← QCE Digital Solutions Unit 3

Sustainability of a solution

How well a solution keeps meeting needs over time without unacceptable environmental, social or economic cost, such as energy use, running and update costs, and social impact.

Part of: QCE Digital Solutions Unit 3 — Innovative Digital Solutions — Module 86

Understanding Sustainability of a solution in QCE Digital Solutions Unit 3

What it does: Listing hosting, licence and update costs shows the economic side of sustainability: whether the owner can afford to keep the solution running over time. Supporting rural users with poor internet and users with disabilities shows a positive social impact, which is part of sustainability. Servers running all the time use electricity and hardware resources, which is an environmental cost. Social impact is about how a solution affects people and communities, including who may be excluded or disadvantaged. Reducing unnecessary processing lowers electricity use and hardware demand. Energy and resource use is one sub-theme of sustainability. A solution that wastes power or needs constant hardware upgrades is less sustainable.

Common mistakes: Energy use in kWh is power multiplied by time, so the line must use * between watts and hours, not +. Correct line: kwh = watts * hours / 1000. == compares values and does not store one, so rate is never defined and the running cost line fails. Use = to assign: rate = 0.30.

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This module's key terms are also in a printable crossword (Modules 251–337) and word search (Modules 194–337).

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Learning
Duo
Which best describes the sustainability of a digital solution?
How fast it runs on the day it is first releasedHow well it keeps meeting needs over time without unacceptable environmental, social or economic cost
Matches
Sustainability = only how fast the program runs today
↓
Sustainability is not just current speed. It covers environmental, social and economic cost over time, such as energy use, update costs and social impact.
Applying
Meanings
Term
sustainability
Meaning
How well a solution keeps meeting needs over time without unacceptable environmental, social or economic cost, such as energy use, running and update costs, and social impact.
Practice
energyUse ← 40
Testing
Gaps
= energyOk and costOk
Check Answer
Spots
2hours = 24
3kwh = watts + hours / 1000

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Quick Questions

1. Which best describes the sustainability of a digital solution?
A. How fast it runs on the day it is first released
B. How well it keeps meeting needs over time without unacceptable environmental, social or economic cost ✓
Sustainability looks at the long term and at environmental, social and economic costs, not just launch-day speed.
2. A school app needs servers running 24/7 even though most students only use it for two hours a day. Which sustainability issue does this raise?
A. Energy and resource use ✓
B. Colour contrast of the interface
Servers running all the time use electricity and hardware resources, which is an environmental cost.
3. A solution is cheap to build but needs expensive licence renewals and frequent paid updates every year. What does this affect?
A. Its long-term running and update costs ✓
B. Its input validation
Ongoing licences and updates are economic costs. A solution that is cheap to build can still be unsustainable if these costs keep growing.
4. Which is an example of social impact when judging sustainability?
A. An app that stores its data in a CSV file
B. An app that only works on new phones excludes students who cannot afford them ✓
Social impact is about how a solution affects people and communities, including who may be excluded or disadvantaged.
5. True or false: a solution is sustainable if it meets today's needs, even if it will need to be replaced every year.
A. False ✓
B. True
Sustainability means continuing to meet needs over time. Constant replacement adds waste and cost.

Match the Pairs

sustainability → How well a solution keeps meeting needs over time without unacceptable environmental, social or economic cost
energy and resource use → The environmental side of sustainability: how much power, hardware and materials a solution consumes while it runs
A sustainable solution keeps its long-term running and update costs affordable → Hosting $40/month + yearly licence $200 + 2 hrs/month updates
Sustainability includes social impact, such as whether the solution is fair to and usable by its community → Social impact: app works offline for rural users and screen readers
Sustainability = only how fast the program runs today → Sustainability is not just current speed. It covers environmental, social and economic cost over time, such as energy use, update costs and social impact.
Server runs at full power 24/7 for 3 users, so it is sustainable → Running a server at full power all day for very few users wastes energy and money, so it is not sustainable. Resource use should match actual need.

Key Term

sustainability
How well a solution keeps meeting needs over time without unacceptable environmental, social or economic cost, such as energy use, running and update costs, and social impact.

Fill in the Blanks

1. sustainability = energyOk and costOk
Hint: Type the name of the criterion variable for how well a solution keeps meeting needs over time at acceptable cost.
2. energyKwh = powerKw * hours
Hint: Type the variable for how long the device runs, which is multiplied by power to give energy used.
3. totalCost = setup + runningCost * years
Hint: Type the arithmetic operator that repeats the yearly running cost across the number of years.
4. socialOk = accessible and affordable
Hint: Type the Boolean operator that makes the social impact check true only when both conditions are met.
5. withinBudget = energyKwh <= budgetKwh
Hint: Type the comparison operator that checks energy use is at or below the allowed budget.

Spot the Error

Question 1
A watts = 50
B hours = 24
C kwh = watts + hours / 1000
D print(kwh)
Line C — Energy use in kWh is power multiplied by time, so the line must use * between watts and hours, not +. Correct line: kwh = watts * hours / 1000.
Question 2
A kwh = 1.2
B rate == 0.30
C cost = kwh * rate
D print(cost)
Line B — == compares values and does not store one, so rate is never defined and the running cost line fails. Use = to assign: rate = 0.30.
Question 3
A def yearly_cost(monthly)
B return monthly * 12
C print(yearly_cost(40))
Line A — A function definition must end with a colon. Without it Python raises a SyntaxError, so the running-cost function never works. It should be def yearly_cost(monthly):
Question 4
A fee = 50
B years = 5
C total = 200 + fee * year
D print(total)
Line C — The variable is called years, not year. Using an undefined name causes a NameError, so the long-term update cost is never calculated. It should be total = 200 + fee * years.
Question 5
A users = 500
B offline = 120
C share = offline / users * 100
D print(share + '% excluded')
Line D — share is a number, and a number cannot be added to a string with +. This causes a TypeError when reporting the social impact. Use a comma instead: print(share, '% excluded').

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