Question 1
Define a renewable energy source.
[1]
Distinguish between the classification of sustainably managed wood and nuclear fuel as energy sources.
[2]
Question 2
Distinguish between energy conservation and energy efficiency, using one example of each.
[3]
State how both approaches may reduce a country's dependence on imported energy.
[1]
Question 3
Figure 1 shows changes in global primary energy consumption by source between 2000 and 2022.
Calculate the percentage increase in total global primary energy consumption between 2000 and 2022.
[2]
Describe two changes in global energy consumption shown in Figure 1.
[2]
Explain how renewable-energy consumption and fossil-fuel consumption could both increase over the period shown.
[2]
Question 4
A residential building introduced four measures to reduce energy consumption. Figure 3(a) summarizes the measures, and Figure 3(b) shows annual energy use before and after their introduction.
Using Figure 3(a), identify one energy-efficiency measure and one energy-conservation measure.
[2]
Calculate the percentage reduction in the building's total annual energy use.
[2]
Explain how the reduction shown could improve national energy security in a country that imports fuel for electricity generation.
[2]
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Question 5
A country's population and annual energy use per person are shown for two years.
Population and annual energy use per person in two years.
| Year | Population / million | Energy use / GJ per person per year |
|---|---|---|
| 2020 | 40 | 80 |
| 2030 | 44 | 88 |
Calculate the percentage increase in the country's total annual energy consumption from 2020 to 2030. Show your working.
[2]
Identify the two changes responsible for the increase in total energy consumption.
[1]
Question 6
Rare earth elements are used in the generators and motors of some renewable-energy technologies.
State why rare earth elements are not classified as energy sources.
[1]
Outline two environmental costs associated with the life cycle of rare earth elements.
[2]
Question 7
The fact file shows selected characteristics of the electricity system of the fictional country of Navira.
Outline two factors that favour increasing solar electricity generation in Navira.
[2]
Outline two limitations of relying heavily on solar electricity in Navira.
[2]
Question 8
The diagram shows a pumped hydroelectricity storage system connected to an electricity grid.
Explain how the system helps match an intermittent electricity supply to demand.
[3]
State why pumped hydroelectricity storage is not itself a primary energy source.
[1]
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Question 9
The electricity mix and import dependence of the fictional country of Lydora are shown.
State what is meant by energy security.
[1]
Explain two measures that could improve Lydora's energy security.
[3]
Question 10
Explain how nuclear fission in a power station produces electricity.
[4]
Question 11
Cooling water discharged from a nuclear power station raises the temperature of a nearby river.
Define thermal pollution.
[1]
Explain one way in which this discharge may affect aquatic organisms.
[2]
Question 12
The island of Cala Verde generates most of its electricity using imported diesel. Its government is considering a wind-turbine and battery-storage system.
Identify the time at which potential wind generation is approximately equal to electricity demand in Figure 1(a).
[1]
Calculate the surplus potential wind power at 03:00.
[2]
Explain how the proposed battery could reduce diesel use during the day shown.
[2]
Outline two reasons why the proposed system would not provide impact-free electricity.
[2]
Evaluate whether the wind-battery proposal is likely to make Cala Verde's electricity supply more sustainable.
[3]
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Question 13
A coastal freight company introduced wind-assist sails on two ships and intelligent low-energy lighting in its warehouses. Operational data were collected before and after the changes.
Annual energy use and financial data before and after the measures.
| Measure | Before measures | After measures | Unit |
|---|---|---|---|
| Ship diesel use | 48 | 39 | GWh per year |
| Warehouse lighting electricity use | 6.0 | 2.4 | GWh per year |
| Maintenance costs | 1.2 | 1.8 | million currency units per year |
| Imported-fuel expenditure | 34 | 28 | million currency units per year |
Calculate the percentage reduction in warehouse lighting electricity use.
[2]
Distinguish between the energy-efficiency and energy-conservation features of the intelligent lighting system.
[2]
Explain why the reduction in ship diesel use may vary between voyages.
[2]
Outline how the measures could improve national energy security if the country imports diesel fuel.
