Next Issue
Volume 14, June-2
Previous Issue
Volume 14, May-2
energies-logo

Journal Browser

Journal Browser

Energies, Volume 14, Issue 11 (June-1 2021) – 386 articles

Cover Story (view full-size image): Municipal biowastes, such as the organic fraction of municipal solid waste (OFMSW) that is collected separately via the biowaste bin, represent important resources for a circular economy. Anaerobic digestion (AD) and composting are the most relevant processes for the utilization of OFMSW. They can be operated either as single technologies or in cascade connection. However, the inherent energetic and material use potential of OFMSW is not fully exploited in both cases. Hydrothermal treatment (HTT) approaches are suitable for processing wet biomasses. They can supplement AD and composting to further increase the utilization efficiency of OFMSW. In this project, HTT below 200 °C was applied on OFMSW samples focusing on the generation of solid products with optimized characteristics for energetic utilization. View this paper.
  • Issues are regarded as officially published after their release is announced to the table of contents alert mailing list.
  • You may sign up for e-mail alerts to receive table of contents of newly released issues.
  • PDF is the official format for papers published in both, html and pdf forms. To view the papers in pdf format, click on the "PDF Full-text" link, and use the free Adobe Readerexternal link to open them.
Order results
Result details
Select all
Export citation of selected articles as:
Article
Modeling, Analysis and Optimization of Grid-Integrated and Islanded Solar PV Systems for the Ethiopian Residential Sector: Considering an Emerging Utility Tariff Plan for 2021 and Beyond
Energies 2021, 14(11), 3360; https://0-doi-org.brum.beds.ac.uk/10.3390/en14113360 - 07 Jun 2021
Cited by 1 | Viewed by 539
Abstract
Currently, difficulties such as the depletion of fossil fuel resources and the associated environmental pollution have driven the rise of other energy systems based on green energy sources. In this research, modeling and a viability study of grid-connected and islanded photovoltaic (PV) power [...] Read more.
Currently, difficulties such as the depletion of fossil fuel resources and the associated environmental pollution have driven the rise of other energy systems based on green energy sources. In this research, modeling and a viability study of grid-connected and islanded photovoltaic (PV) power systems for supplying the residential load in Mekelle City, Ethiopia, were carried out considering the country’s emerging utility tariff plan for 2021 and beyond. The technical viability of the proposed supply option was analyzed using PVGIS, PVWatts and HOMER Pro tool, while the economic and environmental optimization aspects were carried out using HOMER Pro. Sensitivity analyses and output comparisons among the three renewable energy simulation tools are presented. The results showed that under the consideration of an incremental electricity tariff plan (up to 2021), the analyzed cost of energy of the grid/PV system is around 12% lower than the utility grid tariff. Moreover, we also found that by taking the continuous global solar PV cost reduction into account, the cost of energy of the modeled islanded operation of solar PV power units totally broke the grid tariff in Ethiopia after 2029 based on the tariff for 2021 and well before with the expected escalation of the grid tariff on an annual basis. The technical performance of the system realized through PVGIS and PVWatts was almost comparable to the HOMER Pro outputs. Thus, this investigation will offer a clear direction to the concerned target groups and policy developers in the evolution of PV power supply options throughout the technically viable locations in the country. Full article
(This article belongs to the Special Issue Solar Energy: Potential and Future Prospects)
Show Figures

Figure 1

Article
Assessment of Passive Retrofitting Scenarios in Heritage Residential Buildings in Hot, Dry Climates
Energies 2021, 14(11), 3359; https://0-doi-org.brum.beds.ac.uk/10.3390/en14113359 - 07 Jun 2021
Viewed by 645
Abstract
Retrofitting heritage buildings for energy efficiency is not always easy where cultural values are highly concerned, which requires an integrated approach. This paper aims to assess the potential of applying passive retrofitting scenarios to enhance indoor thermal comfort of heritage buildings in North [...] Read more.
Retrofitting heritage buildings for energy efficiency is not always easy where cultural values are highly concerned, which requires an integrated approach. This paper aims to assess the potential of applying passive retrofitting scenarios to enhance indoor thermal comfort of heritage buildings in North Africa, as a hot climate, a little attention has been paid to retrofit built heritage in that climate. A mixed-mode ventilation residential building in Cairo, Egypt, was selected as a case study. The study combines field measurements and observations with energy simulations. A simulation model was created and calibrated on the basis of monitored data in the reference building, and the thermal comfort range was evaluated. Sets of passive retrofitting scenarios were proposed. The results (based on the ASHRAE-55-2020 adaptive comfort model at 90% acceptability limits) showed that the annual thermal comfort in the reference building is very low, i.e., 31.4%. The application of hybrid passive retrofitting scenarios significantly impacts indoor thermal comfort in the reference building, where annual comfort hours of up to 66% can be achieved. The originality of this work lies in identifying the most effective energy measures to improve indoor thermal comfort that are optimal from a conservation point of view. The findings contribute to set a comprehensive retrofitting tool that avoids potential risks for the conservation of residential heritage buildings in hot climates. Full article
Show Figures

Graphical abstract

Article
Comparative Study on the Calendar Aging Behavior of Six Different Lithium-Ion Cell Chemistries in Terms of Parameter Variation
Energies 2021, 14(11), 3358; https://0-doi-org.brum.beds.ac.uk/10.3390/en14113358 - 07 Jun 2021
Viewed by 735
Abstract
The degradation of lithium-ion cells is an important aspect, not only for quality management, but also for the customer of the application like, e.g., scooters or electric vehicles. During the lifetime of the system, the overall health on the battery plays a key [...] Read more.
The degradation of lithium-ion cells is an important aspect, not only for quality management, but also for the customer of the application like, e.g., scooters or electric vehicles. During the lifetime of the system, the overall health on the battery plays a key role in its depreciation. Therefore, it is necessary to monitor the health of the battery during operation, i.e., cycle life, but also during stationary conditions, i.e., calendar aging. In this work, the degradation due to calendar aging is analyzed for six different cell chemistries in terms of capacity degradation and impedance increase and their performance are being compared. In a new proposed metric, the relative deviations between various cells with the exact identical aging history are being analyzed for their degradation effects and their differences, which stands out in comparison to similar research. The capacity loss was found to be most drastic at 60 °C and at higher storage voltages, even for titanate-oxide cells. LiNiMnCoO2 (NMC), LiNiCoAlO2 (NCA) and Li2TiO3 (LTO) cells at 60 °C showed the most drastic capacity decrease. NMC and NCA cells at 60 °C and highest storage voltage did not show any open circuit voltage, as their current interrupt mechanism triggered. The effect of aging shows no uniform impact on the changes in the capacity variance when comparing different aging conditions, with respect to the evaluated standard deviation for all cells. The focus of this work was on the calendar aging effect and may be supplemented in a second study for cyclic aging. Full article
(This article belongs to the Special Issue High-Capacity Cells and Batteries for Electric Vehicles)
Show Figures

