Exergy Analysis and Its Applications

Journal Name	Impact Factor	CiteScore	Launched Year	First Decision (median)	APC
Applied Sciences applsci	2.5	5.3	2011	18.4 Days	CHF 2400
Energies energies	3.0	6.2	2008	16.8 Days	CHF 2600
Thermo thermo	-	2.1	2021	22.8 Days	CHF 1000
Sustainability sustainability	3.3	6.8	2009	19.7 Days	CHF 2400

22 pages, 1398 KiB

Open AccessArticle

A Comprehensive Societal Energy Return on Investment Study of Portugal Reveals a Low but Stable Value

by Marco Vittorio Ecclesia, João Santos, Paul E. Brockway and Tiago Domingos

Energies 2022, 15(10), 3549; https://doi.org/10.3390/en15103549 - 12 May 2022

Cited by 3 | Viewed by 3636

Energy return on investment (EROI) is a ratio of the energy obtained in relation to the energy used to extract/produce it. The EROI of fossil fuels is globally decreasing. What do the declining EROIs of energy sources imply for society as a whole? [...] Read more.

Energy return on investment (EROI) is a ratio of the energy obtained in relation to the energy used to extract/produce it. The EROI of fossil fuels is globally decreasing. What do the declining EROIs of energy sources imply for society as a whole? We answer this question by proposing a novel EROI measure that describes, through one parameter, the efficiency of a society in managing energy resources over time. Our comprehensive societal EROI measure was developed by (1) expanding the boundaries of the analysis up to the useful stage; (2) estimating the amount of energy embodied in the energy-converting capital; (3) considering non-conventional sources such as the muscle work of humans and draught animals; and (4) considering the influence of imported and exported energy. We computed the new EROI for Portugal as a case study. We find a considerably lower EROI value, at around 3, compared to those currently available, which is stable over a long-time range (1960–2014). This suggests an independence of EROI from economic growth. When estimated at the final stage, using conventional methods (i.e., without applying the four novelties here introduced), we find a declining societal EROI. Therefore, our results imply that the production of new and more efficient final-to-useful energy converting capital has historically kept societal EROI around a stable value by offsetting the effects of the changing returns of energy sources at the primary and final stages. This will be crucial in the successful transition to renewables. Full article

(This article belongs to the Topic Exergy Analysis and Its Applications)

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13 pages, 2923 KiB

Open AccessArticle

Exergy Analysis of the Prevailing Residential Heating System and Derivation of Future CO₂-Reduction Potential

by Julian Schwab, Markus Bernecker, Saskia Fischer, Bijan Seyed Sadjjadi, Martin Kober, Frank Rinderknecht and Tjark Siefkes

Energies 2022, 15(10), 3502; https://doi.org/10.3390/en15103502 - 10 May 2022

Cited by 2 | Viewed by 2344

Abstract

The residential heating sector accounts for a large share of the worldwide annual primary energy consumption. In order to reduce CO₂-emissions, it is therefore particularly important to analyse this sector for potential efficiency improvements. In Europe, natural gas boilers are the [...] Read more.

The residential heating sector accounts for a large share of the worldwide annual primary energy consumption. In order to reduce CO₂-emissions, it is therefore particularly important to analyse this sector for potential efficiency improvements. In Europe, natural gas boilers are the most widely used heating technology since they are cost-effective and can be installed in any type of building. The energy efficiency of these boilers is already high. However, in their internal process, heat is generated at a high temperature level which is only used for space heating and therefore a high amount of exergy remains unused. This research aims to develop the potential of using the exergy to further improve the efficiency of the systems. A novel combination of methods is applied to analyse the thermodynamic behaviour of gas-fired boilers in detail and over the cycle of a year. The analysis is performed in two steps: In the first step a system is examined in stationary operating points. This is carried out through an experimental setup and a three-dimensional numerical simulation. In the second step, the obtained data is applied to a transient annual building simulation. The results show the temporal distribution and total amount of the annual exergy loss for a common residential building. The exergy loss accumulates to 16,271 kWh per year, which shows the high potential to partially convert the exergy to electrical energy and significantly reduce the external electricity demand and CO₂-emissions of the building. Based on this, new technologies such as Thermoelectric Generators can be developed, which can enable this potential. Full article

(This article belongs to the Topic Exergy Analysis and Its Applications)

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24 pages, 1637 KiB

Open AccessArticle

Thermodynamic, Exergetic and Thermoeconomic Analyses of Double-Effect LiBr–Water Absorption Refrigeration Systems with a 5 kW High Temperature PEMFC as Heat Source for Data Center Applications

by Seok-Ho Seo, Si-Doek Oh and Ho-Young Kwak

Energies 2022, 15(9), 3101; https://doi.org/10.3390/en15093101 - 24 Apr 2022

Cited by 5 | Viewed by 1658

Abstract

Thermodynamic, exergetic and thermoeconomic analyses were performed on two types of double-effect LiBr–water absorption refrigeration systems (ARS) for use with a 5-kW high-temperature proton exchange membrane fuel cell (HT-PEMFC) as a heat source. Proper temperatures of the high-pressure generator, combined generator and condenser, [...] Read more.

Thermodynamic, exergetic and thermoeconomic analyses were performed on two types of double-effect LiBr–water absorption refrigeration systems (ARS) for use with a 5-kW high-temperature proton exchange membrane fuel cell (HT-PEMFC) as a heat source. Proper temperatures of the high-pressure generator, combined generator and condenser, condenser, absorber and evaporator were determined to meet the requirements of constant cooling demands for data center operations. The heat balance of the combined unit of generator and condenser in the industrial double-effect LiBr-water ARS is important for determining the flow rate of the primary vapor refrigerant from the high-pressure generator. The industrial double-effect ARS system, whose analysis has not been studied analytically, outperformed the series double-effect system and provided 6.5 kW of cooling capacity with a coefficient of performance of 0.99. The unit cost of chilled water estimated by the modified productive structure analysis (MOPSA) method is approximately 7.18 USD/GJ (=0.026 US$/kWh). Effective exergetic efficiency of HT-PEMFC with the industrial ARS increases to 57.6% from 47.0%. Full article

(This article belongs to the Topic Exergy Analysis and Its Applications)

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21 pages, 19339 KiB

Open AccessArticle

Performance Improvement of a Novel Trapezoid Air-Cooling Battery Thermal Management System for Electric Vehicles

by Gang Zhao, Xiaolin Wang, Michael Negnevitsky, Hengyun Zhang and Chengjiang Li

Sustainability 2022, 14(9), 4975; https://doi.org/10.3390/su14094975 - 21 Apr 2022

Cited by 16 | Viewed by 3648

Abstract

An air-cooling battery thermal management system is a reliable and cost-effective system to control the operating temperatures of the electric vehicle battery pack within an ideal range. Different from most designs of the rectangular battery pack in previous research, this one proposed a [...] Read more.

An air-cooling battery thermal management system is a reliable and cost-effective system to control the operating temperatures of the electric vehicle battery pack within an ideal range. Different from most designs of the rectangular battery pack in previous research, this one proposed a novel isosceles trapezoid layout to improve system heat dissipations. The simulation results showed that the trapezoid design delivered better cooling performances than the rectangular one with a maximum temperature reduction of 0.9 °C and maximum temperature difference reduction of 1.17 °C at the inlet air flow rate of 60 L/s. Moreover, the cooling performance was further boosted by an aluminum heat spreader. The boosted design delivers an average Max T (32.95 °C) and an average ΔT (3.10 °C) at five different flow rates, which are 8.8% and 66.1% lower the one without the spreader (35.85 °C and 5.15 °C). Compared with the rectangular design without the spreader, the average Max T and ΔT of the boosted trapezoid design are reduced by 10.4% and 91.9% in addition to a space-saving of about 5.26%. Full article

(This article belongs to the Topic Exergy Analysis and Its Applications)

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12 pages, 2336 KiB

Open AccessArticle

BiLSTM Network-Based Approach for Solar Irradiance Forecasting in Continental Climate Zones

by Mohammed A. Bou-Rabee, Muhammad Yasin Naz, Imad ED. Albalaa and Shaharin Anwar Sulaiman

Energies 2022, 15(6), 2226; https://doi.org/10.3390/en15062226 - 18 Mar 2022

Cited by 22 | Viewed by 2528

Abstract

Recent research on solar irradiance forecasting has attracted considerable attention, as governments worldwide are displaying a keenness to harness green energy. The goal of this study is to build forecasting methods using deep learning (DL) approach to estimate daily solar irradiance in three [...] Read more.

