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Special Issue "Selected Papers from SDEWES 2017: The 12th Conference on Sustainable Development of Energy, Water and Environment Systems"

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

Deadline for manuscript submissions: closed (30 April 2018)

Special Issue Editors

Guest Editor
Prof. Dr. Neven Duić

Professor, University of Zagreb, Croatia
Website | E-Mail
Interests: energy planning of energy systems with high penetration of renewables; sustainable communities; energy policy; energy economics; mitigation of climate change; energy efficiency and combustion engineering.
Guest Editor
Prof. Dr. Xiliang Zhang

Institute of Energy, Environment & Economy, China Automotive Energy Research Center, Tsinghua University, Beijing,China
E-Mail
Interests: energy systems analysis; energy and climate policy; renewable energy; transport
Guest Editor
Prof. Dr. Mário M. G. Costa

IDMEC, Instituto Superior Técnico, Universidade de Lisboa, Lisboa, Portugal
Website | E-Mail
Interests: conventional and alternative fuels; particulate and aerosol formation and abatement; heterogeneous processes; advances in diagnostic methods in combustion; gas turbines; small- and large-scale stationary combustion and power generation; new concepts
Guest Editor
Prof. Dr. Qiuwang Wang

International Joint Research Lab of Thermal Science and Engineering, Xi'an Jiaotong University, Xianning West Road28#, Xi'an, Shaanxi, 710049, China
Website | E-Mail
Interests: heat transfer enhancement; high-temperature/high-pressure heat transfer; transport phenomena in porous media, numerical simulation, prediction & optimization
Guest Editor
Prof. Dr. Francesco Calise

Department of Industrial Engineering, University of Naples Federico II, 80125 Naples, Italy
Website | E-Mail
Phone: +39 0817682301
Fax: +39 0812390364
Interests: fuel cells; solar energy; polygeneration systems; solar cooling; organic Rankine cycle; geothermal energy; solar thermal; solar heating and cooling; photovoltaic/thermal collectors; building dynamic simulations; heating, ventilating, and air-conditioning (HVAC) systems; cogeneration; energy efficiency; desalination

Special Issue Information

Dear Colleagues,

The 12th Conference on Sustainable Development of Energy, Water and Environment SystemsSDEWES Conference, held in Dubrovnik, in 2017, was dedicated to the improvement and dissemination of knowledge on methods, policies and technologies for increasing the sustainability of development by de-coupling growth from natural resources and replacing them with knowledge based economy, taking into account its economic, environmental and social pillars.

One of the main issues of the coming decades is to improve efficiencies by integrating various life supporting systems, using waste from one, as resource in other, and in exact moment when it is beneficial to all, integrating electricity, heating, cooling, transport, water, buildings, waste, wastewater, industry, forestry and agriculture systems. Sustainability being also a perfect field for interdisciplinary and multi-cultural evaluation of complex system, the SDEWES Conference has become a significant venue for researchers in those areas to meet, and originate, discuss, share, and disseminate new ideas. 

Prof. Dr. Neven Duić

Prof. Dr. Xiliang Zhang

Prof. Dr. Mário Costa

Prof. Dr. Qiuwang Wang

Prof. Dr. Francesco Calise

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. Energies is an international peer-reviewed open access monthly 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 1600 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

  • Sustainability comparisons and measurements
  • Smart energy systems
  • Energy policy
  • Water-energy nexus
  • Energy system analysis
  • Renewable energy resources
  • Primary energy resources
  • Renewable electricity generation systems
  • Thermal power plants
  • District heating and/or cooling
  • Advanced sustainable energy conversion systems
  • Renewable heat systems
  • Biofuels and biorefineries
  • Alternative fuels
  • Hybrid and electric vehicles
  • Water treatment for drinking water
  • Modelling for pollution avoidance and energy efficiency
  • Cogeneration, trigeneration, polygeneration
  • Energy storage
  • Electricity transmission and distribution
  • Gas security of supply
  • Energy efficiency in industry and mining
  • Energy efficient appliances
  • Energy efficiency in buildings
  • Energy markets

