Operational/cost efficiencies

The design and optimization of a fuel cell power system is very complex because of the number of required systems, components, and functions. Many possible design options and trade-offs affect unit capital cost, operating cost, efficiency, parasitic power consumption, complexity, reliability, availability, fuel cell life, and operational flexibility. Although a detailed discussion of fuel cell optimization and integration is not within the scope of this section, a few of the most common system optimization areas are examined. 

Internal and Operational Benefits Operational/Cost Efficiencies... 

Electrical heaters must fit the barrel properly. Failure to have a solid surface-to-surface contact will cause uneven heating, hot spots in the heater, and premature heater failure. The heater should have provision for adjustment after heat up to maintain proper fit. It should be able to expand and contract without exerting undue strain on the elements. Heaters should also have an adequate kilowatt rating to insure good heater life and improve the operating cost efficiency. 

Raw materials costs dominate the operating costs of most processes (see App. A). Also, if raw materials are not used efficiently, this creates waste, which then becomes an environmental problem. It is therefore important to have a measure of the efficiency of raw materials use. The process yield is defined as... 

The wisest fan choice is frequently not the cheapest fan. A small fan operates well on its curve but may not have adequate capacity for maximum flow control, future needs, or process upset conditions. It may be so lightly constmcted that it is operating near its peak speed with no provision for speed increases in the future, if needed. As fan size is increased, efficiency generally improves and wheel speed is lower. These factors decrease operating cost and provide reserve capacity for the future. However, it is also possible to oversize a fan and impair its performance. 

Recycling is not the total answer to the soUd waste problem. However, efficiently operated recycling programs can easily divert 35% or more of municipal soUd waste away from disposal. Curbside coUection systems offer the opportunity to coUect the greatest amount of recyclables in the most cost-efficient manner. It is imperative that communities and recyclers operate programs that are glass-friendly and which result in color-separated, contaminant-free material. 

Performance data on some typical tray and compartment diyers are tabulated in Table 12-10. These indicate that an overall rate of evaporation of 0.0025 to 0.025 kg water/(s m") of tray area may be expected from tray and tray-truck diyers. The thermal efficiency of this type of diyer will vary from 20 to 50 percent, depending on the diying temperature used and the humidity of the exhaust air. In diying to very low moisture contents under temperature restrictions, the thermal efficiency may be in the order of 10 percent. The major operating cost for a tray diyer is the labor involved in loading and unloading the trays. About two labor-hours are required to load and unload a standard two-truck tray diyer. In addition, about one-third to one-fifth of a... 

Operating costs will include 5 to 10 percent of one worker s time, plus power and fuel required. Yearly maintenance costs will range From 50 to 10 percent of total installed costs. Total power for fans, dr er drive, and feed and prodirct conveyors will be in the range of 0.5 D to 1.0 D". Thermal efficiency of a high-temperature direc t-heat rotary dryer will range from 55 to 75 percent and, with steam-heated air, from 30 to 55 percent. 

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