[1]
Evaluate the effectiveness of the company's energy measures.
[3]
Question 14
Table 1 compares selected life-cycle characteristics of five electricity sources.
Selected life-cycle characteristics of electricity sources.
| Electricity source | Life-cycle GHG emissions / | Land occupation / | Capacity factor / | Principal life-cycle concern |
|---|---|---|---|---|
| Coal | 820 | 15 | 70 | Mining waste and air pollution |
| Natural gas | 490 | 12 | 55 | Methane leakage and liquefaction energy |
| Nuclear | 12 | 5 | 90 | Uranium mining and radioactive waste |
| Onshore wind | 11 | 70 | 35 | Materials, wildlife and blade disposal |
| Solar photovoltaic | 45 | 35 | 20 | Mining, land use and panel recycling |
| Note | Capacity factor = actual output divided by maximum possible output over the same period. |
Calculate how many times greater the life-cycle greenhouse-gas emissions from coal are than those from onshore wind.
[1]
Compare nuclear power with onshore wind using the data in Table 1.
[2]
Suggest why the data do not support describing any one of the five sources as completely sustainable.
[3]
Question 15
Figures 2(a) and 2(b) show the operation of a pumped hydroelectricity storage system connected to a solar-rich electricity grid.
Electricity supply, demand and upper-reservoir energy over 24 hours
| Time | Solar generation / MW | Grid demand / MW | Upper-reservoir energy / MWh | Round-trip efficiency / % |
|---|---|---|---|---|
| 00:00 | 0 | 500 | 0 | 75 |
| 06:00 | 0 | 500 | 0 | 75 |
| 09:00 | 500 | 650 | 0 | 75 |
| 10:00 | 900 | 660 | 0 | 75 |
| 11:00 | 1000 | 760 | 240 | 75 |
| 12:00 | 1050 | 810 | 480 | 75 |
| 13:00 | 1000 | 760 | 720 | 75 |
| 14:00 | 900 | 660 | 960 | 75 |
| 15:00 | 800 | 560 | 1200 | 75 |
| 16:00 | 600 | 650 | 1200 | 75 |
| 17:00 | 300 | 800 | 1200 | 75 |
| 18:00 | 100 | 1100 | 1200 | 75 |
| 19:00 | 20 | 1200 | 800 | 75 |
| 20:00 | 0 | 1250 | 400 | 75 |
| 21:00 | 0 | 1150 | 0 | 75 |
| 22:00 | 0 | 750 | 0 | 75 |
| 24:00 | 0 | 500 | 0 | 75 |
Identify the period during which electricity is available for pumping water to the upper reservoir.
[1]
Calculate the electrical energy that can be returned to the grid after 1200 MWh is stored, assuming the stated round-trip efficiency.
[2]
Explain how the system shown contributes to peak shaving.
[3]
Question 16
Known economically recoverable oil reserves are estimated at 900 billion barrels. Current extraction is 30 billion barrels per year.
Calculate the reserves-to-production estimate for the number of years the reserves would last. Show your working.
[2]
Outline two reasons why the calculation in (a) does not give a reliable final depletion date.
[2]
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Question 17
A government introduces a policy that rapidly replaces coal-fired electricity with renewable electricity. Several coal mines and power stations are expected to close before the end of their planned working lives.
Define a stranded asset.
[1]
Explain how the policy could strand assets in the coal industry.
[2]
Question 18
A former lignite mine in the fictional Ostra Valley supplied fuel to a nearby power station. Mining ended in 2018, and restoration of the site began in 2019.
Selected indicators at Ostra Valley mine site in 2018 and 2025; suspended sediment is shown as mean ± reported error.
| Indicator | 2018 | 2025 |
|---|---|---|
| Vegetation cover / % | ||
| Mean suspended sediment downstream / mg L | ||
| Recorded plant species | 14 | 39 |
| Restoration expenditure / million currency units | 18 | 7 |
Calculate the percentage-point increase in vegetation cover between 2018 and 2025.
[1]
Describe two changes at the mine site shown in Figure 2(b).
