Currently, geothermal energy has been utilized on a wide scale in many areas worldwide, exclusively on land. This energy resource is regarded by many as the one of the most reliable, as well as one of the least exploited. For a long time, offshore geothermal resources have not been considered as a feasible solution. However, with current concerns over climate change, increasing energy prices, and limited and shrinking fossil fuel reserves, such an option becomes much more attractive.

Fig. 1. Schematic picture of an offshore geothermal resource with power cable and platform anchorages not included for simplicity. Source: Armani & Paltrinieri 2013

Offshore geothermal energy resources are in some ways superior to the onshore resources. For constructing an offshore geothermal power plant, it is not necessary to carry out a detailed visual environmental assessment and no land space is required. Also, offshore drilling is readily available technology which is extensively used within the petroleum industry. On the other hand, such energy resources would have been much more expensive than onshore resources and may cause disturbance to the wild sea life. Additionally, weather conditions (i.e. strong winds, high waves or extremely low temperatures) in some locations may be too extreme to operate offshore power plants.

Some of the potential options of using an offshore geothermal resource for power production may include:

1. Platform-based power plants where the geothermal steam goes through a pipeline from the seabed to the platform.
2. Land-based power plant separating the two-phase geothermal fluid at the seabed and then directing the pure steam onto land via pipeline.
3. Underwater power plant producing electricity and transporting it to land.
4. The binary power plant on land which uses a heat exchanger located at the seabed heating circulating working fluid.
5. A pipeline connected to a thermoelectric device using the temperature difference between the geothermal fluid and the ocean.

A couple of recent research projects have started to investigate the possibility of utilizing offshore geothermal energy. These are the Marsili project in Italy, where the goal was to extract the steam from the underwater volcano to produce electricity as well as hydrothermal vent project in the Gulf of California where the potential use of a submarine with a binary station built inside was investigated. Recently, significant interest is seen in exploiting such resources on the Icelandic waters mainly on the Reykjanes ridge and on the Island of Grimsey.

Fig. 2. Volcanic system of Iceland (source: Wikimedia commons)

As we anticipate this subject to capture a lot of interest, we intend to provide an update on any off-shore geothermal projects in the future.  This concludes our first #GeothermalFactsandStats blog post on the potential of geothermal resource development offshore. For more interesting posts on a wide variety of topics, scroll through our blog or follow us on all the major social media platforms.

Guest Author: Michal Kruszewski

References:

1. Armani F.B., Paltrinieri D., Perspectives of offshore geothermal energy in Italy, EPJ Web of Conferences, Volume 54, New Strategies for Energy Generation, Conversion and Storage, 2013.
2. 2012. “Marsili Project.” Retrieved (http://www.eurobuilding.it/marsiliproject/index.php?option=com_content&view=article &id=54&Itemid=61).
3. Hiriart G., Prol-Ledesma R. M., Alcocer S., Espíndola G., Submarine geothermics: Hydrothermal vents and electricity generation, Proceedings World Geothermal Congress, Bali, Indonesia, 25-29 April 2010.
4. Karason B., Gudjonsdottir M.S., Valdimarsson P., Thorolfsson G., Utilization of Offshore Geothermal Resources for Power Production, Proceedings, Thirty-Eighth Workshop on Geothermal Reservoir Engineering Stanford University, Stanford, California, February 11-13, SGP-TR-198, 2013.

INTERESTING BLOG POSTS:

Geothermal Surface Exploration

Seismic While Drilling

Small Scale Geothermal Developments – Agriculture