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Challenges Towards Sustainable Energy

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A special issue of Energies (ISSN 1996-1073). This special issue belongs to the section "A: Sustainable Energy".

Deadline for manuscript submissions: closed (31 July 2020) | Viewed by 21763

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Special Issue Editors

Prof. Dr. Carlos Felgueiras

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Center for Innovation in Engineering and Industrial Technology (CIETI) and School of Engineering (ISEP), Polytechnic of Porto (P.PORTO), R. Dr. António Bernardino de Almeida 431, 4249-015 Porto, Portugal
Interests: energy quality; energy and buildings; energy and environmental indicators; renewable energy systems; sustainable energy systems; engineering education
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Prof. Dr. Zita Vale

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GECAD-Research Group on Intelligent Engineering and Computing for Advanced Innovation and Development, Polytechnic of Porto (P.PORTO), P-4200-465 Porto, Portugal
Interests: artificial intelligence; demand response; electric vehicles; electricity markets; power and energy systems; renewable and sustainable energy; smart grids
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Prof. Dr. Coriolano Salvini

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Department of Engineering, University of Roma Tre, Via della Vasca Navale, 79, 00146 Rome, Italy
Interests: renewable energy technologies; engineering thermodynamics; thermal engineering; power generation
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Prof. Dr. Luís Tarelho

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Department of Environment and Planning, University of Aveiro, 3810 Aveiro, Portugal
Interests: thermochemical conversion processes; biochar production; fluidized bed reactors engineering; solid waste treatment technology; treatment of gaseous emissions; environmental impact of energy conversion processes
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Dr. Marta Ferreira Dias

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Research Unit on Governance, Competitiveness and Public Policies (GOVCOPP), Department of Economics, Management, Industrial Engineering and Tourism (DEGEIT) Universidade de Aveiro, 3810-193 Aveiro, Portugal
Interests: energy policy and regulation; energy economics; energy markets; energy demand and supply; consumer behaviour; eco-innovation; sustainability
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Prof. Dr. Nelson Martins

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Department of Mechanical Engineering & Centre for Mechanical Technology and Automation, University of Aveiro, 3810-193 Aveiro, Portugal
Interests: Heat Transfer; Thermal Simulation; Energy Management System; Climetization
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Prof. Dr. Nídia Caetano

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Department of Chemical Engineering, Instituto Superior de Engenharia do Porto (ISEP), Porto, Portugal
Interests: biodiesel; bioethanol; biorefinery; energy storage systems; microalgae biorefineries; sustainable energy systems; waste valorization; wastewater treatment; waste-to-energy
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Special Issue Information

Dear Colleagues,

Energy has assumed such an important role that it is increasingly seen as a vital civilization issue. Indeed, the existence of humanity does not seem to be possible while dependent only on natural forms of energy. The production and use of energy in a sustainable way is still a mirage, regardless of the evident research efforts and political objectives. The undeniable reality is that much of the energy currently used around the world is still based on fossil resources (oil and coal), although renewable energy has increased significantly. The use of renewable energy at an increasingly large scale presents huge challenges. This is a complex multidisciplinary problem that encloses the paradigm of energy generation. Challenges include a chain of social stakeholders ranging from the teaching/learning partners to integrated solution providers. In this new scenario, it is necessary to ensure the reliability and efficiency required at various levels of scalability. Energy storage systems and active demand side participation are increasingly needed; with efficient use of available energy, demand flexibility must be intelligently used to compensate for the intermittency of renewable energy sources, such as wind and sun. In this chain context, the circular economy vision is increasingly important because it is a model that is close to the functioning of nature. Therefore, this Special Edition aims to contribute to the "Challenges Towards Sustainable Energy" agenda through scientific development to improve the global and multidisciplinary performance of modern energy systems.

We invite authors to submit articles on innovative technical developments, reviews, case studies, analyses, and evaluations from different disciplines that are relevant to the existing challenges related to sustainable energy. These include smart grids, renewable energy, energy storage systems and materials, life cycle analysis of energy (systems), zero-energy buildings, energy efficiency, (novel) electric and hybrid vehicles, financial and economic analysis, intelligent systems, energy and big data, energy policy, novel energy sources, and renewable-based generation, among others.

