Seung Bok Leigh

Energy consumption analysis of a residential building with phase change materials under various cooling and heating conditions

Phase change materials (PCMs) absorb or release a large amount of heat when changing phase from solid to liquid or vice versa. When this characteristic of PCM is utilized, it can be employed effectively for energy conversation in buildings. To apply PCM to buildings, the thermal characteristics of PCM must be considered, such as the melting temperature and temperature range of the phase changes. In addition, the characteristics of the heating and cooling system, which influence the cycle of PCM absorbing and releasing heat, should also be taken into account. The purpose of this study was to provide guidelines for a method to apply PCM suitable for Korean residences, which use packaged air conditioners and floor radiant heating systems for cooling and heating, respectively. To accomplish this, the characteristics of cooling and heating energy reduction were analysed according to the application of PCM through simulation, taking into consideration various heating and cooling operating conditions. In addition, thermal conditions for PCM suitable for summer and winter were analysed through case studies, with the melting temperature and temperature range of phase changes as variables.

Window retrofit strategy for energy saving in existing residences with different thermal characteristics and window sizes

An adequate window system is one of the most important retrofit strategies for effective energy conservation of a building, because the U-value and solar heat gain coefficient of windows have enormous impact on the heating and cooling loads of buildings. Therefore, this paper presents methods for improving the energy efficiency of existing residences that have various window sizes and envelope insulations, through a window retrofit using optimal U-value and solar heat gain coefficient values. Furthermore, the window retrofit strategy has been standardized using analysis of the correlation between the properties of the retrofitted window and energy saving rates. The results show that the annual heating and cooling energy demand decreases by 7.9–16.7% when changing the U-value of the windows in a poorly insulated house, and that the relationship between the lower U-value and energy saving is strong for poorly insulated houses regardless of window size. However, for houses with better insulation and larger window sizes, the total energy usage decreases by 18.4–29.7% when the solar heat gain coefficient is lower, and the energy saving effect of the U-value decreases while that of the solar heat gain coefficient increases. Practical application: This study was focused on improving the energy efficiency of existing residences by applying retrofitting technology. By exploration of the contribution of the specific qualities of windows and the thermal envelope (insulation) system of buildings via simulation, it was determined that it is necessary to adjust the U-value and SHGC of retrofitted windows, in relation to the thermal performance and window-wall ratio of an existing residence, to achieve high energy efficiency.

A Study on External Shading Devices for Reducing Cooling Loads and Improving Daylighting in Office Buildings

Abstrct This study is aimed at analyzing the impact of effective shading design for office buildings. For shade design, the overheated period for the area in which a target building was located was estimated, the building was configured to be shaded during this period, and a different shading design was applied for each direction. Using this shade design, the daylighting performance and the reduction in cooling loads during the overheated period were evaluated. The daylighting performance was evaluated by employing the daylight factor and useful daylight illuminance (UDI). The results showed a 35% reduction in cooling loads due to the shading device. Regarding the daylight factor, more points were included in a proper daylight factor of 2–5%, which was shown to increase the UDI to 500–2,000 lux.

A Study on Cooling Energy Savings Potential in High-Rise Residential Complex Using Cross Ventilated Double Skin Facade

Abstract The housing market in Korea is changing rapidly. As multi-functional high-rise residential complexes become popular, occupants need more comfortable indoor environment as well as more usable spaces than ever before. These trends force to increase the energy usage for environmental controls, especially for cooling. Thus, this study aims at reducing the cooling energy requirements of high-rise residential complex by maximizing the possibilities of natural ventilation strategies through cross ventilated Double Skin Façade. Based on ESP-r simulations, it was confirmed that the Double Skin Façade could reduce up to 30~40% of cooling energy compared to the conventional façade designs.