Figure 1

Article
Regional Diversity of Technical Efficiency in Agriculture as a Results of an Overinvestment: A Case Study from Poland
Energies 2021, 14(11), 3357; https://0-doi-org.brum.beds.ac.uk/10.3390/en14113357 - 07 Jun 2021
Viewed by 496
Abstract
Ensuring adequate profitability of production, which can be ensured by optimal investments, can encourage farmers to be more caring about sustainable development. Several existing studies indicate that technical efficiency in agriculture varies regionally. Investments comprise a basic way to increase efficiency and thus [...] Read more.
Ensuring adequate profitability of production, which can be ensured by optimal investments, can encourage farmers to be more caring about sustainable development. Several existing studies indicate that technical efficiency in agriculture varies regionally. Investments comprise a basic way to increase efficiency and thus reduce polarisation between regions. However, contrary to established assumptions, not every investment leads to increased efficiency, which entails a phenomenon of overinvestment. Investments should, by definition, be positively correlated with efficiency. However, existing studies indicate the existence of a significant problem of overinvestment, where increased efficiency may not occur. While for about 40% of farms in Poland the scale of investments can be assessed as optimal, more than quarter of farms exhibited absolute overinvestment and nearly one in five farms is underinvested. In response to this problem, this study aimed to identify regional differences in Poland with regard to overinvestment in farms, as well as to determine changes in farm efficiency depending on the region and level of overinvestment. The source material used in the following article consisted of unpublished Farm Accountancy Data Network (FADN) microdata derived from the DG AGRI of the European Commission. The study covered the period 2004–2015. For an original classification of farms according to their level of overinvestment the technical efficiency, using the stochastic frontier analysis approach, was used for determining regional differences that occurred as a result of overinvestment. Stochastic frontier analysis shown noticeable differences in the average technical efficiency for different overinvestment groups. As expected, underinvested farms are the least efficient (general in Poland and in all analyzed regions) and average technical efficiency did not increase. Interestingly, optimally investing farms do not have the highest technical efficiency. Higher efficiency was achieved by both relatively and absolutely overinvested farms. This is due to the fact that in order to produce efficiently in agriculture, it is necessary to at least maintain the level of tangible assets provision, and preferably to increase it as well. In terms of overinvestment levels, farm structure does not differ significantly between individual regions in Poland. However, there are differences between regions in terms of farm efficiency within each group. In all regions, only the underinvested farms did not increase their efficiency over the period under review and the highest efficiency growth rate was in regions where farms were least efficient at baseline. Full article
Show Figures

Figure 1

Article
Assessment of the Environmental Impact of Using Methane Fuels to Supply Internal Combustion Engines
Energies 2021, 14(11), 3356; https://0-doi-org.brum.beds.ac.uk/10.3390/en14113356 - 07 Jun 2021
Viewed by 480
Abstract
This research paper studied the environmental impact of using methane fuels for supplying internal combustion engines. Methane fuel types and the methods of their use in internal combustion engines were systematized. The knowledge regarding the environmental impact of using methane fuels for supplying [...] Read more.
This research paper studied the environmental impact of using methane fuels for supplying internal combustion engines. Methane fuel types and the methods of their use in internal combustion engines were systematized. The knowledge regarding the environmental impact of using methane fuels for supplying internal combustion engines was analyzed. The authors studied the properties of various internal combustion engines used for different applications (specialized engines of power generators—Liebherr G9512 and MAN E3262 LE212, powered by biogas, engine for road and off-road vehicles—Cummins 6C8.3, in self-ignition, original version powered by diesel fuel, and its modified version—a spark-ignition engine powered by methane fuel) under various operating conditions in approval tests. The sensitivity of the engine properties, especially pollutant emissions, to its operating states were studied. In the case of a Cummins 6C8.3 modified engine, a significant reduction in the pollutant emission owing to the use of methane fuel, relative to the original self-ignition engine, was found. The emission of carbon oxide decreased by approximately 30%, hydrocarbons by approximately 70% and nitrogen oxide by approximately 50%, as well as a particulate matter emission was also eliminated. Specific brake emission of carbon oxide is the most sensitive to the operating states of the engine: 0.324 for a self-ignition engine and 0.264 for a spark-ignition engine, with the least sensitive being specific brake emission of nitrogen oxide: 0.121 for a self-ignition engine and 0.097 for a spark-ignition engine. The specific brake emission of carbon monoxide and hydrocarbons for stationary engines was higher in comparison with both versions of Cummins 6C8.3 engine. However, the emission of nitrogen oxide for stationary engines was lower than for Cummins engines. Full article
(This article belongs to the Collection Feature Papers in Energy, Environment and Well-Being)
Show Figures

Figure 1

Article
Model of Flow Resistance Coefficient for a Fragment of a Porous Material Deposit with Skeletal Structure
Energies 2021, 14(11), 3355; https://0-doi-org.brum.beds.ac.uk/10.3390/en14113355 - 07 Jun 2021
Viewed by 450
Abstract
The hydrodynamic conditions resulting from the permeability of porous materials are based not only on the assessment of the gas flow through these materials, but also the losses related to the pressure energy in this flow. Flow resistance is a direct measure of [...] Read more.
The hydrodynamic conditions resulting from the permeability of porous materials are based not only on the assessment of the gas flow through these materials, but also the losses related to the pressure energy in this flow. Flow resistance is a direct measure of this loss. The aim of this experimental research was to evaluate the flow resistance of the porous material in relation to the gas flow. The research was carried out on a material with a slit-porous structure. The tests were carried out on a system for measuring gas permeability under the conditions of gas bubbling through the char. The issue of the total pressure drop process in the porous bed was considered in the Reynolds number category. The coefficient of flow resistance for the char was determined and the value of this coefficient was compared with the gas stream, and an experimental evaluation of the total pressure drop on the porous bed was made. The novelty of this article is the determination of the tortuosity and the gas permeability coefficient for a solid of any shape—a rigid skeleton. Full article
(This article belongs to the Special Issue Energy Crops Production in Central and Eastern Europe)
Show Figures

Figure 1

Article
Identification of Independent Variables to Assess Green-Building Development in China Based on Grounded Theory
Energies 2021, 14(11), 3354; https://0-doi-org.brum.beds.ac.uk/10.3390/en14113354 - 07 Jun 2021
Viewed by 426
Abstract
Background: Development of green building as future buildings has become a trend and played a significant role in changing the general direction of building development and creating an environment for sustainable development ’People-centric’ explores the relationship between people and building development. From [...] Read more.
Background: Development of green building as future buildings has become a trend and played a significant role in changing the general direction of building development and creating an environment for sustainable development ’People-centric’ explores the relationship between people and building development. From the perspective of users, what are the influencing factors of green building? What is the relationship between independent variables? The authors link this issue to the development of green building and gaining a clearer understanding and direction. Methods: The authors applied grounded theory and intensity sampling to analyse the relationships of independent variables. Results: The findings of this study reveal the four core factors affecting how independent variables get to learn about green building, which are ‘personal perception elements’, ‘social elements’, ‘organisational elements’, and ‘architectural properties’. Conclusions: The authors also analysed the relationships between the independent variables to explore construction theory for helping green building better respond to people’s demand and pushing forward its development. In this case, the ’people-centric’ green building further improves the urban living environment. Full article
(This article belongs to the Section Energy and Buildings)
Show Figures

