bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Heat Demand on Integration of Urban Large-Scale Renewable Schemes—Case of Helsinki City (60 °N)
Authors: Arabzadeh Vahid , Lund Peter D.
Published: May 2020

Heat demand dominates the final energy use in northern cities. This study examines how changes in heat demand may affect solutions for zero-emission energy systems, energy system flexibility with variable renewable electricity production, and the use of existing energy systems for deep decarbonization. Helsinki city (60 °N) in the year 2050 is used as a case for the analysis. The future district heating demand is estimated considering activity-driven factors such as population increase, raising the ambient temperature, and building energy efficiency improvements. The effect of the heat demand on energy system transition is investigated through two scenarios. The BIO-GAS scenario employs emission-free gas technologies, bio-boilers and heat pumps. The WIND scenario is based on large-scale wind power with power-to-heat conversion, heat pumps, and bio-boilers. The BIO-GAS scenario combined with a low heat demand profile (−12% from 2018 level) yields 16% lower yearly costs compared to a business-as-usual higher heat demand. In the WIND-scenario, improving the lower heat demand in 2050 could save the annual system 6–13% in terms of cost, depending on the scale of wind power.
Mathematical Modeling of Heat and Mass Processes in a Scrubber: The Box–Wilson Optimization Method
Authors: Blumberga Dagnija , Priedniece Vivita , Rumba Rūdolfs , Kirsanovs Vladimirs , Ņikitenko Agris , Lavendelis Egons , Veidenbergs Ivars
Published: May 2020

Optimal performance parameters must be found in order to organize efficient heat and mass transfer and effective flue gas cooling using a wet scrubber. Mathematical models are widely used for system optimization. However, a significant number of the available models have application limitations. This study presents a universal model for heat and mass transfer simulation in a scrubber called a fog unit, which has been developed and validated. Validation was performed by comparing the experimental and calculated results. Good agreement was achieved among the data, with differences between results not exceeding 10%. The model facilitates an investigation of the effects of gas flow, droplet size, and sprayed water on heat recovery from flue gas. An experimental matrix for fog unit capacity which included five main variables was designed and analyzed. The boundaries of the parameters are set considering the results of the experiments. The optimization method used is the path of the steepest ascent. The obtained results show the parameter change steps to achieve higher capacity of the condenser. In the studied unit, the maximum condenser capacity is limited by a flue gas flow value of 0.01 Nm3/s. The condenser optimization study that was conducted is viewed as a basis for further studies.
Analysis of the Informational Efficiency of the EU Carbon Emission Trading Market: Asymmetric MF-DFA Approach
Authors: Lee Yun-Jung , Kim Neung-Woo , Choi Ki-Hong , Yoon Seong-Min
Published: May 2020

This study explores the degree and change of informational efficiency of the European Union (EU) carbon emission trading market using an asymmetric multifractal detrended fluctuation analysis (A-MF-DFA) method, which allows asymmetry. For this purpose, we analysed the daily price series of the European Emissions Market, which is operated according to the European Union Emissions Trading Scheme. This carbon market is the most active and has the largest trading volume. The data covers the period (from 4 August 2005 to 31 December 2019). The main results are summarised as follows. First, there is a multifractal feature in the price return movements of the EU carbon trading market, which behaves differently in the upward and downward periods of the market. Second, the informational efficiency of the carbon emission market has changed over time, with Phase I having the lowest informational efficiency and Phase III having the highest informational efficiency. These results indicate that informational efficiency has increased as the carbon emission market matures. Third, from the result of the market deficiency measure (MDM), Phase I showed the lowest market efficiency, whereas Phase III showed the highest efficiency. During Phase III, the MDM values of the upward period were higher than that of the downward period, implying higher market inefficiency during the upward period.
A Multi-Criteria Approach for the Evaluation of Low Risk Restoration Projects in Continuous Surface Lignite Mines
Authors: Spanidis Philip-Mark , Roumpos Christos , Pavloudakis Francis
Published: May 2020

The restoration of continuous surface lignite mines entering the closure phase is a long-term, complex and multidisciplinary project. During the evaluation of alternative restoration technologies, various environmental, technical, economic and social parameters are investigated. In this framework, for the selection of the lower risk restoration alternative, the analysis of the associated risks should be incorporated into the decision-making process. This work provides an overview of practical risk management problems and solutions in mining restoration projects. Moreover, it introduces a multi-criteria methodology for the improvement of the decision-making process in the evaluation of restoration alternatives and the selection of the optimal one, considering a continuous surface mining project. The proposed method is a combination of the analytical hierarchy process (AHP) for the quantification of risk factors and the technique for order of preference by similarity to ideal solution (TOPSIS) for the ranking of restoration alternatives based on a low risk approach. The results of the case study indicate that the proposed approach can be utilized as a low cost and easy-to-apply tool, appropriate for coal mining operators, managers and stakeholders involved in the planning and implementation of post-mining land restoration activities. Furthermore, the suggested methodology could be adopted to support the risk management needs in the restoration stage of complex surface mining projects.
Machine Learning Prediction of Surface Segregation Energies on Low Index Bimetallic Surfaces
Authors: Ologunagba Damilola , Kattel Shyam
Published: May 2020

