Special Issue "Urban Generation of Renewable Energy and Energy Saving in Cities"

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

Deadline for manuscript submissions: closed (28 February 2018).

Special Issue Editor

Dr. Francisco Manzano Agugliaro
Website SciProfiles
Guest Editor

Special Issue Information

Dear Colleagues,

The world population will probably exceed eleven billion by the end of the century. Most of this population lives in urban areas. Our quickly-changing world faces great challenges when it comes to the sustainable provision of energy. Despite its huge potential for increasing sustainability, the use of renewable energy in urban places is still scarce. This perspective highlights the urban contribution to renewable energy, which will be essential for the welfare of a growing urban population.

This Special Issue aims to advance the contribution of Urban Generation of Renewable Energy and Energy Saving in order to achieve more sustainable cities. This Special Issue seeks contributions spanning a broad range of topics related, but are not limited to:

  •  Stand-alone PV solar collector and CSP in urban uses
  •  Effects of dust or sand on the materials used in solar systems
  •  The use of rooftops for energy generation
  •  Energy conversion from urban biomass or residues
  •  Energy management for sewage water
  •  Bioclimatic architecture and green buildings
  •  Public and private urban energy saving
  •  Policy for urban energy saving
  •  Electric meters

Prof. Dr. Francisco Manzano Agugliaro
Guest Editor

Manuscript Submission Information

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

Keywords

  • energy saving
  • CSP
  • biomass
  • sustainable cities
  • indoor and outdoor lighting
  • Bioclimatic architecture

Published Papers (6 papers)