[2]
Explain how revegetation of the spoil heaps could have caused the change in suspended sediment.
[2]
Suggest two reasons why restoration may not recreate the ecosystem that existed before mining.
[2]
Evaluate the success of environmental restoration at the Ostra Valley mine.
[4]
Question 19
Two fictional countries are selecting technologies for new electricity generation. Montara is mountainous and wet, while Soland is mostly flat and has a hot, dry climate.
Identify the proposed technology with the highest availability score in each country.
[2]
Explain why solar photovoltaic power may not meet Soland's peak electricity demand without another technology.
[2]
Outline one environmental or social disadvantage of constructing large hydropower reservoirs in Montara.
[1]
Compare the suitability of natural gas generation in Montara and Soland.
[2]
Justify an electricity strategy for each country using the evidence provided.
[3]
Question 20
Figure 4 compares the electricity mix and selected energy-security indicators for the country of Aruna in 2010 and 2024.
Electricity supply and energy-security indicators in Aruna
| Indicator or electricity source | 2010 | 2024 |
|---|---|---|
| Imported natural gas share | ||
| Imported oil share | ||
| Domestic hydropower share | ||
| Domestic wind and solar share | ||
| Domestic nuclear share | ||
| Annual interruption [hours per customer] | 18 | 6 |
| Mean household price [USD per kWh] | 0.14 | 0.20 |
| Electricity demand index (2010 = 100) | 100 | 130 |
Calculate the change in the proportion of electricity generated from imported fuels between 2010 and 2024.
[1]
Describe the evidence that Aruna's electricity supply became more reliable but less affordable.
[2]
Analyse how changes in Aruna's energy mix may have affected its energy security.
[3]
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Question 21
Table 2 gives estimated global fossil-fuel reserves and annual consumption. Figure 5 shows factors that can change estimated depletion timelines.
Illustrative global fossil-fuel reserves and annual consumption.
| Fuel | Economically recoverable reserve / Gt or trillion m^3 | Current annual consumption / Gt per year or trillion m^3 per year | Simple reserve-to-consumption ratio / years |
|---|---|---|---|
| Coal | 900 | 8.0 per year | |
| Oil | 240 | 4.8 per year | |
| Natural gas | 210 trillion | 4.2 trillion per year |
Calculate the simple reserve-to-consumption ratio for oil.
[1]
Identify the fuel with the largest simple reserve-to-consumption ratio.
[1]
Explain why the ratios calculated from Table 2 should not be interpreted as fixed dates of final depletion.
[4]
Question 22
Figures 6(a) and 6(b) show a nuclear power station and measurements taken in a river receiving its cooling-water discharge.
Calculate the increase in river-water temperature between the upstream site and the outlet.
[1]
Explain the relationship between water temperature and dissolved oxygen shown in Figure 6(b).
[2]
Analyse the claim that the power station provides sustainable electricity because it is low-carbon.
[3]
Question 23
Outline four reasons for the increase in global energy consumption.
[4]
Explain why fossil fuels may continue to supply a large proportion of global energy even while renewable-energy production increases.
[7]
Using named examples, to what extent can rising global energy demand be met in a way that is both equitable and environmentally sustainable?
[9]
Question 24
A researcher used secondary data for 24 countries to investigate the relationship between annual energy use per person and income per person. The variables were continuous, strongly skewed and showed a monotonic but non-linear relationship. A Spearman's rank correlation test gave and .
Outline why Spearman's rank correlation was an appropriate statistical test.
[1]
Interpret the result of the statistical test.
[2]
State why this result does not demonstrate that increasing income causes increasing energy use.
[1]
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Question 25
The fictional country of Elaria experienced a disruption to imported natural gas in 2022. It subsequently introduced energy-security policies, including offshore wind, additional interconnectors and industrial energy-efficiency standards.