Recent research on solar irradiance forecasting has attracted considerable attention, as governments worldwide are displaying a keenness to harness green energy. The goal of this study is to build forecasting methods using deep learning (DL) approach to estimate daily solar irradiance in three sites in Kuwait over 12 years (2008–2020). Solar irradiance data are used to extract and understand the symmetrical hidden data pattern and correlations, which are then used to predict future solar irradiance. A DL model based on the attention mechanism applied to bidirectional long short-term memory (BiLSTM) is developed for accurate solar irradiation forecasting. The proposed model is designed for two different conditions (sunny and cloudy days) to ensure greater accuracy in different weather scenarios. Simulation results are presented which depict that the attention based BiLSTM model outperforms the other deep learning networks in the prediction analysis of solar irradiance. The attention based BiLSTM model was able to predict variations in solar irradiance over short intervals in continental climate zones (Kuwait) more efficiently with an RMSE of 4.24 and 20.95 for sunny and cloudy days, respectively. Full article

(This article belongs to the Topic Exergy Analysis and Its Applications)

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31 pages, 7615 KiB

Open AccessArticle

Real-Time Grid Signal-Based Energy Flexibility of Heating Generation: A Methodology for Optimal Scheduling of Stratified Storage Tanks

by Matthias Eydner, Lu Wan, Tobias Henzler and Konstantinos Stergiaropoulos

Energies 2022, 15(5), 1793; https://doi.org/10.3390/en15051793 - 28 Feb 2022

Cited by 3 | Viewed by 1958

Abstract

Heat pumps coupled with thermal energy storage (TES) systems are seen as a promising technology for load management that can be used to shift peak loads to off-peak hours. Most of the existing model predictive control (MPC) studies on tariff-based load shifting deploying [...] Read more.

Heat pumps coupled with thermal energy storage (TES) systems are seen as a promising technology for load management that can be used to shift peak loads to off-peak hours. Most of the existing model predictive control (MPC) studies on tariff-based load shifting deploying hot water tanks use simplified tank models. In this study, an MPC framework that accounts for transient thermal behavior (i.e., mixing and stratification) by applying energy (EMPC) and exergy (XMPC) analysis is proposed. A case study for an office building equipped with an air handling unit (AHU) revealed that the MPC strategy had a high load-shifting capacity: over 80% of the energy consumption took place during off-peak hours when there was an electricity surplus in the grid. An analysis of a typical day showed that the XMPC method was able to provide more appropriate stratification within the TES for all load characteristics. An annual exergy analysis demonstrated that, during cold months, energy degradation in the TES is mainly caused by exergy destruction due to irreversibility, while, during the transition to milder months, exergy loss dominates. Compared to the EMPC approach, the XMPC strategy achieves additional reductions of 18% in annual electricity consumption, 13% in operating costs, and almost 17% in emissions. Full article

(This article belongs to the Topic Exergy Analysis and Its Applications)

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19 pages, 40535 KiB

Open AccessArticle

Life Cycle and Exergoenvironmental Analyses of Ethanol: Performance of a Flex-Fuel Spark-Ignition Engine at Wide-Open Throttle Conditions

by Eduardo J. C. Cavalcanti, Daniel R. S. da Silva and Monica Carvalho

Energies 2022, 15(4), 1422; https://doi.org/10.3390/en15041422 - 15 Feb 2022

Cited by 6 | Viewed by 2537

Abstract

The growth in the number of vehicles circulating has led to a proportional increase in polluting gas emissions. Bioenergy can be used to help meet these increasing energy demands and mitigate environmental impacts. This work verified the effect of the content of ethanol [...] Read more.

The growth in the number of vehicles circulating has led to a proportional increase in polluting gas emissions. Bioenergy can be used to help meet these increasing energy demands and mitigate environmental impacts. This work verified the effect of the content of ethanol on the exergy and exergoenvironmental analyses of a spark-ignition engine. Different gasoline–ethanol mixtures were tested along with hydrous ethanol (4.6% water by volume). The thermodynamic data refer to wide-open throttle conditions and variable engine speeds. The life cycle assessment methodology quantified the environmental impacts associated with equipment and fuel using the Eco-indicator 99 method. Pollutants emitted during combustion were measured and included in the environmental assessment (nitrogen oxides, carbon monoxide, and dioxide). Hydrous ethanol at 1500 rpm presented the highest energy efficiency. The effects of the environmental impact rate of pollutant formation and exergy efficiency were significantly higher than the environmental impact rate of fuel. The lowest specific environmental impact of the product (brake power) was 24.39 mPt/MJ, obtained with the fuel blend with 50% ethanol at 2500 rpm. The combined evaluation of the exergoenvironmental factor and the relative difference in environmental impact indicated the optimization priorities and where improvements should be directed. Full article

(This article belongs to the Topic Exergy Analysis and Its Applications)

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20 pages, 37219 KiB

Open AccessArticle

Experimental Analysis of the R744/R404A Cascade Refrigeration System with Internal Heat Exchanger. Part 2: Exergy Characteristics

by Min-Ju Jeon

Energies 2022, 15(3), 1251; https://doi.org/10.3390/en15031251 - 8 Feb 2022

Cited by 8 | Viewed by 3178

Abstract

This paper examines the exergy efficiency and exergy destruction rate of the R744/R404A cascade refrigeration system (CRS) using an internal heat exchanger in supermarkets according to various conditions affecting the system. A refrigerant of a low-temperature cycle uses R744 and a refrigerant of [...] Read more.

This paper examines the exergy efficiency and exergy destruction rate of the R744/R404A cascade refrigeration system (CRS) using an internal heat exchanger in supermarkets according to various conditions affecting the system. A refrigerant of a low-temperature cycle uses R744 and a refrigerant of a high-temperature cycle in the CRS uses R404A. Experiments were conducted by changing various conditions on the high- and low-temperature side, and exergy analysis was performed accordingly. The main results are summarized as follows: (1) the lower the total exergy destruction rate of the CRS, the higher the exergy efficiency of the system, and accordingly the coefficient of performance (COP) of the system is also improved. (2) In the CRS, since the optimum cascade evaporation temperature exists (about −16 °C), it can be said that the limit point, that is, the cascade evaporation temperature with the maximum COP of the system, is the optimum point at about −16 °C. Therefore, at this optimum point, the exergy destruction rate of the cascade heat exchanger becomes the minimum. In other words, it should be noted that when the cascade evaporation temperature is the optimum point, the exergy destruction rate of the R744 compressor and the cascade heat exchanger is minimal. The purpose of this study is to provide basic design data by analyzing the exergy characteristics according to various conditions on the high- and low-temperature side for optimal design of a CRS to which R744 is applied. Full article

(This article belongs to the Topic Exergy Analysis and Its Applications)

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19 pages, 5099 KiB

Open AccessArticle

Exergy-Based Thermo-Hydraulic Performance of Roughened Absorber in Solar Air Heater Duct

by Tabish Alam, Md Irfanul Haque Siddiqui, Hassan Alshehri, Masood Ashraf Ali, Paolo Blecich and Kushagra Saurabh

Appl. Sci. 2022, 12(3), 1696; https://doi.org/10.3390/app12031696 - 7 Feb 2022

Cited by 7 | Viewed by 2387

Abstract

This paper presents the thermo-hydraulic performance of small conical ribs on the absorber plate of a solar energy air heater (SAH) using exergy analysis. Application of conical protrusion ribs on the absorber is an attractive solution for enhancing the thermal performance of a [...] Read more.

This paper presents the thermo-hydraulic performance of small conical ribs on the absorber plate of a solar energy air heater (SAH) using exergy analysis. Application of conical protrusion ribs on the absorber is an attractive solution for enhancing the thermal performance of a SAH. However, these ribs are also responsible for high friction losses and increased fan power consumption caused by the turbulent air flow. To optimize the rib design, it is vital to consider both thermal and hydraulic performance at the same time. The SAH was assessed using an analytic method which predicts the exergy efficiency under operating parameters (e.g., Reynolds number, solar insolation and temperature increase parameter). The following geometric quantities of ribs were evaluated for optimum exergy efficiency: the relative rib height (e/D), which was in the range between 0.200 and 0.044, and the relative rib pitch (p/e), which was in the range between 6 and 12. The combination of a relative rib height of 0.044 and relative rib pitch of 10 exhibits the highest exergy efficiency of 0.0202. The optimization of the rib geometric quantities parameters was performed by considering the temperature increase parameter, aiming to achieve maximum exergy efficiency. The combination of rib parameters e/D = 0.044 and p/e = 10 are noted to yield best performance when operating at a temperature increase parameter above 0.0141 K∙m²/W. Full article

(This article belongs to the Topic Exergy Analysis and Its Applications)

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35 pages, 9375 KiB

Open AccessArticle

Forecasting Building Energy Consumption Using Ensemble Empirical Mode Decomposition, Wavelet Transformation, and Long Short-Term Memory Algorithms

by Shuo-Yan Chou, Anindhita Dewabharata, Ferani E. Zulvia and Mochamad Fadil

Energies 2022, 15(3), 1035; https://doi.org/10.3390/en15031035 - 29 Jan 2022

Cited by 21 | Viewed by 3460

Abstract

A building, a central location of human activities, is equipped with many devices that consume a lot of electricity. Therefore, predicting the energy consumption of a building is essential because it helps the building management to make better energy management policies. Thus, predicting [...] Read more.

