Conventional and non-conventional energy sources, renewable energy, nuclear energy
• High calorific value (more energy per unit mass)
• Easy to store and transport
• Burns with reasonable rate, no residue
• Eco-friendly (minimum pollution)
• Affordable and readily available
Fossil fuels are formed from decomposed remains of organisms buried millions of years ago under heat and pressure.
Coal: Burns to produce CO₂, SO₂, SO₃ → acid rain
Petroleum: Refined to produce petrol, diesel, kerosene, LPG
Natural gas (CNG): Mostly methane; burns cleanly; used in cooking, vehicles
Problems: Non-renewable (will exhaust); cause greenhouse effect and global warming; acid rain; air pollution
Coal burned → heat → steam → turbine rotates → generator → electricity
Efficiency ≈ 35% (65% heat wasted!)
Thermal plants built near coal mines to reduce transport cost
Dams built on rivers → water stored at height → released → falls → turbine → generator → electricity
Gravitational potential energy → kinetic energy → electrical energy
Renewable and non-polluting! But: displaces people, submerges forests, disrupts ecology
| Source | Working | Advantages | Disadvantages |
|---|---|---|---|
| Solar Energy | Solar cell (photovoltaic) converts sunlight → electricity; Solar heater stores heat | Inexhaustible, clean, no moving parts | Expensive, intermittent (night/cloudy), large area needed |
| Wind Energy | Wind → windmill rotates → generator | Clean, free, renewable | Requires wind speed >15 km/h, large land, noise, kills birds |
| Biomass/Biogas | Organic waste decomposed by bacteria → biogas (CH₄ + CO₂); burns cleanly | Uses waste, slurry = fertiliser, clean fuel | Large amounts of organic matter needed |
| Tidal Energy | Rise and fall of tides → turbine | Predictable, renewable | Limited to coastal areas, few suitable sites |
| Wave Energy | Ocean waves move pistons/turbines | Renewable, no fuel | Difficult to harness consistently |
| Geothermal | Earth's heat from molten rock → steam → turbine | Clean, nearly unlimited | Limited to geologically active areas |
Nuclear Fission: Heavy nucleus (U-235, Pu-239) splits into lighter nuclei when hit by neutron → releases huge energy + more neutrons → chain reaction
Used in nuclear power plants and atom bombs
E = mc² (Einstein's equation — mass converts to energy)
Nuclear Fusion: Two light nuclei (H) fuse to form heavier nucleus (He) → releases even more energy than fission
Occurs in stars (including our sun); powers hydrogen bombs
Fusion is cleaner but requires extremely high temperatures (10⁷ K) — not yet harnessed commercially
Advantages: Extremely high energy per unit mass; low fuel needed; no greenhouse gas emissions during operation
Disadvantages: Radioactive waste (extremely hazardous, lasts thousands of years); risk of accidents (Chernobyl, Fukushima); high construction cost; terrorism risk