Published Papers (17 papers)

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Research

Open AccessArticle A Numerical Study of Small-Scale Longitudinal Heat Conduction in Plate Heat Exchangers
Energies 2018, 11(7), 1727; https://doi.org/10.3390/en11071727
Received: 22 May 2018 / Revised: 14 June 2018 / Accepted: 22 June 2018 / Published: 2 July 2018
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Abstract
Longitudinal heat conduction has a significant effect on the heat transfer performance of plate heat exchangers, but longitudinal heat conduction is usually neglected in numerical studies and the thermal design of a heat exchanger. In this paper, heat transfer models with and without
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Longitudinal heat conduction has a significant effect on the heat transfer performance of plate heat exchangers, but longitudinal heat conduction is usually neglected in numerical studies and the thermal design of a heat exchanger. In this paper, heat transfer models with and without longitudinal heat conduction are proposed to analyze the effect of small-scale longitudinal heat conduction in a plate heat exchanger. The performance of small-scale longitudinal heat conduction is illustrated by temperature and heat flux contours in the heat transfer models with and without longitudinal heat conduction. The results show that small-scale longitudinal heat conduction occurs in the plate and a more uniform temperature profile of the plate is obtained due to small-scale longitudinal heat conduction. In balanced flow, the contributions of longitudinal heat conduction for counter-flow, cross-flow and parallel-flow plate heat exchangers are −3.15%, −0.09% and 0, respectively, whereas, for the respective unbalanced flows they are evaluated to be −1.73%, 0.53% and 0.05%, respectively. Moreover, it is observed that small-scale longitudinal heat conduction in plates is influenced by the thermal conductivity of the plate. The higher the thermal conductivity, the larger is the reduction of thermal performance. The contribution of longitudinal heat conduction varies from −0.54% to −4.01%. Full article
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Open AccessArticle Design of a Path-Tracking Steering Controller for Autonomous Vehicles
Energies 2018, 11(6), 1451; https://doi.org/10.3390/en11061451
Received: 25 April 2018 / Revised: 29 May 2018 / Accepted: 1 June 2018 / Published: 4 June 2018
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Abstract
This paper presents a linearization method for the vehicle and tire models under the model predictive control (MPC) scheme, and proposes a linear model-based MPC path-tracking steering controller for autonomous vehicles. The steering controller is designed to minimize lateral path-tracking deviation at high
[...] Read more.
This paper presents a linearization method for the vehicle and tire models under the model predictive control (MPC) scheme, and proposes a linear model-based MPC path-tracking steering controller for autonomous vehicles. The steering controller is designed to minimize lateral path-tracking deviation at high speeds. The vehicle model is linearized by a sequence of supposed steering angles, which are obtained by assuming the vehicle can reach the desired path at the end of the MPC prediction horizon and stay in a steady-state condition. The lateral force of the front tire is directly used as the control input of the model, and the rear tire’s lateral force is linearized by an equivalent cornering stiffness. The course-direction deviation, which is the angle between the velocity vector and the path heading, is chosen as a control reference state. The linearization model is validated through the simulation, and the results show high prediction accuracy even in regions of large steering angle. This steering controller is tested through simulations on the CarSim-Simulink platform (R2013b, MathWorks, Natick, MA, USA), showing the improved performance of the present controller at high speeds. Full article
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Open AccessArticle Explorative Multidimensional Analysis for Energy Efficiency: DataViz versus Clustering Algorithms
Energies 2018, 11(5), 1312; https://doi.org/10.3390/en11051312
Received: 10 April 2018 / Revised: 8 May 2018 / Accepted: 10 May 2018 / Published: 21 May 2018
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Abstract
We propose a simple tool to help the energy management of a large building stock defining clusters of buildings with the same function, setting alert thresholds for each cluster, and easily recognizing outliers. The objective is to enable a building management system to
[...] Read more.