A building, a central location of human activities, is equipped with many devices that consume a lot of electricity. Therefore, predicting the energy consumption of a building is essential because it helps the building management to make better energy management policies. Thus, predicting energy consumption of a building is very important, and this study proposes a forecasting framework for energy consumption of a building. The proposed framework combines a decomposition method with a forecasting algorithm. This study applies two decomposition algorithms, namely the empirical mode decomposition and wavelet transformation. Furthermore, it applies the long short term memory algorithm to predict energy consumption. This study applies the proposed framework to predict the energy consumption of 20 buildings. The buildings are located in different time zones and have different functionalities. The experiment results reveal that the best forecasting algorithm applies the long short term memory algorithm with the empirical mode decomposition. In addition to the proposed framework, this research also provides the recommendation of the forecasting model for each building. The result of this study could enrich the study about the building energy forecasting approach. The proposed framework also can be applied to the real case of electricity consumption. Full article

(This article belongs to the Topic Exergy Analysis and Its Applications)

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11 pages, 2307 KiB

Open AccessArticle

Ionic Mass Transfer at Point Electrodes Located at Cathode Support Plate in an Electrorefining Cell in Presence of Rectangular Turbulent Promoters

by Tondepu Subbaiah, Ponnam Vijetha, Barsha Marandi, Kali Sanjay and Manickam Minakshi

Sustainability 2022, 14(2), 880; https://doi.org/10.3390/su14020880 - 13 Jan 2022

Cited by 5 | Viewed by 1953

Abstract

Current density plays a major role in deciding the plant size, current efficiency, and energy consumption in electrorefining cells. In general, operating current density will be 40% of the limiting current density. Forced circulation of the electrolyte in the presence of promoters improves [...] Read more.

Current density plays a major role in deciding the plant size, current efficiency, and energy consumption in electrorefining cells. In general, operating current density will be 40% of the limiting current density. Forced circulation of the electrolyte in the presence of promoters improves the mass transfer coefficient. In the present study, rectangular turbulence promoters are fitted at the bottom side of the cell to improve the mass transfer coefficient at the cathode support plate. The limiting current density technique is used to measure the mass transfer coefficient. The variables covered in the present study are the effects of flow rate, promoter height, and spacing among the promoters. The electrolyte consists of copper sulfate and sulphuric acid. At a regulated flow rate, the electrolyte is pumped from the recirculation tank to the cell through an intermediate overhead tank. The limiting current density increased with an increasing flow rate in the presence of promoters, and thus the overall mass transfer coefficient on the cathode support plate also improved. With an increase in the flow rate of the electrolyte from 6.67 × 10⁻⁶ to 153.33 m³/s, limiting current density increased from 356.8 to 488.8 A/m² for spacing of 0.30 m, with a promoter height of 0.01 m. However, it is noteworthy that when the promoter height is increased from 0.01 to 0.07 m, the overall mass transfer coefficient is found to increase up to 60%, but with the further increase in the promoter height to 0.30 m the mass transfer coefficient starts to decrease. Therefore, the optimized cell parameters are established in this work. The current sustainable concept of employing rectangular turbulence promoters will bring benefits to any precious metal refining or electrowinning tank house electrolytes. Full article

(This article belongs to the Topic Exergy Analysis and Its Applications)

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19 pages, 1824 KiB

Open AccessArticle

Exergy Analysis of Alternative Configurations of Biomass-Based Light Olefin Production System with a Combined-Cycle Scheme via Methanol Intermediate

by Yuping Li, Maolin Ye, Fenghua Tan, Chenguang Wang and Jinxing Long

Energies 2022, 15(2), 404; https://doi.org/10.3390/en15020404 - 6 Jan 2022

Cited by 6 | Viewed by 2648

Abstract

Thermodynamic performance of three conceptual systems for biomass-derived olefin production with electricity cogeneration was studied and compared via exergy analysis at the levels of system, subsystem and operation unit. The base case was composed of the subsystems of gasification, raw fuel gas adjustment, [...] Read more.

Thermodynamic performance of three conceptual systems for biomass-derived olefin production with electricity cogeneration was studied and compared via exergy analysis at the levels of system, subsystem and operation unit. The base case was composed of the subsystems of gasification, raw fuel gas adjustment, methanol/light olefin synthesis and steam & power generation, etc. The power case and fuel case were designed as the combustion of a fraction of gasification gas to increase power generation and the recycle of a fraction of synthesis tail gas to increase olefin production, respectively. It was found that the subsystems of gasification and steam & power generation contribute ca. 80% of overall exergy destruction for each case, of which gasifier and combustor are the main exergy destruction sources, due to the corresponding chemical exergy degrading of biomass and fuel gas. The low efficiency of 33.1% for the power case could be attributed to the significant irreversibility of the combustor, economizer, and condenser in the combined-cycle subsystem. The effect of the tail gas recycle ratio, moisture content of feedstock, and biomass type was also investigated to enhance system exergy performance, which could be achieved by high recycle ratio, using dry biomass and the feedstock with high carbon content. High system efficiency of 38.9% was obtained when oil palm shell was used, which was 31.7% for rice husk due to its low carbon content. Full article

(This article belongs to the Topic Exergy Analysis and Its Applications)

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15 pages, 1301 KiB

Open AccessArticle

Assessment of Cumulative Energy Needs for Chosen Technologies of Cattle Feeding in Barns with Conventional (CFS) and Automated Feeding Systems (AFS)

by Witold Jan Wardal, Kamila Ewelina Mazur, Kamil Roman, Michał Roman and Marcin Majchrzak

Energies 2021, 14(24), 8584; https://doi.org/10.3390/en14248584 - 20 Dec 2021

Cited by 8 | Viewed by 2426

Abstract

The increasing popularity of automated systems and the increased market share of producers of robotic feeding equipment for cows causes the need for a deeper study of energy demand in such technologies. This article provides an analysis of the inputs of energy accumulated [...] Read more.

The increasing popularity of automated systems and the increased market share of producers of robotic feeding equipment for cows causes the need for a deeper study of energy demand in such technologies. This article provides an analysis of the inputs of energy accumulated in conventional (CFS) and automated feeding systems (AFS) for cattle. The aim of this is to determine the impact of robotic technologies for the preparation and feeding of fodder on the cumulative energy inputs. The aim of this paper is to investigate the effect of machinery and the equipment applied to the cumulative energy intensity in cattle farming facilities. The cumulative energy consumption for four technologies of automated cattle feeding (AFS) was tested and compared to the energy consumption for six technologies with a conventional feeding system (CFS). The research involved nine cow barn facilities for dairy cows and one for beef cattle. An evaluation has been made for cattle farming structures (milk and meat production) with various mixing and feeding systems for feeds of various concentrations, and keeping system (tied system and free-stall). The cow barns differed in feed mixing, feeding machinery, and equipment. Measurements of live labor inputs and the consumption of electric and mechanical energy carriers were carried out, and the mass of various types of machines and devices with software was taken into account, which became the basis for calculating cumulative energy consumption for individual technologies. The obtained average of electric and mechanical energy inputs for robotic technologies of feeding fodder (AFS) was 0.60025 kWh∙day⁻¹∙LU⁻¹(where LU means Large Animal Unit 500 kg), and it was 39.3% lower than for conventional technologies (CFS) where it was 0.989052 kWh∙day⁻¹∙LU⁻¹. However, taking into account all components of cumulative energy consumption, the average for the group of robotic technologies (AFS) was higher by 35.18% than for conventional technologies (CFS). Full article

(This article belongs to the Topic Exergy Analysis and Its Applications)

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22 pages, 7530 KiB

Open AccessArticle

A Novel Generator Design Utilised for Conventional Ejector Refrigeration Systems

by Anas F. A. Elbarghthi, Mohammad Yousef Hdaib and Václav Dvořák

Energies 2021, 14(22), 7705; https://doi.org/10.3390/en14227705 - 17 Nov 2021

Cited by 1 | Viewed by 2464

Abstract

Ejector refrigeration systems are rapidly evolving and are poised to become one of the most preferred cooling systems in the near future. CO₂ transcritical refrigeration systems have inherently high working pressures and discharge temperatures, providing a large volumetric heating capacity. In the [...] Read more.

