Energies

29 pages, 6146 KiB

Open AccessArticle

Assessment and Day-Ahead Forecasting of Hourly Solar Radiation in Medellín, Colombia

by Julián Urrego-Ortiz, J. Alejandro Martínez, Paola A. Arias and Álvaro Jaramillo-Duque

Energies 2019, 12(22), 4402; https://doi.org/10.3390/en12224402 - 19 Nov 2019

Cited by 15 | Viewed by 3549

The description and forecasting of hourly solar resource is fundamental for the operation of solar energy systems in the electric grid. In this work, we provide insights regarding the hourly variation of the global horizontal irradiance in Medellín, Colombia, a large urban area [...] Read more.

The description and forecasting of hourly solar resource is fundamental for the operation of solar energy systems in the electric grid. In this work, we provide insights regarding the hourly variation of the global horizontal irradiance in Medellín, Colombia, a large urban area within the tropical Andes. We propose a model based on Markov chains for forecasting the hourly solar irradiance for one day ahead. The Markov model was compared against estimates produced by different configurations of the weather research forecasting model (WRF). Our assessment showed that for the period considered, the average availability of the solar resource was of 5 PSH (peak sun hours), corresponding to an average daily radiation of ~5 kWh/m². This shows that Medellín, Colombia, has a substantial availability of the solar resource that can be a complementary source of energy during the dry season periods. In the case of the Markov model, the estimates exhibited typical root mean squared errors between ~80 W/m² and ~170 W/m² (~50%–~110%) under overcast conditions, and ~57 W/m² to ~171 W/m² (~16%–~38%) for clear sky conditions. In general, the proposed model had a performance comparable with the WRF model, while presenting a computationally inexpensive alternative to forecast hourly solar radiation one day in advance. The Markov model is presented as an alternative to estimate time series that can be used in energy markets by agents and power-system operators to deal with the uncertainty of solar power plants. Full article

(This article belongs to the Special Issue Renewable Energy Resource Assessment and Forecasting)

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35 pages, 6068 KiB

Open AccessFeature PaperArticle

Design and Comparative Techno-Economic Analysis of Two Solar Polygeneration Systems Applied for Electricity, Cooling and Fresh Water Production

by Ighball Baniasad Askari, Francesco Calise and Maria Vicidomini

Energies 2019, 12(22), 4401; https://doi.org/10.3390/en12224401 - 19 Nov 2019

Cited by 22 | Viewed by 3402

Abstract

Two solar polygeneration systems were investigated for electricity, cooling and fresh water production. In the first scenario (

{LF}_{PS}

), the linear Fresnel (LF) solar field was used as thermal source of the Organic Rankine Cycle (ORC), absorption chiller (ACH) and multi-effect [...] Read more.

Two solar polygeneration systems were investigated for electricity, cooling and fresh water production. In the first scenario (

{LF}_{PS}

), the linear Fresnel (LF) solar field was used as thermal source of the Organic Rankine Cycle (ORC), absorption chiller (ACH) and multi-effect desalination (MED) unit. In the second scenario (

{PV}_{PS}

), photovoltaic (PV) panels were considered as the electricity source to supply the electricity load that is required for lighting, electrical devices, compression chiller (CCH) and reverse osmosis (RO) units. A techno-economic comparison was made between two scenarios based on the land use factor (F), capacity utilization factor (CUF), payback period, levelized cost of electricity (LCE), levelized cost of cooling energy (LCC) and levelized cost of water (LCW). The calculations were conducted for four different locations in order to determine the effect of solar radiation level on the LCE, LCC and LCW of systems in both scenarios. The results showed that the LCE and LCW of

{PV}_{PS}

is lower than that of

{LF}_{PS}

and the LCC of

{LF}_{PS}

is lower than that of

{PV}_{PS}

. Also, the payback period of

{LF}_{PS}

and

{PV}_{PS}

systems are obtained as 13.97 years and 13.54 years, respectively, if no incentive is considered for the electricity sale. Full article

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22 pages, 6071 KiB

Open AccessArticle

Lead-Acid Battery Sizing for a DC Auxiliary System in a Substation by the Optimization Method

by Janez Ribič, Jože Pihler, Robert Maruša, Filip Kokalj and Peter Kitak

Energies 2019, 12(22), 4400; https://doi.org/10.3390/en12224400 - 19 Nov 2019

Cited by 4 | Viewed by 3985

Abstract

Lead-acid batteries are the most frequently used energy storage facilities for the provision of a backup supply of DC auxiliary systems in substations and power plants due to their long service life and high reliability. It is possible to define the load in [...] Read more.

Lead-acid batteries are the most frequently used energy storage facilities for the provision of a backup supply of DC auxiliary systems in substations and power plants due to their long service life and high reliability. It is possible to define the load in these systems, therefore the IEEE 485 Standard can be used for the selection of batteries according to the conventional method of selection. Special attention is paid in the paper to the technical selection of a lead-acid battery, which depends on its operational reliability that decreases with battery aging. It is defined by the extent of maintenance during its service life. A cost analysis was also carried out, which took into consideration maintenance and procurement costs, as well as the costs of the related air conditioning that keeps the prescribed temperature and ventilates the battery room. The impact is shown of selecting a lead-acid battery on the battery room’s operating safety when charging. The final selection of lead-acid battery is performed using an optimization algorithm of differential evolution. Using the optimization process, the new battery selection method includes the technical sizing criteria of the lead-acid battery, reliability of operation with maintenance, operational safety, and cost analysis. Two cases of selection of lead-acid batteries for the backup supply of a DC auxiliary system in a transmission substation are presented in the paper, where the input data were determined based on measurements in an existing substation. A comparison is made between the existing conventional and new lead-acid battery selection method based on optimization. Full article

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25 pages, 1007 KiB

Open AccessFeature PaperReview

On the Energy Efficiency in the Next Generation of Smart Buildings—Supporting Technologies and Techniques

by César Benavente-Peces

Energies 2019, 12(22), 4399; https://doi.org/10.3390/en12224399 - 19 Nov 2019

Cited by 36 | Viewed by 7904

Abstract

Energy efficiency is one of the most relevant issues that the scientific community, and society in general, must face in the next years. Furthermore, higher energy efficiencies will contribute to worldwide sustainability. Buildings are responsible for 40% of the overall consumed energy. Smart [...] Read more.

