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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 March 2018) | Viewed by 71810

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Dr. Vicky Albert-Seifried

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Smart Cities Group, Fraunhofer Institute for Solar Energy Systems, Heidenhofstr. 2, 79110 Freiburg, Germany
Interests: integrated modeling and optimization of energy systems; electricity and heat coupling; assessment of renewable energy potential; applications of renewable technologies and building energy efficiency
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Dear Colleagues,

There is a worldwide trend towards Smart Cities, and many governments have set goals to ‘smartify’ urban infrastructures and services in order to make cities more efficient and responsive to the needs of the people, business and the environment. In addition, many cities are committed to substantial reduction in greenhouse gas (GHG) emissions in order to mitigate climate change. These endeavors are expected to drive significant transformation in cities in the coming decades.

In this Special Issue, we seek to bring together latest research that aims to make cities smarter and more sustainable through the adoption of novel concepts or use of innovative technologies in the building, energy and transportation sectors. We are looking for contributions that address challenges at the city district level and which demonstrate new approaches for increasing energy efficiency and reducing greenhouse gas emissions. We accept both conceptual and empirical studies with sound methodologies (computer modeling, data analytics, laboratory simulation, field campaigns, etc.). Works that are potentially transferrable to different cities are particularly welcome. Topics of interest include, but are not limited to:

Tools to support low-carbon strategies
Distributed energy systems
Smart/Sustainable transportation
Energy storage
Power-to-heat

Dr. Vicky Cheng
Guest Editor

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Keywords

Smart cities
Sustainable transportation
Sustainable urban energy systems
Low carbon strategies
Energy efficiency

Published Papers (14 papers)

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Research

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15 pages, 7576 KiB

Open AccessArticle

Building Retrofit with Photovoltaics: Construction and Performance of a BIPV Ventilated Façade

by Nuria Martín-Chivelet, Juan Carlos Gutiérrez, Miguel Alonso-Abella, Faustino Chenlo and José Cuenca

Energies 2018, 11(7), 1719; https://doi.org/10.3390/en11071719 - 01 Jul 2018

Cited by 40 | Viewed by 5339

Abstract

Building retrofit offers the opportunity to reduce energy consumption, improve energy efficiency and increase the use of renewable energy sources. The photovoltaic (PV) technology can be integrated into the building envelope, where conventional construction materials can be easily substituted by PV modules. Prices are competitive with some other solutions and good architectural building integrated photovoltaics (BIPV) solutions enhance the appearance of the buildings. All this makes BIPV an attractive solution for effectively and sustainably retrofitting building envelopes, providing savings in materials and in conventional electricity consumption and, at the same time, improving the energy efficiency of the buildings. This paper shows a building retrofit case study in which standard PV modules are integrated into a new ventilated façade, aiming at serving as an easy-to-implement example for large-scale actions. Full article

(This article belongs to the Special Issue Energy Efficient and Smart Cities)

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12 pages, 1392 KiB

Open AccessArticle

Comparative Performance of Semi-Transparent PV Modules and Electrochromic Windows for Improving Energy Efficiency in Buildings

by Nuria Martín-Chivelet, Cecilia Guillén, Juan Francisco Trigo, José Herrero, Juan José Pérez and Faustino Chenlo

Energies 2018, 11(6), 1526; https://doi.org/10.3390/en11061526 - 12 Jun 2018

Cited by 26 | Viewed by 3180

Abstract

Advanced constructive materials, such as electrochromic smart windows (ECSWs) and building integrated photovoltaics modules (BIPV), can improve the energy efficiency in buildings. A good optical and thermal characterization of these elements is necessary to assess and compare their performance. The existing testing procedures for glass in buildings are applied to both types of elements, and it is considered that while the optical procedures are suitable and allow good comparison of the two technologies, the indoor thermal testing procedures are not valid for BIPV nor ECSWs, because temperature of these absorbing elements strongly depend on the irradiance, something not considered in the current standards. To show and characterize this dependence, simultaneously monitoring of different photovoltaics (PV) modules and electrochromic windows has been performed outdoors under solar irradiance. A relationship between the surface temperature, the irradiance, and the ambient temperature has been obtained for each sample to compare both technologies. Full article

(This article belongs to the Special Issue Energy Efficient and Smart Cities)

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12 pages, 1049 KiB

Open AccessArticle

Towards Efficient Sink Mobility in Underwater Wireless Sensor Networks

by Aqeb Yahya, Saif Ul Islam, Adnan Akhunzada, Ghufran Ahmed, Shahaboddin Shamshirband and Jaime Lloret

