Energies

12 pages, 3650 KiB

Open AccessArticle

Enhanced OH⁻ Conductivity for Fuel Cells with Anion Exchange Membranes, Based on Modified Terpolymer Polyketone and Surface Functionalized Silica

by Narges Ataollahi, Eleonora Tomasino, Oscar Cotini and Rosa Di Maggio

Energies 2022, 15(5), 1953; https://doi.org/10.3390/en15051953 - 07 Mar 2022

Cited by 5 | Viewed by 2503

Abstract

Several modified terpolymer polyketones (MPK) with N-substituted pyrrole moieties in the main chain and quaternized amine in the side group were synthesized for use as anion exchange membranes for fuel cells. The moieties were carried by SiO₂ nanoparticles through surface functionalization (Si–N), [...] Read more.

Several modified terpolymer polyketones (MPK) with N-substituted pyrrole moieties in the main chain and quaternized amine in the side group were synthesized for use as anion exchange membranes for fuel cells. The moieties were carried by SiO₂ nanoparticles through surface functionalization (Si–N), which were added to the membranes to enhance their overall properties. On increasing the amount of modified silica from 10% to 60% wt/of MPK, there was an increase in Si–N and a corresponding threefold increase in the hydroxide conductivity of the membrane. The MPK–SiN (60%) exhibited a superior ionic conductivity of 1.05 × 10⁻¹ S.cm⁻¹ at 120 °C, a high mechanical stability, with a tensile strength of 46 MPa at 80 °C. In strongly alkaline conditions (1 M KOH, 216 h at 80 °C), the membranes maintained about 70% of the conductivity measured in a usual environment. Fuel cell performance at 80 °C showed a peak power density of 133 mW·cm⁻², indicating that using surface-functionalized SiO₂ is a simple and effective way to enhance the overall performance of anion exchange membranes in fuel cell applications. Full article

(This article belongs to the Section D2: Electrochem: Batteries, Fuel Cells, Capacitors)

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22 pages, 5267 KiB

Open AccessArticle

A Novel Circulating Current Suppression for Paralleled Current Source Converter Based on Virtual Impedance Concept

by Xiao Fu, Huaibao Wang, Xiaoqiang Guo, Changli Shi, Dongqiang Jia, Chao Chen and Josep M. Guerrero

Energies 2022, 15(5), 1952; https://doi.org/10.3390/en15051952 - 07 Mar 2022

Cited by 5 | Viewed by 2185

Abstract

The circulating current is one of the important issues for parallel converters. It affects the system stable operation and degrades the power quality. In order to reduce the circulating current of the parallel converter and reduce the harmonic pollution to the power grid, [...] Read more.

The circulating current is one of the important issues for parallel converters. It affects the system stable operation and degrades the power quality. In order to reduce the circulating current of the parallel converter and reduce the harmonic pollution to the power grid, a new circulating current suppression strategy is proposed for the parallel current source converter without any communication line. This strategy is able to realize the current sharing between parallel modules by changing the external characteristics of the parallel modules to thus suppress the circulating current among the parallel current source converters. The proposed control strategy adopts DC-side droop control and AC-side virtual impedance control. The DC-side droop control is used to generate the reference voltage of each parallel module, while the AC-side virtual impedance is used to the circulating current suppression. We performed a time domain test of the parallel converter, and the results show that the proposed control strategy reduced the RMS circulating current of the parallel converter by 50% and effectively reduced the grid-side current THD while ensuring the stable operation of the converter. The effectiveness of the proposed control strategy was, therefore, verified. Full article

(This article belongs to the Special Issue Modeling, Control and Design of Power Electronics Converters)

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23 pages, 11978 KiB

Open AccessArticle

Condition Monitoring of Wind Turbine Main Bearing Based on Multivariate Time Series Forecasting

by Xiaocong Xiao, Jianxun Liu, Deshun Liu, Yufei Tang and Fan Zhang

Energies 2022, 15(5), 1951; https://doi.org/10.3390/en15051951 - 07 Mar 2022

Cited by 13 | Viewed by 2488

Abstract

Condition monitoring and overheating warnings of the main bearing of large-scale wind turbines (WT) plays an important role in enhancing their dependability and reducing operating and maintenance (O&M) costs. The temperature parameter of the main bearing is the key indicator to characterize the [...] Read more.

Condition monitoring and overheating warnings of the main bearing of large-scale wind turbines (WT) plays an important role in enhancing their dependability and reducing operating and maintenance (O&M) costs. The temperature parameter of the main bearing is the key indicator to characterize the normal or abnormal operating condition. Therefore, forecasting the trend of temperature change is critical for overheating warnings. To achieve forecasting with high accuracy, this paper proposes a novel model for the WT main bearing, named stacked long-short-term memory with multi-layer perceptron (SLSTM-MLP) by utilizing supervisory control and data acquisition (SCADA) data. The model is mainly composed of multiple LSTM cells and a multi-layer perceptron regression layer. By combining condition parameters into a characteristic matrix, SLSTM can mine nonlinear, non-stationary dynamic feature relationships between temperature and its related variables. To evaluate the performance of the SLSTM-MLP model, experimental analysis was carried out from three aspects: different sample capacity sizes, different sampling time segments, and different sampling frequencies. Furthermore, the model’s capability of online fault detection was also carried out by simulation. The results of comparative studies and online fault simulation tests show that the proposed SLSTM-MLP has better performance for temperature forecasting of the main bearing of large-scale WTs. Full article

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30 pages, 14487 KiB

Open AccessArticle

Effective Volt/var Control for Low Voltage Grids with Bulk Loads

by Daniel-Leon Schultis

Energies 2022, 15(5), 1950; https://doi.org/10.3390/en15051950 - 07 Mar 2022

Cited by 2 | Viewed by 1865

Abstract

This paper investigates the voltage and reactive power control problem in low voltage grids with connected prosumers and bulk loads. The X(U) local control, which maintains the voltage at the feeders’ ends within a predefined band, and its combination with [...] Read more.

This paper investigates the voltage and reactive power control problem in low voltage grids with connected prosumers and bulk loads. The X(U) local control, which maintains the voltage at the feeders’ ends within a predefined band, and its combination with Q-Autarkic customer plants are the most effective and reliable strategies in grids with high prosumer share. However, these strategies may need adaptations to guarantee voltage limit compliance when bulk loads, such as electric vehicle parking garages and community-owned photovoltaic systems, are connected to the low voltage feeders. This paper extends the X(U) local control concept to involve bulk loads in Volt/var control and investigates the resulting load flows in different real low voltage grids. The results show that the extended control arrangement reliably removes all voltage limit violations by deteriorating the effectiveness of the original X(U) local control arrangement: reactive power flows and equipment loading within the low voltage grids are increased. Full article

(This article belongs to the Special Issue Prosperous Energy Communities: Prerequisites, Technical Solutions, and Perspectives)

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22 pages, 22114 KiB

Open AccessArticle

The Circulating Current Reduction Control Method for Asynchronous Carrier Phases of Parallel Connected Inverters

by Seung-Yong Lee and Jae-Jung Jung

Energies 2022, 15(5), 1949; https://doi.org/10.3390/en15051949 - 07 Mar 2022

Cited by 2 | Viewed by 2360

Abstract

Parallel operation of inverters is one of the most effective and representative ways to increase system capacity. However, zero-sequence circulating currents occur due to the practical deviations of components constituting individual inverters in case of parallel connected inverters in which a common direct [...] Read more.

