Special Issue "Sustainable Energy Systems: Optimization and Efficiency"

A special issue of Applied Sciences (ISSN 2076-3417). This special issue belongs to the section "Energy".

Deadline for manuscript submissions: closed (30 September 2019).

Special Issue Editors

Prof. João Carlos de Oliveira Matias
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Guest Editor
GOVCOPP Research Unit; Department of Economics, Management, Industrial Engineering and Tourism (DEGEIT), University of Aveiro, Aveiro, Portugal
Tel. +351 234 370 361 (ext: 23623)
Interests: sustainability; industrial engineering and management; sustainable energy systems; sustainable management systems (quality, maintenance, occupational health and safety); sustainable and lean production; circular economy; technological Innovation
Special Issues and Collections in MDPI journals
Dr. Radu Godina
E-Mail Website1 Website2 Website3
Guest Editor
UNIDEMI - Department of Mechanical and Industrial Engineering, Faculty of Science and Technology (FCT), Universidade NOVA de Lisboa, 2829-516 Caparica, Portugal
Interests: industrial symbiosis; sustainability; circular economy; additive manufacturing; lean manufacturing; quality management systems; sustainable energy systems
Special Issues and Collections in MDPI journals
Dr. Edris Pouresmaeil
E-Mail Website
Guest Editor
Department of Electrical Engineering and Automation, Aalto University, Office 3563, Maarintie 8, 02150 Espoo, Finland
Interests: integration of renewable energy sources into the power grid; power converters and applications of power converters in power systems; dynamic modeling and analysis of power electronic converters and systems; stability analysis of power converters in power system; microgrids operation and control; smart grid systems and technologies
Special Issues and Collections in MDPI journals

Special Issue Information

Dear Colleagues

Renewable energy resources have never been more significant than they are today. As more and more environmental and ecological problems have arisen, the use of renewable resources has become the most important step in addressing and overcoming such challenges. Among the actions that can be taken is the use of renewable energy sources. Renewable sources use natural resources considered inexhaustible because of their ability to regenerate.

One of the most important challenges of present times is energy efficiency related to consumption and use, which encompasses efficiency in energy systems and supply, as well as the demand for final energy. This will maximize the benefits of exploiting the available clean and endogenous primary energy sources. Thus, the technological advances and the new economic framework of the energy sector could guarantee full compliance with environmental constraints.

In the specific field of energy services, notably electricity, a wide and growing range of opportunities regarding energy efficiency are still on the table. The importance of the greater efficiency of the electrical system should be emphasized. Many technologies and solutions for energy efficiency are readily available and economically viable. However, varieties of barriers still obstruct the application of these technologies and prevent them from achieving their potential for greater energy efficiency.

Innovative methods of modelling, which could overcome physical and technical boundary conditions and at the same time take into consideration economic, environmental, and social aspects, could be developed. Therefore, researchers and policy makers are invited to submit their manuscripts to this Special Issue and contribute models, proposals, reviews, and studies.

Prof. Dr. João Carlos de Oliveira Matias
Dr. Radu Godina
Prof. Dr. Edris Pouresmaeil
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Applied Sciences is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1800 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Energy policy
  • Multi-energy systems
  • Thermal energy generation and management
  • Energy life cycle assessment
  • Sustainable energy
  • Energy and circular economy
  • Energy technology
  • Energy markets
  • Power generation and systems
  • Renewable energy
  • Renewable generation forecasting
  • Distributed generation
  • Energy optimization models
  • Energy storage systems
  • Energy efficiency in end-use sectors
  • Electric and hydrogen mobility
  • Building and home energy management
  • Entransy and exergy analyses
  • Fuels
  • Emergy

Published Papers (11 papers)

