Energies

Open AccessReview

Review on Mono and Hybrid Nanofluids: Preparation, Properties, Investigation, and Applications in IC Engines and Heat Transfer

by

Atul Bhattad

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Vinay Atgur

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Boggarapu Nageswar Rao

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N. R. Banapurmath

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T. M. Yunus Khan

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Chandramouli Vadlamudi

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Energies 2023, 16(7), 3189; https://doi.org/10.3390/en16073189 (registering DOI) - 31 Mar 2023

Abstract

Nano fluids are widely used today for various energy-related applications such as coolants, refrigerants, and fuel additives. New coolants and design modifications are being explored due to renewed interest in improving the working fluid properties of heat exchangers. Several studies have investigated nanofluids [...] Read more.

Nano fluids are widely used today for various energy-related applications such as coolants, refrigerants, and fuel additives. New coolants and design modifications are being explored due to renewed interest in improving the working fluid properties of heat exchangers. Several studies have investigated nanofluids to enhance radiator and heat exchanger performance. A new class of coolants includes single, binary, and tertiary nanoparticle-based hybrid nano-coolants using ethylene glycol/deionized water combinations as base fluids infused with different nanoparticles. This review article focuses on the hydrothermal behavior of heat exchangers (radiators for engine applications) with mono/hybrid nanofluids. The first part of the review focuses on the preparation of hybrid nanofluids, highlighting the working fluid properties such as density, viscosity, specific heat, and thermal conductivity. The second part discusses innovative methodologies adopted for accomplishing higher heat transfer rates with relatively low-pressure drop and pump work. The third part discusses the applications of mono and hybrid nanofluids in engine radiators and fuel additives in diesel and biodiesel blends. The last part is devoted to a summary of the research and future directions using mono and hybrid nanofluids for various cooling applications. Full article

(This article belongs to the Special Issue Recent Progress in Biodiesel and IC Engines)

Open AccessReview

Failure Detection Techniques on the Demand Side of Smart and Sustainable Compressed Air Systems: A Systematic Review

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Massimo Borg

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Paul Refalo

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Emmanuel Francalanza

Energies 2023, 16(7), 3188; https://doi.org/10.3390/en16073188 (registering DOI) - 31 Mar 2023

Abstract

The industrial sector is a crucial economic pillar, seeing annual increases in the production output. In the last few years, a greater emphasis has been placed on the efficient and sustainable use of resources within industry. The use of compressed air in this [...] Read more.

The industrial sector is a crucial economic pillar, seeing annual increases in the production output. In the last few years, a greater emphasis has been placed on the efficient and sustainable use of resources within industry. The use of compressed air in this field is hence gaining interest. These systems have numerous benefits, such as relative low investment costs and reliability; however, they suffer from low-energy efficiency and are highly susceptible to faults. Conventional detection systems, such as ultrasonic leak detection, can be used to identify faults. However, these methods are time consuming, meaning that leakages are often left unattended, contributing to additional energy wastage. Studies published in this area often focus on the supply side rather than the demand side of pneumatic systems. This paper offers a novel review based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) methodology of fault detection methods on the demand side of compressed air systems, leading towards a comprehensive understanding of smart and sustainable pneumatic systems. Fifty-three studies were classified and reviewed under the following three areas: (a) demand parameters which help in identifying fault sources; (b) approaches taken to analyse the parametric data; and (c) the role of Artificial Intelligence (AI) in pneumatic fault monitoring systems. This review shows that fault detection on the demand side has received greater importance in the last five years and that data analysis is crucial for AI to be implemented correctly. Nevertheless, it is clear that further research in this sector is essential, in order to investigate more complex systems. It is envisaged that this study can promote the adoption of such systems, contributing to an energy-efficient and cost-effective industry. Full article

Open AccessArticle

Escope: An Energy Efficiency Simulator for Internet Data Centers

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Energies 2023, 16(7), 3187; https://doi.org/10.3390/en16073187 (registering DOI) - 31 Mar 2023

Abstract

Contemporary megawatt-scale data centers have emerged to meet the increasing demand for online cloud services and big data analytics. However, in such large-scale data centers, servers of different generations are installed gradually year by year, making the data center heterogeneous in computing capability [...] Read more.

