Some events of the Sinhala-Hindu New Year festival and a procession are given in the following pictures.

Now, think about these activities. It is clear, that some work is done in all these activities. Now, let's focus on some activities done in our day-to-day life. Pulling a log using a rope, carrying a heavy load of soil by a wheel barrow, loading of goods to a vehicle are some common examples. We understand that energy is needed to do all these activities. What is energy ? Energy is defined as the ability to do work.

Use of energy to do work

Let’s do Activity 4.1 to understand how energy can be utilized to do work.

The wind propeller rotates when there is wind. When the wind speed is higher, the propeller rotates faster.

The rotation of the wind propeller indicates a task. How did the wind propeller get the energy ? It was provided by the blowing wind.

The beaker inside the cooker absorbs more solar energy than the beaker kept outside due to the special arrangement of the cooker. Therefore, the temperature of the beaker inside the box is higher than the beaker kept outside the box. This happens due to solar energy.

When you cook using a solar thermal stove / cooker, solar energy is used. Solar enenrgy is used in many day-to-day activities. For example, drying of chillies / clothes, grains and for making “Lunu dehi”.

Activity 4.1 demonstrates the use of wind energy to rotate a wind propeller. Activity 4.2 shows the use of solar energy to heat water and cook food. There are a large number of enenrgy sources.

e.g : Sun, biomass, fossil fuel, wind, running water, sea waves, tidal

waves, geothermal and nuclear power

Table 4.1 summarises the examples of different activities that use

energy and the respective energy source.

Table 4.1- Examples of use of energy and respective energy source.

Now, let’s study about other sources of energy.

Sun

Fig. 4.7 shows a solar water heater which is located on the roofs of some houses. This can be used to heat water. Solar panels are used in some occasions where electrcity cannot be obtained from the main electricity supply to power some electric appliances. Solar panels obtain their energy from sunlight. Even satellites obtain power from solar panels containing many solar cells.

Biomass

Living materials can produce energy. Think of a wild fire which occurs commonly during drought seasons. Controlling of such fire is very difficult because dried leaves catch fire easily. Such fires release large amount of heat. This proves that living parts can be used to produce energy. Such plant or animal materials which can be used as a fuel, are known as “biomass”. Firewood is one of the commonly used biomass. Other examples of biomass are coconut shells, coal, rotten vegetables, hay, saw dust, rice bran, rotten food materials and agricultural waste. Biomass also contains solar energy. Saw dust stove or "kudu lipa" / "thool aduppu" is one example, where biomass is used. Here, rice bran or saw dust is used as biomass. Make a saw dust stove with the help of your teacher .

This is a very simple economical hearth which can be used to cook meals and to boil water.

Fossil Fuel

Do you know how did the old train engines get energy? It was produced by burning coal. The heat emitted during the burning of coal was used to convert water to steam. The energy generated by steam was used to operate engines. Coal, petroleum oil and petroleum gases are considered as fossil fuel. These fossil fuels are accumulated under different parts of the inner earth. These fuels are made from the buried plants and animals. They are produced when this buried matter is subjected to high pressure and temperature. This process takes millions of years. Solar energy is the stored energy in the fossil fuel too.

Wind

Have you seen how farmers separate unfilled or half filled rice grains from the harvest ? Wind power is used for this purpose even today in rural areas. Wind power can also, be used to dry different materials. Let’s do the following activity to see whether we can use wind energy to do work.

You will observe the rotation of the wind propeller and the lifting of the weight,when wind blows. Thus, it is obvious that we can do work with the help of wind. Large wind mills are operated using wind energy. In ancient times, people used this energy to grind grains and to pump water. When the wind mill operates, we can rotate the parts of a generator. This can be used to generate electricity, too. These types of energy power plants are available in Sri Lanka as well. (Hambanthota, Puththalam)

Energy Stored in Water

During ancient times, people used running water to do certain work such as to grind grains and to operate saw mills. They used water to rotate a turbine and thereby generate energy. Let's do Activity 4.5 to make a turbine.

Energy stored in running water is utilized in hydropower stations to generate electricity. When water is at a higher position, it contains more energy. It is called potential energy. Normally power stations are located at a lower position. The running water is carried in pipes at a high speed. This water is used to rotate the fans of the turbine and operate the generators.

Sea Waves

Sea waves are strong. They can generate a large quantity of energy. This will be a very valuable source of energy in the near future. This energy can be converted into electrical energy by building floating power plants in the sea. A flow of air is used to rotate the blades of the turbine. In some instances, the stored energy of the sea waves causes destructions. One good example is the occurrence of Tsunami in 2004. Due to this situation, we lost millions worth properties and invaluable lives of humans. It also caused great harm to nature.

Tidal Waves

Geothermal Energy

Nuclear Energy

Have you ever thought how does the sun generates its energy? The energy of the sun is generated due to nuclear reactions. A very high amount of energy is emitted during these reactions. If nuclear reactions are performed under controlled conditions, nuclear energy can be generated. This energy is emitted as heat or thermal energy. Heat is thus generated used to produce steam. Steam produced by this process is then used to rotate turbines and to produce electricity. Some countries use this technique to produce electricity.

Sustainable Use of Energy Sources

Now you are aware that energy is needed to do work. Energy helps us in many ways. It helps us to maintain our body temperature, provides light, and helps to cook your meals. It is also used to operate television and radio. Not only that, energy supplies power to move vehicles and for body functions and movements.

In ancient times (200 years ago), the major energy sources were the sun, fire-wood and wind. People used solar energy to dry things, and fire wood to cook meals. Wind energy was utilized for sailing boats.

With the increasing complexity in lifestyle, new energy sources were discovered. Many of them are now used to generate electricity.

The world population increases day-by-day. Energy requirements also, increase accordingly. The use of some energy sources are increasing at a high rate. For example, fossil fuel is a non renewable energy source.What will happen when all sources of coal, petroleum gases and petroleum oil are over? It will take millions of years for them to regenerate. Therefore, it is our responsibility to use these energy sources wisely, without wasting.

We have to protect them for our future generations.

We can conserve energy sources by using them carefully. Our ancestors used them carefully and protected them for us.Therefore, it is our responsibility to protect these sources for future generations, too.

We have to concern about taking necessary action to avoid this crisis in future.

Exercise

01.

i. What is biomass?

ii. What is the similarity between bio mass and fossil fuel?

02.

i. What are the energy sources suitable to generate electricity in Sri Lanka?

ii. What are the fossil fuels that are used in power stations in Sri Lanka?

03

i. Suggest some measures to minimize the energy consumption in your home?

ii. What are the energy sources that will be used to a large extent in the future?