Evaluating the potential for energy savings on lighting by integrating fibre optics in buildings

The effective integration of an artificial lighting system and daylight in buildings occurs only when the artificial lighting system can be switched on or off as a function of daylight levels reaching the working surface of spaces. The paper considers fibre optics technology as a means of supplementing the daylight received at the rear of rooms and the subsequent integration of the total daylight received with a controlled artificial lighting system. Such an approach would contribute not only to energy savings but also to a reduction in environmental pollution. The evaluation took place using the climatic data from seven cities in Brazil and one in the UK. Results showed that by effectively integrating daylight from windows in buildings with the artificial lighting system, energy savings ranging from 17.7% to 92.0% could be achieved in the seven cities in Brazil and savings ranging from 10.8% to 44.0% could be achieved in the UK. By incorporating fibre optic technology into the system, the potential for energy savings on lighting was then found to range from 8.0% to 82.3% for the cities in Brazil and from 56.0% to 89.2% in the UK. For the city in the UK, it was further shown that there would be a reduction in carbon dioxide emission of 122 kg/m² of built area per year if daylight from windows were integrated with the artificial lighting system, and that this would increase to 138 kg/m² per year if fibre optics technology were to be installed.     

A simplified method to estimate energy savings of artificial lighting use from daylighting

This paper provides a simplified analysis method to evaluate the potential of daylighting to save energy associated with electric lighting use. Specifically, impacts on daylighting performance are investigated for several combinations of building geometry, window opening size, and glazing type for four geographical locations in the United States. Four building geometries with various window-to-floor areas, along with different glazing types have been analyzed. It was determined that for most commercial buildings with glass transmittance values above 0.5, increasing window area to floor area ratio above 0.5, daylighting does not provide significant additional lighting energy savings. A direct correlation has been established between window transmittance and window area on annual lighting reductions. A model is proposed to estimate lighting energy savings given perimeter area, window area, and window type. Verification and validation of the model's predictions are demonstrated using results from building energy simulation as well as experimental data.     

Analysis of different models to estimate energy savings related to windows in residential buildings

A Window Energy Rating System (WERS) provides a simple, approximate method to compare the energy performance of the various windows and to determine the different potential savings for the various weather conditions. The main aim of this paper is to obtain a WERS for two climatic zones in Spain.For this purpose, the heating loads and energy savings of a residential building with different types of windows were obtained by three ways. Firstly, the energy through the window was evaluated considering only the climatic conditions. Secondly, the study was performed taking into account the energy useful for the heating system considering the climate and the type of building. Finally, the different cases were simulated using TRNSYS16 and WINDOW5. This study was performed for different European climates.The WERS proposed here is based on the second method. It takes into account the U factor of the window, U factor of the frame, absortivity of the frame, solar heat gain of the glazing and infiltration.     

Quantifying energy savings in daylight responsive systems: The role of dimming electronic ballasts

The application of lighting control technologies with photosensors has led to an increase in public interest. Although these technologies have been promoted during the last years their successful use in buildings has been accomplished in a small percentage of new projects. One reason is the difficulty in quantifying the energy savings and thus the subsequent payback period. Daylight responsive dimming systems consist of three basic components: photosensor, controller, and dimming unit. Electronic dimming ballast (EDB) is one substantial component of these lighting control systems which can adjust the light output due to the transferred signal from the photosensor and lighting controller. The aim of this study is to quantify energy savings among different EDBs. Eighteen commercial EDBs were selected and various sets of electrical and illuminance measurements were taken for different dimming levels, in order to develop polynomial functions between light output and consumed power. Using the measured data, a set of simulations were performed for a photosensor with an ideal cosine spatial sensitivity distribution installed in a typical office room using two control algorithms, closed loop and integral reset, trying to quantify the relative differences in energy savings.     