Development and Application of the KLT Method for the Energy Performance Evaluation of Non-residential Buildings in the Early Design Stage

Abstrct There is a growing interest in sustainable design in the building industry to reduce energy consumption and minimize adverse environmental impacts of buildings. The strategies for sustainable design are as follows: 1) reducing the size of the building′s equipment system and saving energy through an optimal design; 2) maximizing natural energy use through a passive solar heating system; and 3) utilizing an active system through applications of high-performance heating, ventilation, and air conditioning (HVAC) and lighting systems, installation of new and renewable energy facilities, and so on. It is vital to evaluate and compare the energy efficiencies of design alternatives at an early design stage, and hence, to improve the energy performance of the final building, as design elements determined at an early phase in the architectural design process greatly influence the energy performance of the building itself. Further, costs increase over time with the number of design changes made. In the course of this research, the KLT (Korean lighting and thermal energy) method was revised and developed based on the lighting and thermal energy (LT) method, adjusting for South Korea′s climate and architectural regulations, which can be used to assess the energy performance of buildings. This study was conducted to determine the process of selecting optimal design alternatives to maximize building energy performance at an early stage in the process.

Cooling energy reduction effect of parallel double-window system operation in residential buildings in South Korea

This paper aims to derive the operational modes of a parallel double-window system that reduces cooling energy consumption and satisfies indoor comfort through natural ventilation. The parallel double-window system examined in this paper is a window system that could control indoor draft distribution and adjust the size of the opening depending on indoor and outdoor conditions. The system can be used in five ways (all close, out-openu2009+u2009in close, out-open+in open (tilt), out-open+in open (turn) and all open). This work verified the energy savings and indoor comfort of the existing mode experimentally, which were originally derived based on simple calculations at the time when the parallel double-window system was developed. A new operation mode, Alt 1, was derived, which addressed problems of the existing mode. In addition, in this work, the operation mode Alt 2 was derived, which simplified Alt 1 so that the actual occupant can use the system easily. By measuring these three operation modes and comparing the results with those of energy plus simulations, the work derived the amount of cooling energy savings and the level of indoor comfort through the use of an appropriate operation mode during inter-seasonal periods. Compared to when the natural ventilation operation mode was not used, cooling energy consumption was reduced by 60% when the operation mode was in use. The cooling temperature set point could have a significant impact on cooling energy consumption.

The effects of ground cover and shading on an outdoor thermal environment in an apartment complex

A comfortable outdoor environment can be achieved through well-designed physical planning, which includes the layouts of buildings, covering materials, grass, trees, water areas, etc. In this study, the outdoor environments of an apartment complex were measured quantitatively. The paving, grass and water areas were chosen to analyse the effects of ground cover on the outdoor environment. An unsteady-state computational fluid dynamics (CFD) simulation was also conducted with the same conditions as the measurement. In order to obtain the reliability and limitation of the simulation, the results of the measurement and the simulation were compared. The effects of changing the green area, including the grass and the trees, to 15% and 50% were analysed by the simulation method. Depending on the ground cover, the air temperature slightly changed. However, the mean radiant temperature (MRT) of the grass area was lower than that of other areas. Especially the shaded area showed a very low MRT and thus thermal comf...

Design and Performance Estimation of Low Energy House Models of Greenhomeplus

Each country is giving number one priority to reduction of building energy consumption to reduce national CO2 emissions. Korea has begun to regulate new buildings energy performance since 2009, targeting zero energy in 2025. To achieve this goal, the government set goals for each stage, but there has been any concrete model suggested. Thus, this study is to suggest a concrete, feasible residential building model through planning, construction, and performance test of low-energy experimental housing having four stages of 40%, 60%, 80%, and 100% energy consumption reduction compared to existing housing. This study selected apartments suitable for the situation in Korea by reviewing domestic and overseas experimental housings, and predicted performance standards, planning of technology application, and according energy performance for four experimental houses. As a result of progressively improving the performance of building envelopes and ventilation and applying high-efficiency system, 100% reduction mode...