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A special issue of Clean Technologies (ISSN 2571-8797).

Deadline for manuscript submissions: closed (15 December 2020) | Viewed by 79587

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Special Issue Editor

Prof. Dr. Patricia Luis Alconero

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Guest Editor

Materials & Process Engineering, UCLouvain, Place Sainte Barbe 2, 1348 Louvain-la-Neuve, Belgium
Interests: sustainability; chemical engineering; process intensification; membrane technology; CO₂ capture; applied thermodynamics; life cycle assessment
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear colleagues,

Technological development and societal transformation are essential to face current challenges and achieve the Sustainable Development Goals. Researchers and technology developers thus play a critical role in providing novel sustainable solutions to reduce energy consumption, environmental pollution, and the use of water and nonrenewable resources. Clean Technologies is an international journal that has been established to show the most promising advances in sustainable technology. In this Special Issue, “Feature Papers”, we aim at outstanding contributions in the main fields covered by the journal:

Chemical and biochemical engineering;
Product and process engineering;
Membrane technology;
Environmental technology for treatment of wastewater, flue gases and solid waste;
Zero-waste technology;
CO₂ capture and (re)utilization technologies;
Green chemistry;
Cleaner production and technical processes;
Clean energies;
Energy-saving technology;
Microreaction and microseparation technology;
Life cycle assessment.

We look forward to receiving your contribution.

Prof. Dr. Patricia Luis
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 submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Clean Technologies is an international peer-reviewed open access quarterly 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

sustainable technology
membrane technology
micro-technology
clean energy
green chemistry
life cycle assessment

Published Papers (12 papers)

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Research

Jump to: Review

15 pages, 1558 KiB

Open AccessCommunication

Sensing and Delineating Mixed-VOC Composition in the Air Using a Single Metal Oxide Sensor

by Govind S. Thakor, Ning Zhang and Rafael M. Santos

Clean Technol. 2021, 3(3), 519-533; https://doi.org/10.3390/cleantechnol3030031 - 13 Jul 2021

Cited by 3 | Viewed by 3227

Abstract

Monitoring volatile organic compounds (VOCs) places a crucial role in environmental pollutants control and indoor air quality. In this study, a metal-oxide (MOx) sensor detector (used in a commercially available monitor) was employed to delineate the composition of air containing three common VOCs (ethanol, acetone, and hexane) under various concentrations. Experiments with a single component and double components were conducted to investigate how the solvents interact with the metal oxide sensor. The experimental results revealed that the affinity between VOC and sensor was in the following order: acetone > ethanol > n-hexane. A mathematical model was developed, based on the experimental findings and data analysis, to convert the output resistance value of the sensor into concentration values, which, in turn, can be used to calculate a VOC-based air quality index. Empirical equations were established based on inferences of vapour composition versus resistance trends, and on an approach of using original and diluted air samples to generate two sets of resistance data per sample. The calibration of numerous model parameters allowed matching simulated curves to measured data. Therefore, the predictive mathematical model enabled quantifying the total concentration of sensed VOCs, in addition to estimating the VOC composition. This first attempt to obtain semiquantitative data from a single MOx sensor, despite the remaining selectivity challenges, is aimed at expanding the capability of mobile air pollutants monitoring devices. Full article

(This article belongs to the Special Issue Feature Papers 2020)

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26 pages, 15759 KiB

Open AccessArticle

Hybrid PV System with High Speed Flywheel Energy Storage for Remote Residential Loads

by Abid Soomro, Keith R. Pullen and Mustafa E. Amiryar

Clean Technol. 2021, 3(2), 351-376; https://doi.org/10.3390/cleantechnol3020020 - 20 Apr 2021

