This paper studies the influence of different cooling technologies on the power density of a traction machine for heavy-duty distribution transport. A prototype induction machine is built with a housing cooling jacket, potted end-windings, entire winding cooling, and shaft cooling. Electromagnetic finite element and thermal lumped-parameter models are parameterized and verified using test bench measurements. The influence of each thermal resistance along the heat paths is studied and discussed. The results are used for studying different cooling technologies. The results indicate an improvement of the continuous power density up to 108% using shaft cooling and up to 15.6% using entire winding cooling.

The paper introduces a comprehensive investigation in end winding inductances of large two-pole turbo-generators. With the aid of an analytic-numeric approach, where Neumann's formula is applied, the influence of geometric characteristics of double-layer stator end windings with involute shape is analysed. This parameter study results in approximation formulas for the stator self and mutual inductances at stand level as well as for the common used end winding leakage inductance. In order to consider field affecting components as pressure plate, flux shield, rotor shaft and rotor retaining ring, finite elements models for two machines (250 MVA and 1150 MVA) are created and computed. The results are integrated in the developed approximation formulas. Finally the simulation results of machine 1 are compared to the data of two different measurements. All approaches introduced in this paper show good correlation. The high speed of the analytic-numeric calculation is combined with the accuracy and opportunity to consider field affecting components within the extensive finite element computation successfully.

On power generation and the future of Polish offshore wind farms.

In the paper, the author presents a certain method of calculation of Horizontal Axis Wind Turbine (HAWT) performance for yawed flow conditions. The presented model is developed on the basis of propeller theory described in [23). Te model employs the results of the vortex theory of propeller combined with momentum and angular momentum theorems for the HAWT wake. In the model, the blade element is regarded as a source of tangential and axial force acting on air at actuator disk surface. The momentum equations are corrected for the effect of finite number of blades by introduction of Prandtl tip-loss factor to the equations. Thanks to the approximation of lift force coefficient vs. angle of attack by sine curve, one may get a quadratic equation for local axial velocity component. Tangential component of induced velocity may be calculated from relations obtained from vortex theory of HAWT. This allows us to avoid an iterative solution for induced velocity, unlike in most of the HAWT and propeller theories. The blade section drag is incorporated to calculations of total drag of rotor and power, when induced velocity components are known, and hence blade element angle of attack is determined. To incorporate the effect of blade element stall-delay due to blade rotation, a simple semi-empirical model proposed by Tangier and Selig has been applied. The calculations are compared with experimental data obtained at Riso 100 kW experimental turbine test site and at the Grumman Wind Stream 33 turbine modified by NREL. The comparison includes power output as well as blade element angles of attack. The presented results show that the method described in the paper underestimates performance for low speed winds, whereas for strong winds the power output is slightly overestimated. For average angles of attack, one may see that for small tip speed ratios angles of attack are overestimated. At high tip speed ratios, however, angles of attack are underestimated. It was shown that there is a need to take into account the work done by side force on the tangential inflow component to obtain correct power curves for yawed flow conditions.

This paper presents the design method and the construction details of a subsonic low-speed wind tunnel, which has been designed to achieve the flow velocity of 35 m/s in the measurement section with expected uniform velocity field at its inlet. To achieve such objectives a very detailed design was performed using a theoretical 1D analysis and computational fluid dynamics simulations. This approach was applied to improve the flow quality along the wind tunnel sections. When the wind tunnel has been launched a direct comparison of the experimentally measured flow field in the test section and numerical simulation results was conducted. Such comparison of the simulation results with the experimental one is presented in this paper. The obtained results confirm that assumed wind tunnel design method was correct, i.e. the pressure drop in the wind tunnel has been predicted very well and drive system is effective and sufficient to accelerate the airflow to required values.

Eurocode standard recommends using fundamental basic wind velocity (characteristic velocity) as the design value in civil engineering. There are different approaches to estimate this value depending on the climate features of the given area and the quality of environmental data. The estimation of the characteristic value requires statistical analysis of historical data regarding wind velocities measured throughout the country at meteorological stations. The results of the analysis are probability density distributions of this random variable for each meteorological station. On this basis, values of characteristic wind velocity with a mean return period of 50 years are determined. The zones with uniform velocities are delineated on the map of the country. In the case of Poland the last evaluation of wind zones took place over 15 years ago. Higher quality of measurement data on the one hand, and the introduction of the second generation of Eurocode standards on the other hand, create a need to check and update these zones. This work presents theoretical basis for the estimation of characteristic values of random variables in the context of wind velocity, comprehensively reviews practical methods used for this purpose and summarizes current situation in Poland, finally discusses the issues related to the heterogeneity of wind data, illustrating them with an example.