Parallel operation of inverters is one of the most effective and representative ways to increase system capacity. However, zero-sequence circulating currents occur due to the practical deviations of components constituting individual inverters in case of parallel connected inverters in which a common direct current (DC) or alternating current (AC) bus is shared. In particular, circulating currents of the high-frequency component as well as those of the low-frequency component are generated due to the asynchronization of the carriers of individual inverters. In order to suppress the circulating currents as such, the phases of the carriers should be shifted as much as the phase errors between the carriers to compensate for the phase errors. A difficulty in this phase compensation control is that when there are several pulse-width modulation (PWM) carriers, it is impossible to identify the phase of each carrier. In this paper, to overcome the problem, a method to specify the position of one of the many carriers and control the carriers and compensate for phase errors based on the relevant phase was proposed. In addition, this paper includes the analysis of circulating currents generated in the case of carrier phase errors and proposes a method to identify carrier phase errors and compensate for the relevant errors. The proposed method was verified through simulations and experiments. Full article

(This article belongs to the Special Issue Advances in Power Electronics Technologies)

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14 pages, 2508 KiB

Open AccessArticle

Entrained Flow Plasma Gasification of Sewage Sludge–Proof-of-Concept and Fate of Inorganics

by Vishwajeet, Halina Pawlak-Kruczek, Marcin Baranowski, Michał Czerep, Artur Chorążyczewski, Krystian Krochmalny, Michał Ostrycharczyk, Paweł Ziółkowski, Paweł Madejski, Tadeusz Mączka, Amit Arora, Tomasz Hardy, Lukasz Niedzwiecki, Janusz Badur and Dariusz Mikielewicz

Energies 2022, 15(5), 1948; https://doi.org/10.3390/en15051948 - 07 Mar 2022

Cited by 18 | Viewed by 3001

Abstract

Sewage sludge is a residue of wastewater processing that is biologically active and consists of water, organic matter, including dead and living pathogens, polycyclic aromatic hydrocarbons, and heavy metals, as well as organic and inorganic pollutants. Landfilling is on the decline, giving way [...] Read more.

Sewage sludge is a residue of wastewater processing that is biologically active and consists of water, organic matter, including dead and living pathogens, polycyclic aromatic hydrocarbons, and heavy metals, as well as organic and inorganic pollutants. Landfilling is on the decline, giving way to more environmentally friendly utilisation routes. This paper presents the results of a two-stage gasification–vitrification system, using a prototype-entrained flow plasma-assisted gasification reactor along with ex situ plasma vitrification. The results show that the use of plasma has a considerable influence on the quality of gas, with a higher heating value of dry gas exceeding 7.5 MJ/m_N³, excluding nitrogen dilution. However, dilution from plasma gases becomes the main problem, giving a lower heating value of dry gas with the highest value being 5.36 MJ/m_N³ when dilution by nitrogen from plasma torches is taken into account. An analysis of the residues showed a very low leaching inclination of ex-situ vitrified residues. This suggests that such a system could be used to avoid the problem of landfilling significant amounts of ash from sewage sludge incineration by turning inorganic residues into a by-product that has potential use as a construction aggregate. Full article

(This article belongs to the Special Issue Control, Simulation, and Monitoring of Thermal Processes in Power Plants)

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24 pages, 7863 KiB

Open AccessArticle

Production Improvement via Optimization of Hydraulic Acid Fracturing Design Parameters in a Tight Carbonate Reservoir

by Rahman Ashena, Fred Aminzadeh and Amir Khoramchehr

Energies 2022, 15(5), 1947; https://doi.org/10.3390/en15051947 - 07 Mar 2022

Cited by 6 | Viewed by 2410

Abstract

Hydraulic fracturing can be utilized to extract trapped hydrocarbon where integrated fracture networks do not exist for sufficient production. In this work, design parameters of a hydraulic acid fracturing of a tight carbonate reservoir in the Middle East were optimized. The effect of [...] Read more.

Hydraulic fracturing can be utilized to extract trapped hydrocarbon where integrated fracture networks do not exist for sufficient production. In this work, design parameters of a hydraulic acid fracturing of a tight carbonate reservoir in the Middle East were optimized. The effect of optimized hydraulic fracturing on production performance and rate was investigated. Using the petrophysical well logs, formation integrity tests, core data the Mechanical Earth Model (MEM) of the tight carbonate reservoir was created, which resulted in rock mechanical properties and in-situ stresses. The other required parameters for fracturing design were either measured or found from empirical correlations. Following a candidate selection of suitable layers for fracturing, the input parameters were loaded in GOHFER software to design and optimize the fracturing job. Finally, the production forecast was performed and compared with current conditions. The injection parameters (flow rate, total volume, and number of stages) of the fracturing fluid (composed of guar and CMHPG and polymer with 15% HCL acid) were optimized to reach optimum resultant fracture geometry. Finally, optimized injection parameters were found at the injection flow rate of 18 barrels per minute, total injection volume of 90 K-gal, and three stages of injection. Using the optimal injection parameters, the optimized fracture geometrical sizes were determined: the fracture half-length (L_f): 148 m (486 ft), fracture height (H_f) of 64 m (210 ft) and fracture width (W_f) of 0.0962 in. Finally, the effect of this stimulation method on future production performance was investigated. The well production rate showed an increase from 840 STB/Day (before fracturing) to 1270 STB/Day (post fracturing). This study contributes to the practical design and optimization of hydraulic fracturing in the tight carbonate formation of the investigated oilfield and the other potential fields in the region. The results showed that this stimulation method can efficiently improve production performance from reservoir formation. Full article

(This article belongs to the Special Issue Hydraulic Fracturing: Progress and Challenges)

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18 pages, 4091 KiB

Open AccessArticle

Method for Reconfiguring Train Schedules Taking into Account the Global Reduction of Railway Energy Consumption

by Artur Kierzkowski and Szymon Haładyn

Energies 2022, 15(5), 1946; https://doi.org/10.3390/en15051946 - 07 Mar 2022

Cited by 6 | Viewed by 2168

Abstract

The paper aims to propose a method of reconfiguring the train timetable, taking into account minimising the globally consumed energy for traction purposes. This is a very important issue in the context of rising electricity prices, alarming climate changes and the “Fit for [...] Read more.