Surface chemical composition of bimetallic catalysts can differ from the bulk composition because of the segregation of the alloy components. Thus, it is very useful to know how the different components are arranged on the surface of catalysts to gain a fundamental understanding of the catalysis occurring on bimetallic surfaces. First-principles density functional theory (DFT) calculations can provide deeper insight into the surface segregation behavior and help understand the surface composition on bimetallic surfaces. However, the DFT calculations are computationally demanding and require large computing platforms. In this regard, statistical/machine learning methods provide a quick and alternative approach to study materials properties. Here, we trained previously reported surface segregation energies on low index surfaces of bimetallic catalysts using various linear and non-linear statistical methods to find a correlation between surface segregation energies and elemental properties. The results revealed that the surface segregation energies on low index bimetallic surfaces can be predicted using fundamental elemental properties.
Energy Savings Associated with the Use of Fly Ash and Nanoadditives in the Cement Composition
Authors: Golewski Grzegorz Ludwik
Published: May 2020

The paper presented herein investigates the effects of using supplementary cementitious materials (SCMs) in quaternary mixtures on the compressive strength and splitting tensile strength of plain concrete. In addition, environmental benefits resulting from the proposed solutions were analysed. A total of four concrete mixtures were designed, having a constant water/binder ratio of 0.4 and total binder content of 352 kg/m3. The control mixture only contained ordinary Portland cement (OPC) as binder, whereas others incorporated quaternary mixtures of: OPC, fly ash (FA), silica fume (SF), and nanosilica (nS). Based on the obtained test results, it was found that concretes made on quaternary binders containing nanoadditives have very favorable mechanical parameters. The quaternary concrete containing: 80% OPC, 5% FA, 10% SF, and 5% nS have shown the best results in terms of good compressive strength and splitting tensile strength, whereas the worst mechanical parameters were characterized by concrete with more content of FA additive in the concrete mix, i.e., 15%. Moreover, the results of compressive strength and splitting tensile strength are qualitatively convergent. Furthermore, reducing the amount of OPC in the composition of the concrete mix in quaternary concretes causes environmental benefits associated with the reduction of: raw materials that are required for burning clinker, electricity, and heat energy in the production of cement.
Discrete-Ordinates Modelling of the Radiative Heat Transfer in a Pilot-Scale Rotary Kiln
Authors: Gunnarsson Adrian , Andersson Klas , Adams Bradley R. , Fredriksson Christian
Published: May 2020

This paper presents work focused on the development, evaluation and use of a 3D model for investigation of the radiative heat transfer in rotary kilns. The model applies a discrete-ordinates method to solve the radiative transfer equation considering emission, absorption and scattering of radiation by gas species and particles for cylindrical and semi-cylindrical enclosures. Modelling input data on temperature, particle distribution and gas composition in the radial, axial and angular directions are experimentally gathered in a down-scaled version of a rotary kiln. The model is tested in its capability to predict the radiative intensity and heat flux to the inner wall of the furnace and good agreement was found when compared to measurements. Including the conductive heat transfer through the furnace wall, the model also satisfactorily predicts the intermediate wall temperature. The work also includes a first study on the effect of the incident radiative heat flux to the different surfaces while adding a cold bed material. With further development of the model, it can be used to study the heat transfer in full-scale rotary kilns.
Copper Coordination Complexes for Energy-Relevant Applications
Authors: Benesperi Iacopo , Singh Reena , Freitag Marina
Published: May 2020

Copper coordination complexes have emerged as a group of transition metal complexes that play important roles in solar energy conversion, utilization and storage, and have the potential to replace the quintessential commonly used transition metals, like Co, Pt, Ir and Ru as light sensitizers, redox mediators, electron donors and catalytic centers. The applications of copper coordination compounds in chemistry and energy related technologies are many and demonstrate their rightful place as sustainable, low toxicity and Earth-abundant alternative materials. In this perspective we show the most recent impact made by copper coordination complexes in dye-sensitized solar cells and other energy relevant applications.
FEM Applied to Building Physics: Modeling Solar Radiation and Heat Transfer of PCM Enhanced Test Cells
Authors: Vaz Sá Ana , Azenha Miguel , Guimarães A.S. , Delgado J.M.P.Q.
Published: May 2020

In passive solar buildings, energy can be stored using either sensible heat materials or latent heat materials. Phase change materials (PCM) can contribute to temperature control in passive solar buildings when melting occurs near to comfort temperature required for building’s interior spaces. The use of finite element method (FEM) as a numerical methodology for solving the thermal problem associated with heat transfer in current building materials and PCMs make sense, as it is a well-known technique, generalized and dominated, however, still little applied to the domain of building physics. In this work, a solar model was developed and applied in order to simulate numerically the effect of solar radiation incidence on each face of the test cells (with different solar exposures) without neglecting the main objective of the recommended numerical simulation: the study of the action of PCM. During the experimental campaign, two test cells with distinct inner layers were used to evaluate the effect of solar radiation: (i) REFM test cell (without PCM) with a reference mortar; (ii) PCMM test cell (with PCM) with a PCM mortar. The temperatures monitored inside the REFM and PCMM test cells were compared with the values resulting from the numerical simulation, using FEM with 3D discretization and the explicit modeling of the solar radiation, and the obtained results revealed a significant coherence of values.
Assessing the Dynamic Performance of Thermochemical Storage Materials
Authors: Walsh Sara , Reynolds Jack , Abbas Bahaa , Woods Rachel , Searle Justin , Jewell Eifion , Elvins Jonathon
Published: May 2020