Contemporary megawatt-scale data centers have emerged to meet the increasing demand for online cloud services and big data analytics. However, in such large-scale data centers, servers of different generations are installed gradually year by year, making the data center heterogeneous in computing capability and energy efficiency. Furthermore, due to different processor architectures, complex and diverse load dynamic changing, business coupling, and other reasons, operators pay great attention to processor hardware power consumption and server aggregation energy efficiency. Therefore, the simulation and analysis of the energy efficiency characteristics of data center servers under different processor architectures can help operators understand the energy efficiency characteristics of data centers and make the optimal task scheduling strategy. This is very beneficial for improving the energy efficiency of the production system and the entire data center. The Escope simulator designed in this study can simulate the online quantity (placement strategy) of different types of servers in the data center and the optimal operating range of the servers. The purpose of this is to analyze the energy efficiency characteristics of all servers in the data center and provide data center operators with the energy efficiency and energy proportionality characteristics of different servers, improve server utilization, and perform reasonable scheduling. Through the simulation experiment of Escope, it can be proved that running the server at the highest energy efficiency point or running the server under full load cannot improve the energy efficiency of the entire data center. The simulation algorithm provided by Escope can select the optimal set of servers and their corresponding utilization. Escope can set up a variety of simulation strategies, and data center operators can simulate data center energy efficiency according to their own needs. Escope can also calculate the power cost savings of introducing new servers in the data center, which provides an essential reference for operators to purchase servers and design data centers. Full article

(This article belongs to the Special Issue Digital Transformation in the Energy Sector: Data-Driven Analytics, Services and Business Models)

Open AccessArticle

Energy Behaviors of Prosumers in Example of Polish Households

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Energies 2023, 16(7), 3186; https://doi.org/10.3390/en16073186 (registering DOI) - 31 Mar 2023

Abstract

This paper explores ways to save energy in households with energy prosumers who generate energy using photovoltaic panels and heat pumps. On the basis of a literature analysis, we formulated a research gap in the case of the energy behaviors of prosumers. This [...] Read more.

This paper explores ways to save energy in households with energy prosumers who generate energy using photovoltaic panels and heat pumps. On the basis of a literature analysis, we formulated a research gap in the case of the energy behaviors of prosumers. This research is important due to the growing demand for energy and the transitions of countries toward renewable energy sources. The role of prosumers in the economy is growing as they ensure energy independence and cost savings. The main purpose of this research is to understand the energy behaviors of prosumers and to examine the differences in energy behaviors between users of photovoltaic systems and heat pumps. A sample of 326 Polish prosumer households was selected using the CAWI method in order to obtain empirical data. The results suggest that prosumers show advanced ecological behaviors, and more than half of the respondents implement pro-ecological behaviors in their homes. Being a prosumer is associated with energy independence, which leads to economic stability and less dependence on traditional energy sources. The results indicate that prosumers show a general inclination toward pro-ecological behavior. Thus, this study recommends promoting prosumers and encouraging the use of pro-ecological energy as a priority for the economy. This initiative will contribute to a reduction in energy consumption in various areas, thus raising ecological awareness and a sense of responsibility for the environment. Full article

(This article belongs to the Collection Feature Papers in Energy, Environment and Well-Being)

Open AccessArticle

Assessment of the Impact of Technological Development and Scenario Forecasting of the Sustainable Development of the Fuel and Energy Complex

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Energies 2023, 16(7), 3185; https://doi.org/10.3390/en16073185 (registering DOI) - 31 Mar 2023

Abstract

The beginning of the 21st century for the fuel and energy complexes of most countries is characterized as a period of active restructuring and a fundamental shift in developmental priorities. The basis of these changes is technological development. Industry 4.0 technologies have particular [...] Read more.

