Broken Hill battery charges up to create local micro-grid, but why was it disabled in the first place?

The Broken Hill big battery has finally been charged up, helping to bring stability to the local electricity supply and create a more resilient local micro-grid – but the question remains about why the facility was disabled in the first place.

As Renew Economy reported on Friday, the 50 MW, 50 MWh battery had not operated since the Broken Hill region was isolated from the rest of the grid after storms tore down seven transmission towers just after midnight on July 17.

Transmission company Transgrid said on Saturday that it had finally reached agreement with the battery owner AGL for the asset to be switched, 10 days after thousands of homes and business in the local community had started to suffer extensive outages.

On Saturday and Sunday, the battery charged up from the local excess rooftop solar and was standing by to help during the evening demand peaks, and will continue to do so until all the replacement towers are completed on about November 6.

“AGL’s Broken Hill battery … is successfully being charged by power from the grid and will be used to increase stability of power supply for local communities while the storm-damaged transmission line is reconstructed,” Transgrid said in a statement.

“The grid-scale battery will provide additional power to supplement supply and reduce reliance on the large-scale backup generator,” it said in reference to the one diesel generator still in operation and which had suffered multiple trips as the result of demand and supply volatility, heat issues and a failed fuel pump.

The battery reportedly did what it was supposed to do on Sunday evening, helping to alleviate the stress on the grid – particularly in the evening peak.

The single diesel generator is rated at 25 MW but can only produce around 14 MW due to various limitations and Transgrid and Essential Energy have had to rush in a number of small diesel generators to support the grid, and rooftop PV has had to be limited.

The 200 MW Silverton wind farm and the 53 MW Broken Hill solar farm are sitting idle. Their owner, Tilt Renewables, says they are not damaged but cannot generate under their connection rules in such circumstances. That would be different if the battery was operating as it could, or even should.

The AGL website boasts that the Broken Hill battery can – with the grid-forming inverters funded by the Australian Renewable Energy Agency – “support the reliable supply of electricity to Broken Hill in the event of line failure and provide efficient grid support for the region.”

Clearly, it didn’t do that when the line failed in the storm and it now emerges (thanks to the sharp eyes of a Renew Economy reader) that its ability to create mini grid in such circumstances had been deliberately disabled.

An AGL report into the battery’s system strength capabilities, published under the Knowledge Sharing requirements of ARENA funding, reveals that Transgrid had required the battery to include an “anti-islanding” scheme, meaning that its ability to provide the islanding service had been deliberately inhibited.

“It had been hoped that the Broken Hill Battery could be used to supply the Broken Hill load in the event of supply from the grid not being available due to faults or maintenance outages,” the report says.

“This service had previously been provided by Essential Energy using two 25MW GTs (gas turbines) running on diesel.

“When Essential Energy decided that it no longer wished to provide this service, AGL offered to configure the battery to operate in island mode in conjunction with the Broken Hill solar farm, Silverton wind farm and the existing GTs which they had an option to purchase.

“Transgrid ran a RIT-T process to select its preferred provider of standby supply for Broken Hill and chose a compressed air storage alternative. As a consequence, and to avoid adverse interaction between the battery and the compressed air system, the battery has been configured under Transgrid guidance to include an anti-islanding scheme.

“The battery provider is still contracted to include islanding functionality, but this functionality will be inhibited to avoid interaction with the compressed air scheme.”

The compressed air storage project that AGL is referring to is the 200 MW, 1600 MWh facility planned by Canada’s Hydrostor at the site of a cavern in one of the underground silver mines that has made the region famous.

But that project – which has also won an underwriting agreement from the NSW government in a long duration storage tender – will not be built for several years, with a target date of 2027 at the earlier.

And it is not clear why Transgrid required AGL to disable the “islanding” capabilities of the battery, particularly given the ageing nature of the diesel generators that are to be replaced, one of which is completely out of action, and the other only able to operate at just over half of its capacity due to various limitations.

The AGL report appears to make clear that the battery would have been able to support the huge wind farm and large solar farm that are located near Broken Hill, and allow them to generate and provide power to the locals, including the mines that have been forced to down tools.

It has runs on the board in this regard, having successfully operated the Dalrymple North battery in South Australia, which is capable of supporting a micro-grid on the Yorke Peninsula – with the help of the nearby Wattle Creek wind farm – should the lines to the rest of the grid go down.

Both the Silverton wind farm and the Broken Hill solar farm have not been operating since the transmission line went down 10 days ago. But clearly, given the AGL report, they could have been providing power if the battery was properly enabled.

Renew Economy has reached out to all concerned – Transgrid, AGL and the state government – on why the battery was disabled before the compressed air facility was built, particularly given the erratic past performance of the ageing diesel generators – but has yet to receive a reply on that front.

See also: Broken Hill has a wind farm, a solar farm and a big battery. So, why are the lights out?

And: Agreement finally reached to switch on Broken Hill battery, nearly 10 days after storm blows down power lines