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Various problems often arise in high-rise buildings during the winter months due to the stack effect. In this study, the high-rise building of interest, located in South Korea, was experiencing constant loud noises in the winter due to the stack effect. Thus, we created a noise level reduction plan by creating a method for pressurizing the high-rise zones of the building according to outdoor conditions. To discover the appropriate pressurization operating modes, we applied a two-year commissioning process to the 50-story building of interest. The 1st- and 47th-floor elevator halls were identified to have the highest noise levels of all other floors. Prior to applying the reduction plan, the maximum noise level on the first floor with the HVAC system turned off was 85 dB(A) and with the HVAC system turned on it was 70 dB(A). Both values exceeded the criteria of 57 dB(A) for a lobby space of a commercial building. In the case of the 47th floor, the maximum noise level with the HVAC system turned off was 58.7 dB(A) and with the HVAC system turned off was 56.0 dB(A), despite the latter having increased airtightness performance and applying preliminary pressurization (i.e., HVAC operation mode 2). These values exceeded the criteria of 48 dB(A) for an elevator hall in a commercial building. Following this initial data, we determined to pressurize the high/mid-rise zones of the building according to the outdoor air temperature and wind velocity conditions, which we categorized into four types (i.e., HVAC operation mode 4). To this effect, the first-floor elevator hall’s maximum noise level was 56.6 dB(A), meeting the criteria, and the 47th-floor elevator hall’s maximum noise level was 49.5 dB(A), still exceeding the criteria but by an insignificant amount. Although the HVAC pressurization operation we utilized resulted in favorable results for the target building A, it may not be as effective in other new high-rise buildings, creating changes to the indoor air environment or to the energy costs in maintaining a building. However, for the purposes of resolving the stack effect, we believe that the commissioning process we took to optimize the HVAC operation that is presented here can be applied to other new and existing high-rise commercial buildings.

Heated glass can be applied to improve windows’ condensation resistance and indoor thermal comfort in buildings. Although this applied technology has advantages, there are still some concerns in practical applications, such as additional energy consumption and control issues. This study evaluates the effectiveness of a heated window heating (HWH) system in terms of thermal comfort and heating energy performance (HEP). The simulation-based analysis is performed to evaluate the effectiveness of the HWH using a residential building model and to compare it with radiant floor heating (RFH) and hybrid heating (HH) systems (i.e., combined HWH and RFH). This study also investigates the peak and cumulative heating loads using HWH systems with various scenarios of control methods and setpoint temperature. The predicted mean vote (PMV) is used as an indoor thermal comfort index. The ratio of cumulative thermal comfort time to the entire heating period is calculated. The results show that HWH and HH can reduce the heating load by up to 65.60% and 50.95%, respectively, compared to RFH. In addition, the times of thermal comfort can be increased by 12.55% and 6.98% with HWH and HH, respectively. However, considering the social practices of South Korea, HH is more suitable than HWH. Further investigations for HH show that a surface setpoint of 26 °C is proper, considering both heating demands and thermal comfort. In addition, the setpoint temperature should be determined considering HEP and the thermal comfort for HWH, and the optimal setpoint temperature was suggested under specific conditions.

Abstract >> Biogas is a renewable fuel from anaerobic digestion of organic matters such as sewage sludge, manureand food waste. Raw biogas consists mainly of methane, carbon dioxide, hydrogen sulfide, and water. Biogas mayalso contain other impurities such as siloxanes, halogenated hydrocarbons, aromatic hydrocarbons. Efficient powertechnologies such as fuel cell demand ultra-low concentration of containments in the biogas feed, imposing stringentrequirements on fuel purification technology. Biogas is upgraded from pressure swing adsorption after biogas purification process which consists of water, H 2 S and siloxane removal. A polymer electrolyte membrane fuel cellpower plant is designed to operate on reformate produced from upgraded biogas by steam reformer. Key words :혐기성 소화가스(Anaerobic digestion gas), 정제(Purification), 고질화(Upgrading), 메탄개질(MethaneReformimg), 연료전지(Fuel Cell) † Corresponding author : bioleegas@naver.com Received: 2016.3.17 in revised form: 2016.4.12 Accepted: 2016.4.30Copyright ⓒ 2016 KHNES

This paper investigates operational benefits of integrating thyristor controlled series capacitor (TCSC) in Korean electric power system. Critical challenges of balancing the electricity demand rise and deferred transmission construction due to the public opposition and environmental impact as well as unique topological issues of the power grid, endanger reliability of the system. Installation of flexible ac transmission systems (FACTS) is envisioned to be a low-environmental impact technology that effectively resolve these issues. In particular, this research exploits flow control capability of TCSC and examines the benefits of improving transmission capability and security. It presents a series of studies for identifying the adequate location and size of the TCSC and discusses practical issues and lessons learned through studies.

Abstract Supercritical carbon dioxide (S-CO2) power cycle has been under the spotlight for years as one of the promising solutions to resolve the energy and environmental problem. The most of previous studies focused on cycle performances and applicable configuration. In this study, detailed and extensive analysis on the recompression S-CO2 power cycle was carried out to reflect more practical and desirable conditions. This study focused on the optimization of the S-CO2 cycle by evaluation of the irreversibility of the recuperators using the effectiveness analysis and pinch point temperature difference (PPTD) analysis. Split ratio from the main stream to the recompressor and compression ratio were considered as independent parameters. From the simulation, the characteristics and performance of the recompression cycle were discussed. The optimum operating conditions were determined in combinations of PPTDs of the two recuperators. With the performance curves, control strategy of the two independent parameters is ranged for desirable operation of S-CO2 power cycle.

Public transportation can have an efficient role ingainingtraveler satisfaction while decreasing operation costs through establishing an integrated public transit system. The main objective of this research is to propose an integrated multimodal transit model to design the best combination of both railway and feeder bus mode transit systems, while minimizing total cost. In this paper, we have proposed a strategy for designing transit networks that provide multimodal services at each stop, and for consecutively assigning optimum demand to the different feeder modes. Optimum transit networks have been achieved using single and multi-objective approaches via metaheuristic optimization algorithms, such as simulated annealing, genetic algorithms, and the Non-dominated Sorting Genetic Algorithm II (NSGA-II). The used input data and study area were based on the real transit network of Petaling Jaya, located in Kuala Lumpur, Malaysia. Numerical results of the presented model, containing the statistical results, the optimum demand ratio, optimal solution, convergence rate, and comparisons among best solutions have been discussed in detail.