Energies

30 pages, 9582 KiB

Open AccessReview

A Comparative Analysis of Maximum Power Point Techniques for Solar Photovoltaic Systems

by Ashwin Kumar Devarakonda, Natarajan Karuppiah, Tamilselvi Selvaraj, Praveen Kumar Balachandran, Ravivarman Shanmugasundaram and Tomonobu Senjyu

Energies 2022, 15(22), 8776; https://doi.org/10.3390/en15228776 - 21 Nov 2022

Cited by 42 | Viewed by 3574

Abstract

The characteristics of a PV (photovoltaic) module is non-linear and vary with nature. The tracking of maximum power point (MPP) at various atmospheric conditions is essential for the reliable operation of solar-integrated power generation units. This paper compares the most widely used maximum [...] Read more.

The characteristics of a PV (photovoltaic) module is non-linear and vary with nature. The tracking of maximum power point (MPP) at various atmospheric conditions is essential for the reliable operation of solar-integrated power generation units. This paper compares the most widely used maximum power point tracking (MPPT) techniques such as the perturb and observe method (P&O), incremental conductance method (INC), fuzzy logic controller method (FLC), neural network (NN) model, and adaptive neuro-fuzzy inference system method (ANFIS) with the modern approach of the hybrid method (neural network + P&O) for PV systems. The hybrid method combines the strength of the neural network and P&O in a single framework. The PV system is composed of a PV panel, converter, MPPT unit, and load modelled using MATLAB/Simulink. These methods differ in their characteristics such as convergence speed, ease of implementation, sensors used, cost, and range of efficiencies. Based on all these, performances are evaluated. In this analysis, the drawbacks of the methods are studied, and wastage of the panel’s available output energy is observed. The hybrid technique concedes a spontaneous recovery during dynamic changes in environmental conditions. The simulation results illustrate the improvements obtained by the hybrid method in comparison to other techniques. Full article

(This article belongs to the Section K: State-of-the-Art Energy Related Technologies)

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32 pages, 5061 KiB

Open AccessReview

Advances in Indoor Cooking Using Solar Energy with Phase Change Material Storage Systems

by Selvaraj Balachandran and Jose Swaminathan

Energies 2022, 15(22), 8775; https://doi.org/10.3390/en15228775 - 21 Nov 2022

Cited by 5 | Viewed by 4917

Abstract

One of the key areas of the UN’s sustainable development goals is growing affordable and clean energy. Utilizing solar energy that is now accessible will significantly lessen the demand for fossil fuels. Around the world, cooking is a crucial activity for homes and [...] Read more.

One of the key areas of the UN’s sustainable development goals is growing affordable and clean energy. Utilizing solar energy that is now accessible will significantly lessen the demand for fossil fuels. Around the world, cooking is a crucial activity for homes and uses a lot of non-renewable energy. Uncontrolled firewood usage results in deforestation, whereas using biomass-related fuels in inefficient stoves can result in smoke emanating from the kitchen and associated health issues. The benefits of solar cooking include reducing smoke-related problems and saving on fossil fuels and firewood. Applying thermal storage systems in cooking helps households have all-day cooking. This review article presents the research and development of a solar cooking system that transfers solar energy into the kitchen and integrates with the thermal energy storage system, finding the factors affecting indoor solar cooking performance. Adding portable cooking utensils helps in improved solar indoor cooking. Multiple phase change materials arranged in cascaded to store thermal energy helps in quick heat transfer rate, thus enabling better and faster cooking. A novel indoor solar cooker with an innovative arrangement of evacuated tube-based compound concentrating parabolic (CPC) collectors with a cascaded latent heat thermal energy storage system is proposed and needs to be tested under actual meteorological conditions. Full article

(This article belongs to the Special Issue Advances in Solar Thermal Energy Storage Technologies)

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18 pages, 5958 KiB

Open AccessArticle

Enhancing the Efficiency of Integrated Energy Systems by the Redistribution of Heat Based on Monitoring Data

by Andrii Radchenko, Mykola Radchenko, Hanna Koshlak, Roman Radchenko and Serhiy Forduy

Energies 2022, 15(22), 8774; https://doi.org/10.3390/en15228774 - 21 Nov 2022

Cited by 13 | Viewed by 1871

Abstract

Integrated energy systems (IES) for combined power, heat and refrigeration supply achieved a wide application due to high flexibility in matching current loading. So as electricity is easily convertible into any other form of energy, gas engines are widely applied as driving engines [...] Read more.

Integrated energy systems (IES) for combined power, heat and refrigeration supply achieved a wide application due to high flexibility in matching current loading. So as electricity is easily convertible into any other form of energy, gas engines are widely applied as driving engines characterized by high electrical and overall efficiency of about 45% and 90%, respectively. However, the highest thermal efficiency is achieved at full matching heat generated by the engine and heat transformed. This is often impossible in actual practice, especially if the heat is transformed into refrigeration by the most efficient and widespread absorption lithium-bromide chillers (ACh) and the heat not consumed by the ACh is removed from the atmosphere through an emergency radiator. The unused heat might be transformed by an ejector chiller (ECh) as the simplest and cheapest. So as the thermodynamic efficiency of any combustion engine is influenced essentially by the sucked air temperature, the excessive refrigeration produced by the ECh, is used for IES cooling to generate additional electricity and increase the electrical and overall efficiency of the engine. Such a redistribution of heat enables the enhancement of the efficiency of IES with an absorption-ejector chiller (AECh). The modified criteria for the comparative estimation of thermodynamic efficiency of innovative IESs with AEChs without overgenerated heat lost against a typical IES with an ACh and heat lost are proposed. In contrast to well-known electrical and heat efficiency, it considers the magnitude of heat loss and enables us to compare the heat efficiency of any version of transforming heat to refrigeration with an ideal basic version of IES based on a highly efficient ACh, transforming all the heat removed from the engine without heat loss. Some alternative scheme decisions for heat recovery systems have been developed based on monitoring data. They might be easily implemented into a typical IES with ACh. Full article

(This article belongs to the Special Issue Latest Research of Building Heat and Mass Transfer)

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9 pages, 2585 KiB

Open AccessArticle

Experimental Analysis for Determining Potential of Wastewater Sludge Mixed with Degraded Biomass as Substrates for Biogas Production

by Adrian Eugen Cioabla, Francisc Popescu and Timotei Bogdan Bacos

Energies 2022, 15(22), 8773; https://doi.org/10.3390/en15228773 - 21 Nov 2022

Viewed by 1761

Abstract

In the context of increased energy demands and finding solutions for energetic autonomy, the use of waste base materials has increased in recent years in all areas of research. In this context, waste waters, sludge or slurry, biodegradable materials, second generation effluents, and [...] Read more.

