The internationalization strategies in the european renewables market: Enel Green Power Iberian expansion

Renewable energy sources are those resources that are not destined to run out over time. These resources are not "scarce", meaning that the use of them does not preclude a new use in the future, thus their main characteristic is that they renew their availability in the short term.

By definition all fossil fuels such as coal, gas and oil are excluded from this category, as they are subject to depletion and their regeneration cycles cannot be measured in the scale of human time, but in geological time. Nuclear energy is also excluded, as its use depends on limited reserves of materials that do not regenerate at the same speed with which they are consumed.

It is possible to identify six categories of renewable energy sources:

Solar: it is the energy associated with solar radiation and represents the primary source of energy on earth. From this energy derive, more or less directly, almost all the other sources of energy available to man. In fact, all other sources of energy, renewable and non-renewable, are actually stored forms of solar energy. Solar energy can be used to generate electricity (photovoltaic) or to generate heat (solar thermal).

Wind: wind energy is the kinetic energy extracted from the wind. It is converted by wind turbines (rotors) into mechanical energy of rotation and used to produce electricity. Since this is a non-constant phenomenon in terms of power and direction, dependent to the morphology of the land and the environment, it is not possible to locate wind farms in all areas.

Hydroelectric: it is the kind of energy that originates by exploiting the movement of large masses of flowing water. The mass of flowing water produces kinetic energy which, thanks to a turbine and an alternator, is then converted into electrical energy. It is the most developed form of renewable energy in the world.

Bioenergy: the biomass is constituted by biological substances of animal or vegetable origin, which appropriately treated can be transformed into energy. It is used both to generate heat and to generate electricity.

Geothermal: it represents that branch of geophysics which has as its object of study in the earth's heat and, by extension, in the exploitation of the latter as energy for human and industrial use. It is one of the lowest exploited energy sources, representing less than 1% of the world's energy production.

Ocean energy: it is the electricity derived from the force contained in the sea, particularly by the waves. This energy source can be extracted with different technologies: fluid dynamics (currents, waves, tides) and gradient (temperature and salinity). Unfortunately it has very limited capacity to exploit.