Sun Cable still weighing tech options as it lays plans for world’s biggest renewable project

Sun Cable, the developer of what could be the world’s biggest renewable energy project in the Northern Territory, says it is still juggling its technology options as it works towards a final commitment to the $35 billion project.

Sun Cable this week won federal government environmental approval for the first stages of the project, specifically for up to 10 gigawatts (GW) of solar and up to 35 gigawatt hours of battery storage.

It may also, as flagged earlier this week, add wind to the mix and will need to get further approvals from the territory and federal governments for that component. But the scale to which that is added to the mix is likely to depend on technology costs, and for the moment solar and battery storage prices are falling, and wind is not.

“The way I’m approaching is to give ourselves a wide enough envelope of technologies to enable us to essentially supply the lowest cost of renewables,” CEO Cameron Garnsworthy told Renew Economy in an interview on Thursday.

“We are looking at proven technologies of wind, solar and storage, and to be able to mix and match those to ensure that we can supply the cheapest possible price to the customer. In relation to the final sizing, we’re still we’re still working through that.

“As you know, (the price of solar) modules and wind turbines and batteries are all moving around, and we’re not looking to place orders until reaching a final investment decision in 27, so we have some time.”

Sun Cable is looking to build its project in two stages. The solar, and wind if it is chosen, will be built more than 800kms south of Darwin where the solar resource is less affected by the summer monsoon, and will be connected by two HVDC transmission lines, each capable of transporting up to 3 GW of capacity.

The first stage of the project will feature one of those HVDV power lines and will focus only on domestic manufacturing and other green industries in Darwin, particularly the Middle Harbour precinct, possibly at an initial 800 MW, but rapidly growing to 3 GW.

The second stage will add the second the second HVDC power line, with around 1 GW of that capacity boosting its supply to Darwin, and up to 2 GW going via a 4,300 kms sub-sea cable to Singapore, if an agreement can be agreed with authorities in that country.

The very idea seems wildly ambitious to many in Australia, particularly given the nature of the domestic political debate around energy, and the claims that renewables can’t possibly power industry, which is exactly what Sun Cable proposes to do. Without big industrial loads, it will have no customers.

But Garnsworthy says the idea of wind and solar exports is not so unusual in other parts of the world, with many countries looking to profit from their growing renewable resources and laying sub-sea and land-based cables to export cheap and green power to those demand centres struggling for supply.

“Many people are doing what we are doing,” Garnsworthy says. To the point that one of the biggest supply chain issues the project may have is the massive converter stations needed to convert the power back from AC to DC and back to AC again so it can be delivered to customers.

It does have time up its sleeve, although that may not be so much time for a project of this scale. Garnsworthy says Sun Cable is planning to reach a financial investment decision (FID) in 2027, and financial close (meaning debt and other investors locked in) in 2028.

Construction will start in late 2028 or early 2029, with the first power delivered in the early 2030s.

By that time, greater clarity will have emerged about its storage options. Lithium ion chemistry is one obvious choice, but there may be others too, offering longer duration storage options with different chemistries, most of which are still in their early stages.

The final requirements will depend on the final mix, and cost, of the bulk energy supply from solar and wind. “We’re not placing orders yet,” Garnsworth says.

“It’s a very interesting project. If you take a step back and look at the scale of project, it needs to be large to justify the transmission line. What we are working on is de-risking the project – customers, approvals and the like – so we can take our final investment decision.”