This paper presents a comprehensive study on a novel voltage injection based offline parameter identification method for surface mounted permanent magnet synchronous motors (SPMSMs). It gives solutions to obtain stator resistance, d- and q-axes inductances, and permanent magnet (PM) flux linkage that are totally independent of current and speed controllers, and it is able to track variations in q-axis inductance caused by magnetic saturation. With the proposed voltage amplitude selection strategies, a closed-loop-like current and speed control is achieved throughout the identification process. It provides a marked difference compared with the existing methods that are based on open-loop voltage injection and renders a more simplified and industry-friendly solution compared with methods that rely on controllers. Inverter nonlinearity effect compensation is not required because its voltage error is removed by enabling the motor to function at a designed routine. The proposed method is va... [more]

Improving the heat dissipation ability for light-emitting diode (LED) filament bulb is very difficult. A tri-needle/ring ionic wind generator was developed to improve the heat dissipation condition of bulbs. The operation characteristics of the ionic wind generator, such as the electrode gap, inception voltage, and discharge current with regard to the operation voltage, were studied by experiments. The ionic wind velocity within the bulb was investigated under different electrode gaps and applied voltages. The temperature drop achieved by the ionic was were tested with the consideration of many operation parameters for analysis. The experiments showed that ionic wind can provide efficient and stable cooling effect for LED filament bulbs. The temperature drop of LED junction can reach 30 °C at best. Good stability and adjustability of the ionic wind generator were demonstrated by tracing the temperature history of LED filaments in long-term tests. Finally, the light efficiency of LED fi... [more]

Power-to-gas technology plays a key role in the success of the energy transformation. This paper addresses issues related to the legal and technical regulations specifying the rules for adding hydrogen to the natural gas network. The main issue reviewed is the effects of the addition of hydrogen to natural gas on the durability of diaphragm gas meters. The possibility of adding hydrogen to the gas network requires confirmation of whether, within the expected hydrogen concentrations, long-term operation of gas meters will be ensured without compromising their metrological properties and operational safety. Methods for testing the durability of gas meters applied at test benches and sample results of durability tests of gas meters are presented. Based on these results, a metrological and statistical analysis was carried out to establish whether the addition of hydrogen affects the durability of gas meters over time. The most important conclusion resulting from the conducted study indicat... [more]

The forecasting of solar irradiance in photovoltaic power generation is an important tool for the integration of intermittent renewable energy sources (RES) in electrical utility grids. This study evaluates two machine learning (ML) algorithms for intraday solar irradiance forecasting: multigene genetic programming (MGGP) and the multilayer perceptron (MLP) artificial neural network (ANN). MGGP is an evolutionary algorithm white-box method and is a novel approach in the field. Persistence, MGGP and MLP were compared to forecast irradiance at six locations, within horizons from 15 to 120 min, in order to compare these methods based on a wide range of reliable results. The assessment of exogenous inputs indicates that the use of additional weather variables improves irradiance forecastability, resulting in improvements of 5.68% for mean absolute error (MAE) and 3.41% for root mean square error (RMSE). It was also verified that iterative predictions improve MGGP accuracy. The obtained res... [more]

Adsorption chillers offer an environmentally friendly solution for the valorisation of waste or solar heat for cooling demands. A recent application is high efficiency data centre cooling, where heat from CPUs is used to drive the process, providing cooling for auxiliary loads. The metal organic framework aluminium fumarate with water is potentially a suitable material pair for this low temperature driven application. A targeted heat exchanger design is a prerequisite for competitiveness, requiring, amongst other things, a sound understanding of adsorption equilibria and adsorption enthalpy. A novel method is employed for their determination based on small isothermal and isochoric state changes, applied with an apparatus developed initially for volume swing frequency response measurement, to samples with a binder-based adsorbent coating. The adsorption enthalpy is calculated through the Clausius−Clapeyron equation from the obtained slopes of the isotherm and isobar, while the absolute... [more]

Subscale wind turbines can be installed in the field for the development of wind technologies, for which the blade aerodynamics can be designed in a way similar to that of a full-scale wind turbine. However, it is not clear whether the wake of a subscale turbine, which is located closer to the ground and faces different incoming turbulence, is also similar to that of a full-scale wind turbine. In this work we investigate the wakes from a full-scale wind turbine of rotor diameter 80 m and a subscale wind turbine of rotor diameter of 27 m using large-eddy simulation with the turbine blades and nacelle modeled using actuator surface models. The blade aerodynamics of the two turbines are the same. In the simulations, the two turbines also face the same turbulent boundary inflows. The computed results show differences between the two turbines for both velocity deficits and turbine-added turbulence kinetic energy. Such differences are further analyzed by examining the mean kinetic energy equ... [more]

