One feature of every electricity system is the need to guarantee a constant real-time balance between the energy demanded by consumers (households and businesses) and the energy generated by power plants. A system is considered adequate when it has sufficient levels of resources for production, storage, flexibility (such as consumers who are able to voluntarily reduce their load) and transport capacity to meet the expected electricity demand at all times, including a reserve to be able to cope with errors in forecast electricity demand and production (e.g. from renewable sources) and the consequences of possible grid failures and events (such as the opening of a line or a production plant failure).
“Adequacy” refers to the system’s capacity to meet electrical energy requirements while complying with safety and service quality requirements.
An electricity system is considered adequate if it has sufficient generation, storage, demand control and transport capacity resources to meet the expected electricity demand with a reasonable level of confidence.
How to measure it. One of the main indicators for measuring the adequacy (or inadequacy) of an electricity system is known as LOLE (“Loss of Load Expectation”) and represents the total number of hours per year when a switch-off of part of the consumers is likely because the expected demand exceeds the resources available to satisfy it. This indicator has been adopted as an index to measure adequacy at both European and Italian level.
The Italian electricity system is adequate when there are no more than 3 hours LOLE. This means that there is 0.03% probability that at least one consumer (but not necessarily all consumers) will be disconnected from the network due to adequacy. The adequacy assessment is carried out by means of a probabilistic analysis to take into account the variations (random or not) of the main factors, including climate events such as temperature, wind conditions or solar radiation.
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How to measure the capacity required for the system. The demand for generation capacity required to guarantee adequacy is measured in terms of Capacity Available in Probability (CDP in Italian). To the same end, the supply of electricity system capacity should also be measured in CDP, calculated using specific de-rating levels that take into account the effective availability of a specific technology (conventional thermal, non-programmable renewable, storage and flexible demand), thus considering the status and uncertainties of all the various characteristic elements of the electricity system. To date, for example, for around 115-116 GW of installed generation capacity, in the winter period approximately 54-57 GW are available to meet the peaks in demand.
Terna’s Adequacy Report for Italy. Every so often, as the operator of the national transmission grid, Terna checks the adequacy conditions of the Italian electricity system over the medium to long term, updating the analyses based on the most recent methodologies and forecast scenarios. The same analyses are also aligned with the current legislative and regulatory context.