| Abstract |
In the USA, after more than 50 years of development, only about 0.33% of the country's total installed electrical capacity is currently being produced from geothermal resources and the growth rate of this environmentally "green" energy resource is overshadowed by that of wind and solar energy. However, most of the new geothermal developments in the USA involve only relatively small, moderate-temperature, geothermal systems. In contrast, development of higher enthalpy geothermal systems for power production has obvious advantages: specifically higher temperatures yield higher power outputs per well so that fewer wells are needed leading to a smaller environmental footprint for a given size of power plant. Unfortunately locations of suitable very high enthalpy geothermal systems are restricted to young volcanic terrains. Furthermore,, production of very high enthalpy fluids usually requires drilling deeper wells and may require enhanced geothermal (EGS) technology. Similarly drilling deep into hot hostile environments is technologically challenging. None-the-less, there is considerable undeveloped potential in the USA that could yield very favorable economic returns and this suggests that we should begin to develop such a program. One approach to mitigating the cost issue is to form a consortium of industry, government and academia to share the costs and broaden the scope an investigation. An excellent example of such a collaboration is the Iceland Deep Drilling Project (IDDP) which is investigating the economic feasibility of producing electricity from supercritical geothermal reservoirs. At Krafla in northeast Iceland the IDDP developed the world's hottest geothermal well, capable of generating more than 35 MWe from superheated steam at a well-head temperature of ~450°C. Plans for deep drilling to explore for much higher enthalpy, geothermal resources are also underway in the Taupo Volcanic Zone of New Zealand (Project HADES), and in northeast Japan the “Beyond Brittle Project” (Project JBBP) is an ambitious program attempting to create an EGS reservoir in ~500 C rocks. However, there is no comparable national program to develop such resources in the USA, in spite of the fact that there is significant undeveloped potential for developing high-enthalpy geothermal systems in the western USA, Hawaii and Alaska, both on and offshore. Forming a consortium to systematically explore, assess, and eventually develop such higher-enthalpy geothermal resources and to stimulate the necessary scientific and engineering investigations is a necessary first step. |