Cogeneration typical systems

Typical Systems All cogeneration systems involve the operation of a heat engine for the production or mechanical work hich, in nearly all cases, is used to di ive an electric generator. The commonest heat-engine types appropriate for topping-cycle cogeneration systems are ... 

Large industrial operations with on-site needs for electricity and heat in the form of process steam, direct heat, and/or space heat. Typical Systems All cogeneration systems involve the operation... 

Most of the turbines you will encounter in your work are called topping, or extraction, turbines. The idea of such a turbine is to extract much of the potential work from the motive steam, and then use the exhaust steam to reboil towers. Typically, the energy content of the exhaust steam is only 10 to 20 percent less than that of the motive steam. That is the calculation we just did with the Mollier diagram. The rest of the energy of the steam may then be used as the steam condensers, to reboil towers. This sounds pretty efficient. It is the basis for the new cogeneration projects you may have heard about. Of course, this system was used by the British Navy in the nineteenth century. 

Comparison with Alternative and the Selection of Overall Optimum. The alternative to a cogeneration system is typically taken as a low pressure boiler or furnace, and purchasing electricity from the utility. It is when the economy of the optimally designed cogeneration system is compared to the alternative, that a system s true potential can be shown. 

NOx and SOx emissions from SOFC systems are negligible. They are typically 0.06 g/kWhe and 0.013 g/kWhe. SOFCs also produce high-quality heat with their working temperature of 850°C. This makes combined heat and power production possible with SOFC systems. The total efficiency can then reach 85%. Advanced conventional cogeneration of heat and power can reach total efficiencies up to 94% with electrical effi-... 

SOFCs, as shown in Figure 11, use a hard, non-porous ceramic compound as the electrolyte. Since the electrolyte is a solid, the cells do not have to be constructed in the plate-Uke configuration typical of other fuel cell types. SOFCs are expected to be aroimd 50 to 60 percent efficient at converting fuel to electricity. In applications designed to capture and utilize the system s waste heat (cogeneration), overall fuel use efficiencies could top 80 to 85 percent. 

Structures, systems, and components of a nuclear cogeneration plant with the KLT-20 reactor installation are developed with consideration of natural and human-induced external impacts typical of a floating NPP location site and transportation, and comply with the OPB-88/97 safety regulations of Russia, the Sea Shipping Register of Russia and olher regulations. 

City gas (town gas) is used as the state-of-the-art fuel for the first-generation commercial SOFC systems. City gas, consisting mainly of CH4 from the natural gas, may be partially pre-reformed before supplying to the SOFC systems. Figure 6.25 shows the comparison of the current-voltage (1-V) characteristics between a H2-based fuel and a typical SOFC fuel (50% pre-reformed CH4 with S/C = 2.5) [261]. The cross section of a t3 pical SOFC used for this electrochemical measurement (see Fig. 6.25) is shown in Fig. 6.26. This simulated practical SOFC fuel for distributed cogeneration systems consists of the one-to-one mixture of fuUy reformed CH4 with S/C = 2.5 and non-reformed CH4 with S/C = 2.5. While too low S/C may result in carbon deposition, excessive amount of H2O causes lower OCV and may cause re-oxidation of Ni at high fuel utilization of the SOFC systems. 

A typical cogeneration system consists of an engine and a steam turbine, or a combustion turbine that drives an electrical generator. A waste heat exchanger recovers waste heat from the engine and/or exhaust gas to produce hot water or steam. Cogeneration produces a given amount of electric power and process heat with 10 to 30 % less fuel than it takes to produce the electricity and process heat separately. 

The modem MCFC system has a high efficiency typically above 50 % and very low emissions. Since it operates at high temperature (about 650 C) it can be used for cogeneration, combined heat and power, and distributed electricity generation. Most applications have so far been for stationary plants in hospitals, hotels, and resorts where the fuel is natural gas. The MCFC has been demonstrated to run on propane, coal gas, and anaerobic digester gas [90, 94, 96, 97]. Plants have been published for integrated coal gasilier/MCFC systems. 

Steam turbines are often used in cogeneration systems that produce heat for industrial processes as well as power. A typical application is shown in Fig. 6.69. In this case an... 

Molten carbonate fuel cells (MCFCs) are high-temperature systems that use an immobilised liquid molten carbonate salt as the electrolyte. Salts commonly used include lithium carbonate, potassium carbonate and sodium carbonate. Typically MCFC units have an operating temperature of around 650°C and an efficiency of around 60%. (This can rise to as much as 80% if the waste heat is used for cogeneration.)... 

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