The aim of the paper is the techno-economic analysis of innovative integrated combined heat and power (CHP) systems for the exploitation of different renewable sources in the residential sector. To this purpose, a biofuel-driven organic Rankine cycle (ORC) is combined with a wind turbine, a photovoltaic system and an auxiliary boiler. The subsystems work in parallel to satisfy the electric and heat demand of final users: a block of 40 dwellings in a smart community. A 12.6 kWel ORC is selected according to a thermal-driven strategy, while wind and solar subsystems are introduced to increase the global system efficiency and the electric self-consumption. The ORC can be switched-off or operated at partial load when solar and/or wind sources are significant. A multi-variable optimization has been carried out to find the proper size of the wind turbine and photovoltaic subsystems and to define the suitable operating strategy. To this purpose, several production wind turbines (1.0−60.0 kWel... [more]

Waterflooding is a common recovery method used to maintain reservoir pressure and improve reservoir oil sweep efficiency. However, injecting cold water into a reservoir alters the state of in-situ formation stress and can result in the formation fracturing. In other words, it can cause the initiation and growth of thermally induced fractures (TIFs), even when the original fracture propagation pressure is not exceeded. TIFs can cause non-uniform distribution of the fluid flow in wellbores, a reduction in sweep efficiency, and early water breakthrough in nearby production wells. Modelling and history matching workflows that consider the dynamic nature of the TIF problem are critical. These workflows improve and validate reservoir and geomechanical models, identify and confirm observed TIF onset and propagation periods, and provide a history-matched sector model with the rock mechanical and thermal properties and stress gradients that can be used with confidence for subsequent studies. Mo... [more]

In this paper, we present the problem of gas and dolomite outbursts in copper mines. The energy balance of the phenomenon is analyzed. An examination of the porosity of the dolomites is performed; in addition, the content and pressure of the gas accumulated in the pore structure of the rock are determined. The gas energy accumulated in the pore space of rocks is determined depending on the transformation occurring during gas decompression. The work needed to crush the rock for the grain distribution characteristic of post-outburst masses is examined. The gas energy needed to transport rocks is analyzed. The purpose of the research is to determine the limit values of parameters describing the gas and rock system for which there is a risk of dolomite and rock explosions. For the characteristic porosity of dolomites of −5%, gas and rock outbursts at 5 MPa pressure in isothermal transformation can be expected, and if the transformation is closer to adiabatic transformation, outbursts can b... [more]

The article presents the impact of geological and mining factors on the stability of room excavations in the Legnica-Głogów Copper District (LGOM) in Poland. In underground mining, the primary task of bolting of mining excavations is to ensure their stability as an essential condition of work safety. Appreciating the role and importance of the rock bolting in Polish ore mining; rock bolt load sensors were designed, manufactured and tested under laboratory conditions. The purpose of the research was to characterize the sensors and determine the elastic range of the bearing plate, which are an integral part of the sensor. The sensors have been verified in industrial conditions. The tests were carried out in the underground copper ore mine in Poland. Three rooms in the exploitation field were selected for testing, where exploitation was carried out at a depth of 809−820 m below the ground surface with the application of room and pillar with roof deflection and maintaining the central part... [more]

In this study, the electrical, electrochemical and thermodynamic performance of a PV/T electrolyzer system was investigated, and the experimental results were verified with a numerical model. The annual amounts of electrical and thermal energy from the PV/T electrolyzer system were calculated as 556.8 kWh and 1912 kWh, respectively. In addition, the hydrogen production performance for the PV/T electrolyzer was compared with that of a PV electrolyzer system. The amount of hydrogen was calculated as 3.96 kg annually for the PV system, while this value was calculated as 4.49 kg for the PV/T system. Furthermore, the amount of hydrogen production was calculated as 4.59 kg for a 65 °C operation temperature. The electrical, thermal and total energy efficiencies of the PV/T system, which were obtained hourly on a daily basis, were calculated and varied between 12−13.8%, 36.1−45.2% and 49.1−58.4%, respectively. The hourly exergy analyses were also carried out on a daily basis and the results sh... [more]

The increasing demand for energy and the impacts generated by CO2 emissions make it necessary to harness all possible renewable sources of energy, like wave power. Nevertheless, climate change may generate significant variations in the amount of wave energy available in a certain area. The aim of this paper is to study potential changes in the wave energy resource in the Mediterranean coast of Morocco due to climate change. To do this, wave datasets obtained by four institutes during the Coordinated Regional Climate Downscaling Experiment in the Mediterranean Region (Med-CORDEX) project are used. The future conditions correspond to the RCP4.5 and RCP8.5 scenarios from the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. The results show that projected future wave power is very similar to that of the present considering the whole area, although at some specific points there are slight changes that are more evident for the RCP8.5 scenario. Another remarkable resu... [more]

The continued use of nuclear energy has come into question due to the difficulties in managing radioactive waste, and public opposition has increased since the Fukushima nuclear disaster in March 2011. Nonetheless, the novel spent nuclear fuel (SNF) management technologies proposed indicate new pathways toward facilitating the environment and the sustained use of nuclear energy. The reprocessing and recycling of SNF provides an alternative to direct geological disposal. In this article, we examine the current status and strategic alternatives of radioactive waste management in Taiwan.

