Analytical Study of the Effect of Urban Heat Island on Building Cooling Loads in Port Harcourt Metropolis

The urban heat island effect in Port Harcourt metropolis, South South Nigeria, raises urban ambient temperatures above peri-urban and rural equivalents, increasing building cooling energy loads and occupant thermal discomfort, yet this impact has not been analytically quantified for Port Harcourt conditions. This study analytically quantified the impact of the urban heat island on building cooling loads in Port Harcourt using a combination of urban temperature data collection, remote sensing surface temperature analysis, and building energy simulation. Urban-rural temperature differentials were measured at 12 monitoring stations distributed across urban, peri-urban, and rural locations in Port Harcourt metropolis and its surroundings over a continuous 12-month period. Satellite-derived land surface temperature data from Landsat 8 OLI/TIRS (2022 to 2023) were used to map the spatial extent of the urban heat island. EnergyPlus simulations of three building archetypes were conducted using measured urban and rural climate data to quantify cooling load differentials. Results showed that the mean summer nighttime urban heat island intensity in Port Harcourt was 4.3 degrees Celsius, among the highest recorded for a West African city. Annual cooling energy demand in buildings located in high-intensity urban heat island zones was 19 to 27% higher than equivalent buildings in peri-urban locations. Increased tree canopy cover and high-albedo roofing materials were simulated as the most effective mitigation strategies, reducing cooling load by 11 and 9% respectively. The study recommends urban greening and cool roof policies in the Port Harcourt Masterplan revision.

Keywords: urban heat island, building cooling loads, Port Harcourt, EnergyPlus, urban greening