DSE Geography | Energy and Resource Management Lesson-Prep Guide (Tutor Edition)

DSE Geography | Energy and Resource Management Lesson-Prep Guide (Tutor Edition) | Mix, Efficiency, Capacity Factor

2026-11-02

Tutor lesson-prep guides · Secondary Geography

Students hear “renewable” and write “clean and green”, while the question wants capacity factors and unit costs. This lesson drags the topic back to tables and arithmetic.

Objectives — Students can: (1) turn an energy table into fossil and low-carbon shares; (2) use a capacity factor to compute a wind farm annual output and the homes it serves; (3) explain with an efficiency gap why the same kilowatt-hour needs different fuel and carbon.

01 Prerequisites (3-minute check)

If any of these fails, fix it before the lesson starts.

Skill	Quick check	Pass mark
Energy types	What counts as primary energy	Fossil, nuclear, renewable
Percentages	How to convert an amount to a share	Item divided by total
Units	How MW differs from MWh	Power versus energy, an hour apart

02 Lesson flow (60 minutes)

Time	Stage	Tutor does	Student does
0-8 min	Energy mix	Add six sources and convert to shares	Both groups total 100
8-20 min	Efficiency gap	One kilowatt-hour from 40% and 60% plant	33.3% fuel saved
20-34 min	Capacity factor	100 MW farm at 40%	350400 MWh a year
34-46 min	Students compute	Same farm at 25%	Recompute unaided
46-54 min	Policy judgement	Two for and two against, each with a figure	One figure per reason
54-60 min	Exit check	Three quick questions	All three right

03 Teaching script (read it out)

Scene 1: The mix is a percentage table, not a slogan

Six cells: coal 30, gas 25, oil 20, nuclear 10, renewables 15, total 100.
The three fossil cells add to 75%; the two low-carbon cells to 25%.
Students usually add coal and oil only and forget gas, which is still a fossil fuel: the mix answer always starts with the two shares.

Ask students: why gas still counts as fossil (it burns and emits, only less).

Scene 2: The efficiency gap is where fuel is saved

For one kilowatt-hour, a 40% plant burns 1 / 0.40 = 2.5 units; a 60% plant burns 1 / 0.60 = 1.667 units.
Saving = (2.5 – 1.667) / 2.5 = 33.3%; this line earns more than the phrase “higher efficiency reduces emissions”.
Link it to carbon intensity: coal 0.9 kg per kWh, gas 0.4 kg per kWh, so changing fuel changes emissions.

Ask students: why the saving is not 20% (the denominator is the old plant).

Scene 3: The capacity factor sets real output

A 100 MW farm running 8,760 hours would make 876,000 MWh, but wind does not blow flat out all year.
At a 40% capacity factor the equivalent full-load hours are 3504, giving 350400 MWh a year; at 4000 kWh per home that serves about 87600 homes.
“Wind is unreliable” becomes an answer only when written as “capacity factor 40%, so 60% of the time output is below nameplate”.

Ask students: why solar capacity factors in Hong Kong sit below wind (sun hours and cloud).

04 Question types and worked steps

Type	Example	Steps	Answer
Calculation	Energy shares	Each item divided by the total	75% fossil
Calculation	Annual output	Nameplate x 8,760 x capacity factor	350400 MWh
Calculation	Fuel saving	(old use – new use) / old use	33.3%
Essay	Energy policy	Reliability, cost, carbon, siting: one line each	One figure per line

Sanity check (teach this): Shares must total 100; a total of 99 or 101 means a rounding slip.
A capacity factor lies between 0 and 1; anything above 876,000 MWh is a multiplication error.
Keep the denominator consistent: the old plant, not the new one.
Carbon intensity is kilograms per kWh, not per year, unless multiplied by annual use.

05 Independent practice (3 questions)

Question	Answer	What to watch
Fossil share (coal 30, gas 25, oil 20)	75%	30 + 25 + 20
Output of 100 MW at 40% capacity factor	350400 MWh	100 x 8,760 x 0.40
Fuel saved from 40% to 60% efficiency	33.3%	(2.5 – 1.667) / 2.5

06 Common mistakes and what to say

Mistake	Student writes	Say this
Counting coal and oil only	Fossil 50%	Gas burns and emits too; skipping it loses 25 points of share.
Treating MW as MWh	“Annual output 100 MWh”	MW is power; energy needs an hour attached.
Assuming 100% capacity factor	Writing 876,000 MWh	A farm is not at full load all year.
Inverting the efficiency sum	“Saving 20%”	The denominator is the old 2.5 units, not the new 1.667.

07 Homework (paper, section and question numbers)

Paper 1 data question: energy mix chart (Q3-Q5) — Shares first, then the change
Paper 2 essay: expand renewables? (Q8) — Four lines, one figure each
All lesson-prep guides — Compare the ten-section structure

08 Exit check (last 5 minutes)

Question	Answer	Decision
Fossil share	75%	All three right: next chapter
Annual output at 40%	350400 MWh	One wrong: redo the 8,760 idea
Fuel saved	33.3%	Two wrong: return to act two

09 Tutor FAQ

Why split fossil from low-carbon?

Mark schemes reward comparison at the mix level, not a list of numbers.

Can a capacity factor exceed 50%?

Yes for offshore wind and hydro, but solar in Hong Kong usually stays below 20%.

Is nuclear renewable?

No; it is low-carbon but fuel-limited, so keep it separate.

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A TutorZone lesson-prep guide. Written by the TutorZone team; questions and lesson flow are original and are not taken from any school or publisher material.