Influence of solar field recirculation on medium-size CSP performance

This paper aims to evaluate the influence of solar field recirculation on the performance of medium-size Concentrating Solar Power (CSP) systems. Different strategies regarding recirculation paths are proposed and then compared. In particular, cases for total or partial recirculation of the solar field mass flow (those passing through, as well as those bypassing the cold tank) are compared with a strategy of no recirculation during the operating phases that occur throughout the day. The comparative analysis has been carried out by considering three days with different weather conditions, with particular reference to the CSP plant of the Ottana Solar Facility (currently under construction in the industrial district of Ottana, Sardinia, Italy). The results of this study show that partial recirculation of the solar field does not allow performance improvement of the CSP plant. Moreover, bypassing the cold tank in the recirculation path avoids a strong deterioration in performance. Differences between recirculation strategies become subtler for clear-sky days and, therefore, the present results can be very useful for improving the CSP performance, especially during mostly cloudy days.