The present work deals with the thermodynamic analysis of four different integration schemes for a packed bed thermal energy storage in a Stirling - CSP system. Simplified models for the different systems' configurations have been developed and analyzed in steady and transient working conditions. Particularly, a parallel and serial connection between the power and the storage unit have been compared, showing a trade-off between the contemporaneity of power production and storage and the usefulness of the storage itself accordingly to the working temperature constraints for the power unit. It is shown that a closed parallel system configuration is the most promising solution as it allows for a longer production during night time and an higher net energy production, it is therefore worth of further investigations.