Energy efficiency is one of the most relevant issues that the scientific community, and society in general, must face in the next years. Furthermore, higher energy efficiencies will contribute to worldwide sustainability. Buildings are responsible for 40% of the overall consumed energy. Smart Grids and Smart Buildings are playing an essential role in the definition of the next generation of sustainable Smart Cities. The main goal is reducing the impact of energy consumption on the environment as much as possible. This paper focuses on information communication technologies (ICTs) and techniques, their key characteristics and contribution to obtain higher energy efficiencies in smart buildings. Given that electrical energy is the most used, the investigation mainly centres on this energy. This paper also pays attention to green energies and energy harvesting due to their contribution to energy efficiency by providing additional clean energy. The main contribution of this investigation is pointing out the most relevant existing and emerging ICT technologies and techniques which can be used to optimize the energy efficiency of Smart Buildings. The research puts special attention on available, novel and emerging sensors, communication technologies and standards, intelligence techniques and algorithms, green energies and energy harvesting. All of them enable high-performance intelligent systems to optimize energy consumption and occupants’ comfort. Furthermore, it remarks on the most suitable technologies and techniques, their main features and their applications in Smart Buildings. Full article

(This article belongs to the Special Issue Efficient Electrification Control Systems for Smart Buildings)

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25 pages, 7327 KiB

Open AccessArticle

Climate Compensation and Indoor Temperature Optimal Measuring Point Energy Saving Control in VAV Air-Conditioning System

by Xiuying Yan, Cong Liu, Meili Li, Ating Hou, Kaixing Fan and Qinglong Meng

Energies 2019, 12(22), 4398; https://doi.org/10.3390/en12224398 - 19 Nov 2019

Cited by 5 | Viewed by 3372

Abstract

Temperature measuring point is the key to room environment control. Temperature measuring points and climate changes are directly related to the room control effect. It is of great theoretical and practical significance to study the temperature measuring points and control strategy based on [...] Read more.

Temperature measuring point is the key to room environment control. Temperature measuring points and climate changes are directly related to the room control effect. It is of great theoretical and practical significance to study the temperature measuring points and control strategy based on climate compensation. In this study, first, the climate compensation concept in a heating system was introduced into a variable air volume (VAV) air-conditioning system. The heating load was modeled as a function of supply air temperature by analyzing the heat exchange. Based on each control link of subsystems, a climate compensation scheme is proposed to determine the optimal set-point of the supply air temperature. At the same time, a layout of multiple temperature measuring points of an air-conditioned room was studied. Furthermore, the optimal indoor temperature measuring point was determined using an adaptive weighted fusion method. Finally, simulation results show that the proposed method has better control effects on indoor temperature adjustment compared with the traditional method. The optimal supply air temperature in summer and winter was determined according to the proposed climate compensation scheme, and the supply air temperature was controlled using an improved single-neuron adaptive control strategy. Experimental results show that the maximum energy saving can reach up to 35.5% in winter and 6.1% in summer. Full article

(This article belongs to the Special Issue Building Renewable Energy and Thermal Energy Storage System 2019)

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14 pages, 4467 KiB

Open AccessArticle

Using the Magnetotelluric Method for Detecting Aquifer Failure Characteristics under High-Intensity Mining of Thick Coal Seams

by Erhu Bai, Wenbing Guo, Dongsheng Zhang, Yi Tan, Mingjie Guo and Gaobo Zhao

Energies 2019, 12(22), 4397; https://doi.org/10.3390/en12224397 - 19 Nov 2019

Cited by 15 | Viewed by 2845

Abstract

In the ecologically fragile mining area of northwest China, high-intensity mining has seriously affected the aquifer and surface eco-environment. In order to better implement water-preserved mining in ecologically fragile areas, the aquifer failure characteristics should be first detected accurately; therefore, it is necessary [...] Read more.

In the ecologically fragile mining area of northwest China, high-intensity mining has seriously affected the aquifer and surface eco-environment. In order to better implement water-preserved mining in ecologically fragile areas, the aquifer failure characteristics should be first detected accurately; therefore, it is necessary to find a convenient and fast detection method. Based on the analysis of the basic principles and influencing factors of the magnetotelluric (MT) method, the feasibility of using the MT method to detect aquifer failure is verified by testing the mined area with MT detection and field borehole measurement. Subsequently, the failure characteristics of overburden and unconsolidated aquifers under high-intensity mining are studied by MT detection and physical simulation. By comparing the physical simulation with the field measurement from the aspects of the maximum surface subsidence, interval of periodic weighting and step cracks, the reliability of the height of the water flowing fracture zone and caving zone obtained from physical simulation is verified. The analysis from MT detection and physical simulation shows that the results of the two methods are in accord with each other, which further confirms that the MT method can be used to detect the failure of overburdened structures and aquifers. The penetrating fractures are the main channel for the downward seepage of water resources, which is caused by the “two-zone” of overburden model and located in the “dimple” shape in the apparent resistivity (AR) isogram. It can provide a reference and technical support for the corresponding new water-preserved mining technology and the construction of digital mines. Full article

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32 pages, 16909 KiB

Open AccessEditor’s ChoiceArticle

A Novel Dual Fuel Reaction Mechanism for Ignition in Natural Gas–Diesel Combustion

by Sebastian Schuh, Jens Frühhaber, Thomas Lauer and Franz Winter

Energies 2019, 12(22), 4396; https://doi.org/10.3390/en12224396 - 19 Nov 2019

Cited by 8 | Viewed by 3355

Abstract

In this study, a reaction mechanism is presented that is optimized for the simulation of the dual fuel combustion process using n-heptane and a mixture of methane/propane as surrogate fuels for diesel and natural gas, respectively. By comparing the measured and calculated [...] Read more.

In this study, a reaction mechanism is presented that is optimized for the simulation of the dual fuel combustion process using n-heptane and a mixture of methane/propane as surrogate fuels for diesel and natural gas, respectively. By comparing the measured and calculated ignition delay times (IDTs) of different homogeneous methane–propane–n-heptane mixtures, six different n-heptane mechanisms were investigated and evaluated. The selected mechanism was used for computational fluid dynamics (CFD) simulations to calculate the ignition of a diesel spray injected into air and a natural gas–air mixture. The observed deviations between the simulation results and the measurements performed with a rapid compression expansion machine (RCEM) and a combustion vessel motivated the adaptation of the mechanism by adjusting the Arrhenius parameters of individual reactions. For the identification of the reactions suitable for the mechanism adaption, sensitivity and flow analyzes were performed. The adjusted mechanism is able to describe ignition phenomena in the context of natural gas–diesel, i.e., dual fuel combustion. Full article

(This article belongs to the Section B: Energy and Environment)

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29 pages, 2663 KiB

Open AccessEditor’s ChoiceArticle

Towards the EU Emission Targets of 2050: Cost-Effective Emission Reduction in Finnish Detached Houses

by Janne Hirvonen, Juha Jokisalo, Juhani Heljo and Risto Kosonen

Energies 2019, 12(22), 4395; https://doi.org/10.3390/en12224395 - 19 Nov 2019

Cited by 34 | Viewed by 4682

Abstract

To mitigate the effects of climate change, the European Union calls for major carbon emission reductions in the building sector through a deep renovation of the existing building stock. This study examines the cost-effective energy retrofit measures in Finnish detached houses. The Finnish [...] Read more.

