URBAN HEAT ISLAND IN SINGAPORE
In tropical Singapore, increased temperatures due to Urban Heat Island (UHI) negatively affects the thermal comfort of residents. The UHI effect is the result of complex changes in the surface energy budget of urban areas. These changes can broadly categorized as (1) reduced vegetation, (2) properties of urban materials, (3) urban geometry, and (4) anthropogenic heat.
From previous research we have a broad understanding of the magnitude of the UHI effect in Singapore and of its main causes. A study of air temperatures conducted by N.H. Wong (Wong and Chen, 2006) in conjunction with the Building Construction Authority (BCA), the Housing and Development Board (HDB), the National Parks Board (NParks), the Meteorological Services in Singapore (MSS) and the National Environment Agency (NEA between 2001 - 2004 showed that the UHI intensity in Singapore was about 4.5°C. A more recent study from Chow and Roth found that the peak UHI magnitude occurs approximately six hours after sunset at central business districts. Higher UHI intensities generally occur during the southwest monsoon period of May-August, with a maximum of 7°C observed at Orchard Road at approximately 9.00 pm local time (Chow and Roth, 2006). More detailed information about the influence of albedo on the UHI in Singapore has been obtained from satellite or aerial images (Mackey et al., 2012).
Another approach to understanding the UHI in Singapore has been to study local heat flux densities due to anthropogenic activities. Using energy consumption as an indicator, Berger (2012) demonstrated large spatial variation in anthropogenic heat flux across the city and concluded that the contribution of anthropogenic heat sources to the UHI has been underestimated. While gas consumption shows no significant seasonal variation, electricity consumption increases markedly during the warmer months of the year (May - July). This strong seasonal pattern in the electricity consumption reflects the increased use of air conditioning during warmer months. The inference from these results is that Singapore’s UHI effect (which is much larger than the seasonal variation in temperature) is already responsible for a considerable part of domestic electricity consumption.
As Singapore’s energy supply is almost totally carbon-based, decarburization and thus reducing the UHI effect would significantly increase thermal comfort in Singapore. Large contributors to the UHI effect in Singapore are carbon fuel based transportation and industries. Industry and transport contribute with 59% and 21.5%, respectively, to the total energy consumption and households with 5.4% (with a dominant contribution through air conditioning). These warrant a more detailed investigation. Furthermore, due to inefficiencies in the electricity generation, a significant amount of energy is converted into waste heat.