ALBERT

Description: Horizontal wells can significantly improve the gas production and are expected to be an efficient exploitation method for the industrialization of natural gas hydrates (NGHs) in the future. However, the near-wellbore hydrate is highly prone to decomposition during the drilling process, owing to the disturbance aroused by the factors such as the drilling fluid temperature, pressure, and salinity. These issues can result in the engineering accidents such as bit sticking and wellbore instability, which are required for further investigations. This paper studies the characteristics of drilling fluid invasion into the marine NGH reservoir with varied drilling fluid parameters via numerical simulation. The effects of the drilling fluid parameters on the decomposition behavior of near-wellbore hydrates are presented. The simulating results show that the adjustments of drilling fluid density within the mud safety window have limited effects on the NGH decomposition, meanwhile the hydrates reservoir is most sensitive to the drilling fluid temperature variation. If the drilling fluid temperature grows considerably due to improper control, the range of the hydrates decomposition around the horizontal well tends to expand, which then aggravates wellbore instability. When the drilling fluid salinity varies in the range of 3.5–7.5%, the increase in the ion concentration speeds up the hydrate decomposition, which is adverse to maintaining wellbore stability.

Description: The electric power industry sector has become increasingly aware of how counterproductive voltage sag affects distribution network systems (DNS). The voltage sag backfires disastrously at the demand load side and affects equipment in DNS. To settle the voltage sag issue, this paper achieved its primary purpose to mitigate the voltage sag based on integrating a hydrogen fuel cell (HFC) with the DNS using a distribution static synchronous compensator (D-STATCOM) system. Besides, this paper discusses the challenges and opportunities of D-STATCOM in DNS. In this paper, using HFC is well-designed, modeled, and simulated to mitigate the voltage sag in DNS with a positive impact on the environment and an immediate response to the issue of the injection of voltage. Furthermore, this modeling and controller are particularly suitable in terms of cost-effectiveness as well as reliability based on the adaptive network fuzzy inference system (ANFIS), fuzzy logic system (FLC), and proportional–integral (P-I). The effectiveness of the MATLAB simulation is confirmed by implementing the system and carrying out a DNS connection, obtaining efficiencies over 94.5% at three-phase fault for values of injection voltage in HFC D-STATCOM using a P-I controller. Moreover, the HFC D-STATCOM using FLC proved capable of supporting the network by 97.00%. The HFC D-STATCOM based ANFIS proved capable of supporting the network by 98.00% in the DNS.

Description: Apart from numerous technical challenges, the transition towards a carbon-neutral energy supply is greatly hindered by limited economic feasibility of renewable energy sources. This results in their slow and bounded penetration in both commercial and residential sectors that are responsible for over 40% of final energy consumption. This paper aims to demonstrate that combined application of sophisticated planning methodologies at building-level and presents incentive mechanisms for renewables that can result in prosumers, featuring hybrid renewable energy systems (HRES), with economic performance comparable to that of conventional energy systems. The presented research enhances existing planning methodologies by integrating appliance-level demand side management into the decision process and investigates its effect on the planning problem. Moreover, the proposed methodology features an innovative and holistic approach that simultaneously assess electrical and thermal domain in both an isolated and grid-connected context. The analyzed hybrid system consists of solar photovoltaic, wind turbine and battery with thermal supply featuring solar thermal collector and a ground-source heat pump. Overall optimization problem is modeled as a mixed-integer linear program, while ranking of all feasible alternatives is made by the multicriteria decision-making algorithm against several technological, economic, and environmental criteria. A real-life scenario of energy system retrofit for a building in the United Kingdom was employed to demonstrate overall cost savings of 12% in the present market and regulation context.

Description: In the EU 28, the installed heating appliance stock is quite old, with an actual replacement rate of 4%. This is directly reflected in the average efficiency of the installed heating systems, where around 60% of the stock is rated with an energy class of C or D (the lowest classes of the energy label scale). The European project HARP aims at raising consumers’ awareness of the planned replacement of their old and inefficient heating appliances with more efficient and renewable solutions. In this direction, an energy labeling methodology for old appliances has been developed to rate the installed stock before the introduction of the EU energy label. The methodology has been developed for space heating appliances and water heaters, targeting two types of users: end consumers and professional users. The validation considered about 4600 space heating appliances and 800 water heaters built between 1972 and 2019. Three heating appliances and two water heaters were tested in the laboratory, confirming the reliability of the proposed methodology. The expected impact of defining an energy labeling methodology for installed heating appliances increases the current replacement rate of these appliances in the EU from 4% to 5%.

Description: This work presents a comprehensive theoretical analysis of current-mode power amplifiers as a function of input power for different biasing classes under the common simplifying assumption of constant transconductance and hard current cut-off/saturation. Typically, the theoretical analysis of power amplifier performance and behavior are carried out only at maximum output power. However, to achieve high data-rates, modern telecommunication systems adopt signals characterized by a very high peak-to-average power ratio, thus it is useful to analyze the power amplifier behavior as a function of power back-off. Moreover, in many cases, to enhance the efficiency and/or to apply harmonic shaping techniques, a clipped drain-source current, which approaches a square wave, is required. The classical analysis can be extended to low power levels only under the assumption of power-independent conduction angle, which is true only for class-A and class-B amplifiers, and does not take into account possible waveform clipping at maximum current. This work presents a complete theoretical Fourier analysis of FET-based power amplifiers as a function of quiescent drain-source current at any input power level and accounting for the clipped current case, up to the square-wave limit, reorganizing and completing the material that can be found in classical textbooks in the field.

