Advances in Clean Energies

Topic Information

Dear Colleagues,

Traditional fossil fuels, such as coal, oil, and natural gas, contribute most to the sustainable economic development for the industrial sectors in the past few decades. The negative environmental and economic impacts, however, should be considered since fossil fuels will trigger many problems, such as environmental pollution, global warming, and economic security. For example, CO₂ and other pollutant emissions, due to the burning of hydrocarbon fossil fuels, are one of main contributors to atmospheric pollution and climate change. In order to cope with the energy and environment crisis, clean energy technologies, which aim to reduce CO₂ and pollutant emissions, are becoming one of the hot spots in the industry and academia. More and more researchers are entering field and related papers are expanding quickly. Thus, we are committed to providing the platform for the high-quality papers in the field of clean energies. This topic focuses on fundamentals and applied researches which could help to reduce CO₂ and pollutant emissions. The topic includes but is not limited to:

• Hydrogen production, transport, storage, and usage;
• Fuel cell technologies;
• Advanced combustion theory;
• Methanol and other clean alternative fuels;
• Solar photovoltaic and thermal systems;
• Safety issues in the usage of clean energies;
• Energy management system.

Dr. Yongliang Xie
Dr. Shimao Wang
Topic Editors

Keywords

Participating Journals

Journal Name	Impact Factor	CiteScore	Launched Year	First Decision (median)	APC
Clean Technologies cleantechnol	4.1	6.1	2019	33.5 Days	CHF 1600
Energies energies	3.0	6.2	2008	16.8 Days	CHF 2600
Resources resources	3.6	7.2	2012	26.1 Days	CHF 1600

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21 pages, 3372 KiB  

Open AccessArticle

Active Power Cooperative Control for Wind Power Clusters with Multiple Temporal and Spatial Scales

by Minan Tang, Wenjuan Wang, Jiandong Qiu, Detao Li and Linyuan Lei

Energies 2022, 15(24), 9453; https://doi.org/10.3390/en15249453 - 13 Dec 2022

Cited by 2 | Viewed by 1590

Abstract

To improve the control of active power in wind power clusters, an active power hierarchical predictive control method with multiple temporal and spatial scales is proposed. First, the method from the spatial scale divides the wind power clusters into the cluster control layer, [...] Read more.

To improve the control of active power in wind power clusters, an active power hierarchical predictive control method with multiple temporal and spatial scales is proposed. First, the method from the spatial scale divides the wind power clusters into the cluster control layer, sub-cluster coordination layer and single wind farm power regulation layer. Simultaneously, from the temporal scale, the predicted data are divided layer by layer: the 15 min power prediction is deployed for the first layer; the 5 min power prediction is employed for the second layer; the 1 min power prediction is adopted for the third layer. Secondly, the prediction model was developed, and each hierarchical prediction was optimized using MPC. Thirdly, wind farms are dynamically clustered, and then the output power priority of wind farms is established. In addition, the active power of each wind farm is controlled according to the error between the dispatch value and the real-time power with feedback correction so that each wind farm achieves cooperative control with optimal power output. Finally, combined with the simulation of practical wind power clusters, the results show that the wind abandonment rate was reduced by 2.13%, and the dispatch of the blindness was overcome compared with the fixed proportional strategy. Therefore, this method can improve the efficiency of cooperative power generation. Full article

(This article belongs to the Topic Advances in Clean Energies)

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15 pages, 4014 KiB  

Open AccessArticle

Data-Driven Machine Learning Approach for Predicting the Higher Heating Value of Different Biomass Classes

by Inioluwa Christianah Afolabi, Emmanuel I. Epelle, Burcu Gunes, Fatih Güleç and Jude A. Okolie

Clean Technol. 2022, 4(4), 1227-1241; https://doi.org/10.3390/cleantechnol4040075 - 22 Nov 2022

Cited by 15 | Viewed by 3463

Abstract

Higher heating values (HHV) is a very useful parameter for assessing the design and large-scale operation of biomass-driven energy systems. HHV is conventionally measured experimentally with an adiabatic oxygen bomb calorimeter. This procedure is often time-consuming and expensive. Furthermore, limited access to the [...] Read more.

Higher heating values (HHV) is a very useful parameter for assessing the design and large-scale operation of biomass-driven energy systems. HHV is conventionally measured experimentally with an adiabatic oxygen bomb calorimeter. This procedure is often time-consuming and expensive. Furthermore, limited access to the required facilities is the main bottleneck for researchers. Empirical linear and nonlinear models have initially been proposed to address these concerns. However, most of the models showed discrepancies with experimental results. Data-driven machine learning (ML) methods have also been adopted for HHV predictions due to their suitability for nonlinear problems. However, most ML correlations are based on proximate or ultimate analysis. In addition, the models are only applicable to either the originator biomass or one specific type. To address these shortcomings, a total of 227 biomass datasets based on four classes of biomass, including agricultural residue, industrial waste, energy crop, and woody biomass, were employed to develop and verify three different ML models, namely artificial neural network (ANN), decision tree (DT) and random forest (RF). The model incorporates proximate and ultimate analysis data and biomass as input features. RF model is identified as the most reliable because of its lowest mean absolute error (MAE) of 1.01 and mean squared error (MSE) of 1.87. The study findings can be used to predict HHV accurately without performing experiments. Full article

(This article belongs to the Topic Advances in Clean Energies)

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19 pages, 4896 KiB  

Open AccessArticle

Performance Comparison of Mini-Rectangular Fin Heat Sinks Using Different Coolants: Supercritical CO₂, Water and Al₂O₃/H₂O Nanofluid

by Asem Alemam, Sherif A. Yehya, Abubaker S. Omer, Ameer Hamza, Muhammed Saeed and Abdallah S. Berrouk

Energies 2022, 15(22), 8734; https://doi.org/10.3390/en15228734 - 20 Nov 2022

Cited by 2 | Viewed by 2830

Abstract

Mini-channel heatsinks have proven useful in removing high heat fluxes from microelectronic devices. However, further miniaturization of electronic devices requires significant enhancement in the mini-channel heatsinks’ thermohydraulic characteristics, which depend greatly on the coolant and geometrical configuration of the channel. Therefore, the current [...] Read more.

