Geothermal – The Unknown Energy Under Our Feet

Utilization of Geothermal Energy – from the Romans to the Present


by Dr. Jörg Baumgärtner, former Socomine, Soultz-sous-Forêts, Alsace (1994)


The squeaking of primitive wooden winches drowns even the faraway noise of the fizzling steam. The smell of sulfur fills the air. Sweat is pouring from the faces of the two men standing by the drill. Out of breath, they are trying to pull up the heavy drill with the help of a wooden spindle.

prinz_monti1904 - Count Piero Ginori Conti devised the first geothermal energy plant in Larderello, Italy. (Geothermal Education Office)Around 1850, in Tuscany, Italy, geothermal energy is still recovered with such comparatively primitive means as hot temperature water and steam. Above the well site, a ten to twelve meter tall wooden tower has been erected. The drill string is rotated manually and laboriously driven into the ground. Two additional men operate the cable winch attached to the drill. By means of this rather simple technology, drilling depths of up to twenty meters were reached. It was in Tuscany, where, only a few years ago, the industrial utilization of the locally abundant geothermal energy began. But this is only a recent development, since the exploitation of geothermal resources began much earlier.

Tuscany is situated in a region in Western Italy where the earth crust was ruptured in the collision of two larger tectonic plates, the Eurasian and African continental plates. In these rupture zones, hot and liquid rock advanced to the surface. The subsequent heating of the underground also reached the groundwater carrying layers, creating “Lagones” (natural hot water springs) and “Soffiones” (natural hot water outlets, geysers). Already 600 years BC, Etruscan artists used the boric acid that accumulated on hot water springs for the beautiful enamel decorations of their vases. Half a millennium later, the highly developed bath culture and housing of the Romans lead to the first use of geothermal energy. In Tuscany and in other places in their empire, Romans began to heat their baths and living quarters with the water of warm springs (even in some regions of present-day Germany, such as the Lower Rhine). Only little of this civilization has been conserved. Reports of natural disasters and drawings of the Roman thermal springs in Tuscany have been preserved in the “Table of Peuting,” a kind of Roman map dating back to the third century AD. Nevertheless, the descriptions on the table are detailed enough to identify a number of these famous and still existent thermal springs. With the demise and the subsequent repartition of the Roman Empire, however, this elaborate culture had come to an end.

Geothermal resources and their exploitation were of little importance until the early Middle Ages, when they became economically and culturally significant. Again, this development started out in Tuscany. Sulfur, vitriol and alum were recovered from the Tuscan “Lugones” and “Soffiones.” Henceforward, the considerable economic worth of these reservoirs led to repeated wars between the different Tuscan republics. Nevertheless, their industrial exploitation only began in 1702, when Franz Hubert Hoefer, head of the state board of pharmacies in the grand duchy of Tuscany, discovered boric acid in the local “Lagones,” a medicinal product which has since been known as “Sedative Salt of Homberg.” After that, it should take over a century until in 1812 an extraction method for the ‘industrial’ recovery of boric acid had been developed. In a rather cumbersome process, the boric solvent was first collected from the “Lagones” to be vaporized in heated iron vessels, and later crystalized in wooden barrels. In 1827, the French engineer François Larderel had the decisive idea to accelerate this process. The firewood formerly used to vaporize the boric solvent was initially substituted with superheated steam generated in the Soffiones, and later replaced by the geothermal vapor recovered from the boreholes. This was the beginning of a flourishing chemical industry that owed its success to the consistent exploitation of naturally abundant superheated steam, and which lasted until the onset of World War II.

larderello_2_1931    1931 – Exploitation of the fumarole "Soffionissimo" (rock storage basin) in Larderello, Italy (ENEL).


The abundance and accessibility of hot water steam as well as the rapid industrialization of the late 19th century, led rather early to a subsequent utilization of geothermal energy in Italy, particularly for power generation. Already in 1904, Duke Piero Genori Conti used a steam-powered dynamo to illuminate light bulbs. In 1913, Conti (by then director general of the local boric-acid factories) installed the first geothermal energy plant, with an output of 250 kW. Unfortunately, and despite its promising beginnings, geothermal energy production in Tuscany was moderate during the first years and only gained importance in the mid-1930s, when power generation became a permanent fixture in the area. Today, the “Direzione Attitiva Geothermische” of ENEL (national Italian electricity supplier) has an electrical output capacity of more than 630 MW, electricity which is solely generated by geothermal energy (steam and hot water). Modern geothermal energy plants in Italy are based on standardized and particularly environmentally friendly generating units of 20 MW(e) and 60 MW(e), each equipped with several water supply and re-injection bores. In this way, the various standardized thermal power units can be differently combined with one another when necessary. An additional advantage of these plants is that both the generating units as well as the connected supply bores do not require operating personnel, which means that several units at different sites can be remote-operated from one central control station. Depending on the depth of a particular reservoir, the number of supply bores and the age of the respective plant, the costs of geothermal energy production vary between 2, 5 and 7 pfennigs per kW (and between 21 and 56 Lira, all data based on base load plants, average fix costs and variable costs in 1992). Currently, investigations are under way to develop deeper steam reservoirs (at 3000 -5000 meters depth) for energy production, and to replace older plants of the 1950s and 60s with modern ones. (Note: By act of parliament, Italy completely abandoned the option of nuclear energy.)


