THE electricity grid has become “more unstable” because of the rise of renewables and the loss of coal-fired generators, the Australian Energy Market Commission is warning in a report on the system’s performance released on Tuesday.
The report says we have enough power to meet demand in the short-to-medium term but there is a “growing problem” in mixing solar and wind-power – described as “weather-driven generation” – into the grid.
“The national grid is becoming more unstable because of this changing generation mix,” the market commission says.
The market commission says the large coal-fired, hydro and gas-fired power stations have “inertia” and “synchronicity” that keeps power on voltage and frequency in the face of sudden changes in supply or demand.
The “weather-driven” generators – wind and solar – lack inertia, and require an “inverter” to turn their direct current or DC into the alternating current or AC used in Australia.
Renewables advocates say there are ways around these problems, and the market commission says it has taken major steps to counter the changing nature of the grid and is seeking industry feedback on other proposals.
The new report says the power grid “dropped outside secure limits” 11 times during 2016-17 – including the South Australian blackout – up from seven times in 2015-16 and four times in 2014-15.
The commission’s chief executive, Anne Pearson said the electricity “technology revolution” was “well-established” but the system had to be “managed differently” in “more challenging times” in order to cope with the changes and to “keep the lights on”.
The issues around synchronicity and inertia are well known within the power industry but have received little airing in public debate, perhaps because of their technical nature.
A Liberal Party win in South Australia at the weekend has already triggered a new round of debate about national power policy, with the new government likely to steer that state away from the strong renewables policy of the former Labor regime.
Even so, large-scale batteries such as the Tesla installation in SA are as much about “balancing” the system as anything, with a second report by the market commission – a draft document on frequency control – noting “there are a range of new technologies connecting to the system, including battery storage, that are capable of providing frequency control”.
The market commission says overall demand for power has been flat, thanks to power saving devices and roof-top solar, with the system losing 1600 megawatts with the closure of Hazelwood power station.
The system is set to lose another 2000 megawatts of capacity when Liddell shuts in 2022. The commission says another 1312 megawatts of solar and wind power had been “committed” to the grid during 2016-17.