Journal Description
Clean Technologies
Clean Technologies
is a peer-reviewed, open access journal that investigates environmentally-friendly technologies and improves traditional polluted processes, and is published quarterly online by MDPI.
- Open Access— free for readers, with article processing charges (APC) paid by authors or their institutions.
- High Visibility: indexed within ESCI (Web of Science), and many other databases.
- Rapid Publication: manuscripts are peer-reviewed and a first decision provided to authors approximately 18 days after submission; acceptance to publication is undertaken in 14.7 days (median values for papers published in this journal in the first half of 2021).
- Recognition of Reviewers: APC discount vouchers, optional signed peer review, and reviewer names published annually in the journal.
Latest Articles
Investigating Combustion Process of N-Butanol-Diesel Blends in a Diesel Engine with Variable Compression Ratio
Clean Technol. 2021, 3(3), 618-628; https://doi.org/10.3390/cleantechnol3030037 - 20 Aug 2021
Abstract
The search for alternative fuels for internal combustion engines is ongoing. Among the alternatives, plant-based fuels can also be mentioned. Alcohol is not a common fuel for diesel engines because the physical and chemical properties of the alcohols are closer to those of
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The search for alternative fuels for internal combustion engines is ongoing. Among the alternatives, plant-based fuels can also be mentioned. Alcohol is not a common fuel for diesel engines because the physical and chemical properties of the alcohols are closer to those of gasoline. In our research, the combustion properties of diesel-n-butanol mixtures have been investigated to obtain results on the effect of butanol blending on combustion. Among the combustion properties, ignition delay, in-cylinder pressure, and heat release rate can be mentioned. They have been observed under different compression conditions on an engine on which the compression ratio can be adjusted. The method used was a quite simple one, so the speed of the engine was set to a constant 900 rpm without load, while three compression ratios (19.92, 15.27, and 12.53) were adjusted with a fuel flow rate of 13 mL/min and the pre-injection angle of 18° BTDC. Blending butanol into the investigated fuel does not significantly affect maximal values of indicated pressure, while much more effect on the pressure rising rate can be detected. Furthermore, heat release rate and ignition delay increased at every compression ratio investigated. Despite the low blending rates of butanol in the mixtures, butanol significantly affects the combustion parameters, especially at high compression ratios.
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(This article belongs to the Special Issue Fuel Processing and Internal Combustion Engines)
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Techno-Economic Assessment of IGCC Power Plants Using Gas Switching Technology to Minimize the Energy Penalty of CO2 Capture
by
, , , , , , and
Clean Technol. 2021, 3(3), 594-617; https://doi.org/10.3390/cleantechnol3030036 - 10 Aug 2021
Abstract
Cost-effective CO2 capture and storage (CCS) is critical for the rapid global decarbonization effort recommended by climate science. The increase in levelized cost of electricity (LCOE) of plants with CCS is primarily associated to the large energy penalty involved in CO2
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Cost-effective CO2 capture and storage (CCS) is critical for the rapid global decarbonization effort recommended by climate science. The increase in levelized cost of electricity (LCOE) of plants with CCS is primarily associated to the large energy penalty involved in CO2 capture. This study therefore evaluates three high-efficiency CCS concepts based on integrated gasification combined cycles (IGCC): (1) gas switching combustion (GSC), (2) GSC with added natural gas firing (GSC-AF) to increase the turbine inlet temperature, and (3) oxygen production pre-combustion (OPPC) that replaces the air separation unit (ASU) with more efficient gas switching oxygen production (GSOP) reactors. Relative to a supercritical pulverized coal benchmark, these options returned CO2 avoidance costs of 37.8, 22.4 and 37.5 €/ton (including CO2 transport and storage), respectively. Thus, despite the higher fuel cost and emissions associated with added natural gas firing, the GSC-AF configuration emerged as the most promising solution. This advantage is maintained even at CO2 prices of 100 €/ton, after which hydrogen firing can be used to avoid further CO2 cost escalations. The GSC-AF case also shows lower sensitivity to uncertain economic parameters such as discount rate and capacity factor, outperforms other clean energy benchmarks, offers flexibility benefits for balancing wind and solar power, and can achieve significant further performance gains from the use of more advanced gas turbine technology. Based on all these insights, the GSC-AF configuration is identified as a promising solution for further development.