Energies 2018, 11(6), 1471; https://doi.org/10.3390/en11061471 - 06 Jun 2018

Cited by 33 | Viewed by 3406

Abstract

The unique characteristics of underwater environment such as long propagation delay, limited bandwidth, energy-constraint and non-uniform topology are big challenges in designing a routing protocol for underwater wireless sensor networks (UWSNs). In this paper, a novel routing scheme is proposed through which two mobile sinks are used for efficient collection of sensed data packets. Moreover, a new metric “Mobile Sink Utility Ratio (MUR)” is also introduced that helps in measuring the usage of mobile sink in the collection of data packets. The proposed scheme is rigorously evaluated and compared with current state-of-the-art routing protocols. The simulation of the proposed scheme shows promising results in terms of throughput, network lifetime, packet drop ratio and MUR. Full article

(This article belongs to the Special Issue Energy Efficient and Smart Cities)

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18 pages, 13587 KiB

Open AccessArticle

Predicting Charging Time of Battery Electric Vehicles Based on Regression and Time-Series Methods: A Case Study of Beijing

by Jun Bi, Yongxing Wang, Shuai Sun and Wei Guan

Energies 2018, 11(5), 1040; https://doi.org/10.3390/en11051040 - 24 Apr 2018

Cited by 9 | Viewed by 4594

Abstract

Battery electric vehicles (BEVs) reduce energy consumption and air pollution as compared with conventional vehicles. However, the limited driving range and potential long charging time of BEVs create new problems. Accurate charging time prediction of BEVs helps drivers determine travel plans and alleviate their range anxiety during trips. This study proposed a combined model for charging time prediction based on regression and time-series methods according to the actual data from BEVs operating in Beijing, China. After data analysis, a regression model was established by considering the charged amount for charging time prediction. Furthermore, a time-series method was adopted to calibrate the regression model, which significantly improved the fitting accuracy of the model. The parameters of the model were determined by using the actual data. Verification results confirmed the accuracy of the model and showed that the model errors were small. The proposed model can accurately depict the charging time characteristics of BEVs in Beijing. Full article

(This article belongs to the Special Issue Energy Efficient and Smart Cities)

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19 pages, 4580 KiB

Open AccessArticle

Optimal Capacity Estimation Method of the Energy Storage Mounted on a Wireless Railway Train for Energy-Sustainable Transportation

by Jaewon Kim, Joorak Kim, Changmu Lee, Gildong Kim, Hansang Lee and Byongjun Lee

Energies 2018, 11(4), 986; https://doi.org/10.3390/en11040986 - 19 Apr 2018

Cited by 8 | Viewed by 3404

Abstract

Although electric railway systems have gone through many technological innovations in their electrical, mechanical and structural engineering since the energy paradigm conversion to electrical energy, the conventional feeding system based on the catenary contact is still being applied. In order to solve the problems of the contact-based feeding system that arise and to build up the energy-sustainable electric railway system simultaneously, this paper considers the wireless railway train (WRT), which is fed by storages mounted on the board without catenary contact during driving and charged at a platform during a stop. In order to maximize the energy improvement of WRTs’ operation, the optimal power and storage capacity estimation method considering the increased weight of the additional storage devices is proposed. Through case studies of the electrical and topographical conditions of the actual operating railway route, compared with the electrical performance of the existing railway trains, it is verified that the application of WRTs leads to facility capacity margin enlargement through the peak power reduction, and cost-effectiveness improvement through the reduction of catenary loss and driving energy. Full article

(This article belongs to the Special Issue Energy Efficient and Smart Cities)

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17 pages, 3090 KiB

Open AccessArticle

Mitigating Household Energy Poverty through Energy Expenditure Affordability Algorithm in a Smart Grid