On the basis of 35 one-hour series of the measurement of the wind velocity, read out every two minutes, the wind structure at the Arctowski Station, situated on Admiralty Bay, King George Island, was analysed. Very strong turbulence was found with air flow directions from over the area of the Island (S, SW. W and NW) and laminarity with directions from SE, E, NE and partly N, i.e. when the air flows from Admiralty Bay or from over the open waters of Bransfield Strait. The qustiness coefficient, the relationship between the maximum and mean velocities and the intensity of turbulence were determined for the two flow types. Two extremely different cases, in terms of flow character, were considered, by determining for them the distributions of instantaneous velocities and those of oscillations.

Power spectrum techniques were applied to two time series of wind speed values recorded at the Arctowski Station in order to investigate the influence of turbulent and laminar air flow on the quasi-periodicity of the micro-scale wind structure.

The analysis of speed and direction distribution of upper wind in the layer up to 3500 m was carried out on the basis of pibal ascents performed over the Admiralty Bay (King George Island, South Shetland Islands).

The transfer function (TF) method is presently a well-known method used to detect various types of winding damage in power transformers. Although abundant research has been done on this subject using laboratory windings as test objects, it is hard to find one, whose test objects are actual large-power transformer windings. Hence, a 400 kV disc winding consisting of 86 discs is used in this paper to study turn-to-turn short circuit with the help of the TF method. To evaluate the effects of this type of fault on TF curves, some mathematical comparison algorithms are used in this research.

This paper aims to present a new equivalent scheme of multi-windings traction transformers, based on multiport purely inductive circuit. The mathematical background of this equivalent scheme is described. The determination of the different scheme elements is made through a finite-elements calculation of both main and leakage inductances, for the case of a four-winding transformer. A procedure is defined, which allows to estimate the values of these elements from some measurements on the transformer at no-load and short-circuit operations. A specific strategy of short-circuit tests is described, allowing to determine all parameters in a rather simple way.

Comparison of the electromagnetic performance of a flux-switching permanent magnet (PM) machine having two separate stators as well as different winding topologies is investigated in this paper. Different stator and rotor pole combinations of these machines are also considered. The analysis includes the open-circuit and on-load characteristics of the analyzed machines. It is observed that, the largest fundamental values of electromagnetic torque, for each winding topology, is seen in the 11-rotor-pole and 10-rotor-pole machines having alternate- and all-pole-wound configurations, respectively. Moreover, significant ripple is observed in the waveforms of the even-number rotor pole machines compared to their corresponding odd-number rotor pole counterparts. Overall, the alternate-pole-wound machines essentially have larger torque-density than their equivalent all-pole-wound ones. The investigated machine is also tested for validation.

A comprehensive comparison of the dynamic and steady state performance characteristics of permanent magnet synchronous motors (PMSM) with interior and surface rotor magnets for line-start operation is presented. The dynamic model equations of the PMSM, with damper windings, are utilized for dynamic studies. Two typical loading scenarios are examined: step and ramp loading. The interior permanent magnet synchronous motor (IPMSM) showed superior asynchronous performance under no load, attaining faster synchronism compared to the surface permanent magnet synchronous motor (SPMSM). With step load of 10 Nm at 2 s the combined effect of the excitation and the reluctance torque forced the IPMSM to pull into synchronism faster than the SPMSM which lacks saliency. The ability of the motors to withstand gradual load increase, in the synchronous mode, was examined using ramp loading starting from zero at 2 s. SPMSM lost synchronism at 12 s under 11 Nm load while the IPMSM sustained synchronism until 41 seconds under 40 Nm load. This clearly suggests that the IPMSM has superior load-withstand capability. The superiority is further buttressed with the steady state torque analysis where airgap torque in IPMSM is enhanced by the reluctance torque within 90E to 180E torque angle.

In this paper the mathematical model of the brushless DC motor (BLDCM) with a double 3-phase stator winding is analysed. Both the 3-phase windings are mutually displaced by 30 electrical degree. Special care has been sacrificed to influence of higher harmonics of induced electromotive forces (EMF) on electromagnetic torque and zero sequence voltages that may be used for sensorless control. The mathematical model has been presented in natural variables and, after transformation to symmetrical components, in a vector form. This allows, from one side, for formulating the equivalent circuit suitable for circuit oriented simulators (e.g.: Spice, SimPowerSystems of Simulink) and, from the other point of view, for analysis of higher harmonics influence on control possibilities. These considerations have been illustrated with some results of four quadrant operation obtainded due to simulation at automatic control.