We propose a simple tool to help the energy management of a large building stock defining clusters of buildings with the same function, setting alert thresholds for each cluster, and easily recognizing outliers. The objective is to enable a building management system to be used for detection of abnormal energy use. We start reviewing energy performance indicators, and how they feed into data visualization (DataViz) tools for a large building stock, especially for university campuses. After a brief presentation of the University of Turin’s building stock which represents our case study, we perform an explorative analysis based on the Multidimensional Detective approach by Inselberg, using the Scatter Plot Matrix and the Parallel Coordinates methods. The k-means clustering algorithm is then applied on the same dataset to test the hypotheses made during the explorative analysis. Our results show that DataViz techniques provide quick and user-friendly solutions for the energy management of a large stock of buildings. In particular, they help identifying clusters of buildings and outliers and setting alert thresholds for various Energy Efficiency Indices. Full article
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Open AccessArticle Hydrogen Economy Model for Nearly Net-Zero Cities with Exergy Rationale and Energy-Water Nexus
Energies 2018, 11(5), 1226; https://doi.org/10.3390/en11051226
Received: 15 March 2018 / Revised: 29 April 2018 / Accepted: 2 May 2018 / Published: 10 May 2018
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Abstract
The energy base of urban settlements requires greater integration of renewable energy sources. This study presents a “hydrogen city” model with two cycles at the district and building levels. The main cycle comprises of hydrogen gas production, hydrogen storage, and a hydrogen distribution
[...] Read more.
The energy base of urban settlements requires greater integration of renewable energy sources. This study presents a “hydrogen city” model with two cycles at the district and building levels. The main cycle comprises of hydrogen gas production, hydrogen storage, and a hydrogen distribution network. The electrolysis of water is based on surplus power from wind turbines and third-generation solar photovoltaic thermal panels. Hydrogen is then used in central fuel cells to meet the power demand of urban infrastructure. Hydrogen-enriched biogas that is generated from city wastes supplements this approach. The second cycle is the hydrogen flow in each low-exergy building that is connected to the hydrogen distribution network to supply domestic fuel cells. Make-up water for fuel cells includes treated wastewater to complete an energy-water nexus. The analyses are supported by exergy-based evaluation metrics. The Rational Exergy Management Efficiency of the hydrogen city model can reach 0.80, which is above the value of conventional district energy systems, and represents related advantages for CO2 emission reductions. The option of incorporating low-enthalpy geothermal energy resources at about 80 °C to support the model is evaluated. The hydrogen city model is applied to a new settlement area with an expected 200,000 inhabitants to find that the proposed model can enable a nearly net-zero exergy district status. The results have implications for settlements using hydrogen energy towards meeting net-zero targets. Full article
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Open AccessArticle Portuguese Plan for Promoting Efficiency of Electricity End-Use: Policy, Methodology and Consumer Participation
Energies 2018, 11(5), 1137; https://doi.org/10.3390/en11051137
Received: 26 February 2018 / Revised: 4 April 2018 / Accepted: 25 April 2018 / Published: 3 May 2018
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Abstract
The Portuguese Electricity Demand-Side Efficiency Promotion Plan (PPEC) is a voluntary financial mechanism, under which several entities, among them electric utilities, may submit proposals of measures aiming at the reduction of electricity consumption or load management. It is one of the alternative options
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The Portuguese Electricity Demand-Side Efficiency Promotion Plan (PPEC) is a voluntary financial mechanism, under which several entities, among them electric utilities, may submit proposals of measures aiming at the reduction of electricity consumption or load management. It is one of the alternative options followed by the Portuguese government to the Energy Efficiency Obligations (EEO) stated in Article 7 of the EU Energy Efficiency Directive. A brief review is presented of the state of the implementation of Article 7 in EU. PPEC is one of the schemes that provide financial support to the implementation of measures whose results contribute to the commitments made under the Portuguese National Energy Efficiency Action Plan (NEEAP), the framework under which the alternatives to the EEO were designed. In the first edition of the PPEC, only three energy services were addressed, while, in the most recent PPEC edition, the sixth, measures addressed nine energy services. In addition, the co-funding by participating consumers and other agents has increased, raising the investment in energy efficiency from actors other than the program administrator. PPEC, although a voluntary mechanism, has proven to be a very competitive one, involving an increasing number of economic agents, measures and addressed energy services. Full article
