An-Seop Choi

Development of a daylight responsive dimming system and preliminary evaluation of system performance

Abstract In order to make a daylight responsive dimming system itself more flexible and reliable in both control method and system operation, a new system controlled by a computer software program has been developed. The light output from the dimmed luminaires is determined by the selected control algorithm, or is manually controlled in the computer software program. In this paper, the components of such a system are described, and the quantitative aspect of system performance has been evaluated. The results show accuracy and reliability on system performance. The workplane illuminance is maintained relatively close to the target level, and 30–70% of total lighting energy can be saved accordingly.

Improvement in demand-controlled ventilation simulation on multi-purposed facilities under an occupant based ventilation standard

The objective of this paper was to find an effective way of improving demand-controlled ventilation (DCV) simulation performed under an occupant based ventilation standard established in many countries. Two attractive DCV approaches, CO2–DCV and RFID–DCV, were applied to DCV simulations for a theoretical public assembly space served by a dedicated outdoor air system (DOAS) with an enthalpy recovery device. A numerical model for predicting the real-time occupant number, required ventilation amount, CO2 and formaldehyde (HCHO) concentrations under given conditions was developed using a commercial equation solver program. The current ventilation standard used in Korea was applied as a case of occupant based ventilation standards. It was found that the current standard might cause unstable DCV simulation results, especially under CO2–DCV. This is because the ventilation rate (per person) indicated in the standard is the sum of the outdoor air required to remove or dilute air contaminants generated by both occupants and the buildings themselves, and not a pure function of occupant numbers. Finally, it makes DCV control unstable when ventilation flow is regulated only by the number of occupants. In order to solve this problem, the current occupant based ventilation standard was modified as a form of ASHRAE Standard 62.1-2007 showing good applicability to various DCV approaches. It was found that this modification enhances applicability of the current ventilation standard to CO2–DCV significantly and can maintain acceptable HCHO concentrations during the entire time of operation. Fan energy reduction can also be expected from DCV operations.

A Study of Luminous Environment for Standard Illuminance in Residential Areas

Light is an important environmental element for people to live and do creative activities in residential areas. Especially, people are used to live under artificial light in artificial interior surroundings for the most times. Currently, the lighting quality of residential areas has been improved, but it still does not reach to the recommended level because the luminous environment of present residential areas is only based on the life behavior which puts its priority to clear vision. Therefore, it is necessary that proper standard illumination must be used for various uses and purposes. From this point of view, this paper investigated the essence of light in residential areas, and the luminous environment for apartments was measured This paper finally established well-coordinated standard illuminance, derived from the measurement and analysis of luminous environment from these cases.

Practical applications of form factor computation in lighting calculations

Abstract The efficiency of computational methods of form factors is one of the main concerns in lighting calculations. Several computational techniques have been developed in the past to improve the efficiency, but for practical applications of form factor computation in lighting calculations, numeric solutions of the double area integral for general perpendicular and parallel rectangle surface cases have been developed and are widely used. The main advantage of form factor computation in lighting calculations is the ability to perform accurate and fast calculations of luminous quantities in architectural spaces. In this paper, the historical development of the form factor computations and a practical application of DiLauras recently developed form factor computation are introduced, with an analysis of the accuracy of such an application. A computer simulation code is introduced to compute any form factor values for arbitrary surface orientations. A systematic analysis of how the results of a contour integration solution differ from those of existing numeric solutions was also undertaken. Various situations between sending and receiving surfaces were considered, including the facing, size, and distance of two surfaces. In addition, the validation of this developed code was carried out with the principles of the form factor.

A Study on the Subjective Evaluation of Color Appearance under the Different LED CCT Conditions

LED lighting may cause different sensation and color appearance due to the different spectral power distributions compared to those of conventional lightings. Particularly, the CCT (Correlated Color Temperature) of LED lighting has a major effect on color appearance so that this study conducted an experiment through a subjective evaluation and luminance measurement for effective color appearance in a space. This study performed a subjective evaluation under the seven different LED CCT conditions, and color appearance was evaluated with major five colors in a customized lighting box. In addition, luminance measurement was conducted for each CCT and color condition to compare the results from a subjective evaluation. The results of this study may help to select a proper LED CCT for specific color conditions.

A Study on the Comparison of the PV Module Generation from Daylight Irradiation and Indoor Lighting Savings with Lighting Simulation

Recently, BIPV system which is good enough for maintenance and functions with the shading system is being used. However BIPV system with the shading system is different from existing PV module because of using flexible PV module. Prior to the application of the BIPV system, the clearness index was calculated by Erbs et al.(1982) and analyzed for the amount of electric power generation of sky irradiance with measured data. To predict electric lighting energy savings in daylit space, electric lighting power savings with amount of PV module electric power generation was compared by using Relux 2010 software in this study.

Quantitative assessment methods for determining luminous environmental zones in Korea

International organizations have proposed laws, regulations and standards to control light pollution. Korea enacted the Light Pollution Prevention Act on 2 February 2013. This Act designates ‘the luminous environmental zone’ through ‘the luminous environmental impact assessment’ and restricts light emission in the designated area according to the related light emission standards. This paper proposes a quantitative assessment methodology for the luminous environmental impact assessment. For decorative and advertisement lighting, a method using minimum field measurement is suggested. For street lighting, the total emitted luminous flux density is calculated based on security lighting data. Based on such data, a determination is made as to whether a luminous environmental zone for a particular area should be designated or not.

Overall Heat Transfer Coefficient of a Korean Traditional Building Envelope Estimated Through Heat Flux Measurement

Abstract The objective of this research is to determine overall heat transfer coefficients (U-value) of the exterior walls, floors, and roof of a Korean traditional residence via field measurement of transient heat flow and temperature difference across each envelope. The acquired U-values are compared with other existing values and those for current residential buildings. As for the field measurement, heat flux sensors and T-type thermocouple are attached on the internal and the external surfaces of each building component. Real-time measurement data are logged for three consecutive summer days. Acquired U-values agree well with other existing values for traditional building envelopes found in the open literature, but they are higher than U-values of current buildings. From this result one may conclude that the Korean traditional building has uncompetitive thermal performance compared with todays buildings. However, the energy simulation performed in this research shows that the traditional building can provide moderate cooling load competitive to current buildings. It comes mainly from the inherent characteristic of the traditional residence including relatively high infiltration rate and reduced solar radiation penetrating the windows.

Analysis of Luminous Quantity Changes by the Dimming Control of the LED Lamp

Until now, dimmable fluorescent luminaires has been widely used for dimming systems, and LED is currently attracting attentions as a alternative lamp due to environmental problem issues. LED, one of eco-friendly high efficiency lamp, has advantage that dimming is easy than fluorescent luminaire. But there have been not enough research on technical development and application for LED dimming. Therefore, to analyze luminous quantity of dimmable LED, the illuminance, color temperature, luminance, and current were measured in the whole range of dimming. In the results of this study, the dimmable LED of various types showed a similar trend in the changed luminous quantity by dimming.

A Study on the Characteristics of Daylight Distributions by Different Sky Conditions and Controlled Roller Shade Heights

Daylight responsive dimming systems are one of lighting control systems which are to control artificial lightings using available daylight for energy savings. This system is not popular because useful daylight is usually blocked by uncontrolled passive shading systems in buildings. It is necessary to integrate daylight responsive dimming systems and automata! roller shading systems. In this research, mock-up test is performed to analyze the daylight distributions in three different rooms for integrated systems. Roller shades are installed in two rooms. One is fully downed and the other is controlled by sun profile angle. The other room has no shading system as a reference room.