by Omowunmi Mary Longe and Khmaies Ouahada

Energies 2018, 11(4), 947; https://doi.org/10.3390/en11040947 - 16 Apr 2018

Cited by 14 | Viewed by 3557

Abstract

One of the criteria for measuring household energy poverty is the percentage of the household’s income spent on energy expenses. In this work, an autonomous income-based energy scheduling demand side management (DSM) technique called energy expenditure affordability algorithm (EEAA) is proposed to ensure that household energy expenditure is below the nation’s approved energy expenditure threshold. The EEAA problem was formulated as a mixed integer linear programming (MILP) problem and verified with real household data collected from families living in bachelor flats in Johannesburg, South Africa. Consumer preferences and satisfaction were enhanced by using the dynamic time warping (DTW) technique to minimize the distance between nominal and EEAA load profiles. Furthermore, the effects of distributed energy generation (DEG) and distributed energy storage (DES) were also investigated in light of energy expenditure affordability for improved consumer-friendly and satisfying DSM. The EEAA-DSM technique is shown to reduce household energy expenditure below the energy expenditure threshold, offering energy expenditure affordability as well as utility grid peak demand reduction (PDR). Furthermore, grid reliability and sustainability, environmental preservation and gendered energy poverty are consequential benefits of the EEAA. It also offered the households considered an average financial savings from 12% to 82%, depending on the level of implementation of distributed storage and generation to the consumer’s local energy mix. Full article

(This article belongs to the Special Issue Energy Efficient and Smart Cities)

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30 pages, 1041 KiB

Open AccessArticle

Scheduling Appliances with GA, TLBO, FA, OSR and Their Hybrids Using Chance Constrained Optimization for Smart Homes

by Zunaira Nadeem, Nadeem Javaid, Asad Waqar Malik and Sohail Iqbal

Energies 2018, 11(4), 888; https://doi.org/10.3390/en11040888 - 10 Apr 2018

Cited by 41 | Viewed by 4935

Abstract

In this paper, we design a controller for home energy management based on following meta-heuristic algorithms: teaching learning-based optimization (TLBO), genetic algorithm (GA), firefly algorithm (FA) and optimal stopping rule (OSR) theory. The principal goal of designing this controller is to reduce the energy consumption of residential sectors while reducing consumer’s electricity bill and maximizing user comfort. Additionally, we propose three hybrid schemes OSR-GA, OSR-TLBO and OSR-FA, by combining the best features of existing algorithms. We have also optimized the desired parameters: peak to average ratio, energy consumption, cost, and user comfort (appliance waiting time) for 20, 50, 100 and 200 heterogeneous homes in two steps. In the first step, we obtain the optimal scheduling of home appliances implementing our aforementioned hybrid schemes for single and multiple homes while considering user preferences and threshold base policy. In the second step, we formulate our problem through chance constrained optimization. Simulation results show that proposed hybrid scheduling schemes outperformed for single and multiple homes and they shift the consumer load demand exceeding a predefined threshold to the hours where the electricity price is low thus following the threshold base policy. This helps to reduce electricity cost while considering the comfort of a user by minimizing delay and peak to average ratio. In addition, chance-constrained optimization is used to ensure the scheduling of appliances while considering the uncertainties of a load hence smoothing the load curtailment. The major focus is to keep the appliances power consumption within the power constraint, while keeping power consumption below a pre-defined acceptable level. Moreover, the feasible regions of appliances electricity consumption are calculated which show the relationship between cost and energy consumption and cost and waiting time. Full article

(This article belongs to the Special Issue Energy Efficient and Smart Cities)

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21 pages, 14996 KiB

Open AccessEditor’s ChoiceArticle

Contributions of Bottom-Up Energy Transitions in Germany: A Case Study Analysis

by Ortzi Akizu, Gorka Bueno, Iñaki Barcena, Erol Kurt, Nurettin Topaloğlu and Jose Manuel Lopez-Guede

Energies 2018, 11(4), 849; https://doi.org/10.3390/en11040849 - 05 Apr 2018

Cited by 30 | Viewed by 7854

Abstract

Within the context of an energy transition towards achieving a renewable low-impact energy consumption system, this study analyses how bottom-up initiatives can contribute to state driven top-down efforts to achieve the sustainability related goals of (1) reducing total primary energy consumption; (2) reducing residential electricity and heat consumption; and (3) increasing generated renewable energy and even attaining self-sufficiency. After identifying the three most cited German bottom-up energy transition cases, the initiatives have been qualitatively and quantitatively analysed. The case study methodology has been used and each initiative has been examined in order to assess and compare these with the German national panorama. The novel results of the analysis demonstrate the remarkable effects of communal living, cooperative investment and participatory processes on the creation of a new sustainable energy system. The study supports the claim that bottom-up initiatives could also contribute to energy sustainability goals together within the state driven plans. Furthermore, the research proves that the analysed bottom-up transitions are not only environmentally and socially beneficial but they can also be economically feasible, at least in a small scale, such as the current German national top-down energy policy panorama. Full article

(This article belongs to the Special Issue Energy Efficient and Smart Cities)