Beyond Italy


Geothermal energy is being used broadly across Europe, however only in places where underground water reservoirs are large enough to be used as geothermal carrier. These underground water formations are also known as aquifers, which are generally classified as low temperature (25-40 °C), hot water (40 – 100°C) or high temperature and steam (> 100°C). The geothermal formations in Italy described above are exclusively high temperature and steam reservoirs, with temperatures well above 300°C in depths of 3000 to 4000 meters. Nevertheless, low-temperature and hot water deposits can still be valuable resources for heating, for instance, as process heat in drying plants, in thermal baths, greenhouses and as service water. In Iceland, for example, geothermal water has been used in greenhouses since 1888, and a geothermal heating system has serviced large parts of the country’s capital Reykjavík since 1928. It is in France, however, where geothermal energy is used in an exemplary manner for heating purposes. 66 plants have been installed so far, and 54 for of them in the basin of Paris alone. The total investment sum amounted to roughly 6 billion D-mark. At the moment, these 66 plants supply heat to about 200,000 individual units. For environmental reasons, all these geothermal doublet plants are based on a closed-cycle process in which the geothermal fluid is completely pumped back into the underground formation through a second bore installed at a distance from the production well.


A second very interesting example for meaningful utilization of geothermal energy in Europe is Switzerland, because it shows how a country’s economic conditions can positively influence a growing market. Even though at first sight, Switzerland is not abundant in geothermal resources (no volcanic activity, no geothermal anomalies), the introduction of more and more stringent environmental regulations led the government to grant no-risk guarantees (a unique measure in Europe) for geothermal exploration, with the intention of providing funding for a small but very active high-tech industry that focuses solely on low-temperature and hot water aquifers. These state guarantees insure technical and geological drilling risks (in case no reservoir is found) and cover at least 50 percent of the drilling expenses, in individual cases up to 80 percent. In Switzerland, two geothermal extraction methods apply: the development of hot water-bearing layers (about 100°C) in depths of 3000 meters, mainly used for large-scale heating projects, and shallow-drilling (also known as borehole heat-exchangers), for deposits lying close to the surface in depths of up to 150 meters. In this second method, cold water is pumped into a single tube heat-exchanger, and heated to a temperature of 10 to 12 °C. A heat-pump further increases the temperature up to 50°C, high enough for low-temperature heating. In 1988, at least 1,500 of these units had been installed. Compared to customary oil-heating, in 1988, these geothermal heating systems paid off within a period of 15 years (based on a price of 100 Swiss franc per meter drilled), not considering the environmental advantage of this method.




Germany has only been moderately active in geothermal power generation as the country does not dispose of truly profitable geothermal reservoirs. Elevated underground temperatures have been regionally observed in the Upper Rhine Graben, in certain areas of the Swabian Mountains, in the southern Molasse Basin and in some sedimentary rock formation in Northern Germany. Given the country’s economic conditions, geothermal energy in Germany is mainly used in thermal baths in Lower Bavaria (Füssing/Birnbach/Griesbach) and the Rhine rift (Baden-Baden). Only in the former GDR, serious attempts were made to use geothermal energy for larger heating systems, efforts which were primarily driven by the need to secure the country’s energy supply. In the cities of Neubrandenburg, Waren and Prenzlau, three geothermal district heating units were installed, each with a (thermal) capacity of roughly 22 megawatts, which operated – like the French plants – on a closed-cycle doublet system. Following Germany’s reunification, these East-German plants played a decisive role in initiating research projects on low-temperature and hot-water reservoirs in Germany. Last September, initial planning for a modern combined heat and power plant began in Neustadt-Glewe, about 25 kilometers to the South of Schwerin (a geothermal heating system with one block-heating station). Planning foresees heat supply for a residential area, including space heating and hot water, as well as process heat for a nearby industrial district. While the planned capacity of this plant is 12 megawatt, 6.5 megawatts will be generated by geothermal energy alone. Fifty percent of this project, with a total investment of 18 million D-mark, is being funded by the federal ministry for Research and Technology in Mecklenburg-West Pomerania. A fixed price of 85 D-mark per MWH has been proposed.


