Storage is essential for making the solar thermal technologies stand-alone. For the time scale of a day for few days, sensible heat storage with low thermal inertia is a reasonable choice which has the advantage of fast kinetics and lower cost compared to the latent heat or thermochemical routes. In an earlier study, it has been demonstrated experimentally that the sensible heat storage can be made more efficient by modularization. However, the real potential of modular heat storage is experienced with high temperature heat with significant temperature variations. Here, we simulate such heat storage processes for realistic solar thermal heat profile and compare the performance of multi-tank modular system with that of conventional single tank system. We find that the roundtrip storage efficiency can be improved by more than double in terms of enthalpy and more than quintuple in terms of exergy for the given heat profiles. Although the exact quantitative enhancement depends on the temperature variability of the input, the methodology of such analysis and design as employed in this study is universally applicable. It is observed that the improvement in terms of exergy is significantly higher than that in terms of enthalpy. Therefore, the real benefit of such modular heat storage systems will be seen in case of high temperature solar power cycles, particularly based on the solar tower technology.