Cooling rates and energy demand potentials of urban heat island in Akure, Nigeria

This study was carried out to examine air temperature cooling rates and energy demand potentials of the Urban Heat Island (UHI) in Akure, a medium sized hot- humid tropical city in Nigeria. Investigations were conducted on the air temperature data obtained from a year-long (January to December 2010) simultaneous experiment of fixed point observations at the urban city centre and a rural reference site. The UHI which usually causes significant thermal alteration has been established from the climatological analysis of the differences in hourly air temperature between the two sites, using the most common UHI intensity index. The air temperature cooling rates and some energy demand parameters (cooling days and cooling degree hours) were also calculated and compared. Results showed that urban effect significantly reduced air temperature cooling rates over time, causing the rural site to cool relatively faster than the urban site. The energy demand parameters showed that high temperatures during the hot dry period at the onset of summer monsoon will enhance cooling energy demand in the city, thereby increasing loads on the electricity grid. At such time, the high UHI intensities will accelerate cooling load and enhance number of discomfort days with longer length of hours that requires cooling for comfort. However during the wet season, there is drastic reduction in the cooling energy demand due to the dominance of cloudy conditions during the daytime and cooling effect of the monsoon winds that are prevalent in the season, as well as pronounced decline in the nocturnal UHI intensities. Key words: cooling rates, energy demand parameters, urban, rural.