Geothermal energy: is energy in the form of heat, which accumulates under the Earth’s rigid surface. In one liter of the Earth’s underground soil, there is an average of 2.6 kV of energy.
The planet Earth has enough thermal energy stored to satisfy 30 million years of the population’s needs. The Earth’s abundance of energy can be estimated as having the same life-span as the Sun.
A study done in Central Europe reveals that, for every 100 meters below the Earth’s surface there is an average temperature increase of 3 degrees Celsius. In the planet’s upper mantle there have been recorded temperatures of 1200 ˚C, whereas the Earth’s core temperature is predicted to be about 6000 ˚C. The Earth’s temperature is hardly affected by the heating factor of the sun. Irrespective of the low heat- conducting value of soil, the heat of the sun becomes negligible somewhere around 15-20 meters below the Earth’s surface.
In comparing renewable energy sources, Geothermal Energy has major advantages of not being affected by the by ambient temperatures, time of day or year. This remains constant.
As much as geothermal energy is readily available, its technology can be taken advantage of without the construction of expensive transportation systems for the working fluid. In comparison with traditional heating methods, which emit high volumes of carbon dioxide gazes, only a trace of CO2 is emitted when installing a Geothermal Energy system.
In the meantime, this technology is sufficiently developed to be installed almost anywhere in the world. In Germany, geothermal systems, with the help of thermal pumps, have been installed and provide close to 600 (under inclusion of the geothermal heat close to surfaces from the warm pumps) megawatts of environmentally friendly heat. The potential energy capacity of the world can be estimated at 15000 to 20000MW of thermal energy and 8400 MW of electric energy. These estimations comprise only a partial potential of the Earth’s energy capacity. The energy capacity increases when taking into consideration the Earth’s lower layers. This harnessed energy can supply the world all of its heating needs.
System Setup
Near-Surface Geothermal Energy
Although temperatures of only 8-12 ˚C are recorded within the first 100 meters below the Earth’s surface, geothermal heating technology can be applied. To obtain desired heating temperatures for a medium, a thermal pump is necessary. Underground thermal pumps gather the initial energy, mixing it with the ambient temperature and climate. In the federal state of North Rhine Westphalia the distribution and installation of such systems are supported with the help of: “Rational use of energy and installation of fully renewable energy systems.”
To realize the thermal energy of sub-surface geothermal systems, the following equipment is necessary:
Thermal pumps using heat from underground water springs:
Strategically chosen underground holes are bored to access the underground wells. This water is pumped up to the surface via the thermo pumps and returned to its origins with the help of a necessary water return.
Underground collectors:
At a depth of approximately 80-160cm, a horizontal system of plastic hoses is positioned as heat exchangers. As the circulating constant temperature liquid passes through the heat exchangers, its temperature is increased to the desired temperature to condition the medium.
Geothermal probes:
Vertical holes are bored into the Earth’s surface. Plastic tubes are then probed into these holes to depths of 30-100 meters, sometimes deeper. This method is most commonly used in Northern and Central Europe. The probes are connected to the thermal pumps, which either cool or heat the working fluid to the desired temperatures to condition the medium, whether it be; a house, office, commercial building, or a whole apartment building.
Energy cement elements in contact with the earth and energy posts:
Static elements and/or fundamental posts are positioned with underground walls to satisfy the energetic need. This system of heat exchangers and thermal pumps can be installed in newly built buildings to serve as the dwelling’s primary heating and cooling system.
Depth of geothermal technology
Depth of geothermal probes
Initially, geothermal probes were installed to depths beyond 500 m. At the beginning of the 1990’s, existing underground holes in Switzerland, which were used for the extraction of crude oil and natural gazes, were modified to accommodate the geothermal systems. In the city of Prenzlau (Brandenburg), there were geothermal systems setup in existing bored holes with depths of 3000 meters below the surface. The geothermal energy is collected and stored in the city’s central heat- supplying power station. A thermal pump, in the form of an intermittent heating element, is used to raise the temperature of the working fluid, in order to condition the air of the mediums in the network.
Current dwellings are being built in such a way that they require only a small amount of thermal energy to satisfy their air conditioning needs. The heating systems being installed resemble small cooling units. In North Rhine Westphalia a different system is being used. The water is heated in the depths of the earth, then the warmth probe delivers its energy over heat exchanger in the buildings. In the final step the cooled water returns to the Earth to warm up itself there once more and to repeat the circulation cycle.
Use of thermal water
In Germany, geothermal combined heat and power plant (CHP) are being dug to access underground wells. While digging to reach wells in the north German lowlands and south German Molassebecken, between the Danube river and the Alps, near the Swiss Alps, in the valleys of Upper Reigns, and in the region near Aachen city, there are many large known deposits. The temperature of the water in these wells averages between 40 and 100 ˚C. In some wells near the valleys of Upper Reign and Bavaria, there have been recorded temperatures of over 100 ˚C.
