Quick Revision Notes: Sources of Energy

Class: 10 Science (MP Board)

Energy: The capacity to do work. It exists in various forms and can be transformed from one form to another.
Source of Energy: A source of energy is one which can provide adequate amount of energy in a convenient form over a long period of time.
Characteristics of a Good Source of Energy:
1. High useful work per unit volume or mass (High calorific value).
2. Easily accessible and economical.
3. Easy to store and transport.
4. Safe and clean to use (Minimum pollution).

Energy sources are broadly classified into two categories:

Conventional (Non-Renewable) Sources: Sources that have been in common use for a long time and are present in limited quantities. Once exhausted, they cannot be quickly replaced.
- Examples: Coal, Petroleum, Natural Gas (Fossil Fuels), Nuclear Energy.
Non-Conventional (Renewable) Sources: Sources that are inexhaustible and can be regenerated or used continuously.
- Examples: Solar Energy, Wind Energy, Biomass, Hydro Energy, Tidal Energy, Geothermal Energy.

Formed from the remains of dead plants and animals buried deep inside the Earth millions of years ago under high temperature and pressure.
Examples: Coal, petroleum, and natural gas.
Disadvantages:
- Limited reserves (Non-renewable).
- Burning causes air pollution (oxides of carbon, nitrogen, and sulphur cause acid rain and global warming).

Uses the burning of fossil fuels (coal/gas) to boil water to produce steam.
The steam rotates the turbine of a generator to produce electricity.
Energy transformation: Chemical Energy (Coal) $\rightarrow$ Heat Energy $\rightarrow$ Mechanical Energy (Steam/Turbine) $\rightarrow$ Electrical Energy.

Converts the potential energy of falling water into electricity.
High-rise dams are built on rivers to store water.
Energy transformation: Potential Energy $\rightarrow$ Kinetic Energy $\rightarrow$ Mechanical Energy $\rightarrow$ Electrical Energy.
Advantages: Renewable, clean, no greenhouse gases produced during operation.
Disadvantages: Submerges large ecosystems, displaces human settlements, disrupts river flora and fauna.

Biomass: The dead matter from plants and animals (wood, cow dung, crop residue).
Charcoal: When wood is burned in a limited supply of oxygen, water and volatile materials are removed, leaving charcoal behind. It burns without flames, has a higher heat generation efficiency.
Biogas Plant (Gobar Gas Plant):
- An anaerobic degradation (in the absence of oxygen) of animal dung and plant wastes mixed with water (slurry) by micro-organisms.
- Main constituent of Biogas: Methane (CH4) - about 75%.
- Advantages: Excellent fuel, leaves no residue, provides enriched manure (nitrogen and phosphorus).

Uneven heating of the Earth's surface by the sun generates wind.
Kinetic energy of the moving wind is harnessed by wind turbines to turn a generator and produce electricity.
Minimum wind speed required: Generally around 15 km/h for practical use.
Advantages: Pollution-free, renewable.
Disadvantages: High initial setup cost, requires large tracts of land, dependent on wind availability.

Energy harnessed from the sun.
Solar Cooker: Uses black painted surfaces to absorb maximum heat (box-type or reflector-type).
Solar Cell (Photovoltaic Cell):
- Device that converts solar energy directly into electrical energy.
- Made of semiconductor materials like Silicon.
- A typical solar cell produces about $0.5\text{ V}$ to $1\text{ V}$ of electricity and about $0.7\text{ W}$ of power.
- Solar Panel: A combination of many solar cells connected in series/parallel to get a large amount of electricity.

Tidal Energy: Harnesses the rise and fall of water due to gravitational pull of the moon. Dams are built across narrow openings of the sea to trap tidal water.
Wave Energy: Kinetic energy from giant waves near the coast is trapped to turn turbines.
Ocean Thermal Energy Conversion (OTEC):
- The temperature difference between warm surface water (sun-heated) and cold deep ocean water (at depths of 2 km) is used to operate power plants.
- A temperature difference of $20^\circ\text{C}$ or more between surface water and deep water is required.

Heat energy from deep inside the Earth.
Underground water comes in contact with hot spots (molten rocks pushed up in geological regions) and changes into steam. This steam is routed to turn a turbine and generate electricity.

Energy released during nuclear reactions (fission or fusion).
Nuclear Fission: The process in which the heavy nucleus of a radioactive atom (like Uranium-235, Plutonium, or Thorium) is bombarded with low-energy neutrons, splitting it into lighter nuclei with the release of a tremendous amount of energy.
Einstein’s Equation: $E = mc^2$ (Mass is converted into energy).
Nuclear Hazards: Improper waste disposal can cause severe radiation leakage; risk of accidental nuclear explosions.

Global Warming: Burning of fossil fuels releases greenhouse gases like Carbon Dioxide ($CO_2$), trapping heat in the atmosphere and raising Earth's average temperature.
Acid Rain: Sulphur dioxide ($SO_2$) and Nitrogen oxides ($NO_x$) released from burning fossil fuels mix with rain water, making it acidic.
Renewable vs Non-Renewable balance: Shifting toward renewable energy (solar, wind, hydro) is crucial for sustainable development.

Sources of Energy