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(This article belongs to the Special Issue CO2 Capture and Sequestration 2020)
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Innovative Energy-Recovery Unit for the LED-Lighting System of Heavy-Duty Vehicles
by
, , , , and
Clean Technol. 2021, 3(3), 581-593; https://doi.org/10.3390/cleantechnol3030035 - 04 Aug 2021
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In this work, the development of an energy recovery control unit to be incorporated in the light-emitting diodes (LEDs) lighting systems of heavy-duty vehicles is presented. This innovative industrial product adopts modern power electronics technology to improve existing trucks’ LED lighting system by
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In this work, the development of an energy recovery control unit to be incorporated in the light-emitting diodes (LEDs) lighting systems of heavy-duty vehicles is presented. This innovative industrial product adopts modern power electronics technology to improve existing trucks’ LED lighting system by eliminating the so far inevitable power consumption by the conventional central control unit of the majority of these vehicles, which is obligatory for the uninterruptable operation of their lighting system. The main idea of this innovative product is its capability to virtually increase the lighting system power consumption without actually consuming this amount of energy, thus facilitating the central control unit requirements regarding these vehicles in an energy-conscious way. Under this light, a mature power converter’s topology is employed to draw the proper amounts of power from the vehicle’s batteries supply, to the level that the central control unit recognizes, and return this energy back to the batteries. The tests results of the developed industrial product highlight the energy saving potential of the proposed energy recovery scheme, while the Life Cycle Cost Analysis (LCCA) results confirm its techno-economical and environmental profit for the truck applications under study.
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Open AccessCommunication
Carbon Storage in Portland Cement Mortar: Influences of Hydration Stage, Carbonation Time and Aggregate Characteristics
Clean Technol. 2021, 3(3), 563-580; https://doi.org/10.3390/cleantechnol3030034 - 30 Jul 2021
Abstract
This study elucidates the effects of the particle size, carbonation time, curing time and pressure on the efficiency of carbon storage in Portland cement mortar. Using pressure chamber experiments, our findings show how carbonation efficiency increases with a decrease in the particle size.
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This study elucidates the effects of the particle size, carbonation time, curing time and pressure on the efficiency of carbon storage in Portland cement mortar. Using pressure chamber experiments, our findings show how carbonation efficiency increases with a decrease in the particle size. Approximately 6.4% and 8.2% (w/w) carbonations were achieved in the coarse-sand and fine-sand based mortar samples, respectively. For the hydration/curing time of 7 h, up to 12% carbonation was achieved. This reduced to 8.2% at 40 h curing period. On the pressure effect, for comparable curing conditions, 2 bar at 7 h carbonation time gives 1.4% yield, and 8.2% at 5 bar. Furthermore, analysing the effect of the carbonation time, under comparable conditions, shows that 4 h of carbonation time gives up to 8.2% yield while 64 h of carbonation gives up to 18.5%. It can be reliably inferred that, under similar conditions, carbonation efficiency increases with lower-sized particles or higher-surface areas, increases with carbonation time and higher pressure but decreases with hydration/curing time. Microstructural analyses with X-ray diffraction (XRD) and scanning electron microscopy (SEM) further show the visual disappearance of calcium-silicate-hydrate (C-S-H) together with the inhibition of ettringite formation by the presence of CO2 and CaCO3 formation during carbonation.
