Hybrid storage system looks to Ireland's services market

IRELAND: The pilot of a 576kW grid storage system using flywheels and batteries by Dublin-based Schwungrad Energie is looking to pave the way for the technology's deployment in Ireland's ancillary grid services market.

Flywheel technology was provided by US firm Beacon Power

Schwungrad Energie intends to develop a commercial-scale hybrid storage plant for Ireland's DS3 System Services market, comprising a 20MW/10MWh flywheel and lead-acid battery system, able to provide 5-20 minutes of power at full output.

The demonstration project, carried out in conjunction with transmission system operator EirGrid, has been operational since the beginning of the year and will conclude this month.

Results of the pilot in Rhode, east Ireland, show that the hybrid flywheel and battery plant meets Schwungrad's set of requirements for response time and power-output sustainability.

Combining a battery and a flywheel enables the storage system as a whole to operate more efficiently and reduce operational costs over the system's lifetime. Batteries degrade through cycling. Flywheels do not.

By addressing some of the high power events in a grid with flywheels, the batteries do not need to be cycled as much. However, flywheel storage technology, generally, is limited by how much energy can be stored.

"Hybrid storage systems overcome the limitations of each individual storage technology, so that you can provide a wider range of different services, which vary grid by grid," said Schwungrad technical director Frank Burke.

In the pilot project, two 160kW/30kWh flywheels have been supplied by US company Beacon Power, while Hitachi Chemical supplied the 160kW lead acid battery.

The start-up intends to participate in the qualification trial process for EirGrid's DS3 system service market.

If it is successful in the trial, Schwungrad will bid into the DS3 system auction with the 20MW scaled-up project.

The service market is a core part of a programme EirGrid is undertaking to reform the electricity systems of Ireland and Northern Ireland as more renewable generation, especially wind power, is added.

The complexity of the new grid services market's design, which pays out for various different services ranging from fast frequency regulation, to renewables ramping and voltage control, has led to a delay in its implementation to October 2018, with the first auction taking place in the first half of 2018.

"EirGrid has designed an ambitious market, which caters to every type of service that can be offered. This has resulted in a highly complex auction, which has led to delays in its implementation," said Burke.

In March 2016 the Single Energy Market (SEM) Committee, which acts as the decision-making authority on the single electricity market of Ireland and Northern Island, confirmed delays to the auction, following a consultation period where it was decided that further engagement with industry was required ahead of DS3's implementation.

Commercial-scale hybrid storage plant

The main service Schwungrad's hybrid storage system will provide is fast frequency response.

The system will need to respond in two seconds in order to correct grid imbalances, with even faster response times, coming in at a second or under, paid more under a multiplier rate.

"This type of fast frequency response is valued more in the grids of Ireland and Northern Ireland than in other grids in Europe. Mainland grid systems tend to be more interconnected, so there is more inertia in their systems. Ireland's grid is facing problems ahead of many of the mainland European grids," Burke said.

Schwungrad's intellectual property originates from its software controls that manage the operation of storage technologies as a hybrid.

"There is complexity in maintaining the hybrid system at an optimum state-of-charge in order to maximise the capability to deliver services. The delivery of power also requires accurate control to ensure that the grid receives a sufficient quantity over a specific time period," added Burke.