The rapid increase in electricity generation plants using non-programmable renewable sources (NPRSs) in Italy in recent years has had an increasingly tangible impact on processes for management of electricity flows (dispatching) and the safe operation of the national electricity system in general.
In order to optimise generation from renewable sources and at the same time ensure increased security management margins in the electricity system, Terna has identified energy storage as one of the possible solutions to the problem. This is why Terna has planned the installation of technologies in strategic locations across Italy and connected to the National Electricity Transmission Grid (NTG). This innovative use of storage systems has led Terna to launch an experimental programme aimed at implementing pilot projects designed to test and validate the use of electro-chemical storage at the “utility-scale” level.
The first project, launched by Terna in 2011, is focused on large-scale storage plants, connected to sections of the high-voltage (HV) grid in southern Italy, which are critical due to the high levels of penetration from NPRSs. With the primary focus on reducing congestion volumes, Terna conducted a public tender process leading to the selection of the NAS battery technology (sodium/sulphur) as the most suitable for the purpose. The total storage programme of 35 MW is composed of three plants, each connected to the NTG via a 20/150 kV Electrical Substation. The project operation enables the optimisation of the primary objectives (mitigating congestion from NPRSs) and the effective experimentation with highly innovative grid delivery services (e.g. experimental calibration of the primary regulation and secondary regulation of frequency, development of new and advanced dispatching services, etc.).
More experimental in nature and structured like a true energy storage laboratory, the second project (Storage Lab) was launched in 2012, and consists of 16 MW of multi-technology storage systems, aimed at increasing the safety margins of the HV networks on Italy’s two largest islands (Sicily and Sardinia). With 13.4 MW total capacity already installed (21.2 MWh storage capacity), the Storage Lab project is the only one of its kind in the world in terms of the variety of available technologies and the innovative nature of the control systems. The individual storage units are lithium (9.2 MW, 5 types), Sodium Nickel-Chloride (3.4 MW, 2 types) and vanadium redox flow (0.85 MW, 2 types) based. To complement the existing technological portfolio, Terna also plans to install super-capacitor systems in the near future. With the Storage Lab project, Terna is able to experiment with the main storage technologies currently available on the market and test their performance in terms of supporting essential conventional services such as primary frequency regulation, secondary frequency regulation and Defence System easement.
The outcome of the experiments conducted by Terna will help us to place an emphasis on technological development in the sector and accelerate the integration of such resources in the dispatching service markets as well as in the national electricity system in general.