Lesson Notes By Weeks and Term - Junior Secondary School 3

TERM: 2ND TERM

SUBJECT: BASIC TECH

CLASS: JSS 3

Reference Materials

• NERDC, INTRODUCTORY TECHNOLOGY FOR JSS, BOOK 3
• EVANS, INTRODUCTORY TECHNOLOGY FOR JSS, BOOK 3

WEEK 9

TOPIC: RENEWABLE ENERGY SOURCES 

CONTENT

• RENEWABLE ENERGY SOURCES
• SOLAR ENERGY (Renewable) 
• PYRANOMETERS
• SOLAR CELLS

RENEWABLE ENERGY SOURCES

The importance of energy in all human activities cannot be overemphasized. We need energy in order to travel from one place to another, to communicate to cook our foods, to light our homes streets, offices etc.

We have non-renewable energy sources i.e. with time they will be exhausted eg fuel. 

Evaluation

1. State the importance of energy to daily human activities

The Renewable energy resources 

These include water power, solar energy, biogas, wind etc

WATER (renewable)

Water flowing down a dam built across a river or stream possesses a considerable amount of mechanical energy which can be converted to hydro-electric power by turbine or electric generator set placed at the end of falling water. Water power is used to turn wheel round as water falls down from the dam and impinges on the wheel. Such rotating wheel possesses mechanical energy which can be used to drive a series pumps to supply water for homes use or irrigation of the land. It can also to be to turn a turbine to generate electric for the community.

Water power system includes water wheel and pelton impulse wheel. The water wheel is useful for converting water power to mechanical power. The pelton impulse wheel works on the basic principles that a high velocity jet of water possesses kinetic energy which can be used to mobbed any object on which it impinges 

Pelton wheel can be used to generate electricity without using gear driving between the wheel and generator 

Evaluation 

1. Briefly explain how water power can be utilized.

SOLAR ENERGY (Renewable) 

One of the forms of energy from the solar energy is the heat energy reaching the earth from the sun. The radiation from the sun has the following characteristics:

1. Solar radiation is intermittent i.e. any point on the earth receive radiation during the day while it cut off as night approaches.
2. The radiation are partially absorbed by atmospheric gases  like oxygen , ozone , carbon dioxide and water vapour .They can also scattered by cloud masses molecules of air , particles  , dust and smoke.
3. The radiation reaching the earth is split into beam radiation or diffuse radiation. Beam radiation reaching surface of the earth without scattering while diffuse is the re-radiation from scattering particles in the atmosphere. The instrument for measuring solar radiation is called radiometer. 

Evaluation 

1. State the characteristics of the radiation from the sun.

PYRANOMETERS

Pyranometers are radiometers designed for measuring the irradiance on a plane surface, normally from solar radiation and lamps. 

The Kipp & Zonen range of thermopile-based pyranometers has been in production for several decades and is respected around the world for the measurement of solar irradiance to World Meteorological Organisation and ISO 9060 standards.

The instruments are used in meteorological research, solar energy research, material testing, climate control in greenhouses, building physics, science and many other applications.

The CMP series of pyranometers have ergonomic features to facilitate installation, maintenance, and exchange for recalibration.

A waterproof socket is fitted for the signature yellow signal cable, which is available in a range of lengths. The integral bubble level is raised to the top of the housing and can be viewed without removing the sun shield. The screw-in drying cartridge can be reactivated with convenient refill packets.

Pyranometers are easy to use, require no power, and are all supplied with calibration certificates that are traceable to WRR (World Radiometric Reference). All instruments have environmental protection class 67.

Evaluation 

1. What is a pyranometer?

SOLAR CELLS

This is otherwise called photovoltaic cell. It converts sunlight directly to electricity. Photovoltaic is capable of converting from 3% to 20% of incidence solar energy into direct current electricity. It behaves like a low voltage battery.

The photo-voltaic cell is a very promising source of electrical energy. Most especially for system which requires small electrical power to drive them 

Evaluation 

1. State the function of a photovoltaic cell.

Reading Assignment

Read RENEWABLE ENERGY SOURCES 

Reference Materials   

1. EVANS, Introductory Technology for JSS, book 3, pages 185 – 190

Weekend Assignment

1. We need energy for the following reasons except (a) to travel from one place to another (b) to cook our foods (c) to light our homes streets, offices (d) to see a spirit
2. The following are examples of renewable energy resources except (a) water power (b) solar energy(c) biogas (d) Petrol
3. Which of the following is used for converting water power to mechanical power (a) the water wheel (b) the water engine (c) the water rod (d) the water pump
4. Which wheel can used to generate electricity without using gear driving between the wheel and generator?  (a) the pelton wheel (b) the water wheel (c) the nekton wheel (d) the drain wheel 
5. The instrument for measuring solar radiation is  called___ (a) radiometer (b) thermometer (c) hydrometer (d) hygrometer 

Theory

1. State the importance of energy to daily human activities.
2. State the function of a photovoltaic cell.