Electrical Power Train

Schematic of a fuel cell/battery hybrid configuration. 

In this configuration, batteries with a high discharging rate should be chosen in order to reduce the Ah, mass, and volume of the battery bank. For example, for a 60 kW power output at a voltage of300 V, if the battery discharges at 1 C, the battery should be around 200 Ah but if the battery can discharge at 5 C, the battery only needs to be around 40 Ah. This means that the 5 C battery will be around one fifth of the 1 C battery in Ah, mass, and volume. 

A higher discharge rate will shorten the life of the battery. However, the high discharging process only affects the battery for a short time its life should not be seriously affected. 

If the battery cannot discharge at a high rate, its mass and volume will exceed those of a fuel cell system for generating the same level of power. In such a case, it is better to use the fuel cell system to provide all of the power for all driving situations and use the battery only to start up the fuel cell system and to collect the regenerative breaking power. 

---

The integration of a fuel cell system in an electric power train results in a rather complex system constituted by the combination of energy storage systems, energy sources, electric converters and various auxihary devices. 

Buchi F, Tsukada A, Rodutz P, Garcia O, Ruge M, Kotz R, Bartschi M, Dietrich P (2002) Fuel cell supercap hybrid electric power train. In Proceedings of European fuel cell forum conference, Lucerne, pp 218-231... 

An important point to consider about the stack management, with reference to an electric power train operating in dynamic conditions, as determined by road requirements, is the regulation of the stack temperature together with the other control parameters of water and reactants to avoid mass transfer limitations and membrane drying out or flooding. Moreover, the interaction between stack and auxiliaries has to be balanced taking into account the optimization of fuel cell system efficiency and reliability (see Sect. 4.6). 

The electric drive, DC-DC converter and Pb battery pack are equipped with sensors able to monitor all the main parameters of the electric power train during the tests. All the analogic and digital signals are connected to a J-space prototyping system, programmed by means of MathWorks MATE AB development tools. 

Electric power trains are locally emission free, however the energy storage, with today s battery technology, is limited in energy density to about ISOWhkg if advanced lithium batteries are used and refueling time takes a few hours. So the range and availability of the vehicle is lower than for cars with ICE power trains. 

Fig. 8.14 (a) Straight fuel cell powertrain, (b) Hybrid electric power train with fuel cell and electric storage. 

In Chap. 27 Alain Biahmou discusses the concept of sustainable mobility as a field of application of Concurrent Engineering. In particular, the electrical power train of road vehicles has an increasingly significant role. Besides delivering benefits in air and noise pollution, it encompasses huge challenges in practical usability. 

The RH consists of two independent, redundant mechanical subsystems, each of which receives electrical power from one of two separate and redundant electrical power trains. Each subsystem consists of one RHR pump one RHR heat exchanger and the required piping, valves, and instnunentation. The RHR pumps and heat exchangers are located in... 

Hence, to accumulate the necessary voltage for technical applications, e.g., 200 00 V, for an electrical power train in a car, cells must be crmnected in series. Dedicated bipolar arrangements of cells have been designed and put into operation for serial connection, taking into consideration also the necessary parallel mass flow of fuel and oxidant from a manifold into each individual cell and the respective removal of the product. Such an arrangement of cells is called a fuel cell stack, combining the electrical serial connection of individual cells with a parallel connection for mass flow. 

Burke, A., H. Zhao, and E. V. Gelder. 2009. Simulated performance of alternative hybrid electric power trains in vehicles diuing various driving cycles. EVS24 International Battery, Hybrid and Fuel Cell Electric Vehicle Symposium, Norway. Fuel Cells, 1-16. 

---