Thermochemical storage provides a volumetric and cost-efficient means of collecting energy from solar/waste heat in order to utilize it for space heating in another location. Equally important to the storage density, the dynamic thermal response dictates the power available which is critical to meet the varied demands of a practical space heating application. Using a laboratory scale reactor (127 cm3), an experimental study with salt in matrix (SIM) materials found that the reactor power response is primarily governed by the flow rate of moist air through the reactor and that creating salt with a higher salt fraction had minimal impact on the thermal response. The flowrate dictates the power profile of the reactor with an optimum value which balances moisture reactant delivery and reaction rate on the SIM. A mixed particle size produced the highest power (22 W) and peak thermal uplift (32 °C). A narrow particle range reduced the peak power and peak temperature as a result of lower packing densities of the SIM in the reactor. The scaled maximum power density which could be achieved is >150 kW/m3, but achieving this would require optimization of the solid–moist air interactions.
Performance Evaluation of PV/T Air Collector Having a Single-Pass Double-Flow Air Channel and Non-Uniform Cross-Section Transverse Rib
Authors: Choi Hwi-Ung , Choi Kwang-Hwan
Published: May 2020

In the present work, the electrical and thermal performances of a newly designed PV/T (photovoltaic/thermal) air collector, which was proposed and fabricated by the author, have been investigated experimentally in the natural weather conditions. The PV/T air collector has a single-pass double-flow air channel. Also, a non-uniform cross-section transverse rib was attached at the back surface of the PV (photovoltaic) module to improve the heat transfer performance between the PV module and flowing air. The experiment was carried out in an outdoor field on a clear day with various air mass flow rates ranges from 0.0198 kg/s to 0.07698 kg/s. In the results, it was found that the average thermal efficiency of the PV/T collector increased from 35.2% to 56.72% as the air mass flow rate increased. The average electrical efficiency also increased from 14.23% to 14.81% with an increase in an air mass flow rate, but the effect of air mass flow rate on the increase in electrical efficiency was inconsiderable. The average overall efficiency, which represents the sum of electrical and thermal efficiencies, was in the range of 49.44% to 71.54% and it increased as the air mass flow rate increased. The maximum value of average overall efficiency during the test period was found to be 71.54% at an air mass flow rate of 0.07698 kg/s. From the results, it was confirmed that the newly designed PV/T air collector provides a significant enhancement in solar energy utilization.
Dual-Inverter-Controlled Brushless Operation of Wound Rotor Synchronous Machines Based on an Open-Winding Pattern
Authors: Bukhari Syed Sabir Hussain , Sirewal Ghulam Jawad , Chachar Faheem Akhtar , Ro Jong-Suk
Published: May 2020

In an open-winding machine, three-phase stator currents can be controlled such that the input armature currents may contain the third-harmonic current component in addition to the fundamental. Considering this attribute of open-winding patterns, a harmonic current field excitation technique for a wound rotor synchronous machine (WRSM) is proposed in this paper based on the control of time-harmonic magneto-motive force. Two inverters connected to both terminals of the stator winding are controlled so that the input armature current generates an additional third-harmonic current component. This third-harmonic component generates a vibrating magnetic field that induces a current in the specially designed rotor harmonic winding. The current is supplied as DC current to the rotor excitation winding to generate a rotor field by using a full-bridge diode rectifier in order to achieve brushless operation. The proposed dual-inverter-controlled brushless operation for a WRSM is executed in ANSYS Maxwell using 2-D finite element analysis to validate its operation and electromagnetic performance.
A Prospective Net Energy and Environmental Life-Cycle Assessment of the UK Electricity Grid
Authors: Raugei Marco , Kamran Mashael , Hutchinson Allan
Published: May 2020

National Grid, the UK’s largest utility company, has produced a number of energy transition scenarios, among which “2 degrees” is the most aggressive in terms of decarbonization. This paper presents the results of a combined prospective net energy and environmental life cycle assessment of the UK electricity grid, based on such a scenario. The main findings are that the strategy is effective at drastically reducing greenhouse gas emissions (albeit to a reduced degree with respect to the projected share of “zero carbon” generation taken at face value), but it entails a trade-off in terms of depletion of metal resources. The grid’s potential toxicity impacts are also expected to remain substantially undiminished with respect to the present. Overall, the analysis indicates that the “2 degrees” scenario is environmentally sound and that it even leads to a modest increase in the net energy delivered to society by the grid (after accounting for the energy investments required to deploy all technologies).
Scheduled Pre-Heating of Li-Ion Battery Packs for Balanced Temperature and State-of-Charge Distribution
Authors: Vu Hien , Shin Donghwa
Published: May 2020

