Estimation of lighting energy savings from daylighting

This paper refines and validates the predictions of a simplified analysis method for evaluating the potential of daylighting to save energy use associated with electrical lighting. Specifically, impacts on daylighting performance are investigated for several combinations of building geometry, window size, and glazing type for several US and international locations. The impact of both dimming and stepped daylighting controls and their settings are also investigated. Predictions from the simplified method are validated using measurements obtained from field-testing of a daylighting control system utilized to operate lighting fixture illuminating an office space.     

Simplified daylighting energy savings for non-daylighting building energy simulation programs

The California Legislature mandated the California Energy Commission (CEC) to establish and periodically update energy efficiency standards for new buildings. To this end, a sensitivity analysis was conducted by the Standards Development Office of the California Energy Commission for nonresidential buildings. The purpose of this parametric analysis was to determine which variations in building parameters actually have significant energy impacts.A “generic” building model was developed and implemented in conducting this sensitivity analysis. The generic model was used as an analytical tool in modeling the energy impact of building parameter variations, as well as architectural and mechanical energy-saving measures on the energy use of each module. It is recognized that the level of significant energy impact is equivalent to, or bounded by the accuracy of the energy analysis tools in predicting energy usage in actual buildings. For the computer program used, DOE 2.1A this accuracy is within ±5%.Since DOE 2.1A and most of the other building energy simulation programs do not have daylighting algorithms, another calculation tool was used to determine daylight availability and lighting power reduction on an hour-by-hour basis for each orientation. This is accomplished with a daylight reduction factor (DRF).Quicklite, a simplified daylighting program, calculated footcandle (lux) levels based on outdoor ambient light levels, physical room dimensions and properties. To assess the impact of the Quicklite calculated footcandle (lux) levels on artificial lighting use, a control scheme was assumed, and a DRF was calculated based on annual sky conditions by climate zone.Once the DRF values are known for each orientation, the electric lighting schedule can be modified. A new profile number, representing the proportion of installed lighting switched on at that hour, replaced the daily lighting schedules when daylighting was utilized (09:00 – 17:00). To test this methodology, a sensitivity analysis was conducted between DOE 2.1A with Quicklite modifications and DOE 2.1B which has a daylighting preprocessor. The results displayed a 3.6% variation in total energy use.We conclude that daylighting calculations for design days using simplified programs can be used to approximate daylighting energy savings in building energy simulation programs that allow zoned lighting schedules but do not calculate daylight contributions.     

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.     

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.     

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.     

Mutual impacts of lighting controls and daylighting applications

Several types of lighting control strategies, techniques, and equipment are examined with respect to cost and performance. Daylighting is found to require the use of sophisticated equipment that can provide more than this one control strategy. Simple control systems can reduce the lighting load by 12 – 50%; implementing four control strategies provides savings of 60 – 79%. The four control strategies are scheduling, tuning, lumen depreciation, and daylighting. The use of daylighting, properly integrated with electric lighting, makes economic sense and will be more commonly practiced in the future.     

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。     

A case for ‘active’ daylighting by appropriate management of electric lighting

Understanding of how occupants of non-domestic buildings use electric lighting, gained from behavioural studies, indicates that the mere provision of daylighting is unlikely to lead to its useful uptake. It is suggested that the design of appropriate electric lighting control systems, including those requiring occupant action, can be related to occupancy patterns of space use and daylight availability in the space and that provision of such systems should be seen as ‘active daylighting’. It is also suggested that design for ‘active daylighting’ requires more accurate prediction of daylight availability in interiors.     

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 dynamic sky recognition method for use in energy efficient lighting design based on CIE standard general skies

This paper innovatively proposes an “active green lighting model” for control and optimization of building luminous environment. It is expected to optimize the utilization of daylight dynamically in energy efficient lighting design from the viewpoint of intelligent control. As one primary work of implementing the overall model, the luminance distribution of CIE standard general Skies is addressed, and a dynamic sky recognition method for utilization optimization of daylight is proposed based on swarm intelligence. The experiment results of instance field data show the proposed intelligent sky recognition method is feasible and effective.     

