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Brake energy recovery is one of the key components in today's hybrid vehicles that allows for increased fuel economy. Typically, major engineering changes are required in the drivetrain to achieve these gains. The objective of this paper is to present a concept of capturing brake energy in a mild hybrid approach without any major modifications to the drivetrain or other vehicular systems. With fuel costs rising, the additional component cost incurred in the presented concept may be recovered quickly. In today's vehicles, alternators supply the electrical power for the engine and vehicle accessories whenever the engine is running. As vehicle electrical demands increase, this load is an ever-increasing part of the engine's output, negatively impacting fuel economy. By using a regenerative device (alternator) on the drive shaft (or any other part of the power train), electrical energy can be captured during braking.

A simulation framework with a validated system model capable of estimating fuel consumption is a valuable tool in analysis and design of the hybrid vehicles. In particular, the framework can be used for (1) benchmarking the fuel economy achievable from alternate hybrid powertrain technologies, (2) investigating sensitivity of fuel savings with respect to design parameters (for example, component sizing), and (3) evaluating the performance of various supervisory control algorithms for energy management. This paper describes such a simulation framework that can be used to predict fuel economy of series hydraulic hybrid vehicle for any specified driver demand schedule (drive cycle), developed in MATLAB/Simulink. The key components of the series hydraulic hybrid vehicle are modeled using a combination of first principles and empirical data. A simplified driver model is included to follow the specified drive cycle.

This paper describes installation and testing of electrified engine accessories and fuel cell auxiliary power units for a Class-8 tractor. A 2.4 kW fuel cell APU (Auxiliary Power Unit) has been added to supply a 42 V power supply for electrification of air conditioning and water pump systems. A 42/12 V dual alternator was used to replace the OEM alternator to provide safety back-up in case of fuel cell failure. A QNX Real Time Operating System-based (RTOS) Rapid Prototype Electronic Control System (RPECS™), developed by Southwest Research Institute (SwRI™), is used for supervisory control and coordination between accessories and engine. A Controller Area Network (CAN) interface, from the engine Electronic Control Unit (ECU), and the RS232 interface, from the fuel cell controllers, provide system data and control for RPECS. Custom wiring to the hydrogen, water pump, and air conditioning systems also provide data to RPECS. The water pump system controller is autonomous.