Publication date: 15 May 2018
Source:Energy, Volume 151 Author(s): Morteza Nazari-Heris, Amir Fakhim Babaei, Behnam Mohammadi-Ivatloo, Somayeh Asadi The short-term hydrothermal scheduling (SHTS) problem is defined as one of the most important and challenging scheduling problems, which aims to obtain the minimum cost of electrical energy production. Considering an insignificant generation cost of hydropower systems, the objective of STHS is to minimize the operation cost of thermal generation plants. The optimal generation scheduling of hydro and thermal units is a complex non-convex optimization problem taking into account a set of equality and inequality constraints. The challenging constraints of the STHS problem are valve-point loading effect of thermal units, power transmission loss of the system, generation capacity of thermal and hydro units, and load balance. In this paper, an improved harmony search (IHS) optimization algorithm is employed on the non-linear non-convex STHS problem. The proposed method is employed on two test systems in order to evaluate the performance of the applied optimization method on the STHS problem. The simulation results are provided and compared with those reported in recent publications, which proves the effectiveness of the proposed IHS method in the solution of the STHS problem.
15 May 2018
Forecasting the output of shale gas in China using an unbiased grey model and weakening buffer operator
Publication date: 15 May 2018
Source:Energy, Volume 151 Author(s): Bo Zeng, Huiming Duan, Yun Bai, Wei Meng China has the richest shale gas resources worldwide. However, the exploitation of shale gas in China is very recent, and historical data on the output of shale gas are extremely limited (only five data points exist). Consequently, common mathematical models designed for use with big data cannot be used to forecast the shale gas output in China. Grey models can be constructed by using small samples; however, traditional grey models have the drawback of 'misplaced replacement' during the conversion from a difference equation to a differential equation. Thus, a new unbiased grey prediction model called UGM(1,1) is proposed and optimised in this study. A grey weakening buffer operator was employed to pre-process the primary data on Chinese shale gas output to eliminate the contradiction between the prediction results of models and the conclusions of qualitative analysis. The UGM(1,1) model was then used to simulate the output of shale gas in China, and found to outperform other grey models. Finally, we forecasted the output of shale gas in China from 2017 to 2025, and analysed the rationality of the prediction data. The study findings will be of important reference value for use by the Chinese government to formulate energy policies.
15 May 2018
A novel energy harvesting device for ultralow frequency excitation
Publication date: 15 May 2018
Source:Energy, Volume 151 Author(s): Feng Wang, Xiuting Sun, Jian Xu In recent decades, energy harvesting from external vibration with ultralow frequency has been investigated intensively. A novel energy harvesting device with adjustable nonlinearity for ultralow frequency excitation is proposed and analyzed in this study. The energy harvesting device is made of a mass attached to the base by Elastic Steel Slices (ESSs) and a pair of Quadrilateral-Linkage Structures (QLSs). With the mathematical model, theoretical studies are carried out. The analysis shows that the device is capable for ultralow-frequency vibration energy harvesting since it has adjustable resonance frequency band. With the appearance of the adjustable nonlinearity, the system has a wide band for resonance by the utilization of multi-steady states. Experimental prototypes are assembled and tested. The experimental results show that the beginning frequency of effective energy harvesting can be reduced by over 50% by assembling the QLSs to adjust the stiffness property of the system. In addition, although the stiffness of the device is expressed by nonlinear irrational function, we find that the output voltages generated are large, smooth and stable. The results of this study illustrate that the proposed device is a feasible design for collecting energy from ultralow frequency excitation.
15 May 2018
Wind field reconstruction using dimension-reduction of CFD data with experimental validation
Publication date: 15 May 2018
Source:Energy, Volume 151 Author(s): Li Qin, Shi Liu, Teng Long, Muhammad Ali Shahzad, H. Inaki Schlaberg, Song An Yan Short-term wind forecasting is important in updating wind electricity trading strategies, facility protection and more effective operation control. Physical based models, particularly those using computational fluid dynamics (CFD), are able to provide ever more detailed wind speed data. However, such methods involve handling a huge amount of CFD data, which is prohibitively time consuming for a short-term wind forecast in real situations. To solve this problem, Singular Value Decomposition (SVD) and Principal Component Analysis (PCA) algorithms are applied in this study to reduce the dimensions of wind speed data and the proposed method is applied to reconstruct the wind field. Wind fields have successfully been reconstructed with good accuracy for the wind direction angles ranging from 0° to 90°. This method is validated by experimental data from a wind tunnel experiment. The accuracy of the proposed reconstruction algorithm increases with the sampling rate of the measurement and the locations of the sensors do not significantly affect the accuracy of the results. Gaussian noise introduced into the input signal does not significantly deteriorate the reconstruction quality. Results show that the proposed method can adequately be used to reconstruct the wind field for the models tested with a high degree of confidence.