To mitigate the effects of climate change, the European Union calls for major carbon emission reductions in the building sector through a deep renovation of the existing building stock. This study examines the cost-effective energy retrofit measures in Finnish detached houses. The Finnish detached house building stock was divided into four age classes according to the building code in effect at the time of their construction. Multi-objective optimization with a genetic algorithm was used to minimize the life cycle cost and CO₂ emissions in each building type for five different main heating systems (district heating, wood/oil boiler, direct electric heating, and ground-source heat pump) by improving the building envelope and systems. Cost-effective emission reductions were possible with all heating systems, but especially with ground-source heat pumps. Replacing oil boilers with ground-source heat pumps (GSHPs), emissions could be reduced by 79% to 92% across all the studied detached houses and investment levels. With all the other heating systems, emission reductions of 20% to 75% were possible. The most cost-effective individual renovation measures were the installation of air-to-air heat pumps for auxiliary heating and improving the thermal insulation of external walls. Full article

(This article belongs to the Special Issue Energy and Technical Building Systems - Scientific and Technological Advances)

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18 pages, 5876 KiB

Open AccessArticle

Application of Spectral Clustering Algorithm to ES-MDA with DCT for History Matching of Gas Channel Reservoirs

by Sungil Kim and Kyungbook Lee

Energies 2019, 12(22), 4394; https://doi.org/10.3390/en12224394 - 19 Nov 2019

Cited by 1 | Viewed by 2983

Abstract

History matching is a calibration of reservoir models according to their production history. Although ensemble-based methods (EBMs) have been researched as promising history matching methods, reservoir parameters updated using EBMs do not have ideal geological features because of a Gaussian assumption. This study [...] Read more.

History matching is a calibration of reservoir models according to their production history. Although ensemble-based methods (EBMs) have been researched as promising history matching methods, reservoir parameters updated using EBMs do not have ideal geological features because of a Gaussian assumption. This study proposes an application of spectral clustering algorithm (SCA) on ensemble smoother with multiple data assimilation (ES-MDA) as a parameterization technique for non-Gaussian model parameters. The proposed method combines discrete cosine transform (DCT), SCA, and ES-MDA. After DCT is used to parameterize reservoir facies to conserve their connectivity and geometry, ES-MDA updates the coefficients of DCT. Then, SCA conducts a post-process of rock facies assignment to let the updated model have discrete values. The proposed ES-MDA with SCA and DCT gives a more trustworthy history matching performance than the preservation of facies ratio (PFR), which was utilized in previous studies. The SCA considers a trend of assimilated facies index fields, although the PFR classifies facies through a cut-off with a pre-determined facies ratio. The SCA properly decreases uncertainty of the dynamic prediction. The error rate of ES-MDA with SCA was reduced by 42% compared to the ES-MDA with PFR, although it required an extra computational cost of about 9 min for each calibration of an ensemble. Consequently, the SCA can be proposed as a reliable post-process method for ES-MDA with DCT instead of PFR. Full article

(This article belongs to the Section L: Energy Sources)

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20 pages, 8238 KiB

Open AccessArticle

Partial State-of-Charge Mitigation in Standalone Photovoltaic Hybrid Storage Systems

by Iván Sanz-Gorrachategui, Carlos Bernal Ruiz, Estanis Oyarbide Usabiaga, Antonio Bono Nuez, Sergio Jesús Artal Sevil, Erik Garayalde Pérez, Iosu Aizpuru Larrañaga and Jose María Canales Segade

Energies 2019, 12(22), 4393; https://doi.org/10.3390/en12224393 - 19 Nov 2019

Cited by 3 | Viewed by 2409

Abstract

Energy Storage in photovoltaic installations has increased in popularity in recent years due to the improvement in solar panel technology and energy storage systems. In several places where the grid is not available, in remote isolated rural locations or developing countries, isolated photovoltaic [...] Read more.

Energy Storage in photovoltaic installations has increased in popularity in recent years due to the improvement in solar panel technology and energy storage systems. In several places where the grid is not available, in remote isolated rural locations or developing countries, isolated photovoltaic installations are one of the main options to power DC micro-grids. In these scenarios, energy storage elements are mandatory due to the natural day-night cycles and low irradiation periods. Traditionally, lead-acid batteries have been responsible for this task, due to their availability and low cost. However, the intermittent features of the solar irradiance patterns and load demand, generate multiple shallow charge–discharge cycles or high power pulses, which worsen the performance of these batteries. Some Hybrid Energy Storage Systems (HESSs) have been reported in the literature to enhance the lifetime and power capabilities of these storage elements, but they are not intended to overcome the Partial State of Charge (PSoC) issue caused by daily cycles, which has an effect on the short and mid-term performance of the system. This paper studies the impact of the already proposed HESSs on PSoC operation, establishing the optimal hybrid ratios, and implementing them in a real installation with a satisfactory outcome. Full article

(This article belongs to the Special Issue Solar Energy Harvesting, Storage and Application)

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30 pages, 537 KiB

Open AccessReview

Recent Approaches of Forecasting and Optimal Economic Dispatch to Overcome Intermittency of Wind and Photovoltaic (PV) Systems: A Review

by Manzoor Ellahi, Ghulam Abbas, Irfan Khan, Paul Mario Koola, Mashood Nasir, Ali Raza and Umar Farooq

Energies 2019, 12(22), 4392; https://doi.org/10.3390/en12224392 - 19 Nov 2019

Cited by 38 | Viewed by 3609

Abstract

Renewable energy sources (RESs) are the replacement of fast depleting, environment polluting, costly, and unsustainable fossil fuels. RESs themselves have various issues such as variable supply towards the load during different periods, and mostly they are available at distant locations from load centers. [...] Read more.

Renewable energy sources (RESs) are the replacement of fast depleting, environment polluting, costly, and unsustainable fossil fuels. RESs themselves have various issues such as variable supply towards the load during different periods, and mostly they are available at distant locations from load centers. This paper inspects forecasting techniques, employed to predict the RESs availability during different periods and considers the dispatch mechanisms for the supply, extracted from these resources. Firstly, we analyze the application of stochastic distributions especially the Weibull distribution (WD), for forecasting both wind and PV power potential, with and without incorporating neural networks (NN). Secondly, a review of the optimal economic dispatch (OED) of RES using particle swarm optimization (PSO) is presented. The reviewed techniques will be of great significance for system operators that require to gauge and pre-plan flexibility competence for their power systems to ensure practical and economical operation under high penetration of RESs. Full article

(This article belongs to the Special Issue Application of Power Electronics Converters in Smart Grids and Renewable Energy Systems)

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17 pages, 3453 KiB

Open AccessArticle

Multi-Criteria and Life Cycle Assessment of Wood-Based Bioenergy Alternatives for Residential Heating: A Sustainability Analysis

by Mario Martín-Gamboa, Luis C. Dias, Paula Quinteiro, Fausto Freire, Luís Arroja and Ana Cláudia Dias

Energies 2019, 12(22), 4391; https://doi.org/10.3390/en12224391 - 19 Nov 2019

Cited by 20 | Viewed by 3367

Abstract

Moving towards a global bioeconomy can mitigate climate change and the depletion of fossil fuels. Within this context, this work applies a set of multi-criteria decision analysis (MCDA) tools to prioritise the selection of five alternative bioenergy systems for residential heating based on [...] Read more.