The paper aims to propose a method of reconfiguring the train timetable, taking into account minimising the globally consumed energy for traction purposes. This is a very important issue in the context of rising electricity prices, alarming climate changes and the “Fit for 55” policy introduced in Europe. Each unit of energy saved contributes to improving the state of the planet and reducing the negative human impact on it. In this paper, the authors propose a model that, when applied, will reconfigure the timetable in terms of energy intensity and, as a result, reduce the impact of railways on the burden on the environment. It is proposed to introduce an interdependence between trajectories of electrical train movement. This interdependence is to take place so that it is possible to efficiently transfer the energy recovered during the braking of one train to another train, moving on the same section of the railway line and at the same time (i.e., without using energy storage devices). The paper provides a physical background to the considerations—discussing the movement of electric trains in the context of their energy intensity and the possibility of energy recovery; presenting the possibility of interconnecting trains in such a way that the energy from a train that is being braked can be efficiently used by a train that is being accelerated; presenting a method for making the linkages between trains (in the form of an original algorithm resulting from the application of the Delphi method) and implementing them in the timetable. The timetable for the application of the method is real and was obtained from the railway operator in Poland, as a mathematical–physical model describing the trajectory and energy consumption of the original, after which the proposed timetable was verified by running simulations and comparing the energy consumption of the original and the proposed timetable. It turned out that it is possible to achieve a global total energy demand reduction of up to 398 MWh/year. This proves the validity of using the proposed algorithm at the timetabling stage and extending its implementation to the entire network. Furthermore the authors also recognise the tendency of the algorithm to return repeatable solutions, which has the side effect of creating a cyclic timetable. Its implementation in Poland has proved impossible for many years. The application of the proposed method could change this unfavourable situation. Full article

(This article belongs to the Special Issue Transportation Systems Modeling, Simulation and Analysis with Reference to Energy Supplying)

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18 pages, 2944 KiB

Open AccessArticle

Assumptions of the Energy Policy of the Country versus Investment Outlays Related to the Purchase of Alternative Fuels: Poland as a Case Study

by Maciej Ciołek, Izabela Emerling, Katarzyna Olejko, Beata Sadowska and Magdalena Wójcik-Jurkiewicz

Energies 2022, 15(5), 1945; https://doi.org/10.3390/en15051945 - 07 Mar 2022

Cited by 3 | Viewed by 3464

Abstract

Nowadays, the importance of activities for the protection of the environment is growing. This approach has a major impact on the current energy and mining policy in Poland. On the one hand, the energy policy has imposed several restrictions to which the Polish [...] Read more.

Nowadays, the importance of activities for the protection of the environment is growing. This approach has a major impact on the current energy and mining policy in Poland. On the one hand, the energy policy has imposed several restrictions to which the Polish economy will have to adapt; on the other, however, it raises great social opposition from professional groups that will be at risk of changing or losing their jobs and income, which implies extensive restructuring processes. These processes involve the decarbonisation of the economy and include, among others: sustainable production and consumption, sustainable municipal management and high quality of life in the city, waste management, sustainable transport, and energy management. The aim of the article is to indicate the importance of investment outlays and costs incurred when purchasing alternative fuels that would replace hard coal in Poland. It is part of the process of adjusting to the requirements of the new energy policy adopted by Poland as an EU member. In order to ensure energy security by abandoning coal mining, disproportionately high investment outlays for such a transformation would have to be incurred, as well as significant resources that would have to be allocated in the future to the purchase of alternative fuels. The result of the scenario methods used is the proposition of the proprietary RCAES index, which is to facilitate the transition from fossil fuels to alternative fuels, which the authors will fill in the gap existing in this area. Full article

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22 pages, 883 KiB

Open AccessArticle

Comparative Analysis of Hybrid Electric Architectures for Specialized Agricultural Tractors

by Francesco Mocera, Valerio Martini and Aurelio Somà

Energies 2022, 15(5), 1944; https://doi.org/10.3390/en15051944 - 07 Mar 2022

Cited by 15 | Viewed by 2896

Abstract

In this work, a comparative numerical analysis between the performance of a conventional specialized orchard tractor and those of three different hybrid electric tractor configurations is presented. The aim was to compare several powertrain configurations in the same working scenarios derived from field [...] Read more.

In this work, a comparative numerical analysis between the performance of a conventional specialized orchard tractor and those of three different hybrid electric tractor configurations is presented. The aim was to compare several powertrain configurations in the same working scenarios derived from field measurements. Peak power capabilities and endurance were numerically tested with specific load scenarios involving both transportation mission profiles and field activities with external implements powered through the power take off of the tractor. The proposed hybrid architectures were configured with the same battery-based energy storage system to perform the comparison with the same energy storage capabilities. Two parallel, two series and one electro-hydraulic hybrid configuration were modeled and tested through simulations. The parallel ones excelled in peak power performance, whereas the series configurations had the highest fuel savings. The electro-hydraulic configuration was proposed as an alternative able to allow for a downsized engine but also for the introduction of the Continuously Variable Transmission (CVT) functionality, which is always an interesting feature for such working machines. Full article

(This article belongs to the Special Issue Frontiers in Hybrid Vehicles)

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20 pages, 8041 KiB

Open AccessArticle

Static-Errorless Rotor Position Estimation Method Based on Linear Extended State Observer for IPMSM Sensorless Drives

by Feng Jiang, Fan Yang, Songjun Sun and Kai Yang

Energies 2022, 15(5), 1943; https://doi.org/10.3390/en15051943 - 07 Mar 2022

Cited by 1 | Viewed by 1682

Abstract

This article presents a static-errorless rotor position estimation method based on the linear extended state observer (LESO) for interior permanent magnet synchronous motor (IPMSM) drives. Two second-order LESOs are utilized to estimate the α-β axis back-EMFs. A third-order LESO is incorporated [...] Read more.

This article presents a static-errorless rotor position estimation method based on the linear extended state observer (LESO) for interior permanent magnet synchronous motor (IPMSM) drives. Two second-order LESOs are utilized to estimate the α-β axis back-EMFs. A third-order LESO is incorporated into the quadrature phase-locked loop (QPLL) to achieve a high robustness of position tracking against external disturbance. In addition, considering that the nonideal back-EMF will bring DC and harmonic fluctuation errors to the estimated position, an enhanced LESO-based QPLL with static-errorless rotor position estimation is proposed. On the one hand, the DC position esti mation error caused by the phase lag of the back-EMF estimator is analyzed and compensated. On the other hand, to suppress the position harmonic fluctuations induced from the nonsinusoidal back-EMFs, a second-order generalize integrator (SOGI) is embedded in the feedforward path of the LESO-based QPLL. The experimental results on the 1.0 kW IPMSM drive platform show that, compared to the conventional method, the proposed method can achieve better position estimation performance both in steady-state operation and in transient-state operation. Full article

(This article belongs to the Special Issue Active Disturbance Rejection Control in Power Electronics)

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21 pages, 5145 KiB

Open AccessArticle

Multi-Objective Optimal Integration of Solar Heating and Heat Storage into Existing Fossil Fuel-Based Heat and Power Production Systems

by Guangxuan Wang and Julien Blondeau

Energies 2022, 15(5), 1942; https://doi.org/10.3390/en15051942 - 07 Mar 2022

Cited by 1 | Viewed by 1967

Abstract

Increasing the share of Renewable energy sources in District Heating (DH) systems is of great importance to mitigate their CO₂ emissions. The combined integration of Solar Thermal Collectors (STC) and Thermal Energy Storage (TES) into existing Combined Heat and Power (CHP) systems [...] Read more.

