THIRD TERM E-LEARNING NOTE

SUBJECT: BASIC TECHNOLOGY                                                                   

  CLASS J.S 3

SCHEME OF WORK

WEEK             TOPIC

1. ENERGY SOURCES- SOLAR CELLS AND ELECTRICITY
2. ENERGY SOURCES- BIOGAS PRODUCTION          
3. ENERGY SOURCES- WINDMILL            
4. DEVICES FOR PLANTING, HARVESTING AND STORAGE OF AGRICULTURAL PRODUCTS.             
5. SANITAION
6. REVISION              
7. JSCE! JSCE!!             

Reference Materials:

1. EVANS, Introductory Technology For JSS, Book 3.
2. NERDC, Introductory Technology For JSS, Book 3.

WEEK 1                          DATE_________________

TOPIC: ENERGY SOURCES- Solar Cells and Solar Electricity

CONTENT

• Solar Energy
• Solar cell
• Solar Electricity

INTRODUCTION

Solar energy produces heat energy along with light energy reaching the earth from the sun. The sun, with a surface temperature of about 67620C radiates about 353 kW of solar power to an area of 1m2 on the earth’s atmosphere.

SOLAR CELL

While the STPP utilizes the heating effects to produce steam, which drives the turbine to generate electricity, there is a device called PHOTOVOLTAIC CELL OR SOLAR CELL, which converts the sunlight directly to electricity. Photovoltaic cells are capable of converting from 3% to 20% of the incident solar energy into DC (direct current) electricity. It behaves very much like a low –voltage (≈ 0.65V) battery.

Principle of operation

The working principle of photovoltaic cell is quite simple. Sunshine comes in little bundles of energy called photons. This photons enters the semi-conducting material (e.g. high purity silicon), it is absorbed. The absorbed photon breaks the electronic bond of the material to release electron. The entity which is left after the electron is releases is called a hole. It is positively charged. Thus, the absorbed photons create free electrons (negative charges) and holes (positive charges), which move freely in the semiconductor material. By carefully a small quantity of another material called the dopant to the semiconductor material, free electrons in the semiconductor material are separated to one side and holes to the other side. Thus, the ends of the semiconductor material serve as the positive and negative terminals respectively. These semiconductor materials can be connected in parallel and series as required.

Evaluation

1. State the two forms of energy emitted from the sun
2. Define the following: (i) Dopant (ii) hole (iii) pole
3. Explain the principle of operation of a solar cell

SOLAR ELECTRICITY

Solar electricity is the electricity generated from the energy beamed from the sun to the earth. Solar electricity utilizes the heating effect of the sun to generate electricity. This is called thermal collection.

Principle of operation 

In the thermal collection process, the solar heat is used heat a fluid such as water, Freon etc, to a very high temperature. The high temperature fluid at high pressure uses its appreciably mechanical energy (just like the mechanical energy possessed by the falling water from a dam) to turn, for example, the turbine of an electric generator, which operates in this manner is called Solar Thermal Power Plant (STPP) One of the major. To attain a high temperature, concentrating system is used to concentrate the solar energy at a point, so that the temperature of the point will be very high.

Solar Thermal Power Plant

Evaluation

1. What form of energy is used by solar electricity?
2. Explain the principle of operation of a solar electricity

Reading Assignment

Read “RENEWABLE ENERGY –SOLAR ENERGY”

Reference Materials:

• EVANS, INTRODUCTORY TECHNOLOGY FOR JSS, BOOK 3, pages 185-190

Weekend Assignment

1. _____ converts solar directly to electricity (a) Generator (b) Fan (c) Photovoltaic cell  (d) inverter
2. Photocells are made from _______ materials (a) hydrogen (b) oxygen (c) semiconductor (d) proton
3. Photocell absorbs ____ from the sun (a) holes (b) poles (c) photons (d) electrons
4. Solar electricity uses the following devices except (a) turbine-generator (b) concentrating system (c) boiler  (d) photocell
5. Sun generates both (a) light and heat energy (b) mechanical and light energy (c) sound and heat (d) light and kinetic energy

Theory

1. Explain the principle of operation of a solar cell
2. Explain the principle of operation of a solar electricity

Week 2                          DATE________________

TOPIC: ENERGY SOURCES- BIOGAS PRODUCTION          

CONTENT:

• Introduction to biogas technology
• Biogas
• The production of biogas from waste
• Biogas plant

Introduction

Cooking gas used as domestic fuel is a liquidified-petroleum gas (LPG) from oil refineries. This is main source of our cooking gas. However, it is possible to get cooking gas from other sources. One of such sources is biogas.

