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Sources of Energy and the Ultimate Energy Source

Sources of energy and the ultimate energy source

Energy sources are the energy resources available to humans and can be used to do work and produce heat.

The sources used today for electricity production come basically from fossil fuels (coal or hydrocarbons), hydropower, nuclear energy, wind power, geothermal, and solar energy.

The primary purpose is to produce electrical energy, but these resources are also often used to obtain mechanical work (cars) or heat (heating).

Which Is the Ultimate Source of Energy?

Most of the world's energy resources have the Sun as their primary source.

Sources of energy and the ultimate energy source

Solar energy is conserved indirectly in fossil energy or as directly usable energy (for example, the winds).

Even hydropower derives from solar energy that causes water to evaporate and consequent condensation when clouds meet air from cold weather fronts or high mountains.

How Are Energy Sources Classified?

Energy sources can be classified mainly in two ways:

  • Primary or secondary sources.

  • Conventional and non-conventional sources of energy.

Primary energy sources are present in nature. They include oil, coal, natural gas, firewood or biomass, nuclear fuels, hydropower, wind power, geothermal and solar energy, ordered by its importance of current exploitation.

On the other hand, secondary energy sources are not directly present in nature and are resources derived from primary sources. Secondary sources include, for example, electricity.

Conventional sources are not unlimited. They are also known as non-renewable sources such as coal, gas, and oil. On the contrary, non-conventional sources are endless and known as renewable sources such as solar energy or wind power.

Conventional Sources of Energy: Non-renewable Sources

Non- renewable energy sources are energy resources that cannot regenerate or that the consumption rate is higher than that of their regeneration.

The availability of these sources is currently still quite high and, consequently, the cost relatively low.

The primary non-renewable resources are the following:

Fossil Fuels

Regarding the source of fossil fuels, coal combustion or hydrocarbons such as methane or oil provides the maximum amount of energy. The energy gained is used in part for combustion heating systems and the operation of engines, but especially for the production of electrical power.

The advantages of fossil fuels are:

  • High energy density.

  • Easy transportation.

  • Wide availability (at least until now).

  • Oil is also used for non-energy purposes (transport, heating, and electricity generation).

The cons it has are:

  • Every year the world consumes many fossil fuels that nature has created over millions of years. Therefore, after some years, energy supplies can not be taken for granted.

  • The production of CO2 and other pollutants, such as sulfur oxides (mainly SO 2 ) and nitrogen oxides (NO X ).

  • The geographic location of fossil fuels: around 65% of the world's oil resources are located in the Middle East, and within 30 years, Europe's natural gas deposits will be exhausted. As for North America, the natural gas situation is even more critical. Add to this that many countries want to become less dependent on foreign countries for their energy demand.

Nuclear Energy

Nuclear energy can be seen as the mother of all energies on Earth and even the universe. All energies, from solar to fossil energies, from wind power to hydropower, are nothing more than a by-product of the transformation of this type of energy.

There are two types of nuclear reactions: fission and fusion. Today, all nuclear reactors are fission-type for technical reasons. 

Atomic fission energy breaks up a heavy atomic nucleus (usually Uranium-235) to obtain two smaller nuclei, which weigh less than the original nucleus. The slight difference in mass can produce a large amount of energy.

The pros of nuclear energy:

  • Fission reactions do not produce carbon dioxide (CO 2 ).

  • Nuclear fuel has high energy efficiency.

  • More minor logistical issues for the transport fuel than a conventional thermal power plant.

  • The volumes of waste production are significantly lower than a fossil power plant, such as ashes, nitrogen oxides, carbon dioxide, and sulfur oxides.

Cons of nuclear power:

  • The products of the fission reaction are highly radioactive.

  • Nuclear waste must be treated in a particular manner and stored in deep geological sites.

  • The dangerousness of the waste, thus profoundly influencing the transport, treatment, and placement activities.

  • Uranium reserves are more petite than coal and oil reserves.

In a future perspective, a nuclear fusion reactor would exploit an unlimited source of energy. Fusion energy's fuel is deuterium which is available in water, and lithium.

Nuclear fission plants currently produce 16% of the world's electricity.

Non- Conventional Sources of Energy: Renewable Energy Sources

Renewable energy sources are those types of inexhaustible energy. Its use does not imply a decrease in resources.

The primary renewable energy sources are the following:

Firewood and Biomass

The combustion of biomass, wood, or other readily available organic materials represents the oldest way of producing heat and energy.

Lately, however, a renewed awareness in the fight against climate change, combined with growing concern to find energy resources, has brought this energy source back into the news.

Solar Energy

Solar energy is the engine of any activity on Earth: even oil is indirectly solar energy accumulated by the photosynthesis of ancient plants, whose organic matter is believed to have gathered and transformed underground during entire geological ages.

Solar energy can be harnessed through three methods:

Wind Power

Wind power is one of the oldest energy sources: windmills have been used since the 7th century AD to convert wind energy into mechanical energy.

Sources of energy and the ultimate energy sourceWind farms are composed of several wind turbines to produce electricity in modern times. A wind turbine is a power generator consisting of a large rotor with three blades, which is put into action by the wind.

The cons are the location, the large spaces required for centralized wind farm production, and the environmental impact.


Hydropower is clean energy that harnesses the potential energy of water located at high altitudes in mountain basins. When water falls, it acts on a turbine, producing electricity. The principle is the same as in a thermoelectric plant: the difference is that the medium that turns the turbine is water, not steam.

Currently, 16% of the world's electricity comes from this origin. It is one of the disadvantages of this source of energy. However, the construction of dams has an important environmental and social impact.

Geothermal Energy

Geothermal energy is energy generated by geological heat sources and can be considered a form of renewable energy. It is based on the use of the internal heat of the Earth (geothermal) fed by the thermal energy released in the nuclear disintegration processes of radioactive elements such as uranium, thorium, and potassium, naturally contained in the earth.

As it penetrates more profound, the temperature gradually increases by about 30°C per km in the Earth's crust.

In the case of high enthalpy geothermal sources, the exploitation of this source consists of driving the vapors coming from underground water sources towards special turbines used to produce electrical energy. And in the reuse of hot water vapor for district heating, greenhouse crops, and spas.

Marine or Ocean Energy

Oceanic energy refers to the energy contained in various forms in the seas and oceans. This immense amount of energy can be extracted from seawater with different technologies: based on the kinetic energy of fluids (currents, waves, tides) and the gradient (thermal and saline). Today many energy extraction systems have been tested, and some are already in a pre-commercial stage.

Nuclear Fusion

Nuclear fusion is a variant of atomic power. It is joining the nuclei of two hydrogen atoms in which an enormous amount of energy is released.

This process gives rise to energy from the Sun. It generates large amounts of heat that could be used to generate electricity. However, the temperatures and pressures required to maintain fusion make it arduous to control.

One of the potential advantages of fusion is the theoretical possibility of delivering large amounts of energy safely and with relatively little pollution.

The fuel for nuclear fusion is hydrogen. Due to the enormous presence of hydrogen on the planet, nuclear fusion would be considered a renewable energy source.


Published: February 21, 2022
Last review: February 21, 2022