📖 Lesson 15 ⏱ ~30 min Year 9 · Unit 3 ⚡ +100 XP

Energy Storage and the Transition

In 2022, Australia's Hornsdale battery in SA discharged 150 MW in under 4 seconds to stabilise the grid when a coal unit tripped offline.

Today's hook: In September 2022, overcast skies blanketed South Australia for nearly 24 hours and wind speeds dropped too low to spin turbines, yet the lights stayed on. The Hornsdale Power Reserve, a 150 MW Tesla battery near Jamestown, discharged stored electricity within milliseconds of the demand spike. Without energy storage, even the sunniest and windiest nation cannot run on renewables alone. What storage technologies exist, and which scales up best for Australia?

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Warm-up

Think First

+5 XP each

Q1 · Solar panels only produce electricity when the sun shines, and wind turbines only work when it's windy. Before reading, what do you think are the options for keeping the lights on when neither is available?

Q2 · If you were designing an energy storage system for a whole city, what properties would it need, think about capacity, speed of response, safety, cost, and lifespan?

Learning objectives

What you'll master

3 areas

● Know

The main energy storage technologies: batteries, pumped hydro, hydrogen
That storage solves the intermittency problem of renewables
Australia's 82% renewable target by 2030

● Understand

How each storage technology stores and releases energy
Why different storage suits different time scales (seconds to seasons)
The economic and engineering challenges of large-scale storage

● Can do

Compare storage technologies using capacity, cost, and response time
Explain why storage is essential for renewable energy
Evaluate storage options for different Australian locations

Cross-lesson links: Energy storage brings together the energy transformations from Lessons 1–5 (chemical, electrical, gravitational potential energy swapping roles) and the grid management challenges from Lesson 14. In Lesson 21 you'll revisit hydrogen as a storage medium when exploring green hydrogen and Australia's export future.

Core learning

From the lesson

Storage

🔋 Energy Storage Technologies Compared

🔋 Battery Storage

Chemical energy on demand

+5 XP

Watch the sun set over a suburb full of rooftop solar panels, at 6 pm the panels switch off and every household flicks on lights, heaters, and cooktops simultaneously. Without a way to save the day's surplus solar energy, grid operators must instantly fire up gas or coal to fill the gap. Storage is the missing piece of the renewable energy puzzle: it captures surplus energy during generation peaks and releases it when demand peaks.

There are many storage technologies. Lithium-ion batteries respond in milliseconds and are ideal for grid stabilisation and short-term storage. Pumped hydro stores energy by pumping water uphill, then releasing it through turbines, it can provide hours or days of continuous power. Other technologies include compressed air, flywheels, and emerging green hydrogen.

Example

The Snowy Hydro 2.0 scheme will add 2,000 megawatts of generation capacity and 350,000 megawatt-hours of storage. That is enough to power three million homes for a week, making it one of the largest storage projects in the world.

Real-world anchor

AEMO estimates that Australia will need significant storage capacity, both batteries and pumped hydro, to maintain grid reliability as coal plants retire. Storage is no longer optional; it is essential infrastructure.

What to write in your book

Storage captures surplus energy and releases it when needed
Batteries respond in milliseconds; pumped hydro provides hours of storage
Different storage technologies suit different timescales

Predict then reveal+8 XP

1 · Predict

2 · Reveal

3 · Compare

How long can Australia's largest battery at Hornsdale power the entire state of South Australia?

Confidence 50%

💧 Pumped Hydro

The original giant battery

+5 XP

Each storage technology has a sweet spot. Batteries excel at rapid, frequent cycling, charging and discharging many times per day. Pumped hydro excels at bulk, long-duration storage. Hydrogen could become the solution for seasonal storage: storing summer solar energy for winter use, or exporting it overseas as a fuel.

No single technology will solve all storage needs. The future grid will use a portfolio approach: batteries for seconds-to-hours, pumped hydro for hours-to-days, and hydrogen for weeks-to-months. Choosing the right tool for each job is the essence of good systems engineering.

Example

A hospital might use batteries for instant backup during a blackout, while the national grid uses pumped hydro to cover a windless week. Both are storage, but they serve completely different timescales and reliability requirements.

What to write in your book

Batteries excel at rapid, frequent cycling
Pumped hydro excels at bulk, long-duration storage
Hydrogen may become the solution for seasonal storage

Match each storage technology to its key characteristic.

Lithium-ion battery
Pumped hydro
Compressed air
Flywheel
Green hydrogen

Stores energy as chemical bonds, long-term storage
Uses underground caverns to store energy
Stores kinetic energy, very fast response
Large capacity, hours to days
Fast response, seconds to hours

🌿 Hydrogen

The fuel that could power the world

+5 XP

Grid operators must balance supply and demand every second. If generation exceeds demand, the excess can be stored. If demand exceeds generation, stored energy is released. Batteries perform this balancing act far faster than any conventional power station, smoothing out the variability of wind and solar.

