The 80% renewable electricity target by 2030 cannot be achieved unless there is sufficient storage in place for the output of variable renewables.
When you think about it, storage has always been a primary issue for electricity generation. In the case of coal there has always needed to be sufficient coal in bunker storage at a power station to feed the furnaces. Coal is a concentrated form of “solar energy” that was captured by plant photosynthesis many millions of years ago – so it is a form of energy storage. Likewise with gas.
As Australia transitions towards a planned renewables-based electricity generating system it will be critical to have sufficient storage to maintain power supply during periods when intermittent primary generation sources are not producing power. Shutting down existing dispatchable, fossil-fuelled generation before the required storage is in place will likely lead to frequent, unpredictable, widespread blackouts.
As discussed in a previous instalment, solar PV (especially rooftop solar) has a low capacity factor since electricity is only produced when the sun is shining. Let’s assume for simplicity that large scale solar PV with a capacity factor of 30% is the only source of generation. Electricity is produced during an 8h daytime window. What about the rest of the 24h period?
To ensure that sufficient electricity is produced for a 24h period, “surplus” electricity needs to be produced and stored during the day, for use during the dawn and dusk periods and through the night. This means that more than 3 times, over and above the daytime requirement, needs to be produced and stored. Thus, a 300MW nameplate capacity solar farm would be needed to produce 100MW, averaged over the 24h period, with sufficient storage.
The situation is more complicated with wind because of its intermittent nature, noting that the average capacity factor of an onshore windfarm in Australia is about 35%. However, in contrast to the regular and predictable day/night cycle for solar, wind is typically quite variable. So even with overbuilding x3 to allow for the capacity factor, if there is no wind (be it day or night) there will be no power produced.
So, we are going to need storage and LOTS of it, if our current electricity system is going to function with 80% renewables by 2030. What are we looking at for 2030 and how much more is going to be needed between now and then, and beyond?
Australia’s total current storage capacity is only 3GW. Current forecasts by the Australian Energy Market Operator (AEMO) show Australia will need at least 22GW by 2030 – a more than 7 fold (700%) increase in capacity in the next six years.
The market operator’s https://aemo.com.au/-/media/files/major-publications/isp/2024/2024-integrated-system-plan-isp.pdf?la=en (ISP) forecasts Australia will need at least 49GW of storage by 2050 in order to reach net zero.
In my next instalment I will be taking a closer look at the main options that are being proposed for large scale storage – pumped hydro and batteries – and the challenges associated with them.
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