Lighting energy savings in offices using different control systems and their real consumption

This paper compares the potential of lighting energy savings in office rooms by using different control systems, for three locations in Europe and the four main orientations. The method is based on DAYSIM simulations to perform daylight calculations, on laboratory measurement to evaluate precise system energy consumptions and on the implementation of a new algorithm to simulate a close-loop daylight dimming system. It appears that the control of the electrical power in function of daylight leads to very high savings; they slightly depend on the room orientation and the location. Savings vary from 45 to 61%. The performances of an occupancy sensor are also tested. Threshold values of occupancy rate for which daylight dimming leads to higher gains than an occupancy control system vary between 27 and 44% depending on location and orientation. The measurements of the energy consumption of the sensors and detectors also permit to conclude that systems with embedded DALI-compatible ballast controllers should be abandoned in favour of a centralized DALI-compatible ballast controller or embedded analogue systems.     

Impact of electricity rate structures on energy cost savings of pre-cooling controls for office buildings

This paper summarizes the results of a series of parametric analyses performed to evaluate the impact of key design and operating conditions on the effectiveness of pre-cooling control strategies for reducing peak demand and overall energy costs for office buildings. The analyses were carried out using EnergyPlus, a whole building energy simulation program. The effects of various parameters were considered in the analysis including building location, mass level, pre-cooling control strategy, and time-of-use utility rate.     

Use of microencapsulated PCM in concrete walls for energy savings

This paper studies a new innovative concrete with phase change materials (PCM) on thermal aspects. The final objective is to develop a product which would achieve important energy savings in buildings. The work here presented is the construction and experimental installation of two real size concrete cubicles to study the effect of the inclusion of a PCM with a melting point of 26 °C. The cubicles were constructed in the locality of Puigverd of Lleida (Spain). The results of this study show the energy storage in the walls by encapsulating PCMs and the comparison with conventional concrete without PCMs leading to an improved thermal inertia as well as lower inner temperatures.     

Use of diffusers materials to improve the homogeneity of sunlight under pergolas installed in road tunnels portals for energy savings

In spite of the benefits of shifting the threshold zone of road tunnels by means of pergolas, installed before their portal to save energy in the electrical lighting, the lack of uniformity in the road under these structures makes them a non accurate solution in terms of visual performance and, hence, road safety. In this work, a new solution, consisting on the introduction of a diffuser material in the spaces between beams of the pergola is proposed. The measurements and results in a scale mock-up, a computational simulation and the comparison with a theoretical model, as well as the potential impact in real tunnels are presented and analyzed.     

Thermal energy savings in buildings with PCM-enhanced envelope: Influence of occupancy pattern and ventilation

Integration of building materials incorporating PCMs into the building envelope can result in increased efficiency of the built environment. A PCM-enhanced wall system is proposed in this paper and a simplified model for the heat exchange between the indoor environment and ambient was developed. The objective of the study was to assess the effect of occupancy pattern and ventilation on the energy savings potential of the wall system. It was found that (1) the occupancy pattern influences the value of the PCM melting point for which maximum energy savings value was reached and (2) the ventilation and its pattern reduces the relative value of the energy savings.     

Thermotropic glass with active dimming control for solar shading and daylighting

The effectiveness of an autonomous responsive dimming (thermotropic) glass panel fabricated with a transparent heating layer and an electrochromic layer to provide additional active dimming control is examined through preliminary experiments and simulations. Thermotropic glass consists of two panes of glass sandwiching a polymer gel that undergoes a transition from clear to cloudy at a threshold temperature. Winter temperatures can thus prevent the glass from dimming when required for solar shading. With appropriate control of the heating layer, however, the performance of the panel with respect to office solar-shading requirements is demonstrated to be superior to that without the heating layer, despite the simplicity of the system. The configuration requires relatively low electric power, utilizing solar radiation energy to maintain the cloudy state as required. In a different approach, application of electrochromic layer for active dimming control is proposed and verified in various aspects with wavelength characteristics considering simulation.     