Storage also provides valuable grid services: frequency regulation (keeping the AC waveform steady), voltage support, and black-start capability (restarting the grid after a major outage). These services were traditionally provided by spinning coal turbines; batteries are now replacing them.

Example

When a large coal generator trips offline, the grid frequency drops suddenly. The Hornsdale battery can inject power within milliseconds, faster than any gas turbine can start, preventing blackouts and maintaining stable supply.

What to write in your book

Grid operators balance supply and demand every second
Batteries provide frequency regulation and fast response
Storage replaces some services previously provided by coal turbines

What is the main role of grid-scale battery storage?

From the lesson

Interactive

Interactive, Choose Your Storage

🎮 Match Storage to Scenario

Click the best storage technology for each scenario. Consider duration, cost, and feasibility.

Scenario 1: A wind farm in SA needs to smooth output for 15-minute gusts

Wind speeds vary constantly. The grid needs instant response to prevent frequency fluctuations.

Scenario 2: Tasmania wants to store summer hydro surplus for winter dry months

Rainfall is seasonal. Excess water in summer could generate electricity in winter when dams are low.

Scenario 3: Japan wants to import clean fuel from Australia for its steel mills

The fuel must be transported 7,000 km by ship and stored for weeks at the destination.

From the lesson

Copy Into Your Books

▼

Lithium-ion Batteries

Electrical → Chemical → Electrical
Duration: 1-4 hours | Efficiency: 85-95%
Cost: ~$400/kWh | Best: frequency control
Hornsdale (SA): 150 MW / 194 MWh

Pumped Hydro

Electrical → GPE → Kinetic → Electrical
Duration: 6-100 hours | Efficiency: 70-85%
Cost: ~$200/kWh | Best: overnight storage
Snowy 2.0: 2,000 MW / 350,000 MWh

Green Hydrogen

Electrical → Chemical (electrolysis) → Electrical
Duration: days to months | Efficiency: 30-45%
Cost: ~$500/kWh | Best: transport fuel, seasonal
Pilbara hubs planned for export to Asia

Why Storage Matters

Solar only generates during daylight
Wind is variable and unpredictable
Storage shifts energy from surplus to shortage
Australia target: 82% renewable by 2030

From the lesson

Activity 1

Identify + Apply

Energy Transformation Chains for Storage

For each storage technology, write the complete energy transformation chain for both charging and discharging. Name the energy form at each stage and the object/substance that has it.

1 A lithium-ion battery in the Hornsdale Power Reserve, South Australia.

✏️ Answer in your book.

2 The Snowy 2.0 pumped hydro scheme during a charging cycle.

✏️ Answer in your book.

3 Green hydrogen production at a Pilbara solar farm, then use in a Tokyo fuel cell.

✏️ Answer in your book.

From the lesson

Activity 2

Evaluate + Recommend

Design Storage for a Renewable Island

King Island, Tasmania (population 1,600) currently relies on diesel generators for 60% of its electricity. The island has excellent wind resources and moderate solar potential, but no rivers suitable for hydro. Using what you have learned about storage technologies, design a renewable + storage system for King Island. For each component, explain why it suits this location, describe the energy transformations, and address the challenge of multi-day calm periods with no wind.

✏️ Design and justify in your book.

From the lesson

Additional content

Reflect

Revisit your thinking

reflect

At the start of this lesson you were told that South Australia's sun stopped shining and wind dropped to zero for 24 hours, yet the lights stayed on, powered entirely by giant batteries and pumped hydro. Australia is building some of the world's largest energy storage systems.

Now that you've explored the storage options, which technology do you think is most promising for Australia's future, and why? Has the lesson changed your view?

Interactive Tool, Sustainability Audit Open fullscreen ↗

Batteries store energy as:

Quick check · multiple choice

Quick check

What is the primary energy transformation that occurs when a lithium-ion battery is charging?

+10 XP

Quick check

Why is pumped hydro particularly valuable for renewable energy systems?

+10 XP

Quick check

Green hydrogen is produced by splitting water using renewable electricity. What is the main advantage of green hydrogen over fossil fuels?

+10 XP

Quick check

A grid operator needs to store excess midday solar energy for use at 7:00 PM. Which storage technology is most appropriate?

+10 XP

Quick check

Snowy 2.0 will store 350,000 MWh of energy. Approximately how many Tesla Powerwalls (each 13.5 kWh) would be needed to store the same amount?

+10 XP

From the lesson

Short Answers

Written Response

Short Answer Questions

Use clear scientific language. Check the model answers after attempting each question.

3 marks

Question 1. A pumped hydro facility pumps 500,000 tonnes of water 200 metres uphill using surplus solar energy. Calculate the gravitational potential energy stored. Use g = 9.8 m/s². Show all working.

✏️ Answer in your book.

Hint: Use Eₚ = mgh. Convert 500,000 tonnes to kilograms first (1 tonne = 1,000 kg). Then multiply by g and height.

4 marks

Question 2. A student claims: "Lithium-ion batteries are the best storage technology because they are the most efficient and fastest to respond. We should only build batteries and forget about pumped hydro and hydrogen." Evaluate this claim, providing at least one argument supporting the claim and at least two arguments challenging it. Use specific evidence from this lesson.

