Soft hybrid configuration

A further requirement to be satisfied by the oxidant supply device is represented by dynamic performance in a wide range of air flow rates. This aspect is crucial in some hybrid power train operative modes characterized by high stack dynamics (full power or soft hybrid configurations, see Sect. 5.5). 

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 soft hybrid configuration represents the most flexible solution for the energy management in all the possible driving conditions of an automotive... 

Fig. 6.30 Stack and fuel cell system efficiency versus cycle length in soft hybrid configuration on the R40 driving cycle...

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... 

Fig. 7.57 Power distribution between FCS, electric engine, and batteries as function of cycle length for R40 cycle at 10 A s as stack current variation rate (soft hybrid configuration)...

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... 

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 softness of a carbanion is related to the hybridization of the carbon. Higher p character increases the softness sp > sp > sp) and configurational instability of the carbanion. Reactions involving carbanions formally derived from alkanes often lead to racemization, whereas configuration is retained at the alkenic carbanion center. The fact that cyclopropyl carbanions maintain their original stereochemistry (14) concurs with the above notion, as the s char-... 

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