The Policy Address 2015 has suggested using “Kowloon East as a pilot area to explore the feasibility of developing a Smart City.”1 The Government did not elaborate on the specifics, but generally speaking, a smart city improves efficiency and quality of life with digital technology while optimizing the consumption of resources. One key issue that directly affects the quality of life is the environment. Dr Charles Man-sing Wong, Assistant Professor, Department of Land Surveying and Geo-Informatics, an expert in urban environmental quality, is devoted to investigate Urban Heat Island (UHI) effect in Hong Kong, essential to the thoughtful town planning that makes a smart city.
UHI and human health
An Urban Heat Island refers to a densely populated area with higher temperature than surrounding rural areas due to human activities and urban development. Land surface is modified and covered in materials that absorb heat quickly during the day, but release heat slowly at night, such as asphalt and concrete. The built-up areas thus cannot cool down as quickly as the rural areas, resulting in huge temperature difference.
Besides, the height and density of buildings also affect temperature and air flow. Sky View Factor (SVF) is the fraction of sky visible from the ground up. Open space gives high SVF meaning better release of heat at night. Other factors relevant to UHI are wind direction and speed, vegetation cover, man-made heat sources and air-borne pollutants. According to Dr Wong, UHI has major impacts on the wellbeing of urban dwellers. “In Hong Kong for instance, at the peak of summer, every degree Celsius rise in temperature would result in several more deaths associated with excessive heat exposure. UHI exacerbates heat waves, increases the risks of heat stroke and heat exhaustion, especially among sensitive populations, those with existing health conditions and those working outdoors. That’s why it’s important to reduce UHIs and that could be done in several ways, such as vegetation cover, using building materials with high thermal emittance and better town planning based on data gathered with Remote Sensing technologies and Geographic Information Systems (GIS).”
Frontal Area Index and ventilation corridors
One factor that affects temperature is wind direction and speed. “There have been different ways to model wind ventilation in an urban setting, such as Computational Fluid Dynamics (CFD) model, but it is computer-intensive and inapplicable to the whole city. Now with GIS and Remote Sensing techniques, we can derive ventilation pathways using the Frontal Area Index (FAI) of each building retrieved from GIS data,” said Dr Wong. Simply put, FAI measures how a building blocks off the wind. By mapping out FAI of an area, researchers can deduce the paths of least resistance that the wind would take. “And town planners can make correct decisions when they design the urban environment without blocking the key ventilation corridors. By simply altering the locations of buildings or even the orientation of the buildings, ventilation can be maintained and UHI can be mitigated.”
Dr Wong also led a research team in developing a portable environmental monitoring device that can be connected to a smartphone via Bluetooth. Geo-tagged data can then be uploaded to a server for real-time sharing and visualization. In near future, everyone can contribute to the real-time report of various environment attributes including temperature, humidity, UV, noise and air pollution from anywhere in Hong Kong. It is also a vital step in making the city smart.
[1] HKSAR Government. “Point #50.” 2015 Policy Address, 14 January 2015. Retrieved from http://www.policyaddress.gov.hk/2015/eng/p48.html