Description: Contemporary agriculture has become very energy-intensive and mainly uses electricity, which is needed for technological processes on livestock farms. Livestock faeces are burdensome for the environment due to the release of methane into the atmosphere. This article presents the concept of a self-sufficient livestock farm as an off-grid energy circuit that is a part of the agricultural process. The key idea is to obtain an energy flow using the concept of a smart valve to achieve a self-sufficient energy process based on a biogas plant, renewable energy sources, and energy storage. During the production process, a livestock farm produces large amounts of waste in the form of grey and black manure. On the one hand, these products are highly harmful to the environment, but on the other, they are valuable input products for another process, i.e., methane production. The methane becomes the fuel for cogeneration generators that produce heat and electricity. Heat and electricity are partly returned to the main farming process and partly used by residents of the area. In this way, a livestock farm and the inhabitants of a village or town can become energy self-sufficient and independent of national grids. The idea described in this paper shows the process of energy production combining a biogas plant, renewable energy sources, and an energy storage unit that enable farmland to become fully self-sufficient through the energy flow between all constituents of the energy cycle being maintained by a smart valve.

Description: Due to the complex and variable conditions under which wind turbines operate, existing working condition classification methods are inadequate for condition assessment of the main transmission system. Because working conditions are too few after classification, it cannot effectively describe the complex and variable working conditions of wind turbine. This can lead to high false-alarm rates in the condition monitoring, which affect normal operations. This paper proposes a working condition classification method for the main transmission system of wind turbines based on supervisory control and data acquisition (SCADA) data. Firstly, correlation analysis of SCADA data acquired by wind farm is used to select the parameters relevant to the main transmission system. Secondly, according to the wind turbine control principle, the working conditions are initially divided into four phases: shutdown, start-up, maximum wind energy tracking, and constant speed. The k-means clustering algorithm is used to subdivide the maximum wind energy-tracking phase and constant speed phase, which account for a larger proportion of the working conditions, to achieve better classification. Finally, a case study is used to demonstrate the calculation of alarm thresholds and alarm rates for each working condition. The results are compared with the direct use of k-means clustering for working condition classification. It is concluded that the proposed method can significantly reduce the false-alarm rate of the vibration detection process.

Description: The use of polymer composite materials in the aeronautics and automotive sectors has increased dramatically, and their fire behaviour has become a critical parameter in terms of fire safety. On this premise, it is critical to demonstrate that these composite materials constitute elements whose safety justifies a high level of confidence. This is based on their combustibility and the rate at which flammable and toxic gaseous species are emitted. Thus, strict fire safety regulations are enforced by the relevant authorities concerned because of their potential fire risk. This study analysed papers published between 1970 and 2021 that described the devices used to characterise the thermal behaviour of composite materials at various scales. The objective was to highlight the thermophysical phenomena, making it possible to accurately assess the flammability and thermal stability of polymer composite materials. The results of this research reveal that the small-scale facilities provide detailed understanding and mastery of the thermal reaction properties of the composites. While with the medium scale, the extended fire reaction parameters, which are the key indicators of the fire safety performance, can be determined. On a large scale, the tests were carried out using devices such as the NexGen burner recommended by the FAA. Therefore, with such assays, it is possible to assess the rates of thermal degradation as well as quantified pyrolysis gases. However, compared to other scales, there were very few works on a large scale. In addition, by focusing on the polluting nature of synthetic composite materials, there is also few research studies aimed at designing new polymer composite materials from biological sources.

Description: This paper deals with the applicability of alternative power system configurations to reduce the environmental footprint of inland waterway ships. Its original contribution includes: models for assessment of the lifetime emissions and associated lifetime costs of alternative power system configurations for different types of inland waterway vessels, identification of the most cost-effective options for these vessels, and an estimation of the impact of emission policies on the profitability of each option. The case study considers the Croatian inland waterway sector, where three types of vessel with significantly different purposes, designs, and operative profiles are considered (cargo ship, passenger ship, and dredger). The technical and operational features of these ships are analyzed with an emphasis on their energy needs. Then, life-cycle assessments (LCAs) of a diesel engine-powered ship configuration and two battery-powered ship configurations (with and without a photovoltaic system) are performed by means of GREET 2020 software. These configurations are compared from the economical viewpoint, by the life-cycle cost assessment (LCCA), where potential carbon credit scenarios are investigated, while relevant quantities are converted into monetary units. Although the LCA identified the photovoltaic cells’ battery-powered ship configuration as the most environmentally friendly, according to the LCCA, its life-cycle costs are rather high, except for passenger ships, for which the battery-powered ship configuration is a feasible option. If a set of required specific input data is known, the presented procedure is applicable to reduce the environmental footprint of any other inland waterway fleet.

Description: In the case of the inductive voltage transformer (VT), the resonance phenomenon may be the main reason for its poor transformation accuracy of the non-sinusoidal voltage. This problem mainly results from the leakage inductance and the parasitic capacitance of its primary winding. The application of the sinusoidal voltage with a frequency from 20 Hz to 20 kHz presented in this study ensures proper identification of the resonance frequencies of the medium-voltage (MV) inductive VTs. The results are consistent with the values obtained in the reference condition at their nominal primary voltage. Therefore, it is proven that the proposed solution is effective in all cases. The influence of the main frequency variation of the non-sinusoidal primary voltage on the resonance properties of the inductive VT is also studied. Moreover, the tests indicate that the capacitance of the load of the secondary winding may cause a decrease in their resonance frequency.