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Detalles de la revista
Formato
Revista
eISSN
2255-8896
Publicado por primera vez
18 Mar 2008
Periodo de publicación
6 veces al año
Idiomas
Inglés

Buscar

Volumen 54 (2017): Edición 6 (December 2017)

Detalles de la revista
Formato
Revista
eISSN
2255-8896
Publicado por primera vez
18 Mar 2008
Periodo de publicación
6 veces al año
Idiomas
Inglés

Buscar

7 Artículos

Physical and Technical Energy Problems

access type Acceso abierto

Development and Comparison of Technical Solutions for Electricity Monitoring Equipment

Publicado en línea: 24 Jan 2018
Páginas: 3 - 9

Resumen

Abstract

The paper focuses on the elaboration of a demand-side management platform for optimal energy management strategies; the topicality is related to the description and comparison of the developed electricity monitoring and control equipment. The article describes two versions based on Atmega328 and STM32 microcontrollers, a lower and higher level of precision, and other distinct performance parameters. At the end of the article, the results of the testing of the two types of equipment are given and their comparison is made.

Palabras clave

  • demand side management
  • demand response
  • Internet of Things
  • monitoring
  • sockets
  • voltage measurement
access type Acceso abierto

Modelling the Spatial Distribution of Wind Energy Resources in Latvia

Publicado en línea: 24 Jan 2018
Páginas: 10 - 20

Resumen

Abstract

The paper studies spatial wind energy flow distribution in Latvia based on wind speed measurements carried out at an altitude of 10 m over a period of two years, from 2015 to 2016. The measurements, with 1 min increments, were carried out using certified measuring instruments installed at 22 observation stations of the Latvian National Hydrometeorological and Climatological Service of the Latvian Environment, Geology and Meteorology Centre (LEGMC). The models of the spatial distribution of averaged wind speed and wind energy density were developed using the method of spatial interpolation based on the historical measurement results and presented in the form of colour contour maps with a 1×1 km resolution. The paper also provides the results of wind speed spatial distribution modelling using a climatological reanalysis ERA5 at the altitudes of 10, 54, 100 and 136 m with a 31×31 km resolution. The analysis includes the comparison of actual wind speed measurement results with the outcomes of ERA5 modelling for meteorological observation stations in Ainazi, Daugavpils, Priekuli, Saldus and Ventspils.

Palabras clave

  • wind speed
  • wind energy
  • measurements
  • modelling
  • ERA5
access type Acceso abierto

A Methodology for the Estimation of the Wind Generator Economic Efficiency

Publicado en línea: 24 Jan 2018
Páginas: 21 - 31

Resumen

Abstract

Integration of renewable energy sources and the improvement of the technological base may not only reduce the consumption of fossil fuel and environmental load, but also ensure the power supply in regions with difficult fuel delivery or power failures. The main goal of the research is to develop the methodology of evaluation of the wind turbine economic efficiency. The research has demonstrated that the electricity produced from renewable sources may be much more expensive than the electricity purchased from the conventional grid.

Palabras clave

  • energy resources
  • renewable energy sources
  • wind energy
access type Acceso abierto

New Hydrokinetic Turbine for Free Surface Gravitational Wave Transformation

Publicado en línea: 24 Jan 2018
Páginas: 32 - 41

Resumen

Abstract

The present article deals with an alternative form of energy – the conversion of marine/ocean wave energy using an axial self-regulating blade (SB) hydrokinetic turbine (ASRBHK turbine). The article analyses the operation of the ASRBHK turbine and draws the resulting conclusions about the mechanism, in which the power transfer element is a self-regulating blade.

Palabras clave

  • axial hydrokinetic turbine
  • renewable energy
  • wave energy
  • wave energy power plant
  • wave energy converter
  • wave energy receiver
  • self-regulating blade
access type Acceso abierto

Performance Evaluation of Irbene RT-16 Radio Telescope Receiving System

Publicado en línea: 24 Jan 2018
Páginas: 42 - 53

Resumen

Abstract

In the present paper, recent measurement results of refurbished Irbene RT-16 radio telescope receiving system performance are presented. The aim of the research is to evaluate characteristics of RT-16, which will allow carrying out necessary amplitude calibration in both single dish and VLBI observations, to improve the performance of existing system as well as to monitor, control and compare performance if possible changes in the receiving system will occur in future. The evaluated receiving system is 16 m Cassegrain antenna equipped with a cryogenic receiver with frequency range from 4.5 to 8.8 GHz, which is divided into four sub-bands. Multiple calibration sessions have been carried out by observing stable astronomical sources with known flux density by using in-house made total power registration backend. First, pointing offset calibration has been carried out and pointing model coefficients calculated and applied. Then, amplitude calibration, namely antenna sensitivity, calibration diode equivalent flux density and gain curve measurements have been carried out by observing calibration sources at different antenna elevations at each of the receiver sub-bands. Beam patterns have also been evaluated at different frequency bands. As a whole, acquired data will serve as a reference point for comparison in future performance evaluation of RT-16.

