Balancing the grid: How changing demand shapes our electricity supply

The reliability of Western Australia’s energy system, also known as the electricity grid, might not be something you’ve thought much about before - but with our changing energy landscape, keeping the supply and demand of electricity balanced is becoming even more important. 

Over each day, the supply and demand from our energy system fluctuates and the increasing prevalence of rooftop solar can make fluctuations more prominent. To keep the supply of electricity to WA homes and businesses as reliable and stable as possible, keeping supply and demand in the grid in balance is the key. Find out why reliability in the energy system is important, and what can happen when there is an imbalance in supply and demand for electricity. 

Why does the electricity grid have to stay in balance?

Synergy customers are connected to the South West Interconnected System (SWIS), an isolated energy system connecting electricity generators to customers.  Like balancing a set of scales, balancing supply and demand in the SWIS ensures that the electricity supply from generators meets the volume of electricity demand. If the amount of electricity generation doesn’t balance with demand, this can compromise the reliability of the grid, potentially leading to power outages. 

What happens if there is an imbalance?

An imbalance in the energy system can work in either direction. Depending on the conditions and times of demand, there could be either:

  • High electricity generation and low electricity demand
  • Low electricity generation and high electricity demand

Let’s look at the imbalance caused by high electricity generation and low electricity demand first. This situation is sometimes known as a low load event, and is often represented on a graph known as the Duck Curve.

This imbalance can happen at times when the amount of electricity used by homes and businesses is typically low and there’s large amounts of surplus electricity in the grid.  In the SWIS, this can occur when demand is low and large amounts of energy generated by roof-top solar PV systems is being fed into the energy system. This imbalance is difficult to rectify with traditional generation sources, such as power stations, as they generally can’t quickly reduce output or shutdown to meet the drop in demand. 

Now, let’s look at the imbalance caused by low electricity generation and high electricity demand. 

Imagine one of our hot summer days here in WA when everyone gets home from work or school and switches on their air conditioning, causing high demand for electricity. As the sun goes down, the generation from WA’s high number of roof-top solar PV systems drops away and the electricity supplied into the energy system from large generators has to rapidly increase.

Noting that the SWIS is an isolated grid (unlike the grids of the National Electricity Market that operates on the east coast of Australia), the Reserve Capacity Mechanism helps to ensure there is always generation capacity to meet peak demand. However, the challenges of ensuring there is sufficient availability of supply from generators to respond very quickly to manage the high variability of demand are increasing.

How do renewables impact grid reliability?

With more renewable energy in the energy system than ever before, the issue is becoming more complex to manage. 

If you have a roof-top solar PV system, unless you have a battery, you might source renewable energy from your system on sunny days rather than the grid:
Your roof-top solar PV system generates electricity from the sun's energy. 

  • Any excess electricity it generates that you don’t use when it is generated is sent to the electricity grid. 
  • When the sun goes down, most households like yours will then draw electricity from the energy system. 

Renewable energy is a more sustainable way of producing electricity, but the supply can also be less predictable than traditional generation sources. For example, the amount of energy a roof-top solar PV system generates fluctuates considerably when there is cloud cover. Imagine a suburb where most homes have roof-top solar PV systems; if cloud suddenly covers the area, all homes may need to draw electricity from the energy system at the same time. 

Solar batteries can help to store renewable energy from roof-top solar PV systems to be used later - but most battery technologies are not yet economically viable. This means that for the foreseeable future, traditional generation sources will still be needed to help meet demand and help keep the fluctuations in supply and demand in balance across the grid.

There are many other strategies employed by grid operators to keep supply and demand in the energy system in balance. 

How can supply and demand imbalances be managed?

Balancing supply and demand in the grid is an ongoing challenge - but it’s also giving rise to a range of innovative solutions. Here are some of the ways the issues associated with balancing supply and demand in the energy system are being managed:

To address high load:

  • Increasing generation – Some generators may be able to be engaged as needed provide extra generation capacity when demand increases.
  • Reducing electricity use during high demand times – Homes and businesses can adjust their use of appliances that consume large amounts of electricity, such as air conditioners, to use less during peak demand times. 

To address risks associated with low load events:

  • Use your solar generation: If you have a roof-top solar PV system, use as much of the electricity your system generates as you can during the day, for example by running your dishwasher or washing machine. This means the solar energy generated by your system is being consumed as it’s produced, helping to reduce your electricity use from the energy system and prevent excess solar energy being fed into the grid.

To address both high and low load situations:

  • Storing electricity – Synergy is trialling solutions such as the Kwinana big battery. Battery storage projects aim to help smooth the imbalance in supply and demand, where the batteries may be charged using renewable energy sources during the day to be used during the evening peak. 
  • Virtual power plants: With pilots such as Project Symphony, a collection of solar, small domestic batteries and other distributed energy resources can be aggregated and orchestrated to work together in a similar way as a traditional power plant.

A reliable grid for our intelligent energy future 

Reliability of the energy system is an important part of WA's intelligent energy future - and that future is already here. Find out more about Synergy's projects and trials underway including our Virtual Power Plant trial, Project Symphony.

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Synergy acknowledges the Traditional Custodians throughout Western Australia and their continuing connection to the land, water and community. We pay our respects to all members of the Aboriginal communities and their cultures; and to Elders past, present and emerging.