In particular, the board listed two must-haves amid a transition to more renewables: ensuring reliable energy supply and stabilising grid frequency.
Expert in electrical grid systems and University of Melbourne Engineering Professor Iven Mareels agreed with the point, saying that although he believed Australia had to pivot away from fossil fuel energy, several key logistical challenges had to be addressed first.
“We can’t transition like a cowboy,” Mareels told The Epoch Times. “We have to transition carefully.”
Mareels clarified that the switch was not an overnight endeavour, with careful design and planning with the best brains behind it essential in reinforcing a robust, well-functioning electrical grid.
“Saying ‘we can do this overnight, take all the coal-fired power plants, and she’ll be alright mate’—it’s not going to work,” he said.
Mareels’ point has been illustrated several times over the last three months, beginning with coal plant outages in New South Wales (NSW) that forced Australia’s largest aluminium smelter to halt operations and power down five times in two weeks.
Then, a fire at the Callide coal plant cut power to 400,000 Queenslanders and plunged parts of the state into a blackout.
Combined, these coal power outages subsequently propelled average household energy prices across most of Australia to three times that of last year.
Ensuring Sufficient Renewable Energy Supply
Mareels explained that the intermittency of wind and solar meant more wind turbines and solar panels—also known as photovoltaics (PV)—had to be built if they were to compete with similar output from fossil fuels.“A gigawatt of PV is not a gigawatt of coal-fired power,” Mareels said.
This is because wind and solar generation depend heavily on weather conditions and the time of day—with windless nights or cloudy days severely hampering renewable energy generation.
Owing to these factors, Mareels said that, even with generous estimates, the expected output for solar and wind would on average be one quarter, or 25 percent, of its maximum capacity.
This meant four times as many solar and wind farms would be required to deliver the same amount of energy in the long run.
“People have to realise the grid now is about 40 gigawatts of power. In order to do this with renewables, we probably have to build something that is four times bigger—we probably have to build something like 160 [gigawatts].”
But Mareels said that the 25 percent figure was still optimistic, with current values only at around 16 percent.
As a result, Mareels highlighted that, even with solar and wind producing energy at no cost, the construction of a renewables grid of the future with additional interconnecting infrastructure would carry a far larger price tag to go along with it.
Furthermore, Mareels pointed to pumped hydropower—instead of lithium-based batteries—as the optimal choice for large-scale grid energy storage.
While pumped hydro projects—which use water reservoirs to store energy—can be more expensive than big grid batteries, the energy storage capacity offered is substantially greater.
For example, Snowy 2.0—a pumped hydro project headed by the Australian government—is 25 times more expensive than South Australia’s new big battery, but its storage capacity will be 1,400 times greater.
Why Grid Frequency and Inertia Matters
In addition to supply, Mareels explained that maintaining grid frequency was one of the most important technical aspects required in a functioning grid.In Australia, every home, business, and power station has alternating current (AC) at a frequency of 50 Hz (hertz) coursing through its electrical cables.
Typical coal, gas, and hydropower systems are backed by turbines that make generators spin at 50 revolutions per second—or 50 Hz. And as a result, every part of the grid is inextricably linked to this frequency.
However, when Australians return from work on a cold winter evening and crank up the heating or on a hot day the airconditioning, the frequency drops, and the turbine-based power stations are fired up to try to bring the grid back to 50 Hz.
Mareels explained that the big thermal generators carried with them a huge amount of “inertia”—or the tendency to keep spinning and resist change, even as power demand grows.
“They’re big, and they are rotating, just like a train. You can’t stop a train when it’s running, right?” Mareels said.
Because the generators can keep spinning and help keep the grid at around 50 Hz—at least for some time—even as energy demand grows.
“The rotating machine contains an awful lot of kinetic energy,” Mareels said. “And if the grid slows down, then the machines say ‘Hey, I don’t like this,” and it takes some of its own kinetic energy away and pumps it back into the grid.”
Crucially, then, Mareels explained that the inertia bought the grid time to react until new energy generation was fired up to meet the demand.
However, with a lack of large spinning generators, solar and wind lacked inertia altogether.
South Australia had previously experienced the brunt of a blackout in 2016 after extreme weather forced several wind farms offline, with a series of events inevitably leading to a power supply shortfall, leaving 850,000 of the state’s residents without power.
Prior to this, South Australia ceased its last coal-fired power station earlier in 2016, which saw the exit of 520 MW of inertia-delivering generation. The Australian Energy Market Operator later declared an inertia shortfall in South Australia in 2018.
To ensure baseline inertia and power security levels, AEMO was also forced to manually intervene 321 times in 2020 to ensure spinning thermal generators continued to stay online after wind and solar power peaked. This was in contrast to 2016, when AEMO had to manually intervene just 6 times.
Mareels said one solution was keeping the generators connected to the grid without being hooked up to the coal or gas turbines, acting as “synchronous condensers” that spin freely whilst providing the system with inertia.
The Path to an All-Renewables Grid
Environmental groups have pressed for Australia to halt developing fossil fuel power, but Mareels said that gas might be key in facilitating the transition over to an all-renewables electrical grid.
“I wouldn’t keep coal-fired power plants alive at all. I think we can do without them,” Mareels said. “But we have to plan the transition from having coal-fired power plants 70 percent of our power, to zero, carefully.”
Mareels elaborated that gas power plants produced fewer emissions than coal, brought a source of inertia into play, could be converted to hydrogen easily, and can deliver power extremely fast—supporting renewables during periods of low output.
“It’s a transition measure,” Mareels said. “The environmentalists are right; a carbon gas-fired power station is still a fossil fuel.”
“On the other hand, in the meantime, because we don’t have enough inertia in the renewables system, we need inertia from somewhere. And the cheapest way is to use gas power plants because they have a lower carbon footprint than coal.”
“Most gas-fired power plants probably can run on hydrogen as well, so you can switch them over to something more renewable afterwards,” Mareels said.
“And they can act quickly, and that act quickly is important. The coal-fired power plant cannot compensate for the vagaries of PV and wind, but the gas-fired power plant can. If wind drops, gas can drop in almost immediately and pick it up where the wind left off. And the battery can do that, but only for a very short period of time.”
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