Interruptibility: how it works and the financial rewards for businesses

Help the grid tackle emergencies and make money in the process. An opportunity now available to businesses through the interruptibility service

Published on 1 October 2020

Interruptibility as a revenue stream for businesses and to make the grid secure

The global growth in demand for energy, the intensifying use of renewables, the decentralisation of generation and extreme climate events related to global warming, all pose increasing threats to a regular supply of electricity. The result is that Transmission System Operators (TSOs) are having to tackle rising instability and a growing potential for outages for their users. To limit the impact and guarantee that consumption of energy and input to the grid are in balance, TSOs are using a series of services to allow their clients to make available to the grid, in exchange for payment, the flexibility they have in consuming and generating power.

The interruptibility service: how it works

These services, which are provided directly by the TSO, include interruptibility. This is a defence programme for the national grid which, in exchange for a fee that is decided in an auction, allows the interruption of electricity loads specified by the user who is taking part.     

Interruptibility is a practice that is widespread around the world and which helps to prevent electricity supply outages and blackouts.

Interruptability in Italy

In Italy, the interruptibility service is one of the tools that Terna uses to ensure that the electricity system operates safely. When necessary, using its remote control network the operator of the national grid acts directly on switches at electricity production sites connected to the medium- to high-tension grid with an average monthly power equal to or in excess of 1 MW per site, whose owners have signed up for the interruptibility service. Terna will pay the service provider for every MW of interruptible power made available on the basis of the monthly consumption of the interruptible loads. The payment is made up of a total figure comprising a fixed fee (for making the service available) and a variable fee (for every interruption with a positive outcome).  

Instantaneous interruptibility

By instantaneous interruptibility, the National Grid Operator (Terna) means that load disconnection (switches opened) must occur within 200 milliseconds of the receipt of the interruption command sent by the operator using communications channels dedicated to this specific service. 

For the three-year period 2018-2020, the national electricity grid requirement was fixed at a maximum amount of interruptible power of 4,600 MW, consisting of 200 MW for Sicily, 400 for Sardinia, and 4,000 for the rest of the country. For 2020, the requirement on the mainland was fixed at 4,300 MW, taking the overall requirement up to 4,900 MW.

Instantaneous interruptibility service auctions  

The offers made by the businesses interested in the programme are  selected every three years via a marginal-price auction in addition to others on an annual, interim and monthly basis if all of the power has not been assigned or if more is required. These start from a unit price on an annual basis (known as the “reserve price premium”) of 105,000 euro per MW per year for the instantaneous interruptibility service for the Mainland Area and 126,000 euro per MW per year for the Sicily Area and the Sardinia Area.  

Companies belonging to the same group as the assignee may transfer some or all of the interruptibility service between them as long as it involves whole MW values and meets the same requirements.   

All end clients that own points from which power can be taken, can participate in the interruptibility service auction either individually or as a consortium, so long as they comply with the technical requirements. These are set out in in the Terna Grid Code and regard connection with the Interruptible Control Desk; holding the requisite eligibility certificates; and having total available interruptible power of no less than 1 MW per individual site. To participate, interested businesses must also specify the amount of power in MW that they intend to make available for instantaneous interruption.

The Enel X service

Enel X offers businesses the possibility of participating in the interruptibility programme  either individually or in aggregate form through a business consortium. Participating through a business consortium offers numerous benefits including power allocation optimisation for the individual members of the consortium, greater flexibility and reduced risks.

The Enel X service is open to all commercial and industrial clients from all sectors. They should have high- or medium-voltage grid connections with an annual electricity consumption rate of over 7.5 Gwh. The service provides access to a new revenue stream, with a fixed fee for the maximum amount of power made available for interruption, plus a variable fee linked to the number of verified positive interruptions made.

The interruptibility programme is just one of the flexibility solutions that Enel X is making available to its business clients through its e-Industries business line.

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