The beginning of the 21st century for the fuel and energy complexes of most countries is characterized as a period of active restructuring and a fundamental shift in developmental priorities. The basis of these changes is technological development. Industry 4.0 technologies have particular importance in achieving maximum optimization of production processes. In the same way, they are applicable in establishing effective interaction between the energy sector and other sectors of the economy. The authors outline an approach to assessing the country’s fuel and energy balance state through the selected properties: sustainability, accessibility, efficiency, adaptability and reliability. Hence, a model of the fuel and energy complex was created on the example of the Russian Federation, considering the country’s territorial and functional division. The methodology is based on scenario modeling of the influence level of external challenges in conjunction with the accompanying technological development. The mathematical model allowed forecasting changes in the properties of the energy system. The scientific significance of the work lies in the application of a consistent hybrid modeling approach to forecast the state of the fuel and energy balance. The results of the study are useful in compiling scenarios for the regional and entire development of the fuel and energy complex. Further model improvements should include an expansion of the number of counted industries and their relations. Full article

(This article belongs to the Special Issue Challenges, Trends and Forecasting of Sustainable and Renewable Energy Systems)

Open AccessArticle

Structure Optimization of Ensemble Learning Methods and Seasonal Decomposition Approaches to Energy Price Forecasting in Latin America: A Case Study about Mexico

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Anne Carolina Rodrigues Klaar

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Stefano Frizzo Stefenon

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Laio Oriel Seman

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Viviana Cocco Mariani

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Leandro dos Santos Coelho

Energies 2023, 16(7), 3184; https://doi.org/10.3390/en16073184 (registering DOI) - 31 Mar 2023

Abstract

The energy price influences the interest in investment, which leads to economic development. An estimate of the future energy price can support the planning of industrial expansions and provide information to avoid times of recession. This paper evaluates adaptive boosting (AdaBoost), bootstrap aggregation [...] Read more.

The energy price influences the interest in investment, which leads to economic development. An estimate of the future energy price can support the planning of industrial expansions and provide information to avoid times of recession. This paper evaluates adaptive boosting (AdaBoost), bootstrap aggregation (bagging), gradient boosting, histogram-based gradient boosting, and random forest ensemble learning models for forecasting energy prices in Latin America, especially in a case study about Mexico. Seasonal decomposition of the time series is used to reduce unrepresentative variations. The Optuna using tree-structured Parzen estimator, optimizes the structure of the ensembles through a voter by combining several ensemble frameworks; thus an optimized hybrid ensemble learning method is proposed. The results show that the proposed method has a higher performance than the state-of-the-art ensemble learning methods, with a mean squared error of 3.37 × 10

^{- 9}

in the testing phase. Full article

(This article belongs to the Special Issue Coherent Security Planning for Power Systems)

Open AccessArticle

Heat Transfer Analysis of Sisko Fluid Flow over a Stretching Sheet in a Conducting Field with Newtonian Heating and Constant Heat Flux

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Pothala Jayalakshmi

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Mopuri Obulesu

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Charan Kumar Ganteda

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Malaraju Changal Raju

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Sibyala Vijayakumar Varma

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Giulio Lorenzini

Energies 2023, 16(7), 3183; https://doi.org/10.3390/en16073183 (registering DOI) - 31 Mar 2023

Abstract

The present study investigates the steady three-dimensional flow of a Sisko fluid over a bidirectional stretching sheet under the influence of Lorentz force. Heat transfer effects have been carried out for constant heat flux and Newtonian heating systems. The transformed governing equations of [...] Read more.

The present study investigates the steady three-dimensional flow of a Sisko fluid over a bidirectional stretching sheet under the influence of Lorentz force. Heat transfer effects have been carried out for constant heat flux and Newtonian heating systems. The transformed governing equations of the flow model are solved by using the spectral relaxation method (SRM), taking into account similarity transformations. The effects of controlling parameters on flow and derived quantities have been presented in the form of graphs and tables. Numerical benchmarks are used to characterise the effects of skin friction and heat transfer rates. It is noticed that in the case of Newtonian heating, the rate of heat transfer is higher than that in the constant heat flux case. As the stretching parameter increases, the fluid temperature decreases in both Newtonian heating and constant heat flux. It was discovered that successive over (under) relaxation (SOR) approaches will considerably boost the convergence speed and stability of the SRM system. The current findings strongly agree with earlier studies in the case of Newtonian fluid when the magnetic field is absent. Full article

(This article belongs to the Special Issue Turbulence and Fluid Mechanic)

Open AccessArticle

Comparison of Standalone and Hybrid Machine Learning Models for Prediction of Critical Heat Flux in Vertical Tubes

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Mansoor Hameed Inayat

Energies 2023, 16(7), 3182; https://doi.org/10.3390/en16073182 (registering DOI) - 31 Mar 2023

Abstract

Critical heat flux (CHF) is an essential parameter that plays a significant role in ensuring the safety and economic efficiency of nuclear power facilities. It imposes design and operational restrictions on nuclear power plants due to safety concerns. Therefore, accurate prediction of CHF [...] Read more.