Warm or hot water is brought to the surface through bored holes, cooled to the desired temperature, then returned to the underground well through another bored hole to same well it was taken from. A hydraulic balance is created in these wells by not pumping out the reserve of thermal waters. The heat of the water is transferred to the medium it is meant to condition. The heat exchange is made possible by the use of two bored holes called geothermal doublers. The systems that are setup in Germany are installed to depths of 800 to 2500 meters below the Earth’s surface. Such geothermal CHPs provide a power of over 20 MW. This is sufficient to heat several thousands of dwellings.
Geothermal Electricity
Geothermal power plants can be found on every continent, mostly where there are underground fields of steam or hot water. With the help of conventional technology, these power plants work around the clock to provide energy. It is worth noting that this technology is not being used to its full potential. However, current day technology is broadening its possibilities.
In the past, areas where water temperatures were close to 100 ˚C, were not suitable for use to produce electric energy. The community living in the city of Altheim, in upper Austria, has been using the geothermal technology since the beginning of the year 2000. The city located in the northern Alps, was the first example of such a power generating plant. With the evolution of thermal turbines and the use of the Rankin cycle, it is now creating electro-energy with thermal waters of 106 ˚C.
Another step forward within Geothermal energy production comes a new type of electro-power plant. It is being created with the use of “Hot-Dry-Rock” (HDR-power plant). Although in Central Europe there are no underground reserves of steam or hot water, in Ukraine there are wells of satisfactory temperatures to install such systems. To access the required temperatures needed for this technology, deep holes must be bored.
To explain the process is quite simple: the hot rocky medium is accessed through bored holes under the Earth’s surface. Using hydraulic pumps, water is forced from the surface into the bored holes to create or add to existing sources. This acts as an underground heat exchanger that warms the water to the desired temperature, it is then pumped up to the surface and activates a turbine. The circulation of the HDR system is a pressurized closed circuit, which agitates boiling water, causing steam to propel the turbine.
The European team researching the HDR project in Soultz-Sous-Forêts, in the French region of the Upper Rhine (Alsace), was able to produce suitable results, proving the effectiveness of this technology as early as 1994-1997. Sault-Sous-Forêt was chosen as the control center for this project, even though the majority of the HDR technology is being used in Central Europe, where relatively shallow holes of 3500 to 5000 meters are drilled.
The Scientists of North Rhine Westphalia also started to take an interest in this technology and are currently the world’s leading European organization continuing to develop the HDR technology.
In support of this ongoing project, the Federal Government of Switzerland created the first HDR power plant in the region near the city of Basel.
Storage of warmth and coldness
Heat is not only obtained from the underground, it can also be stored underground and used when needed.
Existing geothermal wells:
The heat generated by the sun and accumulated by buildings in summer months can be stored underground, and later used for winter heating.
Models showing the effectiveness of this technology were created in North Rhine Westphalia in 1992. In downtown Düsseldorf, this geothermal technology is being used to heat and cool a building 6650 m2. In a given geothermal system, 77 holes were bored into four underground sources outputting 177.5 kW of energy.
Water reservoirs:
To use an underground water reserve without modifications, the water must be stagnant or have a negligible flow. This type of well was found and a geothermal system was setup in the German Reichstag. Warmth is stored in an underground well during the summer months and used in the winter to heat the building.
Providing safety to vehicle passengers when driving in dangerous weather conditions
In 1994, close to the European city of Derligen Am Tuerzee (Switzerland), the first system harnessing energy from the sun to heat highway pavement was created. This strip of highway had recorded many tragic accidents cause by slippery road conditions. A system of underground heat exchangers store heat from the sun in the summer months,when winter arrives, the heat exchnagers transfer heat to the pavement through viaducts lining the surface just below the road; therefore preventing such slippery conditions.
Comments
Da ich mich mit der Thematik Konvertierung von Geldwerten in Sachwerte befasse (Sicherung der Gelder meiner Kunden vor Entwertung) interessieren mich Beteiligungsmöglichkeiten in Geothermie. Gibt es hier börsenunabhängige Möglichkeiten? Wer kann mir da weiterhelfen?
Mit freundlichen Grüßen aus Fredersdorf bei Berlin
Jens Veit Günther
Auch ich bin an dem Thema sehr interessiert und werde mich innerhalb des nächsten halben Jahres stärker damit auseinandersetz ten. Die Grundidee ist die Kombination von Geothermie und einer effizienzgestei gerten Dampfmaschine zur Stromerzeugung, als Bürgerkraftwerk konzipiert, Beteiligungsmöglichkeit ab 50,- Euro. Über die konkrete Umsetzung werde ich, wie gesagt, erst demnächst grübeln. Vielleicht sollten wir uns mal deswegen kurzschließen, ob man da nicht gemeinsam was ausbrüten könnte?
Herzliche Grüße aus Hamburg,
Gunnar Kliewe