In order to examine the feasibility of integrating external solar heat into the water steam cycle of a power plant, a model based on an existing reference plant was de­fined. This reference plant is a typical fossil fueled conventional steam power plant with an output of 393 MW and 7 feed-water preheating stages. Using APROS a com­prehensive model of this power plant was built-up, adapted and parameterized. Es­pecially the parameterizing is a very time-consuming step due the great amount of lay-out data like geometries, isometries, geodetic elevations, thermodynamic data, valve characteristics and automation concepts that have to be integrated into the model.

The power plant has been subdivided into more than 500 single components. For each component the one dimensional unsteady differential equations for the conser­vation of mass, momentum and energy are solved. Heat transfer, heat capacity of solid walls and two phase flow phenomena are taken into account. On the basis of this model several different kinds of plant configurations with or without an external heat source have been simulated. Careful calibration of the model has been carried out to meet the steady-state design and guarantee values.

To model the parabolic trough collector in APROS, design values calculated by steady state simulations combined with data taken from the literature were used [1,9]. The generation of steam with a heat capacity of 60 MW at noon in July was set as boundary condition for the collector design. The simulation is done with parabolic collectors of the type LS-3 (see figure 2) with a length of 100 m. Ten of them are added up to a 1000 m collector line. According to this, 15 lines in parallel are neces­sary to provide a peak load of 60 MW required for the simulation.

The collector efficiency is assumed to be constant at 67 %. This simplification is of sufficient accurancy for the simulations carried out in this paper, but will be corrected in future work. The collector feedwater pump control guarantees that the water pumped through the absorber tubes gets vaporized and superheated to a constant temperature of 380°C.