Outside of Europe


There are, of course, other regions near the tectonic interfaces of our globe, that offer similar or more favorable conditions for the use of geothermal energy as does, for instance, Italy. The United States of America, the Philippines, Mexico, Japan and New Zealand are particularly prominent examples in this regard. KrokodileGeothermal alligator farm in Idaho, USA. (Geothermal Education Office)All of these countries possess natural hot water resources that are used directly for power generation. The order, in which the countries are listed, corresponds to the amount of electrical power they generate (1990). In 1992, “The Geysers”, a steam field situated in the Western United States, about 120 km to the northwest of San Francisco, already produced 2,979 MW of electricity. These plants are operated by several private companies and provide energy for the highly technologized region of San Francisco. Nevertheless, fierce competition between the individual operators led to a long period of unmonitored exploitation of the steam field (mainly due to the reinjection of process water and uncontrolled heat loss). Only in recent years, and after federal intervention, a cooperation agreement was reached between the different operating companies. Japan, which does not possess any natural resources, is planning on a drastic upgrading of its geothermal power plants (270 MW already installed in 1992, and 456 MW are planned for 1995). A major obstacle in this process is, however, the fact that a large part of these geothermal deposits is located in national parks and Japanese law does not allow drilling and construction in these areas. As a consequence, time and money had to be spent on directional boreholes, a laborious and expensive process which requires long distance drilling from a location outside of the parks to reach the fringe of these reservoirs. Worldwide, more than 200 geothermal energy plants have been installed, with a combined wattage of more than 6,200 MW. Currently, the annual increase rate is at almost 10 percent.


Is that all?


From the perspective of geothermal science, this question has to be answered with a clear ‘no’. The recent developments in the use of geothermal energy in the different countries described above show all known aspects and problems in this regard. In comparison to the advanced exploitation of other natural resources, however, only a small fraction of the geothermal reservoirs worldwide has been tapped into.


There are a number of reasons that contributed to this situation. First, development is generally dependent on the given economic and legal frameworks as well as the local cost structures in a country, and less determined by geological conditions. The word ‘deposit’ already indicates a general problem that applies to all natural resources. Deposits have to be located and their development always implies exploration risks, particularly during the initial prospecting of a region. The cost of drilling, which may, in individual cases, go into the millions, is an important aspect, especially when facing a limited profit margin. National insurance programs, as provided by the Swiss government, can balance some of these risks. Nevertheless, due to the comparatively high initial investments required in geothermal extraction projects (for drilling and the installation of the plants), there are generally only two cost determinants – which are almost entirely independent of the underground conditions:

  • the interest rates to which the capital is tied, and
  • the interval between the first drilling and the generation of energy, that is, the period during which the invested capital is unproductive

In addition, what has to be considered in this context is the fact that geothermal extraction projects always have to compete with the cost structures of a market that is dominated by powerful oil and gas industries, whose profit margin is generally much higher than that of alternative energy producers. Only an oversupply of raw oil on the world market led in recent years to a cost reduction and even to decreasing costs. Naturally, this oversupply of raw oil also resulted in extremely low oil prices. At first sight, then, the burning of oil seems currently and in our region at least, a much more economically efficient method of energy production than the use of geothermal resources. This perspective does, however, have its drawbacks. The oil price is, to begin with, also a politically determined price, which is subject to considerable fluctuations. The political instability in North Africa and the Middle East makes it difficult even for experts to predict long-term trends on the market. Investments in energy plants and heating systems are, however, always long-term and require anticipatory planning. Another factor in this equation is the legitimate interest of a country in securing its energy supply. Strong fluctuation in the oil price can have dramatic consequences for an economy, of which the oil crises of 1979 gave us ample proof. In contrast, geothermal energy is a local resource that is always to our disposal, independent of the weather or the time of day. Also, when used appropriately, geothermal energy is always environmentally friendly. A closed-cycle geothermal power plant is non-polluting and free of emissions (see ozone depletion, forest dieback).


To invest in meaningful and systematic geothermal energy projects means, therefore, to invest in our future and the future of our children. But how can we expedite the use of geothermal energy? As with other mining technologies, initially, development has always focused on deposits that were easily available and accessible. Meanwhile, due to enhanced information and more advanced technologies, it was possible to drill into low-lying and hotter areas, which are energetically more efficient. A hindrance in this process has been the dependence on nearby water reservoirs in the underground, so that the possibility of geothermal energy was limited from the beginning to a few regions only, which meet the geological requirements for geothermal extraction. The much larger amount of hot but ‘dry’ formations has therefore been left untouched. Ironically, it was physicists at the “Los Alamos Scientific Laboratory,” a nuclear research center in the United States, who, in the early seventies, first came up with a concept for using the geothermal energy stored in hot and dry rock formations (“Hot Dry Rock”). The development of this technology, its setbacks, achievements and its prospects for the future will be the focus of the last article in this short series.


Works Cited


Rummel, F. & Kappelmeyer, O. (1993): "Erdwärme, Energieträger der Zukunft? Fakten, Forschung, Zukunft", Verlag C. F. Müller, Karlsruhe  

Weber, R. (1990): "Heizwärme aus der Tiefe", Olynthus Verlag, Oberbözberg, Schweiz

Allegrini, G. & Capetti, G. (1990): "Economic Analysis of Geothermal Projects", G.R.C. Transactions, vol. 14, part I