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  • Writer's pictureGeoff Russell

Big Coal isn't as big as it used to be!



RenewEconomy recently ran an interesting article with an amazing headline: Cannon-Brookes backed fund to deliver "coal plant-worth” of big batteries”.

The article mentioned the following small and very small battery projects:

  1. The Capital Battery, 100MW/200MWh at Queanbeyan,

  2. The Bouldercombe Battery, 50MW/100MWh at Rockhampton,

These were said to be the first of 6 to 8, totalling “1.5-2 gigawatt (GW)” according to one Alexander Austin, of financier Infradebt.


Oops!


I certainly hope Mr Austin knows more about finance than batteries.


You can easily pick people who haven’t got a clue about batteries when they cite a single number to specify the size.


In this case, Mr Austin used “GW”, a measure of power; which tells you nothing about how long that power can be provided. That’s pretty important. Missing it is like telling somebody that their finance payments will be $2000 per month, without telling them how many months they’ll be paying this.


A 2 GW coal plant can provide its power for as long as you shovel the coal in. That’s why people only use a single number for coal plants.


Now, as you can see from the Capital and Bouldercombe batteries, the journalist, Sophie Vorrath, rightly provided two numbers. The first gives the power and the second the energy, which effectively tells you how long the power can be provided. In both examples we are talking about batteries which can provide their maximum power for 2 hours. Is that as long as a coal plant can provide full power? Not quite.


I’m a little surprised that Vorrath didn’t correct or quiz Austin to provide the missing information. Maybe she was just working from a press release. Who knows?


As it stands, the two batteries are a long way short of being a “coal plant’s worth”. What exactly is a “coal plant’s worth”?


Most of Australia’s remaining coal plants are in the range of 1,000-3,000 MW, with a few smaller ones. The biggest is Eraring at 2,880 MW in NSW. A plant is typically made up of multiple turbines. Eraring has four. Gladstone has five, but each is somewhat less powerful.


Let’s think about what a coal plant’s worth of batteries would look like.


Firstly, batteries generate zero energy, so you can’t replace coal plants with them without also providing something to charge them. That may seem like a “small” point, but it isn’t. If you read my post on grid congestion, you’d realise that the power to charge the batteries should be close by. Theoretically, you could charge a battery in Victoria using solar plants in Queensland, but that’s rather unlikely without even more of an overbuild of transmission capacity than is already being planned.


Let’s think about a 2 GW coal plant. Let’s think about how big-a-battery you’d need to get you through a windless night. We’ll think about 12 hours just for the sake of being clear. In reality, you’d need more than this, because a few still days in a row might see you start the night shift in less than a fully charged state.


Over a 12-hour night, a 2,000 MW coal plant can provide about 12 x 2,000 = 24,000 MWh of electricity. Switching to gigawatts (GW), this is 24 gigawatt-hour (GWh).


So if your batteries can’t at least provide that, then they won’t be a “coal plant’s worth”, obviously.


You could do this with 12 x 2 GW batteries with 1-hour capacity each. Meaning they were both 2GW/2GWh batteries. As each became exhausted, the next would take over. By the time you get to battery 12, the first battery might even be charged a bit. But as my congestion post showed, it might not have much. Alternatively, you could opt for 6 x 2 GW batteries with 2 hours of storage each, meaning each battery was 2 GW/4 GWh.


As it stands, the Capital and Bouldercombe batteries will provide just 0.3 GWh of that 24 GWh; meaning they need another 79 pairs of such batteries.


Will the other 6 to 8 projects be 10 times bigger than this pair? I’m guessing they won’t.


In the world of marketing bullshit, battery marketing bullshit stands out as one of the biggest and steamiest piles. Hook up a methane generator to it, and you could probably provide a coal plant’s worth of power!


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