Combined Heat and Power Cogeneration

A more complex utility is combined heat and power (or cogeneration). Here, the heat rejected hy a heat engine such as a steam turbine, gas turbine, or diesel engine is used as the hot utility. 

Fundamentally, there are two possible ways to integrate a heat engine exhaust. In Fig. 6.31 the process is represented as a heat sink and heat source separated hy the pinch. Integration of the heat engine across the pinch as shown in Fig. 6.31a is coimterproductive. The process still requires QHmm, and the heat engine performs no 

Now let us take a closer look at the two most commonly used heat engines (steam and gas turbines) to see whether they achieve this efficiency in practice. To make a quantitative assessment of any combined heat and power scheme, the grand composite curve should be used and the heat engine exhaust treated like any other utility. 

Energy Targets for Heat Exchanger Network and Utilities 195 

The turbine isentropic efficiency tjt measures the ratio of the actual to ideal work obtained  

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Combined heat and power cogeneration). Combined heat and power generation can have a very significant effect on the generation of utility waste. However, great care must be taken to assess the effects on the correct basis. 

The United States obtained about 9 percent of its electricity from combined heat and power (cogeneration) systems as of 1997. Cogeneration is more prevalent in some European nations than in the... 

This is particularly important when considering the effect that combined heat and power generation (cogeneration) has on utility waste. 

The term "cogeneration is sometimes used to describe a combined power plant, but it is better used for a combined heat and power (CHP) plant such as the one shown in Fig. 1.6 (see Ref. [2] for a detailed discussion on CHP plants). Now the fuel energy is converted partly into (electrical) work (W) and partly into useful heat (Qu) at a low temperature, but higher than ambient. The non-useful heat rejected is (2nu-... 

Fig. 1.6. Cogeneration plant (combined heat and power plant).

THE GAS TURBINE AS A COGENERATION (COMBINED HEAT AND POWER) PLANT... 

Chapter 9. The as turbine as a cogeneration (combined heat and power) plant... 

Horlock, J.H. (1997). Cogeneration—Combined Heat and Power Plants. 2nd edn, Krieger, Malabar. Florida. 12 Porter. R.W. and Mastanaiah, K. (1982), Thermal-economics analysis of heat-matched industrial cogeneration systems. Energy 7(2). 171-187. 

Horlock, J. H. (1997). Cogeneration—Combined Heat and Power Thermodynamics and Economics. Malabar, FL KiTcgcr Publishing Company. 

The introduction of the internal combustion engine in the late nineteenth century opened up an entirely new approach to combined heat and power. Rather than using the same fluid for the heat and power process as was the case with hot air and steam processes, the tremendous waste heat generated by the internal combustion process can easily be transformed into useful heat. Cogeneration applications using stationary engines were common in Europe prior to World War I and remain quite popular because the heat is relatively... 

Combined Heat and Power (CHP) systems, also called cogeneration systems, generate electricity (or... 

Designs often include boilers with economizers and pendant superheaters because many of the largest manufacturing operations require additional mechanical or electrical power to process steam and use combination heating and power services (cogeneration). 

Combined heat and power (CHP) (Cogeneration) -The thermal energy created while converting fuel to electricity would be utilized for heat in addition to electricity in remote areas and electricity and heat for sites that have a 24 hour thermal/electric demand. 

The cycles considered so far in this chapter are power cycles. However, there are applications in which Rankine cycles are used for the combined supply of power and process heat. The heat may be used as process steam for industrial processes, or steam to heat water for central or district heating. This type of combined heat and power plant is called cogeneration. A schematic cogeneration plant is illustrated in Fig. 5.19. A different schematic cogeneration plant is illustrated in Fig. 5.20. 

Significant energy conservation is achieved by the well-established method of combined heat and power generation (cogeneration). The heat is usually in the form of intermediate or low-pressure steam, and the power as direct mechanical drives or as electricity generated with turbo-altemators. The choice of systems is usually between back-pressure steam turbines, or gas turbines with waste-heat boilers for the process steam. The amount of power generated is usually determined by the demand for heat. 

Many studies have shown that the potential market is enormous. For instance, a 2000 study for the doe s Energy Information Administration found that the technical market potential for combined heat and power (chp) at commercial and institutional facilities was 75,000 mw, of which more than 60 percent was in systems less than 1 mw in size. This sub-MW market is a very good match for fuel cell technologies. The remaining technical potential in the industrial sector is about 88,000 mw. That analysis did not look at the opportunity created by heat-driven chillers to expand the market for cogeneration, nor did it contemplate cost-effective systems in sizes below 100 kW, as are being pursued by a number of fuel-cell (and other) companies.37... 

The net electrical efficiency of a PAFC is typically about 40%, and a total efficiency of approximately 85% when operating in cogeneration (combined heat and power applications). 

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