By Phil Kreveld
The 2024 AEMO draft inputs, scenarios and assumptions report just released is the forerunner for the 2026 Integrated Systems Plan. The report hints at a bigger role for consumer energy resources (CER)—and just maybe—a rethinking of not yet locked-in transmission projects.
The role of CER is a regular topic of conversation for the Smart Energy Council and Energy Networks Australia, always promoting an expanding role for household and business solar systems. And, no doubt, at the forthcoming plenary sessions of Australian Energy Week (Melbourne, 17-20 June) audiences will be treated to enthusiastic endorsements of CER and its importance in reaching the renewable targets.
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However, ‘singing to the choir’ is of no benefit—and one could be excused for feelings of déjà vu. Cold water on a CER energy independent future has, in the past, been provided by AEMO. Historically it has been very careful in not considering distribution networks as other than dynamic loads, hence the newish Emergency Backstop requirement for disconnection of solar inverters. It is a measure to prevent instability in the high voltage transmission grids due to zero energy requirement in distribution networks.
A decade or so ago would have been the time to allot clearly defined boundaries to (a) transmission and large-scale generation, and (b) distribution networks, with CER. This might then have fixed for ‘all time’ that the latter would always continue to be loads, and the former, responsible for the technology required in reaching the renewable targets.
Undoubtedly that would have led to strict regulations applying to rooftop solar, limiting capacity and establishment of quotas for permission to install systems. Such a scenario sounds completely crazy these days and any suggestion that household solar might be restrained would cause political uproar.
Whenever the subject of a net generating role for distribution networks was raised by participants at public discussion sessions organised by AEMO, it would be politely ‘flicked away’. Does the bigger role for CER and a revision of transmission projects now intersect on AEMO’s Venn diagrams? That might hint at a ‘crazy brave’ change of heart. But let’s jump to three large computer programs; GridLAB-D, HELICS and GridPACK, and get an idea to support ‘crazy brave’.
The first one offers modelling of a distribution grid with 550 inverters on one feeder, the third program models a transmission grid and distribution grid set of buses with 10,000 inverters. The HELICS program connects the other two in one modelling system. Work on the programs was presented by Wei Du, senior research engineer at Pacific Northwest National Laboratory at a UNIFI Consortium presentation of 31 January 2023 with the title ‘Transient and dynamic modelling of droop-controlled grid forming inverters at scale’.
UNIFI is a consortium of grid supporting and grid forming inverter manufacturers and includes academia. Basically, the modelling of this vast number of inverters in the above-mentioned study indicates that with a minimum of 12% grid forming inverters, everything else would run with grid-following inverters.
That being the case, AEMO could consider a very much different renewable electricity system for Australia, one where reliability on ‘transition only with transmission’ would be revised to ‘home-grown transition with existing transmission’. Right now, that would be considered ‘crazy-brave’! There is no doubt that currently ‘tinkering’ is the preferred option in distribution networks and that ‘rewiring the nation’ is focussed on long transmission lines to remote renewable energy zones.
If instead of fearfulness of ‘crazy-brave’, we contemplate the uniqueness of Australia in respect of household and business solar penetration in the national electricity system, we would find legitimate grounds for rethinking the entire system.
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As an example, a serious study could be commenced in making distribution networks independent of transmission, therefore considering models with large capacity battery storage systems and grid forming inverters at terminal stations, rather than at the far end of transmission lines. The abovementioned studies in the USA would ‘gird our loins’ in the validity of the endeavour.
We might well enhance reliability by prevention of concatenating grid failures typical of interconnected grids, and yes, it would in addition to changes in electrical engineering, require rethinking of market mechanisms and the roles of the Australian Energy Regulator and Australian Energy Market Commission! But that wouldn’t presage the end of the world—rather we would be utilising ‘here and now’ technologies to visualise a new energy world. And that’s not crazy-brave; that’s sensible!