Moving towards a global bioeconomy can mitigate climate change and the depletion of fossil fuels. Within this context, this work applies a set of multi-criteria decision analysis (MCDA) tools to prioritise the selection of five alternative bioenergy systems for residential heating based on the combination of three commercial technologies (pellet, wood stove and traditional fireplace) and two different feedstocks (eucalypt and maritime pine species). Several combinations of MCDA methods and weighting approaches were compared to assess how much results can differ. Eight indicators were used for a sustainability assessment of the alternatives while four MCDA methods were applied for the prioritisation: Weighted Sum Method (WSM), Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS), Elimination and Choice Expressing Reality (ELECTRE), and Preference Ranking Organization Method for Enrichment Evaluation (PROMETHEE). Regarding the sustainability performance indicators, the highest environmental impacts were calculated for the fireplace alternatives, and there was not a best environmental option. Also, no clear trend was found for the economic and social dimensions. The application of MCDA tools shows that wood stove alternatives have the best sustainability performance, in particular wood stove with combustion of maritime pine logs (highest scores in the ranking). Regarding the worst alternative, fireplaces with combustion of eucalypt logs ranked last in all MCDA rankings. Finally, a sensitivity analysis for the weighting of the performance indicators confirmed wood stoves with combustion of maritime pine logs as the leading alternative and the key role of the analysts within this type of MCDA studies. Full article

(This article belongs to the Special Issue Advances in Environmental, Economic and Social Assessment of Energy Systems)

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17 pages, 1177 KiB

Open AccessArticle

Low Chlorine Fuel Pellets Production from the Mixture of Hydrothermally Treated Hospital Solid Waste, Pyrolytic Plastic Waste Residue and Biomass

by Md Tanvir Alam, Jang-Soo Lee, Sang-Yeop Lee, Dhruba Bhatta, Kunio Yoshikawa and Yong-Chil Seo

Energies 2019, 12(22), 4390; https://doi.org/10.3390/en12224390 - 19 Nov 2019

Cited by 11 | Viewed by 3177

Abstract

Thirteen types of fuel pellets were prepared from hydrothermally treated hospital solid waste, hydrothermally treated rice straw, pyrolytic plastic waste residue, rice straw, and Sakhalin fir residue using a flat die pellet machine. Different pellet properties such as pellet density, pellet durability, aspect [...] Read more.

Thirteen types of fuel pellets were prepared from hydrothermally treated hospital solid waste, hydrothermally treated rice straw, pyrolytic plastic waste residue, rice straw, and Sakhalin fir residue using a flat die pellet machine. Different pellet properties such as pellet density, pellet durability, aspect ratio, physicochemical characteristics, and gross calorific value (GCV) were evaluated as well as compared concerning the European standard specification for residential/commercial densified fuels. In addition, the quality of pellets was compared with coal. The results showed that the pellets made only with hydrothermally treated hospital solid waste, hydrothermally treated rice straw, pyrolytic plastic waste residue, and rice straw failed to meet few individual criteria (<3 wt% ash content, <10 wt% moisture content, <0.03 wt% chlorine content, >96.5 wt% pellet durability, and >600 kg/m³ pellet density) of the European standard specifications. However, most of the mixed fuel pellets satisfied the requirement of pellet properties according to the European standard specification. In particular, up to 16.70 wt% hydrothermally treated rice straw, 1.50 wt% hydrothermally treated hospital solid waste, and 4.76 wt% of pyrolytic plastic waste residue can be blended with Shakhalin fir residue to produce low-chlorine fuel pellets. The gross calorific value of pellets made from the mixture of hydrothermally treated wastes and pyrolytic plastic waste residue (around 22 MJ/kg) showed similar results to that of coal. In the case of mixed pellets, the presence of these hydrothermally treated wastes and pyrolytic plastic waste residue valorized the fuel pellet quality. The main outcome of this study was the production of low chlorine biomass fuel pellets of high gross calorific values blended with hydrothermally treated wastes and pyrolytic waste residues, which opens a new door for utilizing waste in a better way, especially hospital solid waste. Full article

(This article belongs to the Section A4: Bio-Energy)

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15 pages, 1038 KiB

Open AccessArticle

Wavelet Packet Decomposition for IEC Compliant Assessment of Harmonics under Stationary and Fluctuating Conditions

by Stefano Lodetti, Jorge Bruna, Julio J. Melero and José F. Sanz

Energies 2019, 12(22), 4389; https://doi.org/10.3390/en12224389 - 19 Nov 2019

Cited by 5 | Viewed by 2303

Abstract

This paper presents the validation and characterization of a wavelet based decomposition method for the assessment of harmonic distortion in power systems, under stationary and non-stationary conditions. It uses Wavelet Packet Decomposition with Butterworth Infinite Impulse Response filters and a decomposition structure, which [...] Read more.

This paper presents the validation and characterization of a wavelet based decomposition method for the assessment of harmonic distortion in power systems, under stationary and non-stationary conditions. It uses Wavelet Packet Decomposition with Butterworth Infinite Impulse Response filters and a decomposition structure, which allows the measurement of both odd and even harmonics, up to the 63rd order, fully compliant with the requirements of the IEC 61000-4-7 standard. The method is shown to fulfil the IEC accuracy requirements for stationary harmonics, obtaining the same accuracy even under fluctuating conditions. Then, it is validated using simulated signals with real harmonic content. The proposed method is proven to be fully equivalent to Fourier analysis under stationary conditions, being often more accurate. Under non-stationary conditions, instead, it provides significantly higher accuracy, while the IEC strategy produces large errors. Lastly, the method is tested with real current and voltage signals, measured in conditions of high harmonic distortion. The proposed strategy provides a method with superior performance for fluctuating harmonics, but at the same time IEC compliant under stationary conditions. Full article

(This article belongs to the Special Issue Advanced Signal Processing Techniques Applied to Power Systems Control and Analysis)

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21 pages, 6759 KiB

Open AccessFeature PaperArticle

Looking for Energy Losses of a Rotary Permanent Magnet Magnetic Refrigerator to Optimize Its Performances

by Angelo Maiorino, Antongiulio Mauro, Manuel Gesù Del Duca, Adrián Mota-Babiloni and Ciro Aprea

Energies 2019, 12(22), 4388; https://doi.org/10.3390/en12224388 - 19 Nov 2019

Cited by 7 | Viewed by 2838

Abstract

In this paper, an extensive study on the energy losses of a magnetic refrigerator prototype developed at University of Salerno, named ‘8MAG’, is carried out with the aim to improve the performance of such a system. The design details of ‘8MAG’ evidences both [...] Read more.