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Research

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Open AccessFeature PaperArticle
A Simplified Analytical Approach for Optimal Planning of Distributed Generation in Electrical Distribution Networks
Appl. Sci. 2019, 9(24), 5446; https://doi.org/10.3390/app9245446 - 12 Dec 2019
Abstract
DG-integrated distribution system planning is an imperative issue since the installing of distributed generations (DGs) has many effects on the network operation characteristics, which might cause significant impacts on the system performance. One of the most important characteristics that mostly varies because of [...] Read more.
DG-integrated distribution system planning is an imperative issue since the installing of distributed generations (DGs) has many effects on the network operation characteristics, which might cause significant impacts on the system performance. One of the most important characteristics that mostly varies because of the installation of DG units is the power losses. The parameters affecting the value of the power losses are number, location, capacity, and power factor of the DG units. In this paper, a new analytical approach is proposed for optimally installing DGs to minimize power loss in distribution networks. Different parameters of DG are considered and evaluated in order to achieve a high loss reduction in the electrical distribution networks. The algorithm of the proposed approach has been implemented using MATLAB software and has been tested and investigated on 12-bus, 33-bus, and 69-bus IEEE distribution test systems. The results show that the proposed approach can provide an accurate solution via simple algorithm without using exhaustive process of power flow computations. Full article
(This article belongs to the Special Issue Sustainable Energy Systems: Optimization and Efficiency)
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Open AccessArticle
Impact of Recloser on Protecting Blind Areas of Distribution Network in the Presence of Distributed Generation
Appl. Sci. 2019, 9(23), 5092; https://doi.org/10.3390/app9235092 - 25 Nov 2019
Abstract
The protection relay issues increase with the penetration of distributed generation (DG) units in distribution networks. Blind protection, sympathetic tripping and failure of reclosing are the frequent problems that are created by adding DG to the distribution networks. This research focuses on the [...] Read more.
The protection relay issues increase with the penetration of distributed generation (DG) units in distribution networks. Blind protection, sympathetic tripping and failure of reclosing are the frequent problems that are created by adding DG to the distribution networks. This research focuses on the impact of reclosers on overcurrent relay blind protection areas with DGs embedded in the distribution network. The protection blinding in overcurrent relays leads to a delay or non-tripping of the relay. The conventional solution for the blinding issue is to increase the sensitivity in the relay settings. The variation of relay settings may cause problems in the distribution network. This paper investigates the effect of reclosers on eliminating blind areas and improves the reliability in the presence of DG. In this way, possible blind points of the case study are detected, and recloser relays are then installed in appropriate locations. The case study is based on realistic data of a distribution network. The DG consists of two generators with a capacity of 4 MW. The simulation is performed in DIgSILENT software. Full article
(This article belongs to the Special Issue Sustainable Energy Systems: Optimization and Efficiency)
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Open AccessArticle
Thermoeconomic Modelling and Parametric Study of a Simple ORC for the Recovery of Waste Heat in a 2 MW Gas Engine under Different Working Fluids
Appl. Sci. 2019, 9(21), 4526; https://doi.org/10.3390/app9214526 - 25 Oct 2019
Cited by 3
Abstract
This paper presents a thermo-economic analysis of a simple organic Rankine cycle (SORC) as a waste heat recovery (WHR) systems of a 2 MW stationary gas engine evaluating different working fluids. Initially, a systematic methodology was implemented to select three organic fluids according [...] Read more.
This paper presents a thermo-economic analysis of a simple organic Rankine cycle (SORC) as a waste heat recovery (WHR) systems of a 2 MW stationary gas engine evaluating different working fluids. Initially, a systematic methodology was implemented to select three organic fluids according to environmental and safety criteria, as well as critical system operational conditions. Then, thermodynamic, exergy, and exergo-economic models of the system were developed under certain defined considerations, and a set of parametric studies are presented considering key variables of the system such as pump efficiency, turbine efficiency, pinch point condenser, and evaporator. The results show the influence of these variables on the combined power of the system (gas engine plus ORC), ORC exergetic efficiency, specific fuel consumption (∆BSFC), and exergo indicators such as the payback period (PBP), levelized cost of energy (LCOE), and the specific investment cost (SIC). The results revealed that heat transfer equipment had the highest exergy destruction cost rates representing 81.25% of the total system cost. On the other hand, sensitivity analyses showed that acetone presented better energetic and exergetic performance when the efficiency of the turbine, evaporator, and condenser pinch point was increased. However, toluene was the fluid with the best results when pump efficiency was increased. In terms of the cost of exergy destroyed by equipment, the results revealed that acetone was the working fluid that positively impacted cost reduction when pump efficiency was improved; and toluene, when turbine efficiency was increased. Finally, the evaporator and condenser pinch point increased all the economic indicators of the system. In this sense, the working fluid with the best performance in economic terms was acetone, when the efficiency of the turbine, pinch condenser, and pinch evaporator was enhanced. Full article
(This article belongs to the Special Issue Sustainable Energy Systems: Optimization and Efficiency)
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Open AccessArticle
Multi-objective Optimization of Accommodation Capacity for Distributed Generation Based on Mixed Strategy Nash Equilibrium, Considering Distribution Network Flexibility
Appl. Sci. 2019, 9(20), 4395; https://doi.org/10.3390/app9204395 - 17 Oct 2019
Abstract
The increasing penetration of distributed generation (DG) brings about great fluctuation and uncertainty in distribution networks. In order to improve the ability of distribution networks to cope with disturbances caused by uncertainties and to evaluate the maximum accommodation capacity of DG, a multi-objective [...] Read more.