A sensitivity analysis method for water distribution system tank siting for energy savings

Energy savings in water distribution system (WDS) pumping can save the municipality money and reduce the amount of greenhouse gas emissions. A straightforward method is introduced here that allows any WDS manager to determine source-tank location and connectivity that minimizes pumping energy usage. The method is demonstrated on twelve diverse WDSs to investigate whether less pumping energy is used by having the tank at four key locations. It was found that the new method worked well and identified that having the tank near to the system and connected directly to the source saves pumping energy in all of the WDSs analyzed. If the initial cost of relocating the tank for existing systems or locating the tank near to the source in new systems is less than the cost of energy savings over the lifetime of the tank, then having the tank near to the source is financially worth it.     

Synthesis of artificial lighting to satisfy multiple design criteria

The illuminating engineering design process is concerned with the synthesis of lighting systems to satisfy a number of design criteria. In the past this process has been accomplished intuitively by the experienced designer and the resulting solution analysed against a limited number of design criteria using ‘lumen design’ techniques. This process has the advantage of being economical in terms of design time, but it ignores many recently developed quality aspects of lighting design. This paper describes a computer-aided approach to the lighting design problem, based on the multiple criterion design technique, that automatically synthesises design solutions based on both quality and quantity criteria of design.     

A novel method to model trees for building daylighting simulation using hemispherical photography

The ability to simulate the effect of trees on natural light performance in buildings is contingent upon accurate simulation of light passing through the canopy. Accurate simulations require some assumption of leaf angle distribution (LAD) to compute canopy gap fractions. The ellipsoidal LAD can very closely approximate real plant canopies. The method requires calculation of leaf area density from observed distribution of gap fraction as a function of zenith angle. Two sets of Neem trees were studied (small and large). Hemispherical image acquisition and analysis for both groups was carried out to measure gap fractions. The results helped to develop a 3D tree model that was used to simulate the effect of tree interception of daylight. The illuminance levels were simulated under the tree model and the output results were validated against actual measurements using MBE and RMSE techniques (small trees: MBE = 0.33, RMSE = 0.20; large trees: MBE = 9.68, RMSE = 2.02).     

A generative facade design method based on daylighting performance goals

Successful daylighting design is a complex task which requires the designer to consider numerous design elements and their effects on multiple performance criteria. Facades, in particular, include many variables which may dramatically impact daylighting performance. Genetic algorithms (GAs) are optimization methods which are suitable for searching large solution spaces, such as those presented by design problems. This article presents a GA-based tool which facilitates the exploration of facade designs generated based on illuminance and/or glare objectives. The method allows the user to input an original 3d massing model and performance goals. The overall building form remains the same while facade elements may change. Ten parameters are considered, including materials and geometry of apertures and shading devices. A simple building data model is used to automatically generate a 3d model of each solution. Results from single- and multi-objective case studies are presented to demonstrate a successful goal-driven design exploration process.     

门窗与建筑节能

就一般建筑而言,门窗面积约占建筑外围护结构面积的30%,而门窗的能耗约占建筑外围护结构热损失的50%,所以应用节能门窗对实现建筑节能十分关键。     

Domestic lighting: A high-resolution energy demand model

The use of electric lighting in the domestic sector depends mainly on the level of natural light coming in from outdoors, coupled with the activity of the household residents. This paper presents a detailed model of domestic lighting use that takes these two factors as its basic inputs. The operation of individual bulbs is represented within the model and is used to construct high-resolution lighting electricity demand profiles for individual dwellings. The model is computationally efficient and can easily provide data at 1-min resolution for large numbers of dwellings. As a primary input, the model uses a time-series representing the number of active occupants within a dwelling (people who are at home and awake). This allows it to represent the sharing of lighting between the occupants of a given dwelling and facilitates correlated linking to models of other energy use within the dwelling. Appropriate correlation between dwellings is achieved through the use of appropriate active occupancy data and outdoor ambient light data. An example implementation of the model in Microsoft Excel is available for free download.     

推进绿色照明 缓解能源紧张

介绍了我国当前的能源紧张状况及浪费严重的现象,提出了推进绿色照明,节约能源及保护环境的重要意义,并配合新编国标GB 50034-2013建筑照明设计标准的实施,从设计的角度对新标准的要求与做法进行阐述,结合实例分析了设计中应注意的事项。