In the context of increased energy demands and finding solutions for energetic autonomy, the use of waste base materials has increased in recent years in all areas of research. In this context, waste waters, sludge or slurry, biodegradable materials, second generation effluents, and their byproducts are some of the key substrates of interest to obtain biogas through AD (anaerobe digestion). The goal is to utilize these materials as a base for the generation of renewable energy and thereby make it the main source of energy for households or industries. This paper aims to characterize, from a physical and chemical point of view, wastewater from Timis county as a base substrate material in the co-fermentation process with cereal residual biomass. We aimed to determine the energetic potential of the wastewater and perform preliminary testing at a small and pilot-sized experimental installation for biogas production with Timis wastewater as the main energy carrier. The novelty of the paper stems from the use of a patented pilot installation as our experimental approach, as well as the use of a different comparative scale co-fermentation process for biogas production. The conclusions will be traced relative to the obtained results, and preliminary solutions will be proposed for further avenues on this topic. Full article

(This article belongs to the Special Issue Advanced Technologies for Wastewater and Solid Waste Treatment)

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17 pages, 7680 KiB

Open AccessArticle

Consequence of Blowby Flow and Idling Time on Oil Consumption and Particulate Emissions in Gasoline Engine

by Vincent Berthome, David Chalet and Jean-François Hetet

Energies 2022, 15(22), 8772; https://doi.org/10.3390/en15228772 - 21 Nov 2022

Cited by 3 | Viewed by 2505

Abstract

Pollutant emission standards and, in particular, those concerning particles from an internal combustion engine (ICE) are becoming increasingly restrictive. Thus, it is important to determine the main factors related to the production of particulate matter. In this article, the phenomenon of oil sweeping [...] Read more.

Pollutant emission standards and, in particular, those concerning particles from an internal combustion engine (ICE) are becoming increasingly restrictive. Thus, it is important to determine the main factors related to the production of particulate matter. In this article, the phenomenon of oil sweeping by the blowby gases between the rings/piston/cylinder is investigated. First, a blowby gas simulation model based on experimental results from a Turbocharged Gasoline Direct Injection (TGDI) is developed. From this model, it is possible to characterise the amount of oil swept by the blowby gases. This depends on the endgap position of both the compression and sealing rings. It also depends on the intensity of the blowby flow rate, which is highest at low rpm and high load. At 1500 rpm and full load, this flowrate exceeds 25 mg.cycle⁻¹. From this result, it is possible to quantify the amount of oil swept by these gases as a function of the endgap position. For

θ_{r i n g s} = 180 °,

the quantity of oil swept rises to 20 µg.cycle⁻¹ while for

θ_{r i n g s} = 30 °,

this decreases to 6 µg.cycle⁻¹. The oil concentration of the blowby gas has a direct impact on the particulate emissions because the oil concentration of the backflow gas is inversely proportional to the blowby gas flowrate. As the backflow gases return to the cylinder, the oil oxidises and produces particles. Therefore, it is essential to control the oil concentration of the backflow gases. In addition, the simulation model shows the blowby flowrate becomes negative and decreases to −3.4 mg. cycle⁻¹ in idle conditions. The amount of oil swept by the blowby is no longer directed towards the oil pan, but towards the piston crown. This phenomenon of oil storage of the piston crown in idle condition is proportional to the duration of the idle time. In order to confirm these results, experimental tests are carried out on a TGDI engine. It appears that when the idling time changes from 0 s to 7 s between two strictly identical accelerations, the level of particulate emissions is multiplied by 1.3. When the idling time changes from 0 s to 22 s between two strictly identical accelerations, the level of particulate emissions is multiplied by 3. These results confirm the mechanism of oil storage at idle highlighted by the simulation model. Full article

(This article belongs to the Special Issue NOx, PM and CO₂ Emission Reduction in Fuel Combustion Processes)

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17 pages, 2304 KiB

Open AccessArticle

The Role of Renewable Energy Sources in Electricity Production in Poland and the Background of Energy Policy of the European Union at the Beginning of the COVID-19 Crisis

by Piotr Bórawski, Aneta Bełdycka-Bórawska, Lisa Holden and Tomasz Rokicki

Energies 2022, 15(22), 8771; https://doi.org/10.3390/en15228771 - 21 Nov 2022

Cited by 9 | Viewed by 3450

Abstract

Electricity production in Poland is stable and ranges from 160–170 TWH a year. The share of renewable energy sources (RES) is increasing. Poland increased its share from 6.9% in 2010 to 12.7% in 2019 and 16.1% in 2020. The share of hard and [...] Read more.

Electricity production in Poland is stable and ranges from 160–170 TWH a year. The share of renewable energy sources (RES) is increasing. Poland increased its share from 6.9% in 2010 to 12.7% in 2019 and 16.1% in 2020. The share of hard and brown coal decreased in Poland from 87.8% in 2010 to 73.5% in 2019. Wind energy (9.2%) and natural gas (9.2%) are the most important sources of RES in electricity production. The purpose of this research is to discover the changes in renewable energy production, and the impact on electricity production in Poland. Our research showed the extent of development of RES in Poland and other countries of the European Union. The share of renewable energy sources in electricity production increased as the effect of energy policy of the European Union. We also evaluated the impact of the COVID-19 crisis on the renewable energy market and electricity production in Poland, and other countries of the European Union. Because of the shortage of data, we presented changes at the beginning of the COVID-19 crisis in 2019–2020. First, we described the sustainable development and energy policy of the European Union. Then, we described and used methods, including regression analysis, as the most important method. We also found that the power capacity in Poland increased, with the increases coming from solar radiation (11,984%), wind energy (437.8%) and biomass installations (324.7%) in 2010–2020. The biggest electricity producers in the EU are France and Germany. These countries also use nuclear energy, which helps to meet the increasing demand. To check the impact of power installed from renewable energy carriers we conducted a regression analysis. This method provided a correlation between electricity production from renewable energy sources and investments in renewable energy carriers. We wanted to discover the impact of RES installations, and their impact on electricity production in Poland. The statistical analysis was based on data from 2010–2020. Our research points out that the most important factors shaping electricity production were installations using energy from solar radiation and hydropower installations. Full article

(This article belongs to the Special Issue The Effect of COVID-19 Pandemic on the Energy Economics and Markets in Central and Eastern Europe)

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23 pages, 1367 KiB

Open AccessArticle

Financial Sector Analysis of Companies in the Energy Industry Listed on the Warsaw Stock Exchange

by Katarzyna Goldmann and Aleksander Zawadzki

Energies 2022, 15(22), 8770; https://doi.org/10.3390/en15228770 - 21 Nov 2022

Viewed by 3965

Abstract

In times of the pandemic and the beginning of the energy crisis, the financial situation of enterprises operating in the energy generation sector may be a problem. This sector includes companies that generate energy in different ways and from different sources. The aim [...] Read more.

In times of the pandemic and the beginning of the energy crisis, the financial situation of enterprises operating in the energy generation sector may be a problem. This sector includes companies that generate energy in different ways and from different sources. The aim of this study is to determine the general financial situation of enterprises in the energy sector listed on the Warsaw Stock Exchange. The subject of the paper are the annual financial reports of these entities for the years 2015–2021. Tree hypotheses were formulated regarding various aspects of the financial situation of the entities under study. The following research methods were used in this paper: analysis of the literature on the subject and financial statements, and methods of descriptive statistics. The indicators of liquidity, profitability, debt and activity were calculated. The values of the maximum, minimum, median, upper and lower quartiles, the arithmetic mean, kurtosis and skewness were then calculated for each indicator. The increase in energy prices was influenced by the high rate of economic growth and the so-called post-epidemic inflation. This, in turn, was reflected in the performance of companies in the energy sector, resulting in increased profitability. The research carried out by the authors confirmed that the sector financial indicators of energy enterprises with a dominant share of private capital are concentrated closer to the average value than enterprises with a dominant share of the State Treasury. The financial situation of coal power engineering companies is more stable than that of renewable energy companies. Full article

(This article belongs to the Special Issue Energy Consumption in EU Countries)

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20 pages, 5961 KiB

Open AccessArticle

Distributed Secondary Control for Battery Management in a DC Microgrid

by Alexander Paul Moya, Polo Josue Pazmiño, Jacqueline Rosario Llanos, Diego Ortiz-Villalba and Claudio Burgos

Energies 2022, 15(22), 8769; https://doi.org/10.3390/en15228769 - 21 Nov 2022

Cited by 4 | Viewed by 2196

Abstract

This research presents the design and simulation of a distributed secondary control based on a consensus algorithm for the efficient management of an isolated DC microgrid (MG-DC) that secures the distribution of active power according to the capacities of each storage unit, reducing [...] Read more.

