Ing. Rudolf Bayer, Ph.D.

The issue of light pollution, which is partly caused by public lighting, is a frequent topic of professional discussions. The influence of the luminous flux emitted by the lighting system above the horizon, on the facades of houses in the area or into the nature is often discussed. This study therefore deals with the analysis of the distribution of luminous flux from public lighting in urban environments.

Due to continuous development, LED lamps are gradually becoming the dominant light source on the market, and with some exceptions in certain specific applications, LED technology today accounts for most of the lighting manufacturers' portfolio and sales. However, new technologies bring new technical problems and challenges that need to be addressed. One of the specifics of LED technology compared to conventional technologies is another design solution and the associated different light distribution in the luminaire. This paper therefore aims to analyze whether and how the design of LED luminaires affects the spatial distribution of the light emitted spectrum. The aim of the paper is also to verify theoretical hypotheses by measuring spatial spectral characteristics of LED luminaires.

The article deals with the possibilities of using the Arduino platform in lighting and photometry. The simplicity and wide range of libraries, expanding modules and sensors of this platform opens up new possibilities for simple modelling of the light field, its properties and for modelling the principle of photometric devices.

The aim of paper is biodynamic lighting, which is artificial lighting that should best simulate the spectrum and the daily course of natural daylight. Biodynamic lighting can be achieved by controlling luminaires with several different light sources with different correlated color temperatures, nowadays especially with the use of LEDs. This paper deals with analysis of spectral composition and other photometric parameters of light of industrially used LED samples and their effects on biodynamic lighting.

The paper deals with biodynamic artificial lighting, which should follow the spectral composition and the daily course of natural daylight. Biodynamic lighting can be achieved by controlling luminaires with several different light sources with different CCT, nowadays especially using LEDs. This paper deals with analysis of spectral composition and other photometric parameters of light of industrially used LED samples and their effects on biodynamic lighting.

The paper deals with possibilities of applications of luminaires with tunable correlated color temperature (CCT) and their influence on the perception of light scenes and on biological functions of human body. The first part starts with a description of human visual system, physiological effects of optical radiation and principle of perception. The second part shows the analysis of photometric parameters of the sample of tunable white luminaire with variable CCT.

The paper discusses a way to deploy luminaires in a model room to provide required illuminance levels and uniformity of the working plane by using a genetic algorithm. The problems about determining the adequate DNA structure and fitness function are introduced and solved. The reflections from walls, ceiling and floor are taken into account in the calculations and further discussed. The output results of the algorithm are judged by requirements of the standard CSN EN 12464-1 and from the lighting system designer's point of view.

The research deals with construction of solar concentrator with photovoltaic panels and thermal circuit. As a part of this research there is a design of solar tracking system for solar concentrators. The use of concentrator with solar tracking system shows the performance of combined generation of electrical power and heat from solar radiation. The results of electrical and thermal measurements show the electrical performance and power performance of heat circuit.

Modern computer lighting design programs are using purely diffuse reflecting surfaces during calculations for simplification reasons. For more accurate calculations it is necessary to use real reflective properties of surfaces that can be measured by a reflectophotometer. The reflectophotometer OPTE-F3K of the Department of Electrical Power Engineering, FEE CTU in Prague, allows measuring reflective properties of surface samples 2 by 2 cm. ReflectoSoft, an application designed especially for this reflectophotometer, enables measurements of BRDF in the Klems system of patches. The measured values can then be stored into an XML file containing the BRDF matrix of 145 × 145 elements. The results can be viewed using the software BSDFViewer. The goal of this paper is to present the current state of the renovation of OPTE-F3K, which enables ray tracing algorithms to use measured reflective properties of real materials.

The paper deals with determination of power consumption of street lighting of general type under the conditions of mesopic vision.

The paper discusses a way to deploy a given number of point light sources in the interior to provide required illuminance levels and uniformity of the working plane by using a genetic algorithm. Furthermore a genetic algorithm has been used to generate a proper luminous intensity distribution curve of multiple luminaires to meet the given criteria for the reference plane of the model room for predefined luminaire positions.

The paper deals with lighting road design. The demands on illuminance are defined in standard ČSN EN 13201 in case of Czech Republic. There are several parameters that a designer can change to get the optimal solution to fulfill the standard. The distance between pillars, their heights, the lamp overlap and tilt have to be defined. Such number of parameters make the optimization difficult. This paper solves the optimization via genetic algorithm. The fitness function that is convergent to good solutions is a vital point for this type of algorithms. The paper shows that solutions found by the genetic algorithm fulfill the demands and it also shows the way, how the fitness function can be created.

In recent years the theme mesopic vision is increasingly being discussed in professional and laical discussions in terms of street and outdoor space lighting. These applications are specific mainly by low levels of illuminance, more precisely by low levels of luminance the observer is adapted to. The methodology itself and the accurate evaluation of mesopicaly perceived photometric quantities is relatively difficult and so far there is no general consensus as how to define the impact of mesopic area of vision on the overall vision process. This paper shows within current possibilities the theoretical influence/impact of mesopic vision on energy performance of street lighting systems.

