Electricity storage: centralised or distributed?


Energy storage is a promising, growing industry in which the Enel Group is investing and experimenting, assessing the impact of a range of different technologies on the distribution network. Enel is combining storage systems with wind farms and PV solar power plants, while also operating centralised storage systems connected to the distribution network.

Enel has developed three of the former type of storage project in Sicily, two near Palermo and one in Catania, while Endesa has put into service three storage plants of the same type in the Canary Islands as part of the STORE project. The latter project sees the use of lithium-ion batteries, flywheel batteries and 4MW/20MW ultra-condensers, and aims to resolve the energy issues of an island where stability of the network largely depends on renewable generation.          

Strorage systems built in renewable energyplants can help compensate for forecasting errors and maximise installed generation capacity by storing the energy produced at peak time and avoiding network overload.

When applied on a large scale, this technology helps to keep the plant functioning whenever a single part breaks down, and delocalised accumulation systems can stop failures from creating serious problems for domestic distribution.

Enel also operates centralised storage systems, which are larger and connected to the distribution grid. These systems require sound technical and financial management, as well as a solid interface with the domestic supply and distribution system. Thanks to its considerable size, this type of system can modulate large amounts of electricity, thus helping to integrate intermittent renewable energy sources onto the grid.

This type of system is being used for two projects in Italy, one in Isernia and another, similar but with greater capacity (1 MVA -1 MWh) in the area of Forlì-Cesena, which is part of the Grid4EU project. The Bari and Cosenza storage systems are part of the Res Novae project and installed along the low-voltage network, while the Interregional Operational Plan, with plants in Catanzaro, Catania and Lecce, is an example of primary station storage.