This research presents the design and simulation of a distributed secondary control based on a consensus algorithm for the efficient management of an isolated DC microgrid (MG-DC) that secures the distribution of active power according to the capacities of each storage unit, reducing duty cycles and extending its life cycle. The balance of powers is fulfilled through a photovoltaic (PV) generation unit and an energy storage system (ESS) based on batteries. The PV Boost converter has a maximum power point tracking (MPPT) controller based on the perturb and observe (P & O) method. In contrast, a Buck–Boost converter is integrated into each battery, which is bidirectionally controlled through a local controller and a primary droop control that balances the required power at the loads. It produces a voltage deviation on the DC bus. To compensate for this deviation, a distributed secondary control strategy based on consensus is proposed to restore the voltage while managing the power sharing according to the capacities of each battery. It allows for the improvement of its life cycle, which is shown in the state of charge (SOC) index, thus extending its life cycle. The controllers are evaluated for solar re-source changes, load changes, and different storage capacities. Full article

(This article belongs to the Special Issue Control and Optimization in a DC Microgrid)

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15 pages, 1251 KiB

Open AccessReview

Review on the Conflicts between Offshore Wind Power and Fishery Rights: Marine Spatial Planning in Taiwan

by Hsin-Hua Tsai, Huan-Sheng Tseng, Chun-Kai Huang and Su-Chun Yu

Energies 2022, 15(22), 8768; https://doi.org/10.3390/en15228768 - 21 Nov 2022

Cited by 4 | Viewed by 3074

Abstract

In recent years, Taiwan has firmly committed itself to pursue the green energy transition and a nuclear-free homeland by 2025, with an increase in renewable energy from 5% in 2016 to 20% in 2025. Offshore wind power (OWP) has become a sustainable and [...] Read more.

In recent years, Taiwan has firmly committed itself to pursue the green energy transition and a nuclear-free homeland by 2025, with an increase in renewable energy from 5% in 2016 to 20% in 2025. Offshore wind power (OWP) has become a sustainable and scalable renewable energy source in Taiwan. Maritime Spatial Planning (MSP) is a fundamental tool to organize the use of the ocean space by different and often conflicting multi-users within ecologically sustainable boundaries in the marine environment. MSP is capable of definitively driving the use of offshore renewable energy. Lessons from Germany and the UK revealed that MSP was crucial to the development of OWP. This paper aims to evaluate how MSP is able to accommodate the exploitation of OWP in Taiwan and contribute to the achievement of marine policy by proposing a set of recommendations. It concludes that MSP is emerging as a solution to be considered by government institutions to optimize the multiple use of the ocean space, reduce conflicts and make use of the environmental and economic synergies generated by the joint deployment of OWP facilities and fishing or aquaculture activities for the conservation and protection of marine environments. Full article

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30 pages, 2173 KiB

Open AccessArticle

Modern Trends in Global Energy and Assessment of the Ever-Increasing Role of Digitalization

by Igor Anatolyevich Maksimtsev, Konstantin Borisovich Kostin and Anastasia Arturovna Berezovskaya

Energies 2022, 15(22), 8767; https://doi.org/10.3390/en15228767 - 21 Nov 2022

Cited by 5 | Viewed by 2807

Abstract

The global changes which are affecting countries at the moment act as a ‘censor’ of modern energy relations and energy market development strategies in general. The development of the energy market is no longer considered in terms of its efficiency but more in [...] Read more.

The global changes which are affecting countries at the moment act as a ‘censor’ of modern energy relations and energy market development strategies in general. The development of the energy market is no longer considered in terms of its efficiency but more in terms of its survivability under the influence of external environmental factors and its ability to maintain an acceptable level of energy safety. In order to fully balance a country’s internal interests and increase its competitiveness in the global energy market, the importance of the problem of choosing a development strategy—following the path of energy independence or cooperative development—is becoming evident. The purpose of this paper is to identify an effective energy strategy for a country under the influence of contemporary challenges. The object of the study is the Russian energy market and the energy companies as its key players. In this context, it examines the situations where Russia and other energy market players are unequally affected by external environmental factors. Particular emphasis is placed on the possibility of overcoming the negative impact of environmental factors during the implementation of measures aimed at ensuring energy safety, achieving a better environmental situation in the country by reducing CO₂ emissions, and strengthening the country’s position in the global energy market by changing its own energy development strategy. The dependence of the financial outcome of the energy complex companies of the Russian Federation on the factors of the external and internal environment was determined as the main direction of the study. The financial outcome of the Russian energy complex companies in this article serves as a landmark indicator of energy market development. The working hypothesis of the research is the authors’ claim that it is necessary for modern energy companies in Russia, as important participants in the energy market of the country, to transform their strategy in the direction of deepening cooperation under the influence of external and internal environmental factors. The methodological and theoretical framework of this study consists of classical and modern economic science, covering the analysis of energy market dynamics and structure, as well as the theories aimed at selecting the most effective strategies under the influence of external and internal environmental factors. The study is based on the works of domestic and foreign scientists devoted to the issues of competitiveness, strategic planning, and sustainable development in the context of total digitalization. Within the framework of the conducted research, we used methods of system and factor analysis; statistical research methods, in particular the analysis of dynamic changes, as well as correlation and regression analysis; and methods of comparison, analogy, and generalization. An important source of data on the financial result of companies in the Russian energy sector was the materials of the Federal State Statistics Service of the Russian Federation. As a result of this paper, a notable influence of external and internal environmental factors is determined. Among the most significant factors, digitalization is identified as a development trend. It also represents a driver of improvement in Russia’s energy market, both in terms of improving its competitiveness and environmental safety and in terms of strengthening the country’s leadership position in the global energy market. In addition to the findings, this article provides a theoretical contribution and recommendations for the development of theoretical ideas concerning the choice of an effective strategy for the development of Russia’s energy market. Future research directions are also considered, and the implications of the presented analysis for further research are discussed. Full article

(This article belongs to the Special Issue Economy, Social Policy and Forecast Analysis in Energy Industry)

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12 pages, 3145 KiB

Open AccessArticle

Real-Time Measurement of NOx Emissions from Modern Diesel Vehicles Using On-Board Sensors

by Tommaso Selleri, Christian Ferrarese, Jacopo Franzetti, Ricardo Suarez-Bertoa and Dario Manara

Energies 2022, 15(22), 8766; https://doi.org/10.3390/en15228766 - 21 Nov 2022

Cited by 5 | Viewed by 2510

Abstract

In this work, the performance of on-board vehicle exhaust emission sensors is investigated and compared to reference laboratory and on-road instrumentation for two modern diesel light-duty commercial vehicles, type-approved as Euro 6d-TEMP-EVAP-ISC and Euro 6d-ISC-FCM. The first step of the analysis was to [...] Read more.