Cited by 5 | Viewed by 7105

Abstract

Due to low system inertia in microgrids, frequencies may vary rapidly from the nominal value, leading to the complete blackout of the system unless there is an adequate spinning reserve available for balancing the supply with the demand load. This issue of instability in microgrids under islanded operation has attracted particular attention recently. A diesel generator is considered to be an ideal spinning reserve to provide back-up power to the load along with the renewable energy source in islanded system. However, the high maintenance cost and CO₂ emissions of diesel generator are detrimental factors which have inspired searches for more cost effective and cleaner technologies. The integration of an energy storage system (ESS) in islanded system along with generator not only reduces generator maintenance costs but also reduces the CO₂ emissions by limiting its operating hours. This paper proposes an islanded PV hybrid microgrid system (PVHMS) utilizing flywheel energy storage systems (FESS) as an alternative to battery technology to support the PV system and meet the peak demand of a small residential town with 100 dwellings. The diesel generator is used in the islanded system as a spinning reserve to maintain the stability of the islanded system when the PV system and flywheel storage cannot meet the load demand. Results of analysis of such a system demonstrate that flywheel energy storage technology of appropriate size offers a viable solution to support the operation of the standalone PV system. Furthermore, the reduction in CO₂ emissions and fuel consumption has been quantified as compared with the case with flywheel energy storage systems which means the diesel generator but always be operating. Full article

(This article belongs to the Special Issue Feature Papers 2020)

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24 pages, 6409 KiB

Open AccessArticle

Comparative Study of a Clean Technology Based on DSF Use in Occupied Buildings for Improving Comfort in Winter

by Eusébio Conceição, João Gomes, Maria Manuela Lúcio, Maria Inês Conceição and Hazim Awbi

Clean Technol. 2021, 3(2), 311-334; https://doi.org/10.3390/cleantechnol3020018 - 01 Apr 2021

Viewed by 2745

Abstract

This paper presents a comparative study of a clean technology based on a DSF (double skin facade) used in winter conditions in the occupied buildings comfort improvement, namely the thermal comfort and air quality. The performance of a solar DSF system, the building’s thermal response, the internal thermal comfort and the internal air quality are evaluated. In this study, a DSF system, an air transport system and a HVAC (heating, ventilating and air conditioning) system based on mixing ventilation are used. The study considers a virtual chamber occupied by eight persons and equipped, in the outside environment, by three DSFs. A new horary pre-programming control methodology is developed and applied when the airflow rate is constant and the number of DSFs to operate is variable, when the airflow rate is variable and the number of DSFs to operate is constant and when the airflow rate is variable and the number of DSFs to operate is variable. This work uses a numerical model that simulates the integral building thermal behavior and an integral human thermal response. The internal air, provided by a mixing ventilating system, is warmed using the DSF system. The air temperature inside the DSF system and the virtual chamber, the thermal comfort level using the PMV index, the internal air quality using the carbon dioxide concentration and the uncomfortable hours are calculated for winter conditions. The results obtained show that the energy produced in the DSF, using solar radiation, guarantees acceptable thermal comfort conditions in the morning and in the afternoon. The indoor air quality obtained at the breathing level is acceptable. It is found that the airflow rate to be used is more decisive than the DSF operating methodology. However, when a solution is chosen that combines a ventilation rate with the number of DSF to operate, both variables throughout the day can obtain simultaneously better results for indoor air quality and thermal comfort according to the standards. Full article

(This article belongs to the Special Issue Feature Papers 2020)

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21 pages, 6411 KiB

Open AccessArticle

Critical Analysis and Evaluation of the Technology Pathways for Carbon Capture and Utilization

by Simon P. Philbin

Clean Technol. 2020, 2(4), 492-512; https://doi.org/10.3390/cleantechnol2040031 - 11 Dec 2020