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Open AccessArticle An Optimisation Study on Integrating and Incentivising Thermal Energy Storage (TES) in a Dwelling Energy System
Energies 2018, 11(5), 1095; https://doi.org/10.3390/en11051095
Received: 1 April 2018 / Revised: 20 April 2018 / Accepted: 25 April 2018 / Published: 29 April 2018
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Abstract
In spite of the benefits from thermal energy storage (TES) integration in dwellings, the penetration rate in Europe is 5%. Effective fiscal policies are necessary to accelerate deployment. However, there is currently no direct support for TES in buildings compared to support for
[...] Read more.
In spite of the benefits from thermal energy storage (TES) integration in dwellings, the penetration rate in Europe is 5%. Effective fiscal policies are necessary to accelerate deployment. However, there is currently no direct support for TES in buildings compared to support for electricity storage. This could be due to lack of evidence to support incentivisation. In this study, a novel systematic framework is developed to provide a case in support of TES incentivisation. The model determines the costs, CO2 emissions, dispatch strategy and sizes of technologies, and TES for a domestic user under policy neutral and policy intensive scenarios. The model is applied to different building types in the UK. The model is applied to a case study for a detached dwelling in the UK (floor area of 122 m2), where heat demand is satisfied by a boiler and electricity imported from the grid. Results show that under a policy neutral scenario, integrating a micro-Combined Heat and Power (CHP) reduces the primary energy demand by 11%, CO2 emissions by 21%, but with a 16 year payback. Additional benefits from TES integration can pay for the investment within the first 9 years, reducing to 3.5–6 years when the CO2 levy is accounted for. Under a policy intensive scenario (for example considering the Feed in Tariff (FIT)), primary energy demand and CO2 emissions reduce by 17 and 33% respectively with a 5 year payback. In this case, the additional benefits for TES integration can pay for the investment in TES within the first 2 years. The framework developed is a useful tool is determining the role TES in decarbonising domestic energy systems. Full article
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Open AccessFeature PaperArticle Numerical Simulation of Flow and Heat Transfer in Structured Packed Beds with Smooth or Dimpled Spheres at Low Channel to Particle Diameter Ratio
Energies 2018, 11(4), 937; https://doi.org/10.3390/en11040937
Received: 1 March 2018 / Revised: 4 April 2018 / Accepted: 10 April 2018 / Published: 15 April 2018
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Abstract
Packed beds are widely used in catalytic reactors or nuclear reactors. Reducing the pressure drop and improving the heat transfer performance of a packed bed is a common research aim. The dimpled structure has a complex influence on the flow and heat transfer
[...] Read more.
Packed beds are widely used in catalytic reactors or nuclear reactors. Reducing the pressure drop and improving the heat transfer performance of a packed bed is a common research aim. The dimpled structure has a complex influence on the flow and heat transfer characteristics. In the present study, the flow and heat transfer characteristics in structured packed beds with smooth or dimpled spheres are numerically investigated, where two different low channel to particle diameter ratios (N = 1.00 and N = 1.15) are considered. The pressure drop and the Nusselt number are obtained. The results show that, for N = 1.00, compared with the structured packed bed with smooth spheres, the structured packed bed with dimpled spheres has a lower pressure drop and little higher Nusselt number at 1500 < ReH < 14,000, exhibiting an improved overall heat transfer performance. However, for N = 1.15, the structured packed bed with dimpled spheres shows a much higher pressure drop, which dominantly affects the overall heat transfer performance, causing it to be weaker. Comparing the different channel to particle diameter ratios, we find that different configurations can result in: (i) completely different drag reduction effect; and (ii) relatively less influence on heat transfer enhancement. Full article
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Open AccessFeature PaperArticle From Problems to Potentials—The Urban Energy Transition of Gruž, Dubrovnik
Energies 2018, 11(4), 922; https://doi.org/10.3390/en11040922
Received: 4 March 2018 / Revised: 5 April 2018 / Accepted: 5 April 2018 / Published: 13 April 2018
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Abstract