15 May 2018
Nuclear power supply: Going against the misconceptions. Evidence of nuclear flexibility from the French experience
Publication date: 15 May 2018
Source:Energy, Volume 151 Author(s): C. Cany, C. Mansilla, G. Mathonni
15 May 2018
Integrated tech-paradigm based innovative approach towards ecological coal mining
Publication date: 15 May 2018
Source:Energy, Volume 151 Author(s): Jiuping Xu, Wen Gao, Heping Xie, Jingqi Dai, Chengwei Lv, Meihui Li Coal mining technology directly affects coal production quantity and quality, which in turn affects global energy supplies, especially in rapidly urbanizing, industrializing economies. In this research, a coal production technological diffusion mathematical model is proposed, the results from which indicated that while total coal production is expected to decline in the following decades, coal will continue to provide a sizable share of global prime energy to meet the expected energy demands. A general data analysis was conducted to fully understand coal mining technological paradigmatic development and future necessary improvements to ensure more efficient, environmentally-friendly coal production. It was found that the coal mining technological paradigm followed a three-stage trajectory; competition, diffusion, and shift; in accordance with the traditional technological paradigm S-curve, and underground coal gasification (UCG) related technologies were identified as the main development direction for coal mining technologies. An integrated energy exploitation approach for ecological coal mining was then designed to deal with current environmental and energy returns on investment problems, to improve performance, and to act as a foundation for future UCG technological developments. Some policy recommendations are given to guide the implementation of the proposed ecologically oriented integrated coal mining system.
15 May 2018
Impact of time expenditure on household preferences for cooking fuels
Publication date: 15 May 2018
Source:Energy, Volume 151 Author(s): Karabee Das, Moonmoon Hiloidhari, D.C. Baruah, Sanderine Nonhebel Access to energy for cooking is one of the major challenges that rural India faces. Most of the rural households of North-Eastern India rely heavily upon fuelwood and traditional open-fire cookstoves for cooking activities. And everyday collection of fuelwood is time-consuming. Hence, women often gather fuelwood to make charcoal. While the use of charcoal has some advantages, it is not clear whether the investment of time in making charcoal is worthwhile. In this paper, we compare household time investments for fuelwood and charcoal production. The study is done using survey data on Napaam village situated in Sonitpur District of Assam, Northeast India. We developed a model to analyse fuelwood needed and time spent upon the introduction of improved cookstoves and/or charcoal production. This analysis reveals that improved cookstoves using fuelwood results in the least time expenditure on the production of cooking fuel. Whilst introducing charcoal marginally reduces the amount of fuelwood, but increases time spent on cooking, due to the time required to produce the charcoal. Hence, rural households who make their own charcoal spend more time on producing cooking fuel than those households relying on direct use of fuelwood.
