Hardware electric power

Occasionally an incident occurs that results in a common mode failure. This is a single event that affects a number of pieces of hardware simultaneously. For example, consider several flow control loops similar to Figure 11-4. A common mode failure is the loss of electrical power or a loss of instrument air. A utility failure of this type can cause all the control loops to fail at the same time. The utility is connected to these systems via OR gates. This increases the failure rate substantially. When working with control systems, one needs to deliberately design the systems to minimize common cause failures. 

Wires and cables just carry the electric current and the electric network needs a multitude of other electric equipment including connectors, switches. .. electric power equipment motors and controls measuring and control equipment lighting and wiring equipment current-carrying equipment non-current-carrying wire devices pole line hardware. 

According to these calculations, the option of applying fuel cell cascades in order to increase the electric power output and thereby increase the system efficiency is an interesting option. From an economical point of view, the additional hardware installations which are necessary for such a system stand against this configuration, at least for small systems. For large systems - for example in the Megawatt class -... 

The fuel cell was discussed in Chapter 6. The automobile fuel cell will likely make a profound impact on the private automobile a repeat of the discussion of how fuel cells function is warranted. A fuel cell is a special type of battery. In commonplace batteries, the chemicals and hardware used to produce the electric current are placed within the battery package. As the battery is used, the reaction products remain within the confines of the package. Because of the fixed mass of reactive chemicals, a battery has a fixed total power output. When it is depleted, it must be replaced or recharged. Recharging is the slow process of driving the chemical reaction in reverse with an external source of electric power. 

The need for high-reliability power has grown with the Internet and related digital hardware. In 1998 the Internet consumed 8% of U.S. electric power up from less than 1% in 1993. Computers and other office equipment consumed 13% of the country s electricity, up from 5% in 1993. The U.S. electric grid can be viewed as the equivalent of a huge 30% efficient natural gas power plant. 

Pumps, motors included, normally represent 5-10% of the total major equipment cost for new plant construction. They represent a much larger share of the total cost for electrical hardware and power wiring and this cost is usually several times that of the equipment cost for pumps and drivers. Pumps are significant consumers of process energy. 

However, the requirement of a certain quantity of CO2 at the cathode to form the carbonate ion is a drawback in the plant management. Furthermore, the high contact resistances and the cathode resistance increase overpotentials and decrease efficiency, and concentration polarization limits the electric power densities. Finally, the main challenge for MCFC developers derives from the very corrosive and mobile electrolyte, which requires the use of nickel and high-grade stainless steel for the cell hardware. Higher temperatures promote material problems, and also cathode... 

Developing specifications for systemwide power-conditioning/backup hardware requires careful analysis of various factors before a particular technology or a specific vendor is selected. Key factors in this process relate to the load hardware and load application. The electrical power required by a sensitive load may vary widely, depending on the configuration of the system. The principal factors that apply to system specification include the following ... 

Small devices providing fast, albeit somewhat low resolution, analytical data are useful in applications where it is necessary for users to be unencumbered by large amounts of hardware both size and weight become important here. Resupply of electrical power, batteries, is another significant problem in many cases. In general, smaller, lighter devices use less battery power that larger instruments. 

Table 4.8 provides the complete operation and maintenance cost of RO system, which includes power, membrane module and micron filter cartridge re-plaeement costs, chemical consumption for cleaning and storage, etc. Feed capacity and recovery were assumed to be 2 m /h and 60%, respectively. The operational time for system was assumed to be 10 h per day in view of the fact that electric power supply in remote villages is restricted to a few hours per day. Depreciation costs were taken as 10% of the total capital investment while life of hardware is expected to be 10 years. Membrane life was foimd to be 3 years as per data collected at village sites where plants have been operated. 

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