Green innovation has become an important support to promote the strategic goals of peak carbon dioxide emission and high-quality economic development. This paper systematically examines whether internal control can effectively drive enterprise green innovation and achieve the “win−win” result of enterprise economic development and environmental protection. We found that internal control can significantly improve the green innovation level of enterprises, which is mainly reflected in the mandatory disclosure stage of internal control information and the other four elements of internal control, except the control environment. The mechanism test found that internal control can promote green innovation by reducing enterprise risks, alleviating agency conflicts, relieving financing constraints, and improving the rationality of innovation investment. The heterogeneity test found that the promotion effect of internal control on green innovation is more significant in large enterprises and pri... [more]

Small and medium-sized enterprises around the world play a key role in building economic growth and maintaining environmental sustainability. This strategic role in the economy depends on the possessed competitive advantage, which will increasingly depend on the ecological behavior of SMEs. Therefore, it is justified to undertake research the main goal of which is to identify the pro-ecological activities of SMEs conducive to achieving a competitive advantage. The original empirical research was conducted in 2021 on a sample of 452 small and medium-sized enterprises in Poland. The research was based on a questionnaire. The research allowed for the assessment of sustainable energy management by assessing the awareness of entrepreneurs, assessing the pro-ecological activities undertaken, and assessing the impact of pro-ecological activities on shaping the competitive advantages of enterprises in 2015−2020. The surveyed entrepreneurs considered the most important components of the company... [more]

Aero-engine combustors may experience extreme low pressures in the case of an in-flight shutdown, which makes the study of aviation kerosene flame propagation characteristics at low pressures important. The present work examined flame propagation during the combustion of aviation kerosene over the pressure range from 25 to 100 kPa using a constant-volume bomb apparatus. The laminar burning speeds at different initial pressures, temperatures and equivalence ratios were measured and compared. In addition, numerical simulations were used to examine the reaction sensitivity of the laminar burning speed at low pressure. In trials at the lean flammability limit, the data indicated that it was more difficult to ignite the fuel under a lower pressure condition of 25 kPa and a lower temperature condition of 420 K. The experimental results of laminar burning speed were fitted to an equation providing the laminar burning speeds expected at different pressures (25−100 kPa), temperatures (400−480 K... [more]

Among the several methods investigated over the past few years for the thermal mitigation of buildings in urban areas, green roof systems seem to be one of the most suitable solutions for several reasons, and researchers encourage the further study and implementation of these roofing techniques because of the potential benefits that they offer. So far, intensive, extensive and semi-intensive green roofs are considered to be a better option in terms of both energy efficiency and green area increase. However, there are some aspects that cause green roofs not to be suitable to every application, preventing their use from spreading, such as high maintenance and costs required by these sophisticated systems. Few studies aimed at overcoming the limits of green roofs have hinted at the possibility of implementing hydroponic cultures in green roof systems. This soil-less technology might overcome some issues, such as identifying the suitable substrate to support the growth of the vegetation. T... [more]

This study presents an experimental and numerical investigation on a surface sliding discharge in a supersonic airflow in the presence of an oblique shock wave. In experiments, flow Mach numbers were 1.20−1.68 in the shock tube combined with the discharge chamber. A single high-voltage 25 kV pulse sustains the plasma; the discharge current has a duration of ~500 ns. A surface sliding discharge is developed as a localized channel in a zone of interaction of an oblique shock wave with a boundary layer on the upper wall of the discharge chamber. The discharge channel acts as a linear source of heat and is at the origin of the induced shock wave. The flow field in the discharge chamber is spatio-temporally surveyed using high-speed shadowgraphy imaging with a frequency of up to 525,000 frames per second. The experiments show that the perturbed flow restored the initial structure after more than 100 μs. Numerical simulation with local energy input into the supersonic flow in a flat channel... [more]