Alternative fuel within the meaning of Directive 2014/94/EU is, among others, LPG (liquefied petroleum gas), characterized by a lower purchase cost and lower emissions of toxic exhaust compounds in comparison to the combustion of classic gasoline. In wood chippers, intended for chopping branches, with low-power internal combustion engines that meet the emission standards in force in 2019 in the European Union, in accordance with Regulation 2016/1628/EU, carburetor fuel supply systems are commonly used. Innovative trends in the development of these drives are: electronic fuel injection, systems supporting the adaptation of the working elements to the conditions of use and the use of alternative fuels. The first two solutions significantly affect the cost of purchasing a power unit or modernizing it. The authors of this article indicate, as a beneficial alternative, a cheap (EUR 105) possibility of modernizing the carburetor fuel supply system. It is based on a modification that will all... [more]

To date, to simulate biodiesel production, kinetic models from different authors have been provided, each one usually applied to the use of a specific vegetable oil and experimental conditions. Models, which may include esterification, besides transesterification simulation, were validated with their own experimental conditions and raw material. Moreover, information about the intermediate reaction steps, besides catalyst concentration variation, is either rare or nonexistent. Here, in this work, a universal mathematical model comprising the chemical kinetics of a two-step (esterification and transesterification) vegetable oil-based biodiesel reaction is proposed. The proposed model is universal, as it may simulate any vegetable oil biodiesel reaction from the literature. For this purpose, a mathematical model using the software MATLAB has been designed. Using the mathematical model, the estimation of mass variation with time, of both reactants and products, as well as glyceride conver... [more]

In this work, a control strategy is developed for different components in DC microgrids where set points for all controllers are determined from an energy management system (EMS). The proposed EMS-based control scheme is developed for DC microgrids with solar photovoltaic (PV) systems as the primary generation units along with energy storage systems. In this work, the concept of dual energy storage systems (DESSs) is used, which includes a battery energy storage system (BESS) and supercapacitor (SC). The main feature of this DESS is to improve the dynamic performance of DC microgrids during severe transients appearing from changes in load demands as well as in the output power from solar PV units. Furthermore, the proposed EMS-based control scheme aims to enhance the lifetime of the BESS in DC microgrids with DESSs and voltage stability as compared to the same without SCs. The proposed EMS-based control strategy uses proportional-integral (PI) controllers to regulate the switching cont... [more]

A thermo-economic analysis of a regenerative dual-loop organic Rankine cycle (ORC) is conducted, which will be coupled with the main diesel engines of a general support vessel. An energy and exergy analysis of the regenerative dual-loop ORC is conducted. The energy and exergy analysis results of the regenerative dual-loop ORC are compared with pertinent results for a simple dual-loop ORC without regeneration. A mission analysis that was based on a vessel speed profile with the proposed ORC was conducted. A heat transfer analysis was performed for dimensioning the heat exchangers of both ORC loops. Finally, an economic analysis is conducted to calculate the total capital cost and the payback period of the proposed ORC. The results showed that the proposed ORC is thermodynamically superior in both energetic and exergetic terms compared to the simple dual-loop ORC. The total fuel cost saving is 337,493 Euros, the total CO2 emission saving is 1,153,416.4 kg, and the SO2 emission saving is... [more]

The water-supply system is one of the basic and most important critical infrastructures. Water supply service disruption (water quality or quantity) may have serious consequences in modern societies. Water supply service is subject to various failure modes. Failure modes are specified by their degradation mechanisms, criticality, occurrence frequency and intensity. These failure modes have a random nature that impacts on the network disruption indicators, such as disruption frequency, network downtime, network repair time and network back-to-service time, i.e., the network resilience. This paper focuses on the water leakage failure mode. The water leakage failure mode assessment considers the unavoidable annual real water losses and the infrastructure leakage index recommended by the International Water Association’s Water Loss Task Force specialist group. Probabilistic statistical modelling was implemented to assess the seasonal index, the failure rates and the expectation value of th... [more]

Nowadays, LED lamps have become a widespread solution in different lighting systems due to their high brightness, efficiency, long lifespan, high reliability and environmental friendliness. The choice of a proper LED driver circuit plays an important role, especially in terms of power quality. In fact, the driver controls its own input current in addition to the LED output current, thus it must guarantee a high power factor. Among the various LED drivers available on the market, the quasi-resonant (QR) flyback topology shows interesting benefits. This paper aims at investigating and analyzing the different issues related to the input current distortion in a QR flyback LED driver. Several effects, such as the distortion caused by the ringing current, crossover distortion due to transformer leakage inductance and crossover distortion due to the input storage capacitor have been experimentally reported. These effects, not previously studied for a high power factor (Hi-PF) QR flyback, have... [more]

