The latest news in the National Electricity Market (NEM) is AEMO’s goal to be capable of handling periods of 100% instantaneous renewables penetration by 2025. This is a significant challenge and fitting given the pace the NEM is moving to, supporting increasingly higher levels of instantaneous (and increasingly asynchronous) renewables on a regular basis.
While this challenge may not be as pressing for all NEM regions, the need to identify methods/technologies to enable higher asynchronous generation is a welcomed objective in future-proofing the NEM. To visualise the differences between regions in this transition, the chart summarises the last 18 months in the NEM into duration curves of the renewable percentage of local generation for each NEM region and the level of supply being supplied from asynchronous sources (this includes import volumes in the calculation). Behind-the-meter resources have been omitted from the analysis, given the grid operation focus.
The significant presence of coal in the system for the foreseeable future means that the goal is not as pressing in Queensland (QLD), New South Wales (NSW) and Victoria (VIC). It is also not as pressing for Tasmania (TAS), which operates a mostly 100% renewable energy system. TAS is, however, increasingly incorporating higher asynchronous generation levels where 20% of the time, more than 50% of generation requirements come from asynchronous generation sources. However, the significant hydro capacity (i.e. synchronous generation) in the region means that TAS can have its cake and eat it too.
The region which is of most interest is South Australia (SA). To be clear, SA is already on the cusp of 100% instantaneous renewable power. Over the last 18 months, local grid-level renewables have exceeded local SA demand in ~13k dispatch intervals (~8% of the time). However, despite this, AEMO still relies on gas generation in the state as the key to system stability. At a minimum, there is at least 250 MW of gas generation online regardless of VRE penetration. So, the crux of AEMO’s 2025 goal is to remove the necessity to direct thermal units to remain online for system strength. New synchronous in the state should reduce the need for SA gas units to stay online.
However, capability is the first but important step. The key question then is when AEMO would have the operational confidence to reliably operate the grid with 100% instantaneous power from asynchronous sources. SA likely becomes the NEM’s proving grounds for these new operational approaches (if it wasn’t already).
System-level observations would likely be required as well as the presence of additional service support such as increased local Frequency Control Ancillary Services (FCAS) provision or grid forming types of technologies. It also means that the definition and quantification of the largest contingency will likely evolve from the loss of the largest single unit to the expected forecast change in Variable Renewable Energy (VRE) sources. It is unclear how this level would compare to the status quo, but it is clear is that this would be a different operating paradigm for AEMO.
While the current focus on supporting 100% instantaneous renewable power is a key challenge, a similar effort should be aimed at the inverse case – particularly without coal in the system. Granted, this challenge is likely to be more pressing later in the decade. However, it still requires attention in the near term to understand the required level of dispatchable generation (to allow for sufficient investment and planning). As we know from recent experience (Chart of the week 92), VRE droughts are a somewhat regular occurrence, and there must be enough backup on the system to handle prolonged events effectively.