The receiver serves as a critical component in tower-type concentrated solar power plants. Responsible for light-heat conversion, the efficiency of the receiver significantly affects the overall performance of the power plant. In the current study, the thermal performance of external receivers was investigated. An experiment was set up similarly using the solar simulator to experimentally investigate the heat losses of a billboard receiver. A billboard-type external receiver was designed, fabricated, and experimented with. A solar simulator having seven xenon lamps characteristics similar to the sunlight spectrum was used to obtain heat flux at the surface of the receiver. Convection losses in the head-on wind direction were evaluated, along with the radiation losses. The thermal efficiency of the billboard receiver calculated experimentally was around 83.9%. Numerical simulations were also carried out to compare the results against the experimental data. A variation of ±5% observed be... [more]

Subcooled flow boiling was experimentally investigated in a horizontal annulus with a temperature-controlled boiling surface and transparent outer pipe facilitating visualization. Boiling occurs on a copper tube with a diameter of 12 mm in an annulus with a 2 mm gap. Refrigerant R245fa is used as a working fluid. The focus of this study is to explore the effect of heat flux variation on the boiling flow patterns at approximately constant inlet flow conditions of the working fluid (fixed mass flux and inlet fluid temperature). Subcooled flow boiling is recorded by a high-speed camera, images are analyzed by a neural network to determine the bubble size distributions and their variation with the heat flux. The experimental setup being a part of the laboratory THELMA (Thermal Hydraulics experimental Laboratory for Multiphase Applications) at the Reactor Engineering Division of Jožef Stefan Institute, analysis methods and measurement results are presented and discussed.

Zero carbon emission is a mainstream trend in the development of internal combustion engines (ICEs) in the future. ICEs need to constantly surpass the existing working mechanism, especially in order to explore the possibility of new combustion methods. Dual-fuel combustion is a good way to reduce carbon emissions and achieve clean combustion. However, the traditional internal combustion engine is limited by its own structure, restricting its performance improvement. The opposed-piston, two-stroke (OP2S) diesel engine is a potential power system with a high degree of structural adjustability. Therefore, this work attempted to apply methanol/diesel dual-fuel to OP2S engines in order to explore efficient and clean combustion modes in the future. In this work, a one-dimensional simulation model of an OP2S diesel engine was established and verified. The effect of the port height to stroke ratio on the performance of the OP2S diesel engine was mainly studied for different methanol blending r... [more]

Performance guarantees and tests of thermal power plants are usually carried out at 100% rate output capacity. However, fossil-fired power plants have decreased full load hours, affecting energy efficiency, and are subjected to frequent load changes caused by variable renewable electricity and potential grid stability. Therefore, this study is conducted to calculate and draw the characteristic curves for all stable loads of coal-fired power units including the 60%, 75%, and 100% rate output. The study focuses on the corrected plant net heat rates—gross unit outputs, net standard coal consumption rates—throttle steam pressures, and corrected plant net efficiencies—carbonic emission rates. In addition, the experimental investigation for energy efficiency and carbonic emission of the latest larger-scale (+600 MW) coal-fired power generation units in Vietnam are also implemented using a performance guarantee calculation software called “PG_Cal” version 0.0, which is based on a mass and ene... [more]

The main objective of this paper is to select the optimal configuration of a ship’s power system, considering the use of fuel cells and batteries, that would achieve the lowest CO2 emissions also taking into consideration the number of battery cycles. The ship analyzed in this work is a Platform Supply Vessel (PSV) used to support oil and gas offshore platforms transporting goods, equipment, and personnel. The proposed scheme considers the ship’s retrofitting. The ship’s original main generators are maintained, and the fuel cell and batteries are installed as complementary sources. Moreover, a sensitivity analysis is pursued on the ship’s demand curve. The simulations used to calculate the CO2 emissions for each of the new hybrid configurations were developed using HOMER software. The proposed solutions are auxiliary generators, three types of batteries, and a proton-exchange membrane fuel cell (PEMFC) with different sizes of hydrogen tanks. The PEMFC and batteries were sized as contai... [more]

