It seems I keep stumbling upon hooray stories about Australian grid batteries. I found this reneweconomy article about a new Tesla battery that will be built in New South Wales. The article is titled “Transgrid to build Australia’s first Tesla Megapack big battery in western Sydney” and the author is Giles Parkinson. I remember him from a cheering and one-sided article about the Hornsdale Power Reserve and this article seems not much different.
The first paragraph provides the crux of the story (my emphasis):
Transmission company Transgrid is to build the first big battery in Australia using Tesla’s recently introduced Megapack battery technology, and what is likely to [sic] the first of more than 10 big batteries to be built across NSW as it they are important in face of the looming retirement of its ageing coal fleet..
A new big Tesla battery will be built, this time in New South Wales and likely 10+ big batteries will follow. More, these batteries are built in preparation of the retirement of the New South Wales coal power plants over the next 10 to 12 years…
This all sounds pretty impressive, but I wonder what order of magnitude we are talking about here.
It must be pretty large batteries to have an impact after the closure of the New South Wales coal fleet. The first one to be built is the Wallgrove battery (my emphasis):
At 50MW/75MWh, the Wallgrove battery will be the second biggest in the country – after the highly successful first Tesla big battery at Hornsdale in South Australia that delivered 100MW/129MWh, and was recently expanded to 150MW/194MWh.
A capacity of 50 MW able to store 75 MWh? That is quite underwhelming… That is indeed only half the capacity of the original Hornsdale Power Reserve (before its upgrade).
To be fair, the Wallgrove battery is only the first of more than 10 batteries to be built (as in the first quote) and another half a dozen still in proposal state (my emphasis):
The NSW state government is also providing funding for another half a dozen big battery proposals, and numerous other developers are talking of adding big batteries at existing wind and solar farms. Transgrid also says it is looking for more big battery proposals from third party battery providers to install across its network.
In another article on these batteries it was mentioned that there were 1 dozen scheduled batteries and half a dozen proposed. So let’s take roughly 18 batteries that are in the pipeline. It is mentioned later in the article that one of these batteries will have a capacity of 500 MW.
What will be the function of these batteries?
In a later statement, Transgrid provided this explainer:
“The power system currently relies on inertia provided by large spinning turbines inside coal, gas and hydro generators to maintain a consistent frequency and help the system ride out any disturbances. As coal-fired generators retire and more wind and solar generation connect to the grid, alternate sources of inertia will be needed to stabilise the network.
That is where the batteries come in. They will provide fast frequency response and inertia services. This is not really a big surprise, batteries are especially well equipped for fast frequency response and, looking at the situation of the Hornsdale Power Reserve, they can make quite a buck providing these services to the grid.
The need for such services originates from the migration to intermittent power sources. On the one hand, adding more intermittent power generators to the grid means that variability of electricity generation will increase and fast frequency response services are needed to balance the system. On the other hand, removing dispatchable power generators will decrease the amount of inertia available on the system, therefor making it less stable. Retiring coal power plants will therefor make the grid less resilient against network failures. That is why the article acknowledges that these two issues are major problems that need to be tacked when making the switch to wind and solar.
That is however only part of the story. Remember, those batteries will only tackle the problem of the instability of the grid caused by adding intermittent power sources to the grid and the removal of dispatchable power. It doesn’t tackle the loss of backup capacity when there is no sun and no(t much) wind. This backup is provided primarily by coal. This is the fuelmix summary from the AEMO dashboard of the last year:
The share of coal in the fuelmix is 86%! That is a lot to replace in just 10 to 12 years. Just a back-of-the-envelope calculation. Demand in New South Wales is around 70 TWh per year. If New South Wales is somewhat import/export neutral, then this would mean that 60.2 TWh of electricity is provided by coal. That is on average a capacity of 6,872 MW. There is no way that those batteries can provide significant backup capabilities to replace this amount of electricity, even when 18 of them are built.
How much electricity do these 18 batteries put on the grid? Let’s do another back-of-the-envelope calculation. The batteries will have the same function as those currently in South Australia. When working on a previous post on the batteries in South Australia, I downloaded a year’s worth of data on the fuelmix in South Australia back then (data of the week of 2019-08-31 until the week of 2020-08-29). Batteries discharged in total 12,484.98 MWh during that year and the total capacity of the South Australia batteries then was 155 MW. Let’s now assume that New South Wales will have 17 batteries similar to the Wallgrove battery and one of 500 MW, then this means a capacity of (17 * 50) + 500 = 1,350 MW. If the New South Wales batteries discharge at the same rate as the South Australia batteries, then we are talking about an expected discharge of roughly 12,484 / 155 * 1,350 = 108,732 MWh. That is a whopping 0.13% of what coal produces now.
In a previous post, I found the idiom “as effective as a gnat peeing on a fire”, describing the (incredibly underwhelming) response of the Hornsdale battery to the failing unit of the Loy Yang power plant in 2017. I think this idiom is also appropriate here. Yet now we have, gosh, 18 gnats peeing on a fire! But hey, one of them is a really big gnat…
Trust, yet verify 
There is one undiscussed factor that really affects the use of batteries – what is the charge in the batteries when they are called on? If they are to be used for FIR, then they need to be near fully charged. However, that means they can’t be used for grid balancing, particularly when they have a shortage of generation. There have been unpublicised times when Hornsdale didn’t do much because it was near flat. Fortunately, the grid wasn’t relying on it. FIR is also to give you time for things like the fast start GTs to get on line. If you don’t have them, what do you have as reserves?
Whatever is the actions, there is one thing we know for certain. The Australian consumer will have to pay a lot more money for what will be a lower quality product.
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