Increasing the share of Renewable energy sources in District Heating (DH) systems is of great importance to mitigate their CO₂ emissions. The combined integration of Solar Thermal Collectors (STC) and Thermal Energy Storage (TES) into existing Combined Heat and Power (CHP) systems can be a very cost-effective way to do so. This paper aims at finding the optimal design of STC and TES systems integrated in existing CHP’s considering two distinct objectives: economic profitability and environmental impact. To do so, we developed a three-stage framework based on Pareto-optimal solutions generated by multi-objective optimization, a Technique for Order Preference by Similarity to Ideal Solution (TOPSIS)-entropy method to select the optimal solution, followed by the definition of final Operation strategy. We proposed relevant improvement of the state-of-the-art models used in similar analysis. We also applied the proposed methodology to the case of a representative, 12 MW_th CHP plant. Our results show that, while the addition of TES or STC alone results in limited performances and/or higher costs, both the cost and the CO₂ emissions can be reduced by integrating the optimal combination of STC and TES. For the selected, optimal solution, carbon emissions are reduced by 10%, while the Annual Total Cost (ATC) is reduced by 3%. It also improves the operational flexibility and the efficiency by peak load shaving, load valley filling and thus by decreasing the peak load boiler operation. Compared to the addition of STC alone, the use of TES results in an increased efficiency, from 88% to 92%. The optimal share of STC is then increased from 7% to 10%. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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12 pages, 4031 KiB

Open AccessArticle

Pyrolysis of Biomass Wastes into Carbon Materials

by Małgorzata Sieradzka, Cezary Kirczuk, Izabela Kalemba-Rec, Agata Mlonka-Mędrala and Aneta Magdziarz

Energies 2022, 15(5), 1941; https://doi.org/10.3390/en15051941 - 07 Mar 2022

Cited by 34 | Viewed by 4008

Abstract

This study presents the results of the biomass pyrolysis process focusing on biochar production and its potential energetic (as solid fuel) and material (as adsorbent) applications. Three kinds of biomass waste were investigated: wheat straw, spent coffee grounds, and brewery grains. The pyrolysis [...] Read more.

This study presents the results of the biomass pyrolysis process focusing on biochar production and its potential energetic (as solid fuel) and material (as adsorbent) applications. Three kinds of biomass waste were investigated: wheat straw, spent coffee grounds, and brewery grains. The pyrolysis process was carried out under nitrogen atmosphere at 400 and 500 °C (residence time of 20 min). A significant increase in the carbon content was observed in the biochars, e.g., from 45% to 73% (at 400 °C) and 77% (at 500 °C) for spent coffee grounds. In addition, the structure and morphology were investigated using scanning electron microscopy. Thermal properties were studied using a simultaneous thermal analysis under an oxidising atmosphere. The chemical activation was completed using KOH. The sorption properties of the obtained biochars were tested using chromium ion (Cr³⁺) adsorption from liquid solution. The specific surface area and average pore diameter of each sample were determined using the BET method. Finally, it was found that selected biochars can be applied as adsorbent or a fuel. In detail, brewery grains-activated carbon had the highest surface area, wheat straw-activated carbon adsorbed the highest amount of Cr³⁺, and wheat straw chars presented the best combustion properties. Full article

(This article belongs to the Special Issue Bioenergy Conversion Technologies)

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10 pages, 11538 KiB

Open AccessArticle

Effect of Ignition Energy and Hydrogen Addition on Laminar Flame Speed, Ignition Delay Time, and Flame Rising Time of Lean Methane/Air Mixtures

by Minh Tien Nguyen, Van Van Luong, Quoc Thai Pham, Minh Tung Phung and Phu Nguu Do

Energies 2022, 15(5), 1940; https://doi.org/10.3390/en15051940 - 07 Mar 2022

Cited by 8 | Viewed by 2824

Abstract

A series of experiments were performed to investigate the effect of ignition energy (E_ig) and hydrogen addition on the laminar burning velocity (S_u⁰), ignition delay time (t_delay), and flame rising time (t_rising [...] Read more.

A series of experiments were performed to investigate the effect of ignition energy (E_ig) and hydrogen addition on the laminar burning velocity (S_u⁰), ignition delay time (t_delay), and flame rising time (t_rising) of lean methane−air mixtures. The mixtures at three different equivalence ratios (ϕ) of 0.6, 0.7, and 0.8 with varying hydrogen volume fractions from 0 to 50% were centrally ignited in a constant volume combustion chamber by a pair of pin-to-pin electrodes at a spark gap of 2.0 mm. In situ ignition energy (E_ig ∼2.4 mJ ÷ 58 mJ) was calculated by integration of the product of current and voltage between positive and negative electrodes. The result revealed that the S_u⁰ value increases non-linearly with increasing hydrogen fraction at three equivalence ratios of 0.6, 0.7, and 0.8, by which the increasing slope of S_u⁰ changes from gradual to drastic when the hydrogen fraction is greater than 20%. t_delay and t_rising decrease quickly with increasing hydrogen fraction; however, t_rising drops faster than t_delay at ϕ = 0.6 and 0.7, and the reverse is true at ϕ = 0.8. Furthermore, t_delay transition is observed when E_ig > E_ig,critical, by which t_delay drastically drops in the pre-transition and gradually decreases in the post-transition. These results may be relevant to spark ignition engines operated under lean-burn conditions. Full article

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

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21 pages, 4004 KiB

Open AccessArticle

Effective Inhibition of Carbon Steel Corrosion by Waterborne Polyurethane Based on N-tert-Butyl Diethanolamine in 2M HCl: Experimental and Computational Findings

by Yulia F. Zaripova, Sherzod Razhabov, Roman S. Pavelyev, Svetlana S. Vinogradova, Renat R. Nazmutdinov, Iskander R. Vakhitov and Mikhail A. Varfolomeev

Energies 2022, 15(5), 1939; https://doi.org/10.3390/en15051939 - 07 Mar 2022

Cited by 1 | Viewed by 2074

Abstract

The efficiency of corrosion inhibition for waterborne polyurethane based on N-tert-butyl diethanolamine (tB-WPU) is investigated using different techniques. Corrosion weight loss, open circuit potential experiments, electrochemical impedance spectroscopy, and potentiodynamic polarization measurements show that both a commercial reagent and [...] Read more.

