A Novel Transient Thermal Analysis of Direct Steam Generation External Receivers in Solar Power Tower Plants Under Atmospheric Conditions Fluctuations

Abstract Solar power tower plants are leading candidates for electric power generation. They concentrate solar thermal power to heat the working medium used in the power cycle. However, atmospheric effects cause spatial and temporal fluctuations in solar thermal power during the day. Thus, evaluating the net power acquired by solar receiver tubes as a function of time and location is of high interest. A thorough dynamic thermal analysis procedure is developed in this research and examined under realistic weather conditions to demonstrate its potential for managing complex computations thoroughly and cost-effectively. This research integrates high-accuracy solar field simulations by the solarpilot tool. In addition, a quasi-transient 1D numerical simulation is implemented to predict the net heat flux and tube wall temperatures. The Kandlikar model is used to precisely characterize biphasic flow boiling inside receiver tubes. The current analysis is limited by its dependence on a 1D axisymmetric approximation and natural convection heat losses. Three operational scenarios regarding their impact on the steam bulk temperature, productivity, and enthalpy in the Ivanpah I plant are discussed. One of the scenarios outperforms in net productivity due to the lower overall makeup required throughout the day, enabling the receiver to meet 93.61% of the plant steam demand in standalone mode, compared to 90.44% and 89.06% when the other two scenarios are followed. From a safe-operational point of view, tube wall temperature in the upper part of the receiver facing north, east, and west exceeds the maximum allowable limit. To address this issue, a mass flow interchange approach with optimal circulation factors between the opposing sides is proposed using a temperature-control valve. It was found that the uneven distribution of steam fed to the superheater sides not only ensures the receiver's safety but also slightly reduces the total makeup required while increasing the excess energy available.