FACULTY OF BUILDING SERVICES Eng. Marilena Pușa MĂIEREAN PhD THESIS SYNOPSIS LIGHTING OF URBAN PUBLIC SPACES Scientific Adviser Prof. Florin Radu POP, PhD., Eng. SCIENTIFIC COMMITTEE CHAIRMAN: MEMBERS: Prof. Daniela MANEA, PhD., Eng. Chancellor, Technical University of Cluj-Napoca Prof. Florin Radu POP, PhD., Eng. Scientific adviser, Technical University of Cluj-Napoca Prof. Cornel BIANCHI, PhD., Eng. Scientific reviewer, Technical University of Civil Engineering Bucharest Prof. Nicolae GOLOVANOV, PhD., Eng., Member of the Romanian Academy Scientific reviewer, University Politehnica of Bucharest Reader Dorin BEU, PhD., Eng. Scientific reviewer, Technical University of Cluj-Napoca
The Premises of the PhD Thesis 1 A. Theoretical Premises The theoretical approach of this PhD thesis was developed around two premises, which follow two significant reports, respectively the Light and the People, and the Light and the Objects. Light is, by definition, associated with the People, as it represents an electromagnetic radiation intercepted by the visual system, which induces its visual perception to it. Therefore, Light, as a specific form of energy out of all other electromagnetic radiation forms, is defined through the visual effect created by this energy. The history of architecture demonstrates that the light constitutes a core element of form in architecture. People live in architectural spaces, where they are surrounded by coloured shapes and surfaces. The effect, at an individual level, of the mutual conditioning between architecture and light is an immediate representation of the space in which he moves and lives, thus becomes relevant at a perception and cognitive registering level by the individual of all dimensions and traits of this space: the individual builds psychological representations of the immediate space. The human answer to colour is at the same time objective and subjective and, in order to create a truly harmonious architecture, the technical, physiological and psychological traits of colour need to be integrated in the design process. On the other hand, Light is not visible by itself, but through the illuminated objects, through the light's reflexion on their surfaces, which thus become physically visible. Therefore, the quantity and quality of light are important for the perception of the scene, along with other parameters such as the nature of the surfaces, the angle of incidence. For the purposes of this paper, the illuminated objects are: the materials used in construction for building facades and road surfaces. Starting from these two statements, we have extended the approach towards one of the meeting and mutual influencing points of the three factors: Light, People and Objects the urban public space. By analyzing the influences, actions have resulted, because it is important to point out the fact that, without lighting, a city would become non-existent during the nocturnal part of days. B. The practical premises associated with the condition of public urban lighting in Romania For a long time, the inhabitants of the contemporary Romanian city were left to wander in the nocturnal reality of the public spaces they lived in, already confused by the passage from day to night, which inflicts on them an alteration that modifies their behaviour and condition. And we need not neglect the reality offered by the geographic location which, for four months a year, the duration of the night is 14-15 hours, which means almost two thirds of a day. The current practice in public lighting is resumed to lighting according to a logic destined to car drivers, according to which pedestrians are offered, perhaps, additional safety in the vicinity of roads. Within the last 10-12 years, efforts have been made towards improving public street lighting and expanding the action scale to include the pedestrian and mixed spaces from the cities' central and residential areas. In the latter areas, in a few cases, the positioning and the selection of the lighting devices was made according to a lighting project, and the lighting devices used were, more often than not, devoid of an adapted optic system, which would allow a luminous flux oriented towards useful surfaces. In general, cities display a nocturnal image focused on the functional, with some luminous landmarks, here and there, achieved through lighting public buildings. Despite all these efforts to humanize lighting, the city, as a whole, is characterized by a lighting that is heterogenous, conflicting and devoid of identity. The contemporary city is marked by the deep transformation of the urban, where the human factor becomes a complex actor using multiple services and working within a continuously growing system, with which it interacts, by mutual influence. The thesis tackles the impact of such a change on lighting from the perspective of the evolution of two factors: human and environmental. Public lighting is involved in the process of designing a public space, both from its functional perspective and from its aesthetic one, actively participating in its correct definition. The image of the public space on daylight and its image at night need to be congruent. Furthermore, a city's public spaces need to communicate among them, so as the global image to be, in its turn, a coherent one. From this perspective, public lighting is an agreement between the public space and its users, the inhabitants.
