Renewable energy sources

What are them?

Renewable energy uses natural resources such as sunlight, wind, rain, and the heat of the earth, which are constantly renewed. About 13% of primary energy in the world comes from renewable energy sources. The potential of renewable energy is enormous.

Renewable energies offer us three main advantages in comparison with fossil fuels. The first is that they are inexhaustible (oil is limited, the sun is not). The second is that they are much less polluting. Third, they can be located anywhere as anyone could have a photovoltaic or solar thermal installation in the roof.
Renewable energy sources are:




It is a silent and almost no maintenance power. It is very clean and it transforms part of the solar radiation directly into electricity using solar photovoltaic panels.

The photovoltaic cell uses the material property known as the photoelectric effect absorbing light and releasing electrons. The free electrons are captured producing an electric current. This current can be used to power electrical appliances such as computers and light.
Photovoltaic modules can be mounted on a fixed structure or on a mobile structure.
The solar tracker is a mechanical device used to orient the solar panels in a way that they are nearly perpendicular to the sun, following the sun from sunrise to sunset. This fact increase 40% the electric production.

Type of installations

  • Connected to the network. The electricity generated is introduced into the network and sold to the distributor.
  • Isolated and autonomous. They have no connection to the electricity network. The electricity is stored in batteries to meet the needs. It is typically used in rural areas.

Placas solares

Solar photovoltaic panels tracker



Solar thermal energy


Solar thermal energy is a technology that uses the sun's energy as heat. This heat is stored for later consumption. It can be used for both heating and water heating.
This system is a clean way to produce energy.
For example, water heating from the sun's heat is one of the best ways to include renewable technologies in a building. In a house system the demand for heating water can be reduced in two thirds. This will reduce expenditure on electricity or fossil fuels used for this purpose, reducing the associated environmental impacts.

Type of installations

  • Hot Water. A thermal solar panel installation to heat a tank to store hot water supplies between 60 and 80% of daily needs.
  • Radiant floor heating. This system is installed down to the floor of the house acting as a big radiator.
  • Swimming pools heating. Application of high profitability, as the temperatures needed are low (25 C) and the heat and volumes needed are large.

Energia solar termica

Swimming pool heating.



Wind energy

Wind energy is energy from wind, in other words, the kinetic energy generated by the effect of air currents. It is a source of infinite energy, renewable and non polluting that can be used to produce electricity or in water pumping systems.
This energy is renewed daily by the sun, as a result of the irregularly warming on the surface produced by the sun. The air that is over land heat, expands and rises, and the air that is colder goes down creating wind.
In the past, windmills were used for wheat grinding to get flour. Today, wind energy is mainly used to produce electricity using wind turbines

Wind turbine

Wind turbines use blades to collect the kinetic energy of wind. The air moves over the blades, which, thanks to its aerodynamic profile, causes a lift effect, making they turn. This is connected to a shaft that turns an electric generator producing electricity.




Geothermal energy

Geothermal energy is one that is obtained through the use of heat inside the Earth. This can be exploited as an energy source in many ways, the most common are obtaining electricity power, using directly the heat to use for heating the buildings or to produce hot water, and the use of this heat for heating and cooling through the heat pump.
A geothermal plant generates electricity using steam. The steam goes through a turbine that is connected to a generator and produces electricity.
In Iceland the use of geothermal energy is very common as there are a large number of volcanoes and geysers.

Geothermal heat pump

This leverages the soil temperature for Heat and cool buildings. It is very similar in concept to an air conditioning (cold / hot). The difference is that instead of exchanging heat to the air in the exterior of the house, it uses the ground for the exchange of heat.
In winter, the heat pump absorbs heat from the ground and releases it into the building. In summer, the building absorbs heat and releases it into the ground.
The advantage is that the earth maintains a constant temperature, 3 m depth has a temperature between 10 ºC and 16 ° C. This allows more efficient heat exchange, and therefore lower energy consumption.




Hydropower is probably the most exploited renewable energy over time. The first water wheels have been developed in East about two thousand years ago. Later they were used for grinding. The Industrial Revolution spread the use of these, taking profit of the force of the water for making the work in foundries, forges, or by moving the machines in factories. The mechanical power was obtained from hundreds of watts to tens of kilowatts. The first hydraulic turbine was developed towards the mid-nineteenth century. Comparing the turbine to the water wheel, it is smaller, more compact and more efficient operating at a greater speed. Some time later the turbine was suitable for generating electricity.

Minihydraulic power plants

Minihydraulic energy is the production of electricity from the energy of water in small scale. It can supply electricity to a small town or to a small industrial plant. A hydroelectric power plant is considered minihydraulic when their capacity does not exceed 10 megawatts (MW). Contrary to the big water projects, some of which are not respectful towards the environment, small systems cause less impact to the environment. With good management of this resource, the ecological effects are insignificant.





Biomass is as renewable source obtained from organic material from plants, animals or the result of their transformation. Part of this biomass is used for energy production. Biomass is forest and agricultural residues, liquid biofuels and biogas.
Solid Biofuels

They are byproducts of solid biomass used in energy conversion processes. Examples are cereal straw, wood, chips and pellets.
Pellets are small portions of compressed sawdust that is used as fuel for boilers. To avoid cutting down the trees, the wood from pruning is used or waste in the wood factories. It is obtained by pressing. One of its advantages is that the material is reused.
When burning wood, it releases the same amount of CO² into the atmosphere than the plant has absorbed over its life cycle. Therefore, the balance is zero CO² emissions.


Wood pellet

Liquid Biofuels

Biofuels are produced from living organisms or from byproducts of organic matter such as food waste, including used cooking oil. Unlike other renewable energy sources, liquid biofuels can be used to transport.
There are first and second generation fuels. The first generation came from virgin raw materials like palm oil, corn, sugar cane or beet. The second generation comes from waste oil, agricultural and forestry waste or algae. The advantage of second generation biofuels is that using waste and raw materials agricultural land is not needed.
The most common biofuels are bioethanol and biodiesel. Both are traded mixed. The ethanol is sold mixed with 20% gasoline. Biodiesel is presented as B10, B20 or B30 containing a 10, 20 or 30% biodiesel.


Biogas is a fuel generated in natural environments or specific devices. It is produced from decomposition reactions of organic matter through the action of microorganisms in the absence of oxygen (i.e. anaerobic atmosphere). The resulting gas is called biogas and consists of methane (CH4), carbon dioxide (CO²), carbon monoxide (CO) and other gases.
This process can apply to the majority of organic waste, such as the treatment of sewage sludge, food waste, farm waste, turning it into a stable product for recycling and produce biogas, used later for the production of energy. Nutrient-rich solids obtained after digestion can be used as fertilizers.

Process of biogas production (biogestor)
• animal droppings and rests of food mixed with water or mud.
• In the biogestor, the action of bacteria decomposes the mud, turning it into methane and fertilizer.
• The methane gas can be driven to a power generator or a heater.
• The rests are used as fertilizer.