Cited by 8 | Viewed by 4548

Abstract

Carbon capture and utilization (CCU) is the process of capturing unwanted carbon dioxide (CO₂) and utilizing for further use. CCU offers significant potential as part of a sustainable circular economy solution to help mitigate the impact of climate change resulting from the burning of hydrocarbons and alongside adoption of other renewable energy technologies. However, implementation of CCU technologies faces a number of challenges, including identifying optimal pathways, technology maturity, economic viability, environmental considerations as well as regulatory and public perception issues. Consequently, this research study provides a critical analysis and evaluation of the technology pathways for CCU in order to explore the potential from a circular economy perspective of this emerging area of clean technology. This includes a bibliographic study on CCU, evaluation of carbon utilization processes, trend estimation of CO₂ usage as well as evaluation of methane and methanol production. A value chain analysis is provided to support the development of CCU technologies. The research study aims to inform policy-makers engaged in developing strategies to mitigate climate change through reduced carbon dioxide emission levels and improve our understanding of the circular economy considerations of CCU in regard to production of alternative products. The study will also be of use to researchers concerned with pursuing empirical investigations of this important area of sustainability. Full article

(This article belongs to the Special Issue Feature Papers 2020)

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16 pages, 5567 KiB

Open AccessArticle

Agro Waste Sugarcane Bagasse as a Cementitious Material for Reactive Powder Concrete

by Selvadurai Sebastin, Arun Kumar Priya, Alagar Karthick, Ravishankar Sathyamurthy and Aritra Ghosh

Clean Technol. 2020, 2(4), 476-491; https://doi.org/10.3390/cleantechnol2040030 - 07 Dec 2020

Cited by 31 | Viewed by 4540

Abstract

In the field of advanced concrete science, the construction industry has risen to great heights. Due to its own characterisation, the manufacturing cost of reactive powder concrete (RPC) is very high. This can be minimised by substituting the components of the RPC with the aid of agro waste. Because of the production of sugar from the sugar cane industry, bagasse ash is abundantly available in India. It is not ideal for the direct replacement of ingredients in concrete because of the presence of carbon dioxide in bagasse ash. The study of bagasse ash’s actions under different temperatures and different exposure times is discussed in this paper. It is inferred from the findings obtained from the energy dispersive study of X-ray (EDAX) that the presence of reactive silica in bagasse ash could be substituted by RPC ingredients due to heat treatment. RPC is composed of exceptionally fine powders (cement, sand, quartz powder and silica smolder) and superplasticiser. The superplasticiser, utilised at its ideal dose, decreases the water to cement proportion (w/c) while enhancing the workability of the concrete. A thick matrix is accomplished by optimising the granular packing of the dry fine powders. This compactness gives RPC ultra-high quality and durability. Reactive powder concretes have compressive qualities extending from 200 to 800 MPa. Full article

(This article belongs to the Special Issue Feature Papers 2020)

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14 pages, 423 KiB

Open AccessArticle

Evaluating the Emissions of the Heat Supplied by District Heating Networks through A Life Cycle Perspective

by Francesco Neirotti, Michel Noussan and Marco Simonetti

Clean Technol. 2020, 2(4), 392-405; https://doi.org/10.3390/cleantechnol2040024 - 06 Oct 2020

Cited by 3 | Viewed by 4331

Abstract

The Life Cycle Assessment methodology has proven to be effective in evaluating the impacts of goods production throughout their life cycle. While many studies are available on specific products, in recent years a growing interest is related to the analysis of services, including energy supply for final customers. Different LCA evaluations are available for electricity, while the heating and cooling sector has not yet been properly investigated. The objective of this study is the analysis of the specific impacts of the heat supplied to the final users connected to a district heating system, in comparison with traditional individual natural gas boilers, which represent the baseline heating solution in several urban contexts in Europe. The results show that the comparison is heavily dependent on the allocation method used for combined heat and power plant production. District Heating impact on heat supplied to the users can vary from 0.10 to 0.47 kg

_{{CO}_{2} eq}

/kWh, while distributed natural gas boilers present an overall impact equal to 0.27 kg

_{{CO}_{2} eq}

/kWh. Full article

(This article belongs to the Special Issue Feature Papers 2020)

