Search results

Filters

  • Journals
  • Authors
  • Keywords
  • Date
  • Type

Search results

Number of results: 9
items per page: 25 50 75
Sort by:
Download PDF Download RIS Download Bibtex

Abstract

Thermoelectric generators using the Seebeck effect to generate electricity are increasingly used in various areas of human activity, especially in cases where a cheap high-temperature heat source is available. Despite many advantages, TEG generators have one major disadvantage: very low efficiency of heat conversion into electrical power which strongly depends on the applied load resistance. There is a maximum of generated power between the short and the open circuit in which it is zero. That is why optimization of TEG modules is particularly important. In this paper a method of maximization of generated power in a single TEG module is presented for two cases. The first case concerns a problem with fixed heat flux flow into the hot side of the module whereas the second one concerns a problem with fixed heat transfer parameters in hot heat exchanger i.e. supply gas temperature and heat transfer coefficient. A number of optimization results performed for various values of these parameters are presented and discussed.
Go to article

Authors and Affiliations

Artur Poświata
1
Paweł Gierycz
1

  1. Warsaw University of Technology, Faculty of Chemical and Process Engineering, ul. Waryńskiego 1, 00-645 Warsaw, Poland
Download PDF Download RIS Download Bibtex

Abstract

In this paper, selected aspects of the national technical level of electric energy supply security is shown. An analysis and assessment of the electric power infrastructure in area of generation, transmission and distribution in aspects of electric energy security is conducted. The profile of the generation sector and grid infrastructure in the area of transmission and distribution is shown. The present and future situation in a range of operation of electric power infrastructure in the area of generation, transmission and distribution in the frames of the National Electric Power System in the electric energy supply security context is determined. The level of national electric energy supply security in area of generation and grid infrastructure is assessed. Threats of electric energy supply security are described and the catalogue of essential actions for the assurance of electric energy supply security are proposed. In the area of electricity generation, at present there is no danger to the electricity supply security in normal load conditions, but there is a high probability that it will occur in the future (after 2025) when the forecasted increase in electricity demand takes place and the new stringent environment protection requirements (Directive IED, BAT conclusions, Winter Package) enter into force. The network infrastructure in area of transmission and distribution is admittedly adapted for presently occurred typical conditions of electric energy demand and the realization of internal tasks in normal conditions, but can create a potential threat for electric energy supply security. In the context of the forecasted increase of electric energy demand, inadequate power generation sources in the National Electric Power System and available through intersystem connections, their uneven location on the territory of Poland in the shortage of proper network transmission capacities, the necessity of improvement of the quality and electric energy supply reliability to final consumers and the intensive development of renewable energy sources, the present network infrastructure in area of transmission and distribution will be insufficient.

Go to article

Authors and Affiliations

Waldemar Dołęga
Download PDF Download RIS Download Bibtex

Abstract

An electric power steering system (EPS) is a new type of steering system developed after a mechanical hydraulic power system (MHPS) and electric-hydraulic power steering system (EHPS). In order to coordinate and solve the portability and sensitivity of the steering system optimally, taking an induction power steering system as the research object, the control algorithm of induction motor control under the EPS is studied in this paper. In order to eliminate the feed-forward performance degradation caused by the change of feed-forward parameters, an on-line identification algorithm of feed-forward parameters is proposed. It can improve the control performance of online identification among three feed-forward parameters in the T-axle motor, it improves on the robustness of feed-forward control performance, at the same time it also gives simulation and test results. This method can improve the control performance of the three feed-forward parameter online identification of the T-axis motor and improve the robustness of feed-forward control performance. At the same time, simulation and test results are given. The simulation results show that the algorithm can significantly improve the response speed and control accuracy of EPS system control.

Go to article

Authors and Affiliations

Zhang Naibiao
Cai Tianfang
Han Xuezheng
Download PDF Download RIS Download Bibtex

Abstract

During a blackout, after the post-disaster collapse of an electric power system (EPS), units of thermal power plants should switch-over to the house load operation mode (PPW). However, regarding the dynamics of a post-disaster blackout process, many units can be in forced outage Therefore, restart of these units from the start-up sources with a self-start capability is necessary. The Transmission Network Code in force imposes periodic tests and system tests for such sources. Any system test must be preceded and followed by simulation investigations in which the possibilities: (1) to bring voltage to the started-up power plant by a starting path and (2) to activate the highest-power auxiliaries (PW) of the unit being started-up are evaluated. In the paper, chosen results of simulative investigations of the transient phenomena in the starting path from the hydroelectric power plant of Włocławek (HPP Włocławek) to the thermal power plant of P˛atnów (TPP P˛atnów), related to the system test conducted in September 2017 have been presented.

Go to article

Authors and Affiliations

Ireneusz Grządzielski
Bartosz Olejnik
Mikołaj Zakrzewski
Download PDF Download RIS Download Bibtex

Abstract

Due to unfavorable factors, dangerous conditions occurred in the delivery of electric energy in Poland. This was the most serious incident of its kind since the 1980’s. Such a serious incident raised concern about the safety of the electric power system in the summer and led to the formulation of conclusions for the future. In this article, the author analyses the conditions, which caused that situation. Poland was experiencing a doubt in August 2015, which along with an extremely high maximum daily temperature created remarkably unfavorable conditions for power plants and decreased the capacity of overhead power lines. Such unfavorable metrological conditions occurred not only in Poland, but also in Central-Eastern and Western Europe. It is worth emphasizing that the safety of electric energy delivery was endangered only in Poland. The improper renovation and upkeep policies, as well as unplanned outages in power plants caused a significant decrease of available power in the National Electric Power System. Unscheduled flows between Germany and Poland ruled out the possibility of importing electric energy at such a critical time. The author presents the correlation between the maximum daily air temperature in the sweltering heat and an increase in the demand for electric energy. Overall, unfavorable conditions posed a threat in the delivery of electric energy in Poland. In this article, the author draws attention to the report from the Supreme Audit Office (Najwyższa Izba Kontroli – NIK) from 2014, which predicted such a dangerous situation. Unfortunately, that report remained unnoticed. The author formulated appropriate solutions in order to increase the safety of electric energy delivery in the summer and to prevent such occurrences in the future.