Ejector refrigeration systems are rapidly evolving and are poised to become one of the most preferred cooling systems in the near future. CO₂ transcritical refrigeration systems have inherently high working pressures and discharge temperatures, providing a large volumetric heating capacity. In the current research, the heat ejected from the CO₂ gas cooler was proposed as a driving heating source for the compression ejector system, representing the energy supply for the generator in a combined cycle. The local design approach was investigated for the combined plate-type heat exchanger (PHE) via Matlab code integrated with the NIST real gas database. HFO refrigerants (1234ze(E) and 1234yf) were selected to serve as the cold fluid on the generator flowing through three different phases: subcooled liquid, a two-phase mixture, and superheated vapour. The study examines the following: the effectiveness, the heat transfer coefficients, and the pressure drop of the PHE working fluids under variable hot stream pressures, cold stream flow fluxes, and superheated temperatures. The integration revealed that the cold fluid mixture phase dominates the heat transfer coefficients and the pressure drop of the heat exchanger. By increasing the hot stream inlet pressure from 9 MPa to 12 MPa, the cold stream two-phase convection coefficient can be enhanced by 50% and 200% for R1234yf and R1234ze(E), respectively. Conversely, the cold stream two-phase convection coefficient dropped by 17% and 37% for R1234yf and R1234ze(E), respectively. The overall result supports utilising the ejected heat from the CO₂ transcritical system, especially at high CO₂ inlet pressures and low cold channel flow fluxes. Moreover, R1234ze(E) could be a more suitable working fluid because it possesses a lower pressure drop and bond number. Full article

(This article belongs to the Topic Exergy Analysis and Its Applications)

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17 pages, 3146 KiB

Open AccessArticle

RDF Fire and Explosion Hazards at Power Plants

by Janusz Januszewski and Dorota Brzezińska

Sustainability 2021, 13(22), 12718; https://doi.org/10.3390/su132212718 - 17 Nov 2021

Cited by 3 | Viewed by 3954

Abstract

In the last 30 years Refuse Derived Fuel (RDF) has grown in popularity due to its perception as a readily available, renewable and sustainable fuel for power stations. This increased use of RDF has been closely followed by an escalation of industrial fire [...] Read more.

In the last 30 years Refuse Derived Fuel (RDF) has grown in popularity due to its perception as a readily available, renewable and sustainable fuel for power stations. This increased use of RDF has been closely followed by an escalation of industrial fire and explosion-related incidents associated with this fuel, showing the new hazards and inherent dangers brought by it. The re-evaluation of specific fire and explosion protective measures is required. For RDF to have a continued role as an energy source in a volatile and difficult energy market, it must be perceived as: sustainable; safe; easy; cheap; and reliable. If financial losses due to business interruption occur frequently, then confidence in this area will dissolve, and while safety is paramount to prevent injury and/or death, reputational damage must also be considered to secure energy supply and maintain market confidence in RDF. This paper presents a review of previous investigations and scientific studies, which, combined with the authors’ own RDF fire and explosion investigatory experience, allows for a logical hypothesis to be made in relation to relative practices in storage and fuel route fire safety management. Full article

(This article belongs to the Topic Exergy Analysis and Its Applications)

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26 pages, 1816 KiB

Open AccessReview

Analysis of Natural Gas Consumption Interdependence for Polish Industrial Consumers on the Basis of an Econometric Model

by Tomasz Chrulski and Mariusz Łaciak

Energies 2021, 14(22), 7649; https://doi.org/10.3390/en14227649 - 16 Nov 2021

Cited by 2 | Viewed by 2440

Abstract

The transmission of natural gas is a key element of the Polish energy system. The published data of the Polish distribution system operators and the transmission system operator on the volume of gaseous fuel transmitted indicate a growing trend in the consumption of [...] Read more.

The transmission of natural gas is a key element of the Polish energy system. The published data of the Polish distribution system operators and the transmission system operator on the volume of gaseous fuel transmitted indicate a growing trend in the consumption of energy produced from natural gas. In connection with the energy transformation, switching energy generation sources from hard coal to natural gas in Poland, it is important for transmission operators to know the future demand for gaseous fuel. The aim of the article is to attempt to develop an econometric model related to the consumption of gaseous fuel by Polish entrepreneurs. The knowledge therein may be useful for making business decisions related to the possible expansion of the transmission system, and thus investing financial resources for this purpose. This knowledge will also provide quantitative information related to the interest in gaseous fuel among industrial consumers and the analysis of the trend of natural gas consumption in Poland in the aspect of energy transition. The intention of the publication was to determine the macroeconomic indicators that strongly affect natural gas consumption by the Polish industry and the quantitative growth of consumption depending on changes in these indicators. The results showed that the highest correlation of the growth of natural gas consumption is related to the production of chemistry, the chemical industry, and the power industry. Full article

(This article belongs to the Topic Exergy Analysis and Its Applications)

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11 pages, 949 KiB

Open AccessArticle

Experimental Analysis of GBM to Expand the Time Horizon of Irish Electricity Price Forecasts

by Conor Lynch, Christian O’Leary, Preetham Govind Kolar Sundareshan and Yavuz Akin

Energies 2021, 14(22), 7587; https://doi.org/10.3390/en14227587 - 12 Nov 2021

Cited by 4 | Viewed by 2451

Abstract

In response to the inherent challenges of generating cost-effective electricity consumption schedules for dynamic systems, this paper espouses the use of GBM or Gradient Boosting Machine-based models for electricity price forecasting. These models are applied to data streams from the Irish electricity market [...] Read more.

In response to the inherent challenges of generating cost-effective electricity consumption schedules for dynamic systems, this paper espouses the use of GBM or Gradient Boosting Machine-based models for electricity price forecasting. These models are applied to data streams from the Irish electricity market and achieve favorable results, relative to the current state-of-the-art. Presently, electricity prices are published 10 h in advance of the trade day of interest. Using the forecasting methodology outlined in this paper, an estimation of these prices can be made available one day in advance of the official price publication, thus extending the time available to plan electricity utilization from the grid to be as cost effectively as possible. Extreme Gradient Boosting Machine (XGBM) models achieved a Mean Absolute Error (MAE) of 9.93 for data from 30 September 2018 to 12 December 2019 which is an 11.4% improvement on the avant-garde. LGBM models achieve a MAE score 9.58 on more recent data: the full year of 2020. Full article

(This article belongs to the Topic Exergy Analysis and Its Applications)

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19 pages, 1936 KiB

Open AccessArticle

Research on a Solar Hybrid Trigeneration System Based on Exergy and Exergoenvironmental Assessments

by Eduardo J. C. Cavalcanti, João Victor M. Ferreira and Monica Carvalho

Energies 2021, 14(22), 7560; https://doi.org/10.3390/en14227560 - 12 Nov 2021

Cited by 4 | Viewed by 2384

Abstract

The environmental performance of a combined cooling, heating, and power system is analyzed in this study at a component-level using a SPECO-based exergoenvironmental analysis. The engine consumes natural gas and produces 168.6 kW net power. The waste heat is recovered by a LiBr-H [...] Read more.

The environmental performance of a combined cooling, heating, and power system is analyzed in this study at a component-level using a SPECO-based exergoenvironmental analysis. The engine consumes natural gas and produces 168.6 kW net power. The waste heat is recovered by a LiBr-H₂O absorption chiller and a heat exchanger, which are used for cooling and heating purposes. The energy system is assisted by a solar field. An environmental Life Cycle Assessment quantifies the environmental impacts of the system, and these data are combined with exergy evaluations. The highest total environmental impact rate, 23,740.16 mPt/h, is related to the internal combustion engine, of which pollutant formation is the primary source of environmental impact. Compared with a non-renewable energy system, the solar-assisted trigeneration system decreased the environmental impact per exergy unit of chilled water by 10.99%. Exergoenvironmental performance can be further improved by enhancing the exergy efficiency of the solution pump and high-pressure generator (HG), and by employing a treatment to remove nitrogen oxides in the reciprocating engine. Full article

(This article belongs to the Topic Exergy Analysis and Its Applications)

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19 pages, 3843 KiB

Open AccessArticle

Tackling Dissipative Components Based on the SPECO Approach: A Cryogenic Heat Exchanger Used in Natural Gas Liquefaction

by Eduardo J. C. Cavalcanti and Monica Carvalho

Energies 2021, 14(20), 6850; https://doi.org/10.3390/en14206850 - 19 Oct 2021

Cited by 4 | Viewed by 2632

Abstract

The cryogenic industry has been experiencing continuous progress in recent years, primarily due to the global development of oil and gas activities. Natural gas liquefaction is a cryogenic process, with the refrigeration system being crucial to the overall process. The objective of the [...] Read more.

