Rio Tinto battery to be biggest of its type in world, and shine path to 100 pct renewables

A 45MW big battery now under construction for mining giant Rio Tinto’s massive iron ore operations in Western Australia will be the biggest of its type in the world, and will give valuable insight into how the country’s main grid can also manage the switch to wind, solar and storage.

The battery at Tom Price in the Pilbara will have little more than 15 minutes of storage, or just 12MWh, but it is the ability to operate as a “virtual synchronous machine” (VSM), also known as a “grid forming inverter”, that is the key to this project.

The importance of this technology is that it allows the operators of the private network to switch off expensive and highly polluting gas turbines they currently use as a constant back up for their existing fossil fuel generators.

The battery will be able to control the grid and hold it steady by itself if needed. This, in turn, is a key step to designing battery inverters and software that can support a 100 per cent renewable grid.

The Tom Price battery will not be the first of its type in Australia – several have already been installed, including at nearby Mt Newman (35MW, 12MWh) and at Dalrymple North in South Australia (30MW, 8MWh), and two others are being built by Fortescue Mines in the private network that powers its iron ore projects.

But according to Stephen Sproull, a senior engineer at Hitachi ABB, the 45MW, 12MWh Tom Price battery will be the biggest of its type in Australia, and the biggest battery in the world that is not connected to a national interconnected grid.

Its significance, however, is not so much in its size, but what it means for the future of much bigger grids such as Australia’s National Electricity Market.

“The aim is to switch off synchronous machines such as gas turbines today, but also lay the technical foundation to operate with no synchronous generators in the future and source all electricity from renewables,” Sproull told RenewEconomy in an interview.

“It’s important to demystify the technology, and make it clear that we have the technology to provide the essential grid services and get to 100 per cent renewables.”

As we have reported, the Mt Newman battery – which is operated by Alinta on the private network that serves huge iron ore mines owned by Gina Rinehart’s Roy Hill and Andrew Forrest’s Fortescue – is proving to be an economic success, and is boosting reliability by stepping in to fix any problems with the gas turbines.

In these sorts of grid gas – or diesel power – is supplied by multiple turbines. Two or three might be producing the electricity needed to meet demand, but fossil fuel turbines need back up, and another one or two must keep spinning, and burning, fuel, 24 hours a day, 365 days a year in case of an incident.

A battery like that at Mt Newman allows the back-up turbines to be switched off, delivering big savings on fuel costs and emissions, and improved reliability, as it can also provide grid services, and hold the grid together if a problem emerges so the back-up generators can then be switched on.

That’s why the batteries used in these applications only need a short amount of storage, 15 or 20 minutes. But the key lies in the software which differentiates a “grid forming inverter” from a “virtual synchronous machine.”

Sproull says grid forming inverters are unlike normal inverters because rather than just following the frequency and voltage wave forms of the grid, they can create their own frequency and voltage wage forms.

They are often used on small, off grid installations. But the virtual synchronous machine software that overlays these grid forming inverters teaches them how to behave with the rest of the grid, and to interact with other technologies and installations.

“Instead of just running their own race, and fighting other installations, it acts as a bit of a shock absorber so it can provide a holistic and unified response,” Sproull says.

This is crucial for a future grid without synchronous generators, because it means that batteries can control the system and work together.

And it is the big mining groups – because the technology already stacks up commercially on the smaller networks that they operate – that are showing the path to 100 per cent renewables.

“It’s quite a compelling business case,” Sproull says, noting Alinta’s observations of a rapid payback from its Mt Newman battery.

“This is the technology they need to switch off synchronous generation. It also means we are solving technical challenges up front, before adding renewables, and not hitting the system strength or grid stability problems being encountered elsewhere.”

This is just the latest in a series of important technical achievements that have been achieved in recent times, including the “re-tuning” of solar inverters in north Queensland that has successfully resolved “system strength” issues in the region without turning to synchronous machines, and at a fraction of the cost.

Rio Tinto is adding a 34MW solar farm to its network, to help power the expansion of its iron ore mining operations. Alinta is now completing the 60MW Chichester solar farm that will help power Fortescue mines, while Fortescue itself is to install up to 150MW of solar, and two big batteries in its network.

The Fortescue batteries, like those at Mt Newman and Tom Price, will also be “virtual synchronous machines” and will be installed at two different mine locations in that network. They will be sized with short duration storage at 30MW/8MWh and 20MW/5MWh.

Alinta has also unveiled plans for a four-hour big battery to support a 90MW solar farm and improve the efficiency of its gas generators on the Karratha-Port Hedland grid. Importantly, this battery will also be a “virtual synchronous machine” to also allow 100 per cent renewable energy generation.

The Tom Price batteries are being assembled in Perth, using Hitachi ABB inverters and Kokam batteries, before the containers are shipped to the mine site at the end of the year, where it will be installed next to the existing sub-station and integrated into the network (see artist’s image above).

See also RenewEconomy’s map of big battery storage projects in Australia: Big Battery Storage Map of Australia