Research on energy efficiency of various fuel cell hybrid powertrains

    Belgian scholars studied several powertrain design schemes for fuel cell vehicles and compared the powertrains and control strategies of three fuel cell vehicles: fuel cell/supercapacitor, fuel cell/conventional battery, and fuel cell/supercapacitor/conventional battery hybrid. The conclusion is that the energy efficiency of fuel cell/supercapacitor fuel cell vehicles is slightly better than the other two schemes. The research results have been published at the 27th Electric Vehicle Symposium.

    The energy-saving advantage of fuel cell/supercapacitor fuel cell vehicles mainly comes from the fact that they can frequently use high-efficiency supercapacitors for charging and discharging under transient conditions (the maximum charge and discharge current allowed by supercapacitors is much higher than that of conventional batteries). Therefore, although its vehicle weight is often higher, it is still more energy-efficient.

    The researchers also pointed out that from the perspective of battery life, component size, and transient operating conditions, a fuel cell vehicle that uses a hybrid of fuel cell/supercapacitor/conventional battery may also be a good choice.

    Integrating a standard fuel cell system into a car's powertrain does not always meet the car's power requirements. Although fuel cells have a high power capacity, that is only for stable conditions. On the contrary, their ability to output higher power instantly is relatively weak. Therefore, the high price and sluggish dynamic performance of fuel cell systems have become the biggest obstacles to the commercialization of fuel cell vehicles.

    In order to overcome this obstacle, the fuel cell system must be "hybridized" to equip itself with multiple energy storage systems (such as conventional batteries or supercapacitors, etc.) to better meet power needs while saving energy.

    The study evaluates the energy efficiency, cost and component size of different types of fuel cell systems. The researchers used Matlab/Simulink software to design and simulate a variety of fuel cell powertrains. The energy efficiency evaluation used two standard test cycles, NEDC and FTP75, for simulation. They also used two control logics based on the fuel cell efficiency MAP to minimize the hydrogen consumption of the simulation model.

    Control logic (1) is based on the CSEM energy efficiency MAP diagram, which can reduce the total hydrogen consumption of each test cycle. Control logic (2) is based on the CSPSO ion cluster optimization method, which coordinates the operation of multiple energy storage systems to minimize energy consumption and maintain battery power.