Mini-channel heatsinks have proven useful in removing high heat fluxes from microelectronic devices. However, further miniaturization of electronic devices requires significant enhancement in the mini-channel heatsinks’ thermohydraulic characteristics, which depend greatly on the coolant and geometrical configuration of the channel. Therefore, the current study explores the potential of mini-channel heatsinks’ using different coolants (water, nanofluid and supercritical carbon dioxide) and various channel configurations. The effect of various channel configurations on the thermohydraulic characteristics of the mini-channel heat sinks is evaluated numerically for different coolants employing three flow rates (17 g/s, 34 g/s and 50 g/s). Hence, the effects of fin height, spacing and thickness, and mass flow rate on the overall heat transfer coefficient (CHT) and pressure drop (ΔP) are reported for the abovementioned coolants. It is found that increasing the mass flow rate increases both the CHT and ΔP. It is also noted that increasing the fin height and spacing decreases both the CHT and ΔP, as opposed to increasing the thickness, which causes both the CHT and ΔP to increase. Among the three coolants used, the sCO₂ shows superior performance compared to the water and nanofluid and this based on higher CHT and lower ΔP. Moreover, the performance evaluation criterion (PEC) for the sCO₂ is higher than that for the water and nanofluid by 53% at 17 g/s flow rate and 243% at 50 g/s flow rate. Full article

(This article belongs to the Topic Advances in Clean Energies)

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17 pages, 309 KiB  

Open AccessReview

Solar Energy Implementation for Health-Care Facilities in Developing and Underdeveloped Countries: Overview, Opportunities, and Challenges

by Esteban A. Soto, Andrea Hernandez-Guzman, Alexander Vizcarrondo-Ortega, Amaya McNealey and Lisa B. Bosman

Energies 2022, 15(22), 8602; https://doi.org/10.3390/en15228602 - 17 Nov 2022

Cited by 14 | Viewed by 7850

Abstract

Developing and underdeveloped countries face innumerable problems related to the accessibility and quality of energy that put the lives of patients, health-care infrastructures, and health workers at risk. Current approaches, such as grid power, unsustainable energy sources such as diesel or gas, and [...] Read more.

Developing and underdeveloped countries face innumerable problems related to the accessibility and quality of energy that put the lives of patients, health-care infrastructures, and health workers at risk. Current approaches, such as grid power, unsustainable energy sources such as diesel or gas, and mobile health clinics, have proven insufficient to address this issue. In response, access to reliable health care and electricity has undergone multiple transformations in the last decade, especially in remote and rural areas. Good health and clean energy are two of the 17 United Nations Sustainable Development Goals, originally designed to be a “shared blueprint for peace and prosperity for people and the planet, now and into the future.” Unfortunately, little is known about the interaction between health-care access and energy access in developing and underdeveloped countries, mainly in remote or rural areas. For this reason, this study conducts a review of the literature, including current approaches, challenges, and opportunities for the implementation of solar energy in health centers. As a result, several challenges and opportunities in three impact areas are presented: (1) operational, (2) environmental, and (3) economic. This study delivers detailed information that allows the implementation of solar energy in the health-care sector (in a more effective manner) by sharing best practices. Full article

(This article belongs to the Topic Advances in Clean Energies)

26 pages, 1253 KiB  

Open AccessFeature PaperReview

A Review of the Life Cycle Analysis Results for Different Energy Conversion Technologies

by Violeta Motuzienė, Kęstutis Čiuprinskas, Artur Rogoža and Vilūnė Lapinskienė

Energies 2022, 15(22), 8488; https://doi.org/10.3390/en15228488 - 14 Nov 2022

Cited by 11 | Viewed by 4083

Abstract

Technologies that use renewable energy sources (RES) are crucial to achieving decarbonization goals, but a significant number of studies show their relatively high environmental impact during the production phase. Therefore, technologies need to be compared in terms of their life-cycle environmental impact. The [...] Read more.

Technologies that use renewable energy sources (RES) are crucial to achieving decarbonization goals, but a significant number of studies show their relatively high environmental impact during the production phase. Therefore, technologies need to be compared in terms of their life-cycle environmental impact. The life cycle analysis (LCA) methodology is well known and widely employed. However, problems related to the methodological choices prevent taking full advantage of the LCA, as the results of numerous studies are often incomparable. The presented review aims to critically compare the impact of different energy generation technologies—RES (as well as non-RES) energy generators and co-generators. The numeric results are structured and analyzed in terms of the global warming potential (GWP) and non-RES primary energy consumption. The results show that RES technologies are superior compared to conventional fossil-fuel-based systems in most cases, and the high impact during the production and installation phases is compensated in the operational phase. The high variations in GWP from similar technologies result from different methodological choices, but they also show that the wrong choice of the technology in a certain location might cause serious environmental drawbacks when the impact of the RES technology exceeds the impact of fossil fuel-based technologies. Cogeneration technologies using waste as a fuel may even have a negative GWP impact, thus showing even higher potential for decarbonization than RES technologies. Full article

(This article belongs to the Topic Advances in Clean Energies)

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20 pages, 5636 KiB  

Open AccessArticle

Optimization and Techno-Economic Appraisal of Parabolic Trough Solar Power Plant under Different Scenarios: A Case Study of Morocco

by Hanane Ait Lahoussine Ouali, Ahmed Alami Merrouni, Shahariar Chowdhury, Kuaanan Techato, Sittiporn Channumsin and Nasim Ullah

Energies 2022, 15(22), 8485; https://doi.org/10.3390/en15228485 - 14 Nov 2022

Cited by 12 | Viewed by 3942

Abstract

Morocco is a country with a lack of fossil fuel resources and an increasing demand for energy. This inspired the country to increase the use of renewable energy in the energy mix. The objective of this study was to conduct an optimization and [...] Read more.

