The NSW network hopes a Tesla grid battery will help steady to grid to take more renewables.

One of the problems with replacing predictable forms of generation with unpredictable renewables in the grid is the traditional fleet’s provision of inertia, the steady hand that can counter rapid changes in frequency.

Many engineers in the industry like to stand up at conferences and declare inertia can only be provided by heavy things that spin, and that solar and wind simply can’t provide the service.

New lithium-ion battery technology from Tesla, however, can be operated in “virtual machine mode” to supply synthetic inertia, which puts the clean energy cat among the clay pigeons.

NSW network TransGrid is stepping into new territory by building a 50MW/75MWh facility made up of Tesla Megapacks at its Wallgrove substation in western Sydney to provide fast frequency response and inertia services to the grid. 

Calm down

An increase in renewables is happening “much, much quicker than we’d anticipated”, says TransGrid executive manager of strategy, innovation and technology Eva Hanly, as is the retirement of coal-fired generation. The sticky issue of inertia must be addressed.

“What happens when you reduce the amount of coal-fired generation and increase the amount of renewables is that you have a problem with inertia,” Hanly says. The power system gets the inertia it needs to function effectively from coal, gas and hydro generation, she says. “We needed to find a solution for inertia … solar and wind generation doesn’t provide inertia. This is the sole purpose of this battery.”

Large-scale batteries are expensive, but Hornsdale Power Reserve in South Australia has managed to pay its way by providing services to the grid.

There is a market for inertia, Hanly says, but because the Wallgrove Grid Battery will be the first facility to offer the service it’s not clear enough yet how to value it.

“We are using it for the network, so it’s for the benefit of consumers on the network – but there are elements of the device we are not needing for the network that we are selling into the market, so we are getting market revenue as well [from market participant Infigen Energy]. That makes it much more cost-effective for consumers,”

The battery is co-funded by the NSW and federal governments.

The primary focus for TransGrid, she says, is to provide “secure, safe and reliable” energy on the grid. “We can’t keep having more and more renewable generation connecting to the grid if we can’t solve this inertia problem.”

It must take a bit of bravery to back such new technology. “We’re willing to trial it, but obviously there are all sorts of risk controls in place – we’re going in with our eyes open.”

“We’re proud to be trialling new technology and we’re focused on bringing new technology to Australia. There are a lot of really interesting things happening globally and it’s important that we trial them.”

Storage paves the way

If the trial is a success Hanly says TransGrid will be looking to rollout large-scale storage on the network. “The sooner we can do it and maintain safe, reliable and secure power, the more renewable generators can connect. It’s a really important step in the transition of the energy system and will give us a lot of the information and data we need to accelerate the storage available.

“The last thing we want is for there to be a lot of investment demand in renewable energy but there not being enough secure and reliable technologies like batteries, which slows it down.”

The project is backed with $11.5 in grant funding from the Australian Renewable Energy Agency and $10 million in funding from the NSW government, as part of its $75 million Emerging Energy Program. Once built, the $61.9 million Wallgrove Grid Battery will be dispatched by Infigen Energy, who will trade the battery in the wholesale market and frequency control ancillary services (FCAS) markets. 

ARENA chief executive Darren Miller said the project has the potential to demonstrate the technical capability of batteries to substitute traditional inertia. “In doing so, TransGrid will demonstrate that batteries can provide the most cost-effective solution for NSW’s projected upcoming inertia shortfall,” he said. “Large-scale batteries have a big role to play in firming and balancing our electricity system.”