The efficiency of corrosion inhibition for waterborne polyurethane based on N-tert-butyl diethanolamine (tB-WPU) is investigated using different techniques. Corrosion weight loss, open circuit potential experiments, electrochemical impedance spectroscopy, and potentiodynamic polarization measurements show that both a commercial reagent and a polyurethane-based inhibitor prevent corrosion at increasing temperature to 50 °C. At 75 °C, the activity of both reagents is reduced. In stirring conditions, the effectiveness of acid corrosion inhibition (25 °C, 500 ppm) drops abruptly from 89.5% to 60.7%, which is related presumably to the complexity of binding the polymer molecules to the metal surface. As follows from thermodynamic calculations, the adsorption of tB-WPU on the metal surface in 2M HCl can be treated as a physisorption. Model quantum–chemical calculations support the experimental studies and elucidate the nature of steel surface–inhibitor molecule chemical bond, which is realized mainly by carboxyl and amino groups. It is concluded that WPUs can be considered as a perspective alternative to commercial oilfield reagents due to their versatility. Full article

(This article belongs to the Special Issue Advanced Technologies for Enhanced Oil Recovery (EOR) and Improved Oil Recovery (IOR))

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23 pages, 1286 KiB

Open AccessArticle

A Closed Form Selected Mapping Algorithm for PAPR Reduction in OFDM Multicarrier Transmission

by Sara Carcangiu, Alessandra Fanni and Augusto Montisci

Energies 2022, 15(5), 1938; https://doi.org/10.3390/en15051938 - 07 Mar 2022

Cited by 9 | Viewed by 1816

Abstract

Nowadays, the demand for communication multi-carriers’ channels, where the sub-channels are made mutually independent by using orthogonal frequency division multiplexing (OFDM), is widespread both for wireless and wired communication systems. Even if OFDM is a spectrally efficient modulation scheme, due to the allowed [...] Read more.

Nowadays, the demand for communication multi-carriers’ channels, where the sub-channels are made mutually independent by using orthogonal frequency division multiplexing (OFDM), is widespread both for wireless and wired communication systems. Even if OFDM is a spectrally efficient modulation scheme, due to the allowed number of subcarriers, high data rate, and good coverage, the transmitted signal can present high peak values in the time domain, due to inverse fast Fourier transform operations. This gives rise to high peak-to-average power ratio (PAPR) with respect to single carrier systems. These peaks can saturate the transmitting amplifiers, modifying the shape of the OFDM symbol and affecting its information content, and they give rise to electromagnetic compatibility issues for the surrounding electric devices. In this paper, a closed form PAPR reduction algorithm is proposed, which belongs to selected mapping (SLM) methods. These methods consist in shifting the phases of the components to minimize the amplitude of the peaks. The determination of the optimal set of phase shifts is a very complex problem; therefore, the SLM approaches proposed in literature all resort to iterative algorithms. Moreover, as this calculation must be performed online, both the computational cost and the effect on the bit rate (BR) cannot be established a priori. The proposed analytic algorithm finds the optimal phase shifts of an approximated formulation of the PAPR. Simulation results outperform unprocessed conventional OFDM transmission by several dBs. Moreover, the complementary cumulative distribution function (CCDF) shows that, in most of the packets, the proposed algorithm reduces the PAPR if compared with randomly selected phase shifts. For example, with a number of shifted phases

U = 8,

the CCFD curves corresponding to the analytical and random methods intersect at a probability value equal to 10⁻², which means that in 99% of cases the former method reduces the PAPR more than the latter one. This is also confirmed by the value of the gain, which, at the same number of shifted phases and at the probability value equal to 10⁻¹, changes from 2.09 dB for the analytical to 1.68 dB for the random SLM. Full article

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16 pages, 17632 KiB

Open AccessArticle

Water Invasion Law and Water Invasion Risk Identification Method for Deep Sea Bottom-Water Gas Reservoir

by Jiqiang Zhi, Lifeng Bo, Guohui Qu, Nan Jiang and Rongzhou Zhang

Energies 2022, 15(5), 1937; https://doi.org/10.3390/en15051937 - 07 Mar 2022

Cited by 3 | Viewed by 1834

Abstract

This study analyzes the water invasion characteristics and water encroachment of the deep sea bottom-water gas reservoir (LS17 field) in the South China Sea for the purpose of developing horizontal wells. Gas-producing profile tests and a three-dimensional (3D) water invasion simulation are used [...] Read more.

This study analyzes the water invasion characteristics and water encroachment of the deep sea bottom-water gas reservoir (LS17 field) in the South China Sea for the purpose of developing horizontal wells. Gas-producing profile tests and a three-dimensional (3D) water invasion simulation are used to produce a quantitative analysis of the bottom-water cresting influence factors. On this basis, we establish a suitable risk identification method for the water influx of a deep bottom-water reservoir. The results show that: (1) During the development of a bottom-water gas reservoir, the water ridging is affected by reservoir heterogeneity, production system and heel–toe effect of a horizontal wellbore, and reservoir heterogeneity is the main influencing factor; (2) the horizontal–vertical ratio of the well area determines whether the gas well productivity will be affected by the risk of water invasion. The stronger the reservoir heterogeneity, the smaller the safety limit value of the horizontal–vertical ratio; (3) when the permeability differential increases gradually, the safety limit value of the transverse longitudinal ratio decreases in turn; (4) based on the relationship curve between permeability level difference and the safety limit value of the horizontal–vertical ratio in the well area, the horizontal–vertical ratio of the N1H well is far greater than the safety limit value. The well is at high risk of water invasion and should be developed by water control. In order to improve deep seabed water and gas reservoirs, water control development should be carried out in well areas with sufficient water energy and high water invasion risk. The water invasion characteristics of bottom-water gas reservoirs under different water control technologies (such as variable density screen technology, filling water blocking, breathable coated gravel technology, etc.) and production systems (periodic gas production technology) should be studied. The research results can not only judge the water invasion risk of deep seabed water and gas reservoirs under different permeability levels and gas production rates but also provide a reference for water control development of offshore and onshore bottom-water and gas reservoirs. Full article

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16 pages, 6328 KiB

Open AccessArticle

Prediction of Wall and Indoor Hygrothermal Properties of Rammed Earth Folk House in Northwest Sichuan

by Qinglong Gao, Tao Wu, Lei Liu, Yong Yao and Bin Jiang

Energies 2022, 15(5), 1936; https://doi.org/10.3390/en15051936 - 07 Mar 2022

Cited by 5 | Viewed by 2014

Abstract

The climate crisis is one of the most important problems today. In the process of human building, the use of cement, steel, and other industrial materials in the process of building construction and recycling has brought a huge burden to the natural environment. [...] Read more.

The climate crisis is one of the most important problems today. In the process of human building, the use of cement, steel, and other industrial materials in the process of building construction and recycling has brought a huge burden to the natural environment. Earth is one of the oldest building materials, its availability and insulation make it an excellent constructive solution in human history. Among several existing earth construction techniques, rammed earth is one of the most relevant. In this paper, a numerical model of the rammed earth folk house in Mianyang was established, and an experimental device was built to verify it. With the typical meteorological year data of Mianyang in northwest Sichuan, the heat and moisture transfer in rammed earth wall, as well as the indoor thermal and moisture environment were numerically simulated. The results show that the rammed earth wall weakens the temperature fluctuation of the inner surface of the wall and makes the peak temperature of the inner surface of the wall lag the outer surface. The relative humidity in the center of the rammed earth wall can be maintained at about 60%, both in winter and summer. The moisture absorption and desorption capacity of rammed earth walls without inner decorative materials is about three times that of gypsum board, and the use of a waterproof coating will render the rammed earth wall almost unable to adjust the indoor relative humidity. Additionally, the use of decorative materials will increase the fluctuation range of indoor relative humidity and the risk of mold breeding. Full article

(This article belongs to the Special Issue Green Buildings for Carbon Neutral)

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13 pages, 22016 KiB

Open AccessArticle

Robust Sliding Mode Control of the Permanent Magnet Synchronous Motor with an Improved Power Reaching Law

by Zhenjie Gong, Xin Ba, Chengning Zhang and Youguang Guo

Energies 2022, 15(5), 1935; https://doi.org/10.3390/en15051935 - 07 Mar 2022

Cited by 4 | Viewed by 2130

Abstract

To improve the suppression ability of uncertain disturbance of the sliding mode control driving system of the surface-mounted permanent magnet synchronous motor (SPMSM) and to reduce the chattering of the control output, a robust sliding mode control strategy with an improved power reaching [...] Read more.

