This paper presents the effect of finned multitube shell and tube latent heat thermal energy storage system (LHTES) on the dynamic performance of the Rankine cycle based solar thermal power plant. A widely available phase change material (PCM), sodium nitrate is kept in the shell side. As PCM and HTF have low thermal conductivities, fins are attached on the inner and outer surfaces of the HTF tubes. A simplified thermal resistance network-based energy equation coupled with the enthalpy technique, is developed for analysing heat transfer in the LHTES. The effects of number of fins (N-p = 12, 24, 36 and 48) and fin thickness (t(f) = 1, 2, 3 and 4 mm) on the PCM side of LHTES on the overall performance of the solar power plant for generating electricity after sunset are investigated for an Indian condition on cloudy days. The addition of fins in LHTES is found to reduce the time for continuous power generation. The marginal changes in melt fraction of PCM and turbine output power are found for the number of fins and fin thickness greater than 36 and 2 mm, respectively. The maximum discharge efficiency occurs at the number of fins of 48. (c) 2019 Elsevier Ltd. All rights reserved.