Introducing a dimensionless number as tank selector in hybrid solar thermal energy storage systems

Using hybrid energy storage system is a method for increasing the storage capability of solar thermal energy. If multiple energy storage devices with complementary performance characteristics are used together, the resulting system will be a ‘Hybrid Energy Storage System’. In other words, a Hybrid Energy Storage System (HESS) has several media available for storage at any time. In this way, increase in storable energy is obtained without increasing collectors’ area. When there are more than one storage mediums, the system should be able to choose the best medium for storing energy according to the conditions. In the previous works, an optimizer program was used to find the proper medium along time. But running a computer optimizer program is almost time consuming. So, in this work, a recognition parameter is introduced which helps to select the proper tank in different conditions. Using this dimensionless parameter, the hybrid storage system won’t be always dependent to the optimizer. The results have been checked theoretically and experimentally.