Lesson Notes By Weeks and Term v4 - SHS 2
ENERGY EFFICIENCY AND CONSERVATION
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ENERGY EFFICIENCY AND CONSERVATION
Download the Lessonotes Mobile Ghana app for faster lesson access on Android and iPhone.
Subject: Engineering
Class: SHS 2
Term: 2nd Term
Week: 20
Grade code: 2.2.3.LI.4
Strand code: 2
Sub-strand code: 3
Content standard code: 2.2.3.CS.1
Indicator code: 2.2.3.LI.4
Theme: ENERGY SYSTEMS
Subtheme: ENERGY EFFICIENCY AND CONSERVATION
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In Ghana, we are all familiar with the importance of electricity. We use it to power our homes, schools, and businesses. We also know the frustration of power outages ('dumsor') and the rising cost of electricity bills, especially with prepaid meters. Energy efficiency and conservation are not just abstract engineering concepts; they are practical skills that help us save money, reduce the strain on our national power grid (managed by bodies like VRA and GRIDCo), and protect our environment. This lesson focuses on thermal equipment—devices that use electricity to produce heat or cold—and how we can use them more intelligently to save energy and money.
A. Core Definitions Energy Conservation: This is the act of using less energy. It is a behavioural change. Example: Turning off the lights when you leave a room. You are conserving energy by choosing not to use it at all. Another example is ironing clothes in a large batch instead of one piece at a time. Energy Efficiency: This means using less energy to perform the *same task*. It is a technological change. Example: Replacing an old, incandescent light bulb with a modern LED bulb. Both light up the room, but the LED bulb uses far less electricity to produce the same amount of light. Buying a new refrigerator with a 5-star energy rating instead of an old, unrated one is another example.
Simple Analogy: Conservation: Deciding to walk to the local shop instead of taking a car. Efficiency: Driving a new, fuel-efficient car to the shop instead of an old, fuel-guzzling one. Both get you there, but one uses less fuel. B. What is Thermal Equipment?
Thermal equipment refers to any appliance that is designed to either heat something up or cool something down. This process of changing temperature is very energy-intensive. Common examples in our environment include: Refrigerators and Freezers Air Conditioners (ACs) Electric Water Heaters Electric Kettles Pressing Irons (Clothing Irons) Microwave Ovens and Electric Ovens C. Energy-Saving Tips for Common Thermal Equipment
This section directly addresses our main indicator. Let's look at specific, practical tips for each appliance. Refrigerators and Freezers Location Matters: Place your fridge away from direct sunlight and heat sources like ovens or cookstoves. Heat makes the fridge's compressor work harder to stay cool. Ensure Good Ventilation: Leave a gap of at least 10 cm (about a hand's width) around the back and sides of the fridge. This allows heat from the coils to dissipate easily. Check the Seals: The rubber seals (gaskets) around the door must be airtight. To test, close the door on a piece of paper or a GH₵ 10 note. If you can pull it out easily, the seal is weak and should be replaced. Don't Overfill, Don't Keep it Empty: A fridge works most efficiently when it's about two-thirds full. An empty fridge loses cold air quickly when opened. A completely packed fridge blocks air circulation. Cool Foods First: Never put hot food directly into the fridge. Let it cool down to room temperature first. Set the Right Temperature: The ideal temperature for a refrigerator is between 2°C and 4°C. For a freezer, it is -18°C. Making it colder than necessary wastes a lot of energy. Minimize Door Opening: Decide what you want before you open the door. Each time you open it, cold air escapes and the compressor has to work to cool it down again. Air Conditioners (ACs) Choose the Right Size: An oversized AC cools the room too quickly without removing humidity, making it feel damp. An undersized AC will run constantly and still not cool the room properly. Match the AC's capacity (measured in BTU) to the room size. Set a Sensible Temperature: Set the thermostat to a comfortable temperature, like 24°C or 25°C, instead of the coldest setting (e.g., 16°C). Every degree cooler increases energy consumption significantly. Clean the Filters: Dirty filters block airflow and make the AC work much harder. Clean the filters at least once a month. Seal the Room: Close all doors and windows when the AC is running. Use curtains or blinds to block direct sunlight from heating the room. Use a Fan: A ceiling or standing fan can help circulate the cool air, allowing you to set the AC to a higher temperature while still feeling comfortable. Electric Kettles and Water Heaters Boil Only What You Need: When making tea, don't fill the kettle to the maximum if you only need one cup. Heating extra water is a direct waste of electricity. Descale Regularly: In areas with "hard" water, a chalky substance called limescale builds up on the heating element. This acts as an insulator, making it take longer (and use more energy) to heat the water. Descale your kettle and water heater periodically with vinegar or a descaling solution. Insulate Your Geyser (Water Heater): For large storage water heaters, wrapping the tank in a special insulation "blanket" can reduce heat loss by 25-45%, saving energy. Use Thermos Flasks: If you need hot water throughout the day, boil it once and store it in a good quality thermos flask instead of re-boiling the kettle multiple times. Pressing Irons Iron in Batches: Don't iron one shirt today and one tomorrow. Accumulate a large pile of clothes and iron them all at once. The iron uses a large amount of energy to heat up initially; doing it once saves this start-up energy. Start with Low-Temperature Fabrics: Begin with clothes that need a lower heat setting (like nylon or silk) and move to those that need higher heat (like cotton and linen). Iron When Damp: Clothes iron more easily when they are slightly damp, requiring less time and energy from the iron. Switch Off Early: Turn the iron off a few minutes before you finish. The residual heat is often enough to iron the last one or two light items. D. Calculating Energy and Cost Savings