Morocco is a country with a lack of fossil fuel resources and an increasing demand for energy. This inspired the country to increase the use of renewable energy in the energy mix. The objective of this study was to conduct an optimization and techno-economic appraisal of a concentrated solar power plant (CSP) using different scenarios that took Ouarzazate city in the south of Morocco as a case study. To achieve this, several parameters were assessed, including the impacts of solar collector assemblies (SCAs), receiver types, heat transfer fluids, cooling systems, solar multiples, and thermal storage hours, with regard to the profitability of the CSP plant. Then, performance and sensitivity analyses were conducted to select the best integration scenarios based on different economic indicators, including levelized cost of electricity (LCOE) and net present value (NPV). The findings revealed that the use of the Luz LS-3 as the collector/SCA, Solel UVAC 3 as receiver, and Dowtherm Q as heat transfer fluid exhibited the highest performance in terms of the annual energy production yield and capacity factor, as well as the lowest real and nominal LCOEs with a wet cooled condenser. Furthermore, the LCOE is extremely sensitive to changes in the number of hours of storage and the solar multiple, and the optimal real and nominal LCOEs are determined by a highly specific combination of the solar multiple and the number of hours of storage. As a consequence, the maximum and minimum net electricity outputs for the best configuration of the Parabolic Trough Collector (PTC) plant were 24.6 GWh and 7.4 GWh in May and December, respectively. Likewise, the capacity factor and the gross-to-net conversion factor for the optimized plant were found to be 47.9%, and 93.5%, respectively. Concerning the economic study, the expected energy cost was 0.1303 USD per kWh and the NPV value for Ouarzazate city was positive (more than USD 20 million), which indicates that the studied PTC plant was estimated to be financially and economically feasible. The results of this analysis are highly significant and may persuade decision makers, financiers, and solar energy industry players to increase their investments in the Kingdom of Morocco. Full article

(This article belongs to the Topic Advances in Clean Energies)

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18 pages, 6056 KiB  

Open AccessArticle

Estimation of Nearshore Wind Conditions Using Onshore Observation Data with Computational Fluid Dynamic and Mesoscale Models

by Mizuki Konagaya, Teruo Ohsawa, Toshinari Mito, Takeshi Misaki, Taro Maruo and Yasuyuki Baba

Resources 2022, 11(11), 100; https://doi.org/10.3390/resources11110100 - 30 Oct 2022

Viewed by 2969

Abstract

This study aimed to establish numerical models to replicate wind conditions for nearshore waters, sensitive to onshore topography, and to compare the characteristics of computational fluid dynamic (CFD) and mesoscale models. Vertical Doppler light detection and ranging (LiDAR) observation data were measured at [...] Read more.

This study aimed to establish numerical models to replicate wind conditions for nearshore waters, sensitive to onshore topography, and to compare the characteristics of computational fluid dynamic (CFD) and mesoscale models. Vertical Doppler light detection and ranging (LiDAR) observation data were measured at an onshore site, which showed that wind conditions were affected by thermodynamic phenomena, such as land and sea breeze, and dynamical effects from neighboring onshore topography. The estimation accuracy of the CFD model depended on the height of the LiDAR data input. A height close to the target, such as the hub height of wind turbines, seemed appropriate as input data, considering that the accuracy of the wind speed shear replicated in a CFD numerical model may be uncertain. The mesoscale model replicated the wind through the thermodynamic effect and reliably estimated wind speed over nearshore waters without observation correction. Larger estimation errors were detected in the CFD model than in the mesoscale model, as the former could not account for thermodynamic effects. Wind conditions in water areas near complex coastlines may also be formed by thermodynamic factors, making analysis using a mesoscale model advantageous. Full article

(This article belongs to the Topic Advances in Clean Energies)

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16 pages, 7147 KiB  

Open AccessArticle

Experimental and Numerical Study on the Explosion Dynamics of the Non-Uniform Liquefied Petroleum Gas and Air Mixture in a Channel with Mixed Obstacles

by Bingang Guo, Jianfeng Gao, Bin Hao, Bingjian Ai, Bingyuan Hong and Xinsheng Jiang

Energies 2022, 15(21), 7999; https://doi.org/10.3390/en15217999 - 27 Oct 2022

Cited by 6 | Viewed by 2000

Abstract

Mixed obstacles have a great influence on the deflagration process of liquefied petroleum gas (LPG)-air premixed combustible gas with concentration gradient. The arrangement of mixed obstacles may further stimulate overpressure and flame propagation. In this work, based on experimental and numerical simulations, this [...] Read more.

Mixed obstacles have a great influence on the deflagration process of liquefied petroleum gas (LPG)-air premixed combustible gas with concentration gradient. The arrangement of mixed obstacles may further stimulate overpressure and flame propagation. In this work, based on experimental and numerical simulations, this paper analyzes the flame and overpressure, and mainly studies the coupling relationship among the explosion overpressure characteristics, the structure of flame and the speed of flame propagation. The result shows that when the rectangular obstacle is 100 mm away from the ignition source, not only the speed of flame is the fastest, but also the time required to reach the maximum over-pressure is the shortest. In this configuration, an elongated flame is formed between a rectangular obstacle and a flat obstacle, and an obvious backflow structure appears. In addition, the average growth rate of overpressure has a minimum value, reaching at −35 MPa/s. The existence of rectangular obstacles further stimulates the overpressure. When the rectangular obstacle is 400 mm away from the ignition source, the maximum overpressure value is the highest among the four configurations. Besides, the time when the maximum area of flame appears in the simulation is almost the same as the time when the maximum overpressure is obtained. In addition, the average growth rate of overpressure increases significantly after touching the rectangular obstacle, which coincides with the mutation time of the front tip of the flame, overpressure and area of flame after the flame encounters the rectangular obstacle. This research has an important theoretical guiding significance for preventing LPG leakage and explosion accidents in a long and narrow space. Full article

(This article belongs to the Topic Advances in Clean Energies)

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21 pages, 4480 KiB  

Open AccessReview

A Review of the Mitigating Methods against the Energy Conversion Decrease in Solar Panels

by Gabriella-Stefánia Szabó, Róbert Szabó and Loránd Szabó

Energies 2022, 15(18), 6558; https://doi.org/10.3390/en15186558 - 8 Sep 2022

Cited by 8 | Viewed by 3328

Abstract

Using solar panels is one of the cleanest ways to generate electricity ever created by mankind. The efficiency of rapidly expanding solar panels decreases during their lifetime for several reasons, such as photodegradation, hot spots, potentially induced degradation, etc. Dirt and debris accumulation [...] Read more.

