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: 9
Grade code: 3.2.2.LI.3
Strand code: 2
Sub-strand code: 2
Content standard code: 3.2.2.CS.1
Indicator code: 3.2.2.LI.3
Theme: ENERGY SYSTEMS
Subtheme: RENEWABLE ENERGY SYSTEMS
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Ghana is a growing nation with an increasing demand for electricity for our homes, schools, and industries. For many years, we have relied heavily on hydroelectric power (like the Akosombo Dam) and thermal plants. However, these have challenges, including vulnerability to rainfall patterns and the high cost of fuel. This lesson explores two powerful alternatives: wind and bioenergy. These renewable energy sources offer a path to a more stable, sustainable, and environmentally friendly energy future for Ghana.
This lesson focuses on two key renewable energy technologies suitable for various scales in Ghana: Wind Energy and Bioenergy (specifically Biogas). A. Wind Energy Systems
A wind energy system converts the kinetic energy (energy of motion) of the wind into useful mechanical or electrical energy. Principle of Operation: Wind blows across the blades of a turbine, creating an aerodynamic lift force (similar to an aeroplane wing). This lift causes the blades to rotate. The rotating blades spin a shaft connected to a generator. The generator then converts this mechanical rotation into electricity. Key Components of a Wind Turbine: Blades: Aerodynamically shaped structures designed to catch the wind and create lift. Most modern turbines have three blades. Rotor: The combination of the blades and the central hub to which they are attached. Nacelle: The housing at the top of the tower that contains the main machinery: Gearbox: Increases the slow rotational speed of the blades to the high speed required by the generator. Generator: A machine that converts rotational mechanical energy into electrical energy. Tower: The structure that supports the nacelle and rotor high above the ground to access stronger, more consistent winds. Foundation: A large concrete base that anchors the tower securely to the ground. Control System: A system that monitors and controls the turbine, including turning it to face the wind (yaw control) and adjusting the blade angle (pitch control) in high winds. Simple Design and Installation Considerations:
a. Site Selection: This is the most critical step. Wind Speed: The site must have consistent and adequate wind speed. Power is proportional to the cube of wind speed (more on this below). Coastal areas like Ada, Ningo, and the Kwahu ridge are known for good wind potential. Obstructions: The site should be clear of tall buildings and trees that can create turbulence and block wind flow. A general rule is to place the turbine at least 10 metres higher than any obstacle within a 100-metre radius. Land Use: The land must be available and suitable for constructing a foundation and for turbine access.
b. Sizing and Power Calculation: The power available from the wind is calculated using the following formula: