Simulation of the effects of urban greening on urban thermal environment mitigation and air conditioning reduction

In this study, we quantified the impact of urban greening on mitigating the heat island effect and reducing residential cooling energy consumption in Nagano City, Japan. First, we simulated the urban climate using a mesoscale meteorological model. In this study, we obtained the hourly temperature distribution under typical weather conditions in July as a representative example of summer. Next, we set up scenarios for the green coverage rate and performed meteorological simulations for each scenario. In the greening scenarios, the green coverage rate of the building site and the traffic site was set at two levels: 50% and 100%. For comparison, the green coverage rate was set to 0% in the current scenario. The temperature reduction effect of greening was quantified from the difference between the calculation cases using each greening scenario and the case without vegetation. As a result, the daytime temperature reduction effect was the largest, at 0.74°C in the 50% greening scenario and 1.04°C in the 100% greening scenario. The electricity consumption per household was estimated from the spatial and temporal distribution of temperature, and electricity consumption was calculated by multiplying this by the number of households in the house. The calculation method for electricity consumption is based on temperature sensitivity using residential electricity monitoring data. The effect of greening on electricity consumption reduction was calculated from the difference in calculation results between the greening case and the current situation case. For the greening case, the temperature calculation results of a 50% greening scenario, which assumes coexistence with buildings, were used. As a result, it was estimated that a reduction in electricity consumption of 20.1 [MWh/day] could be achieved in Nagano City.