In this research, the shuttle effect and the low sulfur activation of lithium−sulfur batteries were mitigated by coating the cathode side of Celgard 2400 separators with mixtures of carbon black/chitosan or carbon black/polyvinylidene fluoride using the simple slurry technique. Carbon nanoparticles and the polar groups of the polymers were responsible for boosting the reaction kinetics of sulfur and the chemical and physical trapping of lithium polysulfides. The adsorption of sulfur species in the coated separators was confirmed by the morphologic changes observed in the AFM and SEM images and by the new elements presented in the EDX spectra after 100 charge/discharge cycles. The high intensity of the peaks in the cyclic voltammograms and the long plateaus in the discharge profiles support the improvement in the reaction kinetics. The batteries with the carbon black/chitosan- and carbon black/polyvinylidene fluoride-coated separators reached high specific discharge capacities of 833 an... [more]

Enzymatic Biofuel Cell (EBC) represents a promising green source since it is capable of harvesting electricity from renewable and abundantly available biofuels using enzymes as catalysts. Nevertheless, nowadays long-term stability and low power output are currently the main concerns. To this end, several research studies focus on using complex tridimensional and highly expensive nanostructures as electrode support for enzymes. This increases cell performance whilst drastically reducing the economic feasibility needed for industrial viability. Thus, this paper analyzes a novel flow-based EBC consisting of covalent immobilized GOx (bioanode) and Laccase (biocathode) on a commercial flat conductive polymer. A suitable immobilization technique based on covalent ligands is carried out to enhance EBC durability. The experimental characterization demonstrates that the cell generates power over three weeks, reaching 590 mV and 2.41 µW cm−2 as maximum open circuit voltage and power density, res... [more]

A water diffuser is a critical auxiliary equipment for an ice storage system during the external ice melting process. This paper proposes a linear multi-pore water diffuser for an ice storage system with 500 t of refrigeration capacity to enhance the performance of external ice melting. By establishing a three-dimensional two-phase volume of fluid (VOF) model, different structural designs of water diffusers for the ice storage device are numerically examined regarding the degree of turbulence, flow velocity, and pressure drop. The results show that the optimal water diffuser with five rows of trunk pipe and six perforated pores arranged in per row of branch pipe with a 4 mm diameter of perforated pores exhibiting a relatively lower degree of turbulence with a lower pressure drop compared with the other designs in this study. Meanwhile, the influence of the flow velocity on the ice melting process is also investigated by a numerical model of ice melting. It is found that the fed flow ve... [more]

Long-term energy scenarios (LTES) have been serving as an important planning tool by a wide range of institutions. This article focuses on how LTES have been used (and also devised in some cases) in the government sector, and specifically how the new challenges and opportunities brought by the aspiration for the clean energy transition change the way that governments use LTES. The information tends to remain tacit, and a gap exists in understanding the way to enhance LTES use and development at the government level. To address this gap, we draw on the experience from national institutions that are leading the improvement in official energy scenario planning to articulate a set of overarching best practices to (i) strengthen LTES development, (ii) effectively use LTES for strategic energy planning and (iii) enhance institutional capacity for LTES-based energy planning, all in the context of new challenges associated with the clean energy transition. We present implementation experience... [more]

Facing the challenges of grid stability brought by the large-scale access of new energy to the grid, as one of the important means of frequency regulation of the grid, the doubly-fed pumped-storage units (DFPSU) have great practical significance in the study of the joint frequency regulation strategy with the thermal power unit (TPU). In order to reduce the frequency regulation pressure on the grid caused by the large-scale entry of new energy sources, this paper proposes a joint frequency regulation strategy for the TPU and DFPSU. Based on establishing the optimal scheduling model of the system, taking into account the minimum total operating cost and the optimal time as goals, the chaotic particle swarm optimization (CPSO) is proposed to solve the model. Finally, through MATLAB simulation, the relevant examples are studied and analyzed, and the simulation results verify that the joint frequency regulation strategy in this paper can effectively improve the frequency regulation perform... [more]