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(This article belongs to the Special Issue CO2 Capture and Sequestration 2020)
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Investigation of Performance and Emission Parameters of Hydroxygen (HHO)-Enriched Diesel Fuel with Water Injection in the Compression Ignition Engine
Clean Technol. 2021, 3(3), 537-562; https://doi.org/10.3390/cleantechnol3030033 - 26 Jul 2021
Abstract
The development of engine technologies and research on combustion processes are focused on finding new generation CI engines with simple control of the combustion process while efficiently maintaining desirable engine performance and meeting emission regulations. This comprehensive study on the relatively low hydrogen
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The development of engine technologies and research on combustion processes are focused on finding new generation CI engines with simple control of the combustion process while efficiently maintaining desirable engine performance and meeting emission regulations. This comprehensive study on the relatively low hydrogen energy fraction (0.65–1.80%), supplied by onboard water electrolysers and on water injection, was performed on the performance and emission parameters of the CI engine. The article presents results of both experiment and simulation about the effect of hydroxygen and water injection on the combustion process, auto-ignition delay, combustion intensity, the temperature of the mixture and engine performance at BMEP of 0.2 MPa, 0.4 MPa, 0.6 MPa, and 0.8 MPa at a speed of 1900 rpm. For the first part, the test engine operated with diesel fuel with 3.5 L/min of hydroxygen gas supplied with an external mixture formation. The HHO has an effect on the combustion process at all range of BMEP. A decrease in BTE and increase in BSFC were noticed during tests. The peak pressure and the rate of heat release decreased, but the NOx decreased as well. The second part of experiment was performed with the injection of a substantial amount of water, 8.4–17.4 kg/h (140–290 cm3/min), and the same amount of hydroxygen. The injection of water further decreased the NOx; therefore, HHO and WI can be used to meet emission regulations. A simulation of the combustion process was carried out with the AVL BOOST sub-program BURN. The AVL BOOST simulation provided a detailed view of the in-cylinder pressure, pressure-rise, combustion intensity shape parameter and SOC.
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(This article belongs to the Special Issue Fuel Processing and Internal Combustion Engines)
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Open AccessEditorial
Clean Technol. 2021 Young Investigator Award: Announcement and Interview with the Winner
Clean Technol. 2021, 3(3), 534-536; https://doi.org/10.3390/cleantechnol3030032 - 19 Jul 2021
Abstract
After an extensive voting period, we are pleased to present the winner of the Clean Technol [...]
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Open AccessCommunication
Sensing and Delineating Mixed-VOC Composition in the Air Using a Single Metal Oxide Sensor
Clean Technol. 2021, 3(3), 519-533; https://doi.org/10.3390/cleantechnol3030031 - 13 Jul 2021
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
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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.
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(This article belongs to the Special Issue Feature Papers 2020)
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Open AccessArticle
Optimal Operation of Solar Powered Electric Vehicle Parking Lots Considering Different Photovoltaic Technologies
by
, , , and
Clean Technol. 2021, 3(2), 503-518; https://doi.org/10.3390/cleantechnol3020030 - 16 Jun 2021
Abstract
The performance of electric vehicles and their abilities to reduce fossil fuel consumption and air pollution on one hand and the use of photovoltaic (PV) panels in energy production, on the other hand, has encouraged parking lot operators (PLO) to participate in the
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The performance of electric vehicles and their abilities to reduce fossil fuel consumption and air pollution on one hand and the use of photovoltaic (PV) panels in energy production, on the other hand, has encouraged parking lot operators (PLO) to participate in the energy market to gain more profit. However, there are several challenges such as different technologies of photovoltaic panels that make the problem complex in terms of installation cost, efficiency, available output power and dependency on environmental temperature. Therefore, the aim of this study is to maximize the PLO’s operational profit under the time of use energy pricing scheme by investigating the effects of different PV panel technologies on energy production and finding the best strategy for optimal operation of PVs and electric vehicle (EV) parking lots which is achieved by means of market and EV owners’ interaction. For the accurate investigation, four different PV panel technologies are considered in different seasons, with significant differences in daylight times, in Helsinki, Finland.
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(This article belongs to the Special Issue Integration and Control of Distributed Renewable Energy Resources)
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Carbon Capture from Biogas by Deep Eutectic Solvents: A COSMO Study to Evaluate the Effect of Impurities on Solubility and Selectivity
by
and
Clean Technol. 2021, 3(2), 490-502; https://doi.org/10.3390/cleantechnol3020029 - 01 Jun 2021
Abstract
Deep eutectic solvents (DES) are compounds of a hydrogen bond donor (HBD) and a hydrogen bond acceptor (HBA) that contain a depressed melting point compared to their individual constituents. DES have been studied for their use as carbon capture media and biogas upgrading.
