Rooftop Solar Kill Switch, or Sometimes the Sun Shines Too Much

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As Australia adds massive amounts of rooftop solar power per year, the discourse is turning from: “we need coal/nuclear because there isn’t enough solar to feed into the grid” to “we need to switch off solar to preserve grid stability.” The point is, though, that we do, but only as a last resort. It is easier to curtail a solar farm and “spill” the excess than to stop and restart a coal-fired power station or a nuclear reactor. Happy to be corrected if I am wrong. It isn’t just FUD or gaslighting. Curtailing of solar farms is already occurring, mainly due to the inability to export excess solar if not tied to a battery storage system.

So, in Australia, we get the irony of headlines that say “Rooftop solar provides 107% of grid demand in South Australia” juxtaposed with “Rooftop solar emergency powers needed. Shut off the rooftop solar!” All this while the costs of building out large-scale solar is falling – at about 8% per year. Some are even suggesting that Australia encourage local production of solar panels in competition with China. No thanks, we have had a trade war with China and it came off badly. We’ll take the inexpensive Chinese solar panels and value add, like what Volt Solar Tiles is doing.

Recently, PV-Tech reported that South Australia achieved over 100% of electricity from privately owned residential rooftop solar. “According to OpenNEM, at around 13:45 on 17 November, rooftop solar PV in South Australia provided 107.5% of the state’s demand, standing at around 1,720MW.” South Australia has wind farms and commercial solar farms as well, it should be noted.

South Australia aims to be running totally on renewable energy by 2027 (that’s not very far away). The only thing slowing things down is the ability to export excess power. 10 years of conservative pro-coal federal governments slowed the development of interconnectors between the states. That situation is being rectified.

The irony is that subsidies for rooftop solar were brought in by a conservative government 25 years ago. But, then, further conservative governments have tried to slow the transition. Unintended consequences. Who knew that average Australians would like to generate and consume their own power rather than pay excessive fees to national generators. Is it the little Aussie battler vs. the ogres of enterprise? Feels like it sometimes.

The Australian Broadcasting Commission (aunty) is now highlighting the fact that in extreme circumstances, the Australian Energy Market Operator (AEMO) would like to turn off your rooftop solar in order to protect the grid. They are calling this an “emergency backstop.” Despite the fact that this article emphasises “emergency,” many have taken to their keyboards to express their displeasure of government interference in their lives. Is it big business pushing out the little guy?

I think not — the key word here is “emergency” — when there is so much rooftop solar in the system that it is threatening to overload the grid. It’s hard to appreciate just how much rooftop solar can be generated at times in Australia. Better to turn it off than to end up with a blackout. Since 2010, Australians have installed over 22 GW of rooftop solar. On a good day that is really going to pump out the electrons.

Solar has the potential in Australia to destabilise the grid. On its own, it does not provide the inertia needed to maintain stability. A notable omission from the ABC report is batteries. They have been shown to provide such inertia. “Coal, gas, and hydro plants provide this inertia through their turbines, helping keep the grid steady and maintaining consistent power levels.” So do batteries like the Tesla Big Battery (Hornsdale Power Reserve). South Australia is exploring other options to balance the grid, including the creative use of hot water systems. CleanTechnica published on that here.

I am told by those in the industry that many rooftop solar systems now being installed are being paired with home batteries. The next level up are community batteries. ARENA is funding 370 of these with an aggregated capacity of 280 MWh. Every week comes announcements of the “newest” “biggest” battery to be built in Australia. Pilot projects throughout the country will provide solutions to the need for grid stability. That way, homeowners will still get access to their own, cheap electricity. This situation will improve even more as EVs get to be used as batteries on wheels. So, batteries of all sizes will minimize the need for a “kill switch” in rooftop solar. Emergencies will be minimal.

One cannot fail to see the parallels between the need for “emergency backstop” provisions because of failure to foresee the consequences of subsidised (and now cheap) rooftop solar and the current crisis in the car industry. It is another strategic planning failure. With the rapid deployment of rooftop solar, it should have been apparent, at least, 5 years ago. But with the feral government dragging their feet and supporting coal, it was difficult for the states to move. Things are improving now.

Australia’s planners need to move beyond the past. I guess we are involved in “action research” — trying things out, discovering new ideas, and coming up with new uses for batteries (such as using them for synchronised condensers).

How would AEMO implement this “emergency backstop?” In the words of one of my correspondents: “There exists a gulf between what they want to do, and what they will be able to do in either a technical or multilateral regulatory sense, not to mention the backlash from what is a huge consumer cohort.

“Firstly, technical changes would only pick up new installs in regulated areas and any retrofits, even if mandatory, would take years and perhaps be compensable. On a regulatory front, harmonised powers might need legislative intervention, and if hugely unpopular with enough voters, may get scuppered there. Further to that, the time involved often sees technology advances or new products that work around or obviate the need for such a clumsy administrative solution to what, to my ignorant eyes, essentially seems to be a complex engineering problem.”

Another correspondent chimed in: “I think it’s been hugely socially progressive that in the twentieth century we engineered power grids that provide cheap reliable power to all, at the same cost. This is arguably the single most important thing ever done for human wellbeing.” He added that energy generation from renewables is “inherently messy,” with too many unknown unknowns. An open futures research question perhaps. The crystal ball is foggy and the technology is evolving rapidly. How much of our grid architecture and regulatory management is obsolete? “We can’t just pull a new continent scale design out of our backside here; we’re going to have to incrementally muddle through challenge by challenge.”

We still need the grid. We will still need an emergency cut off switch. If solar generation is in excess of consumption and cannot be exported to the grid, unscheduled blackouts and network failures will be the result as breakers trip. Yes, all this would have been easier with better strategic planning and futures research, and, yes, successive Australian federal governments have obfuscated and delayed. However, this is where we are and we have to deal with it.

In Australia, the future is bright, electric, renewable, and a little difficult to navigate.