Energy resources and evidence-based choices

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課程筆記

Big idea: energy resources and evidence-based choices

Key concept: Systems. Resources differ in availability, power output, reliability and environmental effects. Renewable means replenished on a human timescale, not impact-free.
Related concepts: Models and evidence. Use a scientific explanation to make predictions, then test it against observations.
Global context: Scientific and technical innovation. Energy planning combines supply requirements with environmental and economic evidence.

Energy from the Sun

The Sun transfers energy to Earth by electromagnetic radiation (mostly visible light and infrared).
Most energy resources on Earth come indirectly from the Sun: wind, waves, rain (hydroelectric), and plant growth (biofuels and fossil fuels).
Resources not from the Sun: geothermal (Earth's core heat), nuclear (elements in Earth's crust), tidal (mainly Moon's gravity).
Solar cells (photovoltaic) convert sunlight directly into electricity using semiconducting materials.
Solar panels use sunlight to heat water for domestic use; solar furnaces focus sunlight to boil water for steam turbines.
Advantages of solar: renewable, no pollution, reliable in sunny regions, can be used in remote areas, low running costs.
Disadvantages: low energy density (large area needed), intermittent, expensive to install, low efficiency (20–40%).

Solar panels use energy from sunlight to heat water

Wind Energy

Wind turns turbines → generator → electricity; energy transfers: kinetic (wind) → kinetic (turbine) → kinetic (generator) → electrical.
Advantages: renewable, no pollution, relatively cheap, high efficiency (~50%), land can still be used for farming.
Disadvantages: unreliable (wind not constant), visual pollution, each turbine produces little power, needs high-voltage lines.

Wind turbines use energy from the wind to generate electricity

Energy from Fuels: Fossil Fuels

Fossil fuels: coal, natural gas (methane), crude oil (refined into petrol, diesel). Formed from remains of plants/animals; chemical energy originally from sunlight via photosynthesis.
Advantages: reliable, responsive (can be turned on/off), well-established infrastructure, safe to store.
Disadvantages: non-renewable (millions of years to form, predicted to run out in ~200 years), burning releases CO₂ (greenhouse gas) and SO₂ (acid rain), extraction damages environment, expensive to build/decommission.
Uses: transport, electricity generation (burned to heat water → steam → turbine → generator), heating.

Electricity generation in a coal-fired power station

Energy from Fuels: Biofuels

Biofuels (ethanol, methane) made from plant matter; energy from sunlight stored chemically.
Advantages: renewable, considered carbon neutral (plants absorb CO₂ during growth), no SO₂ produced.
Disadvantages: requires land and resources for crops, only half the energy density of fossil fuels, controversial carbon neutrality (land could have been used for food).

Energy from Fuels: Nuclear Fuel

Nuclear fission splits large nuclei (e.g., uranium) into smaller ones, releasing energy; used to heat water → steam → turbine → generator.
Advantages: no atmospheric pollution, reliable, responsive, massive power output (twice that of fossil fuel plant), high energy density.
Disadvantages: non-renewable (finite uranium), produces radioactive waste (stored for thousands of years), expensive to build and decommission, risk of accidents.

Energy from Water

Wave power: underwater turbines turned by wave motion; tidal power: tidal barrages store water at height, released through turbines.
Advantages: renewable, no pollution, no fuel costs, tidal is reliable and predictable, high efficiency (~80%), responsive.
Disadvantages: few suitable locations (estuaries), interferes with shipping and habitats, technology not yet large-scale, wave power unreliable.
Hydroelectric dams: water stored in reservoir has gravitational potential energy; flowing water turns turbines.
Advantages: reliable, responsive, cheap to run, large electricity output, renewable.
Disadvantages: flooding valleys destroys habitats and settlements, expensive to build, drought can affect supply.

Geothermal Energy

Heat from Earth's core heats rocks; water injected into shafts is heated and returned as steam/hot water to generate electricity or heat homes.
Advantages: renewable, reliable (rocks hot for thousands of years).
Disadvantages: few suitable locations (tectonic activity), can release methane (greenhouse gas), expensive to build, small scale, low efficiency (~12%).

Nuclear Fusion

Nuclear fusion fuses hydrogen nuclei into helium, releasing massive energy (powers the Sun).
Requires extremely high temperatures and pressures; currently research aims to sustain fusion at lower temperatures.
Potential: virtually limitless, carbon-free electricity; but currently reactions require nearly as much energy as they release.