✏️ Answer in your book.

Hint: Consider the duration limitation of batteries. Can a battery store energy for a week? What about cost at very large scale? What about the 50-100 year lifespan of pumped hydro vs 10-15 years for batteries?

5 marks

Question 3. Australia aims to reach 82% renewable electricity by 2030. Using what you have learned about renewable generation, storage technologies, and grid stability, explain why storage is essential for this target, and evaluate which combination of storage technologies would be most effective for Australia. Your answer should consider: daily solar cycles, multi-day wind lulls, seasonal variations, geography, and cost.

✏️ Answer in your book.

Hint: Think about what each technology does best. Batteries for daily cycles, pumped hydro for multi-day, hydrogen for seasonal/export. Where does Australia have geography for pumped hydro? Where does it have sun for hydrogen production?

Model answers (click to reveal)

Model Answers

▼

Q1 (3 marks)

Formula: Eₚ = mgh (1 mark)

Working: m = 500,000 tonnes = 500,000,000 kg. g = 9.8 m/s². h = 200 m. Eₚ = 500,000,000 × 9.8 × 200 = 980,000,000,000 J = 9.8 × 10¹¹ J. (1 mark)

Conversion: 980,000,000,000 J = 980,000 MJ = 980 GJ. (1 mark)

Marking criteria: (1) States correct formula. (2) Correctly substitutes values with unit conversion. (3) Correct final answer with appropriate units.

Q2 (4 marks)

Supporting argument: Lithium-ion batteries are 85–95% efficient and respond in milliseconds, faster than any other storage technology. They are modular, scalable, and can be installed almost anywhere. For grid frequency stability and short-duration peak shaving, batteries are unmatched. (1 mark)

Challenge 1: Batteries are limited to 1–4 hours of duration at full power. They cannot store energy across multiple calm, cloudy days. Pumped hydro can store energy for days or weeks, making it essential for seasonal and multi-day storage. Snowy 2.0 stores 350,000 MWh, equivalent to 26 million Powerwalls. (1 mark)

Challenge 2: Lithium-ion batteries have a lifespan of 10–15 years and require replacement. Pumped hydro lasts 50–100 years with minimal maintenance. Battery costs, while falling, remain high for very large scales ($400/kWh vs $200/kWh for pumped hydro). Additionally, lithium mining has significant environmental impacts. A diversified storage portfolio reduces risk and cost. (1 mark)

Conclusion: Batteries excel at short-duration, fast-response applications but are not a complete solution. Australia needs a mix: batteries for daily cycling and frequency control, pumped hydro for multi-day storage, and hydrogen for seasonal storage and export. (1 mark)

Marking criteria: (1) Valid supporting argument with efficiency/response data. (2) Challenge 1 (duration limitation, pumped hydro advantage). (3) Challenge 2 (lifespan, cost, or environmental impact). (4) Balanced conclusion recognising need for mixed portfolio.

Q3 (5 marks)

Why storage is essential: Solar generates only during daylight (~8 hours/day) and wind is variable. At 82% renewable, the grid would have massive midday surpluses and evening/overnight shortfalls. Without storage, excess renewable energy would be wasted (curtailed) and fossil fuels would still be needed for reliability. Storage shifts energy from surplus periods to shortage periods. (1 mark)

Daily cycle solution: Lithium-ion batteries are ideal for daily solar cycling. They charge from midday solar surplus and discharge during evening peak (5–9 PM). Australia's 40+ grid-scale battery projects provide this service. (1 mark)

Multi-day solution: Pumped hydro is essential for multi-day storage. During extended wind lulls or cloudy periods, batteries deplete quickly. Snowy 2.0, Kidston, and other pumped hydro projects can provide 6–100 hours of continuous output. Australia's mountainous east coast has excellent pumped hydro potential. (1 mark)

Seasonal/export consideration: Green hydrogen addresses seasonal storage and export. The Pilbara's intense sunshine can produce hydrogen during dry winter months when hydro reserves are low. Hydrogen can be exported to Japan and South Korea, creating a new Australian export industry to replace coal and LNG. (1 mark)

Recommended combination: Batteries for daily cycling + frequency control, pumped hydro for multi-day backup, and hydrogen for seasonal/export. This portfolio covers all time scales from milliseconds to months. Geographic diversity, batteries distributed across the grid, pumped hydro in the mountains, hydrogen in the Pilbara, also improves resilience. (1 mark)

Marking criteria: (1) Explains why storage is essential for 82% target. (2) Identifies daily solution (batteries). (3) Identifies multi-day solution (pumped hydro). (4) Identifies seasonal/export solution (hydrogen). (5) Recommends integrated portfolio with justification.

From the lesson

Additional content

Quick-fire challenge

Game time

+25 XP

From the lesson

📚 Revisit the Content

Want to review any section before moving on?

Storage Comparison Batteries Pumped Hydro Hydrogen Choose Your Storage

Mark lesson as complete

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