To improve the suppression ability of uncertain disturbance of the sliding mode control driving system of the surface-mounted permanent magnet synchronous motor (SPMSM) and to reduce the chattering of the control output, a robust sliding mode control strategy with an improved power reaching law (IPRL) is proposed in this paper. Compared with the traditional fast power reaching law (FPRL), the IPRL incorporates the sum of the power terms of the system state variables into the conventional power terms, and uses hyperbolic tangent saturation function to replace the piecewise function, which can effectively suppress the sliding mode chattering and improve the convergence speed of the system state to the sliding mode surface. Furthermore, the robust sliding mode speed controller and sliding mode current controller of the SPMSM are designed separately with the IPRL, and detailed simulation verification is carried out to reveal the effectiveness of the IPRL. Simulation and experimental results show that compared with the FPRL, the proposed IPRL can reduce the inherent chattering phenomenon in sliding mode control, and the IPRL-based speed and current control strategy can effectively improve the dynamic performance and robustness of the system. Full article

(This article belongs to the Special Issue Advanced Electrical Machine Design and Optimization)

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13 pages, 4885 KiB

Open AccessArticle

Experimental and Numerical Study on the Dynamic Thermal Response of Building Interior Decoration Coatings during Intermittent Air-Conditioning in High U-Values Buildings in China

by Yanru Li, Yong Chen, Lili Zhang and Xinyi Li

Energies 2022, 15(5), 1934; https://doi.org/10.3390/en15051934 - 07 Mar 2022

Cited by 1 | Viewed by 1729

Abstract

Interior decorating coatings (IDCs) are the heat-transfer medium between indoor air and building walls, which mainly form the cooling load and are important in an indoor built environment. To explore the impacts of the precooling process of IDCs on indoor thermal environment of [...] Read more.

Interior decorating coatings (IDCs) are the heat-transfer medium between indoor air and building walls, which mainly form the cooling load and are important in an indoor built environment. To explore the impacts of the precooling process of IDCs on indoor thermal environment of occupants during intermittent air conditioning, this paper investigated the dynamic thermal response of IDCs. Three representative coating materials were integrated to the external insulation wall and internal insulation wall, and their interior surface temperatures were experimentally tested under intermittent air conditioning operation in southern China. Moreover, a heat transfer model was established and verified to analyze the influences of IDC on the thermal response of the interior surface. During the pull-down process, the cold was accumulated in the IDC layer with small thermal diffusivity and could not be transferred into the wall inside, so that the largest temperature reduction was obtained, meaning that the indoor thermal environment could meet the setpoint in a short time. According to modelling calculations, the thick IDC with volumetric specific heat capacity less than 1 × 10⁵ J/(m³·K) and small thermal conductivity integrated to the internal insulation wall was beneficial to increase the thermal response rate and had the better energy-saving efficiency. Full article

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18 pages, 5940 KiB

Open AccessArticle

Motion Characteristics of High-Speed Supercavitating Projectiles Including Structural Deformation

by Chuang Huang, Zhao Liu, Zixian Liu, Changle Hao, Daijin Li and Kai Luo

Energies 2022, 15(5), 1933; https://doi.org/10.3390/en15051933 - 07 Mar 2022

Cited by 4 | Viewed by 1845

Abstract

High-speed supercavitating projectiles receive tremendous hydrodynamic force when flying underwater in tail-slap mode, and have obvious structural deformation and structural vibration. To study the motion characteristics of high-speed supercavitating projectiles, a bidirectional fluid-structure interaction model was established, and validated by comparing with the [...] Read more.

High-speed supercavitating projectiles receive tremendous hydrodynamic force when flying underwater in tail-slap mode, and have obvious structural deformation and structural vibration. To study the motion characteristics of high-speed supercavitating projectiles, a bidirectional fluid-structure interaction model was established, and validated by comparing with the existing results. The motion, supercavitation flow field, and structural deformation response process of a supercavitating projectile were numerically investigated under the conditions of initial speed within 800–1600 m/s. It was found that the tail-slap motion of high-speed supercavitating projectiles is correlated with a high-frequency structural vibration. Further, the amplitude of the structural vibration increases with the initial speed. When flying with an initial speed higher than 1200 m/s, supercavitating projectiles encounter a great structural deformation under the action of the huge hydrodynamic load, which exerts a significant influence on the motion characteristic, and even destroys the trajectory stability. Thus, the supercavitating projectile cannot be regarded as a rigid body any more, and the structural response effect must be considered. Full article

(This article belongs to the Special Issue Transport Phenomena Studies for Renewable Energy Development)

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40 pages, 6078 KiB

Open AccessReview

Optimization Models under Uncertainty in Distributed Generation Systems: A Review

by Àlex Alonso-Travesset, Helena Martín, Sergio Coronas and Jordi de la Hoz

Energies 2022, 15(5), 1932; https://doi.org/10.3390/en15051932 - 07 Mar 2022

Cited by 12 | Viewed by 2895

Abstract

Distributed generation systems (DGSs) are one of the key developments enabling the energy transition. DGSs provide users with increased control over their energy use and generation, but entail greater complexity in their design and operation. Traditionally, optimization models have been used to overcome [...] Read more.

Distributed generation systems (DGSs) are one of the key developments enabling the energy transition. DGSs provide users with increased control over their energy use and generation, but entail greater complexity in their design and operation. Traditionally, optimization models have been used to overcome this complexity, and currently, research is focusing on integrating uncertainties on them. This review attempts to analyze, classify and discuss 170 articles dealing with optimization of DGSs under uncertainty. A survey has been performed to identify the selected manuscripts and the strengths and weaknesses of previous reviews. As a result, an innovative classification has been designed and the distinct elements of optimization models in DGSs have been highlighted: microgrid architecture, sources of uncertainty, uncertainty addressing methods, problem types and formulations, objective functions, optimization algorithms and additional features. Each part is detailed thoroughly to provide an instructive overview of the research output in the area. Subsequently, several aspects of interest are discussed in depth: the future of dealing with uncertainty, the main contributions and trends, and the relative importance of the field. It is expected that this review will be of use to both experts and lay people to learn more about the current state of optimization models in DGSs and provide insights into how to further develop this field. Full article

(This article belongs to the Collection Renewable Energy and Energy Storage Systems)

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14 pages, 647 KiB

Open AccessArticle

Evaluating the Impact of Public Information and Training Campaigns to Improve Energy Efficiency: Findings from the Italian Industry

by Michele Preziosi, Alessandro Federici and Roberto Merli

Energies 2022, 15(5), 1931; https://doi.org/10.3390/en15051931 - 07 Mar 2022

Cited by 5 | Viewed by 1746

Abstract

Energy efficiency is a pillar for the energy system transition and for reaching the Sustainable Development Goals. In the light of the “energy efficiency first!” principle, European member states enforce policies to spread energy saving throughout the whole energy chain involving both citizens [...] Read more.