15 May 2018
Analysis of oil-free linear compressor operated at high pressure ratios for household refrigeration
Publication date: 15 May 2018
Source:Energy, Volume 151 Author(s): Kun Liang Compared with conventional reciprocating compressor for vapour compression refrigeration (VCR) system, linear compressor offers higher energy efficiency and oil-free operation, which allows the use of mini/micro-channel heat exchangers. However, there are key challenges when oil-free linear compressors are used for household refrigeration with typical high pressure ratios (above 10), such as high clearance loss, high piston offset, and very non-linear gas spring. Previous papers by the author have demonstrated the feasibility of oil-free linear compressor for electronics cooling at lower pressure ratios (below 3.5). This paper presented comprehensive analysis of these issues as a key step towards developing oil-free linear compressor for household refrigeration. The model of non-linear gas spring at high pressure ratios is validated by measurements of a previous prototype linear compressor with minimum flow. Piston offset can be effectively controlled by solenoid valve at 1
15 May 2018
Planning for variable renewable energy and electric vehicle integration under varying degrees of decentralization: A case study in Lusaka, Zambia
Publication date: 15 May 2018
Source:Energy, Volume 151 Author(s): Madeleine McPherson, Malik Ismail, Daniel Hoornweg, Murray Metcalfe High urbanization rates, decentralized solar photovoltaic growth, and transportation electrification are changing the electricity planning landscape across Sub-Saharan Africa. This paper explores the operational implications of variable renewable energy and electric vehicle integration at the city scale. A production cost dispatch model is applied to Lusaka, Zambia's capital, whose largely hydro-based electricity system is currently facing shortfalls due to population and economic growth and climate change. The results demonstrate that variable renewable energy penetration and decentralization are important levers for managing greenhouse gas emissions, while the choice of electric vehicle charging policy has significant cost implications. Due to Zambia's flexible hydro assets and potential pumped hydro storage capacity, large penetrations of centralized solar photovoltaic energy can be integrated with low curtailment rates, regardless of electric vehicle charging policy. The high curtailment rates (>10%) and increased greenhouse gas emissions associated with non-export solar PV penetrations greater than 35% can be mitigated with flexible loads, such as electric vehicle charging, that is strategically shifted to coincide with high-resource periods of the day. Without active electric vehicle charging management, large peaking capacity is required to satisfy demand spikes. Conversely, system-optimized vehicle-to-grid charging eliminates the need for additional storage infrastructure thereby mitigating system costs.
15 May 2018
Innovative hybrid models for forecasting time series applied in wind generation based on the combination of time series models with artificial neural networks
Publication date: 15 May 2018
Source:Energy, Volume 151 Author(s): Henrique do Nascimento Camelo, Paulo S
15 May 2018
Development of a new flux density function for a focusing heliostat
Publication date: 15 May 2018
Source:Energy, Volume 151 Author(s): Weidong Huang, Liang Yu It is important to calculate solar flux distribution with a precise and simple method for the design and optimization of solar tower systems. In this paper, the Gaussian flux density function at the image plane is deduced after simulating the image function of the heliostat with Gaussian distribution function. The flux density distribution of various round or rectangular focusing heliostats at the receiver plane can be calculated through projection. The simulation results are compared with SolTrace analysis and experimental data. Comparison of the flux density distributions between this method and SolTrace show excellent agreement especially when the optical error is equivalent to or larger than the Gaussian function parameter of heliostat image which fits to most of heliostats in a solar tower system. Although it increases error to simulate the image of the heliostat with elliptical Gaussian distribution, compared with the experimental data, the average prediction error of the elliptical Gaussian function is 2.24%, which is less than that of SolTrace because SolTrace applies the circular Gaussian distribution for optical error which bring more errors. Therefore, the Gaussian flux density function proposed is validated and can be used to simulate and optimize the design of solar heliostats field.
15 May 2018
Thermodynamic optimization of heat transfer process in thermal systems using CO2 as the working fluid based on temperature glide matching
Publication date: 15 May 2018
Source:Energy, Volume 151 Author(s): Fuzhen Zhang, Yinhai Zhu, Conghui Li, Peixue Jiang For thermal systems using CO2 as a working fluid, an isobaric heat transfer in the supercritical region is a variable temperature process. When CO2 is near the pseudo-critical point, its specific heat changes clearly with temperature, which results in an increase in the average temperature difference and thus, an increase in entropy generation. A thermodynamic optimization method for a heat transfer process based on temperature glide matching is proposed in this paper. This method can allow the temperature difference to be uniform and near the minimum value. The heat transfer process in the gas cooler of a CO2 heat pump water heater and the recuperator of the supercritical CO2 (S-CO2) Brayton cycle are optimized based on this method. Using this concept, a CO2 heat pump water heater can simultaneously obtain a certain amount of warm water without simultaneously reducing the hot water output; in addition, for S-CO2 cycle, the exergy efficiency of the regenerator is improved, and the thermal efficiency of the system is thereby improved.