In this work, the performance of on-board vehicle exhaust emission sensors is investigated and compared to reference laboratory and on-road instrumentation for two modern diesel light-duty commercial vehicles, type-approved as Euro 6d-TEMP-EVAP-ISC and Euro 6d-ISC-FCM. The first step of the analysis was to perform emissions tests in the laboratory and compare the NOx concentrations registered by the vehicle sensors available at the engine-out and tailpipe positions with those recorded by reference laboratory instrumentation. In a second step, tests were also conducted on road, comparing the performance of on-board sensors with those of Portable Emission Measurement System (PEMS) analysers, which were taken as references. The uncertainty related to exhaust flow measurements was also addressed. In particular, emissions factors calculated using the flow rates measured either in the laboratory or on-road were compared to those obtained by computing exhaust flows with on-board recorded data available from the vehicle electronic control unit. Results showed maximum deviations on the order of 34% in laboratory tests and of 21% during on-road measurements. Finally, measurements were also carried out during a diesel particulate filter regeneration event, showing the good performance of the on-board sensors even when high NOx concentrations were present. These conditions can be similar to those experienced in the case of an after-treatment system malfunction or of a high-emitting event, and can thus be of interest for real-time malfunction identification and monitoring. Full article

(This article belongs to the Section I2: Energy and Combustion Science)

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27 pages, 4385 KiB

Open AccessArticle

Environmental and Economic Impact Assessments of a Photovoltaic Rooftop System in the United Arab Emirates

by Haneen Abuzaid and Fatin Samara

Energies 2022, 15(22), 8765; https://doi.org/10.3390/en15228765 - 21 Nov 2022

Cited by 3 | Viewed by 4534

Abstract

The shift toward renewable energy resources, and photovoltaic systems specifically, has gained a huge focus in the past two decades. This study aimed to assess several environmental and economic impacts of a photovoltaic system that installed on the rooftop of an industrial facility [...] Read more.

The shift toward renewable energy resources, and photovoltaic systems specifically, has gained a huge focus in the past two decades. This study aimed to assess several environmental and economic impacts of a photovoltaic system that installed on the rooftop of an industrial facility in Dubai, United Arab Emirates (UAE). The life cycle assessment method was employed to study all the flows and evaluate the environmental impacts, while several economic indicators were calculated to assess the feasibility and profitability of this photovoltaic system. The results showed that the production processes contributed the most to the environmental impacts, where the total primary energy demand was 1152 MWh for the whole photovoltaic system, the total global warming potential was 6.83 × 10^–2 kg CO₂-eq, the energy payback time was 2.15 years, the carbon dioxide payback time was 1.87 years, the acidification potential was 2.87 × 10^–4 kg SO₂-eq, eutrophication potential was 2.45 × 10^–5 kg PO₄³-eq, the ozone layer depletion potential was 4.685 × 10^–9 kgCFC-11-eq, the photochemical ozone creation potential was 3.81 × 10^–5 kg C₂H₄-eq, and the human toxicity potential was 2.38 × 10^–2 kg1,4-DB-eq for the defined function unit of the photovoltaic system, while the economic impact indicators for the whole system resulted in a 3.5 year payback period, the benefit to cost ratio of 11.8, and 0.142 AED/kWh levelized cost of electricity. This was the first study to comprehensively consider all of these impact indicators together. These findings are beneficial inputs for policy- and decision-makers, photovoltaic panel manufacturers, and photovoltaic contractors to enhance the sustainability of their processes and improve the environment. Full article

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17 pages, 2676 KiB

Open AccessArticle

Low-Carbon Transition Pathway Planning of Regional Power Systems with Electricity-Hydrogen Synergy

by Liang Ran, Yaling Mao, Tiejiang Yuan and Guofeng Li

Energies 2022, 15(22), 8764; https://doi.org/10.3390/en15228764 - 21 Nov 2022

Cited by 8 | Viewed by 2152

Abstract

Hydrogen energy leads us in an important direction in the development of clean energy, and the comprehensive utilization of hydrogen energy is crucial for the low-carbon transformation of the power sector. In this paper, the demand for hydrogen energy in various fields is [...] Read more.

Hydrogen energy leads us in an important direction in the development of clean energy, and the comprehensive utilization of hydrogen energy is crucial for the low-carbon transformation of the power sector. In this paper, the demand for hydrogen energy in various fields is predicted based on the support vector regression algorithm, which can be converted into an equivalent electrical load when it is all produced from water electrolysis. Then, the investment costs of power generators and hydrogen energy equipment are forecast considering uncertainty. Furthermore, a planning model is established with the forecast data, initial installed capacity and targets for carbon emission reduction as inputs, and the installed capacity as well as share of various power supply and annual carbon emissions as outputs. Taking Gansu Province of China as an example, the changes of power supply structure and carbon emissions under different scenarios are analysed. It can be found that hydrogen production through water electrolysis powered by renewable energy can reduce carbon emissions but will increase the demand for renewable energy generators. Appropriate planning of hydrogen storage can reduce the overall investment cost and promote a low carbon transition of the power system. Full article

(This article belongs to the Section A5: Hydrogen Energy)

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15 pages, 3506 KiB

Open AccessArticle

Design and Validation of Pitch H-Infinity Controller for a Large Wind Turbine

by Yuan Song, Taesu Jeon, Insu Paek and Bayasgalan Dugarjav

Energies 2022, 15(22), 8763; https://doi.org/10.3390/en15228763 - 21 Nov 2022

Cited by 8 | Viewed by 2046

Abstract

In this study, a pitch H-infinity control algorithm was developed for variable-speed–variable-pitch (VSVP) wind turbines to improve the rotor standard deviation of the wind turbines under normal and extreme wind conditions. The pitch H-infinity control algorithm only uses H-infinity control in the blade [...] Read more.

In this study, a pitch H-infinity control algorithm was developed for variable-speed–variable-pitch (VSVP) wind turbines to improve the rotor standard deviation of the wind turbines under normal and extreme wind conditions. The pitch H-infinity control algorithm only uses H-infinity control in the blade pitch control loop in the rated power region, and conventional torque gain scheduling algorithms are applied in the partial power region. The performance of this controller was verified using simulations of a 5 MW wind turbine using the commercial aeroelastic simulation code Bladed. The performance of the pitch H-infinity controller was compared with that of the conventional proportional-integral (PI) control algorithm under three different operating conditions: normal operating conditions without sensor noise, normal operating conditions with sensor noise, and extreme operating conditions without sensor noise based on the wind turbine design standard by IEC. Based on the simulation results with two different wind speed regions, namely, the transition region and the rated power region, it was found that the proposed pitch H-infinity controller showed better rotor speed standard deviation performance in the three operating conditions and achieved lower standard deviations of the rotor speed and the electrical power without affecting the mean electrical power. Full article

(This article belongs to the Special Issue Advancement in Wind Turbine Technology)

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15 pages, 2938 KiB

Open AccessArticle

Decentralized Model-Reference Adaptive Control Based Algorithm for Power Systems Inter-Area Oscillation Damping

by Tswa-wen Pierre-Patrick Banga-Banga, Carl Kriger and Yohan Darcy Mfoumboulou

Energies 2022, 15(22), 8762; https://doi.org/10.3390/en15228762 - 21 Nov 2022

Cited by 1 | Viewed by 2080

Abstract

Being the primary cause of inter-area oscillations and due to the fact that they limit the generation’s output, Low-Frequency Electromechanical Oscillations (LFEOs) represent a real threat to power system networks. Mitigating their effects is therefore crucial as it may lead to system collapse [...] Read more.