Figure 1

Article
Model Predictive Control versus Traditional Relay Control in a High Energy Efficiency Greenhouse
Energies 2021, 14(11), 3353; https://0-doi-org.brum.beds.ac.uk/10.3390/en14113353 - 07 Jun 2021
Viewed by 512
Abstract
The sustainable agriculture cultivation in greenhouses is constantly evolving thanks to new technologies and methodologies able to improve the crop yield and to solve the common concerns which occur in protected environments. In this paper, an MPC-based control system has been realized in [...] Read more.
The sustainable agriculture cultivation in greenhouses is constantly evolving thanks to new technologies and methodologies able to improve the crop yield and to solve the common concerns which occur in protected environments. In this paper, an MPC-based control system has been realized in order to control the indoor air temperature in a high efficiency greenhouse. The main objective is to determine the optimal control signals related to the water mass flow rate supplied by a heat pump. The MPC model allows a predefined temperature profile to be tracked with an energy saving approach. The MPC has been implemented as a multiobjective optimization model that takes into account the dynamic behavior of the greenhouse in terms of energy and mass balances. The energy supply is provided by a ground coupled heat pump (GCHP) and by the solar radiation while the energy losses related to heat transfers across the glazed envelope. The proposed MPC method was applied in a smart innovative greenhouse located in Italy, and its performances were compared with a traditional reactive control method in terms of deviation of the indoor temperature in respect to the desired one and in terms of electric power consumption. The results demonstrated that, for a time horizon of 20 h, in a greenhouse with dimensions 15.3 and 9.9 m and an average height of 4.5 m, the proposed MPC approach saved about 30% in electric power compared with a relay control, guaranteeing a consistent and reliable temperature profile in respect to the predefined tracked one. Full article
Show Figures

Figure 1

Article
An Experimental Study of a Wine Batch Distillation in a Copper Pot Still Heated by Gas
Energies 2021, 14(11), 3352; https://0-doi-org.brum.beds.ac.uk/10.3390/en14113352 - 07 Jun 2021
Viewed by 450
Abstract
Wine batch distillation in a copper pot still heated directly by combustion is unusual. It is a niche sector. Few studies are available on the subject and even fewer have studied it from a thermal point of view. In a context of ecology [...] Read more.
Wine batch distillation in a copper pot still heated directly by combustion is unusual. It is a niche sector. Few studies are available on the subject and even fewer have studied it from a thermal point of view. In a context of ecology awareness and regularly increasing gas taxes, finding less energy consuming and more performing solutions has become necessary. Two methods already exist to recover energy for such pot stills, however improvements could be made. The present study focuses on the heating zone of an experimental pot still. First, a thermal diagnosis based on a nodal model is conducted in transient regime. The major sites of energy expenditure and waste are thus identified and quantified. Results highlight significant losses both in combustion smoke and by conduction to the environment resulting from a limited thermal performance of the system. Proposals are then made to enhance it. For instance, the preheating could be optimized and more thermal waste could be recovered. Full article
(This article belongs to the Section Energetics)
Show Figures

Figure 1

Article
Customized yet Standardized Temperature Derivatives: A Non-Parametric Approach with Suitable Basis Selection for Ensuring Robustness
Energies 2021, 14(11), 3351; https://0-doi-org.brum.beds.ac.uk/10.3390/en14113351 - 07 Jun 2021
Viewed by 446
Abstract
Previous studies have demonstrated that non-parametric hedging models using temperature derivatives are highly effective in hedging profit/loss fluctuation risks for electric utilities. Aiming for the practical applications of these methods, this study performs extensive empirical analyses and makes methodological customizations. First, we consider [...] Read more.
Previous studies have demonstrated that non-parametric hedging models using temperature derivatives are highly effective in hedging profit/loss fluctuation risks for electric utilities. Aiming for the practical applications of these methods, this study performs extensive empirical analyses and makes methodological customizations. First, we consider three types of electric utilities being exposed to risks of “demand”, “price”, and their “product (multiplication)”, and examine the design of an appropriate derivative for each utility. Our empirical results show that non-parametrically priced derivatives can maximize the hedge effect when a hedger bears a “price risk” with high nonlinearity to temperature. In contrast, standard derivatives are more useful for utilities with only “demand risk” in having a comparable hedge effect and in being liquidly traded. In addition, the squared prediction error derivative on temperature has a significant hedge effect on both price and product risks as well as a certain effect on demand risk, which illustrates its potential as a new standard derivative. Furthermore, spline basis selection, which may be overlooked by modeling practitioners, improves hedge effects significantly, especially when the model has strong nonlinearities. Surprisingly, the hedge effect of temperature derivatives in previous studies is improved by 13–53% by using an appropriate new basis. Full article
(This article belongs to the Special Issue Forecasting and Risk Management Techniques for Electricity Markets)
Show Figures

Figure 1

Article
Overview of Solutions for the Low-Temperature Operation of Domestic Hot-Water Systems with a Circulation Loop
Energies 2021, 14(11), 3350; https://0-doi-org.brum.beds.ac.uk/10.3390/en14113350 - 07 Jun 2021
Viewed by 510
Abstract
The operation of typical domestic hot water (DHW) systems with a storage tank and circulation loop, according to the regulations for hygiene and comfort, results in a significant heat demand at high operating temperatures that leads to high return temperatures to the district [...] Read more.
The operation of typical domestic hot water (DHW) systems with a storage tank and circulation loop, according to the regulations for hygiene and comfort, results in a significant heat demand at high operating temperatures that leads to high return temperatures to the district heating system. This article presents the potential for the low-temperature operation of new DHW solutions based on energy balance calculations and some tests in real buildings. The main results are three recommended solutions depending on combinations of the following three criteria: district heating supply temperature, relative circulation heat loss due to the use of hot water, and the existence of a low-temperature space heating system. The first solution, based on a heating power limitation in DHW tanks, with a safety functionality, may secure the required DHW temperature at all times, resulting in the limited heating power of the tank, extended reheating periods, and a DH return temperature of below 30 °C. The second solution, based on the redirection of the return flow from the DHW system to the low-temperature space heating system, can cool the return temperature to the level of the space heating system return temperature below 35 °C. The third solution, based on the use of a micro-booster heat pump system, can deliver circulation heat loss and result in a low return temperature below 35 °C. These solutions can help in the transition to low-temperature district heating. Full article
Show Figures

