AEMO explains caution on S.A. wind: We’re first in the world

One of the first fund managers to specialise in clean energy and ethical investments in Australia used to explain the challenge of his job like this: “It’s great to be ahead of the pack, buy you don’t want to be too far out front.”

It appears that the Australian Energy Market Operator has adopted a similar view. In explaining its recent caution on South Australia, and new rules that require new levels of gas generation, AEMO says South Australia’s grid is the first first large-scale power system in the world to deal with minimum quantities of synchronous machines.

In a new report explaining its actions, AEMO compares South Australia with other countries with high wind penetration – Denmark, Germany and Ireland, as well as the US state of Texas.

It says the penetration of wind in South Australia – 120 per cent of demand  on occasions – is far beyond any other, particularly those in “isolated” grids like Ireland and Texas.

And it uses this graph below to illustrate how. (The big blue bar indicates the maximum penetration of wind in the local grid).

The implication is that AEMO – much like the rest of the industry – is forced to learn as they are going along. And because it has the ultimate responsibility of keeping the lights on, and got a B minus last summer, the grid operator is taking an ultra-cautious approach.

In early July, AEMO began implementing new rules that require a minimum about of gas generators to operate at all times, and at least four to operate when the wind output goes above 1200MW (although that can vary depending not the characteristics of the plant available).

If they don’t get that number of gas turbines, then wind will be curtailed back to 1200MW. It’s already happened on several occasions in the last two months, most notably earlier this week when the 1700MW of wind farms had their output clipped for three days running, delivering this extraordinary vision below.

The move has caused surprise in the industry because it was unexpected, does not relate to the common issue of frequency and inertia, and was not directly prompted by the high profile “system black” last September or the equally controversial load shedding in February.

AEMO says it is an issue about system strength, which it says it is weakened by the lack of “synchronous generation”.

But many in the renewables industry think it’s a pretext for papering over some of the deficiencies in the state’s gas generators, and issues elsewhere in the network. In other words, they suspect that the issues would have emerged whether wind was in the system in great quantities or not.

AEMO is citing November 13 as the day of its epiphany about system strength. Nothing much happened that day, except that South Australia had a high level of wind generation, but only one gas unit from AGL’s Torrens B facility operating.

AEMO says the grid performance that day was satisfactory, but apparently it was spooked by what might have happened if that one unit tripped.

It deemed the situation to be “insecure”, and sought ways to boost “system strength” by having a minimum amount of “synchronous generators” – which in South Australia means gas-fired units.

Indeed the new rules, which were explained to industry participants in a telephone hook-up on Friday morning, after the release of a paper on Thursday, appear to be designed to protect the system in case of an unexpected outage of one of the state’s ageing gas generators.

Since the state-wide blackout there has been a increased focus on the performance of old coal and gas generators, and the so-called governor controls, which dictate how quickly the big synchronous plants can respond to system faults.

There is widespread concern, identified by the wind industry and echoed in the Finkel Review, that lax governor controls are weakening the strength of the grid and its ability to respond.

One observer said that if system strength  was such an issue, then why wasn’t more made of it in the study into the blackout. There is a suspicion that the issue is in fact related to the ability of gas generators to manage frequency and inertia, and their ability to do so may not be as strong as is assumed.

The impacts of the new rules imposed by AEMO will be several:

One, the need for multiple gas generators to be on line at times of high wind generation means that the wholesale price of power in the state will not fall as it usually does when there is a lot of wind. The price will continue to be set by gas, and that means it won’t fall far, barring constraints that stop exports to Victoria.

It also means that excess wind output – above 1200MW from the state’s 1700MW wind farms will be constrained, as has happened on several occasions already since the rules were first imposed in early July.

And it could have impacts on future installations. Already, a new 220MW solar farm is being built near Port Augusta and a new 215MW wind farm will follow soon. Numerous other large scale wind and solar projects are planned.

(It may at least partially explain the state government’s increased enthusiasm for hydrogen technologies to use the excess output from wind and solar farms. It announced a new tender today).

In its paper, AEMO says it will continually review its needs, and its modelling, and the new rules, to take into account any new installations and the emergence of new technologies, or the prospect of using existing technologies like synchronous condensers.

And it promises to be a vigorous debate, at least behind the scenes. There are strong differences of views about the fine details of electrical engineering and how it should apply in this situation – not surprising given the system is moving into virgin territory.

But the one aspect that frustrates many is the lack of independent engineering review – for the moment, most positions are coloured by the respective world views on variable renewables and traditional generation. It promises to be an issue of culture as well as technology.