Energy storage systems become more important due to development of renewable energy sources (RES). The first step of effective cooperation of RES with fossil fuel power stations, in meaning of carbon dioxide emission reduction, is to give the priority of energy generation to RES. Hereby, thermal power plants become power reserve for stable operation of the energy system. To fallow rapid fluctuation in RES power generation increased flexibility of thermal power plants operation is needed. Fast ramp behavior, fast start-up and low minimal output electric power, while maintaining high energy efficiency, are the main issues in this field. However, in some days total power generation in RES and minimal loaded thermal power plants is higher than energy demand. As a consequence the electric energy must be sold abroad or the RES generation must be decrease. In this situation the second step is needed – the energy storage systems. In power engineering only pumped-storage hydroelectricity are commonly used in term of hourly power reserve. Despite high energy efficiency, this type of energy storage is characterized by high investment costs and requires special terrain topology. The most mature alternative solution is compressed air energy storage (CAES). Though, there are only two full-scale CAES plants worldwide this subject is under intensive development. Proposed paper presents an original solution of CAES based on a gas turbine set coupled with a turboexpander in a hierarchical gas-gas system. Firstly this type of gas thermodynamic cycle differs from the Joule cycle with heat regeneration by higher optimal pressure ratio, which is particularly important while air storage is considered. Secondly gas-gas cycle achieve higher energy efficiency for turbine inlet temperature above 1400 K. Moreover, thermal energy storage is proposed, using phase change materials, to increase round-trip efficiency of energy storage.