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Special Issue "Sustainable Energy Systems: Efficiency and Optimization"

A special issue of Energies (ISSN 1996-1073). This special issue belongs to the section "Energy Economics and Policy".

Deadline for manuscript submissions: 31 October 2019

Special Issue Editors

Guest Editor
Prof. Alan Brent

Sustainable Energy Systems, School of Engineering and Computer Science, Victoria University of Wellington, 6140, New Zealand
Website | E-Mail
Interests: sustainability analysis of energy systems; Technical design and integration of renewable energy systems
Co-Guest Editor
Prof. Dr. Toshihiko Nakata

Department of Management Science and Technology, Graduate School of Engineering, Tohoku University, Japan
Website | E-Mail
Interests: integrated design and analysis for sustainable energy systems

Special Issue Information

Dear Colleagues,

New, alternative energy technologies are rapidly becoming affordable, and it is expected that these will be immensely disruptive to our traditional mode of centralised energy generation, transmission, and distribution. Additionally, the severe climate (and other) impacts of many traditional energy generation and utilisation techniques are widely accepted. As stated in the World Energy Outlook of the International Energy Agency (IEA): “the global energy scene is in a state of flux, thrown off balance by falling costs for a range of technologies, led by wind and solar…”. Furthermore, the IEA states that it “…expects renewable electricity generation to increase by a further two-fifths by 2021. However, renewable heat and transport are lagging behind, despite good potential…”. For these changes or transitions to be just and sustainable, systemic analyses are required, with an emphasis on optimizing the energy sector to be better integrated with the other sectors of the economy, thereby ensuring the efficiency of future energy value chains. Such systemic analyses utilise concepts, methods and tools such as system dynamics, urban metabolism, industrial ecology, and life cycle analyses, to inform policy- and decision-making.

This Special Issue is therefore focused on how the concepts, methods and tools of systemic analyses have been utilised in various contexts to enable a transition to sustainable energy systems, with an emphasis on the efficiency and optimisation of future energy value chains.

Prof. Dr. Alan Brent
Guest Editor

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. 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 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.


  • Sustainability
  • Macro-level
  • Systemic analyses
  • Energy value chains
  • Efficiency
  • Optimization

Published Papers (1 paper)

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Open AccessArticle
Optimal Operational Strategy for Power Producers in Korea Considering Renewable Portfolio Standards and Emissions Trading Schemes
Energies 2019, 12(9), 1667; https://doi.org/10.3390/en12091667
Received: 15 April 2019 / Revised: 28 April 2019 / Accepted: 29 April 2019 / Published: 1 May 2019
PDF Full-text (7095 KB) | HTML Full-text | XML Full-text
Globally, many countries are experiencing economic growth while concurrently increasing their energy consumption. Several have begun to consider a low-carbon energy mix to mitigate the environmental impacts caused by increased fossil fuel consumption. In terms of maximizing profits, however, power producers are not [...] Read more.
Globally, many countries are experiencing economic growth while concurrently increasing their energy consumption. Several have begun to consider a low-carbon energy mix to mitigate the environmental impacts caused by increased fossil fuel consumption. In terms of maximizing profits, however, power producers are not sufficiently motivated to expand capacity due to high costs. Thus, the Korean government initiated the Renewable Portfolio Standard (RPS), an obligation to generate a certain proportion of a producer’s total generation using renewable energy for power producers with capacities of 500 MW or more, and the Emissions Trading Scheme (ETS), designed to attain a carbon emissions reduction goal. We propose a mathematical model to derive the optimal operational strategy for maximizing power producer profits with a capacity expansion plan that meets both regulations. As such, the main purpose of this study was to obtain the optimal operational strategy for each obligatory power producer. To that end, we defined a 2 × 2 matrix to classify their types and to conduct scenario-based analyses to assess the impact of major factor changes on solutions for each type of power producer. Finally, for the power generation industry to operate in a sustainable and eco-friendly manner, we extracted policy implications that the Korean government could consider for each type of power producer. Full article
(This article belongs to the Special Issue Sustainable Energy Systems: Efficiency and Optimization)

Figure 1

Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

Type: Article
Title: Setting the Scene for Energy Metabolism Assessment of Nairobi City County
Josephine Kaviti Musango*,1, Amollo Ambole 2, Baraka Mwau 3, Paul Currie 1, Kareem Buyana 4; Madara Ogot 5, Alan C Brent 6,7, and Christer Anditi 2
1 School of Public Leadership and Centre for Renewable and Sustainable Energy Studies; urban Modelling and Metabolism Assessment, Centre for Complex Systems in Transition, Stellenbosch University, South Africa
2 School of the Arts and Design, University of Nairobi, Kenya
3 Urban Planning and Research Consultant, Nairobi, Kenya
4 Urban Action Lab, Makerere University, Uganda
5 Department of Mechanical & Manufacturing Engineering, University of Nairobi, Kenya
6 Department of Industrial Engineering, Centre for Renewable and Sustainable Energy Studies (CRSES), uMAMA, Centre for Complex Systems in Transitions (CST), Stellenbosch University, South Africa
7 Sustainable Energy Systems, Engineering and Computer Science, Victoria University of Wellington, New Zealand
* Correspondence: jmusango@sun.ac.za;
Abstract: Energy metabolism assessment of cities requires quality disaggregated energy data to sufficiently support urban energy planning and policy, as well as to monitor the achievement of the sustainable development goals directly linked to energy. Further, urban energy planning should be integrated with land use planning. An urban metabolism perspective serves as a framework for assessing energy metabolism and as a boundary object for its integration into planning and other decision making processes. While urban metabolism assessments have been undertaken globally, there are limited empirical case studies, particularly in Africa, to advance from theory to implementation. This paper undertakes a basic energy metabolism assessment of Nairobi City County in Kenya to set the scene for deeper study as data become available. The basic urban energy metabolism assessment does not entirely focus on accounting methods but also examines the socio-demographics, economics, biophysical context and policy frameworks that govern the internal dynamics of metabolic energy processes. The results show that Nairobi City County imports its energy requirements from beyond its administrative borders. Further, energy policy and planning is biased towards electricity and petroleum, yet biomass represents the highest level of energy consumption, particularly for cooking services, across income groups. To improve the effectiveness of implementation of sustainability interventions, information about Nairobi City County’s energy metabolism should be of appropriate spatial and temporal resolution to inform urban planning and design. Recommendations are highlighted for future data requirements, which can support disaggregated energy data collection.
Keywords: Urban energy metabolism; Nairobi City County; Energy planning; African cities