Energy efficiency is a pillar for the energy system transition and for reaching the Sustainable Development Goals. In the light of the “energy efficiency first!” principle, European member states enforce policies to spread energy saving throughout the whole energy chain involving both citizens and industries. In this context, information and training campaigns arise as valuable support tools to disseminate energy efficiency and, therefore, for reducing energy consumption. Although various studies have evaluated the impact of information campaigns targeted to citizens, there is a lack of investigations that assess the impact of campaigns dedicated to industry sectors. This study discusses the results of a survey targeted at energy-intensive Italian companies, with a sample of 300 responses. Starting from the analysis of drivers that trigger the implementation of energy efficiency measures, the paper proposes an approach to evaluate the amount of energy savings linked to the Italian information and training program targeted to industries carried out by the Italian Energy Efficiency Agency. Results show that although information campaigns are not a crucial driver for companies, they are recognized as a factor that contributes to the implementation of energy efficiency practices. Findings show that roughly 1.4% of energy savings noted by interviewed companies to the Italian Energy Efficiency Agency are a direct effect of the information and training program. This outcome has significant implications, especially for decision-makers, giving evidence of the efficacy of information campaigns on industries, which have great potential for the transition to low carbon production systems. Full article

(This article belongs to the Topic Energy Efficiency, Environment and Health)

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18 pages, 1053 KiB

Open AccessFeature PaperReview

A Review about Flux-Weakening Operating Limits and Control Techniques for Synchronous Motor Drives

by Nicola Bianchi, Paolo Gherardo Carlet, Luca Cinti and Ludovico Ortombina

Energies 2022, 15(5), 1930; https://doi.org/10.3390/en15051930 - 07 Mar 2022

Cited by 8 | Viewed by 4655

Abstract

This paper deals with motor design aspects and control strategies for the flux-weakening (FW) operation of synchronous motors. The theory of FW is described by taking into account different control schemes. The advantages and drawbacks of each one are discussed, as well. Moreover, [...] Read more.

This paper deals with motor design aspects and control strategies for the flux-weakening (FW) operation of synchronous motors. The theory of FW is described by taking into account different control schemes. The advantages and drawbacks of each one are discussed, as well. Moreover, some motor design considerations for achieving an effective FW operation are illustrated for permanent magnet (PM), wound rotor (WR) and reluctance (REL) synchronous machines, using the per unit approach. The distinguishing characteristic of this review provides two-fold attention on both machine design and control strategies obtained by several collaborations with industrial and commercial companies. Full article

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56 pages, 64533 KiB

Open AccessArticle

Machine Learning-Enhanced Play Fairway Analysis for Uncertainty Characterization and Decision Support in Geothermal Exploration

by R. Chadwick Holmes and Aimé Fournier

Energies 2022, 15(5), 1929; https://doi.org/10.3390/en15051929 - 07 Mar 2022

Cited by 3 | Viewed by 3100

Abstract

Geothermal exploration has traditionally relied on geological, geochemical, or geophysical surveys for evidence of adequate enthalpy, fluids, and permeability in the subsurface prior to drilling. The recent adoption of play fairway analysis (PFA), a method used in oil and gas exploration, has progressed [...] Read more.

Geothermal exploration has traditionally relied on geological, geochemical, or geophysical surveys for evidence of adequate enthalpy, fluids, and permeability in the subsurface prior to drilling. The recent adoption of play fairway analysis (PFA), a method used in oil and gas exploration, has progressed to include machine learning (ML) for predicting geothermal drill site favorability. This study introduces a novel approach that extends ML PFA predictions with uncertainty characterization. Four ML algorithms—logistic regression, a decision tree, a gradient-boosted forest, and a neural network—are used to evaluate the subsurface enthalpy resource potential for conventional or EGS prospecting. Normalized Shannon entropy is calculated to assess three spatially variable sources of uncertainty in the analysis: model representation, model parameterization, and feature interpolation. When applied to southwest New Mexico, this approach reveals consistent enthalpy trends embedded in a high-dimensional feature set and detected by multiple algorithms. The uncertainty analysis highlights spatial regions where ML models disagree, highly parameterized models are poorly constrained, and predictions show sensitivity to errors in important features. Rapid insights from this analysis enable exploration teams to optimize allocation decisions of limited financial and human resources during the early stages of a geothermal exploration campaign. Full article

(This article belongs to the Special Issue Machine Learning Applications in Petroleum Industries and Geothermal Systems)

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16 pages, 1437 KiB

Open AccessArticle

Management of Energy Enterprises in Zero-Emission Conditions: Bamboo as an Innovative Biomass for the Production of Green Energy by Power Plants

by Piotr F. Borowski

Energies 2022, 15(5), 1928; https://doi.org/10.3390/en15051928 - 07 Mar 2022

Cited by 31 | Viewed by 4105

Abstract

Managing energy-producing companies as well as managing the entire energy sector in the light of legal and environmental requirements requires a new vision, mission, and strategy. The paper analyses the strategies of energy enterprises. It is not enough now to produce energy and [...] Read more.

Managing energy-producing companies as well as managing the entire energy sector in the light of legal and environmental requirements requires a new vision, mission, and strategy. The paper analyses the strategies of energy enterprises. It is not enough now to produce energy and deliver it at appropriate, acceptable prices to consumers; it must be generated with the least negative impact on the environment. To achieve that plan, companies should cut the carbon intensity of their products by 20% by 2030, 45% by 2035, and 100% by 2050, using a baseline of 2016. To compared to 1990 levels, the greenhouse gas emission reduction target for 2030 should be increased to 55%. Bioenergy will represent 18% of total final energy consumption in 2050. Additionally, this requires the development of a long-term strategy that can force companies to completely reorganize their production or start a new operation and activities. A low-cost strategy or a competition strategy are insufficient, and it is necessary to look for new strategies that combine adaptation to the requirements of the external environment with the use of innovative solutions. The article analyzes the possibilities of implementing an innovative strategy based on biomass, especially bamboo biomass. The reduction in CO₂ emissions of bamboo, taking into account life cycle emissions, can reach up to 85%. The novelty is to show the possibility of producing electricity by a large-scale power plant solely based on bamboo biomass on the example of a power plant located in the Tokushima prefecture, Japan. Another novelty is the fact that this article draws attention to the problem of burning bamboo in a power plant. The problem is that, as a result of burning bamboo, the clinker settles quite quickly. The study analyzes the selected ingredients for co-firing, which improve the combustion parameters of bamboo biomass (e.g., blended 20% bamboo with 80% pine or 30% bamboo with 70% tree bark). The importance of this research lies in the fact that it shows new innovative solutions in the energy sector that will help to achieve emission reductions. In addition, the article proposes to use eco-innovations and pay attention to eco-efficiency. Such solutions are an opportunity for ecological development through the use of bamboo as a fuel, which is classified as a renewable energy source by power plants. Full article

(This article belongs to the Special Issue Strategic Management and Process Management in Energy Sector)

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16 pages, 8727 KiB

Open AccessArticle

Study on Surface Subsidence Characteristics Based on Three-Dimensional Test Device for Simulating Rock Strata and Surface Movement

by Xingyin Ma, Zhiyong Fu, Yurong Li, Pengfei Zhang, Yongqiang Zhao and Guoping Ma

Energies 2022, 15(5), 1927; https://doi.org/10.3390/en15051927 - 07 Mar 2022

Cited by 6 | Viewed by 1773

Abstract

The main functions of a three-dimensional test device for simulating rock formations and surface movement affected by underground coal mining were described in detail, and a series of similar related tests were carried out. The device consisted of an outer frame, a pressurization [...] Read more.

