The energy demand on planet Earth increases year after year, and the energy sources used to produce electricity are renewable such as solar, wind, hydro, biomass, geothermal, tidal and hydrogen and also non-renewable such as nuclear, coal, oil and natural gas.
Scientists are working today to develop new sources of energy (preferable clean and renewable), but for the moment their progress is small and pretty slow.
Our list will start with non-renewable energy sources (mainly fossil fuels) because today they still represent the main energy sources used on the planet to generate electricity and heat. Let’s see what are energy sources available today.
Non-Renewable Energy Sources
Non-renewable energy sources consist of fossil fuels such as coal, oil (or crude oil) and natural gas, and mineral fuels such as natural uranium and natural thorium.
1. Coal Energy
Coal is the main fossil fuel used on the planet to generate electricity and heat through combustion in power plants and stoves (used only for heating and maybe for cooking in some countries).
Coal represents a cheap energy source, but the amount of harmful emissions released into the atmosphere during burning is so high that coal is known the cheapest, but the dirtiest energy source used today on the planet to produce electricity and heat.
To produce electricity, coal is used to heat water and generate steam that will make a turbine consisting of thousands of propeller-like blades to spin.
The turbine will spin at very high speed in a strong magnetic field and will generate electricity, and the steam will be condensed and returned to the heating boiler to be heated and used again.
40% of the electricity produced in the world today is generated by coal (some countries rely on coal even more) and this is the reason why air, water and land pollution has reached unbearable levels in some countries.
Coal has today a share of 30.4% in the U.S. electricity generation.
2. Oil As Energy Source
Oil is used as crude oil and as petroleum products.
Crude oil can be found in liquid form in underground reservoirs (pools) or even in tiny spaces located within sedimentary rocks.
Crude oil can also be found near the surface of the tar (or oil) sands.
Petroleum products are produced from crude oil or from hydrocarbons contained by coal, natural gas and biomass.
To get petroleum products, the crude oil extracted is sent to refinery, and there the different parts of the crude oil will be separated into petroleum products such as: gasoline, diesel fuel, heating oil, jet fuel (kerosene), petrochemical feedstocks (chemical feedstocks derived from petroleum), lubricating oils, waxes and asphalt.
Gasoline and diesel fuel are used to power vehicles, jet fuel is used by planes, and heating oil is used as fuel for heating.
To generate electricity, oil is used to heat water and produce steam that will spin a turbine (conventional steam technology).
The combustion turbine is another technology that burns oil at high pressure to generate hot exhaust gases that will spin a turbine to produce electricity.
There is another technology called combined-cycle that burns oil in a combustion turbine and the heated exhaust gases will generate electricity. The exhaust gases are recovered and used again to heat water in a boiler, and the steam resulted will spin another turbine.
However, burning oil to generate electricity releases harmful emissions which pollutes the air, the water and the soil.
Oil has today a share of less than 1% in the U.S. electricity generation.
3. Natural Gas Energy
Today, natural gas is still a pretty affordable source of electricity and heat, but because >natural gas is a limited resource, the price paid for natural gas as energy source will grow progressively.
As an energy source, natural gas can be used as compressed natural gas (CNG) or as liquefied petroleum gas (LPG), which is used to power vehicles.
There are three different technologies used to generate low-carbon electricity from natural gas.
Steam generation units are using natural gas as fuel to heat water and produce steam that will spin a turbine to generate electricity.
Centralized gas turbines and combustion engines are using natural gas (or other fossil fuels) to produce hot gases during burning.
The hot gases will spin a turbine and will generate cleaner electricity using generators.
Combined cycle units are used by power plants and consist of both a gas turbine and a steam unit.
The gas turbine will burn natural gas to produce hot gases that will spin the turbine to generate electricity and the waste heat resulted in this process will be used by the steam unit to generate electricity.
Another technology used to generate electricity and heat using natural gas is called distributed generation.
This technology can be found in residential, commercial, and industrial sites and works like a small power plant that generates electricity and heat for the entire site.
Natural gas is a low-carbon energy source that will replace coal and oil in the future as the main source of electricity and heat on the planet.
Natural gas has today a share of 33.8% in the U.S. electricity generation.
4. Nuclear Energy
Today, about 11% of the world’s electricity is generated by nuclear power even if uranium and thorium are considered fossil fuels that are finite resources and pollute the environment.
All these nuclear fuels can be used in nuclear reactors to generate clean electricity.
However, even if the electricity generated during the nuclear fission reaction is clean (no carbon emissions involved in the process) the nuclear waste resulted is very harmful for the environment and for all living beings.
Nuclear energy can become a viable source of clean power that is suited for the future society only if we find a nuclear fuel that produces no nuclear waste.