BIOGAS

Biogas is produced from the fermentation of animal wastes by bacteria in an oxygen-free atmosphere. The wastes, which can be used to produce biogas, are human excretion, dungs (from cow, goat, sheep and pigs), poultry dropping, urban refuse, and agricultural wastes. The process of releasing gas fuel by bacterial digestion of wastes is scientifically referred to as biosynthesis. Hence, the gas released from the process is called biogas.

Evaluation

1. State main source cooking gas.
2. Briefly explain biogas

The Production of Biogas from Wastes.

Biogas plant consists of two parts namely:

1. The digester and
2. The floating gas storage tank.

The digester contains the wastes to be digested. The waste is mixed properly into slurry, and then fed into the digester through the waste inlet. The waste is then left in the digester to ferment from a period ranging from 7-14 days. As a result of fermentation, biogas is released, and collected in the floating storage tank which floats in the digester.

As fermentation progresses, more gas is released and collected in the floating storage tank. The gas rises up in the digester as the gas pressure increases. The biogas flows out under its own pressure through the gas outlet. If such a digester is situated at the back of a kitchen, biogas is connected directly to the gas stove to be used as cooking gas.

Biogas plant

Evaluation

1. Explain the importance of bacteria in the biogas production
2. Briefly discuss activities in the following during biogas production (i)  the digester (ii) the floating gas storage tank.

Reading Assignment

Read “RENEWABLE ENERGY –BIOGAS”

Reference Materials:

• EVANS, INTRODUCTORY TECHNOLOGY FOR JSS, BOOK 3, pages 190-191

Weekend Assignment

1. Cooking gas used as domestic fuel is a (a) hydrogen gas (b) carbon dioxide gas (c) liquidified-petroleum gas (d) neon gas
2. Another source of cooking gas is ____ (a) biogas (b) chemgas (c) physogas (d) mathgas
3. Which of the following is not a waste used for biogas production (a) dung from cow (b) poultry dropping (c) urban refuse (d) oil spillage
4.  Biogas plant consists of two parts namely (a) the digester and the floating gas storage tank. (b) mixer (c) gas jar (d) porous pot
5. The waste is then left in the digester to ferment from a period ranging from (a) 7-14 days (b) 28- 35 days (c)14-21 days (d) 21-28 days

Theory

1. Define biogas
2. Explain the operation of biogas plant

Week 3                                           DATE_________________

TOPIC: ENERGY SOURCES- WINDMILL            

CONTENT

• Wind energy
• Windmill
• Windmill power plant

WIND ENERGY

Wind is another form of energy just like the solar radiation beamed from the sun, the water behind a dam, the stored energy in fuel.

When wind blows through open windows and doors into our rooms, we sometimes notice that ceiling fan can start to rotate even though it is not switched on.

Children make propeller with paper and broom stick. The blades revolve freely on the main shaft. As you hold the ma in shaft in your hand and run fast, the blades rotate at a speed that depends on how fast you can run.

Evaluation

1. Define wind energy
2. Demonstrate the power of wind energy.

Thus, if a propeller with the blades firmly attached to its main shaft is installed on top of a mast. When the wind blows, it will rotate the blades and hence the shaft to which they are firmly connected. Thus, this system has converted the wind energy to the mechanical energy of the rotating blades and the shaft. Such mechanically energy can be used directly for grinding, pumping water e.t.c. To generate electricity, the above system is joined to an electric generator, which converts its mechanical energy to electrical energy.

Evaluation

1. Explain how wind can be classified as a renewable energy source
2. Give practical examples that proved that wind could be strong.

How to generate electricity using a windmill

Wind mill receives its source of energy from the wind blowing. Therefore, the blades of the windmill must be placed in such a way it come receive maximum wind. The blades begin to turn converting the wind energy to mechanical energy. A turbine-generator is connected to the blades by a drive mechanism. The generator, will in-turn, produce electricity.