The main functions of a three-dimensional test device for simulating rock formations and surface movement affected by underground coal mining were described in detail, and a series of similar related tests were carried out. The device consisted of an outer frame, a pressurization unit, a pulling unit, and a coal seam simulation portion. Using this test device, supported by monitoring methods such as the three-dimensional laser scanner method, a model test study on the surface subsidence characteristics caused by coal seam mining was carried out. Combined with the field measurements, the transfer law of surface subsidence caused by coal seam mining was revealed, and the whole surface subsidence response process was analyzed. The experimental results show that the subsidence caused by mining disturbances below the coal seam accounts for 79.3% of the total subsidence, which is the dominant factor of the total surface subsidence. After long-term surface observations, surface subsidence can be divided into four stages after coal mining, and the settlement value of the obvious settlement stage accounts for more than 60% of the total settlement value. The above test results fully reflect the feasibility and practicality of the three-dimensional test device to simulate rock strata and surface movement and provide a new experimental research tool that can be used to further study the surface subsidence characteristics and control caused by coal mining. Full article

(This article belongs to the Topic Mining Safety and Sustainability)

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25 pages, 5378 KiB

Open AccessArticle

Comparison of Environmental Impact Assessment Methods in the Assembly and Operation of Photovoltaic Power Plants: A Systematic Review in the Castilla—La Mancha Region

by Marichell Zarzavilla, Andrea Quintero, Manuela Andrés Abellán, Francisco López Serrano, Miguel Chen Austin and Nathalia Tejedor-Flores

Energies 2022, 15(5), 1926; https://doi.org/10.3390/en15051926 - 07 Mar 2022

Cited by 6 | Viewed by 3488

Abstract

Solar energy is in high demand due to its environmental benefits and economic potential; however, concerns remain about the total impact it holds. In 2020, for Spain, Castilla-La Mancha was the second autonomous community with the highest photovoltaic energy production. Thus, a systematic [...] Read more.

Solar energy is in high demand due to its environmental benefits and economic potential; however, concerns remain about the total impact it holds. In 2020, for Spain, Castilla-La Mancha was the second autonomous community with the highest photovoltaic energy production. Thus, a systematic review on 15 large-scale PV solar energy projects was carried out to assess the industry impacts, through environmental impact assessment (EIA), within the Autonomous Community of Castilla—La Mancha. An estimation of these impacts from a pre-operational approach is presented, based on primary energy needs and emissions discarded during its life cycle due to the manufacture, operation, and recycling of the photovoltaic modules. Based on both the life cycle assessment (LCA) and EIA, the approaches were compared with the results obtained. The obtained results suggest that determining the actual impacts of power plants in this region could provide justified information for the public administration and technicians in the measures for the installation and operation of PV plants and the future benefits of renewable solar technologies. Furthermore, the results indicate the possibility to recognize the relationship between the size of the plant and a high generation capacity, with a shorter time to pay for emissions from the manufacture and recycling of panels, suggesting that it is around 1.66–2.08 years for the Castilla-La Mancha region. Full article

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20 pages, 1994 KiB

Open AccessArticle

Analyzing the Societal Cost of Electric Roads Compared to Batteries and Oil for All Forms of Road Transport

by Hasan Huseyin Coban, Aysha Rehman and Abdullah Mohamed

Energies 2022, 15(5), 1925; https://doi.org/10.3390/en15051925 - 06 Mar 2022

Cited by 12 | Viewed by 3556

Abstract

This article is designed to demonstrate that electric roads are an affordable way to electrify all forms of road transport—not only cars, but also buses and trucks. Electric roads represent a way to power electric vehicles without relying solely on batteries. The idea [...] Read more.

This article is designed to demonstrate that electric roads are an affordable way to electrify all forms of road transport—not only cars, but also buses and trucks. Electric roads represent a way to power electric vehicles without relying solely on batteries. The idea is that when an electric vehicle reaches an electric road, it stops using power from the battery and instead uses power directly from the road itself. The primary challenge for electric vehicles is still the perception of a compromised quality of life in owning an electric vehicle due to a limited range compared with petrol and diesel cars, today. This paper introduces a new technology, currently experiencing rapid development, that can not only overcome range anxiety but make electric vehicles better, in terms of range, than petrol and diesel cars today. Furthermore, not only can this research help to arrange this, but it can also help, for the first time, to cost-effectively electrify heavy-duty transport, such as trucks and buses, which would be a huge breakthrough in terms of sustainability, as it is very important to start supplying electricity to heavy-duty vehicles. The case study provides a very hypothetical example of a trip with and without an electric road, covering a total of 26,011 km of highways and main roads. The results indicate that building electric roads is cheaper than many other alternatives. If a large battery is replaced with a smaller battery for each new vehicle sold, after 3 years, enough savings will be made to electrify all highways and main roads in Turkey. This paper can help transport operators and policymakers develop strategies to accelerate the adoption of electric vehicles by appropriately implementing electric road infrastructure. Full article

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17 pages, 11533 KiB

Open AccessArticle

Input Small-Signal Characteristics of Selected DC–DC Switching Converters

by Włodzimierz Janke, Maciej Bączek, Jarosław Kraśniewski and Marcin Walczak

Energies 2022, 15(5), 1924; https://doi.org/10.3390/en15051924 - 06 Mar 2022

Cited by 3 | Viewed by 2056

Abstract

The main goal of this study was to derive small-signal models of the input characteristics of buck, boost, and flyback converters working in continuous conduction mode (CCM) and discontinuous conduction mode (DCM). The models presented in the paper were derived using the separation [...] Read more.

The main goal of this study was to derive small-signal models of the input characteristics of buck, boost, and flyback converters working in continuous conduction mode (CCM) and discontinuous conduction mode (DCM). The models presented in the paper were derived using the separation of variables approach and included the parasitic resistances of all converter components. The paper features a discussion about the limitations of the model accuracy. The presented characteristics were obtained by calculation and verified by measurements. The input characteristics of converters are essential in the design of converters used in Power Factor Correction systems as well as in maximum power point tracking systems (MPPT). Full article

(This article belongs to the Topic Power System Modeling and Control)

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