On the Optimal Thermal Management of Hybrid-Electric Vehicles with Heat Recovery Systems

A general framework to combine optimal energy management (powertrain supervisory control) and thermal management in Hybrid Electric Vehicles (HEV) is presented. A HEV system with engine exhaust aftertreatment and exhaust heat recovery system is simulated under various scenarios, including warm and cold start. Optimal strategies are derived from Pontryagin Minimum Principle (PMP). The concept of fuel equivalent of thermal energy variations – similar to the equivalence factors for battery energy of standard Equivalent Consumption Minimization Strategy (ECMS) – is introduced. The PMP-based strategies are compared with a heuristic, rule-based strategy. The benefits in fuel economy and reduction of pollutant emissions that are obtained for several scenarios are very promising.