Renewable energies
What are they?
Renewable energy sources are natural resources capable of regenerating themselves in a short period of time and in a sustainable way.
Geothermal energy, biomass, tidal and wave power, wind, sun, and water are examples of renewable energy sources. These sources prevent the need to import fossil fuels such as coal and natural gas to generate electricity, avoid the emission of greenhouse gases, and reduce the price of electricity in the market, contributing to greater economic and environmental sustainability for the country.
Water
Hydropower production occurs in hydroelectric power plants, which can be of two types: those with reservoir storage or run-of-river plants. Small hydroelectric plants have a power output of up to 10 MW, while large plants exceed this value.
The operation of hydroelectric plants is based on the difference in height between the reservoir level (upstream) and the river level downstream. This difference in potential energy is converted into mechanical energy by rotating the blades of a turbine, which, in turn, drives the generator responsible for electricity production.
In the case of run-of-river power plants, there is no reservoir; only the natural flow of the river is used whenever available.
Hydropower plants are one of the most efficient forms of electricity generation and play an essential role in the stability of the electrical system. Currently, in an average year, about 30% of the electricity consumed in Portugal comes from hydropower.
Wind power 
Wind is the movement of air masses generated by the uneven heating of the atmosphere and the orography of the terrain. Throughout history, it has been used to propel sailing vessels, grind grain, and pump water from wells. Today, it plays a fundamental role in the production of electricity through wind energy.
Wind farms are installed in locations where the average annual wind speed exceeds 6 m/s, which, in Portugal, occurs mainly in mountainous areas and along the coast. In these plants, wind turbines convert the force of the wind into electrical energy: the blades capture the kinetic energy of the wind, causing the generator shaft to rotate, which produces electricity.
In addition to onshore wind farms, there are also offshore wind farms, which take advantage of more consistent and intense winds, as well as the vast area available.
However, their implementation requires consideration of restrictions such as fishing zones, protected areas, and shipping routes. Currently, about 25% of the electricity consumed in Portugal comes from wind power, making this energy source an essential pillar of the national electricity system.
Bioenergy
Solar 
Electricity production from the sun can be done through photovoltaic solar panels or thermal solar concentrators.
In the case of photovoltaic panels, composed of photovoltaic cells, solar radiation is captured and converted directly into electricity. Photovoltaic cells capture solar radiation and convert it directly into electricity. Concentrated solar thermal systems, on the other hand, use mirrors to concentrate sunlight and heat a fluid, generating steam that subsequently moves turbines, producing electricity.
In addition to generating electricity, solar energy can also be used for water heating in homes, buildings, and industrial processes, reducing the need for electricity or gas.
Photovoltaic technology allows for the production of electricity without local emissions, noise, or the need for moving parts. Due to its modularity and small unit size, it enables various forms of application or integration, whether on rooftops, facades, or the ground.
Portugal is one of the European countries with the most generous solar resources, with Lisbon being the third European capital with the most hours of sunshine per year.
Oceans 
The oceans are an abundant source of renewable energy. However, the equipment to convert this energy into electricity is still under development, with a focus on improving efficiency and resistance to the marine environment.
Pico Island, in the Azores, is home to a 400 kW power plant, the first in the world to regularly produce electricity from wave energy. Furthermore, along the Portuguese coast, various technologies have already been tested, and the São Pedro de Moel Pilot Zone, located between the ports of Figueira da Foz and Nazaré, covering approximately 320 km², with depths varying between 30 and 90 meters, is in operation, serving as a space dedicated to the demonstration and development of innovative projects for harnessing wave energy.
In addition to wave energy technologies, the world's first floating offshore wind energy project – the Windfloat project – was installed in Portugal in 2019. It was installed to explore the potential of wind energy at sea, since offshore areas provide more consistent and intense winds than coastal regions.
Geothermal 
Geothermal energy is generated from heat originating from the Earth's interior. Regions with volcanic activity, such as magmatic intrusions and geothermally active areas, have a high potential for this type of energy.
Electricity can be produced in geothermal power plants, where the Earth's heat generates water vapor that moves the blades of a turbine. This rotary motion is transferred to the shaft of a generator, which transforms mechanical energy into electricity.
In Portugal, the Azores Autonomous Region is home to several geothermal electricity production units, serving as a pioneering example in the use of this renewable source.
In addition to electricity generation, geothermal energy is widely used for heating and air conditioning, being applied in agricultural greenhouses, thermal baths, industrial processes, and building heating or cooling systems through geothermal heat pumps.
