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In Australia, the rapid growth of renewable energy has transformed the electricity sector, with energy sources like wind and solar now making up 39% of the electricity in the National Electricity Market up from 37.4% in the same period last year.
This shift away from fossil fuels has, however, resulted in new challenges – such as managing variable power generation and storage.
Unlike conventional power sources, such as coal, natural gas, and nuclear energy, renewable sources such as solar and wind are inherently variable due to weather conditions. Therefore, integrating renewable energy into the grid is a complex and challenging task that requires careful planning and investment.
Storage technologies such as lithium-ion and flow batteries are capable of stabilising the grid and improving solar power’s reliability by storing excess electricity generated during times of peak production. This stored energy can then be dispatched during periods of low generation, ensuring a steady and consistent power supply.
Storage systems are also able to respond to grid imbalances within microseconds, much faster than traditional spinning reserve generators, making their response capability indispensable during Australia’s current energy transition, especially in light of the increasing penetration of solar and wind energy.
TBH Renewable Energy Specialist and Director, Ali Nami, discusses how storage technologies can help address wind and solar power variability and help to guarantee a reliable and secure supply for the energy sector.
Variability and Grid Constraints
Extreme weather events such as floods, storms, fires, and heatwaves have become more frequent and severe globally. This has serious implications for the energy system’s reliability and performance.
Wind turbines can shut down during severe wind events to prevent damage, reducing power output, while increased cloud cover and smoke reduce solar energy production. It is especially dangerous for grid stability when both events occur simultaneously at multiple facilities in the same region.
In 2021, the United States experienced terrible blackouts throughout the state of Texas when a severe winter storm caused a significant portion of its power generation capacity to go offline at once. This outage affected more than ten million people and resulted in at least 246 deaths.
California’s power grid has also faced significant challenges in the last few years – and in 2021 during a heatwave, rolling blackouts affected over 800,000 homes and businesses.
Likewise, the United Kingdom experienced a regional blackout on August 9, 2019, affecting 1.1 million consumers due to a sudden shutdown of the Hornsea 1 offshore wind facility combined with the “tripping” of a gas-fired combined-cycle plant after a severe electric storm.
Energy Storage Provides a Buffer
Energy storage provides a buffer between the energy supply and the demand, allowing it to be dispatched when needed. This helps to protect homes and businesses from outages caused by unpredictable changes in demand or supply, such as extreme weather events.
By storing excess energy generated during periods of high wind or sunlight and releasing it during periods of low wind or sunlight, storage technologies can prevent blackouts and ensure a reliable electricity supply – even when renewable energy generation is variable.
Storage technologies also enhance grid reliability and help stabilise the grid through services such as frequency regulation, voltage support, and spinning reserves.
Since power grids are made up of generators that produce power and loads that consume it and are spread out all over the grid, in an ideal system, generators would always supply the exact amount of energy required. But because service providers have no way of knowing in advance exactly how much power will be required; this can be challenging.
Traditional grid infrastructure relies on spinning reserve and backup reserve generators that respond to second-to-second variation in demand using the inertia of the generator rotor. Before renewable energy sources were added to the mix, the grid was typically overloaded just a little bit — and that small amount of power was released to keep voltages and frequencies safe.
Now with the addition of solar farms and wind turbines to the grid, things are a bit less stable and predictable – due to the fact that these energy sources often produce surpluses or deficits, storage systems offer a potential solution to this issue because they can act as a buffer by storing excess energy during productive periods and discharging it during times of high demand.
So, essentially, when renewable energy sources make more power than the grid needs (sunny or windy days), storage systems like batteries can absorb the extra power and store it. Then when demand exceeds generation (i.e. during a heat wave when everyone needs air conditioning) the system can discharge that power and help power and balance out the grid.
How Do Different Energy Storage Systems Compare
In view of the constantly changing nature of the energy sector, different types of energy storage are becoming key components in modern energy systems worldwide, contributing to the management of energy demand both daily and seasonally.
These storage systems come in various forms, each designed to capture, store, and release energy efficiently, including:
Pumped Hydro Energy Storage (PHES)
As an established form of grid storage, Pumped Hydro Energy Storage (PHES) pumps water to a higher elevation during low demand periods, and then released during peak demand periods through turbines to generate electricity.
When it comes to high capacity, long duration applications, this storage method is more economical than batteries (at least for now) and is able to generate electricity for longer periods without materially losing power – making it well suited to tackle daily, weekly, and even seasonal intermittencies.
PHES facilities can have either open-loop design, where water passes through once, or closed-loop systems that recycle the water used and do not interfere with rivers, dams, or waterways.
- Open-loop PHES design requires specific geographical conditions, such as two bodies of water at different elevations which can restrict where these plants can be built as well as substantial alterations to the natural landscape or the use of existing water bodies.
- Closed loop pumped hydro systems instead have been designed to minimise environmental impacts by not being connected to natural water bodies like rivers or streams, making them more environmentally friendly and easier to site.