Prof. Dr. Carlos Felgueiras
Prof. Dr. Zita A. Vale
Prof. Dr. Coriolano Salvini
Prof. Dr. Luis Tarelho
Prof. Dr. Marta Ferreira Dias
Prof. Dr. Nelson Martins
Prof. Dr. Nídia Caetano
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 submissions that pass pre-check are 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. Energies 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 2600 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

Battery design and project
Biofuels as liquid carriers of energy
Distributed generation
Energy policy
Energy storage and transportation
Energy storage integration in renewable Energy systems
Energy storage systems
Energy systems integration
Fuel cells
Hydrogen or methane as energy carriers
Information management
Information management, financial and economic analysis of energy storage systems
Integration of storage energy storage systems in sustainable buildings
Life cycle analysis of energy storage systems
Novel batteries
Novel energy sources
Optimization
Phase change materials
Pumped-hydro energy storage
PV and energy storage systems
Renewable based mobility
Smart grids and energy systems
Thermal energy storage

Published Papers (8 papers)

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Research

27 pages, 831 KiB

Open AccessArticle

Dynamic Modelling of Causal Relationship between Energy Consumption, CO₂ Emission, and Economic Growth in SE Asian Countries

by Jaruwan Chontanawat

Energies 2020, 13(24), 6664; https://doi.org/10.3390/en13246664 - 17 Dec 2020

Cited by 14 | Viewed by 2896

Abstract

Southeast Asian region is fast growing in terms of economy with rapid population growth, high energy consumption, and pollution. Understanding these linkages are crucial to guidance of appropriate policy. This study aims to examine the causal relationship between energy consumption with economic growth and CO₂ emissions of the four selected Asian countries, namely Indonesia, Malaysia, Philippines, and Thailand between the years 1971–2017 using Johansen cointegration method combined with Granger causality model. The results found the evidence of cointegration in all countries implying a long-run relationship among energy consumption, economy and pollution exists. The causality main results show the evidence of unidirectional causality running from economic growth to energy consumption in Indonesia, Malaysia, and Thailand, while the opposite direction was found in Philippines. The results of Indonesia, Malaysia, and Thailand support “conservative hypothesis” suggesting that energy conservation policies could be adopted in these countries as it would not constrain growth of the economies. Whereas the results of Philippines appear to support “growth hypothesis” implying that energy is a key driver to stimulate economy. Limiting the use of energy could affect the economy. Instead, the policies, therefore, should focus on promoting other alternative energy source such as renewable energy in order to maintain sustainable growth. Full article

(This article belongs to the Special Issue Challenges Towards Sustainable Energy)

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23 pages, 10126 KiB

Open AccessArticle

Hydrodynamic Effects of Tidal-Stream Power Extraction for Varying Turbine Operating Conditions

by Lilia Flores Mateos and Michael Hartnett

Energies 2020, 13(12), 3240; https://doi.org/10.3390/en13123240 - 23 Jun 2020

Cited by 4 | Viewed by 1896

Abstract

Realistic evaluation of tidal-stream power extraction effects on local hydrodynamics requires the inclusion of the turbine’s operating conditions (TOC). An alternative approach for simulating the turbine’s array energy capture at a regional scale, momentum sink-TOC, is used to assess the impact of power extraction. The method computes a non-constant thrust force calculated based on the turbine’s operating conditions, and it uses the wake induction factor and blockage ratio to characterise the performance of a turbine. Additionally, the momentum sink-TOC relates the changes produced by power extraction, on the velocity and sea surface within the turbine’s near-field extension, to the turbine’s thrust force. The method was implemented in two hydrodynamic models that solved gradually varying flows (GVF) and rapidly varying flows (RVF). The local hydrodynamic effects produced by tidal-stream power extraction for varying the turbine’s operating conditions was investigated in (i) the thrust and power coefficient calculation, (ii) flow rate reduction, and (iii) tidal currents’ velocity and elevation profiles. Finally, for a turbine array that operates at optimal conditions, the potential energy resource was assessed. The maximisation of power extraction for electrical generation requires the use of an optimum turbine wake induction factor and an adequate blockage ratio, so that the power loss due to turbine wake mixing is reduced. On the other hand, the situations where limiting values of these parameters are used should be avoided as they lead to negligible power available. In terms of hydrodynamical models, an RVF solver provided a more accurate evaluation of the turbine’s operating conditions effect on local hydrodynamics. Particularly satisfactory results were obtained for a partial-fence. In the case of a fence configuration, the GVF solver was found to be a computationally economical tool to pre-assess the resource; however, caution should be taken as the solver did not accurately approximate the velocity decrease produced by energy extraction. Full article

(This article belongs to the Special Issue Challenges Towards Sustainable Energy)