In the challenge for a sustainable society, carbon-neutrality is a critical objective for all cities in the coming decades. In the EU City-zen project, academic partners collaborate to develop an urban energy transition methodology, which supports cities in making the energy transition to
[...] Read more.
In the challenge for a sustainable society, carbon-neutrality is a critical objective for all cities in the coming decades. In the EU City-zen project, academic partners collaborate to develop an urban energy transition methodology, which supports cities in making the energy transition to sustainable lifestyles and carbon neutrality. As part of the project, so-called Roadshows are organised in cities that wish to take the first step toward zero-energy living. Each Roadshow is methodologically composed to allow sustainability experts from across Europe to co-create designs, strategies and timelines with local stakeholders in order to reach this vital goal. Following a precursory investigative student workshop (the SWAT Studio), Dubrovnik was the third city to host the Roadshow in November 2016. During these events the characteristics of Dubrovnik, and the district of Gruž in particular, were systematically analysed, leading to useful insights into the current problems and potentials of the city. In close collaboration with local stakeholders, the team proposed a series of interventions, validated by the calculation of carbon emission, to help make Gruž, and in its wake the whole city of Dubrovnik, net zero energy and zero carbon. The vision presented to the inhabitants and its key city decision makers encompassed a path towards an attainable sustainable future. The strategies and solutions proposed for the Dubrovnik district of Gruž were able to reduce the current carbon sequestration compensation of 1200 hectares of forestland to only 67 hectares, an area achievable by urban reforestation projects. This paper presents the City-zen methodology of urban energy transition and that of the City-zen Roadshow, the analysis of the city of Dubrovnik, proposed interventions and the carbon impact, as calculated by means of the carbon accounting method discussed in the paper. Full article
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Open AccessArticle Comparison of the Energy Conversion Efficiency of a Solar Chimney and a Solar PV-Powered Fan for Ventilation Applications
Energies 2018, 11(4), 912; https://doi.org/10.3390/en11040912
Received: 16 February 2018 / Revised: 4 April 2018 / Accepted: 8 April 2018 / Published: 12 April 2018
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Abstract
A study into the performance of a solar chimney and a solar photovoltaic (PV)-powered fan for ventilation applications was carried out using numerical simulations. The performance of the solar chimney was compared with that of a direct current (DC) fan powered by a
[...] Read more.
A study into the performance of a solar chimney and a solar photovoltaic (PV)-powered fan for ventilation applications was carried out using numerical simulations. The performance of the solar chimney was compared with that of a direct current (DC) fan powered by a solar PV panel. The comparison was carried out using the same area of the irradiated surface—the area of the solar absorber plate in the case of the solar chimney and the area of the solar panel in the case of the photovoltaic-powered fan. The two studied cases were compared under various solar radiation intensities of incident solar radiation. The results indicate that the PV-powered fans significantly outperform solar chimneys in terms of converting solar energy into the kinetic energy of air motion. Moreover, ventilation with PV-powered fans offers more flexibility in the arrangement of the ventilation system and also better control of the air flow rates in the case of battery storage. Full article
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Open AccessArticle On the Effects of Variation of Thermal Conductivity in Buildings in the Italian Construction Sector
Energies 2018, 11(4), 872; https://doi.org/10.3390/en11040872
Received: 10 February 2018 / Revised: 30 March 2018 / Accepted: 5 April 2018 / Published: 9 April 2018
Cited by 2 | PDF Full-text (13018 KB) | HTML Full-text | XML Full-text
Abstract
Stationary and dynamic heat and mass transfer analyses of building components are an essential part of energy efficient design of new and retrofitted buildings. Generally, a single constant thermal conductivity value is assumed for each material layer in construction components. However, the variability
[...] Read more.