Urban spaces are organized after a hierarchical typology, function of the space and the uses. Each type of space is associated with a specific type of lighting, with its own features and problems. The analytical approach, along with the principles of a «Plan General de Iluminat» (Lighting Master Plan), PGI, allow the mapping out of the global approach procedure and of the directions of nocturnal functioning of the city. The project is developed in subsequent conception, validation and coordination stages. The PGI is an evolutive approach, it establishes the state of the concept at a given moment and, because of that, it doesn't have to be considered a supreme, untouchable rule. The city evolves in both space and time, and the PGI accompanies and guides this evolution, without imposing constraints. Establishing the PGI at a city's scale involves grouping various decision factors: architects, designers, engineers, historians, politicians, sociologists, in multidisciplinary teams. The districts, the monuments, the patrimony works of art and the edifices, in a word, public spaces, need to be located and identified according to their importance in the city's image, because artificial lighting redefines the shape of an urban settlement. The PhD thesis is structured in six chapters. The introductive chapter presents the premises and the recentness of the paper. It also briefly recreates, in a reflexive-critical manner, the actual context of public lighting in Romania. It introduces a new approach to public lighting from the perspective of the human factor as a main character in addressing public space and it opens the way to future possible approaches to public lighting through the PGI. The second chapter deepens the relationship between Light and People based on two different approaches: The theoretical approach to light and vision, lighting and visibility, street lighting and visual task, mesopic vision according to the CIE 191:2010 standard and the influence of the mesopic vision theory on the design of the public street lighting systems. The analysis of Cluj-Napoca city inhabitants' perception on the public lighting system. Studying the Cluj-Napoca city inhabitants' perception on public lighting in their city, analysing the dependency of appreciations, preferences and perceptions on some socio-demographic factors: sex, age, level of education, ownership of a driving licence or the parent quality. The poll was conducted in 2011 on a group of 200 subjects, the data processing was done by means of the SPSS program, version 17. (Statistical Package for the Social Sciences). The majority of the Cluj-Napoca city inhabitants think that public lighting performs its basic functions and that their city is, in general, well illuminated, even if the lighting of the architectural elements and of the socializing spaces could be improved. 63% of the population agrees or totally agrees that public lighting provides a feeling of safety during nighttime travelling. The city's population pays attention to the lighting quality and makes a qualitative difference on the lighting of the streets analyzed. Regarding the aspects related to colour and style, the analysis clearly shows the city areas where the white colour of light is preferred to the yellow one. The study confirms that it is impossible for a lighting work to be compatible with the tastes of the entire population. Variables such as sex, level of education, age, produce the most evident population segmentation, but in a different kind of way, related to the appreciation of the lighting quality, of the aspects linked to colour and style and in the assessment of the risk areas. The driving license owners create the main severe segment in relation to the parking spaces lighting and that of the public and the proximity of private buildings. The study shows the small percentage of those that travel between midnight and 5AM. This finding leads to an additional means of improving lighting through luminous flux control in this timeframe, as follows: diminishing the luminous flux of the road lamps; constantly switching off architectural lighting during this timeframe, with the exception of the days/nights dedicated to some social city events. Chapter three is dedicated to the theoretical research of the coloured surfaces' behaviour (regarded as objects) under the influence of light sources customary to outdoor lighting. This chapter also covers some related subjects: 2
An experimental study regarding the assessment of visual perception factors in architectural lighting. Theoretical aspects linked to colour theory. Theoretical assumptions regarding colour theory (perception, qualities and composition of colours), light sources (rendering of colours, apparent colour), the CIE 1931 standard colorimetric system and the calculus of the chromaticity of the architectural objective's lit surface. The colorimetric descriptions of the construction materials used in finishing the lit surfaces - it presents the characteristics of the spectral reflexion of the most important materials used for finishing building surfaces or natural surfaces from the vicinity of buildings. The thesis exposes the results of a comparative study, regarding the behaviour of 45 surfaces types, more frequently used in construction, under the influence of various light sources. We determined the chromaticity coordinates (x, y) for the surfaces grouped into 6 typical categories, as follows: brick (9 samples), shingle (6 