In this paper, an extensive study on the energy losses of a magnetic refrigerator prototype developed at University of Salerno, named ‘8MAG’, is carried out with the aim to improve the performance of such a system. The design details of ‘8MAG’ evidences both mechanical and thermal losses, which are mainly attributed to the eddy currents generation into the support of the regenerators (magnetocaloric wheel) and the parasitic heat load of the rotary valve. The latter component is fundamental since it imparts the direction of the heat transfer fluid distribution through the regenerators and it serves as a drive shaft for the magnetic assembly. The energy losses concerning eddy currents and parasitic heat load are evaluated by two uncoupled models, which are validated by experimental data obtained with different operating conditions. Then, the achievable coefficient of performance (COP) improvements of ‘8MAG’ are estimated, showing that reducing eddy currents generation (by changing the material of the magnetocaloric wheel) and the parasitic heat load (enhancing the insulation of the rotary valve) can lead to increase the COP from 2.5 to 2.8 (+12.0%) and 3.0 (+20%), respectively, and to 3.3 (+32%), combining both improvements, with an hot source temperature of 22 °C and 2 K of temperature span. Full article

(This article belongs to the Special Issue Refrigeration Systems and Applications 2019)

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15 pages, 3467 KiB

Open AccessArticle

Optimal Coordination of Wind Power and Pumped Hydro Energy Storage

by Hussein M. K. Al-Masri, Ayman Al-Quraan, Ahmad AbuElrub and Mehrdad Ehsani

Energies 2019, 12(22), 4387; https://doi.org/10.3390/en12224387 - 19 Nov 2019

Cited by 17 | Viewed by 2781

Abstract

A study combining wind power with pumped hydro energy storage for the Jordanian utility grid is presented. Three solvers of the Matlab optimization toolbox are used to find the optimal solution for the cost of energy in a combined on-grid system. Genetic algorithm, [...] Read more.

A study combining wind power with pumped hydro energy storage for the Jordanian utility grid is presented. Three solvers of the Matlab optimization toolbox are used to find the optimal solution for the cost of energy in a combined on-grid system. Genetic algorithm, simulated annealing (SA), and pattern search (PS) solvers are used to find the optimal solution. The GA solution of 0.0955388 $/kWh is economically feasible. This is 28.7% lower than the electricity purchased from the conventional utility grid. The discounted payback period to recover the total cost is 10.271 years. The suggested configuration is shown to be feasible by comparing it to real measurements for this case and a previous wind-only case. It is shown that the indicators of the optimal solution are improved. For instance, carbon dioxide emissions (E_CO2) and conventional grid energy purchases are reduced by 24.69% and 24.68%, respectively. Moreover, it is shown that the benefits of adding hydro storage, combined with increasing the number of wind turbine units, reduces the cost of energy of renewables (COE_Renewables). Therefore, combining hydro storage with wind power is economically, environmentally, and technically a more efficient alternative to the conventional power generation. Full article

(This article belongs to the Special Issue Challenges and Opportunities for the Renewable Energy Economy)

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14 pages, 4996 KiB

Open AccessArticle

Modeling the Effect of the Loss of Cyclable Lithium on the Performance Degradation of a Lithium-Ion Battery

by Dongcheul Lee, Boram Koo, Chee Burm Shin, So-Yeon Lee, Jinju Song, Il-Chan Jang and Jung-Je Woo

Energies 2019, 12(22), 4386; https://doi.org/10.3390/en12224386 - 18 Nov 2019

Cited by 9 | Viewed by 2626

Abstract

This paper reports a modeling methodology to predict the effect of the loss of cyclable lithium of a lithium-ion battery (LIB) cell comprised of a LiNi_0.6Co_0.2Mn_0.2O₂ cathode, natural graphite anode, and an organic electrolyte on the [...] Read more.

This paper reports a modeling methodology to predict the effect of the loss of cyclable lithium of a lithium-ion battery (LIB) cell comprised of a LiNi_0.6Co_0.2Mn_0.2O₂ cathode, natural graphite anode, and an organic electrolyte on the discharge behavior. A one-dimensional model based on a finite element method is presented to calculate the discharge behaviors of an LIB cell during galvanostatic discharge for various levels of the loss of cyclable lithium. Modeling results for the variation of the cell voltage of the LIB cell are compared with experimental measurements during galvanostatic discharge at various discharge rates for three different levels of the loss of cyclable lithium to validate the model. The calculation results obtained from the model are in good agreement with the experimental measurements. On the basis of the validated modeling approach, the effects of the loss of cyclable lithium on the discharge capacity and available discharge power of the LIB cell are estimated. The modeling results exhibit strong dependencies of the discharge behavior of an LIB cell on the discharge C-rate and the loss of cyclable lithium. Full article

(This article belongs to the Section D: Energy Storage and Application)

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25 pages, 7691 KiB

Open AccessArticle

Investigation of Heat Management in High Thermal Density Communication Cabinet by a Rear Door Liquid Cooling System

by Wansheng Yang, Lin Yang, Junjie Ou, Zhongqi Lin and Xudong Zhao

Energies 2019, 12(22), 4385; https://doi.org/10.3390/en12224385 - 18 Nov 2019

Cited by 2 | Viewed by 3119

Abstract

In this paper, a rear door oil-cooling heat exchanger for data center cabinet-level cooling has been proposed. In order to solve the heat dissipation problem of high heat density data center, this paper applied the mature transformer oil cooling technology to the data [...] Read more.

In this paper, a rear door oil-cooling heat exchanger for data center cabinet-level cooling has been proposed. In order to solve the heat dissipation problem of high heat density data center, this paper applied the mature transformer oil cooling technology to the data room. The heat dissipation of liquid-cooled cabinets and traditional air-cooled cabinets was compared, and the heat dissipation performance of the oil-cooled system was theoretically and experimentally investigated. To investigate the heat dissipation system, the cabinet operating temperature, circulating oil system temperature and cabinet exhaust temperature, cabinet heat density, oil flow rates and fan power were analyzed. It was found that the average cooling efficiency of the liquid-cooled cabinet increased by 66% compared with the average cooling efficiency of the conventional air-cooled cabinet. The operating temperature in air-cooled cabinets is as high as 55 °C, and the operating temperature in liquid-cooled cabinets does not exceed 50 °C. Among which, the maximum heat dissipation efficiency of the liquid-cooled cabinets can reach 58.8%. The oil temperature could reach 46.9 °C after heat exchange, and the exhaust air of the cabinet could reach 42.8 °C, which could be used to prepare domestic water and regenerative desiccant. The results from established calculation model agreed well with the testing results and the model could be used to predict the heat dissipation law of the oil cooling system under different conditions. The research has proposed the potential application of the oil-cooled in cabinet-level cooling, which can help realize saving primary energy and reducing carbon emission. Full article

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15 pages, 1456 KiB

Open AccessArticle

Technologies of Engagement: How Battery Storage Technologies Shape Householder Participation in Energy Transitions

by Sanneke Kloppenburg, Robin Smale and Nick Verkade

Energies 2019, 12(22), 4384; https://doi.org/10.3390/en12224384 - 18 Nov 2019

Cited by 20 | Viewed by 3983

Abstract

The transition to a low-carbon energy system goes along with changing roles for citizens in energy production and consumption. In this paper we focus on how residential energy storage technologies can enable householders to contribute to the energy transition. Drawing on literature that [...] Read more.

