Modeling On/Off-Design Performance of Solar Tower Plants Using Saturated Steam

Abstract

This works presents a model for the performance prediction of concentrating solar tower plants using saturated live steam at on and off-design. For solar tower plants, the most important and critical element is the steam generator that, in this model, is supposed to produce saturated steam. The solar receiver is thus assumed to comprise several panels, each one of which is formed by a number of pipes. Given some boundary and initial conditions, heat and mass balances for the plant at any rated conditions can be obtained. Off-design operation is then defined by a modified map of the radiative heat flow onto the panels, though other operating conditions featuring new ambient conditions or abnormal operation of the plant can be simulated as well. As a result, a new set of heat and mass balances and performance data — efficiency, steam generation, live steam pressure and temperature, bleed pressures — are obtained. The developed model demonstrates its functionality during the design process in three ways. On one hand it allows to calculate and optimize the performance of the plant at rated conditions, developing a sensitivity analysis of the parameters involved. On the other hand, various off-design conditions can be studied and, consequently, it is possible to carry out a long term — for instance yearly — thermodynamic and economical analysis. Finally, it allows detecting undesirable operating conditions of one or more components that could eventually lead to a not admissible operation of the plant: for example a too high vapor fraction in the steam generator, a too low deaerator pressure, cavitation of pumps or other situations that are not appropriate for the steam turbine.