Elaria's electricity generation mix in 2018, 2022 and projected for 2028.
| Electricity source | 2018 / % | 2022 / % | 2028 projected / % |
|---|---|---|---|
| Imported natural gas | 52 | 46 | 18 |
| Domestic coal | 18 | 22 | 12 |
| Wind | 12 | 15 | 30 |
| Solar | 6 | 8 | 16 |
| Hydropower | 7 | 6 | 7 |
| Nuclear | 5 | 3 | 5 |
| Imported electricity | 0 | 0 | 12 |
Elaria energy-security indicators; wholesale price is an affordability proxy; 2028 assumes normal wind conditions and three completed interconnectors.
| Indicator | 2018 | 2022 | Projected 2028 |
|---|---|---|---|
| Wholesale electricity price (affordability proxy) / currency units per MWh | 74 | 168 | 96 |
| Supply interruptions / h per customer | 1.6 | 5.4 | 1.2 |
| Industrial electricity demand index (2018 = 100) | 100 | 104 | 91 |
Calculate the projected change in the combined proportion of electricity generated from fossil fuels between 2022 and 2028.
[2]
Describe the evidence that Elaria's energy security deteriorated between 2018 and 2022.
[2]
Explain how the industrial energy-efficiency standards may improve Elaria's energy security.
[2]
Analyse how diversification could reduce, but not eliminate, risks to Elaria's electricity supply in 2028.
[3]
Evaluate whether the 2028 electricity strategy is likely to provide Elaria with affordable and reliable energy.
[3]
Question 26
Petroleum extraction in the fictional Marovan Basin began in 1995. Figure 6 shows how estimates of economically recoverable reserves and annual extraction changed as prices, technology and policy changed.
Figure 6(a): economically recoverable oil reserves and annual extraction in the Marovan Basin.
| Year | Economically recoverable reserves / billion barrels | Annual extraction / billion barrels per year |
|---|---|---|
| 1995 | 24 | 0.5 |
| 2005 | 31 | 0.8 |
| 2015 | 38 | 1.2 |
| 2025 | 29 | 1.0 |
| 2035 (projected) | 17 | 0.6 |
State what is meant by an economically recoverable fossil-fuel reserve.
[1]
Calculate the simple reserves-to-extraction ratio for 2025.
[2]
Explain why estimated reserves increased between 1995 and 2015 despite continuing extraction.
[2]
Suggest why some pipelines and platforms may become stranded assets before the basin's oil is physically exhausted.
[2]
Examine the claim that the Marovan Basin's oil will be depleted exactly 29 years after 2025.
[4]
Question 27
Figure 7 compares energy use, income and access to electricity in ten societies. The Spearman's rank correlation coefficient for energy use per person and income per person is given as .
Interpret the value of given for the two variables.
[1]
Compare Societies R and S using the data in Figure 7.
[2]
Evaluate the claim that increasing energy use per person will necessarily improve energy equity.
[3]
Question 28
Outline four stages that should be included in a life-cycle assessment of an electricity-generating technology.
[4]
Explain why replacing a natural-gas power station with a large solar photovoltaic installation would reduce some environmental impacts but create others.
[7]
Using named examples, evaluate the claim that renewable energy sources are always more sustainable than non-renewable energy sources.
[9]
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Question 29
Distinguish between intermittent energy production and peak shaving, and outline one way in which energy storage connects the two.
[4]
Explain how climate-responsive housing and intelligent low-energy lighting can reduce national energy consumption, including limitations to their effectiveness.
[7]
Using named examples, discuss whether energy storage or reduced energy demand is more important for increasing the contribution of intermittent renewable sources to a country's electricity supply.
[9]
Question 30
Outline four characteristics of an energy-secure country.
[4]
Explain how diversification, reduced import dependence and energy efficiency may interact to improve a country's energy security.
[7]
Using named examples, evaluate the extent to which policies that improve national energy security also improve environmental sustainability.
[9]
Question 31
The government of Norvale is considering replacing an aging coal power station with either a nuclear power station or a combination of offshore wind and battery storage.
