Sources of Useful Energy and Electrical Power

This section describes how useful energy or electrical power is generated from various natural and man-made sources. Where applicable, it explains the roles of boilers, turbines, and generators.

(a) Chemical Energy Stored in Fossil Fuels

Fossil fuels such as coal, oil, and natural gas contain chemical energy stored over millions of years from dead plants and animals.

• Fossil fuels are burned in a boiler to heat water and produce steam.
• The high-pressure steam spins a turbine.
• The turbine is connected to a generator, which converts the rotational kinetic energy into electrical energy using electromagnetic induction.

This is the most common method used in thermal power stations.

(b) Chemical Energy Stored in Biofuels

Biofuels are made from recently living biological material, such as crops, animal waste, or algae. They are renewable and can be replenished over short timescales.

• Biofuels (like biogas or ethanol) are combusted in a boiler to produce steam.
• The steam drives a turbine, which turns a generator to produce electricity.

Biofuels can also be used directly in internal combustion engines for transport and backup power generation.

(c) Water: Waves, Tides, and Hydroelectric Dams

Water is a powerful source of renewable energy in several forms:

• Waves: The motion of sea waves drives pistons or floating devices that move magnets through coils, generating electricity directly.
• Tides: As tides rise and fall, water flows through sluice gates and spins underwater turbines connected to generators.
• Hydroelectric Dams: Water stored at a height in a reservoir (gravitational potential energy) is released to flow down through large turbines.

In hydroelectric plants:

• Water does not need to be boiled – it already has kinetic energy due to gravity.
• The falling water spins a turbine which turns a generator.

(d) Geothermal Resources

Geothermal energy uses heat from the Earth’s interior to generate electricity or directly heat buildings.

• Cold water is pumped deep into the Earth where it is heated by hot rocks.
• The hot water or steam returns to the surface.
• In power generation:
  
  • The steam drives a turbine which turns a generator.
• No boiler is needed — the Earth’s heat is the natural boiler.

Geothermal plants are most effective in volcanic or tectonically active areas.

(e) Nuclear Fuel

Nuclear power stations use the energy released from nuclear fission reactions in radioactive fuels (like uranium-235 or plutonium-239).

• The nuclear fuel undergoes fission, releasing large amounts of thermal energy.
• This thermal energy is used to heat water in a boiler to produce steam.
• The steam drives a turbine, which is connected to a generator.

Nuclear fuel provides a high energy output and no carbon emissions during operation, but it produces radioactive waste that must be safely stored.

(f) Light from the Sun to Generate Electricity -Solar Cells

Solar cells (photovoltaic cells) convert light energy directly into electrical energy using semiconductors such as silicon.

• When sunlight hits the solar cell, it excites electrons in the material, causing current to flow.
• No boiler, turbine, or generator is needed.
• Solar cells are used in calculators, rooftops, solar farms, and satellites.

They work best in direct sunlight and are silent and non-polluting during operation.

(g) Infrared and Other Electromagnetic Waves from the Sun – Solar Panels and Wind

Infrared and visible light from the Sun heat surfaces like water or land. This energy can be captured or transformed into other useful forms:

• Solar panels (thermal): These panels heat water using sunlight — the hot water is stored or circulated through buildings for domestic use.
• Wind energy: The Sun heats the Earth’s surface unevenly, causing air to move (wind). This kinetic energy is harnessed by wind turbines.

In wind turbines:

• Moving air turns the blades of a turbine.
• The turbine is connected to a generator to produce electricity.

Neither wind nor solar thermal systems require a traditional boiler.