The cryogenic industry has been experiencing continuous progress in recent years, primarily due to the global development of oil and gas activities. Natural gas liquefaction is a cryogenic process, with the refrigeration system being crucial to the overall process. The objective of the study presented herein is to carry out an exergoeconomic assessment for a dual nitrogen expander process used to liquefy natural gas, employing the SPecific Exergy COsting (SPECO) methodology. The air coolers and throttling valve are dissipative components, which present fictitious unit cost rates that are reallocated to the final product (Liquefied Natural Gas). The liquefaction process has an exergy efficiency of 41.89%, and the specific cost of liquefied natural gas is 292.30 US$/GJ. It was verified that this cost increased along with electricity. The highest exergy destruction rates were obtained for Expander 1 and Air cooler 2. The highest average cost per exergy unit of fuel was obtained for the vertical separator, followed by Air coolers 1 and 2. An assessment of the exergoeconomic factor indicated that both expanders could benefit from a decrease in exergy destruction, improving the exergoeconomic performance of the overall system. Regarding the relative cost difference, all compressors presented high values and can be enhanced with low efforts. Full article

(This article belongs to the Topic Exergy Analysis and Its Applications)

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39 pages, 6752 KiB

Open AccessArticle

Tailoring Mission Effectiveness and Efficiency of a Ground Vehicle Using Exergy-Based Model Predictive Control (MPC)

by Robert Jane, Tae Young Kim, Emily Glass, Emilee Mossman and Corey James

Energies 2021, 14(19), 6049; https://doi.org/10.3390/en14196049 - 23 Sep 2021

Cited by 4 | Viewed by 4120

Abstract

To ensure dominance over a multi-domain battlespace, energy and power utilization must be accurately characterized for the dissimilar operational conditions. Using MATLAB/Simulink in combination with multiple neural networks, we created a methodology which was simulated the energy dynamics of a ground vehicle in [...] Read more.

To ensure dominance over a multi-domain battlespace, energy and power utilization must be accurately characterized for the dissimilar operational conditions. Using MATLAB/Simulink in combination with multiple neural networks, we created a methodology which was simulated the energy dynamics of a ground vehicle in parallel to running predictive neural network (NN) based predictive algorithms to address two separate research questions: (1) can energy and exergy flow characterization be developed at a future point in time, and (2) can we use the predictive algorithms to extend the energy and exergy flow characterization and derive operational intelligence, used to inform our control based algorithms or provide optimized recommendations to a battlefield commander in real-time. Using our predictive algorithms we confirmed that the future energy and exergy flow characterizations could be generated using the NNs, which was validated through simulation using two separately created datasets, one for training and one for testing. We then used the NNs to implement a model predictive control (MPC) framework to flexibly operate the vehicles thermal coolant loop (TCL), subject to exergy destruction. In this way we could tailor the performance of the vehicle to accommodate a more mission effective solution or a less energy intensive solution. The MPC resulted in a more effective solution when compared to six other simulated conditions, which consumed less exergy than two of the six cases. Our results indicate that we can derive operational intelligence from the predictive algorithms and use it to inform a model predictive control (MPC) framework to reduce wasted energy and exergy destruction subject to the variable operating conditions. Full article

(This article belongs to the Topic Exergy Analysis and Its Applications)

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22 pages, 7753 KiB

Open AccessFeature PaperArticle

Performance Quantification of Enhanced Oil Recovery Methods in Fractured Reservoirs

by Riyaz Kharrat, Mehdi Zallaghi and Holger Ott

Energies 2021, 14(16), 4739; https://doi.org/10.3390/en14164739 - 4 Aug 2021

Cited by 15 | Viewed by 3509

Abstract

The enhanced oil recovery mechanisms in fractured reservoirs are complex and not fully understood. It is technically challenging to quantify the related driving forces and their interaction in the matrix and fractures medium. Gravity and capillary forces play a leading role in the [...] Read more.

The enhanced oil recovery mechanisms in fractured reservoirs are complex and not fully understood. It is technically challenging to quantify the related driving forces and their interaction in the matrix and fractures medium. Gravity and capillary forces play a leading role in the recovery process of fractured reservoirs. This study aims to quantify the performance of EOR methods in fractured reservoirs using dimensionless numbers. A systematic approach consisting of the design of experiments, simulations, and proxy-based optimization was used in this work. The effect of driving forces on oil recovery for water injection and several EOR processes such as gas injection, foam injection, water-alternating gas (WAG) injection, and foam-assisted water-alternating gas (FAWAG) injection was analyzed using dimensionless numbers and a surface response model. The results show that equilibrium between gravitational and viscous forces in fracture and capillary and gravity forces in matrix blocks determines oil recovery performance during EOR in fractured reservoirs. When capillary forces are dominant in gas injection, fluid exchange between fracture and matrix is low; consequently, the oil recovery is low. In foam-assisted water-alternating gas injection, gravity and capillary forces are in equilibrium conditions as several mechanisms are involved. The capillary forces dominate the water cycle, while gravitational forces govern the gas cycle due to the foam enhancement properties, which results in the highest oil recovery factor. Based on the performed sensitivity analysis of matrix–fracture interaction on the performance of the EOR processes, the foam and FAWAG injection methods were found to be more sensitive to permeability contrast, density, and matrix block highs than WAG injection. Full article

(This article belongs to the Topic Exergy Analysis and Its Applications)

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15 pages, 12213 KiB

Open AccessArticle

Optimizing Power and Thermal Efficiency of an Irreversible Variable-Temperature Heat Reservoir Lenoir Cycle

by Ruibo Wang, Lingen Chen, Yanlin Ge and Huijun Feng

Appl. Sci. 2021, 11(15), 7171; https://doi.org/10.3390/app11157171 - 3 Aug 2021

Cited by 17 | Viewed by 2511

Abstract

Applying finite-time thermodynamics theory, an irreversible steady flow Lenoir cycle model with variable-temperature heat reservoirs is established, the expressions of power (

P

) and efficiency (

η

) are derived. By numerical calculations, the characteristic relationships among

P

and

η

and the [...] Read more.

Applying finite-time thermodynamics theory, an irreversible steady flow Lenoir cycle model with variable-temperature heat reservoirs is established, the expressions of power (

P

) and efficiency (

η

) are derived. By numerical calculations, the characteristic relationships among

P

and

η

and the heat conductance distribution (

u_{L}

) of the heat exchangers, as well as the thermal capacity rate matching (

C_{w f 1} / C_{H}

) between working fluid and heat source are studied. The results show that when the heat conductances of the hot- and cold-side heat exchangers (

U_{H}

,

U_{L}

) are constants,

P - η

is a certain “point”, with the increase of heat reservoir inlet temperature ratio (

τ

),

U_{H}

,

U_{L}

, and the irreversible expansion efficiency (

η_{e}

),

P

and

η

increase. When

u_{L}

can be optimized,

P

and

η

versus

u_{L}

characteristics are parabolic-like ones, there are optimal values of heat conductance distributions (

u_{L_{P} (o p t)}

,

u_{L_{η} (o p t)}

) to make the cycle reach the maximum power and efficiency points (

P_{\max}

,

η_{\max}

). As

C_{w f 1} / C_{H}

increases,

P_{\max} - C_{w f 1} / C_{H}

shows a parabolic-like curve, that is, there is an optimal value of

C_{w f 1} / C_{H}

(

{(C_{w f 1} / C_{H})}_{o p t}

) to make the cycle reach double-maximum power point (

{(P_{\max})}_{\max}

); as

C_{L} / C_{H}

,

U_{T}

, and

η_{e}

increase,

{(P_{\max})}_{\max}

and

{(C_{w f 1} / C_{H})}_{o p t}

increase; with the increase in

τ

,

{(P_{\max})}_{\max}

increases, and

{(C_{w f 1} / C_{H})}_{o p t}

is unchanged. Full article

(This article belongs to the Topic Exergy Analysis and Its Applications)

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18 pages, 1495 KiB

Open AccessArticle

Cooking Fuel Usage in Sub-Saharan Urban Households

by Ting Meng, Wojciech J. Florkowski, Daniel B. Sarpong, Manjeet Chinnan and Anna V. A. Resurreccion

Energies 2021, 14(15), 4629; https://doi.org/10.3390/en14154629 - 30 Jul 2021

Cited by 7 | Viewed by 3560

Abstract

This study models the frequency use of wood, charcoal, liquid gas, electricity, and kerosene in urban households in Ghana and supplements the literature on cooking fuel choices. The modeling is based on survey data collected in several major Ghanaian cities. Survey results indicate [...] Read more.