Palabras clave

  • amplitude calibration
  • pointing calibration
  • radio astronomy

Applied Physics

access type Acceso abierto

Numerical Approach of a Water Flow in an Unsaturated Porous Medium by Coupling Between the Navier–Stokes and Darcy–Forchheimer Equations

Publicado en línea: 24 Jan 2018
Páginas: 54 - 64

Resumen

Abstract

In the present research, simulations have been conducted to determine numerically the dynamic behaviour of the flow of underground water fed by a river. The basic equations governing the problem studied are those of Navier–Stokes equations of conservation of momentum (flows between pores), coupled by the Darcy–Forchheimer equations (flows within these pores). To understand the phenomena involved, we first study the impact of flow rate on the pressure and the filtration velocity in the underground medium, the second part is devoted to the calculation of the elevation effect of the river water on the flow behaviour in the saturated and unsaturated zone of the aquifer.

Palabras clave

  • Darcy–Forchheimer equations
  • groundwater flow
  • hydrodynamic modelling
  • porous medium

Electronics

access type Acceso abierto

Comparison of Chromatic Dispersion Compensation Method Efficiency for 10 Gbit/S RZ-OOK and NRZ-OOK Wdm-Pon Transmission Systems

Publicado en línea: 24 Jan 2018
Páginas: 65 - 75

Resumen

Abstract

In the paper, the authors compare efficiency of two physical dispersion compensation methods for single channel and 8-channel WDM fibre-optical transmission systems using return-to-zero (RZ) and non-return-to-zero (NRZ) line codes for operation within optical C-band frequencies by means of computer simulations. As one of the most important destructive effects in fibre optical transmission systems (FOTS) is chromatic dispersion (CD), it is very important to reduce its negative effect on a transmitted signal. Dispersion compensation methods that were implemented in the research were dispersion compensating fibre (DCF) and fibre Bragg grating (FBG). The main goal of the paper was to find out which dispersion compensation method (DCF or FBG) provided the highest performance increase for fibre-optical transmission system and provided the longest transmission distance after dispersion compensation was implemented at different locations in the fibre-optical line while RZ or NRZ line codes were used. In the paper the reference point of signal quality for all measurements, which were obtained at the receiver, was BER<10−12.

Palabras clave

  • DCF
  • DCM
  • dispersion
  • dispersion compensation
  • FBG
  • optical access
  • optical fibre
  • SMF
  • WDM-PON
7 Artículos

Physical and Technical Energy Problems

access type Acceso abierto

Development and Comparison of Technical Solutions for Electricity Monitoring Equipment

Publicado en línea: 24 Jan 2018
Páginas: 3 - 9

Resumen

Abstract

The paper focuses on the elaboration of a demand-side management platform for optimal energy management strategies; the topicality is related to the description and comparison of the developed electricity monitoring and control equipment. The article describes two versions based on Atmega328 and STM32 microcontrollers, a lower and higher level of precision, and other distinct performance parameters. At the end of the article, the results of the testing of the two types of equipment are given and their comparison is made.

Palabras clave

  • demand side management
  • demand response
  • Internet of Things
  • monitoring
  • sockets
  • voltage measurement
access type Acceso abierto

Modelling the Spatial Distribution of Wind Energy Resources in Latvia

Publicado en línea: 24 Jan 2018
Páginas: 10 - 20

Resumen

Abstract

The paper studies spatial wind energy flow distribution in Latvia based on wind speed measurements carried out at an altitude of 10 m over a period of two years, from 2015 to 2016. The measurements, with 1 min increments, were carried out using certified measuring instruments installed at 22 observation stations of the Latvian National Hydrometeorological and Climatological Service of the Latvian Environment, Geology and Meteorology Centre (LEGMC). The models of the spatial distribution of averaged wind speed and wind energy density were developed using the method of spatial interpolation based on the historical measurement results and presented in the form of colour contour maps with a 1×1 km resolution. The paper also provides the results of wind speed spatial distribution modelling using a climatological reanalysis ERA5 at the altitudes of 10, 54, 100 and 136 m with a 31×31 km resolution. The analysis includes the comparison of actual wind speed measurement results with the outcomes of ERA5 modelling for meteorological observation stations in Ainazi, Daugavpils, Priekuli, Saldus and Ventspils.

