1. Introduction

• ★Conservation of Energy:

  Energy is a fundamental physical quantity that cannot be created or destroyed. It can only be transformed from one form to another, such as from potential energy to kinetic energy, or from chemical energy to heat and light. This principle is known as the law of conservation of energy.

• ★Energy Crisis:

  Although energy is conserved, not all energy is usable for work. Much of it dissipates as heat, sound, or other forms that are difficult to harness efficiently. This is why energy resources are often considered "consumed" in practical terms, leading to energy shortages and crises worldwide.

2. Characteristics of a Good Source of Energy

• ★A good energy source should provide a large amount of work per unit mass or volume, ensuring efficiency.
• ★It should be easily accessible and available in sufficient quantity.
• ★Storage and transport should be convenient and safe.
• ★The source should be economical, providing energy at a reasonable cost.

3. Conventional Sources of Energy

A. Fossil Fuels

• ★Examples: Coal, petroleum, and natural gas.
• ★Formation: These fuels are formed from the remains of ancient plants and animals over millions of years. They are non-renewable because their reserves are finite.
• ★Usage: Fossil fuels are a major source of energy for electricity generation, heating, and transportation.
• ★Disadvantages: Burning fossil fuels releases pollutants such as carbon dioxide, sulfur oxides, and nitrogen oxides, contributing to air pollution, acid rain, and global warming.

B. Thermal Power Plants

• ★Fossil fuels are burnt to heat water, producing high-pressure steam that drives turbines connected to electricity generators.
• ★Thermal power plants are usually located near coal or oil fields to reduce fuel transport costs.
• ★The term "thermal" emphasizes the conversion of heat energy from burning fuel into electrical energy.

C. Hydro Power Plants

• ★Hydroelectric power harnesses the potential energy of water stored at a height behind dams. As water flows downward, its energy is converted into kinetic energy, which turns turbines connected to generators.
• ★Advantages: Renewable and clean source; water is naturally replenished by rainfall.
• ★Limitations: Suitable only in hilly terrains, requires large dams, displaces local communities, submerges farmland, and can release methane from submerged vegetation.

D. Bio-Mass

• ★Bio-mass includes fuels derived from plants and animal waste, such as wood and cow dung.
• ★Technological improvements: Charcoal is produced by heating wood in limited oxygen, yielding a smokeless fuel with higher heat efficiency. Biogas is generated by anaerobic digestion of cow dung, vegetable waste, and sewage.
• ★Biogas plants contain a sealed digester where microbes decompose organic matter to produce methane, carbon dioxide, hydrogen, and hydrogen sulfide. Methane-rich gas burns cleanly, and the remaining slurry can be used as fertilizer.

E. Wind Energy

• ★Unequal heating of land and water creates wind, which possesses kinetic energy.
• ★Wind turbines convert the kinetic energy of moving air into mechanical energy, which is then transformed into electricity.
• ★Wind farms use multiple turbines over large areas to produce electricity commercially.
• ★Advantages: Renewable, environment-friendly, no fuel cost. Limitations: Requires consistent wind speed, large land area, and has high installation and maintenance costs.

4. Alternative / Non-Conventional Sources of Energy

A. Solar Energy

• ★Solar constant: The energy received per unit area at the outer edge of Earth’s atmosphere is 1.4 kW/m².
• ★Devices: Solar cookers and heaters use black surfaces to absorb heat, often with mirrors to focus sunlight. Solar cells convert sunlight directly into electricity; combining multiple cells forms a solar panel.
• ★Advantages: Renewable, low maintenance, suitable for remote areas. Limitations: High initial cost due to materials like silicon and silver, low efficiency.

B. Energy from the Sea

• ★Tidal energy harnesses the rise and fall of sea levels using dams at narrow sea openings.
• ★Wave energy uses the kinetic energy of ocean waves to drive turbines.
• ★Ocean Thermal Energy Conversion (OTEC) exploits temperature differences between warm surface water and cold deep water. Warm water vaporizes a working fluid, which drives turbines, and cold water condenses it back.

C. Geothermal Energy

• ★Heat from molten rocks underground warms water, producing steam that drives turbines to generate electricity.
• ★Advantages: Low production cost. Limitations: Only few suitable sites exist, e.g., New Zealand, USA.

D. Nuclear Energy

• ★Nuclear Fission: Heavy nuclei like Uranium or Plutonium are split by neutrons, releasing tremendous energy. One atom of Uranium releases millions of times more energy than one atom of carbon.
• ★Nuclear Fusion: Light nuclei, such as Hydrogen, fuse to form Helium, releasing energy according to Einstein’s equation, E = Δmc². This is the energy source of the Sun and stars.
• ★Advantages: Massive energy from a small fuel amount. Limitations: Radioactive waste, risk of accidents, and high cost of reactors.

5. Environmental Consequences & Shelf Life

• ★No energy source is completely free from environmental impact. Fossil fuels pollute air; solar panels and wind turbines have environmental costs during manufacturing.
• ★Non-Renewable Sources (Exhaustible): Will be depleted eventually, e.g., coal, petroleum.
• ★Renewable Sources (Inexhaustible): Can be regenerated naturally or are repetitive, e.g., biomass, solar, wind, hydro power.

6. Exam Tips & Summary