15 May 2018
Energy, economic and environmental (3E) analysis and multi-objective optimization of a spray-assisted low-temperature desalination system
Publication date: 15 May 2018
Source:Energy, Volume 151 Author(s): Q. Chen, M. Kum Ja, Y. Li, K.J. Chua Energetic, environmental and economic (3E) performances are major effective criteria that one needs to consider when designing and optimizing a desalination plant. In order to optimize all the three variables, it is important to determine an optimal system configuration and operation strategy at early design stages. Therefore, 3E analyses and multi-objective optimization of desalination systems are the areas of significant research interests. This paper specially conducts a 3E analysis and multi-objective optimization exercise of a spray-assisted low-temperature desalination technology through a judiciously developed mathematical model. Several optimization scenarios are studied to emphasize different performance variables. A multi-objective optimization is also performed to obtain the best trade-offs among these variables. Results revealed that the specific energy consumption highly conflicts with the initial investment, while the specific CO2 emission and the initial investment present a positive correlation. The specific CO2 emission can be minimized through the use of upward spray condensers, while the initial cost can be reduced by designing more compact spray evaporators and using cheaper materials.
15 May 2018
Exchange rate fluctuations, oil price shocks and economic growth in a small net-importing economy
Publication date: 15 May 2018
Source:Energy, Volume 151 Author(s): Presley K. Wesseh, Boqiang Lin Policy makers often rely on theoretical wisdom and tend to allocate huge resources towards hedging strategies against oil price and exchange rate movements without considering to first test these theories on a context basis. To overcome this limitation, we model both upward and downward movements in oil prices and exchange rates in order to study the oil – exchange rate – growth nexus for a small net-importing country like Liberia. We estimate an unrestricted VAR model and document the following results: First, a rise in the price of oil appears to stimulate Liberian GDP. Second, depreciation in the value of the Liberian dollar causes real GDP to fall while appreciation of the Liberian dollar tends to have no impact on real GDP in Liberia. Third, trade balance has a positive correlation with growth of the Liberian economy. Finally, consumer prices are found to also correlate positively with economic growth in Liberia. Contrary to bulk of the literature, this paper provides general insights that a rise in oil price is sometimes good for net-oil importers.
15 May 2018
Analysis of operating diagram for H2/Air rotating detonation combustors under lean fuel condition
Publication date: 15 May 2018
Source:Energy, Volume 151 Author(s): Qiaofeng Xie, Haocheng Wen, Weihong Li, Zifei Ji, Bing Wang, Piotr Wolanski Experiments are performed to investigate the combustion characterization and operating diagram under the lean fuel condition in a laboratory-scale H2/air rotating detonation combustor (RDC). Pressure signals are obtained at different circumferential and axial positions on the RDC. Equivalence ratios ranging from 0.6 to 1.0 and air mass flow rates ranging from 25 to 225
15 May 2018
Forecasting China's total energy demand and its structure using ADL-MIDAS model
Publication date: 15 May 2018
Source:Energy, Volume 151 Author(s): Yongda He, Boqiang Lin Forecasting total energy demand and its structure is the basis for energy planning and industrial policy formulation. However, existing research on the forecast of energy structure remains inadequate. This study aims at constructing an ADL–MIDAS model to identify the optimal model to forecast China's energy demand and its structure, and offer a reasonable judgement on future carbon emission and energy scenarios in China and other developing countries. Thus, this study adopts mixed frequency data for quarterly GDP, quarterly added value, and annual energy demand of various industries to construct an ADL–MIDAS model. Then, the optimal model to forecast China's energy demand is selected from various model combinations that employ different weight functions and forecasting methods. The model forecasts China's total energy demand and its structure as proposed in the 13th Five Year Plan. The in-sample prediction results show that, in the optimal model, the smallest prediction error is 0.02%, while the largest of the four future periods is 2%, indicating that the ADL–MIDAS model is effective in forecasting energy demand. Further, the forecast results suggest that, by 2020, China's total energy demand will reach approximately 4.65 billion tonnes of standard coal equivalent; the demand for coal, natural gas, and non-fossil fuel will be 57%, 7.6%, and 18%, respectively, contingent on economic growth conditions. Given these forecast results, the energy planning targets set under the 13th Five Year Plan are attainable. However, in the case of natural gas demand, considerable marketing is required to promote its use.