Figure 7(a): Comparison of replacement options for Norvale's coal power station.
| Measure | Coal | Nuclear | Offshore wind + batteries |
|---|---|---|---|
| Life-cycle GHG emissions / | 820 | 18 | 32 |
| Capacity factor / % | 68 | 91 | 52 |
| Construction time / years | 4 | 12 | 6 |
| Expected operating life / years | 40 | 60 | 30 |
| Estimated total system cost / | 92 | 126 | 118 |
| Radioactive waste requiring long-term isolation / | None | 24 | None |
| Energy resource | Coal | Imported finite uranium | Domestic renewable wind flow |
| Output characteristic | Dispatchable | High, steady output | Weather-dependent; batteries reduce intermittency |
| Cooling-water discharge warming / | — | +2.8 | — |
| Other infrastructure or ecological consideration | — | — | Transmission and battery infrastructure; potential impact on migratory seabirds |
Calculate how many times greater the life-cycle greenhouse-gas emissions from coal are than those from nuclear power.
[2]
Explain why nuclear power is classified as non-renewable but low-carbon.
[2]
Explain one possible ecological impact of the nuclear station's cooling-water discharge.
[2]
Compare the contribution of nuclear power and offshore wind with batteries to Norvale's energy security.
[3]
Evaluate which option should replace Norvale's coal power station.
[3]
Question 32
Energy data were compiled for the fictional industrial country of Tanora and for the world. The tables show total primary energy use by source separately from access to electricity and other indicators.
Primary energy consumption by source for the world and Tanora.
| Area | Energy source | 2000 / EJ | 2010 / EJ | 2025 / EJ |
|---|---|---|---|---|
| World | Coal | 110.0 | 130.0 | 140.0 |
| World | Oil | 145.0 | 170.0 | 190.0 |
| World | Gas | 85.2 | 108.0 | 151.0 |
| World | Nuclear | 30.0 | 32.0 | 40.0 |
| World | Hydropower | 35.0 | 43.0 | 65.0 |
| World | Wind | 10.0 | 20.0 | 45.0 |
| World | Solar | 4.8 | 7.0 | 19.0 |
| Tanora | Coal | 2.0 | 3.1 | 3.3 |
| Tanora | Oil | 2.2 | 3.2 | 3.8 |
| Tanora | Gas | 1.4 | 2.4 | 3.1 |
| Tanora | Nuclear | 0.8 | 0.9 | 1.1 |
| Tanora | Hydropower | 0.7 | 1.0 | 1.4 |
| Tanora | Wind | 0.3 | 0.5 | 0.9 |
| Tanora | Solar | 0.6 | 0.4 | 1.4 |
Tanora energy, access, affordability and environmental indicators in 2000 and 2025.
| Indicator | 2000 | 2025 |
|---|---|---|
| Population / million | 44 | 60 |
| Primary energy use per person / GJ per year | 182 | 250 |
| Access to electricity / % | 79 | 98 |
| Energy burden, lowest-income fifth / % of income | 7 | 14 |
| Energy imports / % of primary energy | 38 | 57 |
| Urban fine particles / | 52 | 31 |
Calculate the increase in Tanora's total primary energy consumption between 2000 and 2025.
[2]
Compare the change in the fossil-fuel share of primary energy in Tanora with the global change between 2000 and 2025.
[2]
Explain why an increasing renewable share does not necessarily mean that fossil-fuel consumption is decreasing.
[2]
Analyse how Tanora's changing energy use has affected both energy equity and environmental quality.
[3]
Evaluate whether Tanora's energy transition between 2000 and 2025 can be considered secure, equitable and sustainable.
[3]
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Question 33
Distinguish between a fossil-fuel deposit, a fossil-fuel reserve and a stranded asset.
[4]
Explain how changes in consumption, technology, prices and government policy can alter estimated timelines for fossil-fuel depletion.
[7]
Using named examples, to what extent is the global economy likely to end its dependence on fossil fuels before economically recoverable reserves are depleted?
[9]
Question 34
Explain why nuclear power is classified as non-renewable and low-carbon rather than carbon-free.
[4]
Explain the environmental impacts that may occur at different stages of the nuclear-energy life cycle.
[7]
Using named examples, discuss whether nuclear power should form a major part of a country's transition to a reliable, low-carbon electricity system.
[9]
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