Lesson Notes By Weeks and Term v4 - SHS 3
RENEWABLE ENERGY SYSTEMS
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RENEWABLE ENERGY SYSTEMS
Download the Lessonotes Mobile Ghana app for faster lesson access on Android and iPhone.
Subject: Engineering
Class: SHS 3
Term: 2nd Term
Week: 11
Grade code: 3.2.2.LI.4
Strand code: 2
Sub-strand code: 2
Content standard code: 3.2.2.CS.1
Indicator code: 3.2.2.LI.4
Theme: ENERGY SYSTEMS
Subtheme: RENEWABLE ENERGY SYSTEMS
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In Ghana, we are blessed with abundant natural resources like sunshine, wind, and biomass. However, we often face challenges with our national power grid, leading to "dumsor" (power outages) which affects our homes, schools, and businesses. By learning how to harness renewable energy, we can create our own reliable power sources, reduce our electricity bills, protect our environment, and even create new jobs. This lesson focuses on two practical and accessible renewable technologies: wind power and bioenergy. We will learn not just what they are, but how to design, install, operate, and maintain them on a small scale, empowering us to become part of Ghana's energy solution.
This section covers the core knowledge required to understand, operate, and maintain simple wind and bioenergy systems. Part A: Wind Energy Systems Operating Principle: A wind turbine works by converting the kinetic energy (energy of motion) of the wind into electrical energy. Step 1: The wind blows against the angled blades of the turbine, causing them to turn. This is a conversion from kinetic energy to mechanical energy. Step 2: The rotating blades are connected to a shaft, which spins a generator. Step 3: The generator uses electromagnetic induction to convert the mechanical rotation into electrical energy. Step 4: This electricity can then be used directly, stored in batteries, or fed into the grid. Key Components of a Small-Scale Wind Turbine: Imagine a standing fan, but working in reverse. Instead of using electricity to make wind, it uses wind to make electricity.
| Component | Description & Function | | :--- | :--- | | Blades | Aerodynamically shaped blades (usually 3) that capture the wind's energy and start rotating. The shape is crucial for efficiency. | | Rotor | The central hub where the blades are attached. The blades and hub together form the rotor. | | Nacelle | The housing at the back of the rotor that contains the key components: the generator, gearbox (in some models, to increase rotational speed for the generator), and brake system. | | Tower | The structure that raises the turbine high above the ground to access stronger, more consistent winds, away from obstacles like trees and buildings. | | Foundation | A strong concrete base that secures the tower to the ground and prevents it from falling over in strong winds. | *Electrical Components:* | Charge Controller| Regulates the voltage and current coming from the turbine to prevent overcharging of the batteries. | | Battery Bank | A set of deep-cycle batteries used to store the electricity generated, ensuring power is available even when the wind is not blowing. | | Inverter | Converts the Direct Current (DC) electricity stored in the batteries into Alternating Current (AC) electricity, which is the type used by most household appliances in Ghana (e.g., lights, fans, TVs). | Basic Design and Installation Process (Flowchart Approach):
Design Considerations: Assess Wind Resource: Is there enough wind? Use an anemometer to measure wind speed over time or check data from the Ghana Meteorological Agency for your area. Ideal locations are coastal areas (e.g., Ada, Keta), high plains (e.g., Northern regions), or hilltops. Calculate Power Needs (Load Assessment): How much power do you need? List all appliances, their power rating (in Watts), and how many hours you use them per day. E.g., 3 LED bulbs (10W each) for 5 hours = 3 * 10 * 5 = 150 Watt-hours. Site Selection: Choose a location with no obstructions (trees, tall buildings) for at least 100 metres around. The tower should be tall enough to be above any nearby turbulence.
Installation Steps: Site Preparation & Foundation: Clear the area and dig a pit. Construct a reinforced concrete foundation according to the turbine manufacturer's specifications. Let it cure properly. Tower Assembly: Assemble the tower sections on the ground. This could be a monopole or a lattice tower. Nacelle & Rotor Assembly: Attach the nacelle to the top of the tower. Carefully attach the blades to the rotor hub, and then the rotor to the nacelle. Tower Erection: Use a crane, gin pole, or winch system to carefully raise the fully assembled tower and bolt it securely to the foundation. Electrical Wiring: Run wires from the turbine down the tower. Connect the turbine output to the Charge Controller. Connect the Charge Controller to the Battery Bank. Connect the Battery Bank to the Inverter. Connect the Inverter to your building's main distribution board (consumer unit). Crucially, ensure all connections are tight and well-insulated. Operation and Maintenance Schedule: