Concept for energy recovery in city buses based on organic Rankine cycle system

This paper presents a concept for energy recovery in city buses, based on organic Rankine cycle (ORC) system modeling. ORC modeling provides preliminary parameters which enable estimation of transient state energy flow, especially at those points in the system where it can mostly easily be recovered (exhaust, cooling and brakes). The paper describes an easy-to-use procedure for time-domain analysis of velocity waves in a real driving cycle. The results were combined with a dynamic system model of a city bus in block diagram environment, taking into account the influence of parameters assumed to have the greatest impact on the model’s accuracy. Average fuel consumption and producer specifications (maximum vehicle speed, rate of acceleration) were used as reference parameters. A procedure was developed for tuning the simulation model according to the reference parameters. The results of the simulation, based on real measurements of Lodz city traffic parameters, are discussed and an estimate is made of the potential for energy recovery in city buses.