Lithium-ion batteries exhibit significant performance degradation such as power/energy capacity loss and life cycle reduction in low-temperature conditions. Hence, the Li-ion battery pack is heated before usage to enhance its performance and lifetime. Recently, many internal heating methods have been proposed to provide fast and efficient pre-heating. However, the proposed methods only consider a combination of unit cells while the internal heating should be implemented for multiple groups within a battery pack. In this study, we investigated the possibility of timing control to simultaneously obtain balanced temperature and state of charge (SOC) between each cell by considering geometrical and thermal characteristics of the battery pack. The proposed method schedules the order and timing of the charge/discharge period for geometrical groups in a battery pack during internal pre-heating. We performed a pack-level simulation with realistic electro-thermal parameters of the unit battery cells by using the mutual pulse heating strategy for multi-layer geometry to acquire the highest heating efficiency. The simulation results for heating from −30 ∘ C to 10 ∘ C indicated that a balanced temperature-SOC status can be achieved via the proposed method. The temperature difference can be decreased to 0.38 ∘ C and 0.19% of the SOC difference in a heating range of 40 ∘ C with only a maximum SOC loss of 2.71% at the end of pre-heating.
Ship Emission Mitigation Strategies Choice Under Uncertainty
Authors: Yuan Jun , Wang Haowei , Ng Szu Hui , Nian Victor
Published: May 2020

Various mitigation strategies have been proposed to reduce the CO2 emissions from ships, which have become a major contributor to global emissions. The fuel consumption under different mitigation strategies can be evaluated based on two data sources, real data from the real ship systems and simulated data from the simulation models. In practice, the uncertainties in the obtained data may have non-negligible impacts on the evaluation of mitigation strategies. In this paper, a Gaussian process metamodel-based approach is proposed to evaluate the ship fuel consumption under different mitigation strategies. The proposed method not only can incorporate different data sources but also consider the uncertainties in the data to obtain a more reliable evaluation. A cost-effectiveness analysis based on the fuel consumption prediction is then applied to rank the mitigation strategies under uncertainty. The accuracy and efficiency of the proposed method is illustrated in a chemical tanker case study, and the results indicate that it is critical to consider the uncertainty, as they can lead to suboptimal decisions when ignored. Here, trim optimisation is ranked more effective than draft optimisation when the uncertainty is ignored, but the reverse is the case when the uncertainty in the estimations are fully accounted for.
The Effect of Morphology on Solar Potential of High-Density Residential Area: A Case Study of Shanghai
Authors: Zhu Dan , Song Dexuan , Shi Jie , Fang Jia , Zhou Yili
Published: May 2020

This study explores the relationship between the morphology and solar potential of high-density areas in the subtropics high density city known as Shanghai. 1260 parametric scenarios were modeled and their solar irradiation potentials were simulated via a customized workflow. In addition to the five well-known morphological parameters, this study proposed two innovative morphological parameters SSU600 and SSU400, which captured the solar receiving properties of the building envelopes and could be easily calculated based on the meteorological data. For analytical purposes, the previously morphological parameters were considered as independent variables, whereas the new solar performance indicators SRU600 and SRU400 were both examined as dependent variables. The correlation analysis results suggested that the new morphological parameters displayed a strong linear correlation with the corresponding solar performance indicators, surpassing all the other morphological parameters. Two prediction models with respect to SRU600 and SRU400 were developed by multiple linear regressions using a stepwise method and their validity was verified by real residential cases. The findings provide key morphological parameters and rapid calculation tools for establishing solar energy friendly urban planning and design.
The Application of Molten Salt Energy Storage to Advance the Transition from Coal to Green Energy Power Systems
Authors: Kosman Wojciech , Rusin Andrzej
Published: May 2020

The paper presents technical solutions for a power grid that undergoes the elimination of a significant number of coal-based power generating units. The purpose of the solutions is to adapt the existing machines with sufficient lifespans to the new operating conditions. In particular these include steam turbines. The steam turbines’ cycles may be extended with energy storage systems based on a molten salt. This allows to increase the flexibility of the power generating units while maintaining the largest possible efficiency of the power generation. The solutions presented here allow to connect the steam turbines cycles to renewable energy sources and reduce the overall number of the units that create the fundamental layer of the power grid. The analysis of the solutions involves numerical modeling. The paper describes the assumptions and the results of the modeling for chosen cases of the modernization. The researched considered a number of options that differed in the investment costs and the resulting performance.
Managing Power Demand from Air Conditioning Benefits Solar PV in India Scenarios for 2040
Authors: Ershad Ahmad Murtaza , Pietzcker Robert , Ueckerdt Falko , Luderer Gunnar
Published: May 2020

