Remote control

New rules allow the market operator AEMO to remotely disconnect rooftop solar systems when they deem it necessary to preserve system security. AEMO wielded this power for the first time last weekend, when a sunny day coupled with moderate demand drove SA demand to a dangerously low level. Low demand is a problem because it leaves no room for synchronous generators to run even at minimum levels to keep the system’s frequency fine-tuned. Sunday’s demand dip was not a new record, but the situation was exacerbated by the limits on exporting surplus generation into Victoria, as reported in a recent blog. Are these rules fair on solar owners, and now they are being put into practice, will they be politically sustainable?

Let’s look at it first from a system perspective: AEMO is able to manage a system built from generation and networks with multiple owners and operators each acting independently because it has two things: visibility and control. It does this through SCADA installed at each large generator so it has a real time view of their output. Similarly, it can see what’s happening across the high voltage transmission networks (but not yet distribution networks). It issues dispatch targets for every five minute intervals. It has powers to direct generators up down on or off under fairly clear protocols for when it can do so. While it doesn’t physically control generation, there are strong penalties for failing to comply with AEMO instructions so it’s a pretty robust form of control.

Solar advocates are proud of pointing out that rooftop PV is in aggregate “the biggest power station” in each state. Imagine how risky it would be for the system if AEMO had no visibility or control over the output of Torrens island, Loy Yang A, Eraring or Stanwell! Yet this has been the case up until recently. There are a few outfits who use various means to estimate rooftop solar output, including AEMO, but there is an obvious margin for error here. And until the new rule came in there was no way for AEMO to get rooftop solar turned down or off in those cases where it would be the best way to secure the system. The new rule, based on a South Australian government initiative called “smarter homes” established a network of agents who interact with solar customers and who can respond to a call from AEMO to implement a PV shutdown. For AEMO this is a useful step forward, albeit it is only applicable to new installations, so only a subset of the overall rooftop capacity is controllable in this way.

From the perspective of rooftop PV owners, it’s less obvious that it’s a good idea. Some new solar owners ae already dealing with static export limits – where the local distribution network considers it will be overloaded by solar exports it can put a limit on how much new installations can export their surplus PV. The Smarter Homes initiative is a step further still. Analysis for Energy Consumers Australia ranks both of these polices as having high effort to obtain and maintain social licence, due to their high cost for PV owners and low options for opting out of them.

Figure 1: Costs and efforts of maintaining a social licence for DER control programs


Source: Social Licence for Control of Distributed Energy Resources, Cutler Merz, December 2020

Some consumer advocates argue that this approach is unnecessarily heavy-handed and fails to take account of what is already happening in the market. They point out the risks of applying this same approach to turning off household’s aircon on a hot day. The clean energy sector points out that Smarter Homes require a specific type of smart meter even though some inverter models can probably do the same thing. This requirement adds extra costs. The more this power is exercised the more solar owners will get frustrated with their lack of control over an asset they paid for (well with a little help from the subsidies).

Policy makers point to the post 2025 market design project and suggest that will deliver an enduring solution, suggesting this command and control approach is only a stopgap. But as every family knows, the person with the remote control in hand is usually the one who decides which channel to watch and is reluctant to give that power up.