Lighting Control Systems: Factors Affecting Energy Savings' Evaluation☆

Abstract The use of automated lighting control systems allows to reduce lighting costs and to achieve significant energy savings. The energy performances of controls are affected by many factors, the impact of which is very difficult to account for during the design process. The goal of this paper is to describe the factors that influence the control systems' energy performances, to analyze how the currently available calculation tools take them into account and finally to propose a simple method to adjust results obtained from the simulation software

Evaluation of Daylight Availability for Energy Savings

Dynamic daylight simulations are very useful instruments in daylighting design process. They allow an in depth analysis of indoor daylight availability levels and define if they are adequate to perform a particular visual task. Their results can be used to design shading devices or lighting control systems and compare different technical solutions. The use of these simulations is likely to spread in the common design practice since some regulations and green building rating systems suggest their use. This paper presents dynamic daylight simulation results related to an open-plan office, performed with Autodesk 3ds Max Design®, which is a calculation software validated by recent researches. It is not used in academic context but it is very widespread between technicians for photorenderings production purposes. The goal of this research is to demonstrate the functionality of this software also in dynamic daylight simulations field and propose an analysis' methodology to use it

Methods to Evaluate Lighting Quality in Educational Environments

Abstract The current standard for lighting of indoor work places (EN 12464-1) essentially prescribes values of photometric quantities (illuminance, Unified Glare Index, etc.); therefore it does not allow a comprehensive analysis of the luminous environment. In Italy, educational buildings do not always comply with the standard requirements for lighting. Therefore an analysis of their current state is needed and this paper illustrates two methods, developed by the authors, to carry out this investigation: the former is based on the analysis of luminance maps obtained through the HDR imaging technique whereas the latter focuses on the evaluation of non-visual effects of light

Proposta di una metodologia per illuminare i centri storici

La corretta illuminazione di uno spazio urbano non può prescindere da uno studio accurato dei materiali, dei colori e da un'approfondita conoscenza storica ed architettonica del contesto: molto spesso vi sono delle incertezze nel condurre in modo sistematico questi studi preliminari e non vi è una metodologia di riferimento per affrontare la progettazione in contesti così complessi. Per questi motivi in questo articolo si propone una metodologia che rappresenta un tentativo di fornire una guida per progettare la luce rispettando i materiali, i colori e l'architettura di uno spazio urbano. L'illuminazione delle cortine edilizie, delle piazze e dei monumenti differisce profondamente dall'illuminazione stradale che è sottoposta ad altre regole ed esigenze e la metodologia qui presentata è orientata alla progettazione dell'illuminazione per le aree non destinate al traffico veicolare. Per testare questa metodologia si è scelto un caso studio individuato da uno spazio urbano esistente all'interno del centro storico di Napoli: Piazza Sisto Riario Sforza. La scelta di questa piazza è stata fatta in quanto essa è esemplificativa della cattiva illuminazione spesso riscontrabile in simili contesti

The colour of light for urban spaces

Light in urban spaces was first introduced to prevent crimes against both people and properties and, while there is no study that confirms crimes' reduction in lit spaces, it is undeniable that people feel safer in lit urban spaces. Over the years it became evident that light can also improve the liveability of cities and enhance their characteristics, therefore in the last years a growing attention was paid to urban lighting design taking into account the environmental impact and energy saving requirements too. The will to use the lighting design project to improve the liveability of historical centres it’s clear: the city during the night is no more conceived like a sum of lit architectures but, thanks to a good lighting design project, it could complete the image that the city has during the day with perspectives, views and glimpses correctly illuminated, giving a global sense of the environment while making it safer. To properly highlight building facades and monuments, an accurate study of materials and chromaticity needs to be conducted and in this paper a methodology to do so is proposed. This method was developed after a research on the evaluation of chromatic changes of objects lit by sources with different SPDs and it is also based on the concept of visual saliency. Visual saliency is the perceptive quality that makes an object discernible and capable of instantly catching the eyes and mind attention; our brain automatically creates "saliency maps" of everything we see and using an algorithm it is possible to graphically recreate these maps to understand what attracts the eyes' attention in order to enhance it. Luminance is one of the factor that adds or takes saliency to an object: by increasing or decreasing luminance values it is possible to attract or repel the eyes' attention. Today there is a tendency to recommend a specific luminance ratio between an object and its background, using a higher luminance contrast to achieve a higher visibility level and this is typical of objects with a uniform background. However, in urban situations objects have complex backgrounds and it is important to remember that an object's saliency also depends on its background. A single salient target draws the attention irrespective of the number of the other not salient elements on the background, but when these elements increase in luminance, the main target loses visibility and saliency. It is also really important to consider that there may also be different levels of saliency. The methodology was then applied to a case study in the historical centre of Naples