Stationary and dynamic heat and mass transfer analyses of building components are an essential part of energy efficient design of new and retrofitted buildings. Generally, a single constant thermal conductivity value is assumed for each material layer in construction components. However, the variability of thermal conductivity may depend on many factors; temperature and moisture content are among the most relevant ones. A linear temperature dependence of thermal conductivity has been found experimentally for materials made of inorganic fibers such as rockwool or fiberglass, showing lower thermal conductivities at lower temperatures. On the contrary, a nonlinear temperature dependence has been found for foamed insulation materials like polyisocyanurate, with a significant deviation from linear behavior. For this reason, thermal conductivity assumptions used in thermal calculations of construction components and in whole-building performance simulations have to be critically questioned. This study aims to evaluate how temperature affects thermal conductivity of materials in building components such as exterior walls and flat roofs in different climate conditions. Therefore, experimental conductivities measured for four common insulation materials have been used as a basis to simulate the behavior of typical construction components in three different Italian climate conditions, corresponding to the cities of Turin, Rome, and Palermo. Full article
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Open AccessArticle Construction of Biodigesters to Optimize the Production of Biogas from Anaerobic Co-Digestion of Food Waste and Sewage
Energies 2018, 11(4), 870; https://doi.org/10.3390/en11040870
Received: 22 February 2018 / Revised: 26 March 2018 / Accepted: 27 March 2018 / Published: 9 April 2018
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Abstract
The objective of this study was to build and develop anaerobic biodigesters for optimization of biogas production using food waste (FW) and sewage (S) co-digestion from a wastewater treatment plant (WWTP). The biodigesters operated with different mixtures and in mesophilic phase (37 °C).
[...] Read more.
The objective of this study was to build and develop anaerobic biodigesters for optimization of biogas production using food waste (FW) and sewage (S) co-digestion from a wastewater treatment plant (WWTP). The biodigesters operated with different mixtures and in mesophilic phase (37 °C). During the 60 days of experiments, all control and monitoring parameters of the biodigesters necessary for biogas production were tested and evaluated. The biodigester containing FW, S and anaerobic sludge presented the biggest reduction of organic matter, expressed with removal of 88.3% TVS (total volatile solid) and 84.7% COD (chemical oxygen demand) the biggest biogas production (63 L) and the highest methane percentage (95%). Specific methane production was 0.299 LCH4/gVS and removed. The use of biodigesters to produce biogas through anaerobic digestion may play an important role in local economies due to the opportunity to produce a renewable fuel from organic waste and also as an alternative to waste treatment. Finally, the embedded control and automation system was simple, effective, and robust, and the supervisory software was efficient in all aspects defined at its conception. Full article
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Open AccessArticle The Key Role of the Vector Optimization Algorithm and Robust Design Approach for the Design of Polygeneration Systems
Energies 2018, 11(4), 821; https://doi.org/10.3390/en11040821
Received: 19 February 2018 / Revised: 26 March 2018 / Accepted: 30 March 2018 / Published: 2 April 2018
Cited by 1 | PDF Full-text (6940 KB) | HTML Full-text | XML Full-text
Abstract
In recent decades, growing concerns about global warming and climate change effects have led to specific directives, especially in Europe, promoting the use of primary energy-saving techniques and renewable energy systems. The increasingly stringent requirements for carbon dioxide reduction have led to a
[...] Read more.
In recent decades, growing concerns about global warming and climate change effects have led to specific directives, especially in Europe, promoting the use of primary energy-saving techniques and renewable energy systems. The increasingly stringent requirements for carbon dioxide reduction have led to a more widespread adoption of distributed energy systems. In particular, besides renewable energy systems for power generation, one of the most effective techniques used to face the energy-saving challenges has been the adoption of polygeneration plants for combined heating, cooling, and electricity generation. This technique offers the possibility to achieve a considerable enhancement in energy and cost savings as well as a simultaneous reduction of greenhouse gas emissions. However, the use of small-scale polygeneration systems does not ensure the achievement of mandatory, but sometimes conflicting, aims without the proper sizing and operation of the plant. This paper is focused on a methodology based on vector optimization algorithms and developed by the authors for the identification of optimal polygeneration plant solutions. To this aim, a specific calculation algorithm for the study of cogeneration systems has also been developed. This paper provides, after a detailed description of the proposed methodology, some specific applications to the study of combined heat and power (CHP) and organic Rankine cycle (ORC) plants, thus highlighting the potential of the proposed techniques and the main results achieved. Full article
