Objectives and Application of Cogeneration Technology in Krakow

Generating both thermal and electrical energy in a cogenerating plant with district beating can save as much as one-half of the comparable costs of individual heating and power plants, including savings realized from avoiding separate fuel storage and handling facilities. These reasons wen considered when the Leg plant was designed with a cogeneration process in an effort to extract maximum energy from a low-heating-value coal.

Cogeneration efficiency is calculated by the following formula (El Wakil 1984):

n = E + Hs
Qa
where
E = electric energy generated,
Hs = heat energy (enthalpy of steam entering the process less the enthalpy of the process condensate returning to the plant),
Qa = heat added to the plant (in coal, etc.), and
n = cogeneration plant efficiency.


It is estimated that a thermal energy plant alone has an overall efficiency of 65%. The overall thermal efficiency of an electricity-generating plant using steam turbines cannot exceed 35% when the exhaust steam is dumped as waste, as is the case at Krakow's Skawina plant. The conventional method of producing beat and electricity separately loses more than 50% of the energy content of the fuel. With cogeneration it is possible to reduce the loss to an average of 20% to 30%. Some Scandinavian cogeneration facilities report efficiencies that reach up to 90% - a loss of as little as 10% of the thermal energy of the fuel (District Heating and Cooling Committee 1987).

The Leg plant, however, has been hampered in realizing this optimum due to operating and maintenance deficiencies caused by the unavailability of repair and maintenance parts and supplies, lack of hard currency to import those items, and low worker productivity.

| Operations and Economic Critique |