Innovation and Adaptation

Powering Defence Force capability: the case for military micro-grids

By Sandra Benson, Kristy Bryden, Greg Colton and Craig Stieler May 12, 2021

On 28 April, the Prime Minister announced a $747 million package to upgrade military training areas and facilities in the Northern Territory, part of an $8 billion investment in Defence capital works in the Top End over the next decade. This work includes improving engineering services, such as power and water. Alongside this funding, Defence is also prioritising self-reliance, resilience to shocks and outside interference, and support to civil authorities in response to natural disasters and crises.

These upgrades are timely; reliable electricity supplies, on which modern military systems depend, are increasingly threatened by a range of risks. Extreme weather events remain the most likely threat, with weather related factors accounting for over half of all electricity outages across the country, but electricity generation and distribution is also susceptible to deliberate action by a malign actor.

Therefore, any upgrade to military bases which remains reliant on a networked power distribution model remains fundamentally flawed. This article argues that if Defence wants to develop true power resilience, then it should mitigate this risk by exploring the option of on-base military micro-grids.

The threat in detail

Climate change is increasing the impact of extreme weather events across Australia. While the total number of cyclones occurring annually across Australia appears to be decreasing, their intensity may be increasing due to greater wind speeds and heavier rainfall resulting from rising ocean temperatures. This increases the likelihood of damage to local power networks. In 2011, Cyclone Yasi cut power to more than 200,000 properties in Northern Queensland. Seven years later, Cyclone Marcus left 22,500 homes (approximately 33%) without power and brought down more than 500 line spans.

Outside extreme weather events, rising average temperatures will increasingly strain electricity generators and distribution networks. Records from the Bureau of Meteorology (shown in Fig 2; right) show a clear trend in annual mean temperature anomalies.

Defence’s current dependence on external electricity supplies creates an unacceptable risk of frequent power interruptions during high temperature periods, as well as lengthy power outages following extreme weather events. Most notably, it threatens to reduce the capacity of Defence to support civil authorities after natural disasters.

The solution

Defence has publicly recognised the need to adapt its estate management strategy in response to climate change, with one of its five strategic aims being to “improve the efficiency of its resource consumption and strengthen resource security”. This focus is unsurprising; approximately 24 % of all Defence’s energy consumption is linked to offices, laboratories, computer centres and Defence establishments. There is a simple solution to this problem, one that provides both value for money and delivers tangible security benefits; the military micro-grid.

Micro-grids are autonomous electricity grids that can combine different forms of generation and storage to serve a specific site. They can be either isolated (islanded), integrated into the main power grid, or have the option to switch between the two. Micro-grids in Australia typically combine renewable energy sources (primarily solar and wind) and storage capacity with backup generators (e.g. diesel). Grid-connected micro-grids can have the option to sell excess electricity back into the grid.

Micro-grids have become increasingly beneficial in large facilities such as universities, hospitals, and military bases. In Australia, large micro-grids have been installed in a variety of settings, including Deakin University, King Island in Tasmania and Mawson Station in Antarctica. Defence has made a start, partnering with industry to develop micro-grids at Delamere Air Weapons Range and Bathurst Island in the NT, and at Australia’s largest naval base, HMAS Stirling in WA. It is time to expand this concept to include all major Defence bases.

Can Defence afford it?

In FY11-12 (the last year energy use reported under the Energy Efficiency in Government Operations policy was made public), Defence spent approximately $124m on electricity. Defence has calculated that the department accounts for almost 0.5% of the total energy consumption in Australia, and equates to 70% of the total energy use by the Australian Government. This is projected to increase in the future and represents a risk to the Defence estate budget: money spent on electricity bills cannot be used to upgrade warfighting capabilities or pay for a larger workforce.

Defence contracts its electricity supply from retailers in its site locations. As with all customers, Defence's contract prices would be affected by changes in wholesale market costs, regulated network costs, environmental costs, and retailer costs. Wholesale costs have had the most significant impact on prices in recent years. While the increase in renewables and the declining cost of gas has started to bring those costs down, prices in most states remain well above the previous peak in 2013 and are expected to increase after the closure of the Liddell coal-fired power station in FY22-23.

Micro-grid costs depend on location, size, storage capacity and the generation technology. HMAS Stirling’s micro-grid, comprising 2MW of solar PV and a 2MW/0.5MWh battery energy storage system cost $7.5 million. The micro-grid at the Agnew gold mine in Western Australia will combine an 18MW wind farm, a 4MW solar farm and a 13MW/4MWh battery energy storage system and is projected to cost $111.6m. Defence sites located in areas of extreme weather risk will benefit most from the security and resilience provided by a micro-grid. These also happen to be areas of high solar exposure, and the cost of utility scale solar has plummeted in the last ten years, as seen in Fig 3.



In its Environmental Strategy 2016-2036, Defence identifies the reliable and continuous supply of energy as "critical to sustaining Defence capability". However, the energy market's transition to a more complex mix of technologies is creating concerns about reliability and system security. This risk is exacerbated by increasingly intense extreme weather events, which threaten to reduce Defence capabilities at precisely the time it is required to support local response activities. Perhaps the real question is not whether Defence can afford to build military micro-grids, but rather whether it can afford not to.



Sandra Benson, Kristy Bryden, Greg Colton and Craig Stieler

Sandra Benson, Kristy Bryden, Greg Colton and Craig Stieler are students at Southern Cross University where they are studying how advances in science can be used to tackle global challenges. 

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