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

Solar power tower plants are pioneer candidates for electric power generation; hence, such plants concentrate solar thermal power to heat the working medium used in the power cycles. However, atmospheric effects and cloud cover 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. Three operational scenarios regarding their impact on the steam bulk temperature, productivity, and enthalpy are discussed. Among them, Scenario #3 outperforms in terms of net productivity due to the lower overall makeup required throughout the day, where the receiver can meet 93.61% of the plant steam demand when standalone, compared to 90.44% and 89.06% when Scenarios #1 and #2 are followed. From a safe operation point of view, the wall temperature of the superheater tubes on the north, east, and west sides 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 into the superheater sides not only guarantees the receiver's safety but also slightly reduces the total makeup required while improving the excess energy available.