Being the primary cause of inter-area oscillations and due to the fact that they limit the generation’s output, Low-Frequency Electromechanical Oscillations (LFEOs) represent a real threat to power system networks. Mitigating their effects is therefore crucial as it may lead to system collapse if not properly damped. As rotor angle instability is the primary cause of LFEOs, this paper presents a novel Model-Reference Adaptive Control (MRAC) scheme that enhances its stability. The proposed scheme is tested using the Single-Machine Infinite Bus (SMIB) network. The results obtained validate the proposed decentralized control architecture. The robustness of this oscillation damping controller is verified through simulations in MATLAB/SIMULINK. With Gaussian noise added to the structure of the generator to emulate small load variations responsible for the rotor angle instability, the results of the simulations show that the rotor angle remains stable. Furthermore, when subjected to faults, the recovery time is less than 500 ms. Full article

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15 pages, 31059 KiB

Open AccessArticle

Effect of Synthesis Conditions on Capacitive Properties of Porous Carbon Derived from Hemp Bast Fiber

by Michał Bembenek, Volodymyr Kotsyubynsky, Volodymyra Boychuk, Bogdan Rachiy, Ivan Budzulyak, Łukasz Kowalski and Liubomyr Ropyak

Energies 2022, 15(22), 8761; https://doi.org/10.3390/en15228761 - 21 Nov 2022

Cited by 5 | Viewed by 1534

Abstract

A systematic study of the influence of synthesis conditions on the structural, morphological, and electrical properties, as well as the electrochemical performance of hemp fiber-derived carbon materials was performed. An analysis of the capacitive response of carbons obtained under various activation conditions with [...] Read more.

A systematic study of the influence of synthesis conditions on the structural, morphological, and electrical properties, as well as the electrochemical performance of hemp fiber-derived carbon materials was performed. An analysis of the capacitive response of carbons obtained under various activation conditions with additional treatment with HNO₃ and annealing was completed. The contribution of the formation of an electrical double layer at the outer electrode–electrolyte interface, as well as on surfaces inside micropores, has been studied and analyzed in terms of the effect of the turbostratic carbon properties (average lateral size of graphite crystallites, pore size distribution, BET surface area). Full article

(This article belongs to the Special Issue Novel Materials and Technologies for Supercapacitor Applications)

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17 pages, 5390 KiB

Open AccessArticle

Theoretical and Experimental Investigation on Comparing the Efficiency of a Single-Piston Valved Linear Compressor and a Symmetrical Dual-Piston Valved Linear Compressor

by Zhijie Huang, Yuefeng Niu, Yanjie Liu, Yuanli Liu, Chen Zhang, Enchun Xing and Jinghui Cai

Energies 2022, 15(22), 8760; https://doi.org/10.3390/en15228760 - 21 Nov 2022

Cited by 1 | Viewed by 1599

Abstract

The efficiency of the valved linear compressor is very important to the efficiency of the space J-T throttling refrigerator. To compare the efficiency of the single-piston valved linear compressor (SVLC) and the symmetrical dual-piston valved linear compressor (SDVLC), this paper explores the factors [...] Read more.

The efficiency of the valved linear compressor is very important to the efficiency of the space J-T throttling refrigerator. To compare the efficiency of the single-piston valved linear compressor (SVLC) and the symmetrical dual-piston valved linear compressor (SDVLC), this paper explores the factors that affect efficiency. Firstly, this paper analyzes the mechanical vibration system of the linear compressor, the result shows that the efficiency is highest when the external force (current) is in phase with the speed. Then the numerical solutions of the current and velocity are obtained. By comparing the variance and same direction rate of the current and velocity between the SVLC and SDVLC, the reason for the difference in efficiency is explained. Subsequently, the performance of the SVLC and SDVLC are tested on the experimental system. The result shows that the current and velocity of the SDVLC are more in phase, and the isentropic efficiency, volume efficiency and motor efficiency of the SDVLC are all higher than that of the SVLC. Full article

(This article belongs to the Special Issue Advanced Research on High-Energy Performance Compressors)

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17 pages, 5237 KiB

Open AccessArticle

Influence of Different Heat Loads and Durations on the Field Thermal Response Test

by Yongjie Ma, Yanjun Zhang, Yuxiang Cheng, Yu Zhang, Xuefeng Gao, Hao Deng and Xin Zhang

Energies 2022, 15(22), 8759; https://doi.org/10.3390/en15228759 - 21 Nov 2022

Cited by 3 | Viewed by 1550

Abstract

Geothermal energy exhibits considerable development potential in space heating. Shallow geothermal energy stored in the soil in the form of low-grade energy is mainly extracted via the ground source heat pump (GSHP) system. GSHP systems use the subsoil as a heat source, typically [...] Read more.

Geothermal energy exhibits considerable development potential in space heating. Shallow geothermal energy stored in the soil in the form of low-grade energy is mainly extracted via the ground source heat pump (GSHP) system. GSHP systems use the subsoil as a heat source, typically involving a vertical borehole heat exchanger (BHE) to extract heat from the formation. Accurate measurement of the thermal properties of the formation is very important for the design of BHEs. At present, the most common and effective method to measure the thermal conductivity of the formation in the field is the thermal response test (TRT). However, the test conditions (heat load, test time) during the thermal response test can impact the test results. Therefore, in this study, a borehole with a depth of 130 m was evaluated in the field. The TRT module and the distributed thermal response test (DTRT) module based on distributed optical fiber temperature sensor (DOFTS) technology were used to monitor the test with different working conditions in real-time. In the field tests, geothermal conditions and the evolution of the formation temperature with time and depth were determined. Based on the test results under different heat loads and test times, the influence of the test conditions on the thermal conductivity results was analyzed and described. A constant temperature zone was located at a depth from 25 m to 50 m, and an increasing temperature zone was located at a depth from 50 m to 130 m, with a geothermal gradient of 3 °C/100 m. The results showed that the heat load slightly influenced the thermal conductivity test results. At the initial stage of the test, the temperature significantly increased from 0 to 12 h. After reaching the quasi-stable state, the test time slightly influenced the thermal conductivity test results. The characteristics of the formation thermal recovery stage after the test stage were studied. The heat load decreased, which could shorten the time for the formation to recover the initial temperature. The results could provide a basis for the optimization of thermal response test conditions. Full article

(This article belongs to the Section H2: Geothermal)

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20 pages, 1040 KiB

Open AccessArticle

Inter-Fuel Substitution, Technical Change, and Carbon Mitigation Potential in Pakistan: Perspectives of Environmental Analysis

by Muhammad Yousaf Raza and Songlin Tang

Energies 2022, 15(22), 8758; https://doi.org/10.3390/en15228758 - 21 Nov 2022

Cited by 26 | Viewed by 1736

Abstract

Currently, Pakistan is in a stage of urbanization and industrialization, raising its energy demand and supply and carbon dioxide emissions (CO₂Es) due to the excessive use of fossil fuels. In meeting future demand and supply predictions, much emphasis should be given [...] Read more.

