S is for Storage

Storage systems are systems that convert electricity into a form of energy that can be stored, storing it in this state and enabling it to be converted back into electricity and finally used by the end user. There are many storage technologies but two in particular are best known and most widely used. The first is hydroelectric pumping systems, which use well-established technology and are suitable for prolonged use thanks to the high storage capacity (in the order of weeks, depending on the capacity of the reservoirs). The second is electrochemical storage systems. These are particularly interesting as they can be programmed and are very responsive, and have become established on the market on recent years due to increasingly cost-effective prices and the development of electric mobility.

To achieve the ambitious decarbonisation targets set to be reached by 2030, it is essential to further increase the amount of electricity produced from renewable energy sources. To this end, Terna (the Italian national transmission grid operator) has developed a strategy structured into a series of very precise measures, with storage systems playing a crucial role. In particular:

* the development of electricity infrastructure able to transport electricity from areas where there is more renewable energy generation to areas with higher consumption;

* the optimisation of cross-border interconnections;

* the evolution of the so-called "market design" able to promote the integration of new resources and provide the right pricing indications;

* the development of new energy storage systems.

Storage systems offer several benefits to the electricity transmission grid:

1. First of all, they reduce phenomena like over-generation and grid congestion because they store the energy produced from renewables - which is not necessarily produced at a given time of day or night - and avoid the curtailment of production from these sources.

2. Furthermore, the supply of electricity when demand is highest and/or when production from renewables is low, such as during the evening ramp, can significantly contribute to the adequacy of the electricity system.

3. Finally, the supply of advanced grid services, which vary depending on the storage systems, helps to guarantee the safe operation of the grid.

Terna has recognised the potential intrinsic value of electrochemical storage in 2012 and has been researching the topic through two pilot projects launched with the support of the Italian Regulatory Authority for Energy, Networks and Environment (ARERA):

1. Storage Lab (or Power Intensive project), aimed at testing the performance of different electrochemical storage technologies to support safe grid management in Sicily and Sardinia, through the installation sites at Ciminna (Palermo) and Codrongianos (Sassari);

2. Large Scale Energy storage (or Energy Intensive project), developed in Campania (Flumeri, Ginestra, Scampitella) with the aim of assessing to what extent energy storage can reduce grid congestion on sections of the 150 kV grid caused by the excessive integration of non-programmable renewable sources in Southern Italy.

The results of the trials conducted by Terna have enabled the performance of storage systems to be put to the test in the field, identifying innovative services to support dispatching activities. With further development, they will also lead to the development of greater technological know-how and innovative solutions for the optimal integration of storage systems on the grid and on the market.