samples), metallic surface (5 samples), stone (5 samples), granite (10 samples) and surfaces covered with paint-type email (10 samples). In determining the chromaticity coordinates of the surfaces under discussion we used 15 light sources: 7 discharge lamps (one high pressure sodium discharge lamp, three metal halide with warm white light and three neutral white light), four LED sources with white light and different light temperatures and four LED monochromatic light sources. In order to determine the results, we defined a working platform, using a mathematical pre-defined tool, i.e. Microsoft Office Excel. Considering the inherent facilities mathematical and graphical ones of the previously mentioned tool, and furthermore its general accessibility and circumscribing all those facilities to the purpose of the theme, we proceeded to: 1. The use of the mathematical functions of multiplication of the vectors, that allowed the calculation of those three stimuli X, Y, Z, that, subsequently, by performing normalization operations, allowed to determine the chromaticity coordinates x, y; 2. The drawing of the chromaticity diagram of standard colorimetric system CIE 1931; 3. The positioning of the chromaticity coordinates for the used surfaces, correlated with the spectral diagram CIE 1931; 4. The import of colour images of the diagram CIE 1931, keeping the proportions, so that the position of the chromaticity coordinates be accurate. 5. The interpretation of the results through quantitative analysis in order to determine the association between the chromaticity coordinates of the analyzed surfaces and of the light sources. Theoretical research generated a mathematical model of association between the chromaticity coordinates of the materials and the chromaticity coordinates of white light sources. The mathematic model presents itself under the form of the chromatic straight line, on which results are concentrated in the form of line segments, longer of shorter, function of the characteristics of the material. The existence of a linear model leafs to possibilities of results prediction in case other white light sources than the ones analyzed are used. Studying the behaviour of the 45 materials used in construction works under the influence of 15 light sources has generated the following results: the values of reflectances and their spectral variation mode, for the materials analyzed, are specific to their colours; determining the chromaticity coordinates of the materials allows for a qualitative comparison of the way in which these chromaticity coordinates are influenced by a light source; the light sources generate a chromatic dispersion of the lighted materials on the inside and on the outline of the 1931 CIE colour space; each light source influences the chromaticity coordinates (x, y) of different materials function of their own chromaticity coordinates; the dispersal degrees of the chromaticity coordinates of the lighted materials around the chromaticity coordinates of the source is influenced both by the light source's own chromaticity and by the colour of the lit surface; 3
in the case of white light sources, each surface can be associated with a well verified mathematical model under the form of chromatic line, on which the results are concentrated in the form of line segments, longer or shorter, function of the surface type: o the most varied chromatic effects are obtained on blue-coloured surfaces (the biggest lengths for the chromatic line segments are obtained); o red-coloured surfaces represent the exception to the linear model, as the linear model is not sufficiently relevant in their case; the existence of a linear model leads to possibilities of result prediction in case other white light sources than the ones analyzed are used; knowing the apparent colour of the surface that needs to be lit from the initial phases of the design makes in situ experiments simpler, by reducing the costs and simplifying the process; on the basis of the analyzed pattern we can initiate the development on a new set of recommendation regarding the influence of light sources on some architectural surfaces. Chapter four refers to the lighting of road surfaces and the way in which they influence the efficiency of lighting systems and develops, in a logical succession, the following connected subjects: The reflexion properties of lit surfaces theoretical approach. The reflexion properties of road surfaces, detailed theoretical approach on: the parameters used to describe the reflexion properties of a road surface, classification systems for dry and wet road surfaces. Measuring the reflexion characteristics in the laboratory and in situ. The description of the Memphis mobile reflectometer and its functioning principle a specialized instrument used in the project, in the process of determining the luminance coefficients for 6 types of non-standardized road surfaces. The importance of knowing the characteristics of road surfaces reflexion for a street lighting system is based on the fact that the current quality criteria for lighting public roads is the medium luminance, which has to exceed a certain minimum level, imposed by the traffic security and visual control requirements. The average luminance level depends not only on the luminous flux received by the upper part of the road surface, but also by the relation between the distribution of light intensity by the lighting device used and the diagram of the road surface reflexion. The lighting