An Indian electricity system with very high shares of solar photovoltaics seems to be a plausible future given the ever-falling solar photovoltaic (PV) costs, recent Indian auction prices, and governmental support schemes. However, the variability of solar PV electricity, i.e., the seasonal, daily, and other weather-induced variations, could create an economic barrier. In this paper, we analyzed a strategy to overcome this barrier with demand-side management (DSM) by lending flexibility to the rapidly increasing electricity demand for air conditioning through either precooling or chilled water storage. With an open-source power sector model, we estimated the endogenous investments into and the hourly dispatching of these demand-side options for a broad range of potential PV shares in the Indian power system in 2040. We found that both options reduce the challenges of variability by shifting electricity demand from the evening peak to midday, thereby reducing the temporal mismatch of demand and solar PV supply profiles. This increases the economic value of solar PV, especially at shares above 40%, the level at which the economic value roughly doubles through demand flexibility. Consequently, DSM increases the competitive and cost-optimal solar PV generation share from 33–45% (without DSM) to ~45–60% (with DSM). These insights are transferable to most countries with high solar irradiation in warm climate zones, which amounts to a major share of future electricity demand. This suggests that technologies, which give flexibility to air conditioning demand, can be an important contribution toward enabling a solar-centered global electricity supply.
Study of Heat Transfer and the Hydrodynamic Performance of Gas–Solid Heat Transfer in a Vertical Sinter Cooling Bed Using the CFD-Taguchi-Grey Relational Analysis Method
Authors: Fu Junpeng , Cai Jiuju
Published: May 2020

The vertical sinter cooling bed (VSCB) is a high-efficiency energy-saving and environmentally friendly waste heat recovery equipment. In this study, a computational fluid dynamics (CFD) convection model was established to reveal the typical factors on the thermodynamic performance in VSCB. Indeed, a multiple performance optimal algorithm based on the Taguchi-grey relational analysis (GRA) method was first applied to investigate the effects of geometric and operational factors, including the diameter of the bed, height of the bed, air mass flow rate, air inlet temperature, and sinter mass flow rate, on improving the heat transfer (Ex) and hydrodynamic performance (Pdrop) and obtain the optimum combination of each factor in VSCB. The results found that the diameter of the bed was the most influential factor contributing the multiple types of performance with a contribution rate of 70.51%, followed by the air mass flow rate (15.84%), while the height of the bed (0.27%) exerted a limited effect on the performance of multiple processes. The optimal combination of factors (A1B5C5D5E1) was compared with the initially selected parameters by performing a confirmation test. The performances of heat transfer and hydrodynamics were improved by the Taguchi with the GRA method.
Effects of Concentration Variations on the Performance and Microbial Community in Microbial Fuel Cell Using Swine Wastewater
Authors: Ni Hongjun , Wang Kaixuan , Lv Shuaishuai , Wang Xingxing , Zhuo Lu , Zhang Jiaqiao
Published: May 2020

The variation of substrate concentration in anode chamber directly affects the power generation efficiency and decontamination performance of microbial fuel cell (MFC). In this study, three concentrations of swine wastewater with 800 mg/L, 1600 mg/L and 2500 mg/L were selected as substrates, and the performance of MFC and response characteristics of anode microbial community were investigated. The results show that the concentration of a selected substrate is positively correlated with the output voltage of MFC and chemical oxygen demand (COD) removal rate. The microbial community diversity in the anode chamber and the performance of battery can be significantly affected when concentration changes in different ways, which helps to selectively cultivate the adaptable dominant bacteria to enhance the stability and decontamination performance of MFC. The community structure of anodic biofilm is mainly composed of Proteobacteria, Bacteroidetes, Firmicutes, Chloroflexi and Spirochaetae. These findings are meaningful to improve the treatment effects of swine wastewater and can help to find out the mechanism of varying concentration that influences the production of microorganisms in MFC.
The Role of Biorefinery Co-Products, Market Proximity and Feedstock Environmental Footprint in Meeting Biofuel Policy Goals for Winter Barley-to-Ethanol
Authors: Spatari Sabrina , Stadel Alexander , Adler Paul R. , Kar Saurajyoti , Parton William J. , Hicks Kevin B. , McAloon Andrew J. , Gurian Patrick L.
Published: May 2020

Renewable fuel standards for biofuels have been written into policy in the U.S. to reduce the greenhouse gas (GHG) intensity of transportation energy supply. Biofuel feedstocks sourced from within a regional market have the potential to also address sustainability goals. The U.S. Mid-Atlantic region could meet the advanced fuel designation specified in the Renewable Fuel Standard (RFS2), which requires a 50% reduction in GHG emissions relative to a gasoline baseline fuel, through ethanol produced from winter barley (Hordeum vulgare L.). We estimate technology configurations and winter barley grown on available winter fallow agricultural land in six Mid-Atlantic states. Using spatially weighted stochastic GHG emission estimates for winter barley supply from 374 counties and biorefinery data from a commercial dry-grind facility design with multiple co-products, we conclude that winter barley would meet RFS2 goals even with the U.S. EPA’s indirect land use change estimates. Using a conservative threshold for soil GHG emissions sourced from barley produced on winter fallow lands in the U.S. MidAtlantic, a biorefinery located near densely populated metropolitan areas in the Eastern U.S. seaboard could economically meet the requirements of an advanced biofuel with the co-production of CO2 for the soft drink industry.
High Aperture Efficiency Array Antenna for Wireless Power Transfer Applications
Authors: Kang Eunjung , Hur Jun , Seo Chulhun , Lee Hojin , Choo Hosung
Published: May 2020

