Utility to take part of Melbourne suburb off-grid with solar + storage

Victoria network operator Ausnet Services is to take part of a Melbourne suburb completely off grid, powered only with rooftop solar and battery storage, in a first-of-its kind trial in Australia that points to the speed of the household energy revolution.

There is growing interest in the use of  mini-grids in Australia, using local renewable energy sources to take remote towns and new housing developments either completely off the grid, or equipped with a “small” connection.

But the planned trial by Ausnet – to be launched by Victorian energy minister Lily d’Ambrosio on Tuesday – points to the fact that mini-grids may also be used within major towns and cities as a cost-effective alternative to the century-old model of large centralised generators and expansive and costly networks.

Ausnet is to install between 3kW and 4.5kW of rooftop solar and 10kWh of battery storage on each of 14 homes in the outer eastern suburb of Mooroolbark, chosen because the homes are typically suburban, and because Ausnet has a network constraint it thinks it can solve with distributed energy (solar and storage), and because the network configuration means that it is relatively easy to take them off the grid.

The network operator will first monitor the production and consumption patterns of the 14 homes, before then inviting them to individually quit the grid, and see how long that lasts, and then to quit the grid altogether but share their solar and storage in an islanded network.

The 12-month trial will repeat this in several different seasons.

Ausnet managing director Nine Ficca says the “exciting” and “ground-breaking” trial is designed to demonstrate that homes with residential solar systems and batteries can generate, store and share renewable electricity with each other, and operate as a ‘mini grid’ via their local power lines.

“AusNet Services is excited to partner with the community to develop systems that may give consumers the choice to share their solar-generated electricity with their communities, potentially lower their bills and support the electricity network,” Ficca says.

The interest of the network, of course, is to remain relevant in a future that is dominated by locally generated solar and battery storage. Most utilities now accept that, within a few decades, around half of all electricity demand will be satisfied by “distributed energy”, and this means a complete revision of the energy market structure.

Networks are confident that they have a key role in this future, because it will make sense for communities to “share energy” and they will need wires to connect to each other. The future role of centralised generators and retailers is less clear.

Ausnet’s trial will build upon a recently completed three-year residential battery storage trial with homes in its network, which analysed usage and consumption patterns, and the potential returns on investment and tariff structures.

That study found that residential battery storage is not yet “economic”, but quick payback times may not be far off given the expected sharp fall in battery storage prices, which are expected to go down by half in coming years.

The most interesting aspect of that study was the conclusion that residential battery storage could offer as much, or even more, benefit to the network operator than to the consumer.

That’s because of the potential savings on network upgrades, and the ability to use battery storage to reduce and manage peak demand, provide stability to the grid, to provide power during outages caused by storms and other events, and to defer upgrades.

Some utilities are finding that the most effective means of saving costs for new developments, and for remote towns, may be to not build a grid connection at all, and provide a local network solution – or a mini-grid – instead.

Many utilities are trialing solar and battery storage in various situation, and particularly in sharing the output, including in housing developments Alkimos and White Gum Valley in Western Australia, and several trials in Queensland.

The Ausnet trial in Mooroolbark will be the first, however, to take a group of existing suburban homes completely off the grid. Ausnet says it is in talks with other towns and communities about similar projects.

“We’ve developed a control system that will monitor and manage energy flows within the mini grid,” Ficca says.

“This system will enable the energy that is stored in batteries to be shared between houses, based on the needs of the individual houses, the diversity of customer loads within the mini grid and the needs of the network.”

The trial will use JASolar JAP6 60  solar panels, Australian-made 5kW battery inverters from Selectronics and 10kWh batteries from LG Chem.

Most of the houses are owner-occupied.