Figure 1

Case Report
Community-Based Business on Small Hydropower (SHP) in Rural Japan: A Case Study on a Community Owned SHP Model of Ohito Agricultural Cooperative
Energies 2021, 14(11), 3349; https://0-doi-org.brum.beds.ac.uk/10.3390/en14113349 - 07 Jun 2021
Viewed by 983
Abstract
Energy is the prerequisite for social and economic development of a community and country. In Japan, national government is promoting small hydropower (SHP) through a renewable energy policy by providing a high FIT price of 34 yen (≒0.32 US$/kWh) on energy generated from [...] Read more.
Energy is the prerequisite for social and economic development of a community and country. In Japan, national government is promoting small hydropower (SHP) through a renewable energy policy by providing a high FIT price of 34 yen (≒0.32 US$/kWh) on energy generated from an SHP of less than 200 kW. Until now, the energy generation was controlled by national government agencies, but now independent power generation businesses are growing at the local community level in rural Japan. For the future growth of SHP, it is necessary to make electricity generation at the local community level. Therefore, these local communities will install and manage their renewable electricity by themselves. It will help to make the community self-sustainable and independent from the national government, and at the same time, it will also lead them to achieve the Sustainable Developments Goals (SDGs) target from community-based action. This paper aimed to discuss an SHP development business model in which local community will become the business owner of the SHP. It means “of the community, by the community and for the community”. The community identifies their renewable energy potential and needs, they borrow money from the financial organization or banks, install the power plant and do necessary maintenance and management by themselves. The revenue earned by selling electricity is used to repay the loan, and the rest is used for community development directly (such as local roads construction, agriculture land improvements, community hall maintenance, waterways maintenance, welfare, etc.). This paper also discussed a community-based 50 kW SHP installed in Miyazaki prefecture of Japan as a case study. This SHP is one of the best examples of a community ownership model (Community-based business model). A detailed explanation from planning to investment has been discussed. The local community is getting approximately 112,000 USD per year by selling the electricity, and 162-ton CO2 is estimated to decrease yearly, which will support the achievement of SDGs. Finally, installing this kind of SHP in remote areas will provide managerial skills to the local community directly, plant operation knowledge, and education to local students. Local communities learn the problem-solving skills, which lead them to solve the local problem on a community level by themselves. Full article
Show Figures

Figure 1

Article
The Potential Use of Fly Ash from the Pulp and Paper Industry as Thermochemical Energy and CO2 Storage Material
Energies 2021, 14(11), 3348; https://0-doi-org.brum.beds.ac.uk/10.3390/en14113348 - 07 Jun 2021
Viewed by 446
Abstract
As a part of our research in the field of thermochemical energy storage, this study aims to investigate the potential of three fly ash samples derived from the fluidized bed reactors of three different pulp and paper plants in Austria for their use [...] Read more.
As a part of our research in the field of thermochemical energy storage, this study aims to investigate the potential of three fly ash samples derived from the fluidized bed reactors of three different pulp and paper plants in Austria for their use as thermochemical energy (TCES) and CO2 storage materials. The selected samples were analyzed by different physical and chemical analytical techniques such as X-ray fluorescence spectroscopy (XRF), X-ray diffraction (XRD), particle size distribution (PSD), scanning electron microscopy (SEM), inductively coupled plasma atomic emission spectroscopy (ICP-OES), and simultaneous thermal analysis (STA) under different atmospheres (N2, CO2, and H2O/CO2). To evaluate the environmental impact, leaching tests were also performed. The amount of CaO as a promising candidate for TCES was verified by XRF analysis, which was in the range of 25–63% (w/w). XRD results indicate that the CaO lies as free lime (3–32%), calcite (21–29%), and silicate in all fly ash samples. The results of STA show that all fly ash samples could fulfill the requirements for TCES (i.e., charging and discharging). A cycling stability test of three cycles was demonstrated for all samples which indicates a reduction of conversion in the first three reaction cycles. The energy content of the examined samples was up to 504 kJ/kg according to the STA results. More energy (~1090 kJ/kg) in the first discharging step in the CO2/H2O atmosphere could be released through two kinds of fly ash samples due to the already existing free lime (CaO) in those samples. The CO2 storage capacity of these fly ash samples ranged between 18 and 110 kg per ton of fly ash, based on the direct and dry method. The leaching tests showed that all heavy metals were below the limit values of the Austrian landfill ordinance. It is viable to say that the valorization of fly ash from the pulp and paper industries via TCES and CO2 storage is plausible. However, further investigations such as cycling stability improvement, system integration and a life cycle assessment (LCA) still need to be conducted. Full article
(This article belongs to the Special Issue Development in Thermochemical Energy Storage)
Show Figures

Figure 1

Article
Performance Analysis of TiO2-Modified Co/MgAl2O4 Catalyst for Dry Reforming of Methane in a Fixed Bed Reactor for Syngas (H2, CO) Production
Energies 2021, 14(11), 3347; https://0-doi-org.brum.beds.ac.uk/10.3390/en14113347 - 07 Jun 2021
Viewed by 609
Abstract
Co/TiO2–MgAl2O4 was investigated in a fixed bed reactor for the dry reforming of methane (DRM) process. Co/TiO2–MgAl2O4 was prepared by modified co-precipitation, followed by the hydrothermal method. The active metal Co was loaded [...] Read more.
Co/TiO2–MgAl2O4 was investigated in a fixed bed reactor for the dry reforming of methane (DRM) process. Co/TiO2–MgAl2O4 was prepared by modified co-precipitation, followed by the hydrothermal method. The active metal Co was loaded via the wetness impregnation method. The prepared catalyst was characterized by XRD, SEM, TGA, and FTIR. The performance of Co/TiO2–MgAl2O4 for the DRM process was investigated in a reactor with a temperature of 750 °C, a feed ratio (CO2/CH4) of 1, a catalyst loading of 0.5 g, and a feed flow rate of 20 mL min−1. The effect of support interaction with metal and the composite were studied for catalytic activity, the composite showing significantly improved results. Moreover, among the tested Co loadings, 5 wt% Co over the TiO2–MgAl2O4 composite shows the best catalytic performance. The 5%Co/TiO2–MgAl2O4 improved the CH4 and CO2 conversion by up to 70% and 80%, respectively, while the selectivity of H2 and CO improved to 43% and 46.5%, respectively. The achieved H2/CO ratio of 0.9 was due to the excess amount of CO produced because of the higher conversion rate of CO2 and the surface carbon reaction with oxygen species. Furthermore, in a time on stream (TOS) test, the catalyst exhibited 75 h of stability with significant catalytic activity. Catalyst potential lies in catalyst stability and performance results, thus encouraging the further investigation and use of the catalyst for the long-run DRM process. Full article
(This article belongs to the Collection Feature Papers in Sustainable Energy)
Show Figures

