MCQ Answers
1. B — Chemical → Thermal → Kinetic → Electrical. Coal burns to produce heat, steam spins a turbine (kinetic), generator produces electricity.
2. C — Pumped hydro stores energy for days to weeks. Batteries are faster but limited to hours.
3. B — Wind is intermittent; batteries smooth output and store excess for calm periods.
4. D — Snowy 2.0 (2,000 MW, 350,000 MWh) is the largest pumped hydro in the southern hemisphere.
5. A — Baseload = 24/7 constant (coal); peaking = rapid response to demand (gas, batteries); intermittent = weather-dependent (solar, wind).
SAQ 1 — Compare Renewable and Non-Renewable (3 marks)
Marking Criteria: 1 mark — definition distinction. 1 mark — one example of each with explanation. 1 mark — relevance to Australia's future (emissions, resource advantage, or transition).
Model answer: Renewable energy sources are naturally replenished on human timescales, such as solar, wind, and hydroelectric power. Non-renewable sources like coal, natural gas, and uranium exist in finite quantities and will eventually deplete. For example, solar energy uses photovoltaic cells to convert light to electricity with no fuel consumption, while coal requires burning fossilised plant matter that took millions of years to form. This distinction matters for Australia because renewables produce near-zero greenhouse gas emissions during operation, helping meet climate targets. Australia also has exceptional solar and wind resources — some of the best in the world — making renewables economically competitive. As coal plants age and retire, the shift to renewables is both an environmental necessity and an economic opportunity for Australia.
SAQ 2 — Journey of Electricity (4 marks)
Marking Criteria: 1 mark — generation (power station, fuel types). 1 mark — transmission (high voltage, towers, substations). 1 mark — distribution (local grid, transformers). 1 mark — voltage changes explained (P=IV, lower current = lower I²R losses for transmission; safety reasons for lowering to 240 V).
Model answer: Electricity begins at a generation stage where power stations convert chemical, nuclear, or kinetic energy into electrical energy at high voltages (11–25 kV). This is stepped up to 132–500 kV for transmission through tall steel towers spanning hundreds of kilometres. High voltage is used because power loss in wires follows Ploss = I²R — by transmitting at high voltage and low current, losses are minimised. At substation transformers near cities, voltage is stepped down to 11–33 kV for distribution through poles and underground cables. Final transformers reduce this to 240 V (single-phase) or 415 V (three-phase) for safe use in homes and businesses. Without these voltage changes, either enormous energy would be lost as heat in transmission wires, or homes would receive dangerously high voltages.
SAQ 3 — Evaluating "Batteries Alone" (5 marks)
Marking Criteria: 1 mark — evaluate statement (false/oversimplified). 1 mark — explain battery strengths and limits (hours, cost, materials). 1 mark — explain pumped hydro for multi-day storage. 1 mark — explain hydrogen for seasonal/export. 1 mark — propose coherent portfolio citing Australian examples.
Model answer: The statement "batteries alone will solve Australia's energy storage problem" is an oversimplification. While lithium-ion batteries excel at short-duration storage (1–4 hours) and respond in milliseconds to grid frequency changes — as demonstrated by the Hornsdale Power Reserve in South Australia — they are not suited for all storage needs.
Energy storage requirements span three timescales. For daily cycling (hours), batteries are ideal: they charge during midday solar surplus and discharge during evening peak demand. However, for multi-day to weekly storage during extended wind lulls or cloudy weather, pumped hydro is superior. Snowy 2.0 will store 350,000 MWh — enough to power 3 million homes for a week — far exceeding any battery farm.
For seasonal storage and export, green hydrogen is the leading candidate. Excess renewable energy can electrolyse water into hydrogen, which can be stored indefinitely, shipped to Japan and Korea, or burned in turbines during winter when solar output is lowest.
My proposed multi-technology portfolio for Australia: batteries for grid stability and daily shifting (Hornsdale-style); pumped hydro for week-long backup (Snowy 2.0); green hydrogen for seasonal balancing and export revenue (Pilbara hubs). No single technology can meet all storage needs — a diversified portfolio is essential for a reliable, net-zero grid.