Using solar panels is one of the cleanest ways to generate electricity ever created by mankind. The efficiency of rapidly expanding solar panels decreases during their lifetime for several reasons, such as photodegradation, hot spots, potentially induced degradation, etc. Dirt and debris accumulation on the surface of the solar panels can also significantly contribute to their performance degradation due to the diminishing of the solar radiation reaching their active surfaces. Numerous degradation mitigation methods are cited in the literature. This article briefly outlines these basic measures. Full article

(This article belongs to the Topic Advances in Clean Energies)

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25 pages, 1548 KiB  

Open AccessReview

A Critical Analysis of the Oxy-Combustion Process: From Mathematical Models to Combustion Product Analysis

by Brenda Raho, Gianpiero Colangelo, Marco Milanese and Arturo de Risi

Energies 2022, 15(18), 6514; https://doi.org/10.3390/en15186514 - 6 Sep 2022

Cited by 19 | Viewed by 5603

Abstract

Fossil fuels are the most widely used resource for energy production. Carbon dioxide (CO₂) emissions are correlated with climate change, and therefore these emissions must be reduced in the future. It is possible by means of many different technologies, and one [...] Read more.

Fossil fuels are the most widely used resource for energy production. Carbon dioxide (CO₂) emissions are correlated with climate change, and therefore these emissions must be reduced in the future. It is possible by means of many different technologies, and one of the most promising seems to be oxyfuel combustion. This process, with oxygen and recirculating gas, produces a concentrated stream of CO₂ and water. In recent years, many scientists carried out research and studies on the oxyfuel process, but a sufficient level of knowledge was not yet reached to exploit the great potential of this new technology. Although such areas of research are still highly active, this work provides an overview and summary of the research undertaken, the state of development of the technology, and a comparison of different plants so far. Full article

(This article belongs to the Topic Advances in Clean Energies)

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16 pages, 4450 KiB  

Open AccessArticle

Evaluation of Fuel Gas Supply System for Marine Dual-Fuel Propulsion Engines Using LNG and Ammonia Fuel

by Soobin Hyeon, Jinkwang Lee and Jungho Choi

Energies 2022, 15(17), 6303; https://doi.org/10.3390/en15176303 - 29 Aug 2022

Cited by 4 | Viewed by 3193

Abstract

This study proposes a fuel supply system for dual-fuel propulsion engines using liquefied natural gas (LNG) and ammonia to control carbon emissions. The independent fuel supply system of LNG and ammonia is configured as a hybrid system. The operating pressure of the re-condenser [...] Read more.

This study proposes a fuel supply system for dual-fuel propulsion engines using liquefied natural gas (LNG) and ammonia to control carbon emissions. The independent fuel supply system of LNG and ammonia is configured as a hybrid system. The operating pressure of the re-condenser is determined as a process variable according to the power consumption and flow rate of the non-condensable boil-off gas. The independent and hybrid systems are compared and evaluated through thermodynamic analyses, including specific power consumption (SPC) and exergy analyses, with respect to the fuel ratio and engine load. When the engine load is 100% in Case 1 for a 40% carbon reduction by 2030, the hybrid system exhibits an SPC reduction of 70% and exergy efficiency increase of 16% compared with the independent system. Full article

(This article belongs to the Topic Advances in Clean Energies)

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17 pages, 2287 KiB  

Open AccessArticle

Pyrolysis Valorization of Vegetable Wastes: Thermal, Kinetic, Thermodynamics, and Pyrogas Analyses

by Samar Elkhalifa, Sabah Mariyam, Hamish R. Mackey, Tareq Al-Ansari, Gordon McKay and Prakash Parthasarathy

Energies 2022, 15(17), 6277; https://doi.org/10.3390/en15176277 - 28 Aug 2022

Cited by 18 | Viewed by 2880

Abstract

In comparison to other methods, valorising food waste through pyrolysis appears to be the most promising because it is environmentally friendly, fast, and has a low infrastructure footprint. On the other hand, understanding the pyrolytic kinetic behaviour of feedstocks is critical to the [...] Read more.

In comparison to other methods, valorising food waste through pyrolysis appears to be the most promising because it is environmentally friendly, fast, and has a low infrastructure footprint. On the other hand, understanding the pyrolytic kinetic behaviour of feedstocks is critical to the design of pyrolysers. As a result, the pyrolytic degradation of some common kitchen vegetable waste, such as tomato, cucumber, carrot, and their blend, has been investigated in this study using a thermogravimetric analyser. The most prevalent model fitting method, Coats–Redfern, was used for the kinetic analysis, and the various mechanisms have been investigated. Some high-quality fitting mechanisms were identified and used to estimate the thermodynamic properties. As the generation of pyrolysis gases for chemical/energy production is important to the overall process applicability, TGA-coupled mass spectrometry was used to analyse the pyrogas for individual and blend samples. By comparing the devolatilization properties of the blend with single feedstocks, the presence of chemical interactions/synergistic effects between the vegetable samples in the blend was validated. The model, based on a first-order reaction mechanism, was found to be the best-fitting model for predicting the pyrolysis kinetics. The calculated thermodynamic properties (ΔH (enthalpy change $\approx$ E (activation energy))) demonstrated that pyrolysis of the chosen feedstocks is technically feasible. According to the TGA–MS analysis, blending had a considerable impact on the pyrogas, resulting in CO₂ composition reductions of 17.10%, 9.11%, and 16.79%, respectively, in the cases of tomato, cucumber, and carrot. Overall, this study demonstrates the viability of the pyrolysis of kitchen vegetable waste as a waste management alternative, as well as an effective and sustainable source of pyrogas. Full article