Graphical abstract

Article
Optimization of IEDs Position in MV Smart Grids through Integer Linear Programming
Energies 2021, 14(11), 3346; https://0-doi-org.brum.beds.ac.uk/10.3390/en14113346 - 07 Jun 2021
Viewed by 506
Abstract
In the paper, an analytical method for determining the optimal positioning of intelligent electronic devices in medium voltage grids is proposed. Intelligent electronic devices are automated devices able to communicate one with each other and command the circuit breaker in order to localize [...] Read more.
In the paper, an analytical method for determining the optimal positioning of intelligent electronic devices in medium voltage grids is proposed. Intelligent electronic devices are automated devices able to communicate one with each other and command the circuit breaker in order to localize and isolate a line fault as fast as possible. However, the number of intelligent electronic devices to install has to be limited, due to the relevant installation costs and the reduction in the transmission bandwidth caused by the increased number of exchanged messages. So, the electrical distributor has to carefully detect the nodes of the grid where the intelligent electronic devices have to be installed. The authors propose a method based on integer linear programming, which, given the number of intelligent electronic devices to install, finds their optimal position, i.e., the one that minimizes the penalties associated with the power down experienced by customers. In order to highlight the offered advantages in terms of computational effort, the proposed approach has been assessed with a real medium voltage grid. Full article
(This article belongs to the Topic Innovative Techniques for Smart Grids)
Show Figures

Figure 1

Article
Modeling Electricity Price and Quantity Uncertainty: An Application for Hedging with Forward Contracts
Energies 2021, 14(11), 3345; https://0-doi-org.brum.beds.ac.uk/10.3390/en14113345 - 07 Jun 2021
Viewed by 495
Abstract
Energy transactions in liberalized markets are subject to price and quantity uncertainty. This paper considers the spot price and energy generation to follow a bivariate semi-nonparametric distribution defined in terms of the Gram–Charlier expansion. This distribution allows us to jointly model not only [...] Read more.
Energy transactions in liberalized markets are subject to price and quantity uncertainty. This paper considers the spot price and energy generation to follow a bivariate semi-nonparametric distribution defined in terms of the Gram–Charlier expansion. This distribution allows us to jointly model not only mean, variance, and correlation but also skewness, kurtosis, and higher-order moments. Based on this model, we propose a static hedging strategy for electricity generators that participate in a competitive market where hedging is carried out through forward contracts that include a risk premium in their valuation. For this purpose, we use Monte Carlo simulation and consider information from the Colombian electricity market as the case study. The results show that the volume of energy to be sold under long-term contracts depends on each electricity generator and the risk assessment made by the market in the forward risk premium. The conditions of skewness, kurtosis, and correlation, as well as the type of the employed risk indicator, affect the hedging strategy that each electricity generator should implement. A positive correlation between the spot price and energy production tends to increase the hedge ratio; meanwhile, negative correlation tends to reduce it. The increase of forward risk premium, on the other hand, reduces the hedge ratio. Full article
(This article belongs to the Collection Featured Papers in Electrical Power and Energy System)
Show Figures

Figure 1

Article
Unified Power Converter Based on a Dual-Stator Permanent Magnet Synchronous Machine for Motor Drive and Battery Charging of Electric Vehicles
Energies 2021, 14(11), 3344; https://0-doi-org.brum.beds.ac.uk/10.3390/en14113344 - 07 Jun 2021
Viewed by 446
Abstract
An electric vehicle (EV) usually has two main power converters, namely one for the motor drive system and another for the battery-charging system. Considering the similarities between both converters, a new unified power converter for motor drive and battery charging of EVs is [...] Read more.
An electric vehicle (EV) usually has two main power converters, namely one for the motor drive system and another for the battery-charging system. Considering the similarities between both converters, a new unified power converter for motor drive and battery charging of EVs is propounded in this paper. By using a single unified power converter, the cost, volume, and weight of the power electronics are reduced, thus also making possible a reduction in the final price of the EV. Moreover, the proposed unified power converter has the capability of bidirectional power flow. During operation in traction mode, the unified power converter controls motor driving and regenerative braking. Additionally, during operation in battery-charging mode, with the EV plugged into the electrical power grid, the unified power converter controls the power flow for slow or fast battery charging (grid-to-vehicle (G2V) mode), or for discharging of the batteries (vehicle-to-grid (V2G) mode). Specifically, this paper presents computer simulations and experimental validations for operation in both motor-driving and slow battery-charging mode (in G2V and V2G modes). It is demonstrated that the field-oriented control used in the traction system presents good performance for different values of mechanical load and that the battery-charging system operates with high levels of power quality, both in G2V and in V2G mode. Full article
Show Figures

Figure 1

Communication
Extending the Coverage of the Trust–Acceptability Model: The Negative Effect of Trust in Government on Nuclear Power Acceptance in South Korea under a Nuclear Phase-Out Policy
Energies 2021, 14(11), 3343; https://0-doi-org.brum.beds.ac.uk/10.3390/en14113343 - 07 Jun 2021
Viewed by 434
Abstract
This article extends the coverage of the trust–acceptability model to a new situation of nuclear phase-out by investigating the effect of trust on the public acceptance of nuclear power, with South Korea as the research setting. Through the structural equation modeling of a [...] Read more.
This article extends the coverage of the trust–acceptability model to a new situation of nuclear phase-out by investigating the effect of trust on the public acceptance of nuclear power, with South Korea as the research setting. Through the structural equation modeling of a nationwide survey dataset from South Korea, we examined the effects of the public’s trust in the various actors related to nuclear power on their perceptions of the benefits and risks of nuclear power and their acceptance of nuclear power. Contrary to previous studies’ findings, in South Korea, under a nuclear phase-out policy by the government, trust in government revealed a negative impact on the public acceptance of nuclear power. Trust in environmental non-governmental groups also showed a negative effect on nuclear power acceptance. In contrast, trust in nuclear energy authority and trust in nuclear academia both had positive effects. In all cases, the effect of a trust variable on nuclear power acceptance was at least partially accounted for by the trust’s indirect effects through benefit perception and risk perception. These findings strengthen the external validity of the trust–acceptability model and provide implications for both researchers and practitioners. Full article
(This article belongs to the Section Nuclear Energy)
Show Figures

Graphical abstract

Article
CFD Simulations for Performance Enhancement of a Solar Chimney Power Plant (SCPP) and Techno-Economic Feasibility for a 5 MW SCPP in an Indian Context
Energies 2021, 14(11), 3342; https://0-doi-org.brum.beds.ac.uk/10.3390/en14113342 - 07 Jun 2021
Viewed by 414
Abstract
The use of solar energy for power generation using the innovative solar chimney concept has been explored by many researchers mostly with the help of analytical models as well as CFD simulations while experimental studies for a pilot and bench scale facilities have [...] Read more.
The use of solar energy for power generation using the innovative solar chimney concept has been explored by many researchers mostly with the help of analytical models as well as CFD simulations while experimental studies for a pilot and bench scale facilities have been carried out. The efficiencies of these chimneys, however, are less than 1% (~0.07% for 50 kW pilot plant similar to Manzanares plant in Spain). In the present study, an effort has been made to make modifications in the chimney design to improve the efficiency of the chimney in terms of power generation. CFD simulations have been carried out for this modified design and the efficiency is seen to improve to 0.12% for a 50 kW chimney. Furthermore, a techno-economic feasibility analysis has been carried out for a conventional 5 MW solar power plant which can be installed on the western part of India, which receives good solar irradiation throughout the year. Two cases with and without government subsidies have been considered. It is observed that a high rate of return (~20.4%) is obtained for a selling price of electricity of Rs 5 per kWh with government subsidy, while a rate of return of ~19% is obtained for Rs 10 per kWh without government subsidy. Full article
(This article belongs to the Special Issue Recent Advances in Solar Power Plants)
Show Figures

