Sources of Energy Blog 2

SOURCES OF ENERGY 

 LESSON 2

Welcome students!

Learning outcomes : 
At the end of the topic, learners will be able to

1. analyse the structure , function and uses of a biogas plant.
2. appreciate the technology of drawing best out of waste
3. interpret the advantages and disadvantages of using wind energy , solar energy as sources of energy.

Instructions:

Topic marked in red need to be copied in Physics note book.

Biomass

• Biomass is the source of energy derived from living things (organic matter).  biowaste such as cow dung 
• When wood is burnt in a limited supply of oxygen and water until volatile materials are removed, the residue left behind is charcoal. 
• Charcoal has good heat generating efficiency. It also burns without flames.

Bio-gas plant

• Cow dung, sewage waste, plant matter are decomposed in absence of oxygen to produce biogas. 
• A biogas plant is a dome-like structure built with bricks where cow dung and other biowaste are mixed with water to form a slurry and put into a digester.
• The digester is a sealed chamber with anaerobic bacteria which breaks down the slurry.
• This decomposition process releases gases like methane, $C{O}_2$, hydrogen sulfide and hydrogen.
• These gases are drawn via pipes which are transmitted to a turbine for the production of electricity.

Wind energy

• Environment-friendly efficient source of energy.
• Wind is the natural phenomenon caused by pressure differentials due to unequal heating of land and water masses on the surface of the earth. It is harnessed in the form of kinetic energy.

Windmill

• Wind Energy is harnessed by rotatory structures known as windmills.
• They have huge blades or fans attached very high on a rigid support that is attached to turbines that rotate due to high speeds of wind and generate electricity.
• A single windmill has a low output and therefore, the wind farms are built that comprises of several windmills.

Advantages of wind energy

Environment-friendly, efficient, renewable source, with no recurring cost for production of electricity.

Limitations of wind energy

• Wind speeds should be constant and > 15 km/h.
• Must have back up storage facilities like cells.
• Requires large land area. ​
• ​​​​​​High initial cost and regular maintenance are required.

ALTERNATIVE SOURCES OF ENERGY

ADVANTAGES 

    •  Eco friendly

    •  Renewable

    •  Used in rural areas

 DISADVANTAGES 

    •  Silicon cells are expensive

    •  Solar radiation are not uniform over earth’s surface

    •  Can’t be used at night or on cloudy day.

    •  Max temperature achieved by solar cooker is 100° C

Solar cooker

• Solar cookers and water heaters use solar energy to operate.
• Black surfaces absorb more energy than other surfaces and solar cookers use this property by coating their insides black.
• They use reflecting surfaces like mirrors to focus the sun’s rays.
• The device is covered with a glass plate thereby establishing the greenhouse effect by trapping heat inside the cooker.

Solar cell

• A device that converts solar energy into electricity is known as a solar cell.
• A typical solar cell produces a voltage of 0.5 1 V and 0.7 W of electrical power. 
• A large number of such cells can combine to form a solar panel which can generate power large enough for practical uses.

Advantages of Solar cell

(i) no moving parts 

(ii) require little maintenance 

(iii) can be set up in remote areas without the hassle and expenses of transmission lines.

Disadvantages of Solar cell

(i) Requires a special grade silicon which is not easily available 

(ii) Usage of silver for interconnections makes it expensive.

• Uses of Solar cell
  : traffic signals, calculators, artificial satellites and space probes.

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