The increasing penetration of distributed generation (DG) brings about great fluctuation and uncertainty in distribution networks. In order to improve the ability of distribution networks to cope with disturbances caused by uncertainties and to evaluate the maximum accommodation capacity of DG, a multi-objective programming method for evaluation of the accommodation capacity of distribution networks for DG is proposed, considering the flexibility of distribution networks in this paper. Firstly, a multi-objective optimization model for determining the maximum accommodation of DG by considering the flexibility of distribution networks is constructed, aiming at maximizing the daily energy consumption, minimizing the voltage amplitude deviation, and maximizing the line capacity margin. Secondly, the comprehensive learning particle swarm optimization (CLPSO) algorithm is used to solve the multi-objective optimization model. Then, the mixed strategy Nash equilibrium is introduced to obtain the frontier solution with the optimal joint equilibrium value in the Pareto solution set. Finally, the effectiveness of the proposed method is demonstrated with an actual distribution network in China. The simulation results show that the proposed planning method can effectively find the Pareto optimal solution set by considering multiple objectives, and can obtain the optimal equilibrium solution for DG accommodation capacity and distribution network flexibility. Full article
(This article belongs to the Special Issue Sustainable Energy Systems: Optimization and Efficiency)
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Open AccessArticle
A Parametric Numerical Study of the Airflow and Thermal Performance in a Real Data Center for Improving Sustainability
Appl. Sci. 2019, 9(18), 3850; https://doi.org/10.3390/app9183850 - 13 Sep 2019
Abstract
In recent years, reducing energy consumption has been relentlessly pursued by researchers and policy makers with the purpose of achieving a more sustainable future. The demand for data storage in data centers has been steadily increasing, leading to an increase in size and [...] Read more.
In recent years, reducing energy consumption has been relentlessly pursued by researchers and policy makers with the purpose of achieving a more sustainable future. The demand for data storage in data centers has been steadily increasing, leading to an increase in size and therefore to consume more energy. Consequently, the reduction of the energy consumption of data center rooms is required and it is with this perspective that this paper is proposed. By using Computational Fluid Dynamics (CFD), it is possible to model a three-dimensional model of the heat transfer and air flow in data centers, which allows forecasting the air speed and temperature range under diverse conditions of operation. In this paper, a CFD study of the thermal performance and airflow in a real data center processing room with 208 racks under different thermal loads and airflow velocities is proposed. The physical-mathematical model relies on the equations of mass, momentum and energy conservation. The fluid in this study is air and it is modeled as an ideal gas with constant properties. The model of the effect of turbulence is made by employing a k–ε standard model. The results indicate that it is possible to reduce the thermal load of the server racks by improving the thermal performance and airflow of the data center room, without affecting the correct operation of the server racks located in the sensible regions of the room. Full article
(This article belongs to the Special Issue Sustainable Energy Systems: Optimization and Efficiency)
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Open AccessFeature PaperArticle
Energy Management of Virtual Power Plant Considering Distributed Generation Sizing and Pricing
Appl. Sci. 2019, 9(14), 2817; https://doi.org/10.3390/app9142817 - 15 Jul 2019
Abstract
The energy management of virtual power plants faces some fundamental challenges that make it complicated compared to conventional power plants, such as uncertainty in production, consumption, energy price, and availability of network components. Continuous monitoring and scaling of network gain status, using smart [...] Read more.
The energy management of virtual power plants faces some fundamental challenges that make it complicated compared to conventional power plants, such as uncertainty in production, consumption, energy price, and availability of network components. Continuous monitoring and scaling of network gain status, using smart grids provides valuable instantaneous information about network conditions such as production, consumption, power lines, and network availability. Therefore, by creating a bidirectional communication between the energy management system and the grid users such as producers or energy applicants, it will afford a suitable platform to develop more efficient vector of the virtual power plant. The paper is treated with optimal sizing of DG units and the price of their electricity sales to achieve security issues and other technical considerations in the system. The ultimate goal in this study to determine the active demand power required to increase system loading capability and to withstand disturbances. The effect of different types of DG units in simulations is considered and then the efficiency of each equipment such as converters, wind turbines, electrolyzers, etc., is achieved to minimize the total operation cost and losses, improve voltage profiles, and address other security issues and reliability. The simulations are done in three cases and compared with HOMER software to validate the ability of proposed model. Full article
(This article belongs to the Special Issue Sustainable Energy Systems: Optimization and Efficiency)
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Open AccessArticle
Incorporating Concentrating Solar Power into High Renewables Penetrated Power System: A Chance-Constrained Stochastic Unit Commitment Analysis
Appl. Sci. 2019, 9(11), 2340; https://doi.org/10.3390/app9112340 - 06 Jun 2019
Cited by 1
Abstract
High renewables penetrated power systems would be greatly influenced by the uncertainty of variable renewable energy such as wind power and photovoltaic power. Unlike wind and photovoltaic plant, concentrating solar power with thermal energy storage has similar dispatchable characteristics as conventional thermal unit. [...] Read more.
High renewables penetrated power systems would be greatly influenced by the uncertainty of variable renewable energy such as wind power and photovoltaic power. Unlike wind and photovoltaic plant, concentrating solar power with thermal energy storage has similar dispatchable characteristics as conventional thermal unit. Besides, thermal energy storage could support the coordinated operation of concentrating solar power with an electrical heater, which can be employed to convert surplus electricity in the grid into thermal power stored in thermal energy storage for further utilization. In this paper, concentrating solar power is incorporated into a chance-constrained two-stage stochastic unit commitment model. The model considers the energy and reserve services of concentrating solar power and the uncertainty of renewables. The proposed method is employed to assess the role of a concentrating solar power station with thermal energy storage and an electrical heater to provide grid flexibility in high renewables penetrated power systems. Numerical studies are performed on a modified IEEE 24-bus system to validate the viability of the proposed method for the day-ahead stochastic scheduling. The results demonstrate the economic and reliable value of concentrating solar power station to the improvement of unit commitment schedule, to the mitigation of wind uncertainty and photovoltaic uncertainty, and to the reduction of traditional unit reserve requirement. It is concluded that concentrating solar power with thermal energy storage and an electrical heater is effective in promoting the further penetration of renewables. Full article