Type: Article
Title: Conceptualising Household Energy Metabolism: A Methodological Contribution
Adél Strydom 1, Josephine Kaviti Musango *, 1, Paul Klugman Currie 1
1 School of Public Leadership; urban Modelling and Metabolism Assessment (uMAMA) Stellenbosch University, South Africa
* Correspondence: jmusango@sun.ac.za;
Abstract: Urban metabolism assessments enable the quantification of resource flows, which is useful for finding intervention points for sustainability. Household energy consumption accounts for 72% of greenhouse gas emissions; therefore, a household energy metabolism assessment would reveal intervention points to reshape household energy consumption to inform decision-makers about a more sustainable urban energy system. However, existing household energy consumption studies tend to limit the focus on outflows in the form of greenhouse gas emissions and are mostly undertaken at city or national level. This study therefore developed a method to assess household energy metabolism focusing on energy inflows in the form of carriers, and through-flows in the form of services, to identify intervention points for sustainability. The method was then applied to assess the energy metabolism of different households in Cape Town, categorised by income groups. The study argued that, the develop method is useful for undertaking household energy metabolic assessments, and is applicable in both formal and informal city settings.
Keywords: Urban metabolism, Household energy metabolism, Household energy metabolism assessment methods, Household energy consumption

Type: Article
Title: Prospects in Reverse Electrodialysis Driven Water Electrolysis for Sustainable Hydrogen Production
Authors: Ramato Ashu Tufa 1, Efrem Curcio 2,3 and Karel Bouzek 1
Department of Inorganic Technology, University of Chemistry and Technology Prague, Technická 5, 166 28 Prague 6, Czech Republic
2 Department of Environmental and Chemical Engineering DIATIC-UNICAL, University of Calabria Via P. Bucci CUBO 45A, 87036 Rende (CS) Italy
3 Institute on Membrane Technology, National Research Council of Italy ITM-CNR, Via P. Bucci CUBO 17C, 87036 Rende (CS) Italy
Abstract: Hydrogen represents a clean, efficient and versatile energy carrier that can address issues of energy, the environment, and sustainability in general. It can be produced through water electrolysis using electricity from renewable resources. Wind and solar energy resources have been widely investigated for this purpose. On the other hand, there exists an enormous potential of salinity gradient energy, which is a renewable energy generated from mixing two solutions of different salinity, and harnessed by membrane based-technologies like revere electrodialysis (RED). Herein, we present most recent advances in the application of RED for hydrogen production integrated with water electrolysers. We compare different scenarios of energy systems formed by coupling RED with low temperature (alkaline, acidic) and high temperature (solid oxide) water electrolysers in terms of hydrogen production rate and efficiency. Finally, we provide prospective research directions for system optimization towards enhanced performance and scale-up.

Type: Article
Title: Using a System Dynamics Modelling Process to Determine the Impact of eBus and eTruck Market Penetration on Carbon Emissions in South Africa
Authors: Nalini Sooknanan Pillay 1,*, Alan Colin Brent 2, Josephine Kaviti Musango 3 and Francois Van Geems 4
1 Eskom SOC, Research Testing & Development; e-mail: Pillayna@eskom.co.za
2 Department of Industrial Engineering, and Centre for Renewable and Sustainable Energy; Stellenbosch University e-mail: acb@sun.ac.za
3 School of Public Leadership, and Centre for Renewable and Sustainable Energy Studies; Stellenbosch University e-mail: josephine.musango@sun.ac.za
4 Eskom SOC, Research Testing & Development; e-mail: VGeemsSF@eskom.co.za
* Correspondence: Pillayna@eskom.co.za
Received: date; Accepted: date; Published: date
Abstract: The complexities inherent in electricity value chains are non-linear in nature and require unconventional modelling methods such as system dynamics modelling. This paper provides an overview of the system dynamics method applied to obtain an understanding of the impact of electric-bus, -car and -truck market penetration on carbon emissions, through the development of the electric mobility simulator (eMobiSim). The first scenario was based on a market penetration target of 10% by year 2040 for each vehicle category (known as the Relative Ten scenario). The second scenario (known as the World Reference scenario) was based on a market penetration of 22% eCars, 2% eTrucks and 80% eBuses. Results indicated that the World Reference scenario was the most optimistic with the largest decrease in carbon emissions in the transport sector for eCars (7.89 Mton) and eBuses (1.79 Mtons). The best scenario to reduce carbon emissions with eTrucks was for the Relative Ten scenario, where a reduction of 1.85 Mtons was possible.
Keywords: electric vehicles; battery storage; second-life

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