Power cycles

Power cables Power cycles Power factor Powerforming... 

In a combined power cycle operation, clean (sulfur- and particulate-free) gas is burned with air in the combustor at elevated pressure. The gas is either low or medium heat-value, depending on the method of gasification. 

Chiesa, P Consonni. S., Lozza. G. and Macchi. E. (1993), Predicting the ultimate performance of advanced power cycles based on very high temperatures, ASME paper 93-GT-223. 

We consider first Cycles A of Table 8.1 A and the a.ssociated Figs. 8.6-8.8. These are cycles in which the major objective is to separate or sequestrate some or all of the carbon dioxide produced, and to store or dispose it. This can be achieved either by direct removal of the CO2 from the combustion ga.ses with little or no modification to the existing plant or by modest restructuring or alteration of the conventional power cycle so that the carbon dioxide can be removed more easily. 

In summaiy, diesel fuel with veiy low to no sulfur content is now possible with chemical and technological advances. Along with catalytic converters, electronic fuel systems, and sensors, the diesel engine for the new millennium will he capable of complying with ever more stringent EPA exliaust emissions. The diesel engine will continue to sei"ve as the main global workliorse for all of the many thousands of different applications of its power cycle. 

Four phases of the Stirling engine power cycle. 

Stirling engines also have the maximum theoretical possible efficiency because their power cycle (their theoretical pressure volume diagram) matches the Carnot cycle. The Carnot cycle, first described by the French physicist Sadi Carnot, determines the maximum theoretical efficiency of any heat engine operating between a hot and a cold reservoir. The Carnot efficiency formula is... 

Plots of the properties of various substances as well as tables and charts are extremely useful in solving engineering thermodynamic problems. Two-dimensional representations of processes on P-V, T-S, or H-S diagrams are especially useful in analyzing cyclical processes. The use of the P-V diagram was illustrated earlier. A typical T-S diagram for a Rankine vapor power cycle is depicted in Figure 2-36. 

The efficiency of power cycles such as the Rankine cycle is given by the ratio of the net work out to the heat added. Thus from Figure 2-36 the efficiency is... 

Thermal power plant is more commonly associated with very large central power stations. The capital cost for thermal power plant, in terms of cost per installed kilowatt of electrical generating capacity, rises sharply for outputs of less than some 15 MW. It is for this reason that thermal power plant is not usually considered for industrial applications unless it is the combined cycle or combined heat and power modes. However, for cases where the fuel is of very low cost (for example, a waste product from a process such as wood waste), then the thermal power plant, depending on output, can offer an excellent choice, as its higher initial capital cost can be offset against lower running costs. This section introduces the thermal power cycle for electrical generation only. 

Figure 6.4 High-efficiency hybrid FC/Turbine power cycle.

Power conversion, ferrites in, 22 77-82 Power costs, 9 671-672 Power cycles, turbine throttle pressures of, 23 228... 

The development of thorium-based nuclear power cycles still faces various problems and requires much more R D to be commercialised. As a nuclear fuel, thorium could play a more important role in the coming decades, partly as it is more abundant on Earth than uranium and also because mined thorium has the potential to be used completely in nuclear reactors, compared with the 0.7% of natural uranium. Its future use as a nuclear source of energy will, however, depend greatly on the technological developments currently investigated in various parts of the world and the availability of and access to conventional uranium resources. 

A flow diagram for the natural gas fueled 4.5 MW class cascaded " TSOFC power cycle is presented in Figure 9-10. A brief process description is given below, followed by a performance summary. Selected state point values are presented in Table 9-11. 

Advantages, Disadvantages of Various Fuel Cell, Power Cycles... 

Proceedings of the Workshop on Very High Efficiency Fuel Cell/Gas Turbine Power Cycles, edited by M.C. Williams, C.M. Zeh, U.S. DOE Federal Energy Technology Center, Morgantown, W.V., October 1995. 

Theoretically, the Carnot vapor cycle is the most efficient vapor power cycle operating between two temperature reservoirs. 

COMMENTS The Carnot vapor cycle as illustrated by Example 2.1 is not practical. Difficulties arise in the isentropic processes of the cycle. One difficulty is that the isentropic turbine will have to handle steam of low quality. The impingement of liquid droplets on the turbine blade causes erosion and wear. Another difficulty is the isentropic compression of a liquid-vapor mixture. The two-phase mixture of the steam causes serious cavitation problems during the compression process. Also, since the specific volume of the saturated mixture is high, the pump power required is also very high. Thus, the Carnot vapor cycle is not a realistic model for vapor power cycles. 

The hot water from the bottom of the pond is pumped through a boiler, where it boils a working fluid in a Rankine power cycle, as shown in Fig. 2.31. The cooler water from the surface of the pond is used to cool the turbine exhaust vapor in the condenser. This is the same concept that is employed in the OTEC system, except that in the OTEC system the surface waters are warmer than that of the deep ocean water. 

Water has been used mainly as the working fluid in the vapor power examples of this chapter. In fact, water is the most common fluid in large central power plants, though by no means is it the only one used in vapor power cycles. The desirable properties of the vapor cycle working fluid include the following important characteristics. 

The thermodynamic power cycles most commonly used today are the vapor Rankine cycle and the gas Brayton cycle (see Chapter 4). Both are characterized by two isobaric and two isentropic processes. The vapor... 

A numerical example of the carbon dioxide supercritical cycle has been made by Feher (Feher, E.G., The super-critical thermodynamic power cycle. Energy Conversion, vol. 8, pp. 85-90, 1968). The reasons for the neglect of the supercritical cycle until now are not known. 

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