Bus for Urban Public Transport: Energy Performance Optimization

Abstract

Nowadays many people use public transports in urban centers. Consequently, every day a lot of buses move within cities, trying to ensure the best service to citizens. During the year buses become crowded places and using an air conditioning system in constant operation, it tries to ensure a certain condition of comfort for the passengers on board. The aim of this study is to analyze and optimize the energy performance of a bus shell, identifying practical solutions have not yet been adopted in order to reduce the impact of air conditioning on bus’ consumption and, therefore, on air pollution. For this reason it was decided to conduct a thermal analysis of a bus for public transport, in order to understand the behavior of the bus shell and to deduce possible optimization measures that have not yet been made until now. The analysis was carried out considering the hottest day of July and the coldest day of January, considering the operating conditions based on the most common graphics TGM (Average Daily Traffic) able to define the concentration of traffic city during the 24hours per day. The study was done using the dynamic simulation software TRNSYS. With this software it was possible to recreate faithfully the structure of the bus and the external environmental conditions, assessing the impact of different technical solutions for an improvement of internal conditions and a reduction of the cooling capacity required. As the presence of passengers on public transport are considered like a “benefit” during the winter, the analysis is started with the identification of a summer solution and the subsequent evaluation of this solution for the winter time. The aim of this study was to optimize the bus shell and select the most appropriate solutions. Regarding the transparent surfaces it has been given importance to factors such as the thermal transmittance and the solar gain factor (g-value). Aware of the influence given by the solar radiation on the energy loads, bus energy performance were simulated also considering different types of paintwork with high reflectance.