The Northern Territory government has called for expressions of interest to build what could be the world’s second biggest big battery – a large-scale energy storage system of between 25-45MW to support the grid in Darwin and Katherine.

The document, issued last week by Territory Generation, calls for design parameters of 25MW, 35MW, and 45MW power outputs, with an energy storage of 30 minutes — and alternatives of up to an extra hour — at the rated capacity.

According to an ABC News report, the tender document says that the battery would need to be able to supply power during periods of large solar PV capacity loss, such as on cloudy days.

In particular, it would be used to balance supply from large-scale solar farms connected to the Darwin-Katherine power network, as well as from rooftop solar – the installed capacity of which are expected to increase as the Territory transitions its electricity network to 50 per cent renewable energy by 2050.

As we reported here, the NT government in late November endorsed an 86-page Roadmap to Renewables Report it had commissioned back in 2016.

The roadmap charts a slow, and cautious route to take the Territory’s three grids, currently 96 per cent powered by gas and diesel generation, to an installed total of 450MW renewables, from just over 36MW today.

As part of its endorsement, the NT government pledged to provide $750,000 to the Territory-owned utility, Power Water, to develop “a dynamic system model” to integrate increasing levels of renewable energy into the grid in a stable and predictable way.

It has also pledged to spend $4.5 million on household grants of up to $1000 to encourage rooftop solar uptake – currently installed on just 6 per cent of households, compared to 14 per cent on average.

Once the successful bid is selected, NT battery system stands to be the second largest in the world if built with a capacity of more than 30MW. The largest, of course, is the 100MW Big Battery built by Tesla alongside Neoen’s Hornsdale wind farm in South Australia.

As for the contenders to develop the NT battery project, there appears to have been no shortage of interest.

The NT government tender page lists an impressive number of prospective tenderers, including Tesla, ABB, BYD and Siemens.

The tender closes in just over one week, on January 22.