Flexible exports: It looks like the future of rooftop solar for households

The Australian Renewable Energy Agency is funding a new trial for “dynamic” or “flexible” for rooftop solar systems in Victoria and South Australia, in what is shaping up as a new standard for managing the huge growth in rooftop solar systems across Australia.

The ARENA-funded trial will look at how smart controls and communications can allow network companies to “manage” the export of rooftop solar back in to the grid, subject to local conditions and what is happening elsewhere in the grid.

It is not an entirely new idea – one trial has already been completed in Queensland, and it is being considered in Western Australia. But it is one that is considered by networks to be essential to manage the future grid, and to avoid static and sometimes arbitrary limits being placed on exports from solar households.

In South Australia, new households are restricted to a maximum export limit of 5kW, but the situation in other states – Queensland, Victoria and NSW if often more severe, with some new solar households told they will not be allowed to export any output back into the grid due to local constraints.

The idea behind dynamic or flexible exports is that it will free up all households to export solar power, but the amount they are allowed to do so will vary from time to time.

The new trial will be operated by SA Power Networks in it home state and AusNet in Victoria, and they will team up with a range of inverter and other technology providers including Fronius, Solar Edge, SMA and SwitchDin.

The trials will begin next April in yet-to-be-identified constrained areas of the grid, and to new installations. If successful, it will then be rolled out elsewhere, including to existing customers.

SAPN insists that it is all about increasing the capacity of the grid to support rooftop solar. “We think we can double the amount of rooftop solar in the local grid by 2025 without investing in any new capacity,” SAPN spokesman Paul Roberts told RenewEconomy.

SAPN is also rolling out upgrades to 140 substations that include voltage controls that will also lift the capacity of the local grid to absorb  rooftop solar. In the daytime, voltage is dialled down to allow more rooftop solar  to be exported, and dialled up in the evening to deal with peak demand.

South Australia is also entering a “brave new world” for rooftop solar which requires inverter standards to be strictly enforced, and for new solar households to appoint an “agent” – either an inverter supplier, or communications specialist, or the network owner itself – to be able to “switch off” rooftop solar if the market operator deems it necessary to maintain the stability of the grid.

That’s because rooftop solar demand continues to soar and now accounts for more than two thirds of daytime demand on occasions in South Australia. AEMO expects it to cause “negative demand” within the next two years, and says it has to have control over the new rooftop solar installations to manage grid security.

SAPN believes that “dynamic exports” – along with the connection of the new transmission link to NSW, known as Project EnergyConnect – may remove the need for intervention to switch off rooftop solar systems completely, if the exports can be effectively managed.

Export limits in South Australia were reduced from 10kW to 5kW (per phase) in 2017, but SAPN is working they will have to be dialled down further, possibly to zero for new installations, without a management tool such as dynamic exports.

Those initiatives include a new solar sponge tariff – designed to switch demand to the daylight hours, including hot water systems and, in the future, electric vehicle charging – and more controversially, export tariffs – a proposal that is going through the market rule make but may be some way off.

ARENA is putting in $2.09 million into the trial, which will cost around $4.84 million and last around 12 months and involve a total of 600 customers across the two states.

ARENA says that if the trial is successful, this approach could create a new solar connection agreement which could be adopted by any compatible solar inverter product and any network across Australia.

“Currently less than 10 per cent of rooftop solar systems installed across Australia operate with smart control systems which means many people are limited by what they can export back into the grid, ” ARENA CEO Darren Miller said in a statement.

“If the trial is successful, it should help more customers sell more of their energy into the market and benefit from cost savings on their energy bills. (SAPN puts those savings at “several hundred dollars a year).

SwitchDin CEO and founder Andrew Mears says the only tools available for networks now are constraints embedded in their connection agreement, with some households limited to the amount of solar they are allowed to install, or limited to the amount of exports.

“These are blunt instruments,” he told RenewEconomy. “These (new technologies) offer a flexible approach to respond to peak demand and low demand periods,” he said. “This is going to be an option for networks across the country.”

Mark Byrne, a solar advocate and energy policy expert at the Total Environment Centre, agrees that dynamic or flexible exports are a batter alternative to zero or close to zero static export limits.

“Of course it depends how often systems will be throttled back, and if the total solar capacity on a feeder or in a substation area is increasing, then systems will be constrained more and more often unless the network is also incentivised to augment capacity,” he said.

Which is why the TEC and ACOSS are pushing for any new export tariffs be combined with a commitment from networks to increase capacity, a move that Byrne insists will cost little compared to total network spending budgets.

“If this is gonna be rolled out widely there are some consumer protection issues to consider – e.g. prior informed consent and whether my inverter is going to be effectively managed from another country!”