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12 pages, 1230 KiB

Open AccessArticle

Benchmarking Wind Farm Projects by Means of Series Two-Stage DEA

by Ioannis E. Tsolas

Clean Technol. 2020, 2(3), 365-376; https://doi.org/10.3390/cleantechnol2030022 - 04 Sep 2020

Cited by 3 | Viewed by 2478

Abstract

This paper presents a data envelopment analysis (DEA) approach to benchmark a group of wind farm (WF) projects in Greece by employing a series two-stage structure. In the first stage, the investment performance of projects is evaluated using contract data and site wind conditions, though in the second stage the WF operational efficiency is evaluated using data on production inputs and output. Inefficiency occurs in both the construction and operating stages, but the construction process appears to be more inefficient relative to the operating phase. Moreover, WF size is related to operating efficiency and sensitivity analysis results identify wind speed and WF installation capacity as the factors that affect the investment performance and operational efficiency, respectively. The proposed approach is an addition to the existing literature and it can be used by managers and facility operators. Full article

(This article belongs to the Special Issue Feature Papers 2020)

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12 pages, 3800 KiB

Open AccessArticle

Optimization of a Hybrid Solar PV and Gas Turbine Generator System Using the Loss of Load Probability Index

by Mohamed Atef, Tamer Khatib, Muhammad Faris Abdullah and Mohd Fakhizan Romlie

Clean Technol. 2020, 2(3), 240-251; https://doi.org/10.3390/cleantechnol2030016 - 14 Jul 2020

Cited by 3 | Viewed by 2926

Abstract

In this paper, an optimization approach for designing a hybrid renewable energy system with zero load rejection is presented for a specific location in Malaysia. The proposed renewble energy system includes photovoltaic system, gas turbine generator and battery bank. The aim of the optimization process is to design the system with a loss of load probability that is less than 1%. An improved numerical algorithm is proposed in this paper. Moreover, a comparison between electrification options, including the existing gas-turbine-based generator (existing system), electricity grid and the proposed system, is presented in terms of the annualized total life-cycle cost. The results show that the proposed system can reduce the annual running cost by USD 2.1 million, while the electricity grid connection option can reduce the annual cost by USD 1.16 million as compared to the existing gas-turbine-based generator. In addition to this, the proposed optimization algorithm provides a reliable power system with zero load rejection based on simulation results. Full article

(This article belongs to the Special Issue Feature Papers 2020)

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Review

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17 pages, 1287 KiB

Open AccessReview

Social and Technological Impact of Businesses Surrounding Electric Vehicles

by Rachana Vidhi, Prasanna Shrivastava and Abhishek Parikh

Clean Technol. 2021, 3(1), 81-97; https://doi.org/10.3390/cleantechnol3010006 - 01 Feb 2021

Cited by 6 | Viewed by 5941

Abstract

Electric vehicle (EV) penetration has been increasing globally and is expected to continue its exponential growth over the coming decades. Several countries have already announced plans to achieve total or partial electrification of their vehicle fleets. Such rapid transportation electrification will have a significant impact on society and businesses that support the transportation industry. Additionally, new business opportunities will be available to support this technological evolution. In this paper, the business opportunities emerging from EVs and their supporting infrastructure are reviewed. It has been observed that several businesses, such as sustainable mining and manufacturing, will need to be developed before EV growth as they provide the initial platform required for EV adoption. Other businesses such as fleet optimization, battery management, and recycling can be developed at a later stage. All of these businesses will also have social and technological impacts, which will drive policy decisions. Regional governments play a critical role in ensuring the smooth execution of a transition to transportation electrification through social programs, such as training and education for equitable growth, and legislative decisions, such as technology standardization. Full article

(This article belongs to the Special Issue Feature Papers 2020)

