Nowhere in Australia has wind energy had as much of an impact on the existing electricity infrastructure as in South Australia. According to the latest figures from the Australian Energy Market Operator, wind energy accounted for more than 22 per cent of capacity and 20 per cent of supply over the past year – although it has been higher over shorter periods – and at times supplied more than 80 per cent of the state’s energy needs.
The fact that wind energy, once built, supplies energy at near zero marginal cost and lowers the wholesale price of electricity has helped push more expensive fossil fuel generation out of the system, which is why fossil fuel generators are keen to reduce the extent of the renewable energy target. In South Australia, it has forced the closure in winter of the two local coal-fired generators that once supplied nearly one-third of the state’s needs.
Wind energy, though, is challenging to manage. Wind energy is variable and not always blowing at times of peak demand. The good news is that it can be quite predictable, and the more that is put up across different regions, the less variable it becomes. And grid operators are used to dealing with variable demand.
South Australia has one of the highest penetrations of wind in the world, and accounts for around half of the wind energy installations in Australia. This graph from AEMO’s latest study into wind generation in South Australia shows how it has grown over the last five years.
The South Australian wind energy report released by the AEMO today is part of its ongoing study of the impacts of renewable generation, and will help inform its analysis of how Australia can install a 100 per cent renewable grid. Even before the country gets to 100 per cent renewables, however, the grid operators need to learn how to manage large amounts of wind and solar. Given that Australia could be headed towards 25 per cent of renewables by 2020, these are lessons that need to be absorbed fast.
One of the key findings of the report is that South Australia is not a highly interconnected system, and the full benefits of wind energy cannot be exploited until the interconnector with other states is upgraded. This graph below highlights the variability of wind, and compares it to variations in demand.
Variations in the load can be dramatic – one occasion being 545 MW in a 60 minute period. The largest variation in a five-minute period was a decrease 294 MW. “Such large short-term fluctuations in wind generation are challenging for power system operation, as system reliability needs to be maintained including sourcing alternative generation at short notice,” the AEMO notes.
Another interesting graph is this one that shows the “negative price” events in South Australia over the last few years. Negative price events occur when there is too much supply and not enough demand. They are not unique to wind because they occurred before the construction of wind farms, but their occurrence has become more frequent. In the case of the South Australia, this could be an argument for increasing the size of the interconnector with the other eastern states – thereby creating the market for the excess wind supply – or adding some sort of storage mechanism, as they are doing in King Island.
The other thing to note from the graph is that negative price events do not only occur at night at times of low demand, there are many such events during day-time and even peak periods in the afternoon. On that subject, it is worth looking at the three graphs below, which shows the differing outputs from various regions. Geographic diversification is seen as quite critical for renewables, given wind doesn’t blow and the sun doesn’t shine at the same place all of the time, which is why the Europeans are pushing for the establishment of a “super grid” that will use renewables from different regions to balance supply. European grid operators are currently signing a whole bunch of contracts for sub-sea cables that will form the basis of that grid.
In South Australia, the south-east region, these graphs below show, actually delivers more wind energy in the afternoon periods than it does at other times. The increase in the spread of turbines has meant that AEMO has nearly trebled its “peak rating” of wind turbines in the last few years to 8.5 per cent. This is expected to increase over time. And if there is a lesson from the german experience, it shows that more solar will dovetail nicely with wind generation and demand – although for the coming decades there will be significant gaps to be filled by fossil fuel generators or storage options.
The first graph is for the mid-north region, north of Adelaide, which has around 618MW of installed capacity. The second region, coastal peninsula, takes in the 325MW of wind power located on the Eyre, Yorke and Fleurieu peninsulas, while the south-east refers to 192MW of wind energy installed on the coastline near the Victorian border.