systems designers cannot influence the road surface type used for a road, they can only get more acquainted with its reflexion properties by making field measurements using a mobile reflectometer, but this is a lengthy process. The accessible option for the designer in order to obtain an efficient lighting system, according to the requirements established by the design theme, needs to take place at the level of the lighting fixture selection, so that it presents a distribution of luminous intensity consistent with the geometry of the road and with the reflexion properties of the road surface. The PhD thesis proposes and presents a global assessment indicator of a public street lighting system the energy efficiency indicator, η i, - which takes into account not only the energetic efficiency of the lighting system, but also the attaining of its quality lighting parameters (the luminance distribution through general uniformity) and discourages the oversizing of a lighting system in its design phase. The indicator can be used straight from the design phase of a lighting system for the energetic evaluation of possible solutions. The energetic efficiency indicator does not influence the lighting quality, it is calculated for the street lighting system that fits all the performance criteria (average luminance, uniformities, physiological threshold increment, adjacent zone rapport if the case) for the selected lighting class, according to the CIE 115:2010 standard. The indicator, being calculated in the design phase, is a static indicator from the perspective of the lengthy evolution of the reflexion properties of the road surface. The thesis proposed and evaluation system using negative labelling with the purpose of encouraging the energetic efficiency with the end user. The labelling system is an instrument for the energetic assessment of lighting systems accessible also to non-specialists. Energetic labelling appears in the context of the research regarding the efficient use of energetic resources while respecting Eco-design principles. 4
Chapter five raises the issue of the relationship: public lighting public spaces population, starting from the role of lighting for a city, where environmental aspects linked to public lighting regarded as product and as system are emphasized. The experience gathered in the 17 years as practitioner in the outdoor lighting field and the observation of a certain degree of ambiguity related to lighting terminology brought about the intervention in the development and the detailing of outdoor lighting system classification. The thesis recommends the expansion of the current lighting systems classification in Romania, on two levels of approach, in relation to the lighting zone and their destination/scope. The thesis proposes the stages to follow in preparing a PGI, a framework document whose role is to guide the future actions in lighting a city. This may constitute a first step towards the reconsideration of lighting's role in town planning as an integral part of an Urban Master Plan. The sixth chapter presents the final conclusions and the author's contributions by means of this thesis. It also includes the proposed possible directions for continuing scientific research on the tackled topics. Personal contributions of the author: 1. Studying the Cluj-Napoca city inhabitants' perception on public lighting in their city, analysing the dependency of appreciations, preferences and perceptions on some socio-demographic factors: sex, age, level of education, ownership of a driving licence or the parent quality. 2. Defining a work tool, using a pre-defined mathematical calculus instrument, namely Microsoft Office Excel, with the purpose of determining and interpreting the behaviour patterns of coloured surfaces under the influence of various lighting sources. 3. Studying the behaviour of 45 types of materials frequently used in construction under the influence of 15 lighting sources. 4. Theoretical research has generated a mathematical association model between the chromaticity coordinates of materials and the chromaticity coordinates of the white light sources. 5. Measurements of the luminance coefficients, q, for 6 types of non-standardized road surfaces and the evaluation of their influence on projected lighting values. 6. Proposing and presenting a global assessment indicator of a public street lighting system the energy efficiency indicator, η i, - which takes into account not only the energetic efficiency of the lighting system, but also the attaining of its quality lighting parameters. 7. Proposing an evaluation system using energetic labelling with the purpose of encouraging the energetic efficiency with the end-user. 8. Proposing a «Plan General de Iluminat» and establishing its implementation stages. Directions for continuing research: 1. To maximize the study regarding the behaviour of the materials frequently used in construction under the influence of lighting sources through initiating a design guide. 2. Compiling a data base in regards to the reflexion properties of road surfaces, frequently used in Romania, which would take into account the changes caused by the time factor. 3. Researching the influence of the evolution in time of the reflexion properties of road surfaces on the energetic efficiency of a lighting system. 4. Quantifying the effect generated by the implementation of telemanagement systems for public street lighting on the energetic efficiency indicator, η i. 5