Batteries are an obvious, if expensive, way of storing solar energy for later use. Not every home has one, unfortunately, which is why midday exports on parts of networks with high PV penetration are becoming a problem.
In Melbourne, the United Energy distribution network moved early on this issue last year when it trialled two 85kWh batteries installed up poles in suburbs where solar exports were pushing down demand. The two Kokam batteries performed well over the summer, reducing peak demand – when the stored solar energy was discharged – between 10 and 20% and supporting between 50 and 75 homes with energy up to 2.2 hours at a time. “We were pleased with their performance,” says Greg Hannan, head of network strategy at United Energy.
With the rooftop rollout expected to see solar systems installed at a steady clip in Victoria, United Energy is launching its “Electric Avenue” project, with 30kW/66kWh community batteries to be installed up power poles at 40 sites in the network’s domain.
Most of the new batteries will be bunched within a 15km radius east and southeast of the CBD, with others around Frankston to the south and a few more deeper into the Mornington Peninsula.
The idea, Hannan explains, is to defer traditional network augmentation, an example being where pole-top transformers would be upgraded in areas where demand exceeded local capacity limits.
With batteries it’s different, he says. “We looked at the loading on the lines where there were forecast to be constraints,” he says, “and then we also take into account what is the least impactful location from a community point of view.”
The exact location of a pole-top battery takes into account loading levels, the technical characteristics of the local circuit and community issues, such as visual impact and whether anyone is close enough to be bothered when it gives off a low hum.
An optimal distribution of storage assets along suburban feeder lines becomes “the least-cost solution” for the network.
Well-placed pole-mounted storage helps manage demand constraints but also improves power quality and calms voltage issues, problems that can visit parts of a network as more homeowners install rooftop PV. “If you happen to be the unlucky last person [on a feeder line] to put in solar the voltages can be really high at certain times of the day because of exports,” Hannan says.
“It’s a trend – as you see more and more solar you’re going to get more and more of these hot spots.”
Other than seeking out points along the wires where voltages are high, the network also takes cues from solar owners’ complaints about receiving zero export limits. “Most customers have in their mind that the economics of solar are about accessing feed-in tariffs. These batteries are about trying to target that problem as well.”
The average residential solar system is getting bigger every year, growing from 4.99kW in 2015 to 8.04kW in 2020, according to the Clean Energy Council. United Energy’s low-voltage distribution network serves 660,000 customers, including 93,000 solar connections.
Hoisting batteries up poles makes sense to United because there are many more poles than suitable ground-level sites and, because of their small size (the batteries weigh just under 2,000kg), it’s simple enough to connect them to existing overhead infrastructure. The batteries used in the Electric Avenue project will be made by Melbourne company Thycon.
The 40 batteries will charge around noon and discharge into the evening peak, unless called upon as part of their other role to act as a virtual power plant directed by retailer Simply Energy. The VPP function will be activated opportunistically by Simply Energy to trade in the wholesale market for demand management and to provide frequency control ancillary services to the grid. The retailer will make regular payments to United Energy for the privilege.
“When we need them, [Simply Energy] won’t be able to trade them,” Hannan says. “Outside those times, they will make decisions based on the market conditions as to how they use them.”
The lease payments from Simply Energy, combined with deferred network augmentation costs and a $4 million grant from the Australian Renewable Energy Agency have stacked up to make a good business case, Hannan says. “It’s a good example of where one asset can provide multiple benefits.” The entire project will cost nearly $11 million.
Simply Energy will offer its solar-owning customers a product linked to the VPP.
A ring-fencing waiver from the Australian Energy Regulator has made it all possible, Hannan says. “It’s a really good example of how networks and retailers can collaborate; it’s one battery but it’s being used by the network [and] it’s able to provide benefits into the wholesale market – there is one battery servicing multiple revenue streams.”
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| The United Energy and Powercor networks are adding storage based on success of a trial of two pole-mounted batteries. |
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