Combined cycle gas turbine system optimization for extended range electric vehicles

Abstract

In order to meet the Corporate Average Fuel Economy standards for passenger vehicles in 2025, car manufacturers are exploring several alternative energy converters to replace the Internal Combustion Engine, which has demonstrated limited efficiency improvement. Recent studies explored the use of a Gas Turbine as the primary vehicle driver in a hybrid powertrain; however, none evaluated the implementation of a Combined Cycle Gas Turbine, which offers higher efficiency. This study presents a methodology for the design and optimization of the most optimal combined cycle system configuration, suitable to replace the engine in a series-hybrid extended-range electric vehicle, and investigates its potential fuel savings. The two-steps methodology consists of conducting first an exergo-technological analysis using a Non-dominated Sorting Genetic Algorithm to identify the best suitable combined cycle configuration for integration in a series hybrid powertrain. Second, a series-hybrid extended range vehicle model is developed, to assess the consumption savings of the prioritized combined cycle on the Worldwide Harmonized Light Vehicle Test Cycle. The Reheat Gas Turbine combined to a Turbine Reheat Steam Rankine Cycle system is prioritized, for offering the highest efficiency and an acceptable vehicle integration complexity among the other investigated systems. Consumption results show fuel savings up to 23.6% with the prioritized system as compared to a reference extended-range electric vehicle equipped with an engine and savings up to 17% compared to other gas-turbine systems presented in the literature, depending on the battery size, the trip length, and the maximum turbine inlet temperature. Consequently, combined-cycle gas-turbine systems present a serious alternative to replacing internal combustion engines on series hybrid electrified vehicles if the cost-effectiveness of these systems was proven.