Winter and summer analysis of daylight characteristics in offices

This paper reports a comparison of the results of daylight measurements carried out in summer and winter in three offices, with different exposures and characteristics, located in Naples (Italy). The aim was to extend and enrich the findings of a previous study which reported the results of summer measurements about desk illuminances and circadian impact. The research project includes measurements carried out in other seasons and a comparison between measured and software simulated values with the final goal of developing design guidelines. This research confirmed that the spectral distributions and CCTs of the light reaching the eye of a person seated at the desk in these offices are similar, irrespective of the different sky's conditions and season and of the rooms' different characteristics (dimensions, surfaces' spectral reflectances, external obstructions, etc.). It was also confirmed that eye level irradiances and thence their circadian impact are similar to those of D50 and D55 CIE standard illuminants

Lit environments quality: A software for the analysis of luminance maps obtained with the HDR imaging technique

Energy performance of lighting systems has assumed a significant role in the assessment of buildings’ consumptions and consequently lighting design is aimed to reduce installed power but at the same time to achieve an excellent lighting quality both for visual and health purposes. Lighting design is nowadays essentially based on illuminance values on visual tasks and surrounding areas, but today designers’ and researchers’ interest is focused on the analysis of luminance maps obtained through video luminance meters or with numeric simulation tools. Luminance maps availability focus the attention on a more accurate study of the light reaching the eyes (luminance), rather than on the light that arrives on surfaces (illuminance). However luminance values, based on photopic sensitivity, do not always adequately describe the quality of a lit environment and how it is perceived; therefore it is necessary to consider parameters like brightness or equivalent luminance. The first part of this work describes primary factors that influence lit environments’ perception along with the main available luminance–brightness relations. Moreover a software for the luminance maps’ analysis is described with the goal of finding and testing the most significant parameters for the lit environment’s description, both for comfort and energy purposes

Perceived and measured hues under different sources

The diffusion of LED lamps for interior lighting, which possess spectral power distributions (SPDs) that considerably differ from the traditional light sources' ones, arose some questions on colour perception, and particularly on colour appearance. These questions led to a debate about the efficacy of CRI and the need of other indexes to evaluate colour quality of lighting sources. An experiment of colour evaluation has been carried out in a test room lit by LED lamps with very high CRI and three different CCTs. Some results were compared to colour attributes derived by applying the CIECAM02 model to measured data

Indoor lighting quality: Effects of different wall colours

This paper reports the results of measurements performed in a test room to investigate the impact of using different wall colours and light scenes on indoor lighting quality. Eye level spectral irradiances were measured for a user located inside the room and seated at a desk. These measurements allow the use of the Irradiance Toolbox, which makes it possible to calculate equivalent illuminances for the photopigments in the human eye. Moreover, the CIECAM02 colour appearance model was used to investigate the variations in hue and chroma values of the different wall colours when changing the light scene. The results demonstrate that there are significant variations in eye level spectral irradiance distributions, photoreceptor stimulation and hue and chroma values with different combinations of wall colours and light scenes

L'accesso di luce naturale negli ambienti interni. Considerazioni sulla scelta dei software

L'impiego della luce naturale per illuminare gli interni degli edifici ha molteplici effetti positivi tra i quali il comfort ed il contenimento dei consumi energetici. Poiché la luce naturale è una risorsa estremamente variabile nel tempo, la sua corretta modellazione e l’individuazione di parametri caratteristici quantitativi e qualitativi sono essenziali per comprendere quale sia la sua reale disponibilità in ambiente durante l’anno e quali siano gli scenari luminosi che essa determina. Per la complessità della valutazione dell’accesso e della distribuzione della luce naturale, è indispensabile l’utilizzo di software specifici, ma gli applicativi disponibili per il calcolo illuminotecnico sono numerosi e spesso può risultare complicato individuare quello più adatto alle proprie esigenze