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Research

Open AccessArticle
Energy Saving in an ETC Solar System to Produce High Temperature Water
Energies 2018, 11(4), 840; https://doi.org/10.3390/en11040840 - 04 Apr 2018
Cited by 1
Abstract
The use of solar water heating systems (SWHS) based on evacuated tube collectors (ETC) has experienced rapid growth in the residential sector. In contrast, the implementation of these systems in the industrial sector is very limited, due in part to the demand of [...] Read more.
The use of solar water heating systems (SWHS) based on evacuated tube collectors (ETC) has experienced rapid growth in the residential sector. In contrast, the implementation of these systems in the industrial sector is very limited, due in part to the demand of a higher temperature in water. Taking into account that the final energy of the industrial sector is similar to the residential sector, to increase the generation of renewable energy and energy saving in cities, efforts in this sector should be redoubled. Therefore, the present work characterises the behaviour of a SWHS-ETC with active circulation to produce hot water at 90 °C, determining its performance, energy saving and profitability in different scenarios in Europe. The annual energy savings generated by the SWHS Range between 741 and 435 kWh m−2 (reduction of emissions between 215 and 88 kg CO2 m−2). The results of the analysis of profitability, studying the variation of the conventional energy price, the cost of the investment, the useful life and the energy supplied, in thousands of scenarios, are a valuable tool for correct decision making, as they can be of great utility to increase the implementation of these systems in the industrial sector. Full article
(This article belongs to the Special Issue Urban Generation of Renewable Energy and Energy Saving in Cities)
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Open AccessArticle
Evaluation of Uniformity and Glare Improvement with Low Energy Efficiency Losses in Street Lighting LED Luminaires Using Laser-Sintered Polyamide-Based Diffuse Covers
Energies 2018, 11(4), 816; https://doi.org/10.3390/en11040816 - 02 Apr 2018
Cited by 6
Abstract
Energy saving in street lighting is garnering more interest and has become a priority in municipal management. Therefore, LED luminaires are gradually becoming prevalent in our cities. Beyond their energy/economic saving potential, quality in public lighting installations concerns aspects such as uniformity and [...] Read more.
Energy saving in street lighting is garnering more interest and has become a priority in municipal management. Therefore, LED luminaires are gradually becoming prevalent in our cities. Beyond their energy/economic saving potential, quality in public lighting installations concerns aspects such as uniformity and glare which must be maintained if not improved in any installation renewal project using this technology. The high light intensity generated in a discrete point in LED packages and its directional nature result in significant deficiencies in these last two parameters. To soften these effects, translucent covers are being used as one of the most common solutions with the drawback of significant light intensity losses. The objective of this paper is to evaluate the behavior of LED luminaire’s polyamide-based optical covers manufactured with a laser-sintered process. These are designed to improve glare and uniformity output, to minimize light output reductions, and to be industrially manufactured with no increment of cost for their lighting equipment compared to conventional transparent polycarbonate solutions. A laboratory and field lighting test study has been applied to different covers with the same LED lamp and luminaire to compare the performance of three different solutions built with different polymeric materials and with different light transmission surface textures. The photometric results have been observed and discussed to demonstrate the ability to significantly improve the lighting performance of LED luminaires—illuminance and uniformity levels and discomfort and disability glare indexes— using an improved optic cover. Full article
(This article belongs to the Special Issue Urban Generation of Renewable Energy and Energy Saving in Cities)
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Open AccessArticle
Solar Reflector Materials Degradation Due to the Sand Deposited on the Backside Protective Paints
Energies 2018, 11(4), 808; https://doi.org/10.3390/en11040808 - 31 Mar 2018
Cited by 5
Abstract
Concentrating solar power (CSP) technologies are foreseen to be a crucial actor in the future renewable energy mix. Soil accumulation on the optical surfaces of CSP plants involves significant expenses of the operation and maintenance activities because a high cleanliness level is required [...] Read more.
Concentrating solar power (CSP) technologies are foreseen to be a crucial actor in the future renewable energy mix. Soil accumulation on the optical surfaces of CSP plants involves significant expenses of the operation and maintenance activities because a high cleanliness level is required to achieve proper plant revenues. Normally, only the front side of the solar reflectors is cleaned to reflect the maximum possible amount of direct solar radiation towards the receiver. However, soil deposited on the backside of the reflector could provoke degradation and might need to be considered in the cleaning strategy. As this possible degradation has never been studied, this work is dedicated to assess if the backside of reflectors should be regularly cleaned. The influence of the sand in the possible paint degradation depends on its chemical composition and the weather conditions. Therefore, several climatic conditions of artificially soiled reflector samples with different types of sand were simulated in accelerated aging tests. Concerning the results obtained, the ambient conditions simulated by the damp heat and thermal cycling tests were the only ones that produced a significant degradation of the backside paints. Also, the sand from Ouarzazate was responsible for higher deterioration. Full article
(This article belongs to the Special Issue Urban Generation of Renewable Energy and Energy Saving in Cities)
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Open AccessArticle
Renewable Energy in Urban Areas: Worldwide Research Trends
Energies 2018, 11(3), 577; https://doi.org/10.3390/en11030577 - 07 Mar 2018