Figure 1

Article
Particulate Matter Reduction in Residual Biomass Combustion
Energies 2021, 14(11), 3341; https://0-doi-org.brum.beds.ac.uk/10.3390/en14113341 - 07 Jun 2021
Viewed by 418
Abstract
Counteracting emissions of particulate matter (PM) is an increasingly important goal in sustainable biomass combustion. This work includes a novel approach to investigate the PM emissions, originating from residual biomass combustion, at different combustion conditions in a lab-scale grate-fired furnace and includes in [...] Read more.
Counteracting emissions of particulate matter (PM) is an increasingly important goal in sustainable biomass combustion. This work includes a novel approach to investigate the PM emissions, originating from residual biomass combustion, at different combustion conditions in a lab-scale grate-fired furnace and includes in situ PM measurements by using on-line sensors. The interior furnace design allows installation of baffles to suppress the emissions by controlling the residence time. Moreover, the two-thermocouple method is used to measure the true gas temperature, and an on-line spatially resolved PM measurement method is developed to study the evolution of the PM concentration throughout the furnace for different experimental conditions thereby allowing accurate in-situ measurement of the PM reactivity. Experimental results and computational fluid dynamics (CFD) analyses are utilized in the current work to develop a kinetic model for reduction of particulate matter emissions in biomass combustion. The discrete particle model (DPM) is utilized in CFD analysis to improve the understanding of the particle temperature and residence time distribution which are difficult to quantify experimentally. By combining the experimental measurements of real soot formed during biomass combustion and information from the CFD analyses, a predictive kinetic model for PM10 reduction in biomass combustion is successfully developed. Full article
(This article belongs to the Special Issue Residual Biomass Conversion to Bioenergy)
Show Figures

Figure 1

Article
Electrical and Mechanical Characteristics of a High-Speed Motor for Electric Turbochargers in Relation to Eccentricity
Energies 2021, 14(11), 3340; https://0-doi-org.brum.beds.ac.uk/10.3390/en14113340 - 07 Jun 2021
Cited by 1 | Viewed by 440
Abstract
As the demand for eco-friendly, high-efficiency transportation technologies increase due to climate change, a high-speed electric motor, a key component of an electric turbocharger, has been developed that can reduce emissions and increase fuel efficiency. Korea Electrotechnology Research Institute with Keyyang Precision Co., [...] Read more.
As the demand for eco-friendly, high-efficiency transportation technologies increase due to climate change, a high-speed electric motor, a key component of an electric turbocharger, has been developed that can reduce emissions and increase fuel efficiency. Korea Electrotechnology Research Institute with Keyyang Precision Co., Ltd., developed a high-speed surface-mounted permanent magnet synchronous motor. It operates at a power of 3 kW at 100,000 rpm and is intended to fit 1600 cc diesel vehicles. In this paper, the electrical and mechanical characteristics of the high-speed motor were reviewed in consideration of the effect of eccentricity among the various causes that affect vibration. It was confirmed that eccentricity affected the distribution of the electromagnetic force and inductance of the winding due to the uneven air-gap. Additional vibration was generated at the half of pole passing frequency (1666.67 Hz). Diagnosing the presence or absence of eccentricity when driving a motor takes a great deal of time and cost because the load is separated or the motor is diagnosed through disassembly and measurement. The characteristics of eccentricity identified in this paper can be checked using a relatively simple method when diagnosing the presence or absence of actual eccentricity. Full article
(This article belongs to the Special Issue Advances in Motor and Drive)
Show Figures

Figure 1

Article
A Sequential Optimization-Simulation Approach for Planning the Transition to the Low Carbon Freight System with Case Study in the North Island of New Zealand
Energies 2021, 14(11), 3339; https://0-doi-org.brum.beds.ac.uk/10.3390/en14113339 - 06 Jun 2021
Viewed by 548
Abstract
Freight movement has always been, and always will be an essential activity. Freight transport is one of the most challenging sectors to transition to net-zero carbon. Traffic assignment, mode allocation, network planning, hub location, train scheduling and terminal design problem-solving have previously been [...] Read more.
Freight movement has always been, and always will be an essential activity. Freight transport is one of the most challenging sectors to transition to net-zero carbon. Traffic assignment, mode allocation, network planning, hub location, train scheduling and terminal design problem-solving have previously been used to address cost and operation efficiencies. In this study, the interdisciplinary transition innovation, management and engineering (InTIME) methodology was used for the conceptualization, redesign and redevelopment of the existing freight systems to achieve a downshift in fossil energy consumption. The fourth step of the InTIME methodology is the conceptualization of a long-term future intermodal transport system that can serve the current freight task. The novelty of our approach stands in considering the full range of freight supply chain factors as a whole, using an optimization-simulation approach as if we were designing the low-carbon system of 2121. For the optimization, ArcGIS software was used to set up a multimodal network model. Route and mode selection were delivered through the optimization of energy use within the network. Complementarily, Anylogic software was used to build a GIS-based discrete event simulation model and set up different experiments to enhance the solution offered by the network analysis. The results outline the resources needed (i.e., number of railway tracks, train speed, size of railyards, number of cranes and forklifts at terminals) to serve the freight task. The results can be backcast to reveal the most efficient investments in the near term. In the case of New Zealand’s North Island, the implementation of strategic terminals, with corresponding handling resources and railyards, could deliver 47% emissions reduction from the sector by 2030, ahead of longer lead-time upgrades like electrification of the railway infrastructure. Full article
(This article belongs to the Special Issue Energy Transition Engineering 2021)
Show Figures

Figure 1

Article
Rural Electrification Pathways: An Implementation of LEAP and GIS Tools in Mali
Energies 2021, 14(11), 3338; https://0-doi-org.brum.beds.ac.uk/10.3390/en14113338 - 06 Jun 2021
Viewed by 590
Abstract
Remote rural populations do not often have the luxury of viable multisource electricity generation systems. Considering fossil fuels for remote populated areas is not often a viable option due to the fuel transportation costs and the population’s socioeconomic status. Extending the grid is [...] Read more.
Remote rural populations do not often have the luxury of viable multisource electricity generation systems. Considering fossil fuels for remote populated areas is not often a viable option due to the fuel transportation costs and the population’s socioeconomic status. Extending the grid is often economically prohibitive. This paper proposes possible ways in which Mali could increase the rate of population with access to electricity by 2050 using Low Emission Analysis Platform (LEAP) and geographical information tools. The current energy situation is assessed, and multiple demand and supply scenarios are created to find the most viable option in environmental and economic dimensions. A minimum of 50% reduction of biomass consumption in the residential sector and a maximum of 71% was achieved through the combination of grid extension and decentralized solar PV. Solar PV becomes the preferable option when enough time for the effects of electricity on income is given. When these effects are not present, solar PV is still a better option, as the amount of biomass replaced with electricity is reduced. Full article
(This article belongs to the Special Issue Rural Renewable Energy Utilization and Electrification)
Show Figures

