COGENERATION

HEAT TO POWER RATIO

The most important parameter in cogeneration is ‘heat to power ratio’ which determines the proportion of generated heat to electrical power in a single cogeneration system. Table 1 shows the heat to power ratios for different cogeneration types. Each facility has different demand of heat and electricity and those demands should be matched with the heat to power ratios of different cogeneration systems to select the most appropriate one. Table 2 presents different heat to power ratios that are suitable for adequate industries.

  • TABLE 2: TYPICAL HEAT TO POWER RATIOS FOR DIFFERENT ENERGY INTENSIVE INDUSTRIES BASED ON [5]

    • COGENERATION TYPES

    There are three types of cogeneration divided by virtue of usage. First one is industrial cogeneration which exists in factories where thermal and electrical energy is needed. Instead of buying electricity and generating heat in boilers it is possible to setup cogeneration system which will provide both. In case of demand of coolness, it is also possible to install absorption chillers which will turn the system into trigeneration. Those solutions significantly improve economical aspects of the company. An ideal example of industrial cogeneration is a modern sewage plant. Those plants need heat to run the rectifying process and while rectifying there are biogases produced which can be used to feed the cogeneration system with fuel. Such a plant is self sufficient and it can even provide the excess of electricity to the grid. Such plants usually produces useful heat of temperature 140oC or higher.

    Another type is heating cogeneration. Such systems are implemented when there is large demand for heat and generation of electricity is just a byproduct, for example in district heating. Such plants usually produce useful heat of temperature between 40oC and 140oC.

    The last type of cogeneration is agricultural cogeneration which can be used for rural processes. Agriculture cogeneration plants usually produce useful heat of temperature between 15oC and 40oC.

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