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Renewable energy is a type of energy derived from naturally replenishing but finite sources such as sunlight, wind, rain, tides, waves, and geothermal heat. They are virtually inexhaustible in duration, but limited in the amount of energy available per unit of time. Renewable energy often provides energy in four major areas: electricity generation, air/water heating/cooling, transportation, and rural (off-grid) energy services.
Some are considered “inexhaustible” in the sense that they regenerate at least as fast as they are consumed, or are not “exhaustible” on the scale of “geological eras”. Exceptions are some energy resources that are renewable but exhaustible; for example, forests are considered renewable but can be depleted by excessive human exploitation.
Renewable resources, whether material or energy, are natural resources that are renewed over time (at a rate greater than or equal to the rate of consumption/use) due to natural properties or human production, and can be considered inexhaustible or available for human use almost indefinitely. A renewable resource is also said to be “sustainable” if its rate of regeneration is equal to or greater than its rate of use.
As renewable resources are also an energy source, there is a wide range of different types of renewable energy sources such as wind, solar, hydropower, geothermal, biomass, and biofuels. Wind and hydroelectric power are the direct result of differential heating of the earth’s surface, which causes air to move (wind) and precipitation to form as the air is lifted. Solar energy is the direct conversion of sunlight using panels or collectors. Biomass energy is stored sunlight contained in plants. Other renewable energies that do not depend on sunlight are geothermal energy, which is the result of radioactive decay in the earth’s crust combined with the original heat of the earth’s accretion, and tidal energy, which is a conversion of gravitational energy. It is useful to point out that the forms of energy present on our planet (with the exception of nuclear energy, geothermal energy and tidal energy) are almost all derived from solar radiation:
- without the Sun there would be no wind, which is caused by the irregular heating of air masses, and with it wind energy;
- biomass energy can be considered chemically stored solar energy, through the process of chlorophyll photosynthesis;
- hydroelectric energy, which uses waterfalls, would not exist without the water cycle from evaporation to rain, triggered by the Sun;
- fossil fuels (coal, oil, and natural gas) derive from the sun’s energy stored in the biomass millions of years ago through the process of chlorophyll photosynthesis.
As we have said, renewable energy sources have indisputable advantages. Above all, the absence of polluting emissions and their inexhaustibility. The use of energy from renewable sources does not affect, therefore, the availability in the future. Renewable energies offer advantages for the environment and human health. In contrast to fossil fuels, which release CO2 emissions into the atmosphere and accelerate global warming, renewables are sustainable and allow for clean electricity production. The fact that they come from readily available and inexhaustible sources allows renewable energy to reduce dependence on foreign suppliers and to develop the domestic economy.
Renewable energy does not emit pollutants and does not present the problem of waste to be disposed of. In addition, it is economical, creates jobs and allows for the combined use of multiple energy sources. In fact, renewables can be used in synergy with each other. Renewable energy sources include:
- Solar energy
- Wind energy
- Geothermal energy
- Biomass energy
- Ocean energy
Solar energy represents the most known, widespread and efficient renewable source in Italy. It allows the production of electricity starting from the sun’s rays and, to transform solar energy into electricity, it uses photovoltaic or solar power plants.
- Photovoltaic systems use silicon panels to transform solar radiation into electricity. Photovoltaic systems can be installed on the roofs of condominiums or detached houses. Among their major advantages there is undoubtedly the savings in the bill, which combines perfectly with tax incentives for installation.
- Solar systems are connected to a storage tank that heats water, replacing the boiler or water heater.
- Concentrating solar power is a system based on the use of mirrors that channel heat into boilers capable of starting a thermoelectric plant.
- Passive solar, finally, exploits the sun’s rays in a natural way through the construction of buildings capable of passing a greater amount of radiation.
Wind energy is the energy that is generated by exploiting the wind. Using wind blades, the kinetic force of the wind is used to produce mechanical energy, from which electricity is then generated. Wind energy is therefore the energy produced by wind currents and can be considered a form of energy derived from solar energy. The formation of winds, in fact, is linked to factors such as the Earth’s rotation and atmospheric temperature.
The transformation of energy occurs through turbines and wind blades, in a system that resembles windmills.
In order to ensure the efficiency of the system, as well as a good quality of the same, it is essential to place the blades in large areas and particularly windy. In fact, the ideal solution is to install the blades near seas and oceans.
Geothermal energy is that which exploits the natural heat of the Earth, released by the processes of nuclear decay of radioactive elements present within the nucleus, the mantle and the earth’s crust, such as potassium and uranium. This heat is subsequently converted into electricity by geothermal power plants. The flow of steam coming from underground makes a turbine move and this mechanical energy is transformed into electricity by an alternator. It is, therefore, a mechanism that can only work thanks to high temperatures.
Hydropower is produced by the movement of water. This form of energy was once used to run mills. Today, the kinetic energy produced by waterfalls, rivers, waves and tides is converted into electricity using turbines. The energy is produced by hydroelectric power plants: these are usually built in the mountains, close to water courses. In this way it is easier to exploit the combination of kinetic energy and the force of gravity. Among the constructions that allow to maximize this system there are dams: these ensure the channeling of water resources in specific basins. For these plants, it is possible to use power plants with accumulation or flowing water systems.
Biomass energy is generated from waste produced by man and, therefore, cannot be considered inexhaustible. This energy is produced from fuels or organic substances and industrial and agricultural waste through combustion processes. It is derived from plants and animals and allows the production of heat and electricity, as well as liquid fuels. Energy derived from biomass is mainly used by transportation companies, to power vehicles, and by manufacturing industries.
Renewable energy also includes the so-called ocean energy, which must be distinguished from hydroelectric power. This, in fact, uses the movement of currents and tides, or the motion of the waves, to produce electricity. It should be remembered that the oceans are also able to produce thermal energy from the heating of the water caused by solar radiation. Marine energy works in every way like wind energy: it is recovered through technologies that use blades or turbines set in motion.
The need to produce more and more renewable energy and to get away from traditional sources is a need shared by all countries. According to the latest data, green energy contributes to more than a third of the world’s total electricity production. Renewable also rhymes with sustainable and it is precisely in that direction that the economy, necessarily circular, of the future must look.