Graphical abstract

Article
Stakeholder Expectation of Corporate Social Responsibility Practices: A Case Study of PWiK Rybnik, Poland
Energies 2021, 14(11), 3337; https://0-doi-org.brum.beds.ac.uk/10.3390/en14113337 - 06 Jun 2021
Cited by 1 | Viewed by 631
Abstract
Practices of corporate social responsibility (CSR), especially in organizations providing key services, related to the supply of fuel, water and energy, are extremely important from the point of view of identifying stakeholders with the functioning of enterprises in line with the principles of [...] Read more.
Practices of corporate social responsibility (CSR), especially in organizations providing key services, related to the supply of fuel, water and energy, are extremely important from the point of view of identifying stakeholders with the functioning of enterprises in line with the principles of a closed loop economy. The article discusses the origins and evolution of the concept of corporate social responsibility, with particular emphasis on the water supply and sewage industry. The research problem was the perception and expectations of stakeholders toward prosocial activities of PWiK Rybnik (Sewage and Water Supply Ltd. Rybnik). The hypothesis assumed in the study was that the external stakeholders of PWIK Rybnik positively assess the company’s involvement in the tasks carried out as part of corporate social responsibility, they notice the involvement in educational activities and additional initiatives of PWIK that improve the quality of life of its inhabitants. For the purpose of this study, a quantitative method was used. For the purpose of the survey, the authors’ questionnaire “Survey of customers’ opinions on the activities undertaken by PWiK Rybnik” was created. The surveys conducted confirmed the hypothesis that the external stakeholders of PWIK Rybnik positively assess the company’s involvement in the tasks performed as part of corporate social responsibility; they notice the involvement in educational activities and additional initiatives of PWIK that improve the quality of life of its inhabitants. The results of the research made it possible to formulate guidelines for the operation of water supply and sewage companies in accordance with corporate social responsibility in the light of the opinions of their stakeholders. Full article
(This article belongs to the Special Issue Integrated Approaches for Enterprise Sustainability)
Show Figures

Figure 1

Article
Use of Acidithiobacillus thiooxidans and Acidithiobacillus ferrooxidans in the Recovery of Heavy Metals from Landfill Leachates
Energies 2021, 14(11), 3336; https://0-doi-org.brum.beds.ac.uk/10.3390/en14113336 - 06 Jun 2021
Viewed by 510
Abstract
Among the methods used to remove metals and their compounds from landfill leachates with low application costs and high efficiency are bioleaching and biosorption. The most effective bacteria used in the metal removal process are Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans. The aim [...] Read more.
Among the methods used to remove metals and their compounds from landfill leachates with low application costs and high efficiency are bioleaching and biosorption. The most effective bacteria used in the metal removal process are Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans. The aim of the study was to determine the usefulness of the A. ferrooxidans and A. thiooxidans population in removing heavy metals from landfill leachate. In addition, development opportunities for bacterial population using landfill leachate as growth medium were identified. The substrate for the research was the raw leachate before the reverse osmosis process. In order to increase the efficiency of trace elements removal and recovery from leachate, variable combinations have been used which differ by the addition of sulfuric acid, A. ferrooxidans culture, A. thiooxidans culture, mixed culture containing populations of both bacteria, and elemental sulfur. Based on the research, it was found that the removal of heavy metals from leachate was a selective process. High bioleaching efficiency, from 80% to 90%, was obtained for all metals for which the sample acidification or sulfur addition was used. The simultaneous combination of both these additives turned out to be the most advantageous. The A. thiooxidans culture was the most effective in bioleaching reverse osmosis effluents. For the A. ferrooxidans culture used, much lower efficiencies were obtained, while by contrast, the use of mixed culture of two bacterium species had no significant effect. Full article
(This article belongs to the Special Issue Energy and Matter Recovery from Organic Waste Processing and Reuse)
Show Figures

Figure 1

Article
Fourth-Order Comprehensive Adjoint Sensitivity Analysis (4th-CASAM) of Response-Coupled Linear Forward/Adjoint Systems: I. Theoretical Framework
Energies 2021, 14(11), 3335; https://0-doi-org.brum.beds.ac.uk/10.3390/en14113335 - 06 Jun 2021
Viewed by 387
Abstract
The most general quantities of interest (called “responses”) produced by the computational model of a linear physical system can depend on both the forward and adjoint state functions that describe the respective system. This work presents the Fourth-Order Comprehensive Adjoint Sensitivity Analysis Methodology [...] Read more.
The most general quantities of interest (called “responses”) produced by the computational model of a linear physical system can depend on both the forward and adjoint state functions that describe the respective system. This work presents the Fourth-Order Comprehensive Adjoint Sensitivity Analysis Methodology (4th-CASAM) for linear systems, which enables the efficient computation of the exact expressions of the 1st-, 2nd-, 3rd- and 4th-order sensitivities of a generic system response, which can depend on both the forward and adjoint state functions, with respect to all of the parameters underlying the respective forward/adjoint systems. Among the best known such system responses are various Lagrangians, including the Schwinger and Roussopoulos functionals, for analyzing ratios of reaction rates, the Rayleigh quotient for analyzing eigenvalues and/or separation constants, etc., which require the simultaneous consideration of both the forward and adjoint systems when computing them and/or their sensitivities (i.e., functional derivatives) with respect to the model parameters. Evidently, such responses encompass, as particular cases, responses that may depend just on the forward or just on the adjoint state functions pertaining to the linear system under consideration. This work also compares the CPU-times needed by the 4th-CASAM versus other deterministic methods (e.g., finite-difference schemes) for computing response sensitivities These comparisons underscore the fact that the 4th-CASAM is the only practically implementable methodology for obtaining and subsequently computing the exact expressions (i.e., free of methodologically-introduced approximations) of the 1st-, 2nd, 3rd- and 4th-order sensitivities (i.e., functional derivatives) of responses to system parameters, for coupled forward/adjoint linear systems. By enabling the practical computation of any and all of the 1st-, 2nd, 3rd- and 4th-order response sensitivities to model parameters, the 4th-CASAM makes it possible to compare the relative values of the sensitivities of various order, in order to assess which sensitivities are important and which may actually be neglected, thus enabling future investigations of the convergence of the (multivariate) Taylor series expansion of the response in terms of parameter variations, as well as investigating the range of validity of other important quantities (e.g., response variances/covariance, skewness, kurtosis, etc.) that are derived from Taylor-expansion of the response as a function of the model’s parameters. The 4th-CASAM presented in this work provides the basis for significant future advances towards overcoming the “curse of dimensionality” in sensitivity analysis, uncertainty quantification and predictive modeling. Full article
Article
Deep Convolutional Feature-Based Probabilistic SVDD Method for Monitoring Incipient Faults of Batch Process
Energies 2021, 14(11), 3334; https://0-doi-org.brum.beds.ac.uk/10.3390/en14113334 - 06 Jun 2021
Viewed by 477
Abstract
Support vector data description (SVDD) has been widely applied to batch process fault detection. However, it often performs poorly, especially when incipient faults occur, because it only considers the shallow data feature and omits the probabilistic information of features. In order to provide [...] Read more.
Support vector data description (SVDD) has been widely applied to batch process fault detection. However, it often performs poorly, especially when incipient faults occur, because it only considers the shallow data feature and omits the probabilistic information of features. In order to provide better monitoring performance on incipient faults in batch processes, an improved SVDD method, called deep probabilistic SVDD (DPSVDD), is proposed in this work by integrating the convolutional autoencoder and the probability-related monitoring indices. For mining the hidden data features effectively, a deep convolutional features extraction network is designed by a convolutional autoencoder, where the encoder outputs and the reconstruction errors are used as the monitor features. Furthermore, the probability distribution changes of these features are evaluated by the Kullback-Leibler (KL) divergence so that the probability-related monitoring indices are developed for indicating the process status. The applications to the benchmark penicillin fermentation process demonstrate that the proposed method has a better monitoring performance on the incipient faults in comparison to the traditional SVDD methods. Full article
Show Figures

