Demand Side Management (DSM)

Demand Side Management involves users of electricity having the capability to change their usage from their normal or current consumption patterns. It can provide significant benefits for customers in terms of reduced bills and gives them greater control over the energy they use and produce. 

It can help EirGrid in managing the power system efficiently; including accommodating increased renewable electricity generation and providing enhanced capacity. Demand Side Management has been and is expected to remain a key operational service to maintain system security for the island and we support the development of a smart grid where Demand Side Management is an important element.

Electricity consumers can currently participate in Demand Side Management through tariff-based schemes where they are encouraged to move their usage to cheaper off-peak times. Examples include Economy 7 (Northern Ireland) and NightSaver (Ireland). EirGrid also operates two system operator-based schemes in Ireland, Short Term Active Response (STAR) and Powersave, which are used to keep the system secure at times when the system is stressed. These schemes are aimed at large electricity users.

In addition to customers individually participating in the schemes operated by EirGrid, medium to large electricity users can participate in a Demand Side Unit (DSU) or Aggregated Generating Unit (AGU). A Demand Side Unit consists of one or more demand sites that can reduce their demand when instructed by EirGrid or SONI.  The Demand Side Unit has one hour to reduce its demand and must be capable of maintaining the demand reduction for at least two hours. 

The Demand Side Unit, usually third-party company specialising in demand side management, may contract with a number of demand sites and aggregate them together to operate as a single Demand Side Unit. Instructions to reduce demand are issued to the Demand Side Unit by EirGrid or SONI at an aggregate level and the Demand Side Unit then co-ordinates the reduction from all its demand sites. Demand sites typically use on-site generation, plant shutdown or storage technology to deliver the demand reduction.  An Aggregated Generating Unit is similar to a Demand Side Unit, a key difference being it is composed of on-site generation only.

Demand Side Unit (DSU)

A Demand Side Unit (DSU) consists of one or more Individual Demand Sites that can be dispatched by the Transmission System Operator (TSO) as if it was a generator. An Individual Demand Site is typically a medium to large industrial premises. A DSU Aggregator may contract with the Individual Demand Sites and aggregate them together to operate as a single DSU. The DSU Aggregator is a third party company specialising in demand side participation. Dispatch instructions are issued by the TSO at an aggregate level and the DSU Aggregator then coordinates the reduction from the Individual Demand Sites. The Individual Demand Sites use a combination of on-site generation and plant shutdown to deliver the demand reduction. By being available for dispatch the DSU will be eligible for Capacity Payments in the Single Electricity Market (SEM).

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A Demand Side Unit (DSU) is a demand site that can be instructed by EirGrid to reduce electricity demand. Instructions to reduce electricity demand are called dispatch instructions. Where a DSU consists of more than one individual demand site it is called an aggregated DSU. A DSU uses a combination of on-site generation and/or plant shutdown to deliver a demand reduction in response to an instruction from EirGrid.

DSUs that are available for demand reduction are eligible for a capacity payment in the Single Electricity Market (SEM). More information on the capacity payment mechanism in the SEM is available on the SEMO website.

Demand sites, with or without a Maximum Export Capacity (MEC), may be eligible to register as part of a DSU. A DSU must have a demand reduction capacity of at least 4MW. The maximum demand reduction capacity of an individual demand site in an aggregated DSU is 10MW. Demand sites with greater than 10MW demand reduction capacity may register as a stand-alone DSU.

The company registering the DSU, called the DSU aggregator, must be a licensed supplier and registered as a supplier in the SEM. It is not required to be the supplier of the individual demand sites. Information on becoming a licensed supplier can be found here.

To become a DSU an application must be made to both EirGrid and the Single Electricity Market Operator (SEMO). The application to EirGrid can be made using the approved application form with all relevant documentation included. Information on the SEMO application process can be found here.

EirGrid requires real-time communications with the DSU to ensure secure power system operation and to issue dispatch instructions to balance generation and demand. A signal list is provided to the DSU when their application is finalised, so that the DSU can configure their control system to provide these signals. Dispatch instructions are issued by EirGrid via the Electronic Dispatch Instruction Logger (EDIL) that is accessed through a website. The method of communication installed between the individual demand sites and the DSU must be agreed with EirGrid in advance.

A DSU is required by EirGrid to be available 24 hours a day, year-round, unless an outage is agreed with EirGrid or if breakdown forces the unit to become unavailable. When the DSU is required it will be issued dispatch instructions specifying the amount of demand reduction required. Dispatch instructions are issued by EirGrid (via EDIL) at an aggregate level and the DSU aggregator then coordinates the reduction from the individual demand sites.

A DSU is required to demonstrate Grid Code compliance before they become commercially operational. This is achieved through a number of Grid Code tests that will be witnessed by EirGrid. EirGrid may also require testing as part of on-going Grid Code performance monitoring when the unit is commercially operational.