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Deep eutectic solvents (DES) are compounds of a hydrogen bond donor (HBD) and a hydrogen bond acceptor (HBA) that contain a depressed melting point compared to their individual constituents. DES have been studied for their use as carbon capture media and biogas upgrading. However, contaminants’ presence in biogas might affect the carbon capture by DES. In this study, conductor-like screening model for real solvents (COSMO-RS) was used to determine the effect of temperature, pressure, and selective contaminants on five DES’ namely, choline chloride-urea, choline chloride-ethylene glycol, tetra butyl ammonium chloride-ethylene glycol, tetra butyl ammonium bromide-decanoic acid, and tetra octyl ammonium chloride-decanoic acid. Impurities studied in this paper are hydrogen sulfide, ammonia, water, nitrogen, octamethyltrisiloxane, and decamethylcyclopentasiloxane. At infinite dilution, CO2 solubility dependence upon temperature in each DES was examined by means of Henry’s Law constants. Next, the systems were modeled from infinite dilution to equilibrium using the modified Raoults’ Law, where CO2 solubility dependence upon pressure was examined. Finally, solubility of CO2 and CH4 in the various DES were explored with the presence of varying mole percent of selective contaminants. Among the parameters studied, it was found that the HBD of the solvent is the most determinant factor for the effectiveness of CO2 solubility. Other factors affecting the solubility are alkyl chain length of the HBA, the associated halogen, and the resulting polarity of the DES. It was also found that choline chloride-urea is the most selective to CO2, but has the lowest CO2 solubility, and is the most polar among other solvents. On the other hand, tetraoctylammonium chloride-decanoic acid is the least selective, has the highest maximum CO2 solubility, is the least polar, and is the least affected by its environment.
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(This article belongs to the Special Issue CO2 Capture and Sequestration 2020)
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A Review of Heavy-Duty Vehicle Powertrain Technologies: Diesel Engine Vehicles, Battery Electric Vehicles, and Hydrogen Fuel Cell Electric Vehicles
Clean Technol. 2021, 3(2), 474-489; https://doi.org/10.3390/cleantechnol3020028 - 01 Jun 2021
Cited by 2
Abstract
Greenhouse gas emissions from the freight transportation sector are a significant contributor to climate change, pollution, and negative health impacts because of the common use of heavy-duty diesel vehicles (HDVs). Governments around the world are working to transition away from diesel HDVs and
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Greenhouse gas emissions from the freight transportation sector are a significant contributor to climate change, pollution, and negative health impacts because of the common use of heavy-duty diesel vehicles (HDVs). Governments around the world are working to transition away from diesel HDVs and to electric HDVs, to reduce emissions. Battery electric HDVs and hydrogen fuel cell HDVs are two available alternatives to diesel engines. Each diesel engine HDV, battery-electric HDV, and hydrogen fuel cell HDV powertrain has its own advantages and disadvantages. This work provides a comprehensive review to examine the working mechanism, performance metrics, and recent developments of the aforementioned HDV powertrain technologies. A detailed comparison between the three powertrain technologies, highlighting the advantages and disadvantages of each, is also presented, along with future perspectives of the HDV sector. Overall, diesel engine in HDVs will remain an important technology in the short-term future due to the existing infrastructure and lower costs, despite their high emissions, while battery-electric HDV technology and hydrogen fuel cell HDV technology will be slowly developed to eliminate their barriers, including costs, infrastructure, and performance limitations, to penetrate the HDV market.
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(This article belongs to the Special Issue The Road for Renewable Energies)
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A Binary Integer Programming Method for Optimal Wind Turbines Allocation
by
, , and
Clean Technol. 2021, 3(2), 462-473; https://doi.org/10.3390/cleantechnol3020027 - 01 Jun 2021
Abstract
The present study introduces a Binary Integer Programming (BIP) method to minimize the number of wind turbines needed to be installed in a wind farm. The locations of wind turbines are selected in a virtual grid which is constructed considering a minimum distance
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The present study introduces a Binary Integer Programming (BIP) method to minimize the number of wind turbines needed to be installed in a wind farm. The locations of wind turbines are selected in a virtual grid which is constructed considering a minimum distance between the wind turbines to avoid the wake effect. Additional equality constraints are also included to the proposed formulation to prohibit or enforce the installation of wind turbines placement at specific locations of the wind farmland. Moreover, a microscopic wind turbine placement considering the local air density is studied. To verify the efficiency of this proposal, a square site was subdivided into 25 square cells providing a virtual grid with 36 candidate placement locations. Moreover, a virtual grid with 121 vertices related with a Greek island is also tested. All simulations conducted considering the area of geographical territory, the length of wind turbine blades, as well as the capacity of each turbine.