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29 pages, 47779 KiB

Open AccessArticle

The Effect of Climate Conditions on the Relation between Energy Efficiency and Urban Form

by Dimitra Tsirigoti and Katerina Tsikaloudaki

Energies 2018, 11(3), 582; https://doi.org/10.3390/en11030582 - 07 Mar 2018

Cited by 16 | Viewed by 4688

Abstract

Urban sustainability has been connected to form and compactness of the urban tissue. At the same time the relationship between urban form and energy efficiency is strongly affected by climate. This paper investigates the effect of climate conditions on the relation between urban morphology and energy efficiency of urban blocks, focusing on the Greek city context. A set of building block typologies is analyzed with regard to their form factors such as S/V ratio, coverage ratio and building ratio for the climatic conditions of two cities, each one belonging to a different climatic zone. Heating and cooling loads are calculated at an urban block scale for the climate of the city of Thessaloniki (zone C) and of the city of Heraklion (zone A) in order to draw conclusions about the relation between geometry factors and energy efficiency. The results of the research indicate that there is a strong relationship between urban morphology factors and energy efficiency and that the total load demand of urban blocks can be described as a function of form parameters. Results of the research, concerning the energy demand calculation, are valuable since they indicate the energy profile of each typology according to climate and can be used for defining different urban strategies towards sustainability in a context-based climate dependent analysis. Full article

(This article belongs to the Special Issue Energy Efficient and Smart Cities)

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5735 KiB

Open AccessArticle

Economic Feasibility Analysis for Renewable Energy Project Using an Integrated TFN–AHP–DEA Approach on the Basis of Consumer Utility

by Lu Gan, Dirong Xu, Lin Hu and Lei Wang

Energies 2017, 10(12), 2089; https://doi.org/10.3390/en10122089 - 09 Dec 2017

Cited by 14 | Viewed by 5860

Abstract

A renewable energy (RE) project has been brought into focus in recent years. Although there is quite a lot of research to assist investors in assessing the economic feasibility of the project, because of the lack of consideration of consumer utility, the existing approaches may still cause a biased result. In order to promote further development, this study focuses on the economic feasibility analysis of the RE project on the basis of consumer utility in the whole life cycle. Therefore, an integrated approach is proposed, which consists of triangular fuzzy numbers (TFNs), an analytic hierarchy process (AHP) and data envelopment analysis (DEA). The first step is to determine the comprehensive cost index weights of DEA by TFN–AHP. Secondly, to solve the problem, the first DEA model, which is proposed by A. Charnes, W. W. Cooper and E. Rhodes (C²R), is established to calculate the DEA effectiveness. Then, the third task involves designing a computer-based intelligent interface (CBII) to simplify realistic application and ensure performance efficiency. Finally, a solar water heater case study is demonstrated to validate the effectiveness of the entire method’s system. The study shows that this could make investors’ lives easier by using the CBII scientifically, reasonably and conveniently. Moreover, the research results could be easily extended to more complex real-world applications. Full article

(This article belongs to the Special Issue Energy Efficient and Smart Cities)

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5799 KiB

Open AccessArticle

A Design of a Hybrid Non-Linear Control Algorithm

by Farinaz Behrooz, Norman Mariun, Mohammad Hamiruce Marhaban, Mohd Amran Mohd Radzi and Abdul Rahman Ramli

Energies 2017, 10(11), 1823; https://doi.org/10.3390/en10111823 - 10 Nov 2017

Cited by 3 | Viewed by 3430

Abstract

One of the high energy consuming devices in the buildings is the air-conditioning system. Designing a proper controller to consider the thermal comfort and simultaneously control the energy usage of the device will impact on the system energy efficiency and its performance. The aim of this study was to design a Multiple-Input and Multiple-Output (MIMO), non-linear, and intelligent controller on direct expansion air-conditioning system The control algorithm uses the Fuzzy Cognitive Map method as a main controller and the Generalized Predictive Control method is used for assigning the initial weights of the main controller. The results of the proposed controller shows that the controller was successfully designed and works in set point tracking and under disturbance rejection tests. The obtained results of the Generalized Predictive Control-Fuzzy Cognitive Map controller are compared with the previous MIMO Linear Quadratic Gaussian control design on the same direct expansion air-conditioning system under the same conditions. The comparative results indicate energy savings would be achieved with the proposed controller with long-term usage. Energy efficiency and thermal comfort conditions are achieved by the proposed controller. Full article

(This article belongs to the Special Issue Energy Efficient and Smart Cities)