(This article belongs to the Topic Advances in Clean Energies)

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12 pages, 5691 KiB  

Open AccessArticle

Numerical Simulation of Premixed Methane–Air Explosion in a Closed Tube with U-Type Obstacles

by Bin Hao, Jianfen Gao, Bingang Guo, Bingjian Ai, Bingyuan Hong and Xinsheng Jiang

Energies 2022, 15(13), 4909; https://doi.org/10.3390/en15134909 - 5 Jul 2022

Cited by 12 | Viewed by 2148

Abstract

Given the spatial structures and functional requirements, there are a number of different types of obstacles in long and narrow confined spaces that will cause a premixed gas explosion to produce greater overpressure and influence the flame behavior for different obstacles. Because the [...] Read more.

Given the spatial structures and functional requirements, there are a number of different types of obstacles in long and narrow confined spaces that will cause a premixed gas explosion to produce greater overpressure and influence the flame behavior for different obstacles. Because the volume fraction of unburned gas changes with the changing height of the U-type obstacles, we can further study the influence on the volume fraction of the unburned premixed gas for the characteristics of the overpressure and the flame behaviors in the closed tube with the obstacles. The results show that after the premixed gas is successfully ignited in the pipe, the overpressure in the pipe greatly increases as the unburned premixed gas burns between the adjacent plates. Moreover, the increase of the overpressure in the closed duct becomes faster when the decrease of unburned gas becomes faster. The high-pressure areas between the plates move inversely compared with the direction of flame propagation when the height of the U-type increases, whereas the high pressure in the front of the flame moves further when the flame propagation passes all obstacles. In addition, the reversed flow structure of the flame is a coupling result for the overpressure caused by the flame propagation and the vortex between the plates. From the perspective of production safety, this study is a significant basic subject about the characteristics of overpressure and flame behaviors in a closed tube with obstacles. Full article

(This article belongs to the Topic Advances in Clean Energies)

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33 pages, 8874 KiB  

Open AccessArticle

Frequency Modulation Control of Hydraulic Wind Turbines Based on Ocean Used Wind Turbines and Energy Storage

by Lijuan Chen, Pengfei Zheng, Wei Gao, Jishang Jiang, Jiafei Chang, Rukang Wu and Chao Ai

Energies 2022, 15(11), 4086; https://doi.org/10.3390/en15114086 - 1 Jun 2022

Cited by 5 | Viewed by 2422

Abstract

Based on the energy storage type of hydraulic wind turbines (HWTs) and in view of the unit frequency drop problem under high wind power proportion conditions, this paper proposes a method of primary frequency control under maximum power point tracking (MPPT). HWT power [...] Read more.

Based on the energy storage type of hydraulic wind turbines (HWTs) and in view of the unit frequency drop problem under high wind power proportion conditions, this paper proposes a method of primary frequency control under maximum power point tracking (MPPT). HWT power output is affected by wind speed randomness and volatility. In addition, traditional wind turbines do not have inertial adjustment ability, leading to a decrease in the frequency stability of the power system caused by the increase in wind power permeability. In the paper, a hydraulic energy storage system and synchronous generator are combined to carry out primary frequency modulation, and a mathematical model of the hydraulic energy storage system, the hydraulic main transmission system, and the generator active power regulation system after grid connection is established. By analyzing the load changing rules of power systems and frequency fluctuation caused by the power system load after the wind turbine is grid-connected, the variable parameter frequency modulation compensation control strategy of combined turbine-energy storage systems is established, and simulation verification under different load fluctuations is carried out, verifying the effectiveness of the frequency modulation control strategy, which achieves a good control effect for improving the frequency modulation ability of hydraulic wind turbines. Full article

(This article belongs to the Topic Advances in Clean Energies)

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21 pages, 9798 KiB  

Open AccessArticle

Interrogating the Installation Gap and Potential of Solar Photovoltaic Systems Using GIS and Deep Learning

by Sumit Kalyan and Qian (Chayn) Sun

Energies 2022, 15(10), 3740; https://doi.org/10.3390/en15103740 - 19 May 2022

Cited by 5 | Viewed by 2971

Abstract

Non-renewable-resource consumption and global greenhouse-gas (GHG) emissions are critical issues that pose a significant threat to sustainable development. Solar energy is a promising source to generate renewable energy and an appealing alternative electricity source for households. The primary goal of this research is [...] Read more.

Non-renewable-resource consumption and global greenhouse-gas (GHG) emissions are critical issues that pose a significant threat to sustainable development. Solar energy is a promising source to generate renewable energy and an appealing alternative electricity source for households. The primary goal of this research is to detect the rooftops that have no solar photovoltaic (PV) system deployed on them but that receive moderate to high solar-energy radiation using the Geographic Information System (GIS) and deep-learning techniques. Although various studies have been conducted on this subject, not many addressed these two issues simultaneously at a residential level. Identifying the installed solar PV systems in a large area can be expensive and time-consuming work if performed manually. Therefore, the deep-learning algorithm is an emerging alternative method to detect objects using aerial images. We employed the Single-Shot-Detector (SSD) model with the backbone of residual neural network 34 (ResNet34) to detect the solar PV systems and used GIS software to compute solar isolation and calculate the electricity production estimate (EPE) of each rooftop. Our results show that the SSD model detected 6010 solar panels on 4150 properties with an accuracy of 78% and observed that there were 176 Statistical Area 1s (SA1s) that had no rooftops with solar PV systems installed. Moreover, the total electricity production from the suitable area was estimated at over 929.8 Giga Watt-hours (GWhs) annually. Finally, the relation between solar-PV-system density and EPE was also identified using the bivariant correlation technique. Detecting the existing solar PV systems is useful in a broad range of applications including electricity-generation prediction, power-plant-production management, uncovering patterns between regions, etc. Examination of the spatial distribution of solar-energy potential in a region and performing an overlay analysis with socio-economic factors can help policymakers to understand the explanation behind the pattern and strategize the incentives accordingly. Full article