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(This article belongs to the Special Issue The Road for Renewable Energies)
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Impact of Pyrolysis Oil Addition to Ethanol on Combustion in the Internal Combustion Spark Ignition Engine
Clean Technol. 2021, 3(2), 450-461; https://doi.org/10.3390/cleantechnol3020026 - 26 May 2021
Abstract
Thermal processing (torrefaction, pyrolysis, and gasification), as a technology can provide environmentally friendly use of plastic waste. However, it faces a problem with respect to its by-products. Pyrolysis oil obtained using this technology is seen as a substance that is extremely harmful for
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Thermal processing (torrefaction, pyrolysis, and gasification), as a technology can provide environmentally friendly use of plastic waste. However, it faces a problem with respect to its by-products. Pyrolysis oil obtained using this technology is seen as a substance that is extremely harmful for living creatures and that needs to be neutralized. Due to its relatively high calorific value, it can be considered as a potential fuel for internal combustion spark-ignition engines. In order make the combustion process effective, pyrolysis oil is blended with ethanol, which is commonly used as a fuel for flexible fuel cars. This article presents results from combustion tests conducted on a single-cylinder research engine at full load working at 600 rpm at a compression ratio of 9.5:1, and an equivalence ratio of 1. The analysis showed improvements in combustion and engine performance. It was found that, due to the higher calorific value of the blend, the engine possessed a higher indicated mean effective pressure. It was also found that optimal spark timing for this ethanol-pyrolysis oil blend was improved at a crank angle of 2–3° at 600 rpm. In summary, ethanol-pyrolysis oil blends at a volumetric ratio of 3:1 (25% pyrolysis oil) can successfully substitute ethanol in spark-ignition engines, particularly for vehicles with flexible fuel type.
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(This article belongs to the Special Issue Fuel Processing and Internal Combustion Engines)
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Analysis of Latvian Households’ Potential Participation in the Energy Market as Prosumers
Clean Technol. 2021, 3(2), 437-449; https://doi.org/10.3390/cleantechnol3020025 - 17 May 2021
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The European Union sets targets for the extensive use of renewable energy. Meanwhile, the energy production network is changing and transferring from the classic “producer to consumer” scheme to new operation models, where a small consumer with local renewable energy systems becomes a
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The European Union sets targets for the extensive use of renewable energy. Meanwhile, the energy production network is changing and transferring from the classic “producer to consumer” scheme to new operation models, where a small consumer with local renewable energy systems becomes a producer–prosumer, an active energy consumer who is also an energy producer. This study evaluated a potential of Latvian households’ participation in the energy market as prosumers. The analysis was based on an informal prospective extrapolation data evaluation method, based on real historical data from the Central Statistical Bureau of Latvia, annual reports of distribution and transmission system operators, assessments, and the conclusions of relevant experts. In addition, the real performance of a photovoltaic (PV) system was evaluated to get information on the whole year’s energy balance, and to compare it with seasonal electricity price fluctuation. The Latvian electricity transmission system is able to accept about 800 MW of additional new renewable energy source (RES) capacity, so there is a great potential for prosumers. The biggest obstacle for a household’s involvement in the energy market is the lack of support mechanisms and relatively high cost of RES technologies. The results show that with the current dynamics of new microgenerator connections, Latvia will achieve the set goals regarding the involvement of prosumers in the achievement of RES goals only in the next century. In order to attract the public to energy production, the concept of energy community needs to be defined in Latvian legislation, a balanced peer trading mechanism needs to be developed for various RES self-consumption groups willing to sell surplus electricity, and tax policy conditions need to be reviewed for electricity transactions outside the NET (payment system), in order to fully ensure the rights of prosumers.