This paper presents a finite element investigation into the proximity losses in a high-speed permanent magnet (PM) machine for traction applications. A three-dimensional (3D) finite element analysis (FEA) is employed to evaluate and identify the endwinding contribution into the overall winding power loss generated. The study is focused on the end-winding effects that have not been widely reported in the literature. The calculated results confirm that the end-winding copper loss can significantly affect the eddycurrent loss within copper and it should be taken into account to provide reasonable prediction of total losses. Several structures of the end-winding are analyzed and compared in respect to the loss and AC resistance. The results clearly demonstrate that the size of the end-winding has a significant impact on the power loss. The calculated results are validated experimentally on the high-speed permanent magnet synchronous machine (PMSM) prototype for selected various winding arrangements.

A high performance and light-weight wound composite material wheel has been developed and is intended to be used for many purposes. One of these applications is marine current turbine (MCT). Traditionally, major problems influencing the design and operation of MCTs are fatigue, cavitation and corrosion due to the sea water. Considering these factors, implementation of composite materials, especially Kevlar fiber/epoxy matrix, in MCTs is explained in this paper. This novel design pattern of composite material marine current turbine (CMMCT) shows many advantages compared to conventional turbines. This paper investigated several factors which should be considered during this novel turbine design process such as the composite material selection, filament winding of composite wheel and turbine's structural and cavitation analysis. The power coefficient of CMMCT by using CFD is also obtained and the experimental facilities for testing CMMCT in a water towing tank are briefly described.

By means of small wind turbines, it is possible to create distributed sources of electricity useful in areas with good wind conditions. Sometimes, however, it is possible to use small wind turbines also in areas characterized by lower average wind speeds during the year. At the small wind turbine design stage, various types of technical solutions to increase the speed of the wind stream, as well as to optimally orientate it, can be applied. The methods for increasing the efficiency of wind energy conversion into electricity in the case of a wind turbine include: the use of a diffuser shielding the turbine rotor and the optimization of blades mounted on the turbine rotor. In the paper, the influence of the diffuser and rotor blades geometry on the efficiency of an exemplary wind turbine for exploitation in the West Pomeranian Province is investigated. The analyses are performed for three types of the diffuser and for three types of rotor blades. Based on them, the most optimal shapes of the diffuser and blades are selected due to the efficiency of the wind turbine. For the turbine with the designed diffuser, calculations of the output power for the assumed different values of the average annual wind speed and the constant Betz power factor and the specified generator efficiency are made. In all the analyzed cases, the amount of energy that can be generated by the turbine during the year is also estimated. Important practical conclusions are formulated on the basis of these calculations. In the final part of the paper, a 3D model of the wind turbine with the diffuser and rotor blades chosen based on earlier analyses is presented. As a material for the diffuser and rotor blades, glass fiber type A is applied. By means of calculations using the finite element method, the limit displacement of the turbine structure under the influence of a hurricane wind are determined. Based on these calculations, the correctness of the modelled small wind turbine structure has been demonstrated.

This article considers designing of a renewable electrical power generation system for self-contained homes away from conventional grids. A model based on a technique for the analysis and evaluation of two solar and wind energy sources, electrochemical storage and charging of a housing area is introduced into a simulation and calculation program that aims to decide, based on the optimized results, on electrical energy production system coupled or separated from the two sources mentioned above that must be able to ensure a continuous energy balance at any time of the day. Such system is the most cost-effective among the systems found. The wind system adopted in the study is of the low starting speed that meets the criteria of low winds in the selected region under study unlike the adequate solar resource, which will lead to an examination of its feasibility and profitability to compensate for the inactivity of photovoltaic panels in periods of no sunlight. That is a system with fewer photovoltaic panels and storage batteries whereby these should return a full day of autonomy. Two configurations are selected and discussed. The first is composed of photovoltaic panels and storage batteries and the other includes the addition of a wind system in combination with the photovoltaic system with storage but at a higher investment cost than the first. Consequently, this result proves that is preferable to opt for a purely photovoltaic system supported by the storage in this type of site and invalidates the interest of adding micro wind turbines adapted to sites with low wind resources.

