The move will see Defence's Robertson Barracks and RAAF Base Darwin leveraging on renewable energy and reducing its carbon footprint.

Managing director of Lendlease Services Toby Matthews said he is excited to announce the first solar contract with the Department of Defence.

"This critical infrastructure will support a broader Defence program to ensure long term energy security over their facilities."

The project team are expected to begin work in the next two months, with a completion date scheduled for the first quater of 2020.

Defence Renewable Energy and Energy Security program manager Allan O'Connor, said the solar farms would provide up to 40 per cent of Robertson Barracks and RAAF Darwin's electricity requirements.

"The NT Solar Power Purchase Agreement project is the first solar PPA undertaken by Defence," he said.

"It will provide up to 40 per cent of the site's electricity requirements via approximately 14MW of solar across the two sites.

The engineering, procurement and construction works will be delivered by Lendlease including the design of the solar array and battery storage solution, procurement, installation and commissioning of the of the system. Lendlease will also operate and maintain the system.

Closer to Katherine, oil and gas giant Eni - an Italian based company - has started work on a $40 million solar farm, touted to be the largest in the Northern Territory.

The 33MW solar farm will feature about 70 hectares of photo-voltaic panels with a 5.7MW battery energy storage system recently added.

Power produced from the project will be fed into the NT's grid under a deal signed last year with Jacana Energy.

The solar farm is expected to be operational by the end of this year.

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