Proceedings of Building Simulation 2011: 12th Conference of International Building Performance Simulation Association, Sydney, 14-16 November. INTEGRATED COMPUTER SIMULATION FOR CONSIDERING DAYLIGHT WHEN ASSESSING ENERGY EFFICIENCY IN BUILDINGS Evelise Leite Didoné1 and Fernando Oscar Ruttkay Pereira2 1 e 2Universidade Federal de Santa Catarina – UFSC, Faculdade de Arquitetura e Urbanismo, Florianopolis, Brazil Since daylight is extremely variable, it is necessary to ABSTRACT deepen the concept of dynamic measures in order to Daylight is an important strategy for reducing energy evaluate daylight in indoors environments. By using consumption in buildings. In order to predict it, the these measures it is possible to describe in detail the use of weather-based simulation programs that behavior that results from the interaction between a employ the Daylight Coefficients concept is building and the local climate. An annual data base recommended. EnergyPlus, a program for thermal is used, providing a design that is closer to the local energy simulation, is one of these tools; however, it reality [Reinhart et al., 2006]. In order to achieve this has shown a significant limitation regarding the goal, there are daylight simulation tools that facilitate daylighting module, since it tends to overestimate models simulations by using complex geometries. daylight in internal environments. In order to get Daysim is a computer simulation tool developed by around this limitation, the present work proposes a Reinhart [Reinhart, 2006], which calculates the methodology to evaluate energy efficiency, annual indoor illuminance profile using weather- considering the use of daylight, through an integrated based files. This trend is currently observable in most simulation using two distinct programs. This programs for simulating thermal energy behavior. methodology entails evaluating energy and light The application that uses the weather-based file is performance through simulation using the Daysim different from others, since it is able to predict the and EnergyPlus programs. Daysim generates a report amount of daylight in an environment during an that describes the control of the artificial lighting entire year. Static simulation programs only simulate integrated to daylight, which is used by EnergyPlus the phenomenon under a predetermined sky for calculating the final energy consumption in the condition. analyzed environments. The results indicate that the In order to overcome this limitation, this work proposed methodology is capable of compensating describes a methodology to evaluate energy the limitations of EnergyPlus and, in this way, allow efficiency. It considers the use of daylight through an to evaluate energy efficiency in buildings, integrated simulation using two programs, Daysim considering the admission of daylight. This work and EnergyPlus, which evaluate energy and light shows an alternative and reliable way for considering performance [Reinhart et al., 2011]. Daysim daylight when evaluating energy efficiency in generates a report that describes the artificial lighting buildings. control used in EnergyPlus simulation, which INTRODUCTION calculates the final energy consumption within the analyzed environments. The results indicate that this Artificial lighting in indoor environments, along with methodology could compensate the limitations of artificial conditioning systems, is responsible for a EnergyPlus and may as well evaluate energy large amount of energy consumption in efficiency in buildings, by considering the use of contemporary office buildings. This situation can be daylight. This work shows an alternative and reliable reversed when the buildings are equipped with course for including daylight use when evaluating devices associated with more effective design energy efficiency in buildings. strategies that prioritize the use of daylight and Some tools are able to perform an integral analysis ventilation. The use of daylight in these buildings, concerning daylight illuminance, refrigeration and besides ensuring adequate lighting levels for human heating systems. EnergyPlus is one of them, since it activities, reduces the need for the use of artificial provides per hour results and conducts thermal light. Also, when in conjunction with an efficient energy simulations. Therefore, it provides a more control of artificial lighting and the existence of detailed building performance assessment. However, openings and equipment, it influences the EnergyPlus presents some limitations in its natural environmental thermal gain and the total energy lighting system algorithm [Winkelmann et al., 1984]. consumption. It is important to point out that daylight This restriction was also confirmed by Ramos and is widely available during the day, which is the Ghisi [2010], who verified a strong influence of this period when non-residential buildings are used. program when calculating natural lighting. It affected - 2102 - Proceedings of Building Simulation 2011: 12th Conference of International Building Performance Simulation Association, Sydney, 14-16 November. the calculation of the portion of reflected light on the ceiling height of all models was 2.70m, excepting for environment as well as the calculation of external model 4. Its ceiling height was 3.50m, in order to lighting, which ended up being larger than the real study the influence of the environment height on one. In other words, EnergyPlus overestimated the daylight distribution (See Figure 1). amount of daylight in indoor environments and, as a result, it underestimated electric energy consumption used in artificial lighting. Several studies have proved that the use of daylight is able to save a significant amount of electricity used in lighting. In Brazil, some studies have been carried out in order to characterize commercial buildings from the perspective of energy consumption, considering the use of daylight. Souza [2003] proposed a methodology to estimate the Potential of Use of Daylight (PUD) through the use of automatic control systems for saving electricity spent on lighting. He found out that the automatic control strategies can significantly reduce the consumption of electricity spent on lighting, reaching 87% reduction in environments with windows located in opposite sides of them. The aim of the present study is to describe the Figure 1. Scheme for cases M1, M2, M3 and M4. applicability of a methodology to assess energy efficiency, considering the use of daylight. This study The internal reflectances of the environments were: makes use of an integrated simulation by using two 70% for the ceiling, 50% for the walls and 20% for applications of computer simulation, Daysim and the floor. The models were evaluated according to EnergyPlus, in order to overcome the limitations of the four cardinal orientations: North (0º), East (90º), the latter when calculating daylight. South (180º) and West (270º), with the surrounding METHODOLOGY not being considered. The information in the related literature and research The methodology was based on evaluating and was reviewed in order to construct the typical office comparing the lighting and energy performances of building model in Florianopolis/SC. Thirty-five office building models with different architectural buildings were analyzed on the topic of building variables, by using computer simulation. The characterization, and 41 offices were also analyzed methodological steps are shown as following. regarding occupancy pattern and use of equipment The first step concerned survey data obtained from [Santana, 2006 and Carlo, 2008]. already existent papers, regarding typologies and Regarding the use of equipment and occupancy uses in non-residential buildings in Florianopolis pattern, the most common types of equipment city, SC. These data were used to define the reported in Santana’s research were considered: air predominant typology among the office buildings, as conditioning, coffee makers, computers, fax well as to choose the variables to be studied and the machines, light bulbs, refrigerators, printers, fans, preparation of the models for simulation. water filters and radios. They were monitored and the The second step referred to computer simulations, average heating load of the equipment per unit area which were divided into three types. The first one was 9.7 W / m². was thermal energy simulation using EnergyPlus The air conditioning system in use was a window program to be compared with the integrated unit that operated during the hours of use of the simulation results. The second one was daylight building (8 am to 6 pm) and maintained the internal simulation which used Daysim program to assess the temperature between 18 º and 24 º C throughout the dynamic daylight behavior and obtain the necessary year. This temperature is commonly found in the data (operation of lighting) for the integrated energy literature for papers related to Florianopolis city simulation. The final step was the integrated energy [Carlo, 2008]. The air conditioning system was simulation, which used EnergyPlus program to obtain designed with the label A, according to the top the data referring to the final energy consumption of Efficiency rating of INMETRO (the Brazilian the models. agency for measures), with a COP (Coefficient of Characteristics of the models for the simulations Performance) for cooling of 3.19 W/W, scaled Different office rooms were modeled and simulated. according to the area of the prototype under study. They were represented by surfaces