Browsing by Author "Shabbir Ahmed, Dr. Khandaker"

Now showing 1 - 2 of 2

Study on the solar energy harvesting potential at urban block level for business districts in Dhaka
(Department of Architecture, BUET, 2021-06-01) Sabbir Ahmed; Shabbir Ahmed, Dr. Khandaker
On-site production of electricity from solar energy using increasingly sophisticated technologies such as photovoltaics (PV) has been recognized as crucial for making cities energy-efficient. Urban configurations, which can be defined by urban design parameters that are governed by building regulations in Dhaka, highly influence the solar energy harvesting potential (or solar potential) of urban areas. This research aims to find out how the combined effect of urban parameters regulates the solar potential of urban blocks in the business districts of Dhaka, and explores the possibilities for the development of urban design strategies from such findings. Methods include an extensive theoretical framework, field investigation, parametric simulation study, and statistical analysis. For simulation, an integrated parametric interface combining Rhinoceros, Grasshopper, and Ladybug Tools was used. Field investigation generated insights about energy consumption in the buildings in an existing business district (Motijheel Commercial Area) in Dhaka, which is largely regulated by the combined effect of weather variables, and shows strong individual correlations with temperature variables. Moreover, airconditioning energy was found to dominate energy consumption in buildings. As such, solar energy can contribute to meeting energy demands in commercial office buildings more efficiently during the cooler and drier months of the year. Monthly Mean Temperature, Monthly Maximum Temperature (extreme variable), Monthly Average Sunshine Hours, Monthly Number of Workdays and Eid-ul-fitr Month (categorical variable) were all found statistically significant predictor variables for generating monthly energy consumption figures. Parametric study and analytics revealed that while the density and the compactness ratio of an urban block had negative and positive impacts respectively on its solar potential per unit floor area, the impact is governed by the combined effect of parameters such as the number of stories, ground coverage, street-to-surface distance, side-to-side distance, and orientation. Facades facing unobstructed south were found to increase solar potential more efficiently than facades facing other directions and with poorer setback conditions. Local building regulations should acknowledge compactness ratio and surface orientation as significant strategies for more efficient solar energy harvesting in the business districts in Dhaka. Urban designers, planners, architects, and engineers will be critically informed by this research about the impact of urban design decisions on the solar potential of urban blocks within the climatic and physical context of Dhaka.
Urban adaptation measures for climate change: study of urban wetlands in view of potential urban cooling
(Department of Architecture , BUET, 2018-02-26) Abu Taib Mohammed Shahjahan; Shabbir Ahmed, Dr. Khandaker
Urbanization in the developing world took place at an unprecedented rate which outpaced that of the developed world except for few exceptions. Much of the urban areas of the developing world are in the tropical zone, which has gone through an inadvertent environmental modification due to increased built density. This environmental modification due to high built density resulted in an adverse thermal environment in the urban area which is further exacerbated by global warming due to climate change. This adverse thermal environment in the city resulted in a muchreported phenomenon known as Urban Heat Island. An adaptation measure against Urban Heat Island in the tropical cities of the developing world can be use of the natural cycle to cool down the overheated urban fabric. Dhaka is one of the most densely populated cities in the world, where the juxtaposition of wetlands and built up area coupled together may have an opportunity for creating a viable and distinct character of its own while addressing the challenges of inadvertent environmental modification. Increased built density and reduction of wetlands are making Dhaka’s climate uncomfortable in comparison to its rural surroundings, resulting increasing number of air-conditioned buildings, which in turn elevate urban air temperature and consequent energy demand. Thus, urban land use in Dhaka is directly contributing to Urban Heat Island effect. Coolth produced by urban wetland can be an adaptive measure against urban heat island in Dhaka. This study approaches the problem by identifying wetland as existing and potential cool spot and analyzing their characteristics for cooling efficiency. Remote sensing technique was used to identify the existing and potential cool spot at surface level for analysis. This technique applied to analyze the morphology of the wetland as a producer of coolth with potential to counterbalance for the urban heat. As a part of the study field campaigns were conducted and environmental variables were recorded on the buffer area of selected wetlands indicated in the remote sensing study. Evaluations were undertaken with respect to the design factors such as the orientation of the wetlands, riparian shading characteristics, urban permeability for the cooling effect, as those factors affect the cooling intensity produced by the wetland. Through simulation studies, some aspects are identified which could not be derived from the fieldwork. They are the effect of differential riparian shading on the wetlands, effects of variable temperature and relative humidity on the coolth produced by the wetland. Based on the simulations some urban design recommendations was derived. The research finding that indicated the relationship between some important factors like the interdependency between fetch and inversion height to control inversion layer over the water surface that regulate the urban cooling effect of the wetland at an urban scale. This relationship informs as to what extent urban wetland design might impact the thermal environment leading to possible urban microclimatic cooling. These findings, in turn, might help in the development of certain policy guidelines for the urban designers and planners to more positively impact the urban thermal environment.