Cited by 15
Abstract
This study aims to highlight the contribution made by different international institutions in the field of urban generation of renewable energy, as a key element to achieve sustainability. This has been possible through the use of the Scopus Elsevier database, and the application [...] Read more.
This study aims to highlight the contribution made by different international institutions in the field of urban generation of renewable energy, as a key element to achieve sustainability. This has been possible through the use of the Scopus Elsevier database, and the application of bibliometric techniques through which the articles content published from 1977 to 2017 has been analysed. The results shown by Scopus (e.g., journal articles and conferences proceedings) have been taken into account for further analysis by using the following search pattern (TITLE-ABS-KEY ({Renewable energy} AND ({urban} OR ({cit*})). In order to carry out this study, key features of the publications have been taken into consideration, such as type of document, language, thematic area, type of publication, and keywords. As far as keywords are concerned, renewable energy, sustainability, sustainable development, urban areas, city, and energy efficiency, have been the most frequently used. The results found have been broken down both geographically and by institution, showing that China, the United States, the United Kingdom, Italy, Germany and India are the main research countries and Chinese Academy of Sciences, Ministry of Education China and Tsinghua University the major contributing institutes. With regard to the categories, Energy, Environmental Sciences, and Engineering are positioned as the most active categories. The scientific community agrees that the study of the renewable energy generation in cities is of vital importance to achieve more sustainable cities, and for the welfare of a growing urban population. Moreover, this is in line with the energy policies adopted by most of developed countries in order to mitigate climate change effects. Full article
(This article belongs to the Special Issue Urban Generation of Renewable Energy and Energy Saving in Cities)
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Open AccessFeature PaperArticle
Optimization of the Transesterification of Waste Cooking Oil with Mg-Al Hydrotalcite Using Response Surface Methodology
Energies 2018, 11(2), 302; https://doi.org/10.3390/en11020302 - 30 Jan 2018
Cited by 6
Abstract
Nowadays, biodiesel has become a very promising alternative to fossil diesel fuel, regarding environmental concerns and fuel resource depletion. Biodiesel is usually produced through homogeneous or heterogeneous transesterification of different fatty raw materials. Although main research has been carried out with homogenous catalysts, [...] Read more.
Nowadays, biodiesel has become a very promising alternative to fossil diesel fuel, regarding environmental concerns and fuel resource depletion. Biodiesel is usually produced through homogeneous or heterogeneous transesterification of different fatty raw materials. Although main research has been carried out with homogenous catalysts, heterogeneous catalysts may be of interest due to ease of recovery and recycling, as well as readiness for continuous processing. In this work, calcined Mg-Al hydrotalcite (HT) was used for the heterogeneous transesterification of waste cooking oil. Three reaction parameters, namely, reaction time, amount of catalyst, and methanol-to-oil molar ratio, were optimized by means of Response Surface Methodology (RSM) at constant temperature (65 °C), using a Box-Behnken design. Optimal fatty acid methyl ester (FAME) content (86.23% w/w FAME/sample) was predicted by the model with an R-squared value of 98.45%, using 3.39 g of HT (8.5% w/w oil) and an 8:1 methanol-oil molar ratio, for a duration of 3.12 h. It was observed that calcination of HT, while avoiding the previous washing step, allowed the presence of chemical species that enhanced the effect of the catalyst. It can be concluded from this field trial that calcined and nonwashed Mg-Al hydrotalcite may be considered an effective basic catalyst for the production of biodiesel from waste cooking oil. Also, RSM proved to be a useful tool for predicting biodiesel yield. Full article
(This article belongs to the Special Issue Urban Generation of Renewable Energy and Energy Saving in Cities)
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Open AccessArticle
Stand-Alone Photovoltaic System Assessment in Warmer Urban Areas in Mexico
Energies 2018, 11(2), 284; https://doi.org/10.3390/en11020284 - 24 Jan 2018
Cited by 10
Abstract
The aim of this study is to examine the possibility of using a stand-alone photovoltaic system (SAPVS) for electricity generation in urban areas in Southern Mexico. In Mexico, an urban area is defined as an area where more than 2500 inhabitants live. Due [...] Read more.
The aim of this study is to examine the possibility of using a stand-alone photovoltaic system (SAPVS) for electricity generation in urban areas in Southern Mexico. In Mexico, an urban area is defined as an area where more than 2500 inhabitants live. Due to constant migration from the countryside to the cities, the number of inhabitants of urban localities has been increasing. Global horizontal irradiation (GHI) data were recorded every 10 min during 2014–2016 in Coatzacoalcos in the state of Veracruz located on 18°08′09″ N and 94°27′48″ W. In this study, batteries represented 77% of the total cost, 12 PV panels of 310 W could export 5.41 MWh to the grid, and an inverter with an integrated controller and charger was selected, which decreased the initial cost. The city of Coatzacoalcos was chosen because the average annual temperature is 28°, with an average relative humidity of 75% and an average irradiance of 5.3 kWh/m2/day. An emission factor 0.505 tCO2/MWh of greenhouse gases (GHG) were obtained, based on the power system, the reduction of net annual GHG would be 11 tCO2 and a financial revenue of 36.951 × 103 $/tCO2 would be obtained. Financial parameters such as a 36.3% Internal Rate Return (IRR) and 3.4 years payback show the financial viability of this investment. SAPVSs in urban areas in Mexico could be a benefit as long as housing has a high consumption of electricity. Full article
(This article belongs to the Special Issue Urban Generation of Renewable Energy and Energy Saving in Cities)
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