(This article belongs to the Special Issue Sustainable Energy Systems: Optimization and Efficiency)
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Open AccessArticle
The Impact of Demand Response Programs on Reducing the Emissions and Cost of A Neighborhood Home Microgrid
Appl. Sci. 2019, 9(10), 2097; https://doi.org/10.3390/app9102097 - 21 May 2019
Cited by 1
Abstract
The desire to increase energy efficiency and reliability of power grids, along with the need for reducing carbon emissions has led to increasing the utilization of Home Micro-grids (H-MGs). In this context, the issue of economic emission dispatch is worthy of consideration, with [...] Read more.
The desire to increase energy efficiency and reliability of power grids, along with the need for reducing carbon emissions has led to increasing the utilization of Home Micro-grids (H-MGs). In this context, the issue of economic emission dispatch is worthy of consideration, with a view to controlling generation costs and reducing environmental pollution. This paper presents a multi-objective energy management system, with a structure based on demand response (DR) and dynamic pricing (DP). The proposed energy management system (EMS), in addition to decreasing the market clearing price (MCP) and increasing producer profits, has focused on reducing the level of generation units emissions, as well as enhancing utilization of renewable energy units through the DR programs. As a consequence of the nonlinear and discrete nature of the H-MGs, metaheuristic algorithms are applied to find the best possible solution. Moreover, due to the presence of generation units, the Taguchi orthogonal array testing (TOAT) method has been utilized to investigate the uncertainty regarding generation units. In the problem being considered, each H-MG interacts with each other and can negotiate based on their own strategies (reduction of cost or pollution). The obtained results indicate the efficiency of the proposed algorithm, a decrease in emissions and an increase in the profit achieved by each H-MG, by 37% and 10%, respectively. Full article
(This article belongs to the Special Issue Sustainable Energy Systems: Optimization and Efficiency)
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Open AccessArticle
Combustion Characteristics of a Non-Premixed Oxy-Flame Applying a Hybrid Filtered Eulerian Stochastic Field/Flamelet Progress Variable Approach
Appl. Sci. 2019, 9(7), 1320; https://doi.org/10.3390/app9071320 - 29 Mar 2019
Abstract
The oxidation of methane under oxy-fuel combustion conditions with carbon capture is attractive and deserves huge interest towards reducing CO2 and NOx emissions. The current paper reports on the predictions and analysis of combustion characteristics of a turbulent oxy-methane non-premixed flame [...] Read more.
The oxidation of methane under oxy-fuel combustion conditions with carbon capture is attractive and deserves huge interest towards reducing CO2 and NOx emissions. The current paper reports on the predictions and analysis of combustion characteristics of a turbulent oxy-methane non-premixed flame operating under highly diluted conditions of CO2 and H2 in oxidizer and fuel streams, respectively. These are achieved by applying a novel, well-designed numerical combustion model. The latter consists of a large eddy simulation (LES) extension of a recently suggested hybrid model in Reynolds averaging-based numerical simulation (RANS) context by the authors. It combines a transported joint scalar probability density function (T-PDF) following the Eulerian Stochastic Field methodology (ESF) on the one hand, and a flamelet progress variable (FPV) turbulent combustion model under consideration of detailed chemical reaction mechanism on the other hand. This novel hybrid ESF/FPV approach removes the weaknesses of the presumed-probability density function (P-PDF)-based FPV modeling, along with the solving of associated additional modeled transport equations while rendering the T-PDF computationally less affordable. First, the prediction capability of the LES hybrid ESF/FPV was appraised on the well-known air-piloted methane jet flame (Sandia Flame D). Then, it was assessed in analyzing the combustion properties of a non-premixed oxy-flame and in capturing the CO2 dilution effect on the oxy-fuel flame behavior. To this end, the so-called oxy-flame B3, already numerically investigated in a RANS context, was analyzed. Comparisons with experimental data in terms of temperature, scalar distributions, and scatter plots agree satisfactorily. Finally, the impact of generating the FPV chemistry table under condition of unity Lewis number, even with CO2 dilution, was investigated on the general prediction of the oxy-fuel flame structure, stability and emissions. In particular, it turns out that 68% molar percentage of CO2 leads to 0.39% of CO formation near the burner fuel nozzle and 0.62% at 10 dfuel above the nozzle. Full article
(This article belongs to the Special Issue Sustainable Energy Systems: Optimization and Efficiency)
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Open AccessArticle
PV Tracking Design Methodology Based on an Orientation Efficiency Chart
Appl. Sci. 2019, 9(5), 894; https://doi.org/10.3390/app9050894 - 02 Mar 2019
Abstract
This work describes a new photovoltaic (PV) sun tracker design methodology that utilizes the advantages that the orientation and efficiency of the PV panel offer due to the latitude of the installation zone. Furthermore, the proposed design methodology is validated experimentally via the [...] Read more.
This work describes a new photovoltaic (PV) sun tracker design methodology that utilizes the advantages that the orientation and efficiency of the PV panel offer due to the latitude of the installation zone. Furthermore, the proposed design methodology is validated experimentally via the implementation of a solar tracker with dual axes at a specific location (27.5° latitude). In this case, the methodology enables the incorporation of a high-availability, low-accuracy, and low-cost tracking mechanism. Based on the results, the feasibility of this type of solar tracker for latitudes close to 30° is demonstrated, as this tracking system costs 27% less than the traditional commercial systems that use slew drives. This system increases the collection efficiency by 24% with respect to a fixed device. The proposed methodology, which is based on an orientation efficiency chart, can be applied to the construction or control of other types of solar tracker systems. Full article
(This article belongs to the Special Issue Sustainable Energy Systems: Optimization and Efficiency)
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Review

