Abstract The aim of this paper is to present and analyze the monitoring data of an innovative solar Direct Steam Generation plant for industrial processes. The objective is to quantify and evaluate the performance for two different periods of approximatively two weeks each, in winter and in summer. Pressure distribution, pressure drops and liquid level variation are compared to expected results for two characteristic days, one in each period. An innovative flow pattern analysis is presented and some optimizations are proposed to improve energy performance and plant stability. To perform this analysis a new steady-state model based on few monitoring inputs is developed. The result of the analysis for both periods shows a very good agreement between expectation and monitoring results, as long as the system is cleaned frequently. It quantifies the cleaning impact with a deviation of more than 40% in performance before and after cleaning after a period of 33 days of non-cleaning in summer. The simulation results for system head loss during start-up and shut down periods show lower values than observed due to unexpected steam in the downward pipes. A small optimization of the system layout could minimize this effect and improve the system performance. The analysis of the liquid level in winter 2015/2016 led to a new control strategy to minimize start-up losses, which had been implemented in April 2016, the results have been observed in summer 2016. Lastly, the flow pattern analysis shows that harmful flow patterns as stratified flow and dry-outs had successfully been avoided, and the main flow pattern in the steam region is stratified-wavy.