The Northern Territory Labor has awarded the contract for the Darwin big battery to Hitachi Energy, in what is expected to be a major step towards eliminating fossil fuels and operating the local grid with solar only, at least in daytime hours.
The $45 million Darwin-Katherine Battery Energy Storage System (DK BESS) is considered essential to handle the growing amounts of solar in the local grid, particularly rooftop installations, and is crucial to reducing the dependence on gas generation.
The NT government has a target of 50 per cent renewables by 2030, but because there is little in the way of wind, or hydro resources in the territory, this renewable generation will have to be delivered with solar. And it means that solar will need to deliver all, or nearly all, of the daytime electricity needs.
To achieve that outcome, and not have gas generators running in the back-ground, requires hi-spec battery storage inverter technology that can operate in “grid forming mode” or as “virtual synchronous machines”.
The Hitachi battery will have this capability – as others already do in the Australia’s main grid – but it means that with another one or two similarly capable batteries, the Darwin-Katherine grid will be the first of its size in the world to operate on solar alone, with batteries rather than fossil fuels in support.
“The awarding of the BESS tender is a huge step forward in our plan for 50% renewables by 2030 – it is the cornerstone of our Darwin–Katherine System Plan,” the minister for renewables and energy Eva Lawler said in a statement.
The 35MVA (megavolt amps) DK Bess is expected to deliver savings of $9.8 million a year because less gas will be used in the system.
That delivers a payback of less than five years – similar to the paybacks being achieved at Mt Newman in the Pilbara, and which is expected of Tom Price, where Hitachi is also building a battery.
“We’ve backed renewables and so have Territorians – they know renewables deliver cleaner, cheaper and secure power,” chief minister Michael Gunner said.
“The cutting-edge technology in our Battery Energy Storage System will reinforce the Northern Territory as the solar capital and comeback capital of Australia. The BESS will store power and be the backbone of the Darwin to Katherine Electricity grid which keeps the lights on for 150,000 Territorians.
Hitachi Energy’s country manager in Australia, Bernard Norton, said the DK Bess will ensure full utilisation of solar energy generation and less reliance on fossil fuels.
“This battery energy storage system will allow greater penetration of renewable energy in the Territory, helping to ensure a sustainable, flexible and secure energy system for today’s generations and those to come,” he said.
But the reality is that the battery lays the path to go beyond reducing the reliance of gas generators, to eliminating gas generation during the day, and leading the path to a 100 per cent renewables grid.
Hitachi’e Stephen Sproull says the “grid forming BESS” is needed to “form” the grid during minimum demand and allow the system to run on just solar during the day.
“Without these grid forming BESS, this isn’t possible,” Sproul told RenewEconomy.
“This technology unlocks the last mile of renewables and, without it or synchronous condensers, you need to keep a minimum number of thermal generation online. We saw how the installation of synchronous condensers in SA unlocked more renewables and it is the same with grid forming BESS in the NT.”
The Darwin-Katherine grid currently sees “minimum” demand – the amount of demand in the grid less the supply from behind the metre and rooftop solar installations – fall to around 80MW. The system has an average load of around 200MW and a peak of around 300MW.
This Hitachi battery will cover about half of that minimum demand need, and will allow one of the gas generators at the Channel Island Power Station that usually operates in case of an emergency.
“Having two or three of these high spec, grid-forming batteries will allow the grid to run on PV during the day with no synchronous machines or thermal generation online.
“This grid forming BESS is not just supporting renewables to connect, it is underpinning the operation of the grid and allowing 100% renewables to operate and provide the electricity needed.”
The 35MVA battery rating speaks to its capabilities as a “virtual synchronous machine”. It’s other ratings are 34.7MW and 34.7MWh, or one hour of storage, which is longer than the original specifications for the battery.
That means that apart from the “grid-forming” capability, it will allow for “some smoothing and some shifting as well”, according to Juergen Zimmerman, the technical manager for Hitachi Energy in the Darwin area.
The battery will be online continuously, replacing one gas-fired generating unit. Inertia from the battery will increase stability and reliability of the power supply. Fluctuations caused by the intermittency of solar energy can be managed quickly and efficiently.
The graph above – a Hitachi adaptation of the NT government’s renewables roadmap – illustrates how the battery system may change the thinking around the local grid.
Batteries will time shift some solar power to the evening, but currently, it is assumed that some thermal generation will be required during the day to maintain grid security. But if grid security is delivered by grid forming batteries, then the thermal generators can be switched off.
The DK Battery will start construction in early 2022, and be complete by 2023.
“The Darwin-Katherine battery is a cornerstone of Territory Generation’s Fleet Transition,” said Territory Generation CEO Gerhard Laubscher. “It is key to unlocking flexibility in our fleet to better manage the increasing impacts of solar on the system.”