Hard hybrid configuration

The simultaneous utilization of FCS and battery within a fuel cell propulsion system can be accomplished by two basic ways (i) the battery pack can be minimized (but not eliminated as in full power) assigning the role of generating most energy required by the load to the FCS (soft hybrid configuration), (ii) the FCS can be sized to provide the base load, i.e. a power value close to the average power of the expectable road mission (hard hybrid configuration), while larger battery pack are necessary to satisfy the dynamic requirements. 

The main results of the experimental tests regarding the hard hybrid configuration on the R47 cycle are reported in Fig. 6.27a-c. The Fig. 6.27a shows the distribution of the power between FCS, electric drive, battery pack versus the cycle length. The output power of the fuel cell system is fixed at two constant values by... 

Fig. 6.27 Experimental results obtained on the fuel cell power train in hard hybrid configuration for the R47 driving cycle a battery, input electric drive, and output DC-DC converter powers versus cycle length, b hydrogen, input and output DC-DC converter powers versus cycle length, c battery state of charge versus cycle length...

Fig. 6.29 Stack and fuel cell system efficiency versus cycle length in hard hybrid configuration on the R47 driving cycle...

The values of efficiency obtained for the main components of the power diive by experimental measurements are reported in Table 6.6 for R40 cycle in soft and hard hybrid configurations. The evaluation of power train total efficiency takes... 

Fig. 7.58 Power distribution between FCS, electric engine, and batteries as function of cycle length for three successive R40 cycles at 50 A s and DC-DC output power constant at 5 kW (hard hybrid configuration)...

The instantaneous efficiency of the stack and FCS are shown in Fig. 6.29 for R47 cycle in hard hybrid conhguration and in Fig. 6.30 for R40 cycle in soft hybrid configuration. According to the results obtained in steady-state operation, during the low load phases the stack efficiency reaches the value of about 0.7, whereas during the power variations required by the electric drive the efficiency decreases down to the lowest value of about 0.6, in correspondence with the most... 

Finally, an alchemical free energy simulation is needed to obtain the free energy difference between any one substate of system A and any one substate of system B, e.g., Ai- In practice, one chooses two substates that resemble each other as much as possible. In the alchemical simulation, it is necessary to restrain appropriate parts of the system to remain in the chosen substate. Thus, for the present hybrid Asp/Asn molecule, the Asp side chain should be confined to the Asp substate I and the Asn side chain confined to its substate I. Flat-bottomed dihedral restraints can achieve this very conveniently [38], in such a way that the most populated configurations (near the energy minimum) are hardly perturbed by the restraints. Note that if the substates AI and BI differ substantially, the transfomnation will be difficult to perform with a single-topology approach. 

The size of the reagent is not the only controlling factor since a change in the hardness of the nucleophile implies a modification of its valence orbitals and also of its HOMO energy level (Scheme 29) (160). When the level is high (i.e., in a hard nucleophile), frontier-orbital interaction is predominant. When the level is low (i.e., in a soft nucleophile), the relative importance of the nucleophile HOMO-substrate superjacent MO (161) interaction is increased. The structure of the latter is shown below (Scheme 30) for the Si-F bond. The big lobe of the Si hybrid orbital points to the rear in the superjacent MO, which therefore favors inversion of configuration. 

The two crystalline forms of carbon are diamond, which has a tetrahedrally bonded sp configuration, and graphite, which has a trigonally bonded sp configuration. The various forms of noncrystalline carbon, such as hard and soft forms of hydrogenated amorphous carbon a-C H, can be considered as hybrids of... 

The foundation for the hybrid microcircuit is the substrate, which provides the base on which the circuit is formed. The substrate is typically ceramic, a mixture of metal oxides and/or nitrides and glasses that are formulated to melt at a high temperature. The constituents are formed into powders, mixed with an organic binder, patterned into the desired shape, and fired at an elevated temperature. The result is a hard, brittle composition, usually in the configuration of a flat plate, suitable for metallization by one of the film processes. The ceramics used for hybrid applications must have certain mechanical, chemical, and electrical characteristics as described in Table 11.4. 

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