CBSE Class 10 Science: Sources of Energy — Complete Notes 2026

Conventional Energy Sources

• Fossil fuels (coal, petroleum, natural gas): formed from ancient organisms over millions of years; non-renewable
• Coal: major electricity source in India; burning releases CO₂, SO₂; causes acid rain and global warming
• Petroleum: refined into petrol, diesel, kerosene, LPG; OPEC controls 40% of world oil supply

Thermal Power Plants

• Burn coal/oil to heat water → steam → turbine → generator → electricity
• Efficiency: 35–40%; rest lost as heat; major source of air pollution
• India: 60% of electricity from thermal power; Korba, Singrauli major thermal plants

Hydroelectric Power

• Dams: store water; potential energy → kinetic energy → electrical energy; no pollution during operation
• Bhakra Nangal, Tehri, Sardar Sarovar: major Indian hydro projects; 12% of India's power
• Issues: displacement of communities, silt accumulation, earthquake risk, destruction of riverine ecosystems

Solar Energy

• Photovoltaic cells: silicon semiconductor converts sunlight directly to electricity; used in calculators, home panels
• Solar thermal: concentrate sunlight to heat water or generate steam; parabolic reflectors, solar cookers
• India: PM-KUSUM scheme; target 500 GW renewable by 2030; Rajasthan ideal for solar (300+ sunny days)

Wind Energy

• Wind turbines: kinetic energy of wind → mechanical energy → electrical energy
• Wind farms: Muppandal (Tamil Nadu), Jaisalmer (Rajasthan), Gujarat coastline; need consistent wind > 15 km/h
• Limitations: intermittent (not available all time), noise, bird mortality, high initial cost

Biomass and Biogas

• Biomass: plant/animal waste burned for energy or converted to biogas/ethanol
• Biogas: cow dung + water → anaerobic fermentation → CH₄ (65%), CO₂, H₂S; burns cleanly
• Benefits of biogas: slurry is excellent manure; reduces firewood use; prevents deforestation in rural India

Nuclear Energy

• Fission: heavy nucleus (U-235) splits into smaller nuclei releasing enormous energy; 1 kg U-235 ≈ 3,000 tonnes coal
• Tarapur, Kaiga, Narora: nuclear plants in India; provide ~3% of India's electricity
• Risks: radioactive waste disposal, accidents (Chernobyl 1986, Fukushima 2011); high setup cost