Geothermal Energy

Geothermal energy in the WorldGeothermal energy in the World

 

Geothermal energy is the name for the science and technologic field that studies, explores and exploits such a renewable energy which is available – where potential exists, below the Earth's surface, in a range between shallow and deep depths.

 

Geothermal energy originates from the interior of the earth. In average terms, the temperature increases, with depth, about 33ºC per Km. However, due to the heterogeneity of the Earth's crust, the temperature gradient can be lower or higher than that value. It is the areas of high gradient that are of most interest in energy use. The differentiation between high and low enthalpy are generally used to characterize the thermal characteristics of the fluid, depending on whether its temperature is higher or lower than 150ºC. The use of geothermal energy generally implies the existence of a geothermal fluid (water), which transports heat up to the surface from the Earth layers well below the surface. This fluid has origin in the formation from sedimentation - as contemporary fossil water, or come from the infiltration of rainwater. In case this fluid is non-existence (e.g. dry hot rocks), water injection can be used.

 

This type of energy offers, among other characteristics, the advantage of being renewable and low polluting.

Geothermal Energy in Portugal

 

In the mainland Portugal there are mainly conditions to exploit low enthalpy used in balneotherapy, which is a common practice since the Roman Empire colonized the Iberian Peninsula (ca 25 BC), as archeologic evidence shows. More recently the resource has been used for space heating and greenhouses.

 

As a result of the energy crisis in the 70s of last century, and the development of the deep geothermal project at the Azores Island S. Miguel, aiming at the production of electricity, it led to the regulation of the sector through Decree-Law No. 560/-C/76, of July 16, which defines the regime of exploration and exploitation of geothermal resources, which leads to its integration into the public domain under the State governance.

 

Later, considering there was interest in the use of low enthalpy resources in the mainland Portugal, a new legal framework was created established by Decree-Law, 87/90 and 90/90, of March 16.