Think like a scientist

Compare published generation datasets for different energy resources using the same reporting period and system boundaries.
Comparison: the energy resource being assessed. Outcome: energy output and lifecycle impacts.
Control: use consistent units and comparison boundaries. Explain why this makes the comparison fairer.
Evidence: Use a consistent method, repeated observations where appropriate and a table with labelled quantities and units. Keep unexpected results and investigate their cause.
Safety: Practical activities need teacher supervision and an appropriate risk assessment. Use the provided data or simulation where the investigation specifies it.
Inquiry task: State a testable question, predict the outcome using the science, then explain how your observations would support or challenge the prediction.

Evaluate the science

Energy planning combines supply requirements with environmental and economic evidence.
A single metric cannot decide every energy choice; reliability, storage, land use, cost and lifecycle emissions also matter.
Evaluation task: Link your conclusion to evidence, identify a limitation and suggest a specific improvement. Distinguish a measured result from an explanation of its cause.

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練習題

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1.Which energy resource does not use the Sun as the source of its energy?
Easy
- AHydroelectric
- BWind
- CNuclear
- DCoal
2.Which energy resource involves splitting heavy nuclei?
Easy
- ANuclear fission
- BGeothermal
- CBiomass
- DNuclear fusion
3.Which energy resource does not release greenhouse gases?
Easy
- AOil
- BHydro-electric power
- CBiofuel
- DCoal
4.Which disadvantage does not apply to geothermal energy?
Medium
- AExpensive to build
- BFew suitable locations
- CCan result in the release of greenhouse gases
- DNot reliable
5.Which energy source relies on radiation from the Sun?
Easy
- AFossil fuels
- BNuclear fission
- CTidal power
- DGeothermal energy
6.Which source of energy is renewable?
Easy
- Acoal
- Bnatural gas
- Coil
- Dwind
7.Which energy resource does not originate from the Sun's radiation?
Easy
- Atidal power
- Bwind power
- Cwave power
- Dhydroelectric power
8.Listed below are some energy resources. W wind powering a turbine X water falling through a hydroelectric turbine Y alcohol made from crops which have been grown for burning in a biomass generator Z uranium for nuclear fission reactors Which of the resources are renewable?
Medium
- AW, X and Z
- BW and X
- CW, X and Y
- DW, X, Y and Z

複習筆記

## Big idea: energy resources and evidence-based choices - **Key concept: Systems.** Resources differ in availability, power output, reliability and environmental effects. Renewable means replenished on a human timescale, not impact-free. - **Related concepts: Models and evidence.** Use a scientific explanation to make predictions, then test it against observations. - **Global context: Scientific and technical innovation.** Energy planning combines supply requirements with environmental and economic evidence. ## Energy from the Sun - The Sun transfers energy to Earth by **electromagnetic radiation** (mostly visible light and infrared). - Most energy resources on Earth come indirectly from the Sun: wind, waves, rain (hydroelectric), and plant growth (biofuels and fossil fuels). - Resources **not** from the Sun: **geothermal** (Earth's core heat), **nuclear** (elements in Earth's crust), **tidal** (mainly Moon's gravity). - **Solar cells** (photovoltaic) convert sunlight directly into electricity using semiconducting materials. - **Solar panels** use sunlight to heat water for domestic use; **solar furnaces** focus sunlight to boil water for steam turbines. - Advantages of solar: renewable, no pollution, reliable in sunny regions, can be used in remote areas, low running costs. - Disadvantages: low energy density (large area needed), intermittent, expensive to install, low efficiency (20–40%). ## Wind Energy - Wind turns **turbines** → **generator** → electricity; energy transfers: kinetic (wind) → kinetic (turbine) → kinetic (generator) → electrical. - Advantages: renewable, no pollution, relatively cheap, high efficiency (~50%), land can still be used for farming. - Disadvantages: unreliable (wind not constant), visual pollution, each turbine produces little power, needs high-voltage lines. ## Energy from Fuels: Fossil Fuels - Fossil fuels: **coal**, **natural gas** (methane), **crude oil** (refined into petrol, diesel). Formed from remains of plants/animals; chemical energy originally from sunlight via photosynthesis. - Advantages: reliable, responsive (can be turned on/off), well-established infrastructure, safe to store. - Disadvantages: **non-renewable** (millions of years to form, predicted to run out in ~200 years), burning releases **CO₂** (greenhouse gas) and **SO₂** (acid rain), extraction damages environment, expensive to build/decommission. - Uses: transport, electricity generation (burned to heat water → steam → turbine → generator), heating. ## Energy from Fuels: Biofuels - Biofuels (ethanol, methane) made from plant matter; energy from sunlight stored chemically. - Advantages: **renewable**, considered **carbon neutral** (plants absorb CO₂ during growth), no SO₂ produced. - Disadvantages: requires land and resources for crops, only half the energy density of fossil fuels, controversial carbon neutrality (land could have been used for food). ## Energy from Fuels: Nuclear Fuel - **Nuclear fission** splits large nuclei (e.g., uranium) into smaller ones, releasing energy; used to heat water → steam → turbine → generator. - Advantages: no atmospheric pollution, reliable, responsive, massive power output (twice that of fossil fuel plant), high energy density. - Disadvantages: **non-renewable** (finite uranium), produces **radioactive waste** (stored for thousands of years), expensive to build and decommission, risk of accidents. ## Energy from Water - **Wave power**: underwater turbines turned by wave motion; **tidal power**: tidal barrages store water at height, released through turbines. - Advantages: renewable, no pollution, no fuel costs, tidal is reliable and predictable, high efficiency (~80%), responsive. - Disadvantages: few suitable locations (estuaries), interferes with shipping and habitats, technology not yet large-scale, wave power unreliable. - **Hydroelectric dams**: water stored in reservoir has gravitational potential energy; flowing water turns turbines. - Advantages: reliable, responsive, cheap to run, large electricity output, renewable. - Disadvantages: flooding valleys destroys habitats and settlements, expensive to build, drought can affect supply. ## Geothermal Energy - Heat from Earth's core heats rocks; water injected into shafts is heated and returned as steam/hot water to generate electricity or heat homes. - Advantages: **renewable**, reliable (rocks hot for thousands of years). - Disadvantages: few suitable locations (tectonic activity), can release methane (greenhouse gas), expensive to build, small scale, low efficiency (~12%). ## Nuclear Fusion - **Nuclear fusion** fuses hydrogen nuclei into helium, releasing massive energy (powers the Sun). - Requires extremely high temperatures and pressures; currently research aims to sustain fusion at lower temperatures. - Potential: virtually limitless, carbon-free electricity; but currently reactions require nearly as much energy as they release. ## Think like a scientist - Compare published generation datasets for different energy resources using the same reporting period and system boundaries. - **Comparison:** the energy resource being assessed. **Outcome:** energy output and lifecycle impacts. - **Control:** use consistent units and comparison boundaries. Explain why this makes the comparison fairer. - **Evidence:** Use a consistent method, repeated observations where appropriate and a table with labelled quantities and units. Keep unexpected results and investigate their cause. - **Safety:** Practical activities need teacher supervision and an appropriate risk assessment. Use the provided data or simulation where the investigation specifies it. - **Inquiry task:** State a testable question, predict the outcome using the science, then explain how your observations would support or challenge the prediction. ## Evaluate the science - Energy planning combines supply requirements with environmental and economic evidence. - A single metric cannot decide every energy choice; reliability, storage, land use, cost and lifecycle emissions also matter. - **Evaluation task:** Link your conclusion to evidence, identify a limitation and suggest a specific improvement. Distinguish a measured result from an explanation of its cause.