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16 pages, 4234 KiB

Open AccessArticle

Patent Analysis of High Efficiency Tunneling Oxide Passivated Contact Solar Cells

by Chieh-Wa Tsai, Tung-Kuan Liu and Po-Wen Hsueh

Energies 2020, 13(12), 3060; https://doi.org/10.3390/en13123060 - 12 Jun 2020

Cited by 1 | Viewed by 2644

Abstract

High efficiency tunneling oxide passivated contact (TOPCon) solar cell is the traditional PN junction structure, combined the advantages of using a thin film of the passivated silicon surface to separate the metal from the silicon wafer. In this study, the patent analysis of high efficiency TOPCon solar cell is presented. The structure and process technology of TOPCon solar cell were analyzed first, which is used as the basis for the key words of the patent search. The patent management chart analysis is provided, and then the patent portfolio of the main research countries and important manufacturers on the research subject can be recognized. Moreover, the technology-function matrix analysis is used to comprehend the technical development trend of the research topic. The results indicate the TOPCon solar cell technology currently entered into the maturity stage in 2019, and the companies with the top three number of patents are LG Electronics, SunPower, and SolarCity (which was acquired by Tesla in 2016). SunPowern is the earliest patent assignee, and LG Electronics is the follower, while its patent outputs are heavily concentrated after 2014. Patent technology-function matrix found the development focus of the device-related technologies are tunneling oxide and polycrystalline silicon, with a total of 21 patents, and the development focus of process-related technologies are the process of tunneling oxide layers and the process of polysilicon film. Based on the analysis results, the future development prospects of the research topic and the direction of patent portfolio are evaluated. Full article

(This article belongs to the Special Issue Challenges Towards Sustainable Energy)

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21 pages, 1504 KiB

Open AccessArticle

Research on Environmental Sustainability of Coal Cities: A Case Study of Yulin, China

by Xiaowei Zhai, Zhuo Cheng, Keyu Ai and Bo Shang

Energies 2020, 13(10), 2470; https://doi.org/10.3390/en13102470 - 14 May 2020

Cited by 11 | Viewed by 2154

Abstract

Coal cities are an essential impetus for economic development and urbanization processes in China. However, a series of environmental issues provoked by resource exploitation cause the environmental sustainability of coal cities to face enormous challenges. Therefore, on the basis of the time series data of Yulin City from 1996 to 2017, this paper explores the nexus between socioeconomic development and industrial “three wastes” emissions by adopting the Tapio decoupling model, the environmental Kuznets curve (EKC) hypothesis, and the vector auto-regressive (VAR) model. The results show that Yulin’s economic development remains in an extensive stage and will not decouple from the environmental pollution in a short time. Except for the nexus of industrial solid waste and economic growth, which is an inverted U-shaped, the EKC hypothesis is not valid for industrial wastewater and industrial waste gas. Through the VAR (2) model, the impact of per capita gross domestic product (GDP) on industrial waste emissions is consistent with the results of the EKC hypothesis. Moreover, industrial waste emissions have a positive correlation with the per capita raw coal output, the energy consumption per unit of GDP, and the proportion of secondary industry. Hence, it is necessary to formulate targeted measures from industrial restructuring, industrial chain extension, governance model optimization, and waste comprehensive utilization to realize the environmental sustainability of coal cities. Full article

(This article belongs to the Special Issue Challenges Towards Sustainable Energy)

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12 pages, 3345 KiB

Open AccessArticle

Co-Gasification of Crude Glycerol/Animal Fat Mixtures

by Ana Almeida, Rosa Pilão, Albina Ribeiro, Elisa Ramalho and Carlos Pinho

Energies 2020, 13(7), 1699; https://doi.org/10.3390/en13071699 - 03 Apr 2020

Cited by 3 | Viewed by 1918

Abstract

The aim of this work was to assess the technical viability of glycerol/fat co-gasification. The gasification performance was studied in a downflow fixed bed reactor using activated alumina particles as bed material and steam as oxidizing agent. The effect of gasification temperature, from 800 to 950 °C was studied with a feed mixture with 10% (w/w) of animal fat. The influence of fat incorporation on the feedstock in the overall gasification process was also performed, using 3% (w/w) and 5% (w/w) of fat in feed mixtures. Samples of dry gas from the gasifier were collected and analyzed by gas chromatography in order to determine the CO, CO₂, CH₄, and H₂ content. The best results were obtained using the highest tested temperature, 950 °C, and using 3% (w/w) of animal fat in the feed mixture. The overall results revealed that the co-gasification of glycerol/animal fat mixtures seems to be a feasible technical option. Full article

(This article belongs to the Special Issue Challenges Towards Sustainable Energy)

