South Australia considering shutting down rooftop solar to stop destabilising the power grid

Author: Angela Macdonald-Smith

Solar households in South Australia are facing mounting risks of their rooftop panels being shut down to avoid destabilising the grid as regulators, policymakers, and network owners race against time to reform market rules and modify the power system.

The energy market operator last week emphasized the increasing difficulty of keeping the grid stable amid world-leading levels of ‘‘invisible and uncontrolled*’’ rooftop solar. [*dark power grid data]

VECTO System-Energy_Rooftop-solar-panels-on-house
Gray Watson – Photovoltaic solar cell panels on the roof of a house

It wants to be able to cut off rooftop solar if necessary as a ‘‘backstop’’ measure in extreme conditions and said local limits on new solar installations or costly retrofits of existing solar systems may be needed without reforms.

Rooftop solar is already South Australia’s largest electricity generator with about 1300 megawatts of capacity involving one in every three homes.

‘‘At the moment the risk and the issue is, that there is no co-ordination of that electricity supply,’’ said a spokesman for SA Power Networks, the front-line distributor dealing with solar households. ‘We’re really excited about the solar opportunity but there are growing pains to be managed.’’

South Australia Power Networks

How much power is generated by rooftop solar in South Australia?

At times last year, as much as 64 percent of South Australia’s power was supplied by rooftop solar panels, more than double any other state. By 2025, that could rise to as high as 85 percent, with NSW, Queensland, and Victoria all at about 50 percent or higher, the Australian Energy Market Operator said.

What are the problems with rooftop solar being fed into the power grid?

The challenge for AEMO arises in particular on mild, sunny days when rooftop panels are pumping out so much power that demand for grid power falls to a level that threatens the security of the system.

For SAPN, the main issue is around increased voltage which can cause inverters on solar systems to turn off, an increasingly frequent complaint by customers.

That’s happening ‘‘reasonably frequently’’ on the network in metropolitan Adelaide, the SAPN spokesman said, pointing to a mild spring day last October when the rooftops in the southern suburbs of the city were generating so much solar power that the area became a net generator of power into the grid. SAPN has drawn up proposals to tackle the issue and to avoid having to limit further solar connections. Those include lower network tariffs for the hours around the midday peak that could be 25 percent of the standard tariff, compared to 125 percent at peak times, and which will be available from 1 July 2020.

How to prevent electrical blackouts caused by distributed generation?

The distributor is also working with industry and manufacturers on upgraded settings for inverters to allow for the co-ordinated operation of rooftop solar systems. It also wants to introduce flexible limits for solar exports onto the grid, strictly limiting the surplus power from solar households on mild days but allowing for maximum exports on cold days.

South Australia’s Minister for Energy and Mining, Dan van Holst Pellekaan, said the state government was working closely with AEMO and industry to maintain energy security in the state.

‘‘A number of responses to the challenge posed by South Australia’s high penetration of renewable energy and consequent low grid demand are currently being considered,’’ he said.

‘‘What is certain is that the planned interconnector with NSW, the world’s largest per capita roll out of home batteries and South Australia’s grid-scale storage will be integral to maintaining system security.’’

End of original article by Angela Macdonald-Smith

How can we prevent power outages?

A key to controlling this, “invisible and uncontrolled solar” is the understanding that the paradigm, upon which the original power grid was built, is centralised generation and control. Rooftop solar generation represents a different paradigm — distributed generation.

Grid Codes (and Record of Inter System Safety Precautions – RISSP) currently govern the various sources of power flowing into the grid. Base power generation plants have established feedback mechanisms that allow them to maintain power grid stability. Large scale renewable energy providers subscribe to a grid code. This allows girds, using centralised control, to adjust their generation based on those RE feedback loops.

With rooftop solar, there is no feedback mechanism to facilitate control. Each rooftop is a single source of energy. There is no centralised mechanism in place to control the energy entering the grid from tens of thousands of rooftop solar installations.

When this uncontrolled and variable source of power transitions a percentage of grid power, the traditional mechanisms in place to manage the grid, are no longer sufficient to maintain a stable grid.

Dark Energy Data – The Elephant in the Room

A core issue is the lack of access to actionable, grid-wide energy flow data being fed back into the existing feedback control systems. This ‘dark-data’ is the elephant in the room. Legacy metering and control systems were designed for a centralised grid distribution paradigm. It’s a significant technical challenge, not to mention a significant financial investment, to modernise these systems.

In order to build out efficient, distributed control mechanisms, that don’t rely primarily on engineers manning a control room, grid operators require comprehensive, grid-wide, near real-time data, to inform their control mechanisms.

The real problem is that no such centralised, real-time energy data store exists. Energy flow data is embedded in bespoke, disconnected, and diverse metering and control systems throughout operators’ grids.

The ability to control starts with the ability to measure. Near real-time, grid-wide metering will give engineers the information they need, to develop actionable strategies to transition to a distributed power grid.

Without this data at their finger tips, engineers are forced to use sample data from various points in the grid to formulate solutions. The challenge lies in the sample set size and what is occurring on the grid during the sampling period.

If grid scenarios are not included in the sample set, engineers are left with an incomplete picture with which to develop strategies. In this scenario, at some point, the plans compiled will not be sufficient and the grid stability will be at risk.

A full picture of the grid, as it stands, is the precursor to a successful transition to a resilient, distributed grid architecture. Policy makers need to give engineers the data they need if they are to expect a successful transition.

Expanded from an article by Angela Macdonald-Smith for the Financial Review

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