15 May 2018
A theoretical benchmark for bypass controllers in a residential district heating network
Publication date: 15 May 2018
Source:Energy, Volume 151 Author(s): Annelies Vandermeulen, Bram van der Heijde, Dieter Patteeuw, Dirk Vanhoudt, Lieve Helsen Bypass valves in district heating substations are a compromise between efficiency and quality of service. On the one hand, they are required to ensure that each building (no matter the distance to the heat source) has warm water within an acceptable time. On the other hand, they form a short-circuit between the warm supply and cold return line and their use can increase the return temperature substantially. Therefore, a good control of these bypass valves is critical to limit the drawback of their use. In this context, this paper compares two commonly used control strategies (manual control and thermostat control) to a new theoretical benchmark that provides an upper boundary for the performance of bypass controllers. This theoretical benchmark ensures a just-in-time delivery of warm water by taking into account time delays in the network. In a simulation case study of a small neighbourhood in Genk, Belgium, the benchmark shows that substantial improvement regarding bypass control is possible.
15 May 2018
Implications of diversification strategies in the European natural gas market for the German energy system
Publication date: 15 May 2018
Source:Energy, Volume 151 Author(s): Philipp Hauser, Heidi U. Heinrichs, Bastian Gillessen, Theresa M
15 May 2018
Synthesis of recent Swedish district heating research
Publication date: 15 May 2018
Source:Energy, Volume 151 Author(s): Kerstin Sernhed, Kristina Lygnerud, Sven Werner In Sweden, district heating meets currently above half of the heat demands in buildings. District heating research in Sweden has a long tradition dating back to 1975. The latest research program period included 34 projects and was executed between 2013 and 2017. In this paper, a synthesis is performed on the Swedish research frontier by assessing these recent research projects. The three study purposes was to provide an overview over the executed projects, to identify new research questions, and to identify future challenges to the Swedish district heating industry. The assessment was based on six defined key areas, such as demand, resources, system frameworks, technology, cold supply, and international perspective. The subsequent content analysis was performed from three perspectives: the perspective of energy system transition, the customer perspective, and the sustainability perspective. Final conclusions include the three future challenges for the Swedish district heating industry. These are future strategies to communicate the value of district heating, vision for district heating beyond the transition to fossil free supply, and technology development for efficient use of low temperature heat sources.
15 May 2018
Long-term modelling and assessment of the energy-economy decoupling in Spain
Publication date: 15 May 2018
Source:Energy, Volume 151 Author(s): Diego Garc
15 May 2018
Dynamic modeling of local district heating grids with prosumers: A case study for Norway
Publication date: 15 May 2018
Source:Energy, Volume 151 Author(s): Hanne Kauko, Karoline Husev
15 May 2018
Optimization of well spacing to achieve a stable combustion during the THAI process
Publication date: 15 May 2018
Source:Energy, Volume 151 Author(s): Renbao Zhao, Shuai Yu, Jie Yang, Minghao Heng, Chunhui Zhang, Yahong Wu, Jianhua Zhang, Xiang-an Yue Toe-to-Heel Air Injection (THAI) is a great potential in improving energy efficiency for heavy oil/bitumen recovery. A 3D cylindrical combustion model with large size is used to carry out several experiments using Xinjiang (China) crude oil. The evolution of the fire chamber, temperature variation rate, and mass of burned carbon were analyzed using temperature measurements and flue gas composition analysis. Coke zone was quantified in the variation of zone thickness and distribution characteristics. The results reveal that there is a prevailing stable propagation of the combustion front during the first one third of the process for varying injector to producer spacing. Oxygen breakthrough is more susceptible for smaller separations and the combustion zone is reduced in length. Larger combustion fronts with greater relative propagation in the horizontal direction occurs when the well spacing is larger. The distribution of coke is significantly influenced by the injector/producer spacing. For a THAI pattern with greater injector/producer spacing, a smaller inclination angle of the coke zone occurs and the likelihood of oxygen breakthrough to the horizontal production well is lessened. Hence, the injector to producer spacing needs to be considered in designing a safe THAI process for potentially larger efficiency and optimum economics.
15 May 2018
Construction of an innovative adsorbent bed configuration in the adsorption chiller - Selection criteria for effective sorbent-glue pair
Publication date: 15 May 2018
Source:Energy, Volume 151 Author(s): Karolina Grabowska, Jaroslaw Krzywanski, Wojciech Nowak, Marta Wesolowska Due to the progressive climate changes, increasing demand for cooling is observed. Therefore, ecological alternatives to conventional cooling systems based on electricity are analysed. One of the promising solutions are adsorption chillers which can be powered by low grade thermal energy sources such as waste heat, solar power and heat produced in cogeneration. However, contemporary adsorption chillers achieve lower COP (coefficient of performance) when compared to conventional electricity-driven compression refrigerators. Refrigeration capacity of the adsorption chiller is obtained with the use of thermal effects which occur during adsorption and desorption processes on porous media and the intensification of this phenomena is currently one of the most important research challenges. The paper presents development of guidelines to build novel coated construction of adsorption beds. The criterion for selection of optimum bed components in terms of improving COP of the adsorption chillers dedicated to air conditioning has been defined. Silica gel has been indicated as the most favorable sorbent for modification of the bed construction with glue.
