Phase change material-based rooftop on public transport for thermal management✰

Phase change materials (PCMs) are used in buildings and automobiles to control the interior temperature, following to their high thermal storage capacity and energy efficiency. In summer, controlling the interior temperature of vehicles can be difficult, especially in cities where public transportation is excessively crowded. Typically, heating, ventilation, and air-conditioning systems are included to provide thermal comfort inside vehicles, but they use a significant amount fuel, which ultimately have negative impacts on the environment. In this study, a prototype bus model was developed from an actual bus and scaled-down to 1/20th size. A bulb was used as an internal heat source and experiments were conducted under the sun in summer to reflect scenarios of buses stuck in traffic. Various cases were considered by opening and closing the windows and doors and placing the PCM layer on the roof and covering the bulb. The results demonstrate that when the PCM is used to cover the bulb and roof, the interior temperature can drop to the ambient temperature and remain there for a longer period of time. In fact, keeping the windows and doors open results in a significantly lower indoor temperature than when they are closed. The results show that the heat from the engine makes a major contribution to raising the temperature inside of the vehicle. The results from the opened cases can be applied to various forms of public transportation worldwide, but for many closed vehicles, additional ducting systems integrated with a PCM may be the best option.