Renewable energy is today the source of clean and limitless power that could help mankind reduce its dependence on fossil fuels.
The renewable resources available on the planet are here since the creation of the planet, but mankind was not very aware of their presence, and the fact that they could represent someday an alternative to the polluting energy produced by fossil fuels.
Renewable Energy Definition
Renewable energy is a term used to describe a group of alternative sources of power that are limitless because they are replenished within a human’s lifetime.
The most common sources of renewable energy available on the planet are represented by solar, wind, hydropower, biomass, tidal and geothermal.
Nuclear energy is not considered renewable because the nuclear fuels used in the nuclear fission reaction are limited resources.
However, nuclear energy is an alternative source of power because nuclear power plants produce electricity without releasing harmful emissions into the atmosphere.
Types of Renewable Energy
All types of renewable energy are produced today using the renewable resources available on the planet.
In terms of energy, the renewable resources available for us are represented by sunlight, water, air, the combined gravitational forces of the Sun, Moon and Earth, the inner core of the planet, biomass, trash and both human and animal organic waste produced daily by our civilization.
Sunlight is a renewable resource used to produce solar energy with the help of solar modules or mirrors.
1. Solar Energy
Being produced by the Sun, the sunlight is a renewable resource used by photovoltaic (PV) solar cells to produce clean electricity for domestic use or at large scale in solar power plants.
Generating electricity using the sunlight and the photovoltaic effect is called active solar and can be done using PV solar panels.
Clean energy can also be produced by using a large number of mirrors that are reflecting the sunlight on a central point located at the top of a tower where an agent such as molten salt is heated at high temperatures to produce steam, which is then used to spin a turbine and produce electricity with the help of a generator.
Because heat can be stored in the molten salt for many hours, the agent can generate steam many hours after the sunset, and this is the reason why a concentrated solar power plant (CSP) can produce clean electricity even during the night or in cloudy days.
The sunlight is also used to heat water for free (using the Sun), for cooking (solar cookers), etc.
2. Wind Energy
Air represented by wind is another renewable resource produced by the Sun and available for us to generate clean electricity using horizontal-axis and vertical-axis wind turbines.
Our star heats the different layers of air in our atmosphere in an uneven way (the layers of warm air start rising in the atmosphere, while the layers of colder air start descending, and this movement of the different layers of air in the atmosphere is what we call ‘wind’).
The windy areas of the planet are used today to produce electricity on a large scale (both onshore and offshore), but we are also using the power of the wind to produce clean electricity for domestic use using small wind turbines (horizontal-axis and vertical-axis wind turbines).
Wind can blow 24/7, which means that a wind turbine can generate power during the day, but also during the night.
3. Hydropower
Water is a another renewable resource that can be used to produce clean electricity in hydroelectric power plants.
A hydroelectric power plant uses the kinetic energy of the moving water (fast streams) or falling water (uses the gravitational force of the planet) to spin powerful underwater wind turbines and generate clean electricity by rotating the shaft of a massive generator.
Hydropwer uses two natural and renewable resources available on the planet.
The Sun is responsible for the water cycle on the planet, and the movement of the water is used by hydroelectric power plants (built on fast streams) to generate clean power.
Hydroelectric power plants using dams rely on the gravitational force of our planet to produce power.
Falling water is used to spin the underwater turbines and produce electricity using large generators.
Hydropower or hydroelectric energy (hydroelectricity) has the highest share (among all renewables) in the energy mix of the planet.
4. Biomass
Biomass represented by wood and plant waste, agricultural waste, energy crops, trash and human and animal organic waste is another form of renewable energy because is produced every day by our civilization.
Until we have people, forests, grass and animals on the planet, we can say that biomass is a never ending source of renewable energy for mankind.
Burning biomass for energy generation does release greenhouse gas emissions into the atmosphere, which means that biomass is only a renewable energy source, and not a clean source of power for us.
However, if we can turn wood and plant waste, trash, human and animal waste into energy, we can say that we found a way to recycle waste materials and produce power while cleaning the planet.
5. Geothermal Energy
The geothermal resource available today is another form of renewable energy because is generated by the inner core of our planet, which is about as hot as the surface of the Sun.
The underground heat radiated by the inner core of the Earth produces the geothermal resource that reaches the surface of the planet under the form of hot water and steam.
The hot steam is used to spin steam turbines, which generate clean electricity using powerful generators.
The hot water is used to produce steam, but also for residential heating and cooling.
There are many countries on the planet with geothermal resource available (at the surface), but among all of these, Iceland relies on this natural resource the most (the share of geothermal power in the country’s energy mix reaches 25 percent).
6. Tidal Energy
Tidal power is a form of hydropower that converts the energy from the natural rise and fall of the tides to electricity.
Tides are produced on our planet by the combined effects of gravitational forces exerted by the Sun, Moon and the rotation of our own planet.
Tidal power plants can be installed only along coastlines because these areas often experience two high tides and two low tides on a daily basis.
The current technology used to produce tidal energy requires that the difference in water levels between the high tide and the low tide must be at least 16 feet (5 meters) to produce electricity.
Mankind uses today several technologies created to harness the energy of the tides.
1. Tidal barrages
This technology is considered the most efficient one because relies on a dam that utilizes the potential energy generated by the change in height between high and low tides.
That energy compresses air or turns a turbine to generate electricity.
2. Tidal fences
These are vertical axis or horizontal axis underwater turbines that operate in strong currents and produce electricity by rotating the shaft of a very powerful generator.
3. Tidal turbines
Tidal turbines look like very robust wind turbines because they operate underwater in strong sea currents.
These turbines operate both at high tide and low tide, so they need to spin in both directions forward and backward.
The generators used by tidal turbines are reversible electrical generators because they have to generate electricity 24/7.
Final conclusion
Renewable energy has advantages and also disadvantages because as I already mentioned above, renewable does not refer to clean power.
Renewable energy is a great form of free power for mankind because is a never ending source of energy.
To be clean, an energy source needs to be a zero emission source of power, such as solar energy, wind power, tidal energy, hydropower and geothermal energy.
Biomass is a form of renewable energy that is not clean (because it releases harmful emissions into the atmosphere when burning).
However, instead of using fossil fuels like coal, oil and natural gas on a large scale, we rather concentrate our efforts to increase the generation capacity for renewable energy, because the future of mankind is renewable.