(This article belongs to the Topic Advances in Clean Energies)

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16 pages, 3838 KiB  

Open AccessArticle

Analysis and Development of a Small-Scale Supercritical Carbon Dioxide (sCO₂) Brayton Cycle

by Raj C. Patel, Diego C. Bass, Ganza Prince Dukuze, Angelina Andrade and Christopher S. Combs

Energies 2022, 15(10), 3580; https://doi.org/10.3390/en15103580 - 13 May 2022

Cited by 9 | Viewed by 3184

Abstract

Carbon dioxide’s (CO₂) ability to reach the supercritical phase (7.39 MPa and 304.15 K) with low thermal energy input is an advantageous feature in power generation design, allowing for the use of various heat sources in the cycle. A small-scale supercritical [...] Read more.

Carbon dioxide’s (CO₂) ability to reach the supercritical phase (7.39 MPa and 304.15 K) with low thermal energy input is an advantageous feature in power generation design, allowing for the use of various heat sources in the cycle. A small-scale supercritical carbon dioxide (sCO₂) power cycle operating on the principle of a closed-loop Brayton cycle is currently under construction at The University of Texas at San Antonio, to design and develop a small-scale indirect-fired sCO₂ Brayton cycle, acquire validation data of the cycle’s performance, and compare the cycle’s performance to other cycles operating in similar conditions. The power cycle consists of four principal components: A reciprocating piston compressor, a heating source, a reciprocating piston expander to produce power, and a heat exchanger to dissipate excess heat. The work explained in the present manuscript describes the theory and analysis conducted to design the piston expander, heating source, and heat exchanger in the cycle. Theoretical calculations indicate that using sCO₂ for the Brayton cycle generates 4.5 kW of power with the inlet pressure and temperature of 17.23 MPa and 358.15 K to the piston expander. Based on the fully isentropic conditions, the thermal efficiency of the system is estimated to be 12.75%. Full article

(This article belongs to the Topic Advances in Clean Energies)

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16 pages, 2290 KiB  

Open AccessArticle

Liquid Air Energy Storage System (LAES) Assisted by Cryogenic Air Rankine Cycle (ARC)

by Mylena Vieira Pinto Menezes, Icaro Figueiredo Vilasboas and Julio Augusto Mendes da Silva

Energies 2022, 15(8), 2730; https://doi.org/10.3390/en15082730 - 8 Apr 2022

Cited by 8 | Viewed by 4266

Abstract

Energy storage plays a significant role in the rapid transition towards a higher share of renewable energy sources in the electricity generation sector. A liquid air energy storage system (LAES) is one of the most promising large-scale energy technologies presenting several advantages: high [...] Read more.

Energy storage plays a significant role in the rapid transition towards a higher share of renewable energy sources in the electricity generation sector. A liquid air energy storage system (LAES) is one of the most promising large-scale energy technologies presenting several advantages: high volumetric energy density, low storage losses, and an absence of geographical constraints. The disadvantages of LAES systems lay on the high investment cost, large-scale requirements, and low round-trip efficiency. This paper proposes a new configuration using an air Rankine cycle (ARC) to reduce the exergy destruction during heat-exchanging in the liquefaction process while reducing liquefaction power consumption. The addition of the ARC increases the round-trip efficiency of the LAES from 54.1% to 57.1%. Furthermore, the energy consumption per kg of liquid air drops 5.3% in comparison to the base case LAES system. The effects of compression, storage, and pumping pressure on the system performance are investigated by parametric analysis. The results from exergy analysis show that the overall exergy destruction is decreased by 2% and a higher yield of liquid air can be achieved. The results reveal that the increase in the yield of liquid air is more important to the overall efficiency than the power that is generated by the Rankine itself. From an economic viewpoint, the proposed system has a better economic performance than the base case LAES system, decreasing the levelized cost of storage (LCOS) by almost 2%. The proposed configuration may improve the performance and economic competitiveness of LAES systems. Full article

(This article belongs to the Topic Advances in Clean Energies)

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22 pages, 4003 KiB  

Open AccessArticle

The Hydrolysis of Ball-Milled Aluminum–Bismuth–Nickel Composites for On-Demand Hydrogen Generation

by Jamey Davies, Stephanus P. Du Preez and Dmitri G. Bessarabov

Energies 2022, 15(7), 2356; https://doi.org/10.3390/en15072356 - 24 Mar 2022

Cited by 20 | Viewed by 2861

Abstract

The hydrolysis of aluminum (Al) is a promising method for on-demand hydrogen generation for low-power proton exchange membrane fuel cell (PEMFC) applications. In this study, Al composites were mechanochemically activated using bismuth (Bi) and nickel (Ni) as activation compounds. The main objective was [...] Read more.