This study models the frequency use of wood, charcoal, liquid gas, electricity, and kerosene in urban households in Ghana and supplements the literature on cooking fuel choices. The modeling is based on survey data collected in several major Ghanaian cities. Survey results indicate that charcoal and liquid gas are frequently used in meal preparation, while the frequency use of firewood, kerosene, and electricity is limited. Frequency use is estimated using the ordered probit technique. Five cooking fuel use equations identify income, socio-demographic characteristics, and location of urban residents as influencing the frequency use. Statistically significant effects measure probability changes in each of the four fuel categories. Income and education increase the probability of often or very often of using liquid gas or electricity to cook. The effect of being employed by the government is similar but less consistent. Age, household size, and marital status are linked to frequency use, but differently affect specific fuels. As the number of children or adults increases in a household, so does the probability of using firewood or charcoal, but this also increases the probability that such households never use liquid gas or electricity for cooking. Regional differences indicate Tamale residents heavily rely on wood and charcoal, and infrequently use liquid gas or electricity. Multiple cooking fuel use behavior may reflect risk aversion to fuel shortages. Increasing incomes and improving education will drive the probability of an increased use of cleaner cooking fuels and decreased use of fuel mixes, benefiting meal preparers’ health and the environment. Full article

(This article belongs to the Topic Exergy Analysis and Its Applications)

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21 pages, 3070 KiB

Open AccessArticle

Sustainability of Regional Agroecological Economic System Based on Emergy Theory: A Case Study of Anhui Province, China

by Xue Wu, Yaliu Yang, Conghu Liu, Guowei Xu, Yuxia Guo, Fan Liu and Yuan Wang

Sustainability 2021, 13(15), 8317; https://doi.org/10.3390/su13158317 - 26 Jul 2021

Cited by 3 | Viewed by 2341

Abstract

The agroecological economic system is the basic system on which human beings depend for survival. In order to better evaluate the operation status of a regional agroecological economic system and deepen the cognition of the input and output of the regional agroecological economic [...] Read more.

The agroecological economic system is the basic system on which human beings depend for survival. In order to better evaluate the operation status of a regional agroecological economic system and deepen the cognition of the input and output of the regional agroecological economic system from the angle of emergy, the evaluation method of sustainable development of the regional agroecological economic system with comprehensive consideration of resources, economy, and environment was proposed by constructing a unified dimensional measurement model. This paper analyzed and evaluated the data of the agroecological economic system in Anhui Province from 2010 to 2019. The results showed that the agroecological economic system in Anhui Province bore less environmental pressure and gradually decreased, and had a good system efficiency and economic benefits. The average emergy sustainability index (ESI) was 3.12, indicating that the agroecological economic system in Anhui Province had certain vitality of sustainable development. Based on this, the paper puts forward some suggestions on sustainable and high-quality agricultural development in Anhui Province, which provides theoretical and methodical support for sustainable development of a regional agricultural economy. Full article

(This article belongs to the Topic Exergy Analysis and Its Applications)

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18 pages, 3887 KiB

Open AccessArticle

Energy and Exergy Analysis of the Air Source Transcritical CO₂ Heat Pump Water Heater Using CO₂-Based Mixture as Working Fluid

by Yikai Wang, Yifan He, Yulong Song, Xiang Yin, Feng Cao and Xiaolin Wang

Energies 2021, 14(15), 4470; https://doi.org/10.3390/en14154470 - 23 Jul 2021

Cited by 6 | Viewed by 2718

Abstract

Given the large demand nowadays for domestic hot water, and its impact on modern building energy consumption, air source transcritical CO₂ heat pumps have been extensively adopted for hot water production. Since their system efficiency is limited by significant irreversibility, a CO [...] Read more.

Given the large demand nowadays for domestic hot water, and its impact on modern building energy consumption, air source transcritical CO₂ heat pumps have been extensively adopted for hot water production. Since their system efficiency is limited by significant irreversibility, a CO₂-based mixture could offer a promising drop-in technology to overcome this deficiency without increasing system complexity. Although many CO₂ blends have been studied in previously published literature, little has been presented about the CO₂/R32 mixture. Therefore, a proposed mixture for use in transcritical CO₂ heat pumps was analyzed using energy and exergy analysis. Results showed that the coefficient of performance and exergy efficiency variation displayed an “M” shape trend, and the optimal CO₂/R32 mixture concentration was determined as 0.9/0.1 with regard to flammability and efficiency. The irreversibility of the throttling valve was reduced from 0.031 to 0.009 kW⋅kW⁻¹ and the total irreversibility reduction was more notable with ambient temperature variation. A case study was also conducted to examine domestic hot water demand during the year. Pure CO₂ and the proposed CO₂ blend were compared with regard to annual performance factor and annual exergy efficiency, and the findings could provide guidance for practical applications in the future. Full article

(This article belongs to the Topic Exergy Analysis and Its Applications)

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15 pages, 3426 KiB

Open AccessArticle

The Physical Optimum as an Ideal Reference Value for Balancing Thermodynamic Processes Integrating the Exergetic Evaluation by the Example of Heat Supply

by Dirk Volta and Samanta A. Weber

Energies 2021, 14(15), 4426; https://doi.org/10.3390/en14154426 - 22 Jul 2021

Cited by 4 | Viewed by 2140

Abstract

This paper contains the basic definition and application of the physical optimum as a method for process evaluation and optimization. By means of the exemplary balance of a wood pellet-fired boiler, the conventional efficiency is compared to the PhO. Furthermore, this study [...] Read more.

This paper contains the basic definition and application of the physical optimum as a method for process evaluation and optimization. By means of the exemplary balance of a wood pellet-fired boiler, the conventional efficiency is compared to the PhO. Furthermore, this study demonstrates the possibility of applying the thermodynamic state variable exergy as a physical reference property of a system within the PhO method. To explain the approach, the heat generation in the wood pellet-fired boiler is compared to the supply from a heat pump, which itself is connected to a power plant. Furthermore, the process-independent PhO is explained in order to illustrate the limitations of feasible optimization. Additionally, possible research topics such as the integration of dynamic behavior in the method are approached. As a conclusion, the differences between the methods outline the advantage of the PhO in the optimization process. Full article

(This article belongs to the Topic Exergy Analysis and Its Applications)

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20 pages, 4161 KiB

Open AccessArticle

Power and Performance Evaluation of Memory-Intensive Applications

by Kaiqiang Zhang, Dongyang Ou, Congfeng Jiang, Yeliang Qiu and Longchuan Yan

Energies 2021, 14(14), 4089; https://doi.org/10.3390/en14144089 - 6 Jul 2021

Cited by 5 | Viewed by 4321

Abstract

In terms of power and energy consumption, DRAMs play a key role in a modern server system as well as processors. Although power-aware scheduling is based on the proportion of energy between DRAM and other components, when running memory-intensive applications, the energy consumption [...] Read more.

In terms of power and energy consumption, DRAMs play a key role in a modern server system as well as processors. Although power-aware scheduling is based on the proportion of energy between DRAM and other components, when running memory-intensive applications, the energy consumption of the whole server system will be significantly affected by the non-energy proportion of DRAM. Furthermore, modern servers usually use NUMA architecture to replace the original SMP architecture to increase its memory bandwidth. It is of great significance to study the energy efficiency of these two different memory architectures. Therefore, in order to explore the power consumption characteristics of servers under memory-intensive workload, this paper evaluates the power consumption and performance of memory-intensive applications in different generations of real rack servers. Through analysis, we find that: (1) Workload intensity and concurrent execution threads affects server power consumption, but a fully utilized memory system may not necessarily bring good energy efficiency indicators. (2) Even if the memory system is not fully utilized, the memory capacity of each processor core has a significant impact on application performance and server power consumption. (3) When running memory-intensive applications, memory utilization is not always a good indicator of server power consumption. (4) The reasonable use of the NUMA architecture will improve the memory energy efficiency significantly. The experimental results show that reasonable use of NUMA architecture can improve memory efficiency by 16% compared with SMP architecture, while unreasonable use of NUMA architecture reduces memory efficiency by 13%. The findings we present in this paper provide useful insights and guidance for system designers and data center operators to help them in energy-efficiency-aware job scheduling and energy conservation. Full article

(This article belongs to the Topic Exergy Analysis and Its Applications)

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20 pages, 8544 KiB

Open AccessArticle

Offshore Wind Potential of West Central Taiwan: A Case Study

by Wen-Ko Hsu and Chung-Kee Yeh

Energies 2021, 14(12), 3702; https://doi.org/10.3390/en14123702 - 21 Jun 2021

Cited by 2 | Viewed by 2919

Abstract

In this study, we present the wind distributions from a long-term offshore met mast and a novel approach based on the measure–correlate–predict (MCP) method from short-term onshore-wind-turbine data. The annual energy production (AEP) and capacity factors (CFs) of one onshore and four offshore [...] Read more.