Wind Energy: Wind turns **turbines** → **generator** → electricity; energy transfers: kinetic (wind) → kinetic (turbine) → kinetic (generator) → electrical.
Water Energy: Describe how wave, tidal, and hydroelectric power generate electricity, and evaluate their advantages and disadvantages.
Nuclear Fission: Describe nuclear fission as an energy source, and evaluate its advantages and disadvantages.
Biofuels: Describe the production and use of biofuels, and evaluate their advantages and disadvantages including carbon neutrality.
Nuclear Fusion: **Nuclear fusion** fuses hydrogen nuclei into helium, releasing massive energy (powers the Sun).
Geothermal Energy: Heat from Earth's core heats rocks; water injected into shafts is heated and returned as steam/hot water to generate electricity or heat homes.
Solar Energy: Describe how solar energy is harnessed using solar cells and solar panels, and evaluate their advantages and disadvantages.
Fossil Fuels: Describe the formation, uses, and environmental impact of fossil fuels, and evaluate their advantages and disadvantages.
Designing scientific inquiries: Plan a fair comparison: Compare published generation datasets for different energy resources using the same reporting period and system boundaries.
Evaluating evidence and impacts: Energy planning combines supply requirements with environmental and economic evidence. A single metric cannot decide every energy choice; reliability, storage, land use, cost and lifecycle emissions also matter.
Energy from the Sun: The Sun transfers energy to Earth by **electromagnetic radiation** (mostly visible light and infrared).
Energy from Fuels: Fossil Fuels: Fossil fuels: **coal**, **natural gas** (methane), **crude oil** (refined into petrol, diesel). Formed from remains of plants/animals; chemical energy originally from sunlight via photosynthesis.
Energy from Fuels: Biofuels: Biofuels (ethanol, methane) made from plant matter; energy from sunlight stored chemically.
Energy from Fuels: Nuclear Fuel: **Nuclear fission** splits large nuclei (e.g., uranium) into smaller ones, releasing energy; used to heat water → steam → turbine → generator.
Energy from Water: **Wave power**: underwater turbines turned by wave motion; **tidal power**: tidal barrages store water at height, released through turbines.
electromagnetic radiation: The Sun transfers energy to Earth by **electromagnetic radiation** (mostly visible light and infrared).