Impact of electric lighting efficiency on the energy saving potential of daylighting from roof monitors

A developmental version of the building energy analysis computer program BLAST was used to perform simulations of a prototypical, single-story office building. Total annual energy consumption was computed using Typical Meteorological Year (TMY) [1] weather data from three locations in the United States. For each location, two electric lighting designs were tested on the baseline building (no roof monitors) to compare the energy requirements of current-practice and more efficient electric lighting designs. Then roof monitors were added to evaluate their energy saving potential for each of the electric lighting designs. The roof monitors had highly diffusing, vertical glazings facing southeast and southwest.The results show that improving electric lighting system efficiency and adding roof monitors for daylighting both have the potential for substantially reducing lighting electricity and the energy cost of operating the building. The potential benefits of daylighting are substantially lower for a building outfitted with a more efficient electric lighting system, although still significant. To determine the limits of validity of the simulations, a number of sensitives studies were performed. Among the issues investigated were: dirt deposits, snow accumulation, glazing optical properties, interior design, luminous efficacy of admitted sunlight, and thermostatic controls.     

Overview and new developments in optical daylighting systems for building a healthy indoor environment

Optical daylighting technology can deliver natural light to a space in a building where daylight is limited. This study gives an overview of two optical daylighting systems for capturing natural light: light pipe systems and mirror sunlighting systems. The literature on optical system theories and developments is identified and commercial products for optical daylighting systems on the market are described. By using a survey of major applications for optical daylighting systems, this study provides practical advice to building designers and researchers and also shows a light pipe system and a mirror sunlighting system developed from this investigation as well as an evaluation of their performance. The evaluation measured the illuminance of the two optical systems installed in a test room and a living room. This study concluded that optical daylighting systems can provide adequate visual comfort and can save energy if they are carefully designed.     

Predicting lighting energy use under daylight linked lighting controls

For daylight to make a real contribution to energy efficiency, appropriate control of electric lighting is essential. This paper outlines methods to predict electric lighting use for various different types of control, given internal daylight illuminances. Two different kinds of calculation are considered. Annual lighting use can be determined from yearly daylight data, usually in the form of a cumulative distribution. More sophisticated computer programs use hourly daylight data to give a continuous profile of lighting use and the consequent energy flows and environmental conditions within a building. For both types of application, appropriate algorithms are given to quantify the savings from various types of photoelectric and manual controls.

Pour que la lumière du jour apporte une réelle contribution au rendement énergétique, il est essentiel de bien contrôler l'éclairage électrique. Cet article décrit brièvement les méthodes qui permettent de prévoir l'éclairage électrique utilisé en fonction de différents types de contrôle, compte tenu de l'éclairement assuré par la lumière du jour intérieure. Deux types différents de calcul sont pris en considération. L'utilisation annuelle de l'éclairage peut être déterminee à partir des données annuelles relatives à la lumière du jour, généralement sous la forme d'une distribution cumulative. Des programmes informatiques plus complexes utilisent des données horaires sur la lumière du jour pour obtenir un profil continu de l'utilisation de l'éclairage ainsi que les flux d'énergie correspondants et les conditions d'environnement d'un bâtiment. Les auteurs donnent pour deux types d'application des algorithmes appropriés qui permettent de quantifier les économies correspondant à divers types de commandes photoélectriques et manuelles.     

An analysis of daylighting performance for office buildings in Hong Kong

Daylighting has often been recognized as a useful source of energy savings and visual comforts in buildings. Occupants expect good daylight in their working spaces. The quality and quantity of natural light entering a building depend on both internal and external factors. In Hong Kong, commercial building accounts for the major building energy use and electric lighting is one of the major electricity-consuming items. This paper studies the daylighting performance and energy implications for office buildings. A total of 35 commercial buildings have been selected in the survey. Key building parameters affecting daylighting designs are presented. Two typical office blocks were further analysed based on a lighting simulation program. The daylighting performance was evaluated in terms of daylight factor, room depth and glare index. It has been found that the daylighting performance for office buildings is quite effective. About one-third of the office areas that are near the perimeter regions have an average daylight factor of 5%. For inner region of deep plan offices, some innovative daylighting systems such as light redirecting panels and light pipe could be used to improve the daylighting performance. In general, the office building envelop designs are conducive to effective daylighting and proper daylight linked lighting controls could save over 25% of the total electric lighting use.     