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Open AccessArticle
Comparison of Mechanical and Physicochemical Characteristics of Potato Starch and Gelatine Blend Bioplastics Made with Gelatines from Different Sources
Clean Technol. 2021, 3(2), 424-436; https://doi.org/10.3390/cleantechnol3020024 - 11 May 2021
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Environmentally friendly packaging is becoming more popular as the number of companies implementing more sustainable solutions continues to increase, and consumers become more aware and choose more environmentally friendly options. However, not all environmentally friendly packaging meets all desirable properties, as some are
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Environmentally friendly packaging is becoming more popular as the number of companies implementing more sustainable solutions continues to increase, and consumers become more aware and choose more environmentally friendly options. However, not all environmentally friendly packaging meets all desirable properties, as some are only partially made of renewable raw materials or degrade over a long period of time. Bioplastics constructed from blends of gelatine and starch are solely made from renewable raw materials. Combined with relatively short degradation times, these materials have the potential to replace currently used, non-biodegradable film and single-use plastics. However, despite these advantages, further research is required to identify the best combination of raw materials, selectively and collectively, and to then optimise the appropriate physicochemical properties of the resultant bioplastics. In this study, gelatine from different sources (piscine, porcine, bovine) combined with potato starch was used to generate home-compostable bioplastics. These bioplastics were assessed in terms of water solubility, water content, opacity, surface roughness, and key mechanical properties such as tensile strength. Significant differences were found, particularly for piscine gelatine blends. It was concluded that piscine gelatine is a promising protein with highly relevant properties for the bioplastics industry.
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Open AccessArticle
Developing a Hybrid Optimization Algorithm for Optimal Allocation of Renewable DGs in Distribution Network
Clean Technol. 2021, 3(2), 409-423; https://doi.org/10.3390/cleantechnol3020023 - 01 May 2021
Abstract
Distributed generation (DG) is becoming a prominent key spot for research in recent years because it can be utilized in emergency/reserve plans for power systems and power quality improvement issues, besides its drastic impact on the environment as a greenhouse gas (GHG) reducer.
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Distributed generation (DG) is becoming a prominent key spot for research in recent years because it can be utilized in emergency/reserve plans for power systems and power quality improvement issues, besides its drastic impact on the environment as a greenhouse gas (GHG) reducer. For maximizing the benefits from such technology, it is crucial to identify the best size and location for DG that achieves the required goal of installing it. This paper presents an investigation of the optimized allocation of DG in different modes using a proposed hybrid technique, the tunicate swarm algorithm/sine-cosine algorithm (TSA/SCA). This investigation is performed on an IEEE-69 Radial Distribution System (RDS), where the impact of such allocation on the system is evaluated by NEPLAN software.
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(This article belongs to the Special Issue Integration and Control of Distributed Renewable Energy Resources)
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Open AccessArticle
Three-Phase State Estimation for Distribution-Grid Analytics
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Clean Technol. 2021, 3(2), 395-408; https://doi.org/10.3390/cleantechnol3020022 - 01 May 2021
Abstract
Power-distribution grids consist of assets such as transformers, cables, and switches, of which the proper utilization is essential for the provision of a secure and reliable power supply to end customers. Distribution-system operators (DSOs) are responsible for the operation and maintenance of these
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Power-distribution grids consist of assets such as transformers, cables, and switches, of which the proper utilization is essential for the provision of a secure and reliable power supply to end customers. Distribution-system operators (DSOs) are responsible for the operation and maintenance of these assets. Due to the increased use of renewable sources such as wind and solar, grid assets are prone to operation conditions outside safe boundaries, such as overloading, large voltage unbalance, and a rise in voltage. At present, distribution grids are poorly monitored by DSOs, and the above-mentioned problems may thereby go unnoticed until the failure of a critical asset occurs. The deployment of smart meters in distribution grids has enabled measurements of grid variables such as power, current, and voltage. However, their measurements are used only for billing purposes, and not for monitoring and improving the operating condition of distribution grids. In this paper, a state-estimation algorithm is proposed that utilizes smart-meter data for offline analysis, and estimates the loading of grid assets and power losses. Single- and three-phase state-estimation algorithms are compared through simulation studies on a real-life low-voltage distribution grid using measured smart-meter data. The three-phase state-estimation algorithm based on the nonlinear weighted least-squares method was found to be more accurate in estimating cable loading and line power losses. The proposed method is useful for DSOs to analyze power flows in their distribution grids and take necessary actions such as grid upgrades or the rerouting of power flows.
