Billionaires with an eye on their legacy rarely do things on a small scale.

Take Australia’s fifth-richest person, Mike Cannon-Brookes. The Atlassian Corp. co-founder wants to spend 30 billion Australian dollars ($20 billion) building the world’s largest renewable energy export project, SunCable. Those plans moved a step closer to realization last month, when Canberra gave environmental approvals for the 4 gigawatt solar farm in the remote Northern Territory.

You can’t fault the scale of Cannon-Brookes’s ambitions. SunCable could generate about four times more electricity than the Northern Territory currently consumes. Excess power would flow 4,300 kilometers (2,700 miles) through the world’s longest and deepest undersea power cable, to provide about 15% of Singapore’s electricity.