While the cost of maintaining a PSH facility is relatively low, the startup costs of pumped storage projects are often prohibitively high. Furthermore, finding suitable land that is large enough and has the right topography to host a reservoir, a facility, as well as all the other needs can be challenging.
The Global Atlas of Closed-Loop Pumped Hydro Energy Storage developed by researchers at the Australian National University, has identified an enormous potential for environmentally friendly pumped hydro energy storage (PHES) worldwide.
The researchers identified 616,000 potential locations around the world that could be used as environmentally friendly closed loop PHES sites. If these sites around the planet were all used, they would generate around 23 million GWh, which is significantly more energy than that required to support a 100% global renewable electricity system.
Compressed Air-Energy Storage (CAES)
Compressed Air Energy Storage (CAES) is a new technology that uses electricity to compress air and store it in underground caverns or other suitable geological formations, which can then be expanded through a turbine to generate electricity when demand peaks or renewable generation dips. It can be used to integrate renewable energy sources into the grid for seasonal load shifting, load balancing, peaking reserve, and traditional peak to off-peak load shifting.
One of the most interesting advancements in CAES technology is the exploration of storing compressed air in porous rock structures (instead of underground salt caverns). This expansion of potential storage sites increases the feasibility and applicability of CAES across different geographical locations.
A disadvantage of CAES is its low energy efficiency since compressing air produces heat that is often dispersed into the surrounding environment because to improve output, additional energy (often from burning natural gas) is required to heat up the compressed air again after it is expanded to generate electricity.
The round-trip efficiency of CAES systems is therefore generally between 60 and 65 percent, which is lower compared to other energy storage technologies like lithium-ion batteries that can achieve efficiencies in the high 80 percent range.
Lithium-ion Batteries
Lithium-ion batteries are ideal for short-to medium-duration storage applications and offer high round-trip efficiency and fast response times. The cost of lithium-ion technology, while on a downward trajectory, can be a hefty initial investment, particularly when compared to alternatives like lead-acid batteries. But this is expected to keep dropping.
Negatives include a risk of thermal runaway—a condition where batteries overheat and potentially catch fire, and supply chain vulnerabilities due to the finite nature of critical materials such as lithium, cobalt, and nickel, essential for production.
Between 2010 and 2019 lithium-ion battery unit costs decreased by 85%, as reported by the International Renewable Energy Agency, and in 2024, the storage sector is expected to be significantly influenced by battery overproduction and overcapacity – a situation that will likely put pressure on prices, leading to a forecasted price drop in both lithium-ion battery pack and other energy storage systems.
Flow Batteries
Flow batteries have unique advantages for long-duration energy storage applications.
Their ability to independently scale energy and power capacity makes them particularly suited for storing large amounts of energy over extended periods.
Flow batteries possess a lower energy density than lithium-ion batteries, which means they need more space for the same energy storage capacity, which can be a problem in areas where space is at a premium.
The costs associated with flow batteries, especially those using vanadium, are also still very high compared to other storage types like iron, salt, and water-based flow batteries, however according to the International Renewable Energy Agency (IRENA), the installation cost for VRFBs is expected to drop to between $108 and $576 per kWh by 2030.
This is great news for renewable adopters, because as battery storage costs decrease, the ability to store energy generated from renewable sources like solar and wind becomes more economically viable in different forms and scales – which in turn can lead to greater and faster adoption of these technologies.
Underground Gravity Energy Storage (UGES)
Underground Gravity Energy Storage repurposes decommissioned mine sites as a long-term energy storage solution. Unlike batteries, this storage system does not lose energy when it self-discharges, meaning it can allow for storage ranging from weeks to years.
Discovered by a group of international scientists, UGES reuses played-out mines to utilise earth’s natural gravity to raise and lower sand, rocks or concrete blocks to store and release energy.
The system generates electricity by lowering sand into underground mines and converting the potential energy into electricity through regenerative braking. When electricity is cheap, the sand gets lifted back up to store energy.
Because mine shafts, are typically multi-levelled, they already possess the infrastructure needed for this type of system – another benefit to using mine sites is that they have existing connections to the power grid, which reduces the cost and complexity of installation compared to building new facilities.
Environmentally, UGES uses already disturbed areas (mines), so this system can directly benefit ecosystems by reducing the need for land use elsewhere for energy storage facilities.
Unfortunately, despite its potential, UGES is still largely in the demonstration phase, however, the technology holds promise for providing a sustainable and cost-effective solution for long-term energy storage, especially in regions with a high density of abandoned mines (like Australia).
Green Hydrogen
Since hydrogen can be stored in different forms and used for electricity generation, industrial processes and as a transport fuel – it is a versatile, scalable and sustainable solution for storing renewable energy.
While currently more expensive than other strategies, green hydrogen will likely soon become one of the most cost-competitive options for long-duration storage. For example, with elevated natural gas prices due to recent geopolitical factors, this solution is now competitive with grey and black hydrogen (made using natural gases or fossil fuels) and projections suggest that by 2030, it will drop to $1.50 per kilogram.