The transition to a low-carbon energy system goes along with changing roles for citizens in energy production and consumption. In this paper we focus on how residential energy storage technologies can enable householders to contribute to the energy transition. Drawing on literature that understands energy systems as sociotechnical configurations and the theory of ‘material participation’, we examine how the introduction of home batteries affords new roles and energy practices for householders. We present qualitative findings from interviews with householders and other key stakeholders engaged in using or implementing battery storage at household and community level. Our results point to five emerging storage modes in which householders can play a role: individual energy autonomy; local energy community; smart grid integration; virtual energy community; and electricity market integration. We argue that for householders, these storage modes facilitate new energy practices such as providing grid services, trading, self-consumption, and sharing of energy. Several of the storage modes enable the formation of prosumer collectives and change relationships with other actors in the energy system. We conclude by discussing how householders also face new dependencies on information technologies and intermediary actors to organize the multi-directional energy flows which battery systems unleash. With energy storage projects currently being provider-driven, we argue that more space should be given to experimentation with (mixed modes of) energy storage that both empower householders and communities in the pursuit of their own sustainability aspirations and serve the needs of emerging renewable energy-based energy systems. Full article

(This article belongs to the Special Issue New Pathways for Community Energy and Storage)

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20 pages, 2854 KiB

Open AccessArticle

Energy and Emission Characteristics of Biowaste from the Corn Grain Drying Process

by Grzegorz Maj, Joanna Szyszlak-Bargłowicz, Grzegorz Zając, Tomasz Słowik, Paweł Krzaczek and Wiesław Piekarski

Energies 2019, 12(22), 4383; https://doi.org/10.3390/en12224383 - 18 Nov 2019

Cited by 19 | Viewed by 3844

Abstract

This paper presents the results of the evaluation of the energy potential of waste from the process of drying corn grain in the form of corn cobs, damaged grains, corn grain husks, and mixtures of starting materials. A technical and elementary analysis was [...] Read more.

This paper presents the results of the evaluation of the energy potential of waste from the process of drying corn grain in the form of corn cobs, damaged grains, corn grain husks, and mixtures of starting materials. A technical and elementary analysis was performed for the biomass under investigation. The elemental composition of ash and the tendencies for slagging and boiler slagging were determined, and the emission factors were estimated based on the elemental analysis performed. The tests showed the highest calorific value among the starting materials for corn cobs (CCs) (14.94 MJ·kg⁻¹) and for the mixture of corn cobs with corn husk (CC–CH) (13.70 MJ·kg⁻¹). The estimated emission factors were within ranges of 38.26–63.26 kg·Mg⁻¹ for CO, 936–1549 kg·Mg⁻¹ for CO₂, 0.85–4.32 kg·Mg⁻¹ for NO_x, 0.91–1.03 kg·Mg⁻¹ for SO₂, and 3.88–54.31 kg·Mg⁻¹ for dust. The research showed that the creation of mixtures from starting materials leads to materials with lower potential for negative environmental impact as well as a reduced risk of slagging and fouling of biomass boilers. However, taking into account all the parameters determined for the biomass under study, the highest energy potential was characteristic for corn cobs and the mixture of corn cobs with corn husk. Full article

(This article belongs to the Special Issue Bioelectrochemical Systems (BES) for Sustainable Energy Production)

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19 pages, 1108 KiB

Open AccessArticle

Energy Justice as Part of the Acceptance of Wind Energy: An Analysis of Limburg in The Netherlands

by Nikki Kluskens, Véronique Vasseur and Rowan Benning

Energies 2019, 12(22), 4382; https://doi.org/10.3390/en12224382 - 18 Nov 2019

Cited by 9 | Viewed by 3584

Abstract

Policy documents in Limburg stress the importance of participation and distribution of benefits in wind energy projects, but it is not clear which modes of participation and distribution of benefits are most just, both in terms of perceived justice, and in terms of [...] Read more.

Policy documents in Limburg stress the importance of participation and distribution of benefits in wind energy projects, but it is not clear which modes of participation and distribution of benefits are most just, both in terms of perceived justice, and in terms of justice principles. Research shows that considering justice in renewable energy transitions increases the level of acceptance. This study aims to provide insight in what modes of participation and distribution are perceived as most just and likely to create local acceptance of wind parks. The most preferred modes are being compared to the indicators of the energy justice framework in order if they meet the criteria for a fair procedure and distribution of outcomes. Based on semi-structured interviews the analysis of the data demonstrated that different modes of participation in different phases of the process are being preferred and that a balance between modes of distribution of benefits is preferred. The results indicate that the most preferred modes of participation cannot necessarily address all indicators of procedural justice and that depending on the mode of distribution of benefits and the balance between those modes indicators of distributive justice can be addressed. Full article

(This article belongs to the Special Issue New Pathways for Community Energy and Storage)

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22 pages, 1342 KiB

Open AccessReview

Microgrids Literature Review through a Layers Structure

by Miguel Carpintero-Rentería, David Santos-Martín and Josep M. Guerrero

Energies 2019, 12(22), 4381; https://doi.org/10.3390/en12224381 - 18 Nov 2019

Cited by 48 | Viewed by 4306

Abstract

Within a distributed generation (DG) system, microgrids (MGs) are an alternative approach that may provide both resiliency and efficiency benefits. In this review, an analysis of both research and industrial documents was done. In order to establish a solid foundation of the MGs [...] Read more.

Within a distributed generation (DG) system, microgrids (MGs) are an alternative approach that may provide both resiliency and efficiency benefits. In this review, an analysis of both research and industrial documents was done. In order to establish a solid foundation of the MGs concept, a comparison of various definitions written by distinguished authors has been made. Segmenting the information of MGs into layers facilitates its analysis, search, and comparison. Therefore, this paper continuous with a layer approach from other studies and incorporates the concept of the environment as a key element that has a high impact on the microgrid functional structure. With the foundation of the MG concept, an exhaustive literature review has been developed about the main microgrid layers, such as business, standard, climate, infrastructure or control, and operation. Full article

(This article belongs to the Section F: Electrical Engineering)

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15 pages, 4349 KiB

Open AccessArticle

Tidal Current Energy Resource Distribution in Korea

by Su-jin Hwang and Chul H. Jo

Energies 2019, 12(22), 4380; https://doi.org/10.3390/en12224380 - 18 Nov 2019

Cited by 9 | Viewed by 3240

Abstract

Korea is a very well-known country for having abundant tidal current energy resources. There are many attractive coastal areas for the tidal current power that have very strong currents due to the high tidal range and the acceleration through the narrow channels between [...] Read more.

Korea is a very well-known country for having abundant tidal current energy resources. There are many attractive coastal areas for the tidal current power that have very strong currents due to the high tidal range and the acceleration through the narrow channels between islands in the west and south coasts of the Korean peninsula. Recently, the Korean government announced a plan that aims to increase the portion of electricity generated from renewable energy to 20% by 2030. Korea has abundant tidal current energy resources; however, as reliable resource assessment results of tidal current energy are not sufficient, the portion of tidal current power is very small in the plan. Therefore, a reliable resource assessment should be conducted in order to provide a basis for the development plan. This paper describes the resource assessment of tidal current energy in Korea based on the observational data provided by KHOA (Korean Hydrographic and Oceanographic Agency) and numerical simulation of water circulation. As the observational data were unable to present the detailed distribution of the complicated tidal current between islands, numerical simulation of water circulation was used to describe the detailed distribution of tidal current in Incheon-Gyeonggi and Jeollanam-do, where the tidal energy potentials are abundant. The west and south coastal areas of Korea were divided into seven regions according to the administrative district, and the theoretical tidal current potential was calculated using average power intercepted. The results of this research can provide the insight of the tidal current energy development plan in Korea. Full article

(This article belongs to the Section A: Sustainable Energy)

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20 pages, 5861 KiB

Open AccessArticle

New Fast MPPT Method Based on a Power Slope Detector for Single Phase PV Inverters

by Jose Miguel Espi and Jaime Castello

Energies 2019, 12(22), 4379; https://doi.org/10.3390/en12224379 - 18 Nov 2019

Cited by 3 | Viewed by 2856

Abstract

This article presents a novel MPPT method for two stage PV inverters with a single phase connection to the power grid. The method takes advantage of the 100 Hz/120 Hz harmonic present on the DC-bus voltage to guide the MPP search. It consists [...] Read more.