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(This article belongs to the Special Issue Smart Grid Technologies)
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Open AccessReview
Overview of the Enablers and Barriers for a Wider Deployment of CSP Tower Technology in Europe
Clean Technol. 2021, 3(2), 377-394; https://doi.org/10.3390/cleantechnol3020021 - 21 Apr 2021
Cited by 1
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For years, concentrated solar power (CSP) has been considered an emerging technology that could disrupt the energy production sector. The possibility to store the electricity generated during the sunny operating hours in the form of heat enhances energy dispatchability and gives CSP a
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For years, concentrated solar power (CSP) has been considered an emerging technology that could disrupt the energy production sector. The possibility to store the electricity generated during the sunny operating hours in the form of heat enhances energy dispatchability and gives CSP a unique value proposition that conventional renewable energies cannot provide cost-efficiently since it requires the integration of costly large-scale battery systems. CSP is a cleaner technology compared to photovoltaics, but photovoltaics currently has lower overall capital costs, making it more attractive to investors and stakeholders who want to spend less money upfront. This is one of the main reasons why CSP has never really led either the electricity market or the heating one, even if its combined generation capability (heat and electricity) is globally recognized as a great advantage for a renewable technology. In this study, we analyze the reasons why CSP is not as widespread as it could be; at the same time, we look at the opportunities and the enablers for a further deployment of this technology, focusing on the European region.
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Open AccessArticle
Hybrid PV System with High Speed Flywheel Energy Storage for Remote Residential Loads
Clean Technol. 2021, 3(2), 351-376; https://doi.org/10.3390/cleantechnol3020020 - 20 Apr 2021
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
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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.
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(This article belongs to the Special Issue Feature Papers 2020)
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Study of Influential Parameters of the Caffeine Extraction from Spent Coffee Grounds: From Brewing Coffee Method to the Waste Treatment Conditions
Clean Technol. 2021, 3(2), 335-350; https://doi.org/10.3390/cleantechnol3020019 - 02 Apr 2021
Cited by 1
Abstract
This article aims to study the interest of spent coffee grounds (SCG) valorization through caffeine recovery. In an original way, this study takes into account all the parameters such as (i) the brewing coffee methods (household, coffee shops, etc.); (ii) the storage conditions,
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This article aims to study the interest of spent coffee grounds (SCG) valorization through caffeine recovery. In an original way, this study takes into account all the parameters such as (i) the brewing coffee methods (household, coffee shops, etc.); (ii) the storage conditions, in particular the drying step; (iii) the solid/liquid extraction parameters such as the nature of solvent, the temperature, the extraction time and the solid/liquid ratio; and (iv) the liquid/liquid purification parameters such as the nature, the volume and the pH of extraction medium. Results have shown that spent coffee grounds from coffee-shops obtained by percolation contain a higher amount of caffeine than spent coffee grounds from households obtained from spent pods or filters. A drying treatment is not required when extraction is performed under one week after the spent coffee grounds collection with 96.4% of not degraded caffeine. Solid/liquid extraction performed with 25 mL.g−1 SCG of hydroalcoholic solvent (water/EtOH, v/v 60/40) at 60 °C during 15 min have given a caffeine yield up to 4.67 mg.g−1 SCG. When using ethyl acetate, 93.4% of the caffeine has been selectively recovered by liquid/liquid extraction. Finally, the extraction of caffeine for the valorization of spent coffee grounds is a promising and easy way, which fits with an already important and well established market.
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(This article belongs to the Special Issue Green Process Engineering)
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Open AccessArticle
Comparative Study of a Clean Technology Based on DSF Use in Occupied Buildings for Improving Comfort in Winter
Clean Technol. 2021, 3(2), 311-334; https://doi.org/10.3390/cleantechnol3020018 - 01 Apr 2021
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
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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.
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(This article belongs to the Special Issue Feature Papers 2020)
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