Australia has invested more than $500 million to develop green hydrogen hubs in regional areas of the country, and build infrastructure to store the hydrogen, including pipelines and refuelling stations. These hubs will be used to co-host producers, users and potential exporters in the industrial, transport, export and energy sector and generally expand the industry.
Outside of Australia, for countries with large populations and growing economies such as China and India, policy support and investment drivers will help contribute to the ongoing reduction in green hydrogen production costs, making it an increasingly attractive option for decarbonising various sectors of these large economies. India and Japan are investing heavily in green hydrogen – with India’s Green Hydrogen Mission aiming to reduce the cost of green hydrogen by up to 40% through incentives and cheap renewable electricity.
The European Union’s hydrogen strategy forecasts that “…from 2030 onward and towards 2050, renewable hydrogen technologies should reach maturity and be deployed at large scale to reach all hard to decarbonise sectors.”
Advanced Flywheels Supply Rapid Backup Power
Flywheels (FESS) are mechanical devices that provide rotational energy storage. When charged, a motor spins up the flywheel using electricity from the grid, and during discharge, the flywheel’s inertia drives a generator to produce electricity.
Due to the use of advanced composite and magnetic bearing technologies, flywheels can withstand hundreds of thousands of duty cycles while providing grid balancing services like frequency regulation, voltage sag compensation, and renewables smoothing.
The Robertstown substation in South Australia uses flywheels to provide grid stabilisation and to help restore lost inertia in the grid. The ultrafast ramping of flywheels handles power fluctuations better than other types of storage so they can better bridge supply and demand mismatches during peak generation or demand.
There are some disadvantages to flywheel systems, including higher upfront costs and the fact they are not suitable for use in space-constrained environments since they need to be installed in a specific orientation to minimise friction and gyroscopic losses.
Rock Thermal Energy
Using the natural heat-storing properties of granite and soapstone, rock thermal energy storage (RTES) is emerging as a promising technology for stabilising renewable energy sources.
Several countries are demonstrating the viability of RTES, including large scale projects in Denmark and Italy that are using stone to store energy. Tanzanian soapstone in particular offers remarkable heat retention properties and remains stable at high temperatures – which makes these rocks particularly suitable for storing thermal energy.
While rock-based thermal energy storage (RTES) is a promising solution for storing renewable energy, there are limitations worth considering, such as the efficiency of heat extraction and the variability of rock properties depending on geographical location.
Planning and Operations Considerations
Determining the appropriate size and capability of an energy storage system in the Australian context requires careful planning and a thorough understanding of the different technologies available, their efficiencies, capacities, discharge durations, as well as the specific needs of the grid and the regulatory environment.
Factors that should be considered include:
- Load Demand: Understanding the grid’s load demand is crucial for sizing the battery system to supply the peak demand.
- Storage Needs: Different applications require different storage durations. For example, short-duration storage (2-4 hours) is suitable for frequency regulation, while long-duration storage (10+ hours) is needed for seasonal storage.
- Regulatory Environment: Compliance with local regulations and standards may include safety standards, interconnection requirements, and policies that support or restrict energy storage deployment.
Planning Charging and Discharging Around Renewable Generation
Given the variability of renewables, storage systems need to be flexible, ready to absorb excess energy during peak production times and release it during periods of low generation or high demand.
Scheduling the charging and discharging of systems to align with renewable generation profiles also requires strategic planning to charge during the high energy production times and discharge during the low energy production times.
Predictive analytics can help with this by forecasting generation and demand patterns with historic weather data to anticipate periods of surplus renewable energy for charging and times of deficit for discharging and by coordinating the charging and discharging of multiple storage assets across the grid, operators can more precisely balance supply and demand.
Project Controls and Modelling
Project controls and modelling tools can be used to help guarantee reliable performance by implementing effective control mechanisms, collecting, and analysing data, and taking appropriate corrective actions.
Advanced modelling techniques can simulate various scenarios, making it possible to predict how different storage systems will perform under certain conditions to help operators prepare for challenges and make decisions about when to store and release energy and when to monitor storage operations to ensure systems are operating within designed parameters.
Summing Up
Clean Power America described energy storage systems as being “… as revolutionary to the energy industry as refrigeration was for the food industry.”
It is, however, important to consider many factors, including the specific application, desired capacity, power requirements, efficiency, cost, lifetime, and environmental considerations, before choosing a suitable storage technology.
By 2050, renewable energy sources like wind and solar should meet almost all of Australia’s electricity needs, with energy storage systems–like pumped hydro and batteries–making clean energy available around the clock.
TBH has been in the energy market for more than a decade and has broad experience working on complex energy projects worldwide. Whether integrating storage technologies into existing projects or creating a stand-alone energy storage facility, we believe as these systems become increasingly incorporated within the design briefs of renewable energy projects, they will no doubt define the renewable energy landscape for the years to come.
Contact Ali Nami for information about TBHs services throughout the development lifecycle of renewable energy projects, from business case development through to site investigation, planning approvals and project management.