Innovators in Geosciences Series

New Technologies Make Geothermal Solutions Cost-Effective: Interview with Carlo Dietl

American Association of Petroleum Geologists (AAPG)

Geothermal energy from lower temperature (low enthalpy) sources is an increasingly important source of renewable, sustainable energy. Welcome to an interview with Carlo Dietl, who works with both low and high enthalpy geothermal energy sources, and who discusses some of the recent breakthroughs in technology used in geothermal energy.

What is your name and your background?

I’m Carlo Dietl. From my education I am a structural geologist and petrologist. Since 2012 I’m working with Gesteinslabor Dr. Eberhard Jahns in Germany. We offer rock physical and geomechanical services mainly for the oil and gas / geothermal industry, but also for construction and tunneling companies. More information about our activities can be found on our homepage.

How did you first get involved in geothermal resources?

When the last oil (price) crisis started in 2014, we recognized at Gesteinslabor that we have to broaden our scope. That is when we first got interested in geothermal resources. And basically, working with geothermal reservoirs is very similar to working with hydrocarbon reservoirs. Many techniques and needs are the same, only that hot water is the carrier of energy instead of hydrocarbons. We then did some geomechanical investigations (elasticity, strength and stress in 3D) and thermal modelling for the Franconian Basin in SE Germany. However, we discovered soon, that we have to offer also projecting services besides field geology, rock physics and modelling and started working on a geothermal project in our hometown Heiligenstadt, as well as in Nicaragua (together with our Nicaraguan partner COINGELSA) and in Columbia (together with the Columbian Geothermal Association AGEOCOL).

What is the current state of geothermal activity in Europe?

Of course, there is Iceland, but since it is in the midst of the Atlantic Ocean and situated on oceanic crust I would like to leave it out there.

On continental Europe there are currently two main growing markets for geothermal energy: Italy and Germany. In Italy high enthalpy geothermal energy (above 150°C reservoir temperature) is growing with some 900 MWs (power generation) installed and 1000 MWe anticipated for 2020. Most plants are installed in Tuscany. There 30% of the electric power supply comes from geothermal energy already nowadays.

In Germany the southernmost federal state Bavaria can be regarded as trailblazer in low enthalpy geothermal energy (lower than 150°C reservoir temperature). In particular Munich, the capital of Bavaria, can be regarded as the hot spot in terms of geothermal projects in Germany intended mainly for heat production. The administration of Munich plans to base the entire heat supply of the city until 2040 on geothermal energy.

These two examples - Tuscany and Munich - show that geothermal energy has a high potential also in (continental) Europe. However, when we look at the absolute number of activities in relation to fossil fuels, nuclear power and even other regenerative energy carriers such as solar, wind and hydropower, geothermal energy still is at the very margin. A critical issue is that we have to deal with a lack of acceptance in the public. In particular deep seated, petrothermal EGS (enhanced geothermal systems) projects face resistance of the public for the necessity of fracking and the fear of earthquake activity. And of course there are examples for failed geothermal wellbores which ended up in seismic activity such as Basel (Switzerland) or Landau (Germany), both situated within the Rhine Graben, which in general is a favorable area for geothermal projects.

Why are people and governments pursuing geothermal energy in Europe?

In fact, geothermal energy could be pursued much more. This is in particular true for deep geothermal projects (deeper than 400 m). What is a pity: geothermal energy is the only base load capable regenerative energy source! Main reason for the reluctance is the above mentioned “fracking fear” which for example even led to a general fracking ban in Germany. Moreover, and funny enough, geothermal energy is competing with other regenerative energies. Many politicians and managers of municipal utilities only promote one regenerative energy source instead of looking for a combination of several options. We made this experience in Heiligenstadt where public services recently installed a biogas plant and now do not show any interest in geothermal energy. The high costs of drilling very often also discourage public authorities to start geothermal projects. Whenever deep geothermal and petrothermal projects are pursuit in Germany, the main motivation is the so-called “Energiewende” due to the shutdown of all German nuclear power plants until 2020 and the efforts to reduce the emission of CO2 fighting against climate change.

The situation is different when talking about superficial geothermal energy, e.g. for private houses or the storage of waste heat from computer server installations etc. in superficial aquifers. This is an important business field and of the 13.6 TWh produced in Germany 12.4 TWh stem from near-surface geothermal energy.

Please describe the geothermal energy potential in Nicaragua.

Nicaragua, for being such a small country, has a huge potential. We estimate a potential of 1100 MW only for power generation. So far (until 2014, actually), only a small part of this treasure has been unearthed. There exists a geothermal master plan developed by the government of the country which identifies ten areas of high geothermal potential. Until today, only in two of them power plants have been constructed: Momotombo (N of Lake Xolotlán) with 77 MWe (electrical power) and San Jacinto-Tizate (approx. 50 km NW of Momotombo) with 82 MWe. The people of COINGELSA and we at Gesteinslabor think, that the El Hoyo volcano 25 km ENE of the city of Leon, is a very attractive area for a geothermal project: the geothermal gradient there is up to 1°C/m!

What are some of the new technologies that are making the use of geothermal energy more economically viable?

There are nowadays several types of flash plants available which allow for a higher efficiency and power output of individual geothermal reservoirs. Moreover, new drilling technologies adopted from the oil and gas industry and developed for the production from unconventional reservoirs of course have helped in cutting costs for geothermal projects. We also have learned to apply numerical models for better forecasting depletion rates of geothermal reservoirs. This leads to an increased longevity of individual geothermal systems and makes them economically more valuable.When considering low enthalpy and near-surface geothermal systems, new developments in the field of heat pumps and district heating systems make geothermal heat an attractive energy source in this area. Additionally, the improvements with respect to ORC (Organic Rankine Cycle) and Kalina processes allow nowadays for economically viable binary geothermal power plants based on low enthalpy geothermal energy sources.

What do you see as likely developments in the future in the area of geothermal energy?

Supercritical fluids will hopefully become an important and very powerful geothermal energy source. Although still risky to produce, the progress made in particular on Iceland is tremendous.

District heating based on geothermal energy will become more and more important in the future in the northern hemisphere. To make this possible, we have to learn and accept that geothermal energy is not only useful for power production, but in first place for heating. There is a huge amount of low enthalpy geothermal fields around the globe. Think about all the old oil and gas fields which still can serve as geothermal reservoirs.

Finally, we all should learn to see our planet itself as the most powerful and natural energy source, which offers heat and power basically for free. So why not accepting with open arms this fantastic gift?!

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