Energy and Society – SS3 Physics Lesson Note (First Term)

Energy in society means the energy resources, such as fuel, petroleum products and electricity, that people use to do work.

Behavioural objectives

1. List the main sources of energy available to society.
2. Distinguish between renewable and non-renewable energy resources and give examples of each.
3. State the main uses of energy in society.
4. Describe how hydroelectric power is generated.
5. Explain the terms head, penstock and powerhouse.

What are the sources of energy?

There are nine main sources of energy available to society: petroleum and natural gas, nuclear energy, solar energy, wind energy, hydroelectric energy, geothermal energy, coal and wood, tidal and ocean energy, and biomass.

1. Petroleum and natural gas: fossil fuels used for transport, cooking and electricity generation.
2. Nuclear energy: energy released from radioactive material in a nuclear reactor.
3. Solar energy: energy from the Sun, used for heating and for solar panels.
4. Wind energy: moving air turns the blades of a wind turbine.
5. Hydroelectric energy: falling or fast-flowing water drives turbines.
6. Geothermal energy: heat from inside the Earth.
7. Coal and wood: solid fuels burnt for heat.
8. Tidal and ocean energy: energy from the rise and fall of tides and from ocean waves.
9. Biomass: plant and animal matter, such as farm waste, used as fuel.

What are renewable and non-renewable energy resources?

Energy resources are grouped as renewable or non-renewable, depending on whether they can be replaced after use.

What are renewable energy resources?

Renewable energy resources are energy resources that can be replaced continually as they are used up.

• Solar energy: the Sun keeps supplying heat and light.
• Wind energy: wind keeps blowing and can be used again and again.
• Biomass: plants and waste can be regrown or produced again.
• Biofuel: fuel made from plant or animal matter, such as ethanol from crops.
• Tidal power: tides rise and fall every day.
• Water or hydroelectric power: rain keeps refilling rivers and reservoirs.
• Geothermal energy: heat from inside the Earth is continually available.

What are non-renewable energy resources?

Non-renewable energy resources are energy resources that cannot be replaced or replenished as they are used up.

• Nuclear energy: comes from radioactive material, which is limited in supply.
• Petroleum and natural gas: take a very long time to form underground.
• Coal: a fossil fuel that takes a very long time to form.
• Wood: listed as non-renewable when trees are cut faster than they are replanted.

Petroleum, natural gas and coal are classified as fossil fuels.

What is the difference between renewable and non-renewable energy resources?

What are the uses of energy?

Energy is used to control and adapt to the environment, and it is essential to the development of society.

1. Agriculture: pumping water for irrigation and running farm machines.
2. Transportation: fuel moves cars, buses, trains, ships and aircraft.
3. Waste collection and recycling: powers refuse trucks and recycling machines.
4. Information technology: electricity runs computers, servers and phones.
5. Communication: radio, television and telephone networks need electricity.
6. Homes and industry: electricity supplies homes and runs industrial machinery.
7. Heating or cooling of homes: energy runs heaters, fans and air conditioners.

How is hydroelectric power generated?

What is hydroelectric power?

Hydroelectric power, also called hydropower, is electricity produced from generators driven by turbines that convert the potential energy of falling or fast-flowing water into mechanical energy.

• In the early 21st century, hydroelectric power was the most widely used form of renewable energy.
• In 2019 it accounted for more than 18 per cent of the world’s total power generation capacity.
• Nigerian examples include the Kainji, Jebba and Shiroro stations.

What are the steps in generating hydroelectric power?

1. Water is collected and stored at a higher elevation, behind a dam, in a reservoir.
2. The water is led downward through large pipes or tunnels (penstocks) to a lower elevation.
3. At the end of the penstock, the falling water makes the turbines rotate.
4. The turbines drive generators, which convert the turbines’ mechanical energy into electricity.
5. Transformers convert the alternating voltage suitable for the generators to a higher voltage suitable for long-distance transmission.
6. Transmission lines carry the electricity to homes, offices and industries.

What is the energy change in a hydroelectric station?

• Stored water: has potential energy because it is high up.
• Falling water: potential energy changes to kinetic energy.
• Turbine: kinetic energy of water becomes mechanical energy of rotation.
• Generator: mechanical energy becomes electrical energy.

What are head, penstock and powerhouse?

• Head: the difference in elevation between the stored water and the water at the turbines.
• Penstock: a large pipe or tunnel that carries water from the reservoir down to the turbines.
• Powerhouse: the structure that houses the turbines and generators, and into which the penstocks feed.
• Transformer: a device that raises the generator voltage for long-distance transmission.

Where are hydroelectric power plants located?

Hydroelectric power plants are usually located at dams that impound rivers.

• Dam height: the dam raises the water level behind it and creates as high a head as is feasible.
• Head and power: the potential power from a volume of water is directly proportional to the working head.
• High head: a high-head installation needs a smaller volume of water than a low-head one to produce the same power.
• Powerhouse on a flank: in some dams the powerhouse is built on one side, and part of the dam is a spillway for excess water in times of flood.
• Powerhouse in the dam: where the river flows in a narrow, steep gorge, the powerhouse may be inside the dam itself.

What are the advantages and disadvantages of hydroelectric power?

Evaluation

1. Name five sources of energy.
2. Distinguish between renewable and non-renewable energy resources, giving two examples of each.
3. State four uses of energy in society.
4. What is meant by the head in hydroelectric power generation?
5. State the function of transformers in a hydroelectric power plant.

Assignment

Describe how hydroelectric power is generated. In your answer, mention the penstock, turbine, generator, transformer and powerhouse.