Currently, Pakistan is in a stage of urbanization and industrialization, raising its energy demand and supply and carbon dioxide emissions (CO₂Es) due to the excessive use of fossil fuels. In meeting future demand and supply predictions, much emphasis should be given to both energy consumption and the level of inter-factor and inter-fuel substitution possibilities. Specifically, future outcomes for energy demand are more valid when production models contemplate substitution elasticity occurring during the period. To analyze the potential for little reliance on fossil fuels and diminish CO₂Es, the present research has examined the potential for the substitution of energy and non-energy factors (i.e., natural gas, electricity, petroleum, labor, and capital) by using translog productions function over the period between 1986–2019. The ridge regression method is applied to evade the multicollinearity issue in the data. The model analyzes the output elasticity, substitution elasticity, technical progress, and carbon emission scenarios. The results show that the output elasticities are growing, presenting that the contribution of all factors adds to economic growth. The inputs between capital-petroleum, capital-electricity, labor-electricity, capital-natural gas, and natural gas-electricity are extreme substitutes. These substitutes are increasing capital growth and production sizes. The relative difference in technical progress shows a small positive change between 3–7% with convergence evident. Lastly, the investment scenarios under 5% and 10% investment in petroleum reduction are evidence that the CO₂Es would reduce by 7.5 Mt and 10.43 Mt under scenario 1 and 7.0 Mt and 10.9 Mt under scenario 2. The results have broader suggestions for energy-conserving policies, particularly under the China–Pakistan Economic Corridor. Full article

(This article belongs to the Special Issue Climate Change, Energy Efficiency and Technological Innovation)

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12 pages, 2900 KiB

Open AccessArticle

Hyperparameter Tuning of OC-SVM for Industrial Gas Turbine Anomaly Detection

by Hyun-Su Kang, Yun-Seok Choi, Jun-Sang Yu, Sung-Wook Jin, Jung-Min Lee and Youn-Jea Kim

Energies 2022, 15(22), 8757; https://doi.org/10.3390/en15228757 - 21 Nov 2022

Cited by 8 | Viewed by 2058

Abstract

Gas turbine failure diagnosis is performed in this work based on seven types of tag data consisting of a total of 7976 data. The data consist of about 7000 normal data and less than 500 abnormal data. While normal data are easy to [...] Read more.

Gas turbine failure diagnosis is performed in this work based on seven types of tag data consisting of a total of 7976 data. The data consist of about 7000 normal data and less than 500 abnormal data. While normal data are easy to extract, failure data are difficult to extract. So, this study mainly is composed of normal data and a one-class support vector machine (OC-SVM) is used here, which has an advantage in classification accuracy performance. To advance the classification performance, four hyperparameter tuning (manual search, grid search, random search, Bayesian optimization) methods are applied. To analyze the performance of each technique, four evaluation indicators (accuracy, precision, recall, and F-1 score) are used. As a result, about 54.3% of the initial failure diagnosis performance is improved up to 64.88% through the advanced process in terms of accuracy. Full article

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20 pages, 14573 KiB

Open AccessArticle

Experimental Study on Flow Boiling Characteristics in Continuous and Segmented Microchannels with Vapor Venting Membrane

by Shanwei Li and Min Wei

Energies 2022, 15(22), 8756; https://doi.org/10.3390/en15228756 - 21 Nov 2022

Cited by 5 | Viewed by 1791

Abstract

Flow boiling in microchannels is one of the promising techniques for heat dissipation occurred in micro devices. However, the rapid bubble growth must be suppressed, which leads to serious boiling instabilities, high pressure drop, and low heat transfer coefficient. The addition of porous [...] Read more.

Flow boiling in microchannels is one of the promising techniques for heat dissipation occurred in micro devices. However, the rapid bubble growth must be suppressed, which leads to serious boiling instabilities, high pressure drop, and low heat transfer coefficient. The addition of porous hydrophobic membrane has proven an effective method to remove the vapor in-site in the literature. However, the effects of heat sink’s topological structures on the vapor venting are still a research gap. The present study experimentally investigates the influence of Polytetrafluoroethylene (PTFE) membrane on fluid flow pattern, pressure drop, vapor venting performance, and heat transfer characteristics of flow boiling in the continuous and segmented heat sinks. Results show that the vapor venting membrane can reduce the pressure drop and increase the heat transfer coefficient effectively by decreasing the exit vapor quality, especially in combination with the segmented structures. The interconnection area as a space for bubble growth and coalescence is beneficial for vapor venting due to increased vapor pressure and quantity. Following the enhanced vapor discharge, the fluctuation of pressure drop is further weakened, which is conducive for the safe operation of heat sink. Full article

(This article belongs to the Section J: Thermal Management)

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22 pages, 13286 KiB

Open AccessArticle

Application of Technology to Develop a Framework for Predicting Power Output of a PV System Based on a Spatial Interpolation Technique: A Case Study in South Korea

by Yeji Lee, Doosung Choi, Yongho Jung and Myeongjin Ko

Energies 2022, 15(22), 8755; https://doi.org/10.3390/en15228755 - 21 Nov 2022

Cited by 1 | Viewed by 1450

Abstract

To increase the accuracy of photovoltaic (PV) power prediction, meteorological data measured at a plant’s target location are widely used. If observation data are missing, public data such as automated synoptic observing systems (ASOS) and automatic weather stations (AWS) operated by the government [...] Read more.

To increase the accuracy of photovoltaic (PV) power prediction, meteorological data measured at a plant’s target location are widely used. If observation data are missing, public data such as automated synoptic observing systems (ASOS) and automatic weather stations (AWS) operated by the government can be effectively utilized. However, if the public weather station is located far from the target location, uncertainty in the prediction is expected to increase owing to the difference in distance. To solve this problem, we propose a power output prediction process based on inverse distance weighting interpolation (IDW), a spatial statistical technique that can estimate the values of unsampled locations. By demonstrating the proposed process, we tried to improve the prediction of photovoltaic power in random locations without data. The forecasting accuracy depends on the power generation forecasting model and proven case, but when forecasting is based on IDW, it is up to 1.4 times more accurate than when using ASOS data. Therefore, if measured data at the target location are not available, it was confirmed that it is more advantageous to use data predicted by IDW as substitute data than public data such as ASOS. Full article

(This article belongs to the Topic Solar and Wind Power and Energy Forecasting)

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30 pages, 5809 KiB

Open AccessArticle

Power System Stability Enhancement Using Robust FACTS-Based Stabilizer Designed by a Hybrid Optimization Algorithm

by Saeed Behzadpoor, Iraj Faraji Davoudkhani, Almoataz Youssef Abdelaziz, Zong Woo Geem and Junhee Hong

Energies 2022, 15(22), 8754; https://doi.org/10.3390/en15228754 - 21 Nov 2022

Cited by 17 | Viewed by 1808

Abstract

Improving the stability of power systems using FACT devices is an important and effective method. This paper uses a static synchronous series compensator (SSSC) installed in a power system to smooth out inter-area oscillations. A meta-heuristic optimization method is proposed to design the [...] Read more.