We propose a novel array antenna with high aperture efficiency by employing an array element operating in a high-order mode to improve the transmission efficiency of wireless power transmission applications. The proposed array element, operating at a frequency of 5.8 GHz, consists of a square patch with four metallic shorting pins, an extended cavity, and a high dielectric superstrate. The four metallic shorting pins derive the high-order operation, which can enhance the bore-sight gain, resulting in the high aperture efficiency of the array. The extended cavity structure can help further improvement the aperture efficiency and minimize the mutual coupling strength between adjacent elements. The proposed antenna element is extended to 2 × 2 and 4 × 4 arrays, resulting in aperture efficiencies of 74.2% and 80.5%, respectively. For the 2 × 2 array, maximum measured gains of 19.9 dBi in the zx-plane and 18.8 dBi in the zy-plane are observed. For the 4 × 4 array, the maximum measured gains of 24.3 dBi in the zx-plane and 24.5 dBi in the zy-plane are obtained in a full-anechoic chamber. Finally, the transmission efficiency of 6% with a distance of 0.8 m between the transmitter (Tx) and the receiver (Rx) is measured when setting up the wireless power transfer system, which consists of the Tx with the proposed 4 × 4 array and the Rx with a single element.
Synergies and Trade-Offs Between Sustainable Development and Energy Performance of Exterior Lighting
Authors: Jägerbrand Annika K.
Published: May 2020

The aim of this review was to map synergies and trade-offs between sustainable development and energy efficiency and savings regarding exterior lighting. Exterior lighting, such as public road and street lighting, requires significant amounts of energy and hinders sustainable development through its increasing of light pollution, ecological impact, and global climate change. Interlinkages between indicators in sustainability and energy that have positive interactions will lead to a mutual reinforcement in the decision-making process, and vice versa, interlinkages between trade-offs may lead to unwanted and conflicting effects. Very few studies have presented a clear vision of how exterior lighting should be contributing to, and not counteracting, the sustainable development of our planet. This study was conducted through a theoretical and systematic analysis that examined the interactions between sustainable development and energy performance based on a framework using indicators and variables, and by reviewing the current literature. Additionally, 17 indicators of energy efficiency and energy savings were identified and used in the analysis. Most interactions between variables for sustainable development and energy performance (52%) were found to be synergistic. The synergistic interactions were mostly found (71%) in the ecological and environmental dimension showing that environmental and ecological sustainability goes hand in hand with energy efficiency and savings. Trade-offs were found only in the economic and social dimensions accounting for 18% of the interactions identified. This review shows that the interactions between sustainable development and energy performance can be used to establish more efficient policies for decision-making processes regarding exterior lighting.
Adapt or Perish: A New Approach for Industry Needs-Driven Master’s Level Low-Carbon Energy Engineering Education in the UK
Authors: Rowley Paul , Walker Caroline
Published: May 2020

This paper describes the results of recent research carried out with the UK energy sector to assess low-carbon related skills gaps and training requirements at the masters-level. Via iterative engagement across the industry, the characteristics of the market for new ‘needs-driven’ industry-focussed masters-level training offerings were defined. The results, taken together with the outcomes of a gap analysis of existing masters-level training, support the creation of a new framework for masters-level energy education that will more effectively meet the growing unmet need for such skills in the UK and beyond. The outcomes of the research indicate that flexibility in both delivery mode and curriculum content across both technical and non-technical disciplines is essential, along with improved supplier agility to rapidly develop new courses in evolving engineering specialisations. Without responding effectively to such demands from industry, we conclude that the advanced skills needed across the highly dynamic UK and global energy engineering sector will be in increasingly short supply.
Study of How Photoelectrodes Modified by TiO2/Ag Nanofibers in Various Structures Enhance the Efficiency of Dye-Sensitized Solar Cells under Low Illumination
Authors: Nien Yu-Hsun , Chen Huang-Hua , Hsu Hui-Hsuan , Rangasamy Manjunath , Hu Geng-Ming , Yong Zhen-Rong , Kuo Po-Yu , Chou Jung-Chuan , Lai Chih-Hsien , Ko Cheng-Chu , Chang Jun-Xiang
Published: May 2020

