Syncing to new heights

22 December 2020



We’ve set a new record in Tasmania: powering over 80 per cent of Tasmania’s demand with non-synchronous energy sources.

 

If you don’t yet know what that means, it’s okay! Power grids are complex and rely on the laws of physics, which most of us don’t even remember from high school (and it's a fair bit more complicated than that). But this short explainer will show you why this record is worth celebrating and why it makes Battery of the Nation so important.

 

First, you may have heard recently that with the construction of new windfarms, Tasmania is now able to generate 100 per cent of its own energy needs from renewables. That’s true, but for the purposes of running a large and stable power grid, there are two broad categories of energy sources.

 

Synchronous and non-synchronous energy sources

Our national power grid will remain stable when there is a balance between supply and demand. Just like a see-saw, if an oversupply of energy occurs or demand exceeds supply, the grid will become unbalanced. At worst, this could lead to power outages or even major blackouts. So for example, when everyone turns on their air conditioners during a hot day, power generators and transmission operators must be ready and able to respond.

 

Traditional energy sources like coal and gas power stations convert energy into electricity through large spinning turbines. The speed at which they spin is 'synchronised' to the grid, which acts to keep the grid stable. Exactly how this is achieved gets complicated, but it involves the magnetic configuration of each turbine and their spin matching the grid's frequency. The important thing to understand is that having a lot of rotating mass - synchronous energy sources - in the power grid acts like a shock absorber for changes in supply and demand, which helps to keep our lights on! 

 

Infographic explaining - synchronous and non synchronous energy generation

 

On the other hand, non-synchronous energy sources provide output levels that are constantly changing based on conditions, like wind and solar. So before these sources can be connected to the grid, they pass through a 'converter' to change their output to match the grid's conditions. Even Basslink’s high voltage direct current transmission (HVDC) must first be connected to a converter before joining Tasmania's power grid. These non-synchronous sources cannot provide the power grid with the same levels of stability.

 

Keeping the grid stable

If you managed to grasp all of that, you might now be wondering what will happen to Australia’s power grid as our synchronous coal-fired power stations retire. We know Australia has to reduce its carbon emissions, but without synchronous generation providing stability for the power grid, we are risking more blackouts and threatening Australia’s energy security.

 

This is the dilemma being faced around the world as every country considers how best to adapt existing systems to a low-carbon future. It’s why critics of renewable energy claim you cannot replace fossil fuels. They say it’s impossible to run a stable power grid that is mostly renewables. And as more wind and solar join Australia’s grid, there have been concerns about what will happen when non-synchronous generation eventually comprises the majority of the National Electricity Market.

 

But there are existing technologies that can address this problem and provide stability. Batteries are one option (more on those in a moment). And of course there is also a synchronous energy source that happens to be renewable: hydropower.

 

A new record

Between 1-1:30 pm on Sunday, 13 September 2020, over 80 per cent of Tasmania’s energy demand was met with non-synchronous energy generation. This is a record for Tasmania.

 

That energy was coming from a combination of local wind farms in Tasmania and Basslink imports, while hydropower provided the synchronous generation needed to stabilise the grid. In fact, at this time we were spinning six of our large turbines ‘on empty’ with zero output, just to provide that stability.

 

One important point about Basslink: we were importing a large amount of energy from Victoria at this time because of the wholesale pricing in the National Electricity Market. As always, pricing follows the laws of market economics – supply and demand – and during that Sunday afternoon Victoria had an oversupply of wind and solar energy, which temporarily sent their price negative. This means they were actually paying other states to use it, in order to keep their own power grid stable.

 

While over 80 per cent is definitely a new record for non-synchronous generation in Tasmania, it may also be a new world record. Confirming these figures is difficult when trying to compare similar results from complicated power systems around the world. Regardless, this achievement shows that it is possible to operate a large stable power grid that is mostly powered by renewables.

 

Battery of the Nation, for the nation

The variability of wind and solar will always affect wholesale energy prices, but storing that available energy will also become increasingly important. Batteries will be a much bigger feature of Australia’s future power grid. They are available in different sizes and are always getting cheaper, but they cannot do it alone. Australia's power grid has a very big change coming. We’re going to need every available technology to meet this challenge.

 

Battery of the Nation's pumped hydro is just another form of energy storage and Tasmania’s topography makes it ideal for storing massive amounts of energy, which you might hear called 'deep storage'. When energy prices are cheap due to an oversupply, we can use that energy to pump water uphill into a reservoir, then release the water downhill into synchronous turbines when the energy is in demand.

 

Battery of the Nation isn’t just a catchy name. Tasmania is going to be an essential part of Australia’s future energy needs, because only synchronous hydropower can provide stability in a grid that is mostly renewables. With more interconnection through the two proposed Marinus Link cables, Tasmania can both supply and help stabilise Victoria’s power grid.

 

And all according to the laws of physics and market economics, which helps to deliver both stability to the national grid and revenue to the owners of our hydropower system – Tasmanians.

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