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17 pages, 5074 KiB

Open AccessArticle

Two-Stage Radial Turbine for a Small Waste Heat Recovery Organic Rankine Cycle (ORC) Plant

by Ambra Giovannelli, Erika Maria Archilei and Coriolano Salvini

Energies 2020, 13(5), 1054; https://doi.org/10.3390/en13051054 - 27 Feb 2020

Cited by 10 | Viewed by 3239

Abstract

Looking at the waste heat potential made available by industry, it can be noted that there are many sectors where small scale (< 100 kWe) organic Rankine cycle (ORC) plants could be applied to improve the energy efficiency. Such plants are quite challenging from the techno-economic point of view: the temperature of the primary heat source poses a low cutoff to the system thermodynamic efficiency. Therefore, high-performance components are needed, but, at the same time, they have to be at low cost as possible to assure a reasonable payback time. In this paper, the design of a two-stage radial in-flow turbine for small ORC industrial plants is presented. Compared to commonly applied mono-stage expanders (both volumetric and dynamic), this novel turbine enables plants to exploit higher pressure ratios than conventional plants. Thus, the theoretical limit to the cycle efficiency is enhanced with undoubted benefits on the overall ORC plant performance. The design process involved 1D/2D models as well as 3D Computational Fluid Dynamic ones. After the design of the preliminary configuration, sensitivity analyses were carried out varying the most relevant geometric parameters for design performance improvement. Thereafter, the stages were both analyzed in off-design conditions giving their performance maps. Moreover, a stage stacking procedure was applied to obtain the overall turbine behavior. Full article

(This article belongs to the Special Issue Challenges Towards Sustainable Energy)

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23 pages, 1836 KiB

Open AccessArticle

Decomposition Analysis of the Carbon Emissions of the Manufacturing and Industrial Sector in Thailand

by Jaruwan Chontanawat, Paitoon Wiboonchutikula and Atinat Buddhivanich

Energies 2020, 13(4), 798; https://doi.org/10.3390/en13040798 - 12 Feb 2020

Cited by 6 | Viewed by 2898

Abstract

Since the 1990s, CO₂ emissions have increased steadily in line with the growth of production and the use of energy in the manufacturing sector in Thailand. The Logarithmic Mean Divisia Index Method is used for analysing the sources of changes in CO₂ emissions as well as the CO₂ emission intensity of the sector in 2000–2018. On average throughout the period, both the amount of CO₂ emissions and the CO₂ emission intensity increased each year relative to the baseline. The structural change effect (effect of changes of manufacturing production composition) reduced, but the intensity effect (effect of changes of CO₂ emissions of individual industries) increased the amount of CO₂ emissions and the CO₂ emission intensity. The unfavourable CO₂ emission intensity change came from the increased energy intensity of individual industries. The increased use of coal and electricity raised the CO₂ emissions, whereas the insignificant change in emission factors showed little impact. Therefore, the study calls for policies that decrease the energy intensity of each industry by limiting the use of coal and reducing the electricity used by the manufacturing sector so that Thailand can make a positive contribution to the international community’s effort to achieve the goal of CO₂ emissions reduction. Full article

(This article belongs to the Special Issue Challenges Towards Sustainable Energy)

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21 pages, 7628 KiB

Open AccessArticle

Energy Scheduling Using Decision Trees and Emulation: Agriculture Irrigation with Run-of-the-River Hydroelectricity and a PV Case Study

by Omid Abrishambaf, Pedro Faria, Zita Vale and Juan M. Corchado

Energies 2019, 12(20), 3987; https://doi.org/10.3390/en12203987 - 20 Oct 2019

Cited by 8 | Viewed by 2793

Abstract

Agriculture is the very backbone of every country. Unfortunately, agricultural sustainability is threatened by the lack of energy-efficient solutions. The threat becomes more evident with the constantly growing world population. The research community must, therefore, focus on resolving the problem of high energy consumption. This paper proposes a model of energy scheduling in agricultural contexts. Greater energy efficiency is achieved by means of PV (photovoltaics) and hydropower, as demonstrated in the conducted case study. The developed model is intended for contexts where the farm is located near a river, so the farmer can use the flowing water to produce energy. Moreover, the model has been emulated using a variety of state-of-the-art laboratory devices. Optimal energy scheduling is performed via a decision tree approach, optimizing the use of energy resources and reducing electricity costs. Finally, a realistic scenario is presented to show the technical features and the practical behaviors of each emulator when adapting the results of the decision tree. The research outcomes demonstrate the importance of the technical validation of each model. In addition, the results of the emulation reveal practical issues that had not been discovered during the theoretical study or during the simulation. Full article

(This article belongs to the Special Issue Challenges Towards Sustainable Energy)

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