The hydrolysis of aluminum (Al) is a promising method for on-demand hydrogen generation for low-power proton exchange membrane fuel cell (PEMFC) applications. In this study, Al composites were mechanochemically activated using bismuth (Bi) and nickel (Ni) as activation compounds. The main objective was to determine the effects of Bi and Ni on Al particles during mechanochemical processing, and the hydrolysis activity of the Al-Bi-Ni composites. Successfully formulated ternary Al-Bi-Ni composites were hydrolyzed with de-ionized water under standard ambient conditions to determine the reactivity of the composite (extent of hydrogen production). Scanning electron microscopy (SEM) showed that Bi and Ni were distributed relatively uniformly throughout the Al particles, resulting in numerous micro-galvanic interactions between the anodic Al and cathodic Bi/Ni during hydrolysis reaction. The addition of >1 wt% Ni resulted in incomplete activation of Al, and such composites were non-reactive. All successfully prepared composites had near-complete hydrogen yields. X-ray diffraction (XRD) showed that no mineralogical interaction occurred between Al, Bi, and/or Ni. The main phases detected were Al, Bi, and minute traces of Ni (ascribed to low Ni content). In addition, the effect of the mass ratio (mass Al:mass water) and water quality were also determined. Full article

(This article belongs to the Topic Advances in Clean Energies)

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15 pages, 8692 KiB  

Open AccessArticle

A New Method for Capturing CO₂ from Effluent Gases Using a Rice-Based Product

by Ameera F. Mohammad, Abeer F. Dar Saleh, Maatouk Khoukhi and Ali H. Al-Marzouqi

Energies 2022, 15(6), 2287; https://doi.org/10.3390/en15062287 - 21 Mar 2022

Cited by 4 | Viewed by 2834

Abstract

In 2013, UAE imported around 772 million kilograms of rice, making it one of the largest consumers of this popular grain in the world. However, 40% of rice available in the market is discarded, contributing to the country’s CO₂ footprint. Given that [...] Read more.

In 2013, UAE imported around 772 million kilograms of rice, making it one of the largest consumers of this popular grain in the world. However, 40% of rice available in the market is discarded, contributing to the country’s CO₂ footprint. Given that CO₂ emissions are recognized as a significant contributor to climate change and efforts aimed at their reduction are proving insufficient for combatting the global increase in temperature, various approaches aimed at its removal from the atmosphere have been proposed. The goal of this study is to contribute to this initiative by proposing a new method for CO₂ removal based on a special gas contact device filled with buffered puffed rice cakes obtained by heating in a purposely designed sealed chamber at high pressure to obtain layers with 9−12 mm thickness. The resulting cakes are subsequently immersed in a sodium hydroxide liquor (0.25−2.5 M) to increase the moisture content to 5% and pH to >11.0. In the experiments, different rice structures (stacked layers, rice grains, and multi-spaced layers) were tested, varying the CO₂ percentage in the simulated effluent gas (1−15%). The highest CO₂ uptake value (7.52 × 10⁻³ mole CO₂/cm² rice cake surface area) was achieved using 10% CO₂ and a 500 mL/min flow rate with rice cakes of 80 mm diameter, comprising 12 mm thick layers that occupied 20% of the device volume. These results indicate that the proposed design exhibits high CO₂ removal efficiency and should be further optimized in future investigations. Full article

(This article belongs to the Topic Advances in Clean Energies)

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11 pages, 3466 KiB  

Open AccessArticle

Combustion Performance and Low NOx Emissions of a Dimethyl Ether Compression-Ignition Engine at High Injection Pressure and High Exhaust Gas Recirculation Rate

by Inmo Youn and Joonho Jeon

Energies 2022, 15(5), 1912; https://doi.org/10.3390/en15051912 - 5 Mar 2022

Cited by 10 | Viewed by 3211

Abstract

Dimethyl ether (DME) is a promising alternative to diesel for compression-ignition (CI) engines used in various industrial applications. However, the high nitrogen oxide (NOx) emissions of DME combustion have restricted its use. The primary cause of high NOx emissions is a high combustion [...] Read more.

Dimethyl ether (DME) is a promising alternative to diesel for compression-ignition (CI) engines used in various industrial applications. However, the high nitrogen oxide (NOx) emissions of DME combustion have restricted its use. The primary cause of high NOx emissions is a high combustion temperature. In this study, a high exhaust gas recirculation (EGR) rate was used when testing a common-rail direct injection CI engine suitable (with minor modifications) for a passenger car. A modified fuel supply system created high injection pressure during evaluation of combustion performance. The physical and chemical properties of DME were the principal determinants of the ignition delay, combustion speed, and heat release rate. Although a high injection pressure accelerated formation of the fuel-air mixture and the combustion speed, combustion performance deteriorated with increased NOx emissions. An increased EGR rate affected combustion and the NOx concentration. A high EGR rate effectively reduced NOx formation and emission under low-temperature combustion conditions. Also, the good DME combustion characteristics were maintained when the EGR rate was high, unlike for an ultra-low sulfur diesel engine. Full article

(This article belongs to the Topic Advances in Clean Energies)

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15 pages, 3921 KiB  

Open AccessArticle

Improvements in the Water Retention Characteristics and Thermophysical Parameters of Backfill Material in Ground Source Heat Pumps by a Molecular Sieve

by Tingting Luo, Peng Pei, Yixia Chen, Dingyi Hao and Chen Wang

Energies 2022, 15(5), 1801; https://doi.org/10.3390/en15051801 - 28 Feb 2022

Cited by 3 | Viewed by 2737

Abstract

The thermophysical properties of backfill material (BM) in a heat exchange borehole significantly influence the heat exchange effect of ground source heat pumps (GSHPs). Several treatments such as compaction and adding bentonite, cement, and fine sands are often used to improve the thermophysical [...] Read more.