Critical heat flux (CHF) is an essential parameter that plays a significant role in ensuring the safety and economic efficiency of nuclear power facilities. It imposes design and operational restrictions on nuclear power plants due to safety concerns. Therefore, accurate prediction of CHF using a hybrid framework can assist researchers in optimizing system performance, mitigating risk of equipment failure, and enhancing safety measures. Despite the existence of numerous prediction methods, there remains a lack of agreement regarding the underlying mechanism that gives rise to CHF. Hence, developing a precise and reliable CHF model is a crucial and challenging task. In this study, we proposed a hybrid model based on an artificial neural network (ANN) to improve the prediction accuracy of CHF. Our model leverages the available knowledge from a lookup table (LUT) and then employs ANN to further reduce the gap between actual and predicted outcomes. To develop and assess the accuracy of our model, we compiled a dataset of around 5877 data points from various sources in the literature. This dataset encompasses a diverse range of operating parameters for two-phase flow in vertical tubes. The results of this study demonstrate that the proposed hybrid model performs better than standalone machine learning models such as ANN, random forest, support vector machine, and data-driven lookup tables, with a relative root-mean-square error (rRMSE) of only 9.3%. We also evaluated the performance of the proposed hybrid model using holdout and cross-validation techniques, which demonstrated its robustness. Moreover, the proposed approach offers valuable insights into the significance of various input parameters in predicting CHF. Our proposed system can be utilized as a real-time monitoring tool for predicting extreme conditions in nuclear reactors, ensuring their safe and efficient operation. Full article

(This article belongs to the Special Issue Heat and Mass Transfer in Multiphase Flows)

Open AccessArticle

Design and Analysis of Grid-Connected Solar Photovoltaic Systems for Sustainable Development of Remote Areas

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Armin Razmjoo

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Arezoo Ghazanfari

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Poul Alberg Østergaard

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Sepideh Abedi

Energies 2023, 16(7), 3181; https://doi.org/10.3390/en16073181 - 31 Mar 2023

Abstract

This study analyses the expansion of solar energy in Iran, considering political, economic, social, and technological factors. Due to the prolonged sanctions on Iran, the development of clean energy power plants has been either halted or significantly reduced. Hence, this study aims to [...] Read more.

This study analyses the expansion of solar energy in Iran, considering political, economic, social, and technological factors. Due to the prolonged sanctions on Iran, the development of clean energy power plants has been either halted or significantly reduced. Hence, this study aims to identify barriers to the expansion of solar energy power plants and simulate solar power plants using PVsyst (Photovoltaic system) software. The study is unique in its approach of combining technical analysis with social sciences to facilitate the implementation of solar energy expansion in remote areas. This study focuses on two specific areas with high solar radiation, namely Darab and Meybod, which are located in Fars and Yazd provinces, respectively. Solar energy can be generated in these two areas due to their unique location with high levels of solar irritation. To achieve this goal, the technical analyses focuson simulating the performance of a 9 kWp (kilowatt ‘peak’ power output of a system) grid-connected polysilicon(poly-Si) photovoltaic plant for Darab and a 9.90 kWp plant for Meybod. The simulation is carried out to obtain maximum electricity production and evaluate parameters such as incident radiation, performance ratio, energy into the grid, energy output at the array, and losses. The produced energy for Darab was 20.40 MWh/year, with specific production of 2061 kWh/kWp/year, and the performance ratio (PR) was 81.26%. For Meybod, production was 20.70 MWh/year, with specific production of 2091 kWh/kWp/year, and the performance ratio (PR) was 80.88%. Through the PEST analysis, it is evident that strategic planning and appropriate actions are crucial at the provincial, national, and local levels for energy systems’ development. This indicates that both governments and citizens should play an active role in supporting the expansion of energy systems by planning and creating awareness among the public to embrace and adopt energy systems. Full article