Wind power plant

Evaluation

1. State the important components of a wind power plant
2. Briefly explain the operation of a wind power plant

Reading Assignment

Read “RENEWABLE ENERGY –WIND ENERGY”

Reference Materials:

• EVANS, INTRODUCTORY TECHNOLOGY FOR JSS, BOOK 3, pages 191-192

Weekend Assignment

1. A windmill converts the kinetic energy of wind into the ___ of a rotating shaft (a) mechanical energy (b) solar energy (c) nuclear (d) wind energy
2. Energy from the windmill can be used for the following except (a) grinding (b) pumping (c) generating electricity (d) ploughing
3. The speed of the shaft of a windmill depends on the (a) length of the shaft (b) strength of the wind (c) power of the turbine (d) solar energy
4. When the wind blows, the blade will (a) rotate  (b) revolve (c) slant (d) slope
5. Generator converts (a) electrical to mechanical energy (b) mechanical to electrical energy (c) kinetic to potential energy (d) electrical to potential energy

Theory

1. Briefly explain wind energy as renewable energy source
2. Describe how windmill can be used to generate electricity.

WEEK 4                               DATE__________________

TOPIC: DEVICES FOR PLANTING, HARVESTING AND STORAGE OF AGRICULTURAL PRODUCTS.             

CONTENT

• Introduction to mechanized farming
• Ploughing
• Planting and Seeding
• Harvesting
• Storage

INTRODUCTION

Good agricultural activities in the nation will enhance the social, economic and political development of the nation and make the nation independent on other nations.

One major problems confronting us in agriculture is the stark reality that our agricultural practice has not changed that much from the labour-intensive and backbreaking practice it used to be.

Through mechanization, new lands and wild lands are being tamed: old lands are better tiller and tended with new forms of farming techniques. Through simple mechanization, a man is able to plant on many hectares of land per day; a task which may requires many men using ordinary cutlasses. Our farms can be larger with fewer farmers producing more to feed the people.

Tractor

Our food processing industries will become viable due to the availability of locally produced raw materials.

Mechanized farming

• Tractor is an agricultural machine acting as power house to drive other agricultural implements hooked to it.
• Ploughing: The process of pulverizing, aerating and loosening the soil to supply good nutrients to new plant seedlings.
• Checkrow planting This an accurate and indexed placement of hills or groups of seeds to give rows in two perpendicular directions
• Picker-Sheller: A machine that cuts picks dehusks and shells corn

Evaluation

1. Define farm mechanism
2. State 4 mechanized farming equipment

Ploughing pulverizes, aerates and loosens the soil, to provide unused plant nutrients for new plant seedlings. Ploughing provides new and unused plant nutrients near the surface of the soil for the new plant seedling.

Ploughing can be done locally by using hoes, animal-driven ploughs. It can be done mechanically tractor-driven ploughs. Ploughing can be done by using animal power or machine power, which typically involves hooking a plough to a tractor. Ploughing is about the hardest work that the farmer has to do.  Ploughing is labour-intensive operation. The energy required to plough depends upon the soil. It varies from the smallest value for the sandy soil to highest value for dry heavy clay soil.

Planting and Seeding

The main objective of planting is to deposit seeds or tuber in the soil at predetermined depth, and make sure the seeds are properly covered. Seed planting follows different patterns include:

1. furrow planting
2. flat planting
3. bed planting
4. Bed planting-two per bed

A simple mechanical planter called auto-feed job planter designed and fabricated at the International Institute for Tropical Agricultural, Ibadan. Apart from planting seed, the system also applies fertilizer. The working components consist of spine, handle, fertilizer/seed funnel, spring, jaw arm, compactor arm and bracket, compactor pad, jaws and depth gauge

Evaluation

1. State 4 planting patterns
2. State the functions of auto-job planter

Harvesting

The method of harvesting depends greatly on the crop.

Corn harvesting involves picking dehusking and shelling. These processes can be done manually or by using machines such as picker-husker or picker-Sheller.

Harvesting of root crops such yam, groundnuts, cassava e.t.c. typically involves digging the soil and scooping it together with the crop, shaking to remove the clinging soil, stones and other debris, and finally retrieving the crop.

Storage

Storage of most crops usually requires pre-drying to certain moisture content.

Factors affecting the storage

The moisture content of a freshly harvested crop is usually high. Freshly harvested corn contains about 20% of moisture, while fresh yam tuber contains more than 65% moisture.

