Flexible rooftop solar exports could be a reality next year after trial success

South Australia could introduce flexible rooftop solar exports for households and businesses as early as the second half of 2022, after a trial found that virtual power plant participants were able to export more than state’s 5kW limit without compromising grid stability.

Flexible solar exports – that is, the ability to set export limits dynamically, according to the local conditions and at a point in time – hold promise as the new standard for managing the huge growth in rooftop solar systems across Australia.

South Australia has one of the world’s highest penetrations of rooftop solar on its grid, which has seen it set a state-wide residential solar export limit of 5kW and introduce strict, mandatory inverter standards to deal with the days that rooftop solar might supply the equivalent of 100 per cent of state demand, or more.

The harsh reality for many solar households is that residential solar export limits are common in all states and territories, with some households on what networks says are heavily congested grids unable to export any solar at all.

As well as putting a handbrake on customer returns from rooftop solar, static export limits effectively set a cap on the maximum power of a VPP, limiting its use to the grid and the incentives for customers to participate.

South Australia currently has nine VPPs operating on its grid, including four of significant size from Tesla (16MW registered), AGL (5MW), Simply Energy (5MW) and ShineHub (more than 2MW) that are actively participating in the FCAS market.

The 21-month Advanced VPP Grid Integration trial was led by the state’s monopoly distribution company SA Power Networks in partnership with Tesla and CSIRO and involved 1,000 households with solar and batteries.

The trial was not only successful in allowing increased household output beyond the normal 5kW per-site export limit, safely and without breaching local network constraints, but it increased the VPP’s total export capacity from 5MW to an average of 6-8MW during solar hours.

“By continually adapting to the changing condition of the local network, each VPP participating site was able to export more power to the grid than if operating on the standard fixed 5kW per phase limit, significantly increasing the VPP’s ability to trade in the energy market and provide valuable frequency balancing services to the grid,” said Mark Vincent, SAPN’s general manager of strategy and transformation.

“The capabilities developed in this project will help VPP operators create more value for customers from their investment in Distributed Energy Resources (DER) and will enable distribution network operators to integrate more and larger VPPs with the network without the need for costly network upgrades.

“This will increase the opportunity for customers’ DER to help the overall system run more efficiently, and also deliver more community value from existing network assets, helping to keep prices lower for all.”

Bryn Williams, SAPN’s future network strategy manager, told RenewEconomy that the company’s target was to have the option for flexible exports in place by mid-late 2022, subject to the success of a follow-up trial, which will focus on households with solar only.

“We’ve got a goal to double the amount of solar on our network by 2025 and to do that in smart ways, not by simply upgrading infrastructure,” Williams said.

“So we effectively made a commitment to build this capability between 2020 and 2025 and we’ve been able to accelerate that with commonwealth funding from ARENA.

“If you think of the alternative, if we continue with only a fixed limit, then that … will have to keep coming down” as more and more households install solar, he said.

Williams said that limits of around 1-1.5kW would quickly become the standard for households that chose not to switch to flexible exports, while households equipped for flexible exports would be looking at up to 10kW inverters.

“This is a key capability that everyone is concerned about for the future market. You have to make sure … that all [distributed energy resources] can operate within the technical limits of the network.

“We’re super excited by the trial and [its] results,” Williams added. “It’s a glimpse into the future.”