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IB DemystifiedMYP Sciences

Sustainable resources and energy choices

Every country must keep the lights on, the factories running and the water pumping, while cutting emissions and using finite materials wisely. Choosing between coal, gas, solar, wind, hydro and nuclear, and deciding how much to save and recycle, is one of the biggest scientific and social decisions of our time.

Recommended for MYP 5 · eAssessment priority · About 3 lessons · Criteria A, B, C and D

Coal820Natural gas490Biomass230Solar PV48Geothermal38Hydro24Nuclear12Wind110200400600800lifecycle emissions / g CO₂-equivalent per kWh
Figure 1. Lifecycle emissions differ enormously between electricity sources.
On this page
  1. Learning objectives
  2. Before you start
  3. Key vocabulary
  4. Understanding the ideas
  5. Comparing energy sources
  6. Energy choices in the real world
  7. Worked examples
  8. In the eAssessment
  9. Check your understanding
  10. Practice questions
  11. Investigation
  12. Criterion-linked questions
  13. Challenge questions
  14. Topic check
  15. Review your mistakes
  16. Your progress

Learning objectives

By the end of this topic you should be able to:

  • classify energy resources as renewable or non-renewable
  • compare sources using lifecycle emissions, reliability, cost and land use
  • apply efficiency, payback and energy-saving calculations
  • explain finite materials, recycling and the circular economy
  • analyse data from solar-panel and energy-saving investigations
  • discuss national and household energy decisions

Before you start

You will use these skills. If any feel shaky, review them first.

  • energy stores, transfers and efficiency (see Thermal energy transfer)
  • generating electricity and power
  • climate change and the greenhouse effect (see Climate change)

Key vocabulary

Renewable resource
A resource replenished naturally as fast as it is used.
Lifecycle emissions
Greenhouse gases released over the whole life of a power source, from building to decommissioning.
Intermittent
Producing power only some of the time, such as solar or wind.
Energy storage
Storing surplus energy for later use, for example in batteries or pumped hydro.
Payback time
The time for savings to equal the cost of an investment.
Circular economy
A system that keeps products and materials in use through reuse, repair and recycling.

Understanding the ideas

  1. What is it?

    Energy resources are either non-renewable, such as coal, oil, gas and uranium, which will run out, or renewable, such as solar, wind, hydro, geothermal and sustainably grown biomass. Each has different costs, emissions, reliability and effects on land, water and people.

  2. Why does it happen?

    Lifecycle assessment compares sources fairly by counting emissions from mining, manufacturing, building, running and dismantling. By this measure, wind, nuclear, hydro and solar have very low emissions, while coal and gas are far higher. But reliability matters too: solar and wind are intermittent, so grids need storage and flexible sources.

  3. How do we know?

    The IPCC gathers hundreds of studies to estimate lifecycle emissions. At school, you can measure solar-panel output, test insulation, and use energy meters to find what devices really use.

  4. Why does it matter?

    Choices about energy and materials affect bills, health, jobs, energy security and the climate. Many countries are adding solar and wind rapidly, improving efficiency and recycling metals needed for batteries and magnets.

  5. What does it connect to?

    This topic brings together energy and efficiency in physics, combustion and extraction of metals in chemistry, ecosystems in biology, and climate change in Earth science.

Comparing energy sources

  • Emissions: use lifecycle data (Figure 1).
  • Reliability: can it generate on demand, or is it intermittent?
  • Cost: building costs, fuel costs and payback time.
  • Resources: is the fuel finite, imported, or free?
  • Impacts: land use, water use, wildlife, waste, displacement of people.
  • Saving energy (efficiency, insulation, LEDs) is often the cheapest and cleanest option.

Energy choices in the real world

Pakistan has seen a rapid rise in rooftop solar as panel prices fall. Large dams on the Indus provide hydroelectricity and irrigation storage, and new ones are under construction. Recycling aluminium saves about 95% of the energy needed to make it from ore.

Worked examples

Example 1: payback time

A solar water heater costs Rs 90 000 and saves Rs 3000 a month on gas. Find the payback time.

  1. Months = 90 000 ÷ 3000 = 30 months.
  2. 30 ÷ 12 = 2.5 years.

Example 2: emissions saved

How much CO₂-equivalent is saved by using wind (11 g/kWh) instead of gas (490 g/kWh) for 500 kWh?

  1. Saving per kWh = 490 − 11 = 479 g.
  2. 479 × 500 = 239 500 g ≈ 240 kg.

In the eAssessment

Sustainability questions ask you to use data to compare options and make justified decisions. Expect:

  • Calculate efficiency, emissions saved and payback times.
  • Compare energy sources using several criteria, not just one.
  • Analyse experimental data from solar or energy-saving investigations.
  • Discuss decisions balancing environmental, economic and social factors.

Common ways to lose marks: saying renewables have no environmental impact; comparing sources on one criterion only; forgetting to convert grams to kilograms or months to years; and ignoring who pays for and who benefits from energy decisions.

Check your understanding

Quick questions on the ideas above. Try each one before using a hint.

Practice questions

Show

Investigation: designing a model wind turbine

Partially guided investigation · about 50 minutes · groups

Research question
How does the number of blades (2, 3, 4 or 6) on a model wind turbine affect its voltage output at a fixed wind speed from a fan?
Scientific background
Wind turbines convert the kinetic energy of moving air into electrical energy using a generator. Blade number affects how much of the wind's energy is captured and how fast the rotor spins.
Hypothesis
Write your own prediction, with a scientific justification.
Variables
Identify your independent, dependent and control variables, and explain how you will control them.
Apparatus
Small d.c. motor used as a generator, hub with slots for card or plastic blades, desk fan, voltmeter (or multimeter), ruler, card, scissors.
Method
  1. Make identical blades and fit 2 to the hub.
  2. Place the turbine 1 m from the fan on its highest setting and record the steady voltage after 30 seconds.
  3. Repeat with 3, 4 and 6 blades, keeping the blade angle and size the same.
  4. Repeat each three times and calculate means.

Safety. Keep fingers and hair away from the fan and rotor; secure the turbine so it cannot fall; switch off the fan before changing blades.

Then evaluate: why do most real wind turbines have three blades?

Criterion-linked questions

Criterion B: inquiring and designing

Criterion C: processing and evaluating

Criterion D: reflecting on the impacts of science

Challenge questions

Harder problems in unfamiliar contexts. Plan before you calculate.

Topic check

Five questions picked at random from the whole topic. Take a new set whenever you like.

Review your mistakes

Questions you got wrong on this device appear here so you can try them again. Answer one correctly and it leaves the list.

Your progress

Tracked separately for each skill, on this device only.

SkillCorrectStatus

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