Under the earth we walk on beats an energy that is born from internal heat, silent, so constant that neither the night nor the clouds can interrupt it. We don’t see it, we don’t hear it, but it is there: an engine running since the planet was formed. In recent decades, as we looked to the sun and wind to fuel our modern lives, that subterranean heat remained almost forgotten. It is an energy that has always been there, waiting to be understood.
What is Geothermal Energy?
Geothermal energy refers to the heat retained within the Earth. This renewable energy source is harnessed for electricity generation, heating, and air conditioning. The heat is stored in soils, rocks, and groundwater at varied depths and temperatures. The core of the Earth reaches astonishing temperatures of about 5,982 ºC—nearly equivalent to the surface of the sun. As this heat rises, it warms the mantle and crust, enabling us to capture and convert it into usable energy.
How is Geothermal Energy Generated?
The process behind geothermal energy generation is straightforward. Heat from the Earth’s interior warms underground water. When this water reaches temperatures exceeding 150 ºC, it is viable for electricity production. For lower temperatures, typically between 30 ºC and 100 ºC, the heat is utilized for district heating or industrial applications.
Furthermore, surface geothermal harnesses stable ground temperatures ranging from 10 to 15 ºC. Geothermal heat pumps capitalize on this consistency by extracting heat in winter and transferring it back in summer, leading to energy savings of up to 80% compared to traditional systems. Recent advancements include Enhanced Geothermal Systems (EGS), which create additional resources in previously unfeasible locations.
How Does a Geothermal Power Plant Work?
A geothermal power plant operates similarly to a thermal power plant, using steam to turn a turbine that drives a generator. The primary distinction lies in the steam’s origin—geothermal energy sources their heat from the Earth’s subsurface.
There are three main technologies employed:
- Dry steam: Utilizes steam straight from the reservoir.
- Flash steam: Evaporates hot water by lowering its pressure.
- Binary cycle: Transfers heat to a secondary fluid that vaporizes at lower temperatures.
These power plants can generate electricity consistently, providing a firm energy supply that stabilizes electrical grids by mitigating the variability seen in other renewable sources.
What is Geothermal Energy Used For?
Geothermal energy’s primary application is electricity generation; countries like Iceland heavily rely on it. In Europe, while usage is less extensive, around 1 gigawatt is currently installed. However, the most significant growth area is in heating. In numerous European cities, subterranean heat is utilized for heating residential buildings through extensive networks.
Geothermal energy also serves diverse functions, from heating greenhouses and powering spas to regulating temperatures in fish farms and air conditioning large buildings like university campuses.
Pros and Cons of Geothermal Energy
The advantages of geothermal energy are compelling:
- Constant and manageable energy supply, independent of weather conditions.
- Low emissions and minimal visual impact.
- High efficiency in residential applications, reducing energy consumption significantly.
- Long operational lifetime of 25 to 50 years with minimal maintenance.
- Potential for extracting lithium as a by-product.
However, like any energy source, it has its drawbacks:
- High initial investment that comes with drilling and exploratory risks.
- Need for complex geological studies that may require technical interventions.
- Limited suitable locations owing to factors like heat and geological permeability.
- Shortage of specialized labor in the field.
- Insufficient regulatory frameworks compared to other renewable energy forms.
Are There Geothermal Power Plants in Spain?
Currently, Spain does not operate any geothermal power plants, but there is significant growth in surface geothermal energy for heating and cooling. Various institutions are already employing geothermal heat pumps.
Major developments could stem from the Canary Islands, where volcanic origins make it a hotspot for medium to high-temperature resources. The Deep Geothermal project, funded by NextGenerationEU, aims to cover up to 50% of exploration costs, marking a significant step forward.
A Source Without Limits
Geothermal energy stands out as the only renewable energy source that does not rely on sunlight or wind. It can continuously power homes, industries, and cities. For Spain, harnessing this energy could be pivotal in achieving energy independence and advancing its ecological transition.