Photometry and colorimetry characterisation of materials in daylighting evaluation tools

This paper presents a methodology for evaluating the photometric and colorimetric characteristics of internal building materials, for daylight evaluation. The assessment of these characteristics is crucial both for modelling materials accurately in daylight simulation tools and for building correct daylight mock-ups. The essential photometric and colorimetric parameters that influence the reflection of light from and its transmission through building materials are identified and described. Several methods for evaluating these parameters qualitatively and quantitatively are then proposed and discussed. Our new methodology was fused to create a database of materials in a freely accessible web tool which compares full-size materials to scale-model materials in order to help architects and lighting designers choose materials for building daylight scale models.     

建筑采光和照明新技术

就新型建筑采光和照明技术作了论述，通过了解采光和照明发展的新趋势，以方便我们合理的选择和恰当运用照明技术，从而创造出理想的照明环境，体现光建造空间的魅力。     

Rapid visualization of the potential residential cost savings from energy storage under time-of-use electric rates

Buildings feature a prominent role in electric grid loading, as they use about 75% of the total electricity generated in the United States and are main drivers of electric peak demand in the summer due to electrically driven air conditioning systems. Energy storage is a key technology that can increase energy cost savings, and add flexibility to the grid. However, cost is an important factor to consider. This study proposes a rapid approach that allows for visualization of potential cost savings by introducing energy storage as a peak load control for residential buildings in California. A combination of EnergyPlus load data generation, Matlab post-processing, and Google Fusion Tables data presentation analyses the potential cost savings when energy storage is implemented and TOU rates are applied. The study presents potential annual cost savings of $420 per home with storage capacities of 24?kWh.     

Statics of space syntax: Analysis of daylighting

Space syntax involves a set of techniques for analyzing the spatial configurations of various spaces at building and urban scales. Religious spaces, such as prayer halls, are examples of buildings where observers experience space mostly from a single point of view. Furthermore, traditional space syntax is mainly used in the analysis of visibility and space cognition in terms of isovists and graph-based measures. The other aspects of space cognition, such as day lighting, artificial lighting, and glare, are carried in the isolation of the space syntax analysis. This paper proposes the scaling of the space syntax field for the inclusion of other parameters, such as daylighting, and integration of the associated performative measures to space syntax analysis of the mosque typology to aid in the studying of overall space cognition based on comfort and environmental parameters. We present a case study on a typical mosque layout using multi-objective optimization. The analysis presented in the paper has implications for the architectural designs of spaces with respect to glare management and daylight potential. Moreover, it is unique and builds on our previous work for the exploration of comfort, visibility, and proximity thresholds for stationary observers.     

Passive cooling for air-conditioning energy savings with new radiative low-cost coatings

Passive cooling is considered as an alternative technology to avoid unwanted heat gains, to reduce urban heat islands and to generate cooling potential for buildings (limiting air-conditioning energy). According to materials and surface treatments, the roof can represent to be a major heat gain source from opaque elements of the building fabric, heating up the outer surface and increasing heat flow by conduction. This paper presents low-cost new radiative materials (1 ∉/m²) allowing to limit heat gains during diurnal cycle for hot seasons. To evaluate the relevance of these new substrates, their reflective UV-VIS-IR behavior are studied and compared to classical roofed materials available in industrial and developing countries. A 48 m² experimental roof having different surfaces (plate steel sheets, fiber cement, terra cotta tiles and corrugated sheets) allows to determine the temperature ratio δ between uncoated and coated materials. Up to 34% surface temperature gains are obtained for white coated CS, 25% for FC and ∼18% for TCT and PSS. According to uncoated materials for a surface temperature T₀ = 60 °C, simulations showed that the low-cost white opaque reflective roofs (50 m²) presented in this study would reduce cooling energy consumption by 26-49%.