This paper presents research on humidity in a passenger car cabin with the use of supply ventilation without cooling the air. Based on the tests carried out and the humidity balance in the car, a model was developed for changing the humidity in the passenger car cabin as a function of time. The study of thermohumid conditions was carried out in two passenger cars. During the tests, the heating and cooling functions were turned off. The relative humidity and temperature were measured outside the car before and after driving the car and in the supply air duct and inside the passenger car cabin while driving the car. The tests were carried out for an average temperature range from 20 to 42.9 °C. In order to develop a model of humidity changes as a function of time, a humidity balance was prepared. Human-generated humidity in the car cabin depends mainly on the temperature inside the car and the age of the person and can range from 20 to 180 g/(h × person) for an adult in the temperature r... [more]

The aim of this publication is to review the current state and possibilities of developing electromobility and alternative fuels in Poland. It was found that the current market for alternative fuels in Poland is insufficiently developed. At the end of 2019 in Poland, liquefied petroleum gas-powered cars accounted for approximately 3.3 million pieces, which amounts to 14.3% all passenger vehicles up to 3.5 tonnes of gross vehicle weight. There were over 9000 electric cars on the road, the share of which accounted for 0.04% of domestic passenger transport. The lack of a sufficient number of charging points, inhibiting the development of electromobility, was also noted. There were approximately 4000 (0.02%) passenger cars powered by compressed natural gas. Liquefied gas-powered vehicles were exclusively public transport vehicles or trucks. The share of biofuels in the Polish transport sector stands at 4%, while European Union requirements are at a level of 10%. Although there is huge pote... [more]

Literature and experience show that there are large discrepancies between the calculated and measured building energy usages, where user-related parameters are significant factors with regard to energy use in low-energy buildings. Furthermore, the difficulties encountered when quantifying these parameters compound these discrepancies. The main aim of this study was to provide feedback that would help the building industry and research communities to predict more accurately the impact of the user-related parameters on energy performance. The results of the study would, subsequently, contribute to minimizing the discrepancies between calculated and measured energy use. This article analyses simulated building energy use based on randomly chosen combinations of measured user-related parameters in three recently built low-energy schools in Sweden. The results show that energy performance can span from 30 to 160 kWh/(m² y) simply by varying the combination of previously measured user-relate... [more]

The robustness of the reference circuit in a wide range of supply voltages is crucial in implanted devices. Conventional reference circuits have demonstrated a weak performance over wide supply ranges. Channel-length modulation in the transistors causes the circuit to be sensitive to power supply variation. To solve this inherent problem, this paper proposes a new output-voltage-line-regulation controller circuit. When a variation occurs in the power supply, the controller promptly responds to the supply deviation and removes unwanted current in the output path of the reference circuit. The proposed circuit was implemented in a 0.35-μm SK Hynix CMOS standard process. The experimental results demonstrated that the proposed reference circuit could generate a reference voltage of 0.895 V under a power supply voltage of 3.3 V, line regulation of 1.85 mV/V in the supply range of 2.3 to 5 V, maximum power supply rejection ratio (PSRR) of −54 dB, and temperature coefficient of 11.9 ppm/°C in... [more]

DC distribution grids are increasingly a promising solution for wind and solar integration due to good matching with DC output voltage such as photovoltaic (PV) array systems, distributed battery storage systems (BESS) and electric vehicles. To overcome the control problems involving coordination control schemes of multi-BESSs in real-time as well as operation strategies of DC grids in the long-term, this paper presents the effective adaptive coordinated droop control of multi-battery energy storage systems (MBESSs) in DC distribution grids. The adaptive coordinated droop is proposed according to the available energy levels in BESSs. With the proposed method, the dual-objectives, which are stabilization of DC voltages especially through disturbance for instance outage of BESS and enhancement of State of Charge (SOC)-balance speed among BESSs, can be achieved. Analytical derivations are established to investigate the impacts of the adaptive method. Meanwhile, the influence of the propos... [more]

The energy transformation is changing the structure of the energy sector in Europe and Germany. In this paper the current structure of the energy sector is analysed both empirically as well as theoretically. Therefore, the authors have developed the business model framework for the energy transformation (BMFE). The framework is a synthesis of classical business model designs. An exhaustive survey of existing business models based on primary data collection and a literature review leads to 638 business models. Finally, 69 prototypical business models of the energy sector are the result of the classification of these business models. The information of the business models within the BMFE is applied to show the growing importance of value creation networks in energy industry. The work represents the current status of the business models in the energy sector.