Go to article

Authors and Affiliations

Bartosz Sobik
Download PDF Download RIS Download Bibtex

Abstract

The overriding objective of the National Electric Power System (KSE) is to ensure the security of electricity supply. In summer, the upward trend in the demand for electric energy is caused by, among others, the proliferation of air conditioners. Therefore, the upward trend in summer’s on-peak demand is expected to be maintained. Examples from 2015, 2016 or 2018 indicate that National Electric Power System needs a summer’s on-peak source that will be able to produce electricity regardless of the hydrological conditions. Photovoltaics is a source of energy that can cover the peak demand during sweltering heat. This article briefly characterizes the problem of increasing demand for electricity in summer and uses examples that have taken place in recent years. The main conclusion is the postulate for the extension of photovoltaic power in the National Electric Power System, the purpose of which will be the production of electricity during sweltering heat, covering the peak load in the system. This article presented both the advantages and disadvantages of such a solution. Unfavorable weather conditions (high air temperature, low water level, lack of wind) limit the production of electricity from wind farms or conventional power plants, and also increase transmission losses, which is why photovoltaics is a desirable source from the National Electric Power System’s point of view. The article refers to examples from the Czech Republic and Germany, where a significant installed capacity of photovoltaics enables the stable operation of the power system during sweltering heat. It was also pointed out that the role of photovoltaics in the National Electric Power System is growing, which is consistent with the assumptions of the Polish Energy Policy Project until 2040.

Go to article

Authors and Affiliations

Bartosz Sobik
Download PDF Download RIS Download Bibtex

Abstract

Vacuum conditions in foundry installations are generated using electric-driven vacuum pumps. The purpose of the experiment is to evaluate the performance of a vacuum-assisted system for compaction of moulding sand basing on registered plots of selected electric power parameters of the power-supplying system of the pumps. Model testing done on an experimental vacuum system installation, power-supplied from a system incorporating the recorders of instantaneous current and voltage values. Following the numerical procedure, the experimental data are analysed to yield mathematical relationships between the variations of the generated vacuum pressure levels and variations of selected electric power parameters. Registered and computed values of selected parameters: instantaneous and RMS voltage and current values, active, reactive and apparent power levels and power coefficient allow for diagnosing the adequacy and reliability of the system operation. According to the authors, the applied monitoring of the power parameters of a vacuum-assisted installation may become an effective and easy practical method of evaluating the performance of such installations, used also in foundry plants.

Go to article

Authors and Affiliations

E. Ziółkowski
M. Brzeziński
R. Wrona
K. Smyksy
P. Zyzak
Download PDF Download RIS Download Bibtex

Abstract

In this article the main problems related with the proper choice of the design and operation parameters of vacuum installation in vacuum moulding system have been discussed. In such system a vacuum are generated using electric-driven vacuum pumps. The aim of the experiment is to evaluate the performance of a vacuum system basing on registered plots of selected electric power parameters of the power-supplying system of the pumps with parallel measurements instantaneous values of pressure in selected points of model stand. The measurements system for power-supply unit has incorporated the recorders of instantaneous current and voltage values. Following the suitable numerical procedure, the experimental data are analysed to yield mathematical relationships between the variations of the generated vacuum pressure levels and variations of selected electric power parameters. According to the authors, the applied measurements system of the parameters of a vacuum-assisted installation may become an effective and easy practical method of evaluating the performance of such installations, used also in industry.

Go to article

Authors and Affiliations

M. Brzeziński
K. Smyksy
E. Ziółkowski
R. Wrona
Download PDF Download RIS Download Bibtex

Abstract

One of the most critical systems of any satellite is the Electrical Power System (EPS) and without any available energy, the satellite would simply stop to function. Therefore, the presented research within this paper investigates the areas relating to the satellite EPS with the main focus towards the CubeSat platform. In this paper, an appropriate EPS architecture with the suitable control policy for CubeSat missions is proposed. The suggested control strategy combines two methods, the Maximum Power Point Tracking (MPPT) and the Battery Charge Regulation (BCR), in one power converter circuit, in order to extract the maximum power of the Photovoltaic (PV) system and regulate the battery voltage from overcharging. This proposed combined control technique is using a Fuzzy Logic Control (FLC) strategy serving two main purposes, the MPPT and BCR. Without an additional battery charger circuit and without switching technique between the two controllers, there are no switching losses and the efficiency of the charging characteristic can be increased by selecting this proposed combined FLC. By testing a space-based PV model with the proposed EPS architecture, some simulation results are compared to demonstrate the superiority of the proposed control strategy over the conventional strategies such as Perturb and Observe (P&O) and FLC with a Proportional Integral Derivative (PID) controller.

Go to article

Authors and Affiliations

Abderrahmane Seddjar
Kamel Djamel Eddine Kerrouche
Lina Wang

This page uses 'cookies'. Learn more