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Open AccessReview
Application of Nanofluids in Thermal Performance Enhancement of Parabolic Trough Solar Collector: State-of-the-Art
Appl. Sci. 2019, 9(3), 463; https://doi.org/10.3390/app9030463 - 29 Jan 2019
Cited by 29
Abstract
The present review paper aims to document the latest developments on the applications of nanofluids as working fluid in parabolic trough collectors (PTCs). The influence of many factors such as nanoparticles and base fluid type as well as volume fraction and size of [...] Read more.
The present review paper aims to document the latest developments on the applications of nanofluids as working fluid in parabolic trough collectors (PTCs). The influence of many factors such as nanoparticles and base fluid type as well as volume fraction and size of nanoparticles on the performance of PTCs has been investigated. The reviewed studies were mainly categorized into three different types of experimental, modeling (semi-analytical), and computational fluid dynamics (CFD). The main focus was to evaluate the effect of nanofluids on thermal efficiency, entropy generation, heat transfer coefficient enhancement, as well as pressure drop in PTCs. It was revealed that nanofluids not only enhance (in most of the cases) the thermal efficiency, convection heat transfer coefficient, and exergy efficiency of the system but also can decrease the entropy generation of the system. The only drawback in application of nanofluids in PTCs was found to be pressure drop increase that can be controlled by optimization in nanoparticles volume fraction and mass flow rate. Full article
(This article belongs to the Special Issue Sustainable Energy Systems: Optimization and Efficiency)
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