• Energy Research

Abstract The solar photovoltaic (PV) system is known as one of the most outstanding new renewable energy systems for achieving the nearly zero energy building (nZEB). For the continuous deployment of the solar PV system in urban environments, it is crucial to estimate the rooftop solar PV potential. Urban areas, however, where high-rise buildings abound, are not always suitable for solar PV installation. Therefore, it is important to accurately estimate the available rooftop area considering the shadows from the surrounding buildings for reliable rooftop solar PV potential estimation. Therefore, this study proposed a method for estimating the rooftop solar PV potential by analyzing the available rooftop area through Hillshade analysis. Toward this end, the rooftop solar PV potential was estimated through the following hierarchical process: (i) calculation of the physical potential; (ii) calculation of the geographic potential; and (iii) calculation of the technical potential. For accurate estimation of the rooftop solar PV potential, the geographic potential (i.e., the available rooftop area) was explored in detail by analyzing the shadow based on the location of the sun through Hillshade analysis. By applying the proposed method to the Gangnam district in Seoul, South Korea, this study estimated the physical, geographic, and technical potentials on hourly, monthly, and annual bases. Overall, the physical, geographic, and technical potentials in the Gangnam district were found to be 9,287,982 MW h, 4,964,118 m 2 , and 1,130,371 MW h, respectively. These rooftop solar PV potential results can be used in establishing solar policies by analyzing the different levels of the rooftop solar PV potential on hourly, monthly, and annual bases.

As climate change and global warming have become two of the most significant environmental issues today, the double-skin façade (DSF) is getting considerable attention as an energy-efficient passive design. This study is aimed at assessing the seasonal energy efficiency strategies of a DSF targeting library facilities in the climate region with hot summers and cold winters. Toward this end, this study was conducted in four steps: (i) establishment of seasonal energy-efficient strategies; (ii) application of seasonal energy-efficient strategies; (iii) analysis of energy saving effect by season; and (iv) life cycle cost and life cycle CO2 analyses for selecting an optimal DSF. Results show that a shaft box DSF energy model (EMS) #2, which applied winter strategies, was optimal with an energy saving rate of 4.13%, while a multi-story DSF energy model (EMM) #5, which applied summer strategies, was optimal with an energy saving rate of 12.67%. In terms of savings to investment ratio (SIR40) and breakeven point (BEP40), the multi-story DSF (3.20; 9 years) was superior. The results of this study can be used for (i) seasonal energy efficiency strategies of a DSF in East Asian monsoon climates, and (ii) as a guideline for the application of a DSF both in existing and new buildings.

The excessive use of fossil fuels has led to global warming and air pollution. To solve these problems, interest in new renewable energy system (NRE system) has increased in recent years. In particular, photovoltaic, solar thermal heating, fuel cell and ground source heating system are actively implemented for achieving the zero energy building. Since the initial investment cost of the NRE system is quite expensive, it is necessary to conduct a feasibility study from the life cycle perspective. Therefore, this study aimed to develop the process for the implementation of NRE system in a building for the optimal design. This study was conducted with four steps: (i) establishing the basic information for the system installation; (ii) selecting key factors affecting system performances; (iii) making possible alternatives of the system installation; and (iv) selecting optimal system by considering environmental and economic effect. The proposed process could enable the final decision-maker to easily and accurately determine the optimal design of the NRE systems from the economic and environmental efficiency in the early design phase. The process could also be applied to any other NRE system and could be extended to any other country in the global environment.