Improving the stability of power systems using FACT devices is an important and effective method. This paper uses a static synchronous series compensator (SSSC) installed in a power system to smooth out inter-area oscillations. A meta-heuristic optimization method is proposed to design the supplementary damping controller and its installation control channel within the SSSC. In this method, two control channels, phase and magnitude have been investigated for installing a damping controller to improve maximum stability and resistance in different operating conditions. An effective control channel has been selected. The objective function considered in this optimization method is multi-objective, using the sum of weighted coefficients method. The first function aims to minimize the control gain of the damping controller to the reduction of control cost, and the second objective function moves the critical modes to improve stability. It is defined as the minimum phase within the design constraints of the controller. A hybrid of two well-known meta-heuristic methods, the genetic algorithm (GA) and grey wolf optimizer (GWO) algorithm have been used to design this controller. The proposed method in this paper has been applied to develop a robust damping controller with an optimal control channel based on SSSC for two standard test systems of 4 and 50 IEEE machines. The results obtained from the analysis of eigenvalues and nonlinear simulation of the power system study show the improvement in the stability of the power system as well as the robust performance of the damping in the phase control channel. Full article

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11 pages, 5290 KiB

Open AccessArticle

Pressure Losses Downstream of a Compact Valve in the Inlet Chamber of an Intermediate-Pressure Steam Turbine

by Vaclav Slama, David Simurda and Richard Lenhard

Energies 2022, 15(22), 8753; https://doi.org/10.3390/en15228753 - 21 Nov 2022

Cited by 1 | Viewed by 1995

Abstract

Deep knowledge about pressure and energy losses in each part of a steam turbine is crucial for assuring the required efficiency and operational reliability. This paper presents the experimental as well as the numerical study of pressure losses in the inlet chamber of [...] Read more.

Deep knowledge about pressure and energy losses in each part of a steam turbine is crucial for assuring the required efficiency and operational reliability. This paper presents the experimental as well as the numerical study of pressure losses in the inlet chamber of an intermediate-pressure steam turbine. Measurements were carried out on a complex model, where not only was there an inlet turbine chamber, but also a compact valve assembly situated upstream and nozzles situated downstream. The compact valve as well as the turbine inlet chamber were relatively small. Therefore, greater pressure losses were expected. The aerodynamic laboratory of the Institute of Thermomechanics of the Czech Academy of Sciences was responsible for acquiring the measurements, which were carried out in a modular in-draft wind tunnel. In order to learn further details, numerical simulations were carried out. Doosan Skoda Power was responsible for this. A package of ANSYS software tools was used. Measured data were described and compared with numerical ones. Pressure losses were generalized in the form of the total pressure loss coefficient. As a result, pressure losses in similar turbine compact inlet chambers can be predicted with the required accuracy. Full article

(This article belongs to the Topic Latest Developments in Fluid Mechanics and Energy)

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19 pages, 8017 KiB

Open AccessArticle

Artificial Intelligence Model in Predicting Geomechanical Properties for Shale Formation: A Field Case in Permian Basin

by Fatick Nath, Sarker Monojit Asish, Deepak Ganta, Happy Rani Debi, Gabriel Aguirre and Edgardo Aguirre

Energies 2022, 15(22), 8752; https://doi.org/10.3390/en15228752 - 21 Nov 2022

Cited by 5 | Viewed by 2652

Abstract

Due to complexities in geologic structure, heterogeneity, and insufficient borehole information, shale formation faces challenges in accurately estimating the elastic properties of rock which triggers severe technical challenges in safe drilling and completion. These geomechanical properties could be computed from acoustic logs, however, [...] Read more.

Due to complexities in geologic structure, heterogeneity, and insufficient borehole information, shale formation faces challenges in accurately estimating the elastic properties of rock which triggers severe technical challenges in safe drilling and completion. These geomechanical properties could be computed from acoustic logs, however, accurate estimation is critical due to log deficit and a higher recovery expense of inadequate datasets. To fill the gap, this study focuses on predicting the sonic properties of rock using deep neural network (Bi-directional long short-time memory, Bi-LSTM) and random forest (RF) algorithms to estimate and evaluate the geomechanical properties of the potential unconventional formation, Permian Basin, situated in West Texas. A total of three wells were examined using both single-well and cross-well prediction algorithms. Log-derived single-well prediction models include a 75:25 ratio for training and testing the data whereas the cross-well includes two wells for training and the remaining well was used for testing. The selected well input logs include compressional wave slowness, resistivity, gamma-ray, porosity, and bulk density to predict shear wave slowness. The results using RF and Bi-LSTM show a promising prediction of geomechanical properties for Permian Basin wells. RF algorithm performed superior for both single and grouped well prediction. The single-well prediction method using the RF algorithm provided the highest accuracy of 99.90% whereas Bi-LSTM gave 93.60%. The best accuracy for a grouped well prediction was achieved employing Bi-LSTM and RF models, i.e., 96.01% and 93.80%. The average prediction including RF and Bi-LSTM algorithms demonstrated that accuracy for single well and cross well prediction is 96% and 94% respectively with an error below 7%. These outcomes show the astonishing capability of artificial intelligence (AI) models trained to create a realistic prediction to unlock unconventional potential when datasets are inadequate. Given adequate training data, operators could leverage these efficient tools by utilizing them to examine fracture interpretations with reduced cost and time when datasets are incomplete and thus increase the hydrocarbon recovery potential. Full article

(This article belongs to the Special Issue Application of Machine Learning in Rock Characterization)

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23 pages, 4303 KiB

Open AccessReview

A Comprehensive Review on Advances in TiO₂ Nanotube (TNT)-Based Photocatalytic CO₂ Reduction to Value-Added Products

by Md. Arif Hossen, H. M. Solayman, Kah Hon Leong, Lan Ching Sim, Nurashikin Yaacof, Azrina Abd Aziz, Wu Lihua and Minhaj Uddin Monir

Energies 2022, 15(22), 8751; https://doi.org/10.3390/en15228751 - 21 Nov 2022

Cited by 10 | Viewed by 2918

Abstract

The photocatalytic reduction of CO₂ into solar fuels by using semiconductor photocatalysts is one of the most promising approaches in terms of pollution control as well as renewable energy sources. One of the crucial challenges for the 21st century is the development [...] Read more.

The photocatalytic reduction of CO₂ into solar fuels by using semiconductor photocatalysts is one of the most promising approaches in terms of pollution control as well as renewable energy sources. One of the crucial challenges for the 21st century is the development of potential photocatalysts and techniques to improve CO₂ photoreduction efficiency. TiO₂ nanotubes (TNTs) have recently attracted a great deal of research attention for their potential to convert CO₂ into useful compounds. Researchers are concentrating more on CO₂ reduction due to the rising trend in CO₂ emissions and are striving to improve the rate of CO₂ photoreduction by modifying TNTs with the appropriate configuration. In order to portray the potential applications of TNTs, it is imperative to critically evaluate recent developments in synthesis and modification methodologies and their capability to transform CO₂ into value-added chemicals. The current review provides an insightful understanding of TNT production methods, surface modification strategies used to enhance CO₂ photoreduction, and major findings from previous research, thereby revealing research gaps and upcoming challenges. Stability, reusability, and the improved performance of TNT photocatalysts under visible light as well as the selection of optimized modification methods are the identified barriers for CO₂ photoreduction into valuable products. Higher rates of efficacy and product yield can be attained by synthesizing suitable photocatalysts with addressing the limitations of TNTs and designing an optimized photoreactor in terms of the proper utilization of photocatalysts, incident lights, and the partial pressure of reactants. Full article

(This article belongs to the Special Issue Advanced Nanomaterials for Photocatalytic Energy Conversion and Storage)

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26 pages, 5796 KiB

Open AccessArticle

Performance Evaluation of a Solar Heat-Driven Poly-Generation System for Residential Buildings Using Various Arrangements of Heat Recovery Units

by Saeed Alqaed, Ali Fouda, Hassan F. Elattar, Jawed Mustafa, Fahad Awjah Almehmadi, Hassanein A. Refaey and Mathkar A. Alharthi

Energies 2022, 15(22), 8750; https://doi.org/10.3390/en15228750 - 21 Nov 2022

Cited by 8 | Viewed by 1737

Abstract

Poly-generation systems are a feasible alternative to conventional energy production techniques in buildings. A poly-generation system allows for the concurrent production of electricity, heat, cold, and fresh water, with considerable advantages regarding technology, finances, energy recovery, and the environment. In the present study, [...] Read more.

