Conclusion

In some countries such as Iceland, Turkey, and the Philippines, geothermal energy makes up a significant portion of the national energy budget.  While, in theory, geothermal heat pumps can be used anywhere in the world,  the extent to which geothermal power plants or district heating systems can contribute to a given area varies by location and depends on the preexisting geothermal aquifers, dry steam fields, or subsurface heat flow in hot rocks three to ten kilometers underground.  Thorsteinsson notes that, “Unlike wind and solar where the resource can be measured relatively easily, in geothermal developments nothing is 100% certain about the resource until a well has been drilled and an economical flow of fluid/steam has been found” (Thorsteinsson 2008, 104).  Consequently district heating projects are risky, complex, and require high levels of initial capital investment.  This, combined with regulatory and informational barriers, makes it unlikely that district heating will contribute significantly to meeting the United States space heating needs in the near future.  Because of rate structures, district heating is well suited to large buildings of 50,000 square feet or more and institutional developments with multiple large buildings.  The high cost of retrofitting and connecting preexisting homes or small buildings make district heating economically impractical in many built-up areas despite the presence of geothermal resources.  New developments that incorporate district heating systems can be economically attractive and such developments are taking place in the Western United States.   

The use of geothermal heat pumps will continue to grow and an increase in qualified and experienced installers in underserved areas can lower costs.  The Friends Center case illustrates that ground source heat pumps can be utilized in dense urban settings and retrofit situations.   Even at this early stage in the development of deep standing-column geothermal projects in urban settings, economic benefits can be achieved within a reasonable timeframe for building owners planning on holding their building for the long-term.  This is especially true in the case of owners for whom environmental concerns outweigh financial motives. 

The presence of geothermal resources and their utilization can be important factors in creating a sense of place. The Earth’s geothermal heat content is enormous, 99% of the earth’s volume has temperatures greater than 1000°C, and only 0.1% of the volume is at temperatures less than 100°C  (Rybach 2007, 2).  Society is just beginning to tap the immense potential of the Earth’s heat to meet some of its energy needs.  Sustainable use of geothermal resources requires finding the appropriate level of production for the resources being tapped, which in turn is dependent on the field size, natural recharge rate, and other characteristics.  There are potential negative impacts: perhaps the most critical is the potential harm to aquatic environments if effluent is discharged into surface water bodies.  Most negative impacts can be minimized by the reinjection of geothermal fluids back into the reservoir.  Geothermal energy is both renewable and one of the cleanest sources of energy and its use has the potential to greatly reduce greenhouse gas emissions by displacing fossil fuels.