Dye-sensitized solar cells (DSSCs) are low-cost solar cells belonging to the thin-film photovoltaic cell type. In this study, we studied the photovoltaic performances of DSSCs based on titanium dioxide (TiO2) nanofibers (NFs) containing silver (Ag) nanoparticles (NPs) under low illumination. We used the sol-gel method with the electrospinning technique to prepare the TiO2 NFs containing Ag NPs. Herein, we used two ways to add TiO2/Ag NFs to modify the photoelectrode successfully and enhance the performance of DSSCs. One way was that the TiO2/Ag NFs were mixed with pristine TiO2; the other way was that the TiO2/Ag NFs were seeded beside the TiO2 colloid layer as an additional layer on the photoelectrode of the DSSC. According to this experiment, the photovoltaic conversion efficiency of the DSSC which had TiO2/Ag NF seeded as an additional layer on the photoelectrode (5.13%) was increased by 28% compared to the DSSC without the photoelectrode modification (3.99%). This was due to the suppression of electron recombination and the more effective utilization of the light radiation by adding the TiO2/Ag NFs. Because of the good conductivity of Ag, the electrons were quickly transported and electron recombination was reduced. In addition, the photovoltaic conversion efficiency of the DSSC which had TiO2/Ag NF seeded as an additional layer on the photoelectrode increased from 5.13% to 6.23% during the decrease in illumination from 100 mW/cm2 to 30 mW/cm2; however, its photovoltaic conversion efficiency decreased to 5.31% when the illumination was lowered to 10 mW/cm2.
Electricity Portfolio Optimization for Large Consumers: Iberian Electricity Market Case Study
Authors: Canelas Emanuel , Pinto-Varela Tânia , Sawik Bartosz
Published: May 2020

Electricity markets are nowadays flooded with uncertainties that rise from renewable energy applications, technological development, and fossil fuel prices fluctuation, among others. These aspects result in a lumpy electricity prices for consumers, making it necessary to come up with risk management tools to help them hedge this associated risk. In this work a portfolio optimization applied to electricity sector, is proposed. A mixed integer programming model is presented to characterize the electricity portfolio of large consumers. The energy sources available for the portfolio characterization are the day-ahead spot market, forward contracts, and self-generation. The study novelty highlights the energy portfolio characterization for players denoted as large consumers, which has been overlooked by the scientific community and, focuses on the Iberian electricity market as a real case study. A multi-objective methodology is explored, using a weighted-sum approach. The expected cost and the conditional value-at-risk (CVaR) minimization are used as objective function. Three case studies illustrate the model applicability through the characterization of how the portfolio evolves with different demand profiles and how to take advantage from seasonality characteristic in the spot market. A scenario analysis is explored to reflect the uncertainty on the price of the spot market. The expected cost and CVaR are optimized for each case study and the portfolio analysis for each risk posture is characterized. The results illustrate the advantage to reduce costs and risk if the prices seasonality is considered, triggering to an adaptive seasonal behavior, which support the decision-maker decision towards its goals.
Environmental Assessment of a Coal Power Plant with Carbon Dioxide Capture System Based on the Activated Carbon Adsorption Process: A Case Study of the Czech Republic
Authors: Zakuciová Kristína , Štefanica Jiří , Carvalho Ana , Kočí Vladimír
Published: May 2020

The Czech Republic is introducing new technological concepts for mitigation of greenhouse gases (GHG) in coal-based energy industries. One such technology, in power plants, is post combustion CO2 capture from flue gases by activated carbon adsorption. A life cycle assessment (LCA) was used as the assessment tool to determine the environmental impacts of the chosen technology. This article focuses on a comparative LCA case study on the technology of temperature-swing adsorption of CO2 from power plant flue gases, designed for the conditions of the Czech Republic. The LCA study compares the following two alternatives: (1) a reference power unit and (2) a reference power unit with CO2 adsorption. The most significant changes are observed in the categories of climate change potential, terrestrial acidification, and particulate matter formation. The adsorption process shows rather low environmental impacts, however, the extended LCA approach shows an increase in energy demands for the process and fossil depletion as a result of coal-based national energy mix. The feasibility of the study is completed by the preliminary economical calculation of the payback period for a commercial carbon capture unit.
How Is Mortality Affected by Fossil Fuel Consumption, CO2 Emissions and Economic Factors in CIS Region?
Authors: Rasoulinezhad Ehsan , Taghizadeh-Hesary Farhad , Taghizadeh-Hesary Farzad
Published: May 2020

It is widely discussed that GDP growth has a vague impact on environmental pollution due to carbon dioxide emissions from fossil fuels consumed in production, transportation, and power generation. The main purpose of this study is to investigate the relationships between economic growth, fossil fuel consumption, mortality (from cardiovascular disease (CVD), diabetes mellitus (DM), cancer, and chronic respiratory disease (CRD), and environmental pollution since environmental pollution can be a reason for societal mortality rate increases. This study uses the generalized method of moments (GMM) estimation technique for the Commonwealth of Independent States (CIS) members for the period from 1993–2018. The major results revealed that the highest variability of mortality could be explained by CO2 variability. Regarding fossil fuel consumption, the estimation proved that this variable positively affects mortality from CVD, DM, cancer, and CRD. Additionally, any improvements in the human development index (HDI) have a negative effect on mortality increases from CVD, DM, cancer, and CRD in the CIS region. It is recommended that the CIS members implement different policies to improve energy transitions, indicating movement from fossil fuel energy sources to renewable sources. Moreover, we recommend the CIS members enhance various policies for easy access to electricity from green sources and increase the renewable supply through improved technologies, sustainable economic growth, and increase the use of green sources in daily social life.
A Frequency Estimation Method Based on a Revised 3-Level Discrete Fourier Transform with an Estimation Delay Reduction Technique
Authors: Kang Sang-Hee , Seo Woo-Seok , Nam Soon-Ryul
Published: May 2020