This article presents a novel MPPT method for two stage PV inverters with a single phase connection to the power grid. The method takes advantage of the 100 Hz/120 Hz harmonic present on the DC-bus voltage to guide the MPP search. It consists of detecting the slope of the P-V curve and integrating it to obtain the duty-cycle. The power slope detector (PSD) is able to calculate the P-V slope to command the MPPT even at very low powers, where the amplitude of the oscillations is barely perceptible. Design equations are provided, both of the gain of the PSD and of the gain of the MPPT integrator. It also shows how this PSD-MPPT strategy can be combined with the power control, allowing regulation of powers lower than those of the MPP. The power control loop is analyzed, and its stability is related to a single gain to be designed. The PSD-MPPT is tested in a two stage PV inverter, where the step-up DC-DC converter consists of three parallel boost converters. The results show that the PSD-MPPT method can work without the measurement of the current in the boost converters, which implies a cost reduction. A PV efficiency of about 99.8% is obtained with a usual ripple in the DC-bus of 4% peak-peak. In addition, the PSD-MPPT method is characterized as being extremely fast, both in the MPP search and in the power control, with response times around 50 ms. The PSD-MPPT is a simple algorithm of constant parameters that can be solved in a low cost microcontroller at a sampling frequency of about 2 kHz, requiring only the voltage and current of the PV array. Full article

(This article belongs to the Section A2: Solar Energy and Photovoltaic Systems)

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15 pages, 4292 KiB

Open AccessArticle

Data-Driven Compartmental Modeling Method for Harmonic Analysis—A Study of the Electric Arc Furnace

by Haobo Xu, Zhenguo Shao and Feixiong Chen

Energies 2019, 12(22), 4378; https://doi.org/10.3390/en12224378 - 17 Nov 2019

Cited by 6 | Viewed by 2690

Abstract

The electric arc furnace (EAF) contributes to almost one-third of the global iron and steel industry, and its harmonic pollution has drawn attention. An accurate EAF harmonic model is essential to evaluate the harmonic pollution of EAF. In this paper, a data-driven compartmental [...] Read more.

The electric arc furnace (EAF) contributes to almost one-third of the global iron and steel industry, and its harmonic pollution has drawn attention. An accurate EAF harmonic model is essential to evaluate the harmonic pollution of EAF. In this paper, a data-driven compartmental modeling method (DCMM) is proposed for the multi-mode EAF harmonic model. The proposed DCMM considers the coupling relationship among different frequencies of harmonics to enhance the modeling accuracy, meanwhile, the dimensions of the harmonic dataset are reduced to improve computational efficiency. Furthermore, the proposed DCMM is applicable to establish a multi-mode EAF harmonic model by dividing the multi-mode EAF harmonic dataset into several clusters corresponding to the different modes of the EAF smelting process. The performance evaluation results show that the proposed DCMM is adaptive in terms of establishing the multi-mode model, even if the data volumes, number of clusters, and sample distribution change significantly. Finally, a case study of EAF harmonic data is conducted to establish a multi-mode EAF harmonic model, showing that the proposed DCMM is effective and accurate in EAF modeling. Full article

(This article belongs to the Special Issue Power Quality: Monitoring, Mitigation, and New Types of Disturbances)

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14 pages, 7473 KiB

Open AccessArticle

Experimental Investigations on the Inner Flow Behavior of Centrifugal Pumps under Inlet Air-Water Two-Phase Conditions

by Qiaorui Si, Haoyang Zhang, Gérard Bois, Jinfeng Zhang, Qianglei Cui and Shouqi Yuan

Energies 2019, 12(22), 4377; https://doi.org/10.3390/en12224377 - 17 Nov 2019

Cited by 10 | Viewed by 2546

Abstract

Centrifugal pumps are widely used and are known to be sensitive to inlet air-water two-phase flow conditions. The pump performance degradation mainly depends on the changes in the two-phase flow behavior inside the pump. In the present paper, experimental overall pump performance tests [...] Read more.

Centrifugal pumps are widely used and are known to be sensitive to inlet air-water two-phase flow conditions. The pump performance degradation mainly depends on the changes in the two-phase flow behavior inside the pump. In the present paper, experimental overall pump performance tests were performed for two different rotational speeds and several inlet air void fractions (α_i) up to pump shut-off condition. Visualizations were also performed on the flow patterns of a whole impeller passage and the volute tongue area to physically understand pump performance degradation. The results showed that liquid flow modification does not follow head modification as described by affinity laws, which are only valid for homogeneous bubbly flow regimes. Three-dimensional effects were more pronounced when inlet void fraction increased up to 3%. Bubbly flow with low mean velocities were observed close to the volute tongue for all α_i, and returned back to the impeller blade passages. The starting point of pump break down was related to a strong inward reverse flow that occurred in the vicinity of the shroud gap between the impeller and volute tongue area. Full article

(This article belongs to the Special Issue Advancements in Multiphase Fluid Dynamics in Energy and Propulsion Systems)

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12 pages, 4382 KiB

Open AccessArticle

A Combined Multiple Factor Degradation Model and Online Verification for Electric Vehicle Batteries

by Yuan Chen, Yigang He, Zhong Li and Liping Chen

Energies 2019, 12(22), 4376; https://doi.org/10.3390/en12224376 - 17 Nov 2019

Cited by 6 | Viewed by 2518

Abstract

Battery state of health (SOH) is related to the reduction of total capacity due to complicated aging mechanisms known as calendar aging and cycle aging. In this study, a combined multiple factor degradation model was established to predict total capacity fade considering both [...] Read more.