(This article belongs to the Special Issue Optimizing Renewable-Energy-Driven Systems Using Thermodynamic, Economic, and Environmental Analyses)

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Open AccessArticle

Renewable Scenario Generation Based on the Hybrid Genetic Algorithm with Variable Chromosome Length

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Energies 2023, 16(7), 3180; https://doi.org/10.3390/en16073180 - 31 Mar 2023

Abstract

Determining the operation scenarios of renewable energies is important for power system dispatching. This paper proposes a renewable scenario generation method based on the hybrid genetic algorithm with variable chromosome length (HGAVCL). The discrete wavelet transform (DWT) is used to divide the original [...] Read more.

Determining the operation scenarios of renewable energies is important for power system dispatching. This paper proposes a renewable scenario generation method based on the hybrid genetic algorithm with variable chromosome length (HGAVCL). The discrete wavelet transform (DWT) is used to divide the original data into linear and fluctuant parts according to the length of time scales. The HGAVCL is designed to optimally divide the linear part into different time sections. Additionally, each time section is described by the autoregressive integrated moving average (ARIMA) model. With the consideration of temporal correlation, the Copula joint probability density function is established to model the fluctuant part. Based on the attained ARIMA model and joint probability density function, a number of data are generated by the Monte Carlo method, and the time autocorrelation, average offset rate, and climbing similarity indexes are established to assess the data quality of generated scenarios. A case study is conducted to verify the effectiveness of the proposed approach. The calculated time autocorrelation, average offset rate, and climbing similarity are 0.0515, 0.0396, and 0.9035, respectively, which shows the superior performance of the proposed approach. Full article

(This article belongs to the Special Issue Optimizing, Forecasting, Modeling and Applications of New Energy Microgrid/Grid)

Open AccessReview

A Review of Energy Management Systems and Organizational Structures of Prosumers

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Energies 2023, 16(7), 3179; https://doi.org/10.3390/en16073179 (registering DOI) - 31 Mar 2023

Abstract

This review provides the state of the art of energy management systems (EMS) and organizational structures of prosumers. Integration of renewable energy sources (RES) into the household brings new challenges in optimal operation, power quality, participation in the electricity market and power system [...] Read more.

This review provides the state of the art of energy management systems (EMS) and organizational structures of prosumers. Integration of renewable energy sources (RES) into the household brings new challenges in optimal operation, power quality, participation in the electricity market and power system stability. A common solution to these challenges is to develop an EMS with different prosumer organizational structures. EMS development is a multidisciplinary process that needs to involve several aspects of observation. This paper provides an overview of the prosumer organizational and control structures, types and elements, prediction methods of input parameters, optimization frameworks, optimization methods, objective functions, constraints and the market environment. Special attention is given to the optimization framework and prediction of input parameters, which represents room for improvement, that mitigate the impact of uncertainties associated with RES-based generation, consumption and market prices on optimal operation. Full article

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Open AccessReview

Energy Storage for Water Desalination Systems Based on Renewable Energy Resources

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Mohammad Ali Abdelkareem

Energies 2023, 16(7), 3178; https://doi.org/10.3390/en16073178 - 31 Mar 2023

Abstract

Recently, water desalination (WD) has been required for the supply of drinking water in a number of countries. Various technologies of WD utilize considerable thermal and/or electrical energies for removing undesirable salts. Desalination systems now rely on renewable energy resources (RERs) such as [...] Read more.