In this paper, a frequency estimation method based on a revised three-level discrete Fourier transform (DFT) with an estimation delay reduction technique is proposed. First, the input signal passes through a sine filter twice to improve the ability to decrease the level of harmonics and inter-harmonics. Secondly, the second sine-filtered signal is decomposed into two orthogonal components by DFT with a hamming window to enhance the ability to suppress inter-harmonics. The frequency of the signal is derived using orthogonal components without a zero-crossing problem, which can cause numerical estimation error. This process causes the estimation delay of three cycles and three samples in total. Therefore, the estimation delay reduction technique compensating for the phase delay of the phasor is proposed. To evaluate the performance of the proposed method, several frequency changes were considered when the test signals were generated according to the IEEE PMU Standards C37.118.1a-2014. The performance of the proposed method was also evaluated under dynamic and fault conditions in a five-bus transmission system modeled with PSCAD/EMTDC. The simulation results show that the proposed method accurately estimated the frequency of the signal.
A Comparative Techno-Economic Analysis of Different Desalination Technologies in Off-Grid Islands
Authors: Castro Michael , Alcanzare Myron , Esparcia Eugene , Ocon Joey
Published: May 2020

Freshwater in off-grid islands is sourced from rain, groundwater, or mainland imports, which are unreliable, limited, and expensive, respectively. Sustainable freshwater generation from desalination of abundant seawater is another alternative worth exploring. Model-based techno-economic simulations have focused on reverse osmosis desalination due to its low energy consumption and decreasing costs. However, reverse osmosis requires frequent and costly membrane replacement. Other desalination technologies have advantages such as less stringent feedwater requirements, but detailed studies are yet to be done. In this work, a techno-economic comparison of multi-effect distillation, multi-stage flash, mechanical vapor compression, and reverse osmosis coupled with solar photovoltaic-lithium ion-diesel hybrid system was performed by comparing power flows to study the interaction between energy and desalination components. Optimization with projected costs were then performed to investigate future trends. Lastly, we used stochastic generation and demand profiles to infer uncertainties in energy and desalination unit sizing. Reverse osmosis is favorable due to low energy and water costs, as well as possible compatibility with renewable energy systems. Multi-effect distillation and multi-stage flash may also be advantageous for low-risk applications due to system robustness.
Determination of Various Parameters during Thermal and Biological Pretreatment of Waste Materials
Authors: Hren Robert , Petrovič Aleksandra , Čuček Lidija , Simonič Marjana
Published: May 2020

Pretreatment of waste materials could help in more efficient waste management. Various pretreatment methods exist, each one having its own advantages and disadvantages. Moreover, a certain pretreatment technique might be efficient and economical for one feedstock while not for another. Thus, it is important to analyze how parameters change during pretreatment. In this study, two different pretreatment techniques were applied: thermal at lower and higher temperatures (38.6 °C and 80 °C) and biological, using cattle rumen fluid at ruminal temperature (≈38.6 °C). Two different feedstock materials were chosen: sewage sludge and riverbank grass (Typha latifolia), and their combinations (in a ratio of 1:1) were also analyzed. Various parameters were analyzed in the liquid phase before and after pretreatment, and in the gas phase after pretreatment. In the liquid phase, some of the parameters that are relevant to water quality were measured, while in the gas phase composition of biogas was measured. The results showed that most of the parameters significantly changed during pretreatments and that lower temperature thermal and/or biological treatment of grass and sludge is suggested for further applications.
An MPC Approach for Grid-Forming Inverters: Theory and Experiment
Authors: Labella Alessandro , Filipovic Filip , Petronijevic Milutin , Bonfiglio Andrea , Procopio Renato
Published: May 2020

Microgrids (MGs) interest is growing very fast due to the environment urgency and their capability to integrate renewable energy in a flexible way. In particular, islanded MGs in which distributed energy resources (DERs) are connected to the infrastructure with power electronic converters have attracted the interest of many researchers of both academia and industry because management, control and protection of such systems is quite different from the case of traditional networks. According to their operation mode, MGs that power electronic converters can be divided into grid-forming, grid-feeding and grid-supporting inverters. In particular, grid forming inverters are asked to impose voltage and frequency in the MG. This paper aims to propose a model predictive control (MPC) based approach for grid-forming inverters in an islanded MG. The MPC strategy is implemented because of its capability to define the optimal control actions that contemporarily track the desired reference signals and accounts for equality and inequality constraints. The overall problem formulation (objective function and relevant constraints) is described step by step and considers the specificity of the considered DC source. The proposed approach allows for the obtaining of very good results in terms of readiness against disturbances, even if it requires being fed only by local measurements. In order to validate the developed method, this paper proposes an experimental validation of the designed MPC controller in order to show its correct operation on a real system in a power hardware in the loop set-up using a rapid control prototyping approach.