Abstract To ensure the high energy performance of a new building, its operational rating should be accurately estimated in the early design phase. Toward this end, this study developed an estimation methodology for the dynamic operational rating (DOR) of a new residential building using the advanced case-based reasoning (A-CBR) and stochastic approaches. This study was conducted in three steps: (i) establishment of a case database; (ii) retrieval of similar cases using the A-CBR approach; and (iii) estimation of the dynamic operational rating using the stochastic approach. The residential buildings located in Pusan, South Korea, were selected to validate the applicability of the developed methodology. Also, this study used the mean absolute percentage error (MAPE) to evaluate the prediction accuracy of the developed methodology (which means the difference between the predicted and measured energy performance). As a result, it was determined that the MAPE of the A-CBR model (i.e., 96.8% for electricity and 86.6% for gas energy) is superior to those of the other models (i.e., the basic CBR, multiple regression analysis, and artificial neural network models). In addition, based on the stochastic approach, it was estimated that cluster No.6, as a case study, would have the letter rating of ‘B’ grade (i.e., 25

Abstract Psychological response based on the indoor environmental quality (IEQ) condition changes and activities of the occupants, can be assessed via indoor air quality (IAQ) satisfaction and thermal comfort. However, it is difficult to analyze both indices at the same time because they are measured on different scales. Therefore, this study aimed to develop an integrated psychological response score of the occupants based on 22 experimental participants' activities and the IEQ condition changes by using the weighted Euclidean distance. For this purpose, the experiment was designed with three scenarios to simulate the IEQ condition changes (i.e., CO 2 concentration and operative temperature) during an 8-h working period. In each scenario, six cognitive tasks that simulate office work were performed to consider the activities of the occupants. A questionnaire survey on IAQ satisfaction and thermal comfort was conducted before and after (i) office work and (ii) IEQ condition changes. As a result, when the operative temperature was changed from 18.70 °C (cold) to 25 °C (neutral), the best psychological response score was calculated as 0.335. In addition, the occupants were more affected by the operative temperature than the CO 2 concentration. It was shown that the mental health status based on IEQ condition, while considering both the indoor air pollutant and indoor climate, could be expressed as a single index. The mechanical system designer and facility manager can design or operate the IEQ condition considering the integrated psychological response score of the occupants, which can be used as an IEQ condition management guideline for mental health.

Green-roof systems offer various benefits to man and nature, such as establishing ecological environments, improving landscape and air quality, and offering pleasant living environments. This study aimed to develop an optimal-scenario selection model that considers both the economic and the environmental effect in applying GRSs to educational facilities. The following process was carried out: (i) 15 GRSs scenarios were established by combining three soil and five plant types and (ii) the results of the life cycle CO(2) analyses with the GRSs scenarios were converted to an economic value using certified emission reductions (CERs) carbon credits. Life cycle cost (LCC) analyses were performed based on these results. The results showed that when considering only the currently realized economic value, the conventional roof system is superior to the GRSs. However, the LCC analysis that included the environmental value, revealed that compared to the conventional roof system, the following six GRSs scenarios are superior (cost reduction; reduction ratio; in descending order): scenarios 13 ($195,229; 11.0%), 3 ($188,178; 10.6%), 8 ($181,558; 10.3%), 12 ($130,464; 7.4%), 2 ($124,566; 7.0%), and 7 ($113,931; 6.4%). Although the effect is relatively small in terms of cost reduction, environmental value attributes cannot be ignored in terms of the reduction ratio.

Abstract To facilitate an increase in comfortable and healthy indoor environments, a lot of people have researched and conducted studies related to this field. However, it has proven difficult to find optimal indoor conditions because each of the elements that make up the thermal environment has different properties. Natural ventilation is an important factor in meeting and creating the thermal environment as well as improved indoor air quality. Moreover, the continuation of efforts to reduce energy consumption in buildings is also required from the design stage due to the depletion of energy resource and global warming. Therefore, this study aims to provide a material of natural ventilation for educational facilities by calculating the energy consumption of a classroom in accordance with indoor temperature distributions in summer. A target educational facility with classrooms was selected in Seoul, Republic of Korea. This study assumed that the classroom windows were fully opened and were then analyzed for indoor temperature distributions and energy consumption according to natural ventilation. In addition, the simulation was conducted based on the actual daily schedule in the school. The results were achieved by utilizing the Computer fluid dynamics simulation and Building energy simulation. This paper will be the basis of research related to occupant behavior and patterns indoors.