Figure 1

Article
Thermal and Flow Simulation of Concentric Annular Heat Pipe with Symmetric or Asymmetric Condenser
Energies 2021, 14(11), 3333; https://0-doi-org.brum.beds.ac.uk/10.3390/en14113333 - 06 Jun 2021
Viewed by 471
Abstract
The current research work describes the flow and thermal analysis inside the circular flow region of an annular heat pipe with a working fluid, using computational fluid dynamics (CFD) simulation. A two-phase flow involving simultaneous evaporation and condensation phenomena in a concentric annular [...] Read more.
The current research work describes the flow and thermal analysis inside the circular flow region of an annular heat pipe with a working fluid, using computational fluid dynamics (CFD) simulation. A two-phase flow involving simultaneous evaporation and condensation phenomena in a concentric annular heat pipe (CAHP) is modeled. To simulate the interaction between these phases, the volume of fluid (VOF) technique is used. The temperature profile predicted using computational fluid dynamics (CFD) in the CAHP was compared with previously obtained experimental results. Two-dimensional and three-dimensional simulations were carried out, in order to verify the usefulness of 3D modeling. Our goal was to compute the flow characteristics, temperature distribution, and velocity field inside the CAHP. Depending on the shape of the annular heat pipe, the thermal performance can be improved through the optimal design of components, such as the inner width of the annular heat pipe, the location of the condensation part, and the amount of working fluid. To evaluate the thermal performance of a CAHP, a numerical simulation of a 50 mm long stainless steel CAHP (1.1 and 1.3 in diameter ratio and fixed inner tube diameter (78 mm)) was done, which was identical to the experimental system. In the simulated analysis results, similar results to the experiment were obtained, and it was confirmed that the heat dissipation was higher than that of the existing conventional heat pipe, where the heat transfer performance was improved when the asymmetric area was cooled. Moreover, the simulation results were validated using the experimental results. The 3-D simulation shows good agreement with the experimental results to a reasonable degree. Full article
(This article belongs to the Special Issue Advances in Heat Transfer Enhancement)
Show Figures

Graphical abstract

Article
Design and Large Temperature Jump Testing of a Modular Finned-Tube Carbon–Ammonia Adsorption Generator for Gas-Fired Heat Pumps
Energies 2021, 14(11), 3332; https://0-doi-org.brum.beds.ac.uk/10.3390/en14113332 - 05 Jun 2021
Viewed by 514
Abstract
Gas-fired heat pumps are a potential replacement for condensing boilers, utilizing fossil-fuel resources more efficiently and reducing the amount of biogas or hydrogen required in sustainable gas grids. However, their adoption has been limited due to their large size and high capital cost, [...] Read more.
Gas-fired heat pumps are a potential replacement for condensing boilers, utilizing fossil-fuel resources more efficiently and reducing the amount of biogas or hydrogen required in sustainable gas grids. However, their adoption has been limited due to their large size and high capital cost, resulting in long payback times. For adsorption-based heat pumps, the major development challenge is to maximize the rate of heat transfer to the adsorbent, whilst minimizing the thermal mass. This work develops a modular finned-tube carbon–ammonia adsorption generator that incorporates the adsorbent in highly compacted 3-mm layers between aluminum fins. Manufacturing techniques that are amenable to low cost and high-volume production were developed. The module was tested using the large temperature jump (LTJ) method and achieved a time constant for adsorption and desorption of 50 s. The computational model predicted that if incorporated into two adsorption generators of 6 L volume each, they could be used to construct a gas-fired heat pump with a 10 kW heat output and a gas utilization efficiency (GUE, the ratio of useful heat output to higher calorific value of gas used) of 1.2. Full article
(This article belongs to the Special Issue Advances on Adsorption Heat Pumps, Stores and Systems)
Show Figures

Graphical abstract

Article
Analysis of Restructuring the Mexican Electricity Sector to Operate in a Wholesale Energy Market
Energies 2021, 14(11), 3331; https://0-doi-org.brum.beds.ac.uk/10.3390/en14113331 - 05 Jun 2021
Viewed by 514
Abstract
This paper analyzes the energy reform that has taken place in Mexico since 2013, driven by steady growth in energy demand and insufficient economic resources. The relevant points in the restructuring process are discussed, shedding light on the impact of recent governmental actions [...] Read more.
This paper analyzes the energy reform that has taken place in Mexico since 2013, driven by steady growth in energy demand and insufficient economic resources. The relevant points in the restructuring process are discussed, shedding light on the impact of recent governmental actions not aligned with the original spirit of the law. This research uses a framework and fundamentals of a well-organized structural process called the textbook model, making a comparative analysis of Mexican reform. It proceeds by presenting the Mexican Electrical System in numbers and how it is affected by the present government’s restructuring process providing positive and negative impacts of several implementations. The main objectives of restructuring were carried out to attract private investment and increase the reliability and efficiency of the system. During the first four years, the reform has attracted investment, in diminishing form in generation but not in transmission and distribution. Therefore, the main reason for this is explained and a brief analysis and the roots of these failures are presented. It is shown that recent political decisions tend to keep the system operator and regulatory agencies under Federal Government control so that it is acting against the main objectives of the original reform. Finally, a summary of the deviation of the reality from the existing law is outlined. Full article
(This article belongs to the Section Energy Economics and Policy)
Show Figures

Graphical abstract

Previous Issue
Next Issue
Back to TopTop