Oxygen electrode has a crucial impact on the performance of reversible solid oxide cells (RSOC), especially in solid oxide electrolysis cell (SOEC) mode. Herein, Sm0.5Sr0.5Co0.5O3-δ@Sm0.2Ce0.8O1.9 (5SSC@5SDC) composite material has been fabricated by the in-situ synthesis method and applied as the oxygen electrode for RSOCs with scandium stabilized zirconia (SSZ) electrolyte. The phase structures, thermal expansion coefficients, and micromorphologies of 5SSC@5SDC have all been further analyzed and discussed. 5SSC@5SDC is composed of a skeleton with large SDC particles in the diameter range of 200~300 nm and many fine SSC nanoparticles coated on the skeleton. Thanks to the special microstructure of 5SSC@5SDC, the electrolyte-supported RSOC with SSC@SDC oxygen electrode shows a polarization resistance of only 0.69 Ω·cm2 and a peak power density of 0.49 W·cm−2 at 800 °C with hydrogen as the fuel in solid oxide fuel cell (SOFC) mode. In addition, the electrolysis current density of RSOC wi... [more]

This paper presents a two-stage grid-connected PV system with reactive power management capability. The proposed model can send phase-shifted current to the grid during a low-voltage ride through (LVRT) to recover the voltage levels of the grid’s feeders. The novelty of the proposed algorithm, unlike the common methods, is that it does not need to disable the maximum power point tracking (MPPT) state while managing active and reactive power injection simultaneously. Moreover, the new method promotes a safety factor by offering overcurrent protection to the PV inverter. The phase-locked loop based on the synchronous reference frame (SRF-PLL) is optimized using a genetic algorithm (GA). The settling time of SRF-PLL’s step response is minimized, and the frequency dynamics are improved to enhance synchronization during LVRT. The system’s performance is tested and verified using MATLAB/Simulink simulations. The obtained results prove the effectiveness of the proposed control algorithm in ma... [more]

In this paper, the analysis and the design of a high-efficiency power electronic conversion system for offshore wind applications are presented. This system is composed of a 6-phase AC−DC converter based on the SiC power semiconductors, to be used to control the achievable power from the wind turbine electrical generator. Thanks to the phase redundancy, the proposed boost rectifier is suitable for applications where reliability and fault tolerance capability are the main targets. To select the appropriate power semiconductor devices, voltage and current ratings have to be determined. After that, the power loss equations are derived in order to evaluate the conversion efficiency. To design the appropriate DC-bus capacitor configuration, an analytical investigation is carried out by estimating the DC-bus RMS current and the voltage ripple. Finally, the thermal sizing of the system is calculated to identify a suitable heatsink. To validate the proposed analysis, the analytical results are... [more]

Load profiles of energy consumption from smart meters are becoming more and more available, and the amount of data to analyse is huge. In order to automate this analysis, the application of state-of-the-art data mining techniques for time series analysis is reviewed. In particular, the use of dynamic clustering techniques to obtain and visualise temporal patterns characterising the users of electrical energy is deeply studied. The performed review can be used as a guide for those interested in the automatic analysis and groups of behaviour detection within load profile databases. Additionally, a selection of dynamic clustering algorithms have been implemented and the performances compared using an available electric energy consumption load profile database. The results allow experts to easily evaluate how users consume energy, to assess trends and to predict future scenarios.

Anaerobic digestion (AD) and sewage sludge digestion (SD) plants generate significant quantities of ammoniacal nitrogen in their digestate liquor. This article assesses the economic viability and CO2 abatement opportunity from the utilisation of this ammonia under three scenarios and proposes their potential for uptake in the United Kingdom. Each state-of-the-art process route recovers ammonia and uses it alongside AD-produced biomethane for three different end goals: (1) the production of H2 as a bus transport fuel, (2) production of H2 for injection to the gas grid and (3) generation of heat and power via solid oxide fuel cell technology. A rigorous assessment of UK anaerobic and sewage digestion facilities revealed the production of H2 as a bus fleet transport fuel scenario as the most attractive option, with 19 SD and 42 AD existing plants of suitable scale for process implementation. This is compared to 3 SD/1 AD and 13 SD/23 AD existing plants applicable with the aim of grid inje... [more]