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1320 KiB

Open AccessArticle

Profitability of Residential Battery Energy Storage Combined with Solar Photovoltaics

by Christoph Goebel, Vicky Cheng and Hans-Arno Jacobsen

Energies 2017, 10(7), 976; https://doi.org/10.3390/en10070976 - 11 Jul 2017

Cited by 31 | Viewed by 5616

Abstract

Lithium-ion (Li-Ion) batteries are increasingly being considered as bulk energy storage in grid applications. One such application is residential energy storage combined with solar photovoltaic (PV) panels to enable higher self-consumption rates, which has become financially more attractive recently due to decreasing feed-in subsidies. Although residential energy storage solutions are commercially mature, it remains unclear which system configurations and circumstances, including aggregator-based applications such as the provision of ancillary services, lead to profitable consumer investments. Therefore, we conduct an extensive simulation study that is able to jointly capture these aspects. Our results show that, at current battery module prices, even optimal system configurations still do not lead to profitable investments into Li-Ion batteries if they are merely used as a buffer for solar energy. The first settings in which they will become profitable, as prices are further declining, will be larger households at locations with higher average levels of solar irradiance. If the batteries can be remote-controlled by an aggregator to provide overnight negative reserve, their profitability increases significantly. Full article

(This article belongs to the Special Issue Energy Efficient and Smart Cities)

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Review

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41 pages, 9324 KiB

Open AccessReview

Review of Control Techniques for HVAC Systems—Nonlinearity Approaches Based on Fuzzy Cognitive Maps

by Farinaz Behrooz, Norman Mariun, Mohammad Hamiruce Marhaban, Mohd Amran Mohd Radzi and Abdul Rahman Ramli

Energies 2018, 11(3), 495; https://doi.org/10.3390/en11030495 - 27 Feb 2018

Cited by 139 | Viewed by 10244

Abstract

Heating, Ventilating, and Air Conditioning (HVAC) systems are the major energy-consuming devices in buildings. Nowadays, due to the high demand for HVAC system installation in buildings, designing an effective controller in order to decrease the energy consumption of the devices while meeting the thermal comfort demands in buildings are the most important goals of control designers. The purpose of this article is to investigate the different control methods for Heating, Ventilating, and Air Conditioning and Refrigeration (HVAC & R) systems. The advantages and disadvantages of each control method are discussed and finally the Fuzzy Cognitive Map (FCM) method is introduced as a new strategy for HVAC systems. The FCM method is an intelligent and advanced control technique to address the nonlinearity, Multiple-Input and Multiple-Output (MIMO), complexity and coupling effect features of the systems. The significance of this method and improvements by this method are compared with other methods. Full article

(This article belongs to the Special Issue Energy Efficient and Smart Cities)

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Other

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17 pages, 4023 KiB

Open AccessConcept Paper

Building “with the Systems” vs. Building “in the System” of IMS Open Technology of Prefabricated Construction: Challenges for New “Infill” Industry for Massive Housing Retrofitting

by Jelena Nikolic

Energies 2018, 11(5), 1128; https://doi.org/10.3390/en11051128 - 03 May 2018

Cited by 8 | Viewed by 4548

Abstract

Post-war industrialized housing between 1955 and 1985 in Belgrade and its special form of integrated prefabrication has been analyzed with a strong interest in transformation capacity of industrialized building model (IBM) on different technical levels. Research field is massive housing up to 23 floors, 400 dwellings per building and different housing layouts—to be evaluated for potential retrofitting at the dwelling level. IBM for massive housing built with IMS construction technology represents an integration of systems’ components into hierarchy assemblies by simple joints. IMS Building Technology by IMS Institute is the system for high-rise structures with prefabricated elements of the skeleton. In order to assess the current situation regarding the selection and implementation of energy savings measures and the role of industrialized technology in supporting the rehabilitation of post-war housing in Belgrade—building configuration model and IMS construction technology has been analyzed, providing in-depth information on the way building components and systems are put together into IBM. In which way retrofit may be approached? IBM is represented with graph model (GM) diagram to describe a number of value-added processes according to independent systems/components and flexible connections. This paper highlights the technological aspects of “open” prefabrication industry and building with the systems that should be assessed in the future retrofitting of massive housing based on industrialization and energy efficiency. The paper proposes an IBM that provides concrete description of massive housing buildings, the requirements for information to be provided to approving refurbishment processes. The research also addresses both: challenges as well as opportunities for advancing Building Information Modeling (BIM) standards in off-site re-construction of massive housing with new “infill” industry. Full article

(This article belongs to the Special Issue Energy Efficient and Smart Cities)

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