In this study, we present the wind distributions from a long-term offshore met mast and a novel approach based on the measure–correlate–predict (MCP) method from short-term onshore-wind-turbine data. The annual energy production (AEP) and capacity factors (CFs) of one onshore and four offshore wind-turbine generators (WTG) available on the market are evaluated on the basis of wind-distribution analysis from both the real met mast and the MCP method. Here, we also consider the power loss from a 4-month light detection and ranging (LiDAR) power-curve test on an onshore turbine to enhance the accuracy of further AEP and CF evaluations. The achieved Weibull distributions could efficiently represent the probability distribution of wind-speed variation, mean wind speed (MWS), and both the scale and shape parameters of Weibull distribution in Taiwan sites. The power-loss effect is also considered when calculating the AEPs and CFs of different WTGs. Successful offshore wind development requires (1) quick, accurate, and economical harnessing of a wind resource and (2) selection of the most suitable and efficient turbine for a specific offshore site. Full article

(This article belongs to the Topic Exergy Analysis and Its Applications)

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15 pages, 7497 KiB

Open AccessArticle

Optimization Analysis of the Structural Design of NNBI Cryosorption Pumps

by Jiaqi Lang, Chundong Hu, Yuanlai Xie and Yunhua Tong

Energies 2021, 14(12), 3628; https://doi.org/10.3390/en14123628 - 18 Jun 2021

Cited by 7 | Viewed by 2049

Abstract

Cryosorption pumps create a vacuum by adsorbing gas at low temperature through porous solid adsorbents. The transmission probability of gas molecules and heat loads of cryosorption pumps are important factors affecting its performance. Herein, Molflow software based on the Monte Carlo principle is [...] Read more.

Cryosorption pumps create a vacuum by adsorbing gas at low temperature through porous solid adsorbents. The transmission probability of gas molecules and heat loads of cryosorption pumps are important factors affecting its performance. Herein, Molflow software based on the Monte Carlo principle is used to analyze the effects of the structural design of cryosorption pumps on transmission probability. The influence of structural design on radiation heat transfer is analyzed by ANSYS Steady-State Thermal software. This provides a reference for the design of a cryosorption pump to validate the prototype of a neutral beam injector for the China Engineering Fusion Experimental Reactor (CFETR). Full article

(This article belongs to the Topic Exergy Analysis and Its Applications)

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24 pages, 25400 KiB

Open AccessArticle

Numerical and Theoretical Study of Performance and Mechanical Behavior of PEM-FC Using Innovative Channel Geometrical Configurations

by Hussein A. Z. AL-bonsrulah, Mohammed J. Alshukri, Ammar I. Alsabery and Ishak Hashim

Appl. Sci. 2021, 11(12), 5597; https://doi.org/10.3390/app11125597 - 17 Jun 2021

Cited by 9 | Viewed by 2481

Abstract

Proton exchange membrane fuel cell (PEM-FC) aggregation pressure causes extensive strains in cell segments. The compression of each segment takes place through the cell modeling method. In addition, a very heterogeneous compressive load is produced because of the recurrent channel rib design of [...] Read more.

Proton exchange membrane fuel cell (PEM-FC) aggregation pressure causes extensive strains in cell segments. The compression of each segment takes place through the cell modeling method. In addition, a very heterogeneous compressive load is produced because of the recurrent channel rib design of the dipole plates, so that while high strains are provided below the rib, the domain continues in its initial uncompressed case under the ducts approximate to it. This leads to significant spatial variations in thermal and electrical connections and contact resistances (both in rib–GDL and membrane–GDL interfaces). Variations in heat, charge, and mass transfer rates within the GDL can affect the performance of the fuel cell (FC) and its lifetime. In this paper, two scenarios are considered to verify the performance and lifetime of the PEM-FC using different innovative channel geometries. The first scenario is conducted by adopting a constant channel height (H = 1 mm) for all the differently shaped channels studied. In contrast, the second scenario is conducted by taking a constant channel cross-sectional area (A = 1 mm²) for all the studied channels. Therefore, a computational fluid dynamics model (CFD) for a PEM fuel cell is formed through the assembly of FC to simulate the pressure variations inside it. The simulation results showed that a triangular cross-section channel provided the uniformity of the pressure distribution, with lower deformations and lower mechanical stresses. The analysis helped gain insights into the physical mechanisms that lead to the FC’s durability and identify important parameters under different conditions. The model shows that it can assume the intracellular pressure configuration toward durability and appearance containing limited experimental data. The results also proved that the better cell voltage occurs in the case of the rectangular channel cross-section, and therefore, higher power from the FC, although its durability is much lower compared to the durability of the triangular channel. The results also showed that the rectangular channel cross-section gave higher cell voltages, and therefore, higher power (0.63 W) from the fuel cell, although its durability is much lower compared to the durability of the triangular channel. Therefore, the triangular channel gives better performance compared to other innovative channels. Full article

(This article belongs to the Topic Exergy Analysis and Its Applications)

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14 pages, 5828 KiB

Open AccessArticle

Modular Marx Generator Based on SiC-MOSFET Generating Adjustable Rectangular Pulses

by Yahia Achour, Jacek Starzyński and Jacek Rąbkowski

Energies 2021, 14(12), 3492; https://doi.org/10.3390/en14123492 - 12 Jun 2021

Cited by 9 | Viewed by 4749

Abstract

The paper introduces a new design of Marx generator based on modular stages using Silicon Carbide MOSFETs (SiC-MOSFET) aimed to be used in biomedical applications. In this process, living cells are treated with intense nanosecond Pulsed Electrical Field (nsPEF). The electric field dose [...] Read more.

The paper introduces a new design of Marx generator based on modular stages using Silicon Carbide MOSFETs (SiC-MOSFET) aimed to be used in biomedical applications. In this process, living cells are treated with intense nanosecond Pulsed Electrical Field (nsPEF). The electric field dose should be controlled by adjusting the pulse parameters such as amplitude, repetition rate and pulse-width. For this purpose, the structure of the proposed generator enables negative pulses with a quasi-rectangular shape, controllable amplitude, pulse-width and repetition-rate. A complete simulation study was conducted in ANSYS-Simplorer to verify the overall performance. A compact, modular prototype of Marx generator was designed with 1.7 kV rated SiC-MOSFETs and, finally, a set of experiments confirmed all expected features. Full article

(This article belongs to the Topic Exergy Analysis and Its Applications)

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21 pages, 5782 KiB

Open AccessArticle

A Method of Multi-Stage Reservoir Water Level Forecasting Systems: A Case Study of Techi Hydropower in Taiwan

by Hao-Han Tsao, Yih-Guang Leu, Li-Fen Chou and Chao-Yang Tsao

Energies 2021, 14(12), 3461; https://doi.org/10.3390/en14123461 - 11 Jun 2021

Cited by 7 | Viewed by 2783

Abstract

Reservoirs in Taiwan often provide hydroelectric power, irrigation water, municipal water, and flood control for the whole year. Taiwan has the climatic characteristics of concentrated rainy seasons, instantaneous heavy rains due to typhoons and rainy seasons. In addition, steep rivers in mountainous areas [...] Read more.

Reservoirs in Taiwan often provide hydroelectric power, irrigation water, municipal water, and flood control for the whole year. Taiwan has the climatic characteristics of concentrated rainy seasons, instantaneous heavy rains due to typhoons and rainy seasons. In addition, steep rivers in mountainous areas flow fast and furiously. Under such circumstances, reservoirs have to face sudden heavy rainfall and surges in water levels within a short period of time, which often causes the water level to continue to rise to the full level even though hydroelectric units are operating at full capacity, and as reservoirs can only drain the flood water, this results in the waste of hydropower resources. In recent years, the impact of climate change has caused extreme weather events to occur more frequently, increasing the need for flood control, and the reservoir operation has faced severe challenges in order to fulfil its multipurpose requirements. Therefore, in order to avoid the waste of hydropower resources and improve the effectiveness of the reservoir operation, this paper proposes a real-time 48-h ahead water level forecasting system, based on fuzzy neural networks with multi-stage architecture. The proposed multi-stage architecture provides reservoir inflow estimation, 48-h ahead reservoir inflow forecasting, and 48-h ahead water level forecasting. The proposed method has been implemented at the Techi hydropower plant in Taiwan. Experimental results show that the proposed method can effectively increase energy efficiency and allow the reservoir water resources to be fully utilized. In addition, the proposed method can improve the effectiveness of the hydropower plant, especially when rain is heavy. Full article

(This article belongs to the Topic Exergy Analysis and Its Applications)

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11 pages, 2419 KiB

Open AccessArticle

Evaluation of Mechanical and Energetic Properties of the Forest Residues Shredded Chips during Briquetting Process

by Kamil Roman, Jan Barwicki, Witold Rzodkiewicz and Mariusz Dawidowski

Energies 2021, 14(11), 3270; https://doi.org/10.3390/en14113270 - 3 Jun 2021

Cited by 24 | Viewed by 2939

Abstract

The briquetting process is one of methods of solid biofuel production. During the briquetting of raw material, it can be noticed that material is viscoelastic, and reflects the effect on the volume and the final effect of the agglomerate during mentioned treatment. The [...] Read more.