Poly-generation systems are a feasible alternative to conventional energy production techniques in buildings. A poly-generation system allows for the concurrent production of electricity, heat, cold, and fresh water, with considerable advantages regarding technology, finances, energy recovery, and the environment. In the present study, the organic Rankine cycle (ORC), the humidification–dehumidification desalination system (HDH), and the desiccant cooling system (DCS) are merged with three unique solar-driven poly-generation systems (BS, IS-I, and IS-II) and numerically examined. The proposed options provide energy, space cooling, domestic heating, and potable water to buildings of small/medium scale. Using n-octane ORC working fluid, the impact of operational circumstances on system productivity and execution characteristics was considered. The findings show that (i) the suggested poly-generation systems can provide electrical power, conditioned space cooling, local heating, and fresh water, whereas keeping the conditioned area pleasant, (ii) the IS-I system achieves the best system performance among all compared arrangements (BS and IS-II); (iii) the attained extreme values of

{\dot{W}}_{n e t}

,

{\dot{m}}_{f r e s h}

,

{\dot{Q}}_{c o o l i n g}

,

{\dot{Q}}_{h e a t i n g}

, and TGOR are 102.0 kW (all systems), 214.70 kg/h (IS-II), 29.940 kW (IS-II), 225.6 kW (IS-I), and 0.6303 (IS-I), respectively. Full article

(This article belongs to the Special Issue Heat Transfer and Fluid Flow in Heat Exchangers and Sustainable Energy Systems)

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19 pages, 7422 KiB

Open AccessArticle

Analysis of the Influence of the Gas Infrared Heater and Equipment Element Relative Positions on Industrial Premises Thermal Conditions

by Boris Vladimirovich Borisov, Alexander Vitalievich Vyatkin, Geniy Vladimirovich Kuznetsov, Vyacheslav Ivanovich Maksimov and Tatiana Aleksandrovna Nagornova

Energies 2022, 15(22), 8749; https://doi.org/10.3390/en15228749 - 21 Nov 2022

Cited by 2 | Viewed by 1790

Abstract

The creation of local heated areas in large-sized premises using systems based on gas infrared heaters has recently become the most rational alternative in terms of energy efficiency. However, the lack of information about the thermal characteristics in such areas limits the effective [...] Read more.

The creation of local heated areas in large-sized premises using systems based on gas infrared heaters has recently become the most rational alternative in terms of energy efficiency. However, the lack of information about the thermal characteristics in such areas limits the effective application of these systems. To determine the main thermal parameters characterizing the scheduled thermal conditions in heated local working areas of industrial premises, experimental and mathematical modeling of heat transfer processes in a closed area with the presence of equipment in it was carried out. The experimental area was equipped with a gas infrared heater and a model of the equipment (a horizontally oriented panel). The system of equations of thermal conductivity, radiant heat transfer, as well as energy and Navier–Stokes was solved by the finite element method. A significant influence of the equipment position on the temperature field and the air movement hydrodynamics in the local working area has been established. The equipment presence in the room intensifies the air movement due to thermal convection and, as a result, a more uniform temperature distribution over the local working area was obtained. Analysis of the obtained results shows the possibility to control the temperature fields’ formation in local working areas during the gas infrared heater operation by varying the position and configuration of the equipment in the room. Full article

(This article belongs to the Topic Built Environment and Human Comfort)

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19 pages, 15032 KiB

Open AccessArticle

Multipoint Design Optimization of a Radial-Outflow Turbine for Kalina Cycle System Considering Flexible Operating Conditions and Variable Ammonia-Water Mass Fraction

by Peng Song, Jinju Sun, Shengyuan Wang and Xuesong Wang

Energies 2022, 15(22), 8748; https://doi.org/10.3390/en15228748 - 21 Nov 2022

Cited by 3 | Viewed by 1716

Abstract

The radial-outflow turbine has advantages due to its liquid-rich gas adaptability when applied in the Kalina ammonia-water cycle system. However, the operational conditions of the turbine often deviate from its design values due to changes of the heat source or the cooling conditions, [...] Read more.

The radial-outflow turbine has advantages due to its liquid-rich gas adaptability when applied in the Kalina ammonia-water cycle system. However, the operational conditions of the turbine often deviate from its design values due to changes of the heat source or the cooling conditions, and such deviates may deteriorate the flow behavior and degrade the turbine performance. To enhance the turbine efficiency at complex conditions for flexible running of the Kalina cycle system, a multipoint design optimization method is developed: the flexible operating has been defined by three critical, dimensionless parameters, which cover a wide range in a 3D operating space; the representative off-design points are identified to define the objective function; and adaptive optimization methods are integrated to permit optimization searching using limited CFD callings. The developed multipoint design method is adopted to improve the turbine performance under complex operating conditions. The obtained results demonstrate that the application of the developed multipoint optimization method effectively eliminates the flow separation at various operating conditions; thus, the turbine off-design performance has been comprehensively improved. Full article

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31 pages, 1627 KiB

Open AccessReview

Power Generation Scheduling for a Hydro-Wind-Solar Hybrid System: A Systematic Survey and Prospect

by Chaoyang Chen, Hualing Liu, Yong Xiao, Fagen Zhu, Li Ding and Fuwen Yang

Energies 2022, 15(22), 8747; https://doi.org/10.3390/en15228747 - 21 Nov 2022

Cited by 8 | Viewed by 4691

Abstract

In the past two decades, clean energy such as hydro, wind, and solar power has achieved significant development under the “green recovery” global goal, and it may become the key method for countries to realize a low-carbon energy system. Here, the development of [...] Read more.

In the past two decades, clean energy such as hydro, wind, and solar power has achieved significant development under the “green recovery” global goal, and it may become the key method for countries to realize a low-carbon energy system. Here, the development of renewable energy power generation, the typical hydro-wind-photovoltaic complementary practical project, is summarized, and some key problems in complementary systems such as the description and prediction of the power generation law in large-scale stations, risk management, and coordinated operation are analyzed. In terms of these problems, this paper systematically summarizes the research methods and characteristics of a hydro-wind-solar hybrid system and expounds upon the technical realization process from the prediction and description of wind and solar power station cluster output, the risks brought about by large-scale renewable energy grid-connected operation, and the long-term and short-term coordination modeling and resolution thoughts on the hydro-wind-solar hybrid system in cluster mode. Finally, based on the aforementioned analysis, the existing research gaps are discussed from the standpoints of generation forecast, risk management, and cluster scheduling, and the future work outlook is presented accordingly. A hybrid system that combines hydro, wind, and solar energy is emerging as a way to make up for each other’s shortcomings and will be a fruitful area of study in the future. Full article

(This article belongs to the Section A1: Smart Grids and Microgrids)

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