International scales describing the intensity of tornadoes are investigated along with reports from the Polish Government Security Centre on all types of wind storms in Poland. Then, collected tornado reports for the years 1899–2019 in Poland, a set of the annual maximum gust wind speeds measured at 39 meteorological stations from 1971 to 2005 (35 years), descriptions of Poland’s strongest wind storms in the 21st century, estimating the risk of significant strong and extreme winds in Poland, and classification of maximum wind speeds by Lorenc (2012) are presented. Based on these data, i.e. measured and estimated wind speeds, this paper proposes two separate intensity scales to categorize synoptic, thunderstorm, and downslope winds (in the Tatra and Karkonosze regions), derechos, tornadoes, and downbursts, i.e. all types of wind storms. These scales are simpler than the one put forward by Lorenc (2012). These two scales cover a range of maximum wind speeds from 20 to 90 m/s. This proposal is only applicable to Poland. Other countries may determine whether it applies to them.

Pollution continues to experience a rapid increase so cities in the world have required the use of renewable energy. One of the keys that can prevent climate change with a sustainable system is renewable energy. Renewable energy production, especially for hybrid systems from biomass and wind, is the objective of the analysis in this work. The potential of feedstock for different biofuels such as bio-diesel, bio-ethanol, bio-methane, bio-hydrogen, and biomass is also discussed in this paper. The sustainability of the energy system for the long term is the main focus of work in this investigation. The configuration of the hybrid system between biomass energy and wind energy as well as some problems from various design factors are also presented. Based on the findings, this alternative energy utilization through biomass-based hybrids can save costs and improve environmental conditions, especially for the electrification of off-grid rural areas. This paper will provide important information to policymakers, academics, and investors, especially in carrying out the development and factors related to the utilization of wind-biomass-based hybrid energy systems.

The Polish Wind Energy Association (PWEA) is Poland’s largest organization promoting alternative energy sources, mainly onshore and offshore wind power. It is actively involved in consultations on strategic documents and acts of legislation related to the market of renewable energy sources, alternative fuels, and the energy transition. By working together with decision-makers at the EU, national, and local government levels, it aligns various interests to promote Poland’s sustainable development. It organizes events bringing together representatives of the sector and decision-makers, including the annual PWEA Conference – the largest such event in Central and Eastern Europe ( http://konferencjapsew.pl/en/) devoted to prospects for the development of onshore and offshore wind energy in Poland. The Association initiated the establishment of the RE-Source Poland Hub Foundation ( http://resourcepoland.pl/en/), which shows businesses how they can become part of the trend towards the green transition and sustainable development. It promotes pro-environmental attitudes and knowledge of the environmental, economic, and social benefits of wind energy in the media, on social media (such as https://www.facebook.com/psew.pwea and https://twitter.com/PSEW_PWEA), and during the “Summer with the Wind” family summer picnics (Lato z wiatrem) held at the Baltic Sea.

This paper reports a new strand wire winding method in a solenoidal coil with limited geometry that enables good impedance matching. In the proposed method strand wires are wound layer-by-layer on top of each other allowing one to set equivalent inductance and resistance of the coil to desired values while obtaining dense magnetic flux and high current carrying capacity. As a proof-of-concept demonstration, simple model setups were constructed with solenoidal coils composed of copper wire strands wound according to the proposed method, and a plastic pipe. The measurements were repeated with a metal shell placed inside the coil to model a complete heating system. System inductance and resistance were measured at two different frequencies. The results show that with the new winding method it is possible to increase a coil’s turn number and the number of strand layers composed by the coil. Also, adding and removing strand layers in the proposed coil architectures enable inductance and resistance values to decrease and increase, respectively, in a controlled way. To understand changes of system parameters, simulations were also performed. The calculated inductance and resistance values in the simulations agree well with the measurement results and magnetic flux distribution created in the system demonstrates the changes.

Traps to catch microfauna transported by wind were installed on already colonised by plants area, in the vicinity of the glacier. After 6-week-exposition 859 individuals of microfauna were caught, of which Nematoda constituted 71%, Tardigrada 22% and Rotifcra 7%. Number of microfauna individuals caught depended on distance from the already colonised areas and presence of plant parts, together with which animals can be transported more easily. Microfauna connected with vegetation, which is transferred together with plant parts, was transported in higher numbers. Probably these taxa (i.e. Diphascon within tardigrades and Dorylaimidae within nematodes) colonise new habitats at first, but other species dominate later in freshwater bodies.