Project Leader:	Professor Dr-Ing Otto Geisler
Research Assistant:	Dipl-Ing M Reymann
Duration:	01.04.1992 - 31.12.1995

 

For communal and industrial energy supply gas and steam power plants are increasingly used for combined generation of electricity and thermal or process heat. In most cases both the electric as well as the heating loads fluctuate substantially, on a daily or seasonal basis. Furthermore, because the operation of the gas turbines is significantly influenced by the ambient conditions, the operating point of the plants can vary within a fairly wide rang.

The operating behaviour of gas and steam plants is determined essentially from the characteristics of the gas turbine used and the designs of the steam boiler and the steam turbine. Simple plants with a gas turbine, a heat-recovery steam generator and a back pressure steam turbine are characterised by a rigid power and heat coupling. This inflexible coupling can be eased through the introduction of additional degrees of freedom (e.g., splitting of the turbine power in two units, with variable supplementary firing or by using a steam turbine with extraction and condensation units). During operation various regulation concepts can also offer additional adjustment possibilities.

In the framework of this project combined gas-steam CHP power plants were optimised for various application cases. This was done by dividing the overall plant into sub-systems and performing detailed plant simulation computations on each part. To describe the operating behaviour appropriate energetic and exergetic coefficients were defined. From the results it was possible to determine the thermodynamically optimal plant configuration in each case, taking into consideration the characteristics of each application and the boundary conditions.