The heat is on: How does summer weather impact the energy network?

It’s that time of year when the days get longer, the temperature gets hotter and the weather gets wilder – and that means the electricity grid has to work harder. Here’s what you need to know about how summer impacts the grid, and how the market prepares for it. 

Summer brings with it a natural increase in energy consumption, as homes and businesses turn to air conditioners to help them get through the longer, hotter days. 

Summer in Queensland also comes with the risk of extreme weather events, like bushfires, floods and storms, that place further strain on the energy network.

That’s why ongoing maintenance and preparation takes place throughout the year to ensure the grid is ready to respond to the challenges of summer and provide the energy Queenslanders need. 

By popular demand 

If you’re reading this in the midst of a Queensland summer, then there’s a good chance you’re sitting in an air-conditioned space right now.

You’re not alone. According to the Australian Energy Market Operator (AEMO), peak demand – the time when demand for energy from the grid is at its highest – occurs in summer, driven by cooling loads. 

The one exception is in Tasmania, where peak demand is caused by heavy heater use in winter.

Traditionally, demand for electricity on hot days would peak around the early afternoon, when the temperature is at its highest. 

But with the rise of rooftop solar, demand for energy from the grid when the sun is shining in the middle of the day has gone down. Instead, there’s now a sharp spike in demand for energy from the grid in the late afternoon and early evening, when sunlight starts to dwindle at the same time many people are returning home from work and turning their air conditioners on.

In the years to come, these spikes in demand at the end of the day should be tempered by an increase in the uptake of batteries. Under the Queensland Energy and Jobs Plan, grid-scale batteries and pumped hydro storage will also help to flatten these spikes, as the grid progresses to the point where Queensland is no longer reliant on coal. 

But for now, baseload units powered by coal still provide the majority of the power in the energy grid. They run continuously, except during maintenance outages, but they can only ramp their production up slowly. 

That’s why flexible peaking plants – usually gas-fired generators – are called upon to provide supply when there’s a shortfall at times of peak demand. These peaking plants are expensive to operate, and typically only run for a few hours at a time, and some units only on a few days a year.  

Heatwaves – three or more days in a row of unusually high temperatures – are a particularly common source of stress on the grid in summer, especially as they roll into their third and fourth day. As heat accumulates in buildings, air conditioners have to work harder to cool them down, and that leads to an increase in energy consumption. 

Heatwaves have traditionally had the most impact on the grid from January to March. Because the National Electricity Market (NEM) is an interconnected grid, high demand in one state – or ‘region’, as it’s referred to for the purposes of the NEM – can usually be met by extra supply from another.

But in summer, multiple regions have been known to have heatwaves at the same time, which increases the pressure on the grid. 

High temperatures don’t just lead to high demand – they can also impair the operation of key electrical infrastructure. Generators, transformers, transmission lines, and even solar panels and wind turbines can all have their output reduced or cut off altogether as a result of heat-related stress. 

This reduces the supply of power when it’s needed most, and increases the risk of outages. 

To the extreme

It’s not just heat that impacts the grid in summer. Extreme weather events, such as bushfires, storms, flash flooding and cyclones can also damage transmission lines and disrupt the grid, potentially leading to power outages. 

This summer, Australians have been urged to prepare for potentially dangerous fire conditions. The Bureau of Meteorology has officially declared that both an El Niño event and a positive Indian Ocean Dipole (IOD) are underway – and together, these two climate drivers are expected to create hot and dry weather conditions over summer that will lead to an elevated risk of significant bushfires.

The Australian Energy Market Operator says it is preparing for levels of “extreme” demand in the coming El Niño summer, and is warning of the risk to supply should transmission lines and thermal generation fail in the hot temperatures, bushfires or storms.

“This year’s summer forecast is for hot and dry El Niño conditions, increasing the risk of bushfires and extreme heat, which could see electricity demand reach a 1-in-10-year high across the eastern states and in Western Australia,” AEMO head of operations Michael Gatt said in a statement.

How does the grid get ready for summer? 

If you’ve ever tried to ‘get fit for summer’ at the last minute, then you know that true summer readiness requires a year-round commitment.

Stanwell – Queensland’s largest energy supplier – manages its assets in a year-long program to ensure it’s ready for the peak demands of summer. That includes investing in asset maintenance, secure coal supply and climate resilience planning. This ensures its plants and its people are prepared to respond to the challenges of summer. 

Stanwell operates two of Australia’s most reliable and efficient coal-fired power stations – Tarong Power Stations near Kingaroy, and Stanwell Power Station west of Rockhampton. 

But that reliability and efficiency doesn’t just happen – Stanwell invests hundreds of millions of dollars into the maintenance and operations of these power stations.

That includes planned shut-downs of these stations to undertake essential maintenance and ensure they’re ready to go the distance during periods of peak demand. 

As a result, Stanwell’s coal-fired energy plants are operating at approximately 98 per cent reliability – the most reliable energy supply in Australia. 

In fact, every generating unit in every power station in the NEM is required by law to undergo a regular, scheduled maintenance overhaul, to ensure they’re ready to provide reliable supply.  

Planned outages are coordinated with AEMO more than a year ahead of their commencement to minimise any disruption to the grid. Internally, this early preparation enables generators to  accurately scope and plan the outage, and source any parts and resources required. 

It’s also important for generators to build up coal stock for summer. Stanwell owns the fuel supply at Tarong power station and has long term coal contracts in place for Stanwell Power Station. Stanwell continues to actively manage its coal stockpiles at the Tarong and Stanwell power stations, while delivering the generation required by the market. 

While there is always a chance that extreme weather events may result in fallen power lines, electricity networks have emergency crews standing by to respond in the event of equipment failure and minimise the time that people in the affected area are without power. 

So when that summer heat kicks in and energy demand increases, the grid is ready to respond – and you can kick back, relax and stay cool in air-conditioned comfort. 

Looking for ways to beat the heat? Learn how to save money on your summer electricity bill here.

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