15 May 2018
Asymptotic analysis of anode relative humidity effects on the fastest voltage decay single cell in a stack
Publication date: 15 May 2018
Source:Energy, Volume 151 Author(s): Yongfeng Liu, Na Wang, Pucheng Pei, Shengzhuo Yao, Fang Wang An anode relative humidity (ARH) model is set up to analyze the effects of anode relative humidity on the fastest voltage decay single cell in a stack. In the ARH model, the saturation pressure related to relative humidity is established by anode pressure drop instead of using conventional empirical equation in Fluent model. First, a three dimensional (3D) model incorporating geometry and grids is established. Second, experiment is conducted including a 10-cell stack, single cell distribution and test schematic. Third, both experiment and simulation results are discussed in detail. Furthermore, for the fastest voltage decay single cell, a comparable analysis among ARH model, Fluent model and experiment is carried out at the different anode relative humidities (55%, 70%, 85% and 100%). The results show that FC10 (the furthest distance single cell from gas inlet) voltage decay is the fastest in the stack. ARH model applied to FC10 voltage decay shows good agreement with Fluent model and experiment. ARH model accuracy increases by 47% compared to Fluent model. And the error between ARH model and experiment is reduced to 3% at 350
15 May 2018
Network-constrained optimal bidding strategy of a plug-in electric vehicle aggregator: A stochastic/robust game theoretic approach
Publication date: 15 May 2018
Source:Energy, Volume 151 Author(s): Saeed Zolfaghari Moghaddam, Tohid Akbari This paper presents a strategic bidding model for several price-taker plug-in electric vehicle aggregators sharing the same distribution network that participate in both day-ahead energy and ancillary services (up/down-regulation reserve) markets. Since the strategic feasible space of an aggregator depends on the actions of the other aggregators due to the limited capacity of the existing feeders, the proposed problem forms a generalized Nash equilibrium problem. The aggregators’ objective is considered to be the cost of purchased energy from the day-ahead and real-time market minus the revenue from the day-ahead regulation market. A hybrid stochastic/robust optimization model is employed to deal with different uncertainties an aggregator faces in the bidding strategy problem. These uncertainties include day-ahead energy prices, day-ahead up/down-regulation prices, and real-time energy prices. Day-ahead prices are modeled by different scenarios, while real-time prices are represented by the confidence bounds. Results of a case study are shown to demonstrate the applicability and tractability of the proposed model.
15 May 2018
Enhancement of performance monitoring of a coal-fired power plant via dynamic data reconciliation
Publication date: 15 May 2018
Source:Energy, Volume 151 Author(s): Sisi Guo, Pei Liu, Zheng Li Wide-range and frequent operation changes have become a common phenomenon with thermal power plants in the context of fast penetration of intermittent renewable power. Performance monitoring at transient states is more important to the safety and high efficiency of power plants. Data quality is essential for conducting dynamic performance monitoring, and dynamic data reconciliation (DDR) provides great potential to enhance quality of measured data at transient states. In this paper, a moving window based approach to dynamic data reconciliation is proposed for a real coal-fired power plant using high sampling operational data. Firstly, dynamic characteristics of the system are discussed, taking account of the equipment accumulation in DDR problems. Results of case studies indicate that the data accuracy of measured mass flow parameters are enhanced effectively after DDR, and better results are obtained with the increasing time window size. Comparison with steady state data reconciliation approach is also carried out to indicate the enhanced effect of the DDR approach for the performance monitoring of a real power plant.
