What is Energy?
We consider energy to be the capacity to produce work or to perform an action. This capacity has its origin in two types of energy source: renewable and non-renewable.
Renewables
Renewable energy sources come directly from nature and are renewed from inexhaustible natural cycles. Examples include: water, biomass, geothermal energy, tides, waves, solar radiation or wind.
Non-Renewables
Non-renewable energy sources are limited resources which are depleted as they are used and are dependent on the resources to be found on the planet or their renewal rate. Examples include fossil fuels: coal, oil and natural gas.
Forms of Energy
Energy can manifest itself in different ways. We have kinetic energy, electricity, mechanical energy, nuclear energy, potential energy, chemical energy, thermal energy, etc. Consult our Energy Dictionary to get more information about these forms.
Bearing in mind the energy transformation processes, we can also classify it as primary, secondary or final energy.
Primary energy is the energy available in nature before being converted or transformed. This type of energy may be used directly or subject to changes. It covers renewable and non-renewable energy sources. Examples include coal, oil, natural gas, solar radiation, water or wind.
Secondary energy is the result of processes involving the transformation of primary energy into forms of energy suitable for different practical uses, naturally suffering the losses inherent to those processes. Oil is an example of a primary energy source, which is transformed at refineries into secondary energy sources such as petrol, diesel or liquefied petroleum gas. Another example of secondary energy is the high-voltage electricity produced at power stations which use renewable or non-renewable energy sources.
Final energy is the energy that is received and used directly by the consumer or ordinary citizen. Examples include the diesel or petrol we use to fill up the car and the low-voltage electricity that reaches the household appliances in our homes. Sometimes primary energy is converted directly into final energy. For example, solar radiation is converted by solar panels into thermal energy, a final energy used in water heating. Forest waste is converted by combustion in a fireplace into final thermal energy.