Palabras clave

  • wind speed
  • wind energy
  • measurements
  • modelling
  • ERA5
access type Acceso abierto

A Methodology for the Estimation of the Wind Generator Economic Efficiency

Publicado en línea: 24 Jan 2018
Páginas: 21 - 31

Resumen

Abstract

Integration of renewable energy sources and the improvement of the technological base may not only reduce the consumption of fossil fuel and environmental load, but also ensure the power supply in regions with difficult fuel delivery or power failures. The main goal of the research is to develop the methodology of evaluation of the wind turbine economic efficiency. The research has demonstrated that the electricity produced from renewable sources may be much more expensive than the electricity purchased from the conventional grid.

Palabras clave

  • energy resources
  • renewable energy sources
  • wind energy
access type Acceso abierto

New Hydrokinetic Turbine for Free Surface Gravitational Wave Transformation

Publicado en línea: 24 Jan 2018
Páginas: 32 - 41

Resumen

Abstract

The present article deals with an alternative form of energy – the conversion of marine/ocean wave energy using an axial self-regulating blade (SB) hydrokinetic turbine (ASRBHK turbine). The article analyses the operation of the ASRBHK turbine and draws the resulting conclusions about the mechanism, in which the power transfer element is a self-regulating blade.

Palabras clave

  • axial hydrokinetic turbine
  • renewable energy
  • wave energy
  • wave energy power plant
  • wave energy converter
  • wave energy receiver
  • self-regulating blade
access type Acceso abierto

Performance Evaluation of Irbene RT-16 Radio Telescope Receiving System

Publicado en línea: 24 Jan 2018
Páginas: 42 - 53

Resumen

Abstract

In the present paper, recent measurement results of refurbished Irbene RT-16 radio telescope receiving system performance are presented. The aim of the research is to evaluate characteristics of RT-16, which will allow carrying out necessary amplitude calibration in both single dish and VLBI observations, to improve the performance of existing system as well as to monitor, control and compare performance if possible changes in the receiving system will occur in future. The evaluated receiving system is 16 m Cassegrain antenna equipped with a cryogenic receiver with frequency range from 4.5 to 8.8 GHz, which is divided into four sub-bands. Multiple calibration sessions have been carried out by observing stable astronomical sources with known flux density by using in-house made total power registration backend. First, pointing offset calibration has been carried out and pointing model coefficients calculated and applied. Then, amplitude calibration, namely antenna sensitivity, calibration diode equivalent flux density and gain curve measurements have been carried out by observing calibration sources at different antenna elevations at each of the receiver sub-bands. Beam patterns have also been evaluated at different frequency bands. As a whole, acquired data will serve as a reference point for comparison in future performance evaluation of RT-16.

Palabras clave

  • amplitude calibration
  • pointing calibration
  • radio astronomy

Applied Physics

access type Acceso abierto

Numerical Approach of a Water Flow in an Unsaturated Porous Medium by Coupling Between the Navier–Stokes and Darcy–Forchheimer Equations

Publicado en línea: 24 Jan 2018
Páginas: 54 - 64

Resumen

Abstract

In the present research, simulations have been conducted to determine numerically the dynamic behaviour of the flow of underground water fed by a river. The basic equations governing the problem studied are those of Navier–Stokes equations of conservation of momentum (flows between pores), coupled by the Darcy–Forchheimer equations (flows within these pores). To understand the phenomena involved, we first study the impact of flow rate on the pressure and the filtration velocity in the underground medium, the second part is devoted to the calculation of the elevation effect of the river water on the flow behaviour in the saturated and unsaturated zone of the aquifer.

Palabras clave

  • Darcy–Forchheimer equations
  • groundwater flow
  • hydrodynamic modelling
  • porous medium

Electronics

access type Acceso abierto

Comparison of Chromatic Dispersion Compensation Method Efficiency for 10 Gbit/S RZ-OOK and NRZ-OOK Wdm-Pon Transmission Systems

Publicado en línea: 24 Jan 2018
Páginas: 65 - 75

Resumen

Abstract

In the paper, the authors compare efficiency of two physical dispersion compensation methods for single channel and 8-channel WDM fibre-optical transmission systems using return-to-zero (RZ) and non-return-to-zero (NRZ) line codes for operation within optical C-band frequencies by means of computer simulations. As one of the most important destructive effects in fibre optical transmission systems (FOTS) is chromatic dispersion (CD), it is very important to reduce its negative effect on a transmitted signal. Dispersion compensation methods that were implemented in the research were dispersion compensating fibre (DCF) and fibre Bragg grating (FBG). The main goal of the paper was to find out which dispersion compensation method (DCF or FBG) provided the highest performance increase for fibre-optical transmission system and provided the longest transmission distance after dispersion compensation was implemented at different locations in the fibre-optical line while RZ or NRZ line codes were used. In the paper the reference point of signal quality for all measurements, which were obtained at the receiver, was BER<10−12.

Palabras clave

  • DCF
  • DCM
  • dispersion
  • dispersion compensation
  • FBG
  • optical access
  • optical fibre
  • SMF
  • WDM-PON

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