Thorium is a radioactive chemical element that has superior physical and nuclear properties than uranium and is also more abundant in nature.
However, thorium produces nuclear waste during the nuclear fission reaction (less than uranium) and is a finite resource, so does not represent a renewable energy source for the future.
Nuclear energy accounts today for 19.7% in the U.S. electricity generation.
Renewable Energy Sources
Renewable energy sources such as solar, wind, hydro, biomass, geothermal, tidal and hydrogen represent the alternative energy sources that will replace the dirty fossil fuels in the future for a cleaner environment.
1. Solar Energy
Solar energy is a free, renewable and clean source of power that is produced by the Sun and can be harnessed to generate green electricity (using solar panels) and hot water (using solar heaters).
Solar power accounts for less than 1% in the energy mix of the U.S. because the solar technology used today is not very efficient and is also pretty expensive.
However, mankind has learned that the Sun is a great source of free electricity that can help us get rid of fossil fuels.
2. Wind Energy
Wind power represents an ancient source of clean energy that was first used to navigate the sea and in agriculture to pump water and grind grain.
Today, we are using wind turbines to turn the kinetic power of the wind into clean electricity.
About 5% of the electricity produced in the U.S. is generated by wind turbines and in Europe the share of the wind power in the energy mix is even higher.
Being a clean and renewable energy source (wind is produced by the Sun) wind power represents an energy source of the future.
3. Hydropower
The kinetic power of the moving or falling water is used today to generate clean electricity with the help of turbines connected to generators.
Hydropower has been used by mankind since ancient times in agriculture for crop irrigation and to operate different mechanical devices such as sawmills, gristmills, textile mills, dock cranes, trip hammers, domestic lifts, ore mills and others.
At the end of the XIX century, hydropower was used to generate electricity and the first commercial hydroelectric power plant in the world was built at Niagara Falls in 1879.
To generate electricity at large scale, the power of the wind is harnessed today by large hydroelectric dams.
Hydropower is a clean and renewable energy source and today accounts for 6.5% in the U.S. electricity generation.
4. Biomass Energy
Biomass is another major source of renewable energy in the world today because mankind is a great producer of waste.
Wood waste, agricultural waste, plant-based waste (used as animal feed), landfills, organic waste and green algae are all considered great sources of biomass that can be used to produce biofuels such as ethanol and biodiesel for vehicles, and also methane gas (known as biogas or landfill gas).
In the coal power stations of today, biomass can be used as a greener alternative to coal that can reduce the level of emissions released into the atmosphere by the plant.
Biomass has today a share of 1.5% in the U.S. electricity generation.
5. Geothermal Energy
Geothermal energy, also known as thermal energy is another source of renewable energy that is used to produce clean electricity and hot water.
Geothermal energy can generate clean electricity using the underground heat that is collected by geothermal heat pumps and used to produce steam that will spin a turbine.
The turbine will produce clean electricity while spinning with the help of generators.
The underground hot water (naturally heated) can be used as a free heating source during the winter for homes and buildings.
Geothermal power has today a share of 0.4% in the U.S. electricity generation.
6. Tidal Energy
Tidal energy converts the kinetic power of the tides into clean electricity.
Tidal energy is pretty new on the market today and tidal power has 0% share in the U.S. energy mix.
The tides on planet Earth are produced by the gravitational forces of the Moon and Sun and that is the reason why tidal energy is considered a renewable energy source.
The technology used to harness the power of the tides today is still under development and is very expensive, but in the future, the costs with the technology could become competitive on the market and this will unleash the true potential for clean power provided by the coastal areas of the planet.
7. Hydrogen Energy
Hydrogen is a very abundant element on Earth (can be found in water) and in the known universe, so can be considered as a renewable energy source.
Hydrogen also represents a clean energy source because burning hydrogen as fuel in the presence of oxygen releases no harmful emissions into the atmosphere.
Hydrogen is the clean fuel that was first used by N.A.S.A. to launch the space shuttles.
Hydrogen cannot be found in gaseous state here on the planet, but can be found in combination with another element in water and in many organic compounds (hydrocarbons) specific to fossil fuels.
This is the reason why hydrogen is mostly produced today from fossil fuels such as natural gas.
Space ships are using hydrogen fuel cells to produce clean electricity and pure water (drinkable water) as waste.
A hydrogen fuel cell combines hydrogen and oxygen to produce electricity, heat and pure water as a byproduct.
In the future, hydrogen fuel cells can be used to provide clean electricity and heat for buildings, and also clean power for electrical vehicles.
Conclusion
The human society is heading towards a cleaner future where the dirty fossil fuels will be used less often, while the clean and renewable energy sources will slowly become the main source of power in the energy mix of the planet.
The environment must be cleaner of any form of air, water and soil pollution in order to be preserved for the future generations.
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