15 May 2018
Risk assessment of industrial excess heat recovery in district heating systems
Publication date: 15 May 2018
Source:Energy, Volume 151 Author(s): Kristina Lygnerud, Sven Werner The recovery of industrial excess heat for use in district heating systems can be characterised by great political interest, high potential, low utilisation and often high profitability. These characteristics reveal that barriers are present for its greater utilisation. One identified barrier is the risk that industries with excess heat can terminate their activities, resulting in the loss of heat recovery. Excess heat recovery investments are therefore sometimes rejected, despite them being viable investments. The risk of termination of industrial activities has been assessed by a study of 107 excess heat recoveries in Sweden. The analysis verified that terminated industrial activities are one of two major explanations for terminated heat delivery. The other major reason is substitution by another heat supply. These two explanations correspond to approximately 6% of all annual average heat recoveries. The identified risk factors are small annual heat recovery and the use of heat pumps when low-temperature heat was recovered. The main conclusion is that a small proportion of industrial heat recovery has been lost in Sweden because of terminated industrial activities. The risk premium of losing industrial heat recovery for this specific reason should be considered to be lower than often presumed in feasibility studies.
15 May 2018
Renewable heating strategies and their consequences for storage and grid infrastructures comparing a smart grid to a smart energy systems approach
Publication date: 15 May 2018
Source:Energy, Volume 151 Author(s): Henrik Lund This paper compares different strategies to transform the heating sector into a future 100% renewable energy solution. It focuses on the consequences for infrastructures in terms of grids and storage across the electricity, gas and heating sectors. The hypothesis is that these consequences are rarely taken into proper consideration, even though the costs are significant and differ substantially between the alternative pathways. While the smart grid scenarios are based on electricity as an energy carrier, the “smart energy systems” approach is based on a cross-sectoral use of all grids. Using Denmark as a case, this paper shows how the current gas and district heating grids each have twice the capacity of the electricity distribution grid. Moreover, the existing gas and thermal storage capacities are substantially higher and the additional future capacities are more affordable than within the electricity sector. The conclusion is that the “smart grid” pathway requires a 2–4 times expansion of the electricity grid and significant investments in electricity storage capacities, while the “smart energy systems” pathway can be implemented with relatively few investments in affordable minor expansions of existing grids and storage capacities.
15 May 2018
Assessment of primary air on corn straw in a fixed bed combustion using Eulerian-Eulerian approach
Publication date: 15 May 2018
Source:Energy, Volume 151 Author(s): Xiaoxiao Meng, Rui Sun, Tamer M. Ismail, M. Abd El-Salam, Wei Zhou, Ruihan Zhang, Xiaohan Ren In this paper, mathematical modelling is conducted on the combustion of corn straw in a one-dimensional bench combustion test rig, and the effects of the primary air flow rate are assessed over a wide range. Due to complex solid combustion mechanisms and inadequate knowledge of the process, the development of such combustion system is limited. Numerical modelling of this combustion system has some advantages over experimental analysis, although the development of a complete model for this type of combustion system remains a challenge. Due to its characteristic properties, modelling of biomass combustion has to overcome many difficulties. One such problem is displaying the process of initiating the combustion in numerical modelling. This study finds that the volatile release and combustion of char increases, thus increasing the amount of primary air up to a critical point, where the starting time of ignition becomes shorter as the primary air flow rate increases. The peak concentration of NO decreases with the increase of primary air, whereas with the increase in the amount of air, there is a reduction in the release of SO2 as well as a reduction in CO emissions in the bed.
1 May 2018
Comparative scaling analysis of two different sized pilot-scale fluidized bed reactors operating with biomass substrates
Publication date: 15 May 2018
Source:Energy, Volume 151 Author(s): J. Cardoso, V. Silva, D. Eus
1 May 2018
Thermodynamic performance of cycle combined large temperature drop heat exchange process:Theoretical models and advanced process
Publication date: 1 May 2018
Source:Energy, Volume 150 Author(s): Chenghu Zhang, Yaping Li High-temperature-drop heat exchange technology, which can be realized by the proper configuration of heat-driven heat pump cycles, is an important solution for the Large-scale District Heating project. Cycle combined heat exchange process model is a theoretical standard for the analysis of High-temperature-drop heat exchange process, the thermodynamic performance and the heat-work conversion relationship of the this kind of process need to be researched to approach the theoretical optimal heat exchange effect. In this paper, with the analytical method, the thermodynamic performance including the medium temperature variation, useful work transmission, operation efficiency and heat exchange effect. Various values of heat engine high-grade temperature, heat exchange efficiency and endo-irreversibility factor are considered to analyze their effects on the outlet temperature lift/drop. The quantity and location of the exergy destruction distribution is also researched. Moreover, the relation between the heat exchange effect and the distribution of the exergy loss is researched, by which the advanced process model is proposed. With re-distribution of the exergy destruction, the advanced process has a promoted heat exchange effect compared with the original one. The result and conclusion of the this paper will offer a guidance principle for the component configuration of the practical application.