Reducing of the energy consumption and creating of the pleasant working environment in buildings is a actual topic touching not only the lighting field. Currently there is effort for better use of a daylight in buildings. The problem is the unpredictability of the daylight and its parameterization. In fact the only quantitative parameter is horizontal illuminance for CIE overcast standard sky [1], which is the most often used sky type. This article deals with the determination of illuminance of unobstructed vertical plane. For calculations of daylight for the certain date, time and the type of the sky in most cases it is advantageous to know the vertical plane illuminance representing the building facade.

To apply more economical and powerful light sources is a constant topic of many professional discussions. One of the nowadays most promising light sources are LEDs – Light Emitting Diodes. Even though there are predictions regarding lifetime and light flux dependence of LEDs over time, actual in field application and measurements are rare. This paper presents results of 16 monitored street lighting systems after more than 6000 hours of operation thanks to help of Eltodo-Citelum s. r .o.

This paper describes the status of the reflectometer modernization project. First of all the reflectometer’s function and the laboratory workplace deployment is described. Basic abilities of the original reflectometer’s built-in electronics are mentioned and the reasons for its upgrade. Features of the newly designed and manufactured electronics are explained with help of current schemes of used circuitry and a table of supported commands.

Illuminance measurements in the mesh of control points is the most commonly used method for evaluation of parameters of interior lighting systems as national supervisory authorities (eg. The regional health stations) and private entities engaged in design activities in the field of lighting systems. Measurements can verify requirements for lighting systems of the Czech technical standards. The measurement of illuminance is still processed manually, ie. projecting a mesh of control points and then measuring the illuminance by illuminance meter in each of the control points. One of the ways to ensure a considerable acceleration of the lengthy process of illuminance measuring in the interior is the automation of the measurement process using robotic units, which would be able to project its own mesh of control points according to standards and at the same time ranging mesh of control points to measure illuminance in this mesh.

The accuracy of calculations of the photometric quantities is dependent on the accuracy of the description of interreflections taking place at the given place. It is therefore important to know the exact characteristics of the reflective materials. Reflectance of surfaces can be measured by a reflectometer such as OPTA-F3K. This article aims to describe the current draft of the new control and power electronics of the device.

The calculation accuracy of photometric quantities is dependent on the description accuracy of interreflections ongoing in a given place. Therefore knowing accurate reflective properties of materials is of great importance. These properties can be measured by a spatial luminance distribution measuring device of reflecting surfaces, such as OPTE-F3K. This paper informs about the progress of the ongoing upgrade of this device being made.

The aim of this paper is to describe the reflective properties of materials and their specific use in calculating the parameters of lighting scenes. Computer programs commonly used for modeling parameters of lighting scenes to create a mathematical model of a scene primarily work with diffusely reflecting surfaces in the intended area where light can be employed to characterize the surface integral reflection coefficient. Numerical model of a scene containing only diffusely reflecting surface is mathematically less demanding than the model in the calculation of parameters including lighting scenes and actual generally reflecting surface. Structural elements of modern buildings are often made of materials with its reflective properties differ significantly from the ideal diffusely reflecting surfaces. If the modeling of lighting scenes is not taken into account the directional dependence of the reflection coefficient, the model of light scenes can contain considerable error.

The paper summarizes the common principles in the light sources, especially LEDs emitting white light. Described is a new automatic measuring station built in the photometric laboratory CTU in Prague, which allows analyzing the spectrum of light emitted by different light sources using a monochromator Oriel 77250 1/8 using a newly developed software SpectroSoft. Included are examples of graphic results of spectra of selected LEDs.

In order to be able to measure direct and indirect solar radiation, a device referred to as Solar Tracker was developed. Values of direct and indirect solar radiation are important for efficient selection of technology, operation, control and policy mainly in the field of fotovoltaic power plants and are also important in other subject fields, such as the lighting systems in building industry.

Nowadays there are procedures to evaluate the energy performance of buildings, but there is no methodology to design buildings with optimized energy performance. It is impossible to effectively optimize the lighting systems of already designed buildings. The obstacle of a comprehensive evaluation of a lighting system is the perception of the lighting quality demands and the energy performance as two separated opposing areas. The current evaluation of lighting energy performance of buildings, also including an evaluation through parameters such as the relative installed power, is misleading, is not related to the real lighting energy performance, has no direct binding dependencies to photometric parameters in the given building and can negatively influence photometric parameters and the environment of buildings.

This paper deals with a method how to filtrate the first harmonic of a frequency obtained from a mains with high noise and how to detect zero-crossings by the designed adaptive filter. The zero-crossing-detections can be difficult due to multiple zero-crossings caused by superposed noise or in cases, where the signal stays at the zero value for a given time. By a simple filter multiple zero-crossings can be filtered, but a phase-shift occurs between the input and the output of the filter. The designed adaptive filter processes the singal in two parallel branches. The first detects the exact frequency of the first harmonic of the input signal. The second uses this frequency to set the central frequency of a filter, filtering all but the first harmonic from the given input signal.

