We are in a historical period for humanity in which the energy transition plays a fundamental role in future perspective. The aim is to decrease climate change and air pollution by reducing our dependence on fossil fuels. As well known, the main solution is the integration of renewable sources in the countries energy mix but is also known the weak point of RES that is the intermittence in energy supplying due to natural conditions. For these reasons, the storage of energy comes to help with playing a very big role in power systems. In order to integrate more RES in the countries’ energy mix maintaining stability and reliability of energy supply, the EES (electrical energy storage) is crucial indeed.