The briquetting process is one of methods of solid biofuel production. During the briquetting of raw material, it can be noticed that material is viscoelastic, and reflects the effect on the volume and the final effect of the agglomerate during mentioned treatment. The research aimed to evaluate the mechanical and energetic properties of shredded pine forest residues during the briquetting process. The shredded fragments of the forest residues were compacted by the principal stresses with determination of the energy value consumed during the briquetting process. Tests were carried out using a specially designed compacting tube, with additional equipment directly mounted on the testing machine. The compaction process was carried out using the presented material and through continuous monitoring of the process parameters. During the study, it was estimated that the moisture content of the compacted material should be equal from 10 to 15%. The calculated average value of the unit energy consumption during the briquetting process (WB) was equal to 0.14 MJ·kg⁻¹. In future research, the mathematical model can serve as an algorithm in a computer program in order to calculate the flow of biomass in the extrusion process. Full article

(This article belongs to the Topic Exergy Analysis and Its Applications)

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11 pages, 1363 KiB

Open AccessArticle

Possibilities for Reducing CO and TOC Emissions in Thermal Waste Treatment Plants: A Case Study

by Janusz Bujak, Piotr Sitarz and Rafał Pasela

Energies 2021, 14(10), 2901; https://doi.org/10.3390/en14102901 - 17 May 2021

Cited by 2 | Viewed by 2853

Abstract

The technology of waste-management thermal processing may pose a threat to the natural environment through the emission of harmful substances, such as CO, NOx, SO₂, HCl, HF, total organic carbon (TOC) and dust, as well as dioxins and furans. Due to [...] Read more.

The technology of waste-management thermal processing may pose a threat to the natural environment through the emission of harmful substances, such as CO, NOx, SO₂, HCl, HF, total organic carbon (TOC) and dust, as well as dioxins and furans. Due to the advantages of thermal waste treatment, including the small volume of solid residue produced and possible thermal energy recovery, thermal waste treatment is widely applied. Continuous research is necessary to develop methods for reducing the risk of harmful substances being produced and methods for the effective removal of pollutants resulting from flue gases. This paper presents an analysis of the results and conditions of the experimental redesign of a thermal industrial waste (polypropylene) treatment plant. The purpose of the redesign was to improve the quality of gasification and afterburning processes taking place in the combustion and afterburner chambers (through the installation of an additional section), thus resulting in a reduction in the concentrations of CO and total organic carbon (TOC) in flue gases. The research concerned a facility implementing the combustion process on an industrial scale. The experiment led to a reduction in the average concentrations of carbon monoxide from 16.58 mg/m³ to 3.23 mg/m³ and of volatile organic compounds from 2.20 mg/m³ to 0.99 mg/m³. At the same time, no deterioration was observed in any of the remaining technological parameters of the plant, such as waste combustion performance and the energy efficiency of the thermal energy recovery system. Full article

(This article belongs to the Topic Exergy Analysis and Its Applications)

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24 pages, 252 KiB

Open AccessReview

Technical, Economic, Social and Regulatory Feasibility Evaluation of Dynamic Distribution Tariff Designs

by Kristoffer Christensen, Zheng Ma and Bo Nørregaard Jørgensen

Energies 2021, 14(10), 2860; https://doi.org/10.3390/en14102860 - 15 May 2021

Cited by 14 | Viewed by 2968

Abstract

The increasing number of distributed energy resources in the distribution grids creates the risk of grid congestion and the high cost of grid expansion. The implementation of the dynamic distribution grid tariffs can potentially avoid grid congestion. Meanwhile, the design and implementation of [...] Read more.

The increasing number of distributed energy resources in the distribution grids creates the risk of grid congestion and the high cost of grid expansion. The implementation of the dynamic distribution grid tariffs can potentially avoid grid congestion. Meanwhile, the design and implementation of any distribution tariff need to consider and match the regional/national requirements. However, there is no sufficient evaluation method available to review and evaluate the feasibility of the dynamic distribution tariffs. Therefore, this paper introduces a feasibility evaluation method with four dimensions of technical, economic, social, and regulatory to review dynamic distribution tariffs. The literature on dynamic distribution tariffs is collected, and 29 dynamic distribution tariffs are selected and further categorized into five attributes of rationale, cost drivers, dynamics, events, and active demand. The evaluation results show that the time-of-use tariff is the most feasible dynamic distribution tariff, and the review of a proposed future distribution tariff model in Denmark verifies the evaluation method and results. The developed feasibility evaluation method for dynamic distribution tariffs can ensure the design and implementation of a dynamic distribution tariff to be feasible and applicable in a region. Full article

(This article belongs to the Topic Exergy Analysis and Its Applications)

21 pages, 5815 KiB

Open AccessArticle

Fault-Tolerant Battery Power Network Architecture of Networked Swappable Battery Packs in Parallel

by Chung-Jen Chou, Shyh-Biau Jiang, Tse-Liang Yeh and Chein-Chung Sun

Energies 2021, 14(10), 2841; https://doi.org/10.3390/en14102841 - 14 May 2021

Cited by 3 | Viewed by 2392

Abstract

To improve the reliability and energy efficiency of battery swapping, we constructed a battery power network system with active redundancies and with multiple battery management controllers (one in each newly developed smart redundant battery pack). Each pack is getting ready to assume the [...] Read more.

To improve the reliability and energy efficiency of battery swapping, we constructed a battery power network system with active redundancies and with multiple battery management controllers (one in each newly developed smart redundant battery pack). Each pack is getting ready to assume the role of the major to coordinate direct safe mounting of the packs onto the power bus for load sharing or charging without the need for a direct current to direct current converter. This fault-tolerant architecture provides multiple backups in both management control and power supply. To verify this design, the mounting, insertion, and removal of the battery packs were executed during charging and discharging. Battery packs can be swapped on and off safely at any time regardless of their charging states. Battery packs can be direct safe mounted onto the power bus by a threshold algorithm. With each mount on event, the equivalent output energy conversion efficiency ranges from 98.3% to 99.2% throughout the transient. Moreover, when the major battery pack fails or gets removed, other battery packs can indeed assume the role of major safely. The reliability, energy efficiency, and safety of our system were verified. Full article

(This article belongs to the Topic Exergy Analysis and Its Applications)

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26 pages, 4113 KiB

Open AccessArticle

A Prediction Model for Battery Electric Bus Energy Consumption in Transit

by Hatem Abdelaty and Moataz Mohamed

Energies 2021, 14(10), 2824; https://doi.org/10.3390/en14102824 - 14 May 2021

Cited by 48 | Viewed by 6397

Abstract

This study investigates the impacts of vehicular, operational, topological, and external parameters on the energy consumption (E_C) of battery-electric buses (BEBs) in transit operation. Furthermore, the study develops a data-driven prediction model for BEB energy consumption in transit operation that considers [...] Read more.

This study investigates the impacts of vehicular, operational, topological, and external parameters on the energy consumption (E_C) of battery-electric buses (BEBs) in transit operation. Furthermore, the study develops a data-driven prediction model for BEB energy consumption in transit operation that considers these four parameters. A Simulink energy model is developed to estimate the E_C rates and validated using the Altoona’s test real-world data. A full-factorial experiment is used to generate 907,199 scenarios for BEB operation informed by 120 real-world drive cycles. A multivariate multiple regression model was developed to predict BEB’s E_C. The regression model explained more than 96% of the variation in the E_C of the BEBs. The results show the significant impacts of road grade, the initial state of charge, road condition, passenger loading, driver aggressiveness, average speed, HVAC, and stop density on BEB’s energy consumption, each with a different magnitude. The study concluded that the optimal transit profile for BEB operation is associated with rolling grade and relatively lower stop density (one to two stops/km). Full article

(This article belongs to the Topic Exergy Analysis and Its Applications)

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14 pages, 497 KiB

Open AccessEditor’s ChoiceReview

Coping with Energy Poverty: Measurements, Drivers, Impacts, and Solutions

by George E. Halkos and Eleni-Christina Gkampoura

Energies 2021, 14(10), 2807; https://doi.org/10.3390/en14102807 - 13 May 2021

Cited by 40 | Viewed by 7080

Abstract

Energy is required for socioeconomic development, and the world’s energy needs have significantly increased in the last decades. The lack of energy can have severe impacts on a person’s well-being; therefore, energy access should be ensured for everyone in the world. Energy poverty [...] Read more.

Energy is required for socioeconomic development, and the world’s energy needs have significantly increased in the last decades. The lack of energy can have severe impacts on a person’s well-being; therefore, energy access should be ensured for everyone in the world. Energy poverty usually refers to a situation where a household cannot be kept adequately warm, but it is a complex issue with many more aspects. This paper aims to present a comprehensive review of the energy poverty problem, particularly presenting various definitions given in the literature that capture the multi-dimensional nature of the problem and analyzing the different ways of measuring energy poverty (expenditure approach and consensual approach). In addition, the impacts of the problem are identified, including health, socioeconomic, and environmental impacts, as well as the drivers that can worsen energy poverty conditions, such as several household characteristics and various socioeconomic and environmental factors. The situation occurring currently in the world is also presented, including studies that focus on different world regions, and the different solutions that can help address the problem are discussed, including changes to the living environments and the use of new technologies. Full article

(This article belongs to the Topic Exergy Analysis and Its Applications)

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