字卡

Which energy resource does not use the Sun as the source of its energy?

Nuclear Nuclear energy comes from nuclear fission of elements in the Earth's crust, not from the Sun. Hydroelectric, wind, and coal all ultimately derive from solar energy.

Which energy resource involves splitting heavy nuclei?

Nuclear fission Nuclear fission is the splitting of a heavy nucleus into two smaller nuclei, releasing energy. Nuclear fusion is the joining of small nuclei.

Which energy resource does not release greenhouse gases?

Hydro-electric power Hydro-electric power uses moving water to generate electricity and does not burn fuel, so no greenhouse gases are released. Oil, biofuel, and coal all release CO₂ when burned.

Which disadvantage does not apply to geothermal energy?

Not reliable Geothermal energy is reliable because the rocks remain hot for thousands of years. The other options are disadvantages: expensive to build, few suitable locations, and can release methane (a greenhouse gas).

Which energy source relies on radiation from the Sun?

Fossil fuels Fossil fuels store energy originally from sunlight via photosynthesis. Nuclear fission, tidal power, and geothermal energy do not originate from the Sun's radiation.

Which source of energy is renewable?

wind Wind is renewable because it is replenished naturally. Coal, natural gas, and oil are non-renewable fossil fuels.

Which energy resource does not originate from the Sun's radiation?

tidal power Tidal power comes mainly from the gravitational attraction of the Moon, not the Sun. Wind, wave, and hydroelectric power all derive from solar energy.

Listed below are some energy resources. W wind powering a turbine X water falling through a hydroelectric turbine Y alcohol made from crops which have been grown for burning in a biomass generator Z uranium for nuclear fission reactors Which of the resources are renewable?

W, X and Y Wind (W), hydroelectric (X), and biomass (Y) are renewable. Uranium (Z) is non-renewable because it is a finite resource.

Which statement best describes nuclear fuel as an energy source?

Reliable, non-renewable and available for large scale production Nuclear fuel is reliable (can produce power consistently), non-renewable (finite uranium), and suitable for large-scale electricity generation.

Which statement best describes the differences between solar cells and solar panels?

Solar panels use energy from the sun to heat water and solar cells use energy from the sun to generate electricity Solar panels (thermal) heat water; solar cells (photovoltaic) generate electricity directly from sunlight.

What feature do geothermal, hydroelectric and nuclear energy sources share?

Cause rotation in a generator All three involve rotating a generator to produce electricity. Geothermal and nuclear use steam; hydroelectric uses flowing water directly.

Which statement about nuclear fuel is correct?

Nuclear waste must be stored for thousands of years Radioactive waste from nuclear fission must be stored safely for thousands of years. Nuclear fusion is not yet used for large-scale generation; fission does not provide 70% of UK energy.

A hydroelectric power station has a reservoir of water at a height of 50 m above the turbines. The water flows down and turns the turbines. Which energy transfer takes place as the water falls?

gravitational potential to kinetic Water stored at a height has gravitational potential energy. As it falls, this is converted to kinetic energy. The moving water then turns the turbine.

The efficiency of a solar cell is 20%. If 500 J of solar energy fall on the cell, how much electrical energy is produced?

100 J Efficiency = useful output energy / total input energy × 100%. So useful output = (20/100) × 500 J = 100 J.

A solar cell and a wind turbine's energy output vary over 24 hours. The solar cell produces no energy between 18:00 and 06:00. The wind turbine produces a steady output of 2 kW from 00:00 to 12:00, then drops to 0.5 kW from 12:00 to 24:00. What is the total energy generated by the wind turbine in 24 hours?

30 kWh Energy = power × time. From 00:00 to 12:00 (12 h) at 2 kW: 2 × 12 = 24 kWh. From 12:00 to 24:00 (12 h) at 0.5 kW: 0.5 × 12 = 6 kWh. Total = 24 + 6 = 30 kWh.

Which energy resource uses the kinetic energy of moving air to generate electricity?

wind power Wind turbines convert the kinetic energy of moving air (wind) into electrical energy.

How would you design the inquiry for energy resources and evidence-based choices?

Compare published generation datasets for different energy resources using the same reporting period and system boundaries. Compare the energy resource being assessed; record energy output and lifecycle impacts; use consistent units and comparison boundaries.

What limitation matters when applying energy resources and evidence-based choices?

A single metric cannot decide every energy choice; reliability, storage, land use, cost and lifecycle emissions also matter.

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Wind speed (m/s)	Power output (W)
2.0	0.5
4.0	4.0
6.0	13.5
8.0	32.0