The impact of nuclear generation will be felt at home

Interview with Allan O’Neil, Independent Energy Market Consultant

Following last month’s ‘What would nuclear energy mean for your solar panels?’, Village Power interviewed Allan O’Neil, independent energy market consultant, to gain an understanding of the mechanisms of curtailment of domestic solar panels. Alan explains what curtailment is, how it works, when and why it happens, and the impact on rooftop solar owners.

Village Power: Thanks for joining me. Readers of the Village Power newsletter are keen to understand the actual mechanisms of curtailment of their solar panels should Australia adopt nuclear energy. Let's start with your background and then move on?

Allan: My first degree was in mathematics and physics which led to my first job in the public service. Following that I worked  in the private sector. I completed an MBA, and then in the mid -1990s, moved into the energy market at the time the SEC was being privatised and split up. By the late 1990s, I was working in the National Energy Market, mostly in the commercial market doing modelling. Since 2014, I have been freelance consulting in the energy market, working with clients who want to understand how the energy market operates. It's the evolution of the market that keeps me involved.

VP: I understand that each state has a different way of dealing with excess solar and different ways of curtailing solar.

Allan: Yes. We are already running into problems with the current system. There's roughly 25GW of rooftop solar capacity in the system - that's 4-5 million solar systems - and this exceeds the maximum capacity of all the coal-fired generation in the market at the moment. The biggest single source of power in the grid is rooftop solar and sometimes that can meet 55% of our total electricity consumption which only leaves 45% to be supplied by other things such as coal and large scale wind or large scale solar. Large scale wind or solar can be scaled down but not rooftop solar. Coal-fired can reduce but only so far. It can reduce to about 40-50% of its capacity but then hits a floor because these plants can't be turned off completely and then restarted quickly.

VP: So there's a significant issue if nuclear were to replace coal?

Allan: Yes, Nuclear doesn't have the same flexibility as coal. Coal can be scaled down to 40% but nuclear to only 70% at a stretch. If we replace coal with nuclear, we will have less flexible large-scale generation than we do at the moment. And people aren't stopping installing rooftop solar on their houses. If growth continues, and we move to less flexible, large-scale generation, something has to give so that's, in a nutshell, the issue.

VP: Will curtailment be a problem everyday?

Allan: No, that won't happen every day. On hot summer days the system wants all the power it can get from rooftop systems. In winter time, rooftop solar isn't putting out as much, and demand is higher in the winter so that's not a problem. It's the shoulder season - mild sunny days - where we get a “minimum demand” problem but really it's an inflexible supply problem.

VP: So regarding the actual process of curtailing solar - what is that mechanism? And what will be the impact on the rooftop solar owner?

Allan: That depends on where you are. That mechanism is already in place in South Australia. If you have installed a new system there, in the last couple of years, it has to come with a capability that allows it to be remotely controlled. That means in some cases it can be turned off, in other cases, it can be set so that it doesn't export any power to the grid and just matches what your household uses. Both of those things are there because SA's got more rooftop solar relative to its population than other states. At times rooftop solar in SA can produce enough to meet the state’s whole demand and the reason that it can do that is that the excess can be exported to Victoria. There's been a handful of days where SA has had so-called negative demand, meaning that no large-scale power is needed because rooftop solar is doing it all, and the excess comes to Victoria.

VP: Is that the same for Queensland?

Allan: The different states are introducing controls at different rates. Queensland has taken some steps toward rooftop solar being controlled by the distributor. The concept in Queensland is again, if you are installing a new system, the distributor will have the ability to press a button in their control room and reduce the output of your panels or turn them off so they are not exporting to the grid. Queensland is not talking about retrofitting that capability.
In Victoria, control is a real issue. Everyone's very aware of it. There are steps being taken to give the distributors the ability to control output as a last resort, following the lead of South Australia and Queensland.

VP: Does that mean the distributor can 'up' the voltage to trip people's inverters?

Allan: That was the initial approach in SA but it is a very crude approach and not one that the  States are seeking to introduce generally.

VP: So, how, here in Victoria, would our rooftop solar be limited or turned off?

Allan: Well following the SA example, your inverter has an internet connection - probably wifi to your home router and that's able to receive a signal over the internet - that of course depends on your wifi being up and running. About 80% of systems installed since these requirements came in would respond to an instruction - the other 20% covers the fact that you might be away and have turned your wifi off or lost connection. But the concept is that it's done by a signal over the internet. The so-called voltage management is there as a last resort but it's not the way anyone wants to go. Queensland has taken a different approach again, with the distributors controlling recently installed inverters via signals carried on the powerlines themselves.

VP: When this happens, it prevents you exporting to the grid but does it also turn off your capacity to generate power for your own use so that you then have to buy from the grid?

Allan: The preferred approach, if your inverter is supported, is to just turn off exports to the grid so you can still consume your own solar and don't have to buy from the grid. However some models of inverter might not have that degree of control because that requires the inverter to be intelligent enough to turn off exports and balance what the solar panels are producing to the needs of home usage. Some inverters may not be intelligent enough to do that and can only be turned off.

VP: Is it possible to upgrade your inverter?

Allan: Yes, but the question will be, 'Who Pays?'

VP: One last question, who exactly has the ability to instruct your inverter?

Allan: It is typically the distributors like Jemena or Powercorp that press the button, but the instruction comes to them from the market and system operator, the Australian Energy Market Operator (AEMO).

VP:  Thanks for your time, Allan. Our readers will be very interested in what you have had to say and you have cleared up a number of questions that are on people's minds.