The paper presents the comparison of luminous and electrical properties of modern LED-based luminaires with properties of the conventional luminaires with high pressure sodium lamp. It collects available product information of compared luminaires with measured luminous and electrical properties of them to allow a reader to take a view of mentioned luminaire properties. The most important values of the luminaire samples compared are the luminous efficacy, color rendering index, startup process characteristics, spectral distribution of the light sources, etc.

The authors deal with the problem of controlling of single phase active filters. Some algorithms for active filters controlling are well known today, but some of them can't be used in case of single phase filters. For example the PQ Theory (Theory of the Instantaneous Reactive Power) is excellent for three phase solutions, but for single phase solutions it can't be implemented. The main challenge in the single phase controlling method is to get the fundamental harmonic function in a proper magnitude and phase. The authors proposed a simple and fast method, which is based on the LMS algorithm ("Least Mean Square" algorithms are a class of adaptive filters). This method can be easily implemented also in 8-bit microcontroller units only with the need of sum and multiplication instructions.

This paper is first of three articles about technology and realization of passive EMC filters. In this inductory section the authors deals with reasons of faults in frequency response of proposing filters. For this purpose is used the "Fault Tree Analysis". The article describes potential problems arising during proposing of filters and explains their possible solutions. There is also included related standards and publications covering these problems in the article.

The electrical power of photovoltaic systems depends on the power of solar radiation incident on the active parts of the system (photovoltaic panels). The incident solar radiation contains of direct and indirect component which is caused by actual weather conditions. Due to the receiving characteristics of the solar panels it could be more efficient to turn the panels directly to the sun while the direct component of solar radiation dominates. The solar concentrators for photovoltaics are based on concentrating the direct solar radiation. This paper should describe the ratio of direct and indirect component of solar radiation in different weather conditions.

The authors deal with the problem of zero-crossing detection in power mains voltage which is highly distorted by harmonics. The zero-crossing detection in such system can be difficult due to multiple zero cross in measured signal for example. Simple filtering of the signal can solve the problem of the distortion but it also adds a phase error between input and output signal. So the zeros both signals aren't synchronized. The authors proposed a solution based on adaptive filtering, which extracts the fundamental harmonic from the input signal. So the zero detection can be done according to the zero crossing in the fundamental harmonic.

The paper presents the comparison of luminous and electrical properties of modern LED-based luminaires with properties of the conventional luminaires with high pressure sodium lamp. It collects available product information of compared luminaires with measured luminous and electrical properties of them to allow a reader to take a view of mentioned luminaire properties. The most important values of the luminaire samples compared are the luminous efficacy, color rendering index, startup process characteristics, spectral distribution of the light sources, etc.

This paper discusses the software Gofosoft4 used to measure luminous intensity distribution curves of light sources and light fixtures. Gofosoft4 is designed specially for the use in the laboratory of photometry, providing an interface to communicate with the goniophotometer and illuminance meter via serial port (RS-232). It's main goal is to make automatic measurings of luminous intensity distribution curves possible, thus making the measurings faster and with only a minimal human intervention. Also this version of Gofosoft is written in Java making it's operation faster and smoother on the given computer then the previous version.

Software Gofosoft v2.1 previously used in the photometric laboratory at the CTU in Prague, FEE was programmed in LabVIEW environment which supported the A / D converter for digitizing data from luxmeters. LabVIEW software was not optimal for that purpose. The luxmeter was later directly connected via a serial interface to the computer and A / D converter was no longer needed. There was a new requirement to provide a practical simplified alternative measurement software for goniophotometer to measure luminous intensity diagrams. Designed and implemented applications Gofosoft4 provides the necessary user interface and automatic measurement of luminous intensity diagrams in the selected photometric planes. Application Gofosoft4, whose functions are described in this paper, was developed in the NetBeans IDE Java environment.

This paper discusses the software Gofosoft4 used to measure luminous intensity distribution curves of light sources and light fixtures. Gofosoft4 is designed specially for the use in the laboratory of photometry, providing an interface to communicate with the goniophotometer and illuminance meter via serial port (RS-232). It's main goal is to make automatic measurings of luminous intensity distribution curves possible, thus making the measurings faster and with only a minimal human intervention. Also this version of Gofosoft is written in Java making it's operation faster and smoother on the given computer then the previous version.

There are many electrical devices connected to the mains requiring reliable synchronization with the mains voltage. These devices are for example thyristor-controlled rectifiers, uninterruptible power supplies or power converters returning electrical power to the mains. The voltage phase difference between the mains and the output of the converter is typically obtained by detecting zero voltage crossings. This is why a reliable zero voltage crossing detection is becoming so important affecting the converter's operation and the quality of the supplied or consumed energy. Suitable detection can be achieved with signal processing making use of fast signal processors or programmable gate arrays. But it makes the detection more complex and expensive. Therefore the authors try to find a simple and reliable solution even in the case of high distorted mains using only a simple microcontroller