Factors affecting the storage of a crop are: moisture content, temperature and oxygen. For proper storage a crop must be kept dry and cool.

Evaluation

1. state the factors affecting the storage of farm products

AVERAGE MOISTURE CONTENT OF SOME LOCALLY PRODUCED CROPS

System for drying crops

In natural drying, air movement is by free convection. It is susceptible to losses arising from attack by insect and damage by weather. It is not also hygienic whereas in artificial drying, the air is forced over the product by a fan. In a heated air drier, the air is heated to certain temperature and then blown uniformly over the product. The temperature of the air must be kept below some maximum value depending upon the end-use of the product. For example, if the product is to be used for seed, it is usually recommended that a maximum temperature of 43⁰C be used for drying.

There are two basic types of storage system ventilated and non-ventilated systems.

Storage devices

In a refrigerated storage system, the material is stored either in cold storage or frozen storage.

There are two basic types of storage system: ventilated and non-ventilated .Non-ventilated systems are workable in dry climate where the m.c of the product is at, below, safe storage level. In a controlled atmosphere storage oxygen is replaced by inert gases such as nitrogen, carbon dioxide e.t.c.

.

Frozen storage: this is the process of storing a product at a temperature at or below its freezing

Storage devices include the following

1. Gourds for storing maize
2. Silo  for air-tight storage of grains
3. Nitrogen atmosphere tank for storing maize
4. Barns for storing yams
5. Cribs for storing maize

Evaluation

1. State the reasons for using nitrogen atmosphere storing tank

Reading Assignment

Read “DEVICES FOR PLANTING, HARVESTING AND STORAGE OF AGRICULTURAL PRODUCTS.             

Reference Materials:

• EVANS, INTRODUCTORY TECHNOLOGY FOR JSS, BOOK 3, pages 194- 204

Weekend Assignment

1. Good agricultural activities in the nation will enhance the following except (a) the social,(b) economic (c) political (d) sport
2. The following are machine for farming except (a) Tractor (b) Plough (c) Picker-Sheller (d) solar cell
3. _____is an agricultural machine acting as power house to drive other agricultural implements hooked to it (a) Tractor (b) Plough (c) Picker-Sheller (d) Auto-job planter
4. The process of pulverizing, aerating and loosening the soil to supply good nutrients to new plant seedlings is called (a) Tractor (b) Ploughing (c) Picker-Sheller (d) solar cell
5. For proper storage, a crop must be kept (a) dry and cool (b) dry and hot (c) cool and wet (d) cool and frozen

Theory

1. Define mechanized farming and state 4 machines for farming.
2. copy and complete the table below

                                         WEEK 5                        DATE___________________

TOPIC: SANITAION

CONTENT

• Sanitation 
• Non-Network  Disposal System
• Other Non-Network
• Aqua Privy

Introduction

Sanitation can be defined as the equipment and system that keeps places clean, especially by removing human wastes.

The success of any sanitation programme does not depend on the provision of sanitary facilities rather upon collective responsibility through individual discipline for the good of all. Therefore, the importance of good sanitation to the health and general well-being of people cannot be over-emphasized

Poor Sanitation has been linked to the spread of diseases such as cholera, diarrhea, and typhoid e.t.c. Pathogens are disease-producing organisms e.g. mosquito, housefly and tsetse fly.

The design of a sanitary system should have the following factors in focus:

Health factors

1. Fresh excreta should not be handle nor exposed to flies
2. Soil surface and ground water should not be contaminated

Cost factors

1. The construction cost should not be exorbitant
2. Local materials and expertise should be employed for the purpose of construction and maintenance.

The basic objectives of any sanitary system are to reduce the BOD (Biochemical Oxygen Demand) and achieve the reduction and control of pathogens. Biochemical Oxygen Demand is a measure of organic pollution. It is usually expressed milligrams/litres of solution

Non-Network Disposal System

The common latrines, the aqua privy system, the septic tank system are referred to as the non-network systems.

The different types of latrine are the bucket latrine, pit latrine and incineration latrine.

Bucket latrine

The success of the bucket latrine depends critically on organization.

The bucket latrine is an example of what is called a removal method. It involves storing human waste in containers from where night-soil men evacuate them. The bucket consists of four main elements, namely:

1. The defecation area- The latrine and the container to hold the excreta.
2. The removal of excreta to some other container or the replacement of a full container by an empty one
3. Transportation system for moving excreta to some depot.
4. Treatment processes, disposal and/or utilization.

