Chun-Ming Hsieh

Mitigating urban heat islands: A method to identify potential wind corridor for cooling and ventilation

Abstract In summer, the urban heat island effect causes unbearable warmth in the cities of Taiwan. This study maps out ventilation paths that are expected to draw in breezes from suburban areas and the sea to mitigate the urban heat island effect. Wind corridors are estimated based on the concept that wind moves along paths of low urban roughness, as defined by the frontal area index (FAI) and the least cost path (LCP) methodology followed in this study. The primary wind corridor was proposed with a main function of identifying wind that minimizes net daytime heating through a redistribution of the total surface heat flux. Land use that affects urban temperature is discussed by indicating the areas of potential rises and drops in air temperature in order to describe the temperature influences in both windward and leeward areas. The horizontal resolution of the calculation unit was a hundred meters, which is called an urban block scale in this study. At that resolution, detailed analyses can be discussed in a detailed plan scheme. A slightly more sophisticated CFD model confirms the more simplistic GIS-based mode, and thus, these results have the potential to guide urban wind corridor planning efforts. The land use map of potential temperature influences is superimposed with the current wind corridors to determine the exact areas in which to execute the mitigation strategies. Four sites are recommended for urban surface improvement according to their land uses, respectively. Furthermore, a potential cooling route on the east side of the study area was suggested for the FAI reduction strategy.

Managing heat rejected from air conditioning systems to save energy and improve the microclimates of residential buildings

Abstract Simulations are conducted to investigate the influence and improvement potential of air conditioning heat rejection management of residential buildings on microclimate and energy use. The microclimate and building energy use are simulated on a typical high-rise building in Taipei, Taiwan, on a summer night. Heat rejection from the air conditioners is estimated with a building energy program, EnergyPlus, and a computational fluid dynamics (CFD) program, Windperfect, is used to analyze how heat rejection affects the outside thermal environment. Results show that heat rejection from air conditioners worsens the thermal environment below the urban canopy, thus increasing building energy use. Three countermeasure cases of heat rejection management, which consider the type of cooling system and its installation position, are proposed in this study. The average air temperature increase around the buildings caused by heat rejection was analyzed by transferring the simulation results of the building energy program to the CFD model on an hourly basis. Results show that the air temperature next to the building envelope and the air temperature around air conditioners decrease and that there is a reduction in electricity consumption by the air conditioners when a split-type air conditioner is installed on each floor or on every third floor. A reduction in the ambient air temperature below the urban canopy can be obtained by placing a cooling tower on the roof of the building.

The Influence of Tree Allocation and Tree Transpiration on the Urban Microclimate: An Analysis of a Subtropical Urban Park

Recently, because of the growing importance of issues such as global warming and the heat island effect, maintenance of trees and the design of planting on green land have become increasingly significant. This article focuses on variation in sap flow in, and transpiration of, Araucaria heterophylla in Tainan Park. In order to understand the relationship between the allocation of plantings and the physiological functions of trees, the influence of cover conditions and meteorological conditions related to insolation were taken into consideration. First, under the same allocating conditions, the amount of transpiration was affected by differences on the ground (grassy and sandy). The differences in cover conditions have a lot to do with the water physiology of the tree. In addition, other factors such as insolation and changes in the speed of sap flow during a day are positively correlated. The results of this study are the main factors for evaluating the allocation and density of tree plantings and also for analysing the relationship between microclimatic environments and the physiological characteristics of trees.

An example of ecological wisdom in historical settlement: The wind environment of Huazhai village in Taiwan

During the initial developmental stage of historical settlement, residents used the principles of feng shui to locate suitable residence sites to ensure quality of life. Using Huazhai Village in Taiwan as a case study, this study explores the design philosophy of ancient Chinese people through scientific analysis. Research showed that the region was characterized by a windy climate. Therefore, a computational fluid dynamics model was used to simulate the local wind environment and restore the early architectural complex of the village. Compared to the current situation, it was demonstrated that the planning principles of the early buildings gave first priority to site selection. Second, with the village streets acting as a wind corridor, the angle of the streets was well utilized to strengthen outdoor ventilation in summer. Third, according to wind field characteristics at different locations, various opening directions and arrangement modes were applied in different areas to improve the wind field of the living environment. This ancient ecological wisdom provides current designers with a new strategy for living in harmony with nature, which may aid the design of sustainable living environments that adapt to the climate.

Using Heritage Risk Maps as an Approach for Estimating the Climate Impact to Cultural Heritage Materials in the Island of Taiwan

Heritage conservation studies concerning how climate influences Asian cultural heritage are rare. The object of this study was to utilize the concept of heritage climatology together with a spatial analysis approach that includes respective climate parameter risks to cultural heritage sites. The study area, the island of Taiwan, is located between the Ryukyu isles in the north and the Philippine archipelagos in the south. It lies across the Tropic of Cancer, and its climate is influenced by the East Asian Monsoon. Northern and central Taiwan has a humid subtropical climate while most of southern Taiwan has a tropical monsoon climate. With nearly 300 hundred years of history, Taiwan displays much cultural diversity, which is the result of racial mingling of indigenous peoples, Spanish, Dutch, Chinese, and Japanese since ancient times, leaving behind rich cultural heritage sites.

Using heritage risk maps as an approach for estimating the climate impact to cultural heritage materials in the Island of Taiwan

This paper presents an automatic methodology capable of registering non-overlapping laser scans based on a bundle block adjustment for the orientation estimation of synthetic images generated from the 3D data and camera images using a Structure-from-Motion (SfM) method. Adding camera images to the registration of the generated images can improve the block geometry. The SfM process provides accurate image orientations and sparse point clouds, initially in an arbitrary model space. This enables an implicit determination of the 3D-to-3D correspondences between the sparse points and the laser data then, the Helmert transformation is introduced and its parameters are computed. This results in registering the non-overlapping scans, since the relative orientations between the generated images are determined at the SfM step and transformed to the absolute coordinate system directly. The proposed approach was tested on real case studies and experimental results are shown to demonstrate the effectiveness of the presented method.