The thermophysical properties of backfill material (BM) in a heat exchange borehole significantly influence the heat exchange effect of ground source heat pumps (GSHPs). Several treatments such as compaction and adding bentonite, cement, and fine sands are often used to improve the thermophysical properties. In this study, a 3A molecular sieve (3A-MS), a type of porous material, was added to the BM to enhance its water maintaining capacity. Three types of backfill materials with different additive contents, named as BM-0, BM-1, and BM-2, were examined. The variation of the BM properties such as the soil–water characteristic curve (SWCC), thermal conductivity, specific heat capacity, and thermal diffusivity with the groundwater content were investigated through a series of experiments and simulations. A scanning electron microscope (SEM), an energy dispersive spectrometer (EDS), and the BET method for specific surface area pore size analysis were used to characterize the material. The results indicated that the specific heat capacity improved with the water content whereas the thermal conductivity and thermal diffusivity decreased with the water content. The variation of the buried pipe outlet temperature with the change of the thermal physical parameters of the BM were researched by a numerical simulation and theoretical calculations; the results showed that BM-2 could raise the heat transfer rate per meter by 45.9% in summer and 118.4% in winter compared with the backfill materials without groundwater (NW). The research results provide theoretical support for the improvement of BM for ground source heat pump projects where abundant groundwater is available. Full article

(This article belongs to the Topic Advances in Clean Energies)

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14 pages, 1815 KiB  

Open AccessArticle

Influences of Crest Vertical Curve Curvature on Exhaust Emissions of Heavy-Duty Diesel Trucks at Grade Change Point Section in Highway

by Xingli Jia, Xuefang Qin, Wuxiao Zhou, Xingpeng Chen and Shuangqing Li

Energies 2022, 15(4), 1506; https://doi.org/10.3390/en15041506 - 17 Feb 2022

Cited by 2 | Viewed by 3261

Abstract

The vertical curve is a major factor affecting vehicle exhaust (CO₂, CO, NO_x, PM2.5) emissions. This article takes a heavy-duty diesel truck as a typical vehicle, combining instantaneous speed, acceleration and the vehicle-specific power VSP to divide the operating [...] Read more.

The vertical curve is a major factor affecting vehicle exhaust (CO₂, CO, NO_x, PM2.5) emissions. This article takes a heavy-duty diesel truck as a typical vehicle, combining instantaneous speed, acceleration and the vehicle-specific power VSP to divide the operating mode, and the exhaust emission of a heavy-duty diesel truck is then calculated by using MOVES. Finally, the environmental modification factors (EMFs) are used to evaluate the influence of curvature change on the exhaust emissions. The results show that CO₂ and PM2.5 emissions of heavy-duty diesel trucks are increasing with the curvature of the crest vertical curve changing; with the increase and decrease of curvature K of the crest vertical curve by 50%, CO and NO_x emissions showed an increasing trend. Among the four main emissions, CO₂ emission amount is the largest, followed by NO_x, CO and PM2.5. The emission rates of CO₂ and PM2.5 increase with the increase of curvature of the crest vertical curve, and the minimum values of CO₂ and PM2.5 emission rates are 46.7 g/s and 0.022 g/s, respectively. The emission rates of CO and NO_x increase with the increase of curvature. The minimum point of emission rates of CO and NO_x are 0.042 g/s and 0.259 g/s, respectively. Full article

(This article belongs to the Topic Advances in Clean Energies)

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57 pages, 1502 KiB  

Open AccessReview

Energy-Based Approaches in Estimating Actual Evapotranspiration Focusing on Land Surface Temperature: A Review of Methods, Concepts, and Challenges

by Mercedeh Taheri, Abdolmajid Mohammadian, Fatemeh Ganji, Mostafa Bigdeli and Mohsen Nasseri

Energies 2022, 15(4), 1264; https://doi.org/10.3390/en15041264 - 9 Feb 2022

Cited by 34 | Viewed by 4194

Abstract

The surface energy balance (SEB) model is a physically based approach in which aerodynamic principles and bulk transfer theory are used to estimate actual evapotranspiration. A wide range of different methods have been developed to parameterize the SEB equation; however, few studies addressed [...] Read more.

The surface energy balance (SEB) model is a physically based approach in which aerodynamic principles and bulk transfer theory are used to estimate actual evapotranspiration. A wide range of different methods have been developed to parameterize the SEB equation; however, few studies addressed solutions to the SEB considering the land surface temperature (LST). Therefore, in the current review, a clear and comprehensive classification is provided for energy-based approaches considering the key role of LST in solving the energy budget. In this regard, three general approaches are presented using LSTs derived by climate and land surface models (LSMs), satellite-based data, and energy balance closure. In addition, this review surveys the concepts, required inputs, and assumptions of energy-based LSMs and SEB algorithms in detail. The limitations and challenges of aforementioned approaches including land surface temperature, surface energy imbalance, and calculation of surface and aerodynamic resistance network are also assessed. According to the results, since the accuracy of resulting LSTs are affected by weather conditions, surface energy closure, and use of vegetation/meteorological information, all approaches are faced with uncertainties in determining ET. In addition, for further study, an interactive evaluation of water and energy conservation laws is recommended to improve the ET estimation accuracy. Full article

(This article belongs to the Topic Advances in Clean Energies)

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19 pages, 4449 KiB  

Open AccessReview

Review of the Current Status of Ammonia-Blended Hydrogen Fuel Engine Development

by Xiaowei Xu, Enlong Liu, Neng Zhu, Fanfu Liu and Feng Qian

Energies 2022, 15(3), 1023; https://doi.org/10.3390/en15031023 - 29 Jan 2022

Cited by 42 | Viewed by 7660

Abstract

As fossil fuels continue to be extracted and used, issues such as environmental pollution and energy scarcity are surfacing. For the transportation industry, the best way to achieve the goal of “carbon neutrality” is to research efficient power systems and develop new alternative [...] Read more.

As fossil fuels continue to be extracted and used, issues such as environmental pollution and energy scarcity are surfacing. For the transportation industry, the best way to achieve the goal of “carbon neutrality” is to research efficient power systems and develop new alternative fuels. As the world’s largest product of chemicals, ammonia is a new renewable fuel with good combustion energy. It can be used as an alternative fuel to reduce carbon emissions because of its proven production process, low production and transportation costs, safe storage, the absence of carbon-containing compounds in its emissions, and its future recyclability. This paper firstly introduces the characteristics of ammonia fuel engine and its problems; then it summarizes the effects of various ammonia-blended fuels on the combustion and emission characteristics of the engine from the combustion problem of ammonia-blended engine; then the fuel storage of ammonia-blended hydrogen is discussed, the feasibility of hydrogen production instead of hydrogen storage is introduced. Full article

(This article belongs to the Topic Advances in Clean Energies)

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