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Renewable energy, often referred to as clean energy, comes from natural sources or

processes that are constantly replenished. For example, sunlight or wind keep shining
and blowing, even if their availability depends on time and weather.

Nonrenewable sources of energy are only available in limited amounts and take a long

time to replenish. When we pump gas at the station, we’re using a finite resource

refined from crude oil that’s been around since prehistoric times. Example- Fossil fuels

Fossil Fuels and Thermal Energy

Conventional sources of energy

 Sources of energy that have been in use for a very long time or have been used

extensively worldwide are known as conventional sources. Eg: wood as a
common source of heat energy or the usage of coal after the Industrial

Revolution.

 Examples: Fossil Fuels, Hydro Power

Fossil fuels

 Fossil fuels are formed due to compression of dead organic matter over millions

of years, buried deep under the earth. E.g. coal or natural gas.

 We rely heavily on fossil fuels for most of our work.

 Fossil Fuels are non-renewable sources of energy as they have limited reserves

and hence finding alternative sources is essential to avoid an energy crisis.

Disadvantages of burning fossil fuels

 Fossil fuels also produce byproducts due to combustion which causes air

pollution.