Battery state of health (SOH) is related to the reduction of total capacity due to complicated aging mechanisms known as calendar aging and cycle aging. In this study, a combined multiple factor degradation model was established to predict total capacity fade considering both calendar aging and cycle aging. Multiple factors including temperature, state of charge (SOC), and depth of discharge (DOD) were introduced into the general empirical model to predict capacity fade for electric vehicle batteries. Experiments were carried out under different aging conditions. By fitting the data between multiple factors and model parameters, battery degradation equations related to temperature, SOC, and DOD could be formulated. The combined multiple factor model could be formed based on the battery degradation equations. An online state of health estimation based on the multiple factor model was proposed to verify the correctness of the model. Predictions were in good agreement with experimental data for over 270 days, as the margin of error between the prediction data and the experimental data never exceeded 1%. Full article

(This article belongs to the Special Issue Battery Aging and Life Prediction for Electric Vehicles, Energy Storage Systems and Portable Electronics)

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18 pages, 2104 KiB

Open AccessArticle

The State of Smart Cities in China: The Case of Shenzhen

by Richard Hu

Energies 2019, 12(22), 4375; https://doi.org/10.3390/en12224375 - 17 Nov 2019

Cited by 47 | Viewed by 18273

Abstract

China is at the midpoint of its urbanisation—the largest scale in human history. The recent smart city movement is influencing the discourse and practice of China’s urbanisation, with numerous cities claiming to build smart cities and/or adopting some forms of smart city strategies [...] Read more.

China is at the midpoint of its urbanisation—the largest scale in human history. The recent smart city movement is influencing the discourse and practice of China’s urbanisation, with numerous cities claiming to build smart cities and/or adopting some forms of smart city strategies and initiatives. A so-called ‘latecomer’s advantage’ is being exploited to advance their pursuit for a smart city status, not only to catch up with overseas counterparts, but to overtake them and become international leaders. This local-level enthusiasm strikes a chord with the central government’s strategy of building an ‘innovative nation’ to drive its economic transformation towards a knowledge economy. This converging central-local interest is creating a ‘smart city mania’ across the nation, which, however, has not received due attention in the international literature, and thus deserves critical examination and reflection to inform policy debates. To address this gap, this study investigates the state of smart cities in China, based on a case study of Shenzhen, China’s fastest-growing, experimental city. Shenzhen grew from a fishing village into an international metropolis in 40 years, and has now won a nickname of ‘China’s Silicon Valley’ or ‘China’s smartest city’. This study analyses the state of Chinese smart cities and the pursuit for a smart Shenzhen from the perspectives of the smart city as a concept, as an urban development paradigm, and as an urban regime, drawing upon the international smart city literature. It concludes that a technology-centric approach to smart cities in China, as illustrated by the Shenzhen case, have advanced innovation capacity and economic growth through capitalising on a ‘latecomer’s advantage’. However, this ‘latecomer’s advantage’ may translate into a ‘latecomer’s disadvantage’ for this approach’s lack of institutional adaptation, and for its insufficient attention to social and environmental problems covered under the shiny economic boom. This latecomer’s disadvantage is likely to impact the long-term sustainability of Chinese cities. Full article

(This article belongs to the Special Issue Approaches, Advances and Applications in Sustainable Development of Smart Cities )

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19 pages, 2418 KiB

Open AccessArticle

An Evolutionary Computation Approach for the Online/On-Board Identification of PEM Fuel Cell Impedance Parameters with A Diagnostic Perspective

by Walter Zamboni, Giovanni Petrone, Giovanni Spagnuolo and Davide Beretta

Energies 2019, 12(22), 4374; https://doi.org/10.3390/en12224374 - 17 Nov 2019

Cited by 9 | Viewed by 3068

Abstract

Online/on-board diagnosis would help to improve fuel cell system durability and output power. Therefore, it is a feature the manufacturers may wish to provide for final users to increase the attractiveness of their product. This add-on requires suitable stack models, parametric identification tools [...] Read more.

Online/on-board diagnosis would help to improve fuel cell system durability and output power. Therefore, it is a feature the manufacturers may wish to provide for final users to increase the attractiveness of their product. This add-on requires suitable stack models, parametric identification tools and diagnostic algorithms to be run on low-cost embedded systems, ensuring a good trade-off between accuracy and computation time. In this paper, a computational approach for the impedance parameter identification of polymer electrolyte membrane fuel cell stack is proposed. The method is based on an evolutionary algorithm including sub-population and migration features, which improves the exploration capability of the search space. The goal of the evolutionary algorithm is to find the set of parameters that minimizes an objective function, representing the mismatch between two impedance plots in a normalized plane. The first plot is associated with experimental impedance and the second is computed on the basis of the identified parameters using a circuit model. Three kinds of impedance models, characterized by increasing computational complexity, are used, depending on the experimental data—a linear model made of resistors and capacitors, the Fouquet model and the Dhirde model. Preliminary analysis of the experimental impedance data may evidence correlations among parameters, which can be exploited to reduce the search space of an evolutionary algorithm. The computational approach is validated with literature data in a simulated environment and with experimental data. The results show good accuracy and a computational performance that fits well with the commercial embedded system hardware resources. The implementation of the approach on a low-cost off-the-shelf device achieves small computation times, confirming the suitability of such an approach to online/on-board applications. From a diagnostic perspective, the paper outlines a diagnostic approach based on the identified impedance parameters, on the basis of a small set of experimental data including fuel cell stack faulty conditions. Full article

(This article belongs to the Special Issue Polymer Electrolyte Membrane Fuel Cell Systems)

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11 pages, 2874 KiB

Open AccessArticle

Enhanced Degradation of Pharmaceutical Compounds by a Microbubble Ozonation Process: Effects of Temperature, pH, and Humic Acids

by Yong-Gu Lee, Yongeun Park, Gwanghee Lee, Yeongkwan Kim and Kangmin Chon

Energies 2019, 12(22), 4373; https://doi.org/10.3390/en12224373 - 17 Nov 2019

Cited by 15 | Viewed by 2649

Abstract

This study systematically investigated the feasibility of the microbubble ozonation process to degrade the 17α-ethinylestradiol, ibuprofen, and atenolol through the comparison with the millibubble ozonation process for elucidating the degradation behavior and mechanisms during the microbubble ozonation processes. The proportions of small microbubbles [...] Read more.

This study systematically investigated the feasibility of the microbubble ozonation process to degrade the 17α-ethinylestradiol, ibuprofen, and atenolol through the comparison with the millibubble ozonation process for elucidating the degradation behavior and mechanisms during the microbubble ozonation processes. The proportions of small microbubbles (diameter 1–25 μm) were increased with increasing the cavity pump frequency (40 Hz: 51.4%; 50 Hz: 57.5%; 60 Hz: 59.9%). The increased concentrations of O₃ and OH radicals due to the higher specific area of O₃ microbubbles compared to O₃ millibubbles could facilitate their mass transfer at the gas–water interface. Furthermore, the elevated reactivity of O₃ by increasing the temperature might improve the degradation of the pharmaceutical compounds, which was more pronounced for the microbubble ozonated waters than the millibubble ozonated waters. Although the degradation efficiency of the pharmaceutical compounds during the microbubble ozonation processes was significantly influenced by the existence of humic acids compared to the millibubble ozonation process, the increased solubilization rate of O₃ and OH radicals by collapsing O₃ microbubbles enhanced the degradation of the pharmaceutical compounds. Overall, these results clearly showed that the microbubble ozonation process could be an alternative option to conventional ozonation processes for the abatement of the pharmaceutical compounds. Full article

(This article belongs to the Special Issue Wastewater Treatment and Resource Recovery)

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Energies, Volume 12, Issue 22 (November-2 2019) – 180 articles

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