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18 pages, 1807 KiB

Open AccessReview

Economic and Sustainability of Biodiesel Production—A Systematic Literature Review

by Tamás Mizik and Gábor Gyarmati

Clean Technol. 2021, 3(1), 19-36; https://doi.org/10.3390/cleantechnol3010002 - 08 Jan 2021

Cited by 101 | Viewed by 10151

Abstract

As Earth’s fossil energy resources are limited, there is a growing need for renewable resources such as biodiesel. That is the reason why the social, economic and environmental impacts of biofuels became an important research topic in the last decade. Depleted stocks of crude oil and the significant level of environmental pollution encourage researchers and professionals to seek and find solutions. The study aims to analyze the economic and sustainability issues of biodiesel production by a systematic literature review. During this process, 53 relevant studies were analyzed out of 13,069 identified articles. Every study agrees that there are several concerns about the first-generation technology; however, further generations cannot be price-competitive at this moment due to the immature technology and high production costs. However, there are promising alternatives, such as wastewater-based microalgae with up to 70% oil content, fat, oils and grease (FOG), when production cost is below 799 USD/gallon, and municipal solid waste-volatile fatty acids technology, where the raw material is free. Proper management of the co-products (mainly glycerol) is essential, especially at the currently low petroleum prices (0.29 USD/L), which can only be handled by the biorefineries. Sustainability is sometimes translated as cost efficiency, but the complex interpretation is becoming more common. Common elements of sustainability are environmental and social, as well as economic, issues. Full article

(This article belongs to the Special Issue Feature Papers 2020)

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14 pages, 13170 KiB

Open AccessReview

Chromogenic Technologies for Energy Saving

by Alessandro Cannavale

Clean Technol. 2020, 2(4), 462-475; https://doi.org/10.3390/cleantechnol2040029 - 20 Nov 2020

Cited by 15 | Viewed by 6827

Abstract

Chromogenic materials and devices include a wide range of technologies that are capable of changing their spectral properties according to specific external stimuli. Several studies have shown that chromogenics can be conveniently used in building façades in order to reduce energy consumption, with other significant effects. First of all, chromogenics influence the annual energy balance of a building, achieving significant reductions in consumption for HVAC and artificial lighting. In addition, these technologies potentially improve the indoor level of visual comfort, reducing the risks of glare and excessive lighting. This brief review points to a systematic discussion—although not exhaustive and mainly limited to recent results and investigations—of the main studies that deal with building-integrated chromogenics that have appeared, so far, in the scientific literature. Full article

(This article belongs to the Special Issue Feature Papers 2020)

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21 pages, 288 KiB

Open AccessReview

A Review of Technical Standards for Smart Cities

by Chun Sing Lai, Youwei Jia, Zhekang Dong, Dongxiao Wang, Yingshan Tao, Qi Hong Lai, Richard T. K. Wong, Ahmed F. Zobaa, Ruiheng Wu and Loi Lei Lai

Clean Technol. 2020, 2(3), 290-310; https://doi.org/10.3390/cleantechnol2030019 - 17 Aug 2020

Cited by 159 | Viewed by 23375

Abstract

Smart cities employ technology and data to increase efficiencies, economic development, sustainability, and life quality for citizens in urban areas. Inevitably, clean technologies promote smart cities development including for energy, transportation and health. The smart city concept is ambitious and is being refined with standards. Standards are used to help with regulating how smart cities function and contributing to define a smart city. Smart cities must be officially recognized by national and international authorities and organizations in order to promote societal advancement. There are many research and review articles on smart cities. However, technical standards are seldom discussed in the current literature. This review firstly presents the study of smart city definitions and domain. The well-known smart city standards will be presented to better recognize the smart city concept. Well-defined standards allow meaningful comparisons among smart cities implementation. How smart city initiatives make a city smarter and improve the quality of life will be discussed for various countries. This review highlights that technical standards are important for smart cities implementation. This paper serves as a guide to the most recent developments of smart cities standards. Full article

(This article belongs to the Special Issue Feature Papers 2020)

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