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Open AccessArticle Technical Aspects and Energy Effects of Waste Heat Recovery from District Heating Boiler Slag
Energies 2018, 11(4), 796; https://doi.org/10.3390/en11040796
Received: 18 February 2018 / Revised: 21 March 2018 / Accepted: 27 March 2018 / Published: 30 March 2018
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Abstract
Coal continues to dominate in the structure of the heat production system in some European countries. Coal-fired boilers in district heating and power generation systems are accompanied by the formation of large quantities of slag and ash. Due to considerable high temperature, slag
[...] Read more.
Coal continues to dominate in the structure of the heat production system in some European countries. Coal-fired boilers in district heating and power generation systems are accompanied by the formation of large quantities of slag and ash. Due to considerable high temperature, slag may be used as a source of waste energy. In this study, the technical possibilities of recovery slag’s physical enthalpy from grate-fired district heating boiler of 45 MW thermal capacity are analyzed. The aim of the work is to estimate the waste energy potential of the slag in analyzed boiler and proposition of the heat recovery system. The construction and design of the existing deslagging system was examined. Studies have shown that high water temperature accelerates system wear. Recovering heat from this system decreases the water temperature, which extends the trouble-free working time. The slag parameters were determined, including the temperature at the outlet of the boiler and the temperature after leaving the slag water tub. The annual amount of heat regenerative potential was estimated. On the basis of the research, the authors propose a waste heat recovery facility with high temperature R134a heat pump system. The result of the conducted research is that the proposed heat pump provides energy savings that are worth considering by recovering from 58.8% to 88.0% of energy slag potential. Full article
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Open AccessArticle Novel Concept of an Installation for Sustainable Thermal Utilization of Sewage Sludge
Energies 2018, 11(4), 748; https://doi.org/10.3390/en11040748
Received: 16 February 2018 / Revised: 19 March 2018 / Accepted: 22 March 2018 / Published: 26 March 2018
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Abstract
This study proposes an innovative installation concept for the sustainable utilization of sewage sludge. The aim of the study is to prove that existing devices and technologies allow construction of such an installation by integration of a dryer, torrefaction reactor and gasifier with
[...] Read more.
This study proposes an innovative installation concept for the sustainable utilization of sewage sludge. The aim of the study is to prove that existing devices and technologies allow construction of such an installation by integration of a dryer, torrefaction reactor and gasifier with engine, thus maximizing recovery of the waste heat by the installation. This study also presents the results of drying tests, performed at a commercial scale paddle dryer as well as detailed analysis of the torrefaction process of dried sewage sludge. Both tests aim to identify potential problems that could occur during the operation. The scarce literature studies published so far on the torrefaction of sewage sludge presents results from batch reactors, thus giving very limited data of the composition of the torgas. This study aims to cover that gap by presenting results from the torrefaction of sewage sludge in a continuously working, laboratory scale, isothermal rotary reactor. The study confirmed the feasibility of a self-sustaining installation of thermal utilization of sewage sludge using low quality heat. Performed study pointed out the most favorable way to use limited amounts of high temperature heat. Plasma gasification of the torrefied sewage sludge has been identified that requires further studies. Full article
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Open AccessFeature PaperArticle Development and Validation of 3D-CFD Injection and Combustion Models for Dual Fuel Combustion in Diesel Ignited Large Gas Engines
Energies 2018, 11(3), 643; https://doi.org/10.3390/en11030643
Received: 27 February 2018 / Revised: 9 March 2018 / Accepted: 11 March 2018 / Published: 14 March 2018
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Abstract
This paper focuses on improving the 3D-Computational Fluid Dynamics (CFD) modeling of diesel ignited gas engines, with an emphasis on injection and combustion modeling. The challenges of modeling are stated and possible solutions are provided. A specific approach for modeling injection is proposed
[...] Read more.
