There is a source of renewable energy thousands of times larger than all the oil and gas fields together. It can be found underground, and it's earth's heat, or geothermal energy.
Although currently less than 1% of the world energy production comes from geothermal sources, extraction costs decreased dramatically over the past years, and advancements in technology made it one of the most promising renewable sources.
Geothermal power has two main sources: one is the decay of radioactive elements (such as uranium and potassium), and the other is the primordial heat, which was preserved by the earth’s crust. When the heat rises upwards towards the surface, it heats the water filtering from the rocks, which will then be used to produce energy.
Although the exploitation of this type of energy is relatively simple, it's not available everywhere but only in seismic areas, or where tectonic plaques meet.
However, the remaining areas of the earth are not without heat: at any latitude, temperature will increase by 30°C in average each Km of depth.
This type of geothermal energy is called low enthalpy, and although it won’t generate high temperatures, it can still be efficiently used for the heating and cooling systems of buildings. In this case, the process is based on a heat exchange, going from the earth to the building (for heating systems), or the opposite way (for cooling systems).
Geothermal water is quite corrosive as it contains a large amount of salts. The equipment that is used for its exploitation therefore needs to be built with resistant materials.
Stainless austenitic-ferrous steel is currently the most widely used for geothermal applications, as it’s very resistant to corrosion.
In the exchangers we produce (preheaters and evaporators) for such purposes, the parts that are intended to come into contact with sea or geothermal water are built with Superduplex, an alloy composed of chrome (25%), nickel (7%) and molybdenum (4%).
Among the most recent systems for the exploitation of geothermal energy, the most promising are the third generation ones, also called EGS (Enhanced Geothermal Systems). Their technology allows to dramatically improve energetic efficiency of both geothermal wells and dry rocks.
With EGS systems, high-pressure water is pumped underground, with the purpose of increasing or triggering the natural process of geothermal energy.
Finally, another way to increase the exploitation of this type of renewable source is cogeneration, as geothermal fields are often located in proximity of oil and gas fields.