Two vehicle chassis design tasks were solved by decomposition-based multi-disciplinary optimisation (MDO) methods, namely collaborative optimisation (CO) and analytical target cascading (ATC). A passive suspension system was optimised by applying both CO and ATC. Multiple parameters of the spring and damper were selected as design variables. The discomfort, road holding, and total mass of the spring−damper combination were the objective functions. An electric vehicle (EV) powertrain design problem was considered as the second test case. Energy consumption and gradeability were optimised by including the design of the electric motor and the battery pack layout. The standard single-level all-in-one (AiO) multi-objective optimisation method was compared with ATC and CO methods. AiO methods showed some limitations in terms of efficiency and accuracy. ATC proved to be the best choice for the design problems presented in this paper, since it provided solutions with good accuracy in a very ef... [more]

We used three-dimensional (3D), high-resolution simulations facilitated by parallel computation to assess the effect of hydrogeological heterogeneity in the Mt. Simon Sandstone on CO2 plume evolution and storage and geochemical reactions in a portion of the Illinois Basin, Indiana. Two scenarios were selected to investigate the effects of the hydrogeological heterogeneity in 3D reactive transport simulations: a heterogeneous case with variable porosity and permeability, and a homogenous case with constant porosity and permeability. The initial pressure, temperature, and mineralogical distributions are consistently applied in both the heterogeneous case and the homogeneous case. Results indicate that including hydrogeological heterogeneity in 3D reservoir simulations for geological CO2 storage significantly impacts modeling results for plume migration patterns, CO2-water-mineral interaction, reservoir quality, and CO2 plume containment. In particular, results indicate that (1) the CO2 p... [more]

Since the quality of the direct and quadrature axis current (dq-axis) is an important performance indicator of a motor, the technique of flux ripple analysis is necessary to determine the appropriate working conditions for various voltage sequences and reduce current fluctuations. However, the traditional flux ripple model cannot analyze dq-axis flux ripples (except under no-load conditions). Therefore, it is unable to calculate the modulation ratio and voltage angle (angle between the reference vector and the q-axis) ranges to satisfy the given q-axis (or d-axis) current fluctuation requirement based on this model. To solve this problem, in this paper, we derived an improved flux ripple model by applying coordinate transformation to the traditional flux ripple model, which can be used to calculate the RMS (root mean square) value of the q-axis and the total flux ripple distribution within sector I under different modulation ratios and voltage angle ranges. The modulation ratio and vol... [more]

A recent survey of cybersecurity assessment methods proposed by the scientific community revealed that their practical adoption constitutes a great challenge. Further research that aimed at identifying the reasons for that situation demonstrated that several factors influence the applicability, including the documentation level of detail, the availability of supporting tools, and the continuity of support. This paper presents the European Energy Information Sharing and Analysis Centre (EE-ISAC)—a cybersecurity platform for the energy sector that has been adopted by multiple organisations. The platform facilitates sharing information about cybersecurity incidents, countermeasures, and assessment results. Prospectively, it is envisaged to be integrated with the threat intelligence platform that enables real-time situational awareness. By considering both fault and attack scenarios together, threat awareness can be mapped onto operational contexts to prioritise decisions and responses. Th... [more]

Partial discharge (PD) sensors have been widely used in PD detection of power equipment. In order to adapt to the development of the new power system, the new PD sensor should not only have a wide response band but also have a large dynamic range. PD measurement devices currently used in smart grids are mainly based on traditional metal materials, which face difficulty in fully meeting these technical requirements. Graphene has a variety of excellent properties, and it is introduced to improve PD sensor materials in this paper. Based on the transmission line model, the circuit parameters of graphene PD sensor electrode plate material are theoretically derived. Various factors affecting its resistance characteristics, inductance characteristics, and capacitance characteristics are analyzed. Next, the variation curves of circuit parameters under different influencing factors are obtained. Linear regression models based on the least-square method were developed for circuit parameters. Fin... [more]