Energy security relates to how the electricity grid or 'power system' reacts to events that may influence it. It includes the grid's capability to react and recover securely to major events such as faults or generation tripping, termed 'contingencies'.
The ability of the grid to respond to events and contingencies is termed ‘power system security’. Because the grid is balanced in real time – where the generation (supply) must equal demand plus any transmission losses – power system security requires all parts of the grid to work together. Ensuring that the power system is secure requires close monitoring and coordination, which is the role of the Australian Energy Market Operator (AEMO).
A secure energy system is of fundamental importance to modern economies around the world. Electricity grids everywhere are currently going through a technological transformation, driven by a move away from conventional gas and coal generation technologies to renewable energy and energy storage technologies. The objective of a transition towards renewable energy is to reduce emissions and tap into the competitive and energy independence advantages that come with using renewable energy resources. Of course, this objective has to be delivered alongside energy security constraints.
In Australia, more than 3 million homes and businesses already have solar on their rooftops, and investment in large-scale solar and wind farms dominates over conventional generation technologies. This new capability and capacity is coming online at a time when the National Electricity Market (NEM) is expected to deal with the withdrawal of many large conventional coal generators that have approached the end of their useful lifespan. Emissions abatement efforts are expected to accelerate these closures.
Emissions from Australia’s coal power stations also need to be addressed to ensure that we can meet our emissions reduction commitments.
|Average annual emissions from coal aged over 40 (tCO2e)
|% of electricity sector emissions from coal aged over 40
|Average annual emissions from coal aged over 50 (tCO2e)
|% of electricity sector emissions from coal aged over 50
The withdrawal of thermal generators has been occurring because they have been approaching the end of their useful lifespans. Closures of coal generation is expected to accelerate with international emissions abatement commitments. However, the amount of renewables currently deployed is less than the coal capacity that has been withdrawn, and investment in renewables needs to continue to replace these retiring coal generators. Australia should be embracing this change to secure a low-cost and reliable energy system as we transition towards a renewable energy future.
The volume and extent of change is enormous and requires a clear plan.
Synchronous generators have spinning magnetic fields that keep frequency close to 50 Hz. These magnetic fields are locked in synchronism across the grid, and synchronous generators rely on them to operate stably.
Non-synchronous generators are wind, solar and battery storage that use power electronics to follow the grid frequency in order to inject power into the grid, but can operate in a range of grid conditions.
Energy system reliability
Energy system reliability is ensuring that there is enough generation, demand-side and network capacity to supply customers with the energy they demand, with a very high degree of confidence.
Energy system security
Energy system security is a power system that is able to operate within defined technical limits, such as frequency, even if there is an incident such as the loss of a major transmission line or large generator.
Frequency is an outcome of supply and demand balance and is kept close to 50 Hz with the Frequency Control Ancillary Services (FCAS) market to provide this balance. The Australian Energy Market Operator operates the FCAS market, which has historically tended towards changes in generation (supply) rather than demand.
Rate of change of frequency (ROCOF)
Rate of change of frequency or ROCOF is the steepness of a change in frequency following a contingency event.
Inertia is the power system’s immediate response to a contingency event. The level of inertia dictates the rate of change of frequency away from 50 Hz immediately after the event. Inertia allows for time to bring the power systems other emergency frequency control mechanisms into assist and restore frequency.
Fast frequency response
Fast frequency response is the fast-acting frequency control capability that can be delivered from a battery storage system or wind turbine generator. Acting like a synthetic form of inertia it swiftly injects (or consumers) power into (or from) the grid to push against a high rate of change of frequency event, with an aim to assist in restoring the supply-demand balance and therefore the frequency.