1 May 2018
Trade-offs between integration and isolation in Switzerland's energy policy
Publication date: 1 May 2018
Source:Energy, Volume 150 Author(s): P. Eser, N. Chokani, R. Abhari In response to the Fukushima nuclear accident, Switzerland has targeted to phase out nuclear power by 2050. Two diametrically opposite pathways to accomplish Switzerland's nuclear phase-out are quantitatively investigated for the year 2035 using a novel high-resolution power systems simulation framework. The first pathway, “Island in Europe”, installs new natural gas power plants to ensure a self-sufficient Swiss energy system. The second pathway, “Battery of Europe”, increases Switzerland's engagement with central Europe with new pumped hydro storages and increased cross-border electricity trade of European renewable energy. The results show that the “Battery of Europe” scenario enables a threefold increase in financial surplus of cross-border electricity trade compared to the “Island in Europe” scenario. This surplus translates to 15–23% lower domestic Swiss electricity prices, thereby enhancing the competitiveness of the Swiss marketplace; however, Switzerland is then exposed to more technical and political engagement with its neighbours. Additionally, successful implementation of the “Battery of Europe” scenario requires reinforcing 5% of the Swiss transmission grid, which necessitates more streamlined legal processes for new transmission infrastructure. Along a different political dimension, electricity price reductions of up to 22% are possible if the targeted increase of efficiency in Switzerland's energy policy is accomplished.
1 May 2018
The effect of gravity on inner transport and cell performance in passive micro direct methanol fuel cell
Publication date: 1 May 2018
Source:Energy, Volume 150 Author(s): Zhenyu Yuan, Manna Zhang, Kaiyuan Zuo, Yongqiang Ren In this paper, the effects of non-isothermal and gravity on inner methanol concentration and thermal distribution of passive micro direct methanol fuel cell (
1 May 2018
Numerical simulation on thermoelectric and mechanical performance of annular thermoelectric generator
Publication date: 1 May 2018
Source:Energy, Volume 150 Author(s): Shifa Fan, Yuanwen Gao In this paper, a three dimensional finite element model of annular thermoelectric devices is established to optimize the geometric dimensions and the number of thermocouples for the enhancement of the thermoelectric performance and mechanical reliability. The influences of geometric dimensions and the number of the thermocouples on the thermoelectric performance and the mechanical reliability of annular thermoelectric generators are investigated, respectively. The numerical results indicate that with the increasing the angle ratio of the thermoelectric leg, the maximum von Mises stress in the legs of thermocouples decreases first and then increases, and the thermoelectric performance of the annular thermocouple can be significantly improved. In addition, increasing the length of legs of thermocouples would reduce the thermoelectric performance, but improve the mechanical reliability of annular thermocouples. For the whole annular thermoelectric generator, there exists different optimal number of thermocouples to enhance the thermoelectric performance for different external resistance. The number of thermocouples has little influence on the maximum von Mises stress in the legs of annular thermoelectric generators. Finally, the optimal geometric dimensions of the annular thermoelectric generator with high thermoelectric and mechanical performance are also discussed. These results can provide some guidance for the optimization design of annular thermoelectric generators.

A novel data-driven approach for residential electricity consumption prediction based on ensemble learning
Publication date: 1 May 2018
Source:Energy, Volume 150 Author(s): Kunlong Chen, Jiuchun Jiang, Fangdan Zheng, Kunjin Chen With the development of smart grid as well as the electricity market, it is of increasing significance to predict the household electricity consumption. In this paper, a novel data-driven framework is proposed to predict the annual household electricity consumption using ensemble learning technique. The extreme gradient boosting forest and feedforward deep networks are served as base models. These base models are combined by ridge regression. What is more, the importances of input features are estimated. A subset of features is selected as the important features to feed into the model to increase its accuracy. A comparison of the proposed ensemble framework against classical regression models indicates that the former can reduce by $30 %$ of the prediction error. The results of this study show that ensemble learning method can be a convenient and accurate approach to predict household electricity consumption.
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