Energy security isn’t just about preventing blackouts, grid operators and regulators spend more time simply making sure the power supply doesn’t damage all the systems (and appliances) that rely on it.
Every day, energy market operators are locked in a constant battle to stop household appliances such as fridges, irons and kettles from blowing up. While this might sound overly dramatic, grid stability and security is no laughing matter for the Australian Energy Market Operator and other regulators trying to chart a course for the ever-evolving electricity grid. It might be black-outs and grid reliability that gets the headlines, but energy boffins, including Energy Security Board chairwoman Kerry Schott, are more worried about grid security.
“The main problem in the market is actually one of security,” Schott told The Australian Financial Review National Energy Summit in October last year. It was Schott, the no-nonsense government energy czar, who raised the prospect of the exploding appliances as a way to demonstrate the challenges facing the grid, especially with the influx of intermittent renewable energy such as solar and wind.
Grid security involves technical terms like frequency, voltage, inertia and system strength, but it boils down to making sure the electricity grid operates as it was meant to. Schott told The AFR summit that networks in some cases were able to manage with 100 per cent rooftop solar penetration, while in others, solar exports exacerbated “over-voltage” or “under-voltage” issues. “What not being within voltage limit means, amongst other things, is that people’s appliances are going to blow up,” she said at the time. “So in certain places, there will be more people having trouble with their fridges and other appliances because the voltage changes, but more importantly the system becomes uncontrolled.”
The rapid influx of renewable energy into the electricity grid has been both a blessing and a curse for energy market operators. While the uptake of wind and solar has allowed Australia to move towards a lower-emissions future and meet international climate change agreements, it has also caused some headaches for grid stability and security. Coal-fired power generators may be big carbon emitters but they have provided the backbone of energy generation for decades and still account for two-thirds of electricity generation in the National Electricity Market (NEM).
A less well-known feature is what synchronous generators, such as coal-fired power stations, provide to the energy grid in terms of system security and stability. Solar and wind may provide a cheaper form of power when the sun is shining or the wind is blowing, but their intermittent nature makes it harder to deliver system security, which is essential for the efficient running of the grid.
Nuts and Bolts
According to the recent report by the Energy Security Board, a secure system is one that operates with an appropriate level of frequency, voltage, inertia and system strength. Frequency refers to the number of cycles of current and voltage made per second in an AC (alternating current) system. The operational frequency of the NEM is 50 cycles per second (hertz).
In a nutshell, the frequency of the power system requires a perfect match between supply from generation and customer demand. Voltage is the electrical force that helps the flow of electricity between two points. It is increased or decreased at various points using transformers. Inertia refers to the rotating of a turbine or alternator of a generating power unit. Synchronous generators, such as coal, gas or hydro, are in perfect sync with the grid – at 50 cycles per second – and they operate 24/7. All of these factors are crucial to keeping the lights on, and they are something that wind and solar generation are not able to provide.
“Variable renewable generation is non-synchronous and cannot easily accommodate variations in load power factors,” the ESB report said. “There is less inertia in the system so that a sudden change in frequency caused by generation ceasing unexpectedly, due say to equipment failure or a sudden change in the weather, cannot be easily arrested. “The anticipated exits of ageing synchronous coal-fired generation suggests that these security issues will take some time to manage.”
The instability caused by renewable generation has caused the Australian Energy Market Operator to intervene, especially in Victoria and South Australia.
Last financial year, AEMO intervened 75 times, up from 32 times the year before. Some 158 “directions” were made to market participants to maintain grid security in 2018-19, up from 100 the year before and about 10 before that. All of the directions over the last two financial years were due to system “security”, rather than “reliability” reasons, where generators are ordered to switch on to ensure adequate supply.
South Australia, with its lack of any baseload generation since the closure of the Northern coal power plant in 2018, has seen by far the most directions, but Victoria has also featured. They can involve ordering gas power generators to come online to provide stability in the system even when wind and solar generation is ample, or orders to cut generation output.
The interventions, driven by security concerns, cost consumers almost $18.2 million in 2017-18, moderating slightly to $15.7 million in 2018-19 despite a steep increase in the number of times AEMO had to step in. The length of time AEMO’s directions have lasted has also increased, from an average of about seven hours in the decade to 2016-17, then surging to 61 hours in 2017-18, then 26 hours the year after.
System security is different from system reliability, which is basically whether there is enough supply to meet demand.
The ESB said reliability – or energy reserves – has improved in the NEM since last year but supply is still very tight during summer peak demand in Victoria, NSW and SA. The grid is still dealing with the closure of older coal-fired power stations, such as Hazelwood in Victoria and Flinders in SA, with the number of Lack of Reserve notices issues by AEMO increasing in recent years. AEMO juggles the constant supply/demand equilibrium every day, ensuring there is enough power to keep the lights on. It and the ESB are looking to ensure the balance is also met in the longer term.
Grid instability due to new renewable generation came to the fore in September 2019 in the renewables-rich West Murray region on the Victoria-NSW border when five operating solar farms were ordered to cut back their output to 50 per cent. The market operator had detected abnormal fluctuations in voltage in the electrically remote area of the grid that threatened the security of that part of the network. Almost six months later, a technical fix is still being worked through, delaying several other new solar farms from connecting into the grid.
On a more local level, the problems can be seen in voltage fluctuations that can impact home appliances.
Schott – who chairs the ESB which features all the energy regulators including AEMO, Australian Energy Market Commission and the Australian Energy Regulator – is more worried about some areas of grid security than others. For frequency, rule changes are already in place, paving the way for a good working market for frequency services, Schott told The Australian Financial Review on Wednesday. Combined with the contribution from the rise of batteries, frequency is something Schott says she is “happy” about. On inertia too, Schott says the issues have been “pretty much fixed” through rule changes, putting the NEM well on the way to solving the issues.
Voltage ‘A Big Challenge’
But voltage remains “a big challenge,” she said, not so much in transmission but in smaller distribution networks. “You can see it in South Australia, where there is so much rooftop solar there are some parts of [Adelaide] where you suddenly get a drop in grid demand to zero or less and the distribution company then struggles with system control,” she said. “As a last resort the way we control that is turning the solar off, which is less than ideal.”
But Schott says the problems will eventually be solved by the distribution companies either putting in batteries within their network or by contracting with generators to provide that service. “That is not going to happen overnight but the steps are being taken and it’s well on the way,” she said.
With Australia charging down the path of renewables as fast as or faster than – in the case of rooftop solar – any country worldwide, what happens here to tackle these issues is of international interest. “The whole world is watching us because we are so far ahead on the rooftop solar that we’re sort of the bunny that everyone is looking at,” she says.
Article on AFR Website: https://www.afr.com/companies/energy/how-to-stop-your-kettle-from-blowing-up-20200224-p543og