Overview
The U.S. military faces unusual challenges in securing energy for its in-theater operations and for its many installations. The cost of energy in a field operation often is many times the purchase price because of the logistics assets needed to move it there and the defense assets used to protect it (1, 2). That cost also is affected by the attrition of fuel, personnel and transport assets that result from enemy action. While power can be obtained from the U.S. grid for cents per kilowatt hour, its cost can rise to several dollars per kilowatt hour in a field operation, particularly one subject to relatively intense conflict. This suggests that alternative means of supplying power in a theater could be cost effective even though they would not necessarily be so elsewhere.
Separately, military installations generally derive electricity from local grids, but this makes them vulnerable to long-term disruption caused by accidents or willful acts. The Defense Science Board has recommended to the Department of Defense that it reduce its dependence on the grid at critical installations, both through more efficient use of energy and through development of local sources of energy supply (1).
Geothermal energy may offer potential to alleviate the first of these two problems, and in some instances can be used to address the second, particularly where known geothermal resources exist on military lands (3). Geothermal energy has the advantage that it can supply base load power as well as heat for ongoing operations. Also, a related form of underground energy, ground source heat pumps, offers an option for immediate military use. However, there are a number of technical challenges to more widespread use of geothermal energy, both for forward operations and at installations (4). The nature of these challenges and what might be done to address them will be described.
Methods
Under the sponsorship of the Defense Advanced Research Projects Agency (DARPA), a workshop to examine the potential for military geothermal energy use was held in March 2010. Session topics included the costs of conventional energy supplied the military and technical challenges to more widespread use of geothermal. The cost of conventional energy was estimated under varying conditions of conflict, from peacetime to medium intensity. Data from supplying energy to overseas locations ranging from Bosnia to Afghanistan was used for the estimates.
The sessions devoted to geothermal energy’s technical challenges focused on resource identification, drilling and production, and power plant construction. They also focused on means to curb logistics requirements, since delivery of logistics supplies to a theater of operations can be prohibitively expensive.
Challenges identified to the use of geothermal energy in theater included how to improve capability to: 1) detect geothermal potential remotely; 2) map reservoirs accurately; 3) drill quickly, and 4) produce power efficiently. Other discussion involved the supply of geothermal energy to military installations and in particular to Guam, to which a large number of military personnel will be moving and where geothermal potential may exist. Findings and analyses performed for the workshop will be described.
Results
The exploitation of geothermal energy by the military faces a number of serious challenges. In-theater forces require energy quickly and with certainty whereas geothermal can take time to develop and drilling success is uncertain. Better resource identification and more accurate reservoir mapping could reduce this uncertainty, though activities to do so may be di. fficult to accomplish in a theater. Remote sensing offers a possible means to address the task without subjecting geologists or others to undue danger.
U.S. forces must operate abroad with as few logistics as possible but geothermal drilling requires large amounts of materiel, including steel pipe, cement and fuel. Conventional geothermal technology therefore may not be appropriate in such circumstances. Ground source heat pumps, howver, may provide an attractive alternative. Though technically not a geothermal energy technology, this approach can be implemented quickly and with few logistic requirements. This technology also may be applicable at many installations, where it could measurably reduce requirements for grid-supplied power (5).
Installations also could benefit from more extensive worldwide mapping of geothermal resources and from more robust means of obtaining energy from these resources. As noted above, the U.S. military is particularly interested in whether the Pacific island of Guam offers geothermal potential. Mapping of this resource in that location is therefore a high priority objective. Enhanced geothermal systems (EGSs) offer a technical means to expand the scope of this energy source by utilizing less ideal geothermal resources to produce useful amounts of power. However, EGS is expensive and a number of technical challenges remain (6). The U.S. Department of Energy and the Department of Defense are investing in this technology and considerable stimulus funds have been allocated to its development.
Conclusions
Application of geothermal energy for use by military installations may be possible on Guam and elsewhere where there is volcanic activity. Successful development of enhanced geothermal system technology could much increase the geographic scope where the resource could be tapped. This would help the military overcome the challenge of reducing reliance on nearby power grids.
Despite the high cost of delivering conventional energy to U.S. military field operations, the use of geothermal energy for that purpose remains a more distant objective. However, further technological development to locate and extract geothermal energy and to reduce the logistics required for its production will enhance its potential both for military and for civilian use.
References
(1) Defense Science Board, Report of the Defense Science Board on DoD Energy Strategy, “More Fight—Less Fuel,” Washington, DC, February 2008.
(2) Defense Science Board Task Force on Improving Fuel Efficiency of Weapons Platforms, More Capable Warfighting Through Reduced Fuel Burden, Washington, DC, January 2001.
(3) A. E. Sabin, J.R. Unruh, J.D. Walker, F.W. Monastero, J. Lovekin, A. Robertson-Tait, H. Ross, M. Sorensen, R. Leong, C.T. Holte, C. Amos and D. Blackwell, “Geothermal Energy Resource Assessment on Military Lands,” Proceedings, 29th Workshop on Geothermal Reservoir Engineering, Stanford University, January, 2004.
(4) “The Future of Geothermal Energy: Impact of Enhanced Geothermal Systems on the United States in the 21st Century,” MIT, 2006.
(5) J. A. Shonder, P. J. Hughes, R. A. Gordon, and T. M. Giffin, Geothermal Heat Pump ESPC at Ft. Polk: Lessons Learned, Oak Ridge National Laboratory, July 1997.
(6) Y. Polsky, A.J. Mansure, Douglas Blankenship, Robert J. Swanson and Louis E. Capuano, Jr., “Enhanced Geothermal Systems Well Construction Technology Evaluation Synopsis,” Proceedings, 34th Workshop on Geothermal Reservoir Engineering, Stanford University, 2009.
Results
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Conclusions
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References
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