Recently, water desalination (WD) has been required for the supply of drinking water in a number of countries. Various technologies of WD utilize considerable thermal and/or electrical energies for removing undesirable salts. Desalination systems now rely on renewable energy resources (RERs) such as geothermal, solar, tidal, wind power, etc. The intermittent nature and changeable intensity constrain the wide applications of renewable energy, so the combination of energy storage systems (ESSs) with WD in many locations has been introduced. Thermal energy storage (TES) needs a convenient medium for storing and hence reuses energy. The present work provides a good background on the methods and technologies of WD. Furthermore, the concepts of both thermal and electrical energy storage are presented. In addition, a detailed review of employing ESSs in various WD processes driven by RERs is presented. The integration of energy storage with water desalination systems (WDSs) based on renewable energy has a much better capability, economically and environmentally, compared with conventional desalination systems. The ESSs are required to guarantee a constant supply of fresh water over the day. Full article

(This article belongs to the Special Issue The Prospects for Renewable Energy Storage: Technology, Process, and New Materials)

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Open AccessArticle

Study on Surface Configurations and Force Transfer Mechanism of Dual-Wedge Shaped Slips for Liner Hanger

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Energies 2023, 16(7), 3177; https://doi.org/10.3390/en16073177 (registering DOI) - 31 Mar 2023

Abstract

The penetration force and depth of the slip teeth are important factors influencing the hanging capacity of liner hanger, which can lead to failure of well cementation. In this study, a method to calculate the penetration force of dual-wedge slip teeth was presented [...] Read more.

The penetration force and depth of the slip teeth are important factors influencing the hanging capacity of liner hanger, which can lead to failure of well cementation. In this study, a method to calculate the penetration force of dual-wedge slip teeth was presented by considering the surface configuration and the force transfer mechanism of dual-wedge slip in three dimensions. The interaction between dual-wedge slips and casing was simulated using ABAQUS 6.14 software, and the contact force (penetration force) was obtained. Experimental research was carried out to verify the correction of calculation and simulation. The strain of casing was obtained after the dual-wedge slips set under axial loads. The experimental results, theoretical prediction, and the numerical simulation are in good agreement. The effects of geometrical parameters on force transfer characteristics were discussed, which shows that the penetration force of dual-wedge slips increases with increase in the liner weight and Eulerian angle γ, and it decreases with the increase in Eulerian angle α and friction coefficient. The geometric parameters of the dual-wedge slip can be designed to obtain an optimal penetration force, and ensure that the slip teeth penetrate into the inner wall of casing without damage to the casing. The penetration force can be obtained by optimizing the parameters related to geometry of dual-wedge slips. Full article

(This article belongs to the Special Issue Development of New Energy Materials/Devices and Their Safety)

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Open AccessArticle

Study of the Heat Exchange and Relaxation Conditions of Residual Stresses Due to Welding of Austenitic Stainless Steel

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Juan Pablo Carrasco-Amador

Energies 2023, 16(7), 3176; https://doi.org/10.3390/en16073176 (registering DOI) - 31 Mar 2023

Abstract

The present study presents a numerical prediction of residual stresses (RS) using the single-pass tungsten inert gas (TIG) welding process for stainless steel plates and the two-pass TIG welding process for stainless steel pipes. The effect of heat exchange between welding material and [...] Read more.

The present study presents a numerical prediction of residual stresses (RS) using the single-pass tungsten inert gas (TIG) welding process for stainless steel plates and the two-pass TIG welding process for stainless steel pipes. The effect of heat exchange between welding material and the environment was studied. The work consists of two parts: The first one is based on the determination of the existence of residual stresses numerically using Cast3M software, which has been validated by literature results. The second part addresses the means envisaged to attenuate the amplitudes of these residual stresses by practical methods. Two parameters with significant influence on the residual stresses have been chosen: the welding bead thickness and the torch displacement speed. The finite element model used has been validated experimentally, and the results obtained for the residual stresses have been compared with those given by the numerical study. The results obtained were found to be in agreement with references results. In addition, the microstructural analysis of different areas after welding of the solder joint (base metal, heat-affected zone and solder zone) was carried out using optical microscopy analysis. Full article

(This article belongs to the Section J1: Heat and Mass Transfer)

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Open AccessArticle

Thermal Performance Analysis of Micro Pin Fin Heat Sinks under Different Flow Conditions

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Jéssica Martha Nunes

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Jeferson Diehl de Oliveira

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Jacqueline Biancon Copetti

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Sameer Sheshrao Gajghate

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Utsab Banerjee

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Sushanta K. Mitra

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Elaine Maria Cardoso

Energies 2023, 16(7), 3175; https://doi.org/10.3390/en16073175 (registering DOI) - 31 Mar 2023

Abstract

Due to microscale effects, the segmented microchannels or micro pin fin heat sinks emerged as a high thermal management solution. In this context, the present work analyzes the influence of different heights of square micro pin fins with an aligned array and investigates [...] Read more.