This paper focuses on improving the 3D-Computational Fluid Dynamics (CFD) modeling of diesel ignited gas engines, with an emphasis on injection and combustion modeling. The challenges of modeling are stated and possible solutions are provided. A specific approach for modeling injection is proposed that improves the modeling of the ballistic region of the needle lift. Experimental results from an inert spray chamber are used for model validation. Two-stage ignition methods are described along with improvements in ignition delay modeling of the diesel ignited gas engine. The improved models are used in the Extended Coherent Flame Model with the 3 Zones approach (ECFM-3Z). The predictive capability of the models is investigated using data from single cylinder engine (SCE) tests conducted at the Large Engines Competence Center (LEC). The results are discussed and further steps for development are identified. Full article
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Open AccessArticle Co-Combustion of Low-Rank Coal with Woody Biomass and Miscanthus: An Experimental Study
Energies 2018, 11(3), 601; https://doi.org/10.3390/en11030601
Received: 9 February 2018 / Revised: 19 February 2018 / Accepted: 23 February 2018 / Published: 9 March 2018
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Abstract
This paper presents a research on ash-related problems and emissions during co-firing low-rank Bosnian coals with different kinds of biomass; in this case woody sawdust and herbaceous energy crops Miscanthus. An entrained-flow drop tube furnace was used for the tests, varying fuel portions
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This paper presents a research on ash-related problems and emissions during co-firing low-rank Bosnian coals with different kinds of biomass; in this case woody sawdust and herbaceous energy crops Miscanthus. An entrained-flow drop tube furnace was used for the tests, varying fuel portions at a high co-firing ratio up to 30%wt woody sawdust and 10%wt Miscanthus in a fuel blend. The tests were supposed to optimize the process temperature, air distribution (including OFA) and fuel distributions (reburning) as function of SO2 and NOx emissions as well as efficiency of combustion process estimated through the ash deposits behaviors, CO emissions and unburnt. The results for 12 co-firing fuel combinations impose a reasonable expectation that the coal/biomass/Miscanthus blends could be successfully run under certain conditions not producing any serious ash-related problems. SO2 emissions were slightly higher when higher content of woody biomass was used. Oppositely, higher Miscanthus percentage in the fuel mix slightly decreases SO2 emissions. NOx emissions generally decrease with an increase of biomass co-firing rate. The study suggests that co-firing Bosnian coals with woody sawdust and Miscanthus shows promise at higher co-firing ratios for pulverized combustion, giving some directions for further works in co-firing similar multi-fuel combinations. Full article
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Open AccessArticle Evaluation of Excess Heat Utilization in District Heating Systems by Implementing Levelized Cost of Excess Heat
Energies 2018, 11(3), 575; https://doi.org/10.3390/en11030575
Received: 16 February 2018 / Revised: 1 March 2018 / Accepted: 5 March 2018 / Published: 7 March 2018
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Abstract
District heating plays a key role in achieving high primary energy savings and the reduction of the overall environmental impact of the energy sector. This was recently recognized by the European Commission, which emphasizes the importance of these systems, especially when integrated with
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District heating plays a key role in achieving high primary energy savings and the reduction of the overall environmental impact of the energy sector. This was recently recognized by the European Commission, which emphasizes the importance of these systems, especially when integrated with renewable energy sources, like solar, biomass, geothermal, etc. On the other hand, high amounts of heat are currently being wasted in the industry sector, which causes low energy efficiency of these processes. This excess heat can be utilized and transported to the final customer by a distribution network. The main goal of this research was to calculate the potential for excess heat utilization in district heating systems by implementing the levelized cost of excess heat method. Additionally, this paper proves the economic and environmental benefits of switching from individual heating solutions to a district heating system. This was done by using the QGIS software. The variation of different relevant parameters was taken into account in the sensitivity analysis. Therefore, the final result was the determination of the maximum potential distance of the excess heat source from the demand, for different available heat supplies, costs of pipes, and excess heat prices. Full article
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