The evacuated waste can be disposal of in any of the following ways:

• Burying underground
• Depositing into water
• Burning
• Composting with refuse
• Sending to digester for biogas production

Problem with bucket latrine is the need for the night-soil men to regularly and carefully remove the buckets to ensure that there is no spillage, which leaves the area very unsightly and full of odour.

Pit latrine

The pit latrine consists of the pit, the floor slab or the squatting plate and the superstructure. It is recommended that the floor slab be constructed with concrete reinforced with steel bars. The pit latrines can be made more popular by providing vents as well as water seals.

In the construction of pit latrine the following factors should be considered at the design stage:

1. Cost
2. Reliability and comfort
3. Fly control
4. Superstructure which must be supported properly so that it is not blown away in any storm.

A pit latrine should be deep as possible to ensure long life. It will dark and thereby prevent breeding of flies and also reduce odour. It is supported particularly in areas where the soil is weak or where the ground water is likely to rise above the bottom of the pit latrine.  In such cases, pit latrines should be lined.1:3:6 concrete mix is recommended for the base. The concrete floor should reinforced and inter locked in between. It should also be vented, as vented latrines have been shown to be odourless and to have less number of flies, due to air circulation.

Aqua Privy

The aqua privy is a device whereby faeces are stored in a water-tight pit, floor slab, and soak away pit. It is not as expensive as the septic tank, while having many advantages over the ordinary pit latrine.

In aqua privy, excreta are deposited directly into a tank rather being flushed along a pipe network as in the case of a septic tank system. For septic tank system, digestion of excreta by anaerobic bacteria takes place in the tank. Faeces enter the tank from the above the squatting plate through a vertical drop pipe, with an optimum  diameter of 15cm, whose tip should be at least 10cm deep in the water.

Advantages over pit latrine

1. The water seal makes aqua privy to eliminate odour
2. The water seal makes aqua privy  to eliminate flies
3. It takes longer period to fill  ( since the bacteria digest the faeces more efficiently in the water medium)
4. It requires a small amount of water for daily maintenance

Advantages over septic tank

1. It is easier to construct
2. it is less expensive
3. It requires less operation

Cautions

The water level in the tank must be maintained by topping it up daily with about 14 litres of water. This quantity of water can be used initially to wash the floor and wall of the inlet drop pipe into the tank every morning.

Other Non-Network

1. Chemical Toilet: A chemical toilet as the name implies consists of a container, which holds a strong solution of bactericidal liquid (liquid capable of killing bacteria) such as sodium hydroxide and formaldehyde. The chemical toilet is ideal for people I boats, buses and trains.

1. Incineration Latrine:  In incineration latrine, excreta are deposited in latrine equipped with an incineration for immediate combustion. The ashes have to be removed. One of the drawbacks of this method is the need to provide fuel energy.

1. The Composting: In this method, excreta, garbage, and paper are put into a container, which is resistant to corrosion. Air is admitted and provision is made for gases to escape. The contents of the container are turned regularly, as they are subjected to biological destruction. Humus is product; water vapour, carbon dioxide and other gases are allowed to escape.

Reading Assignment

Read “SANITATION”

Reference Materials:

• EVANS, INTRODUCTORY TECHNOLOGY FOR JSS, BOOK 3, pages 206-214

Weekend Assignment

1. ­­­­­_________can be defined as the equipment and system that keeps places clean, especially by removing human wastes.(a) Sanitation (b) latrine (c) aqua privy (d) soak away
2. The common examples of latrines include the following except (a) pit (b) bucket (c) incineration (d) sewage
3. Latrines, the aqua privy system, the septic tank system are referred to as the ______ (a) non-network systems. (b) network systems (c) revolutionary system (d) non-revolutionary systems
4. A device whereby faeces are stored in water-tight tank with constant water level is called __ (a) Sanitation (b) latrine (c) aqua privy (d) soak away
5. The objective of any sanitary system are as follows except (a) to reduce the BOD (b) to reduce the activities of pathogens (c) to control micro-organism (d) to increase government revenue

Theory

1. Define sanitation. State 3 types of latrines
2. Draw and explain the operation of Aqua privy toilet.