Due to microscale effects, the segmented microchannels or micro pin fin heat sinks emerged as a high thermal management solution. In this context, the present work analyzes the influence of different heights of square micro pin fins with an aligned array and investigates their influence on pressure drop and heat transfer behavior. The HFE-7100 is used as the working fluid, and the pressure drop and surface temperature behavior are analyzed for different mass fluxes and inlet subcooling. The single-phase flow was analyzed numerically using the computational fluid dynamics (CFD) software ANSYS FLUENT^® for comparing the simulation results with the experimental data, showing that the highest micro pin fins configuration provides a more uniform and lowest wall temperature distribution compared to the lowest configuration. There is a good agreement between the experimental results and the numerical analysis, with a mean absolute error of 6% for all the considered parameters. For the two-phase flow condition, experimental tests were performed, and for the highest subcooling, an increase in mass flux causes an enhancement in the heat transfer for low heat flux; by increasing heat flux, there is a gradual predominance of boiling heat transfer over convection as the heat transfer mechanism. The pressure drop drastically increases with the vapor amount flowing into the system, regardless of the pin fin height; the boiling curves for the higher fin height show a much smaller slope and a smaller wall superheat than the fin with the smallest height, and consequently, a high heat transfer performance. A larger region of the heat sink is filled with vapor for lower inlet subcooling temperatures, degrading the heat transfer performance compared to higher inlet subcooling temperatures. Full article

(This article belongs to the Special Issue Heat Transfer and Fluid Dynamics in Boiling Systems)

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Open AccessArticle

Photovoltaic Systems through the Lens of Material-Energy-Water Nexus

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Megan Belongeay

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Gabriela Shirkey

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Marina Monteiro Lunardi

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Gonzalo Rodriguez-Garcia

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Energies 2023, 16(7), 3174; https://doi.org/10.3390/en16073174 - 31 Mar 2023

Abstract

Solar photovoltaics (PV) has emerged as one of the world’s most promising power-generation technologies, and it is essential to assess its applications from the perspective of a material-energy-water (MEW) nexus. We performed a life cycle assessment of the cradle-to-grave MEW for single-crystalline silicon [...] Read more.

Solar photovoltaics (PV) has emerged as one of the world’s most promising power-generation technologies, and it is essential to assess its applications from the perspective of a material-energy-water (MEW) nexus. We performed a life cycle assessment of the cradle-to-grave MEW for single-crystalline silicon (s-Si) and CdTe PV technologies by assuming both PV systems are recycled at end of life. We found that the MEW network was dominated by energy flows (>95%), while only minor impacts of materials and water flows were observed. Also, these MEW flows have pyramid-like distributions between the three tiers (i.e., primary, secondary/sub-secondary, and tertiary levels), with greater flows at the primary and lower flows at the tertiary levels. A more detailed analysis of materials’ circularity showed that glass layers are the most impactful component of recycling due to their considerable weight in both technologies. Our analysis also emphasized the positive impacts that increased power-conversion efficiency and the use of recycled feedstock have on the PV industry’s circularity rates. We found that a 25% increase in power-conversion efficiency and the use of fully recycled materials in PV panel feedstocks resulted in 91% and 86% material circularity for CdTe and s-Si PV systems, respectively. Full article

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Open AccessReview

3D Solar Harvesting and Energy Generation via Multilayers of Transparent Porphyrin and Iron Oxide Thin Films

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Jou Lin

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Mengyao Lyu

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Donglu Shi

Energies 2023, 16(7), 3173; https://doi.org/10.3390/en16073173 - 31 Mar 2023

Abstract

Photovoltaic solar cells have been extensively used for various applications and are considered one of the most efficient green energy sources. However, their 2D surface area solar harvesting has limitations, and there is an increasing need to explore the possibility of multiple layer [...] Read more.

Photovoltaic solar cells have been extensively used for various applications and are considered one of the most efficient green energy sources. However, their 2D surface area solar harvesting has limitations, and there is an increasing need to explore the possibility of multiple layer solar harvest for enhanced energy density. To address this, we have developed spectral-selective transparent thin films based on porphyrin and iron oxide compounds that allow solar light to penetrate multiple layers, significantly increasing solar harvesting surface area and energy density. These thin films are designed as photovoltaic (PV) and photothermal (PT) panels that can convert photons into either electricity or thermal energy for various green energy applications, such as smart building skins and solar desalination. The advantages of this 3D solar harvesting system include enlarged solar light collecting surface area and increased energy density. The multilayer system transforms the current 2D to 3D solar harvesting, enabling efficient energy generation. This review discusses recent developments in the synthesis and characterization of PV and PT transparent thin films for solar harvesting and energy generation using multilayers. Major applications of the 3D solar harvesting system are reviewed, including thermal energy generation, multilayered DSSC PV system, and solar desalination. Some preliminary data on transparent multilayer DSSC PVs are presented. Full article

(This article belongs to the Section A2: Solar Energy and Photovoltaic Systems)

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Open AccessArticle

Sustainable Environmental Impact Assessment Using Indicators for Sustainable Energy-Intensive Industrial Production

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Energies 2023, 16(7), 3172; https://doi.org/10.3390/en16073172 - 31 Mar 2023

Abstract

We have proposed an impact assessment methodology for determining sustainability in energy-intensive industrial production based on a comprehensive combination of economic, environmental, and social indicators for sustainable development. The goal of this study was to disclose this methodology for assessing sustainability in energy-intensive [...] Read more.

We have proposed an impact assessment methodology for determining sustainability in energy-intensive industrial production based on a comprehensive combination of economic, environmental, and social indicators for sustainable development. The goal of this study was to disclose this methodology for assessing sustainability in energy-intensive industrial production. We proved that any energy-intensive chemical, metallurgical, and energy generation processes should maximize the material output values and product value addition to ensure innovative sustainable development. We proposed indicators that determine the levels of increasing the sustainability of energy-intensive production as a whole, as well as taking into account individual technological processes. We proposed a procedure for making managerial decisions to increase the sustainability of energy-intensive outputs using the technological renewal of fixed assets and/or technological modernization of production. Our proposed methodology is based on a graphical model of the technological development’s life cycle of the existing energy-intensive production process. In addition, the proposed methodology ensures resource- and energy-efficiency intensification, together with the environmental safety of the technological processes. Full article

(This article belongs to the Special Issue Smart Energy and Sustainable Environment)

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Open AccessArticle

Green Jobs in the Energy Sector

by

Łukasz Jarosław Kozar

and

Adam Sulich

Energies 2023, 16(7), 3171; https://doi.org/10.3390/en16073171 - 31 Mar 2023

Abstract

This article analyzes Green Jobs (GJs) in the energy sector. GJs are naturally created in the processes related to the implementation of the Sustainable Development Goals (SDGs); this is especially visible in the 7th and 8th SDGs. There is currently a green transition [...] Read more.

This article analyzes Green Jobs (GJs) in the energy sector. GJs are naturally created in the processes related to the implementation of the Sustainable Development Goals (SDGs); this is especially visible in the 7th and 8th SDGs. There is currently a green transition from fossil fuels to renewable energy sources in the energy sector, and this mainly technological change also influences GJ creation. Despite this, there is a research gap related to green self-employment and GJ definitions. The goal of this paper is to explore the scientific literature collected from the Scopus database using a qualitative approach to present areas and keywords related to GJs in the energy sector. The adopted method is a Structured Literature Review (SLR), with the original query Q1. The retrieved data results of the SLR method were analyzed in the form of bibliometric maps of co-occurring keywords generated by the VOSviewer software, together with tables showing clusters of keyword features. As a result, the pivotal keywords and their clusters were identified. In this study, the most important scientific areas of GJ research in the energy sector were also indicated. This paper presents the current state of knowledge and the evolution of the subject of GJs in the energy sector, which can be useful for both researchers and practitioners. In the last section of this paper, possible new directions of future studies on the subject of GJ creation in the energy sector are identified. The limitations of this research and its practical implications are also addressed. Full article

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

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