Enhanced Geothermal Systems Ali Yasir Stuart School of Business
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TABLE OF CONTENTS

SECTION 1: SYNOPSIS Scope EGS, a viable option SECTION 2: INTRODUCTION Overview of the Process Basic concept Process Optimization SECTION 3: RESOURCE-BASE IN THE U.S What the facts say? Heat Content SECTION 4: ECONOMICS Potential Cost of Development Levelized Cost of Electricity SECTION 5: EMISSION REDUCTION POTENTIAL Summary of Regulations Potential Environmental Impacts Summary of Environmental Benefits SECTION 6: CURRENT DEVELOPMENTS & GOING FORWARD EGS Worldwide EGS Development in the U.S Obstacles to Further Development in the U.S Policy Options to help promote EGS SECTION 7: CONCLUSION REFERENCES

4 5 6 7 8 9 10 11 12 14 15 16 17 19 20 20 21 23 24 25 26 27 28 30

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PREFACE
There is a pre-dominating energy crisis in the United States, as the country is currently relying on a finite supply of fossil fuels. This energy crisis, along with economic growth and environmental stability must be sustained by developing alternative, renewable energy sources. Population is expanding at a geometric rate and each doubling will increase energy demand that will far exceed supply. China and India have recently developed into industrialized nations and several more will follow. Many leading scientists describe the “tipping point” for carbon dioxide emissions as having already passed, meaning it could be too late for renewable energy options to have an impact (McKibben, 2008). However, until the full impact is determined, scientists worldwide should be developing energy alternatives, in order to help stabilize the environment, secure national policy interests and boost to the economy. One such option that is often ignored is Geothermal Energy, produced from both conventional hydrothermal and Enhanced (or engineered) Geothermal Systems (EGS). Geothermal energy represents a sizeable, renewable power source and is one of several alternative energy options that should be utilized. In order for this technology to be able to move forward with any success, it must achieve the highest efficiency, through smart thinking and conservation methods. Society needs to integrate energy, environmental, economic and political policies; otherwise, there is no chance for a sustainable future. This paper discusses the important aspects of Enhanced Geothermal Systems with respect to both its operation and resource base capacities for operation in the United States. A study by MIT calculated the world's total EGS resources to be over 13,000 ZJ. Of these, over 200 ZJ would be extractable, with the potential to increase this to over 2,000 ZJ with technology improvements; sufficient to provide all the world's present energy needs for several millennia. The paper also discusses the need for EGS and advantages over the conventional geothermal techniques. The key characteristic of an EGS is that it reaches down into hard rock to extract the energy stored there. To extract this energy requires engineering a reservoir at depths between 2.5 and 10 kilometers which was not possible with conventional geothermal technologies. In the context of the study, EGS technology will be analyzed in terms of energy potential, economics and environmental benefits plus the barriers and future challenges that it could face.

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1
SYNOPSIS

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Scope
There are several compelling reasons why United States should be concerned about the security of its energy supply for the long term. With the increasing U.S. population, along with increased electrification of our society, U.S. nameplate generating capacity has increased more than 40% in the past 10 years and is now more than 1 TWe according to the Energy Information Administration (EIA 2006). Retirement of Existing Capacity In addition, the electricity supply system is threatened with losing existing capacity in the near term, as a result of retirement of existing nuclear and coal fired generating plants (EIA, 2006). It is likely that 50 GWe or more of coal-fired capacity will need to be retired in the next 15 to 25 years because of environmental concerns. In addition, during that period, 40 GWe or more of nuclear capacity will be beyond even the most generous relicensing procedures and will have to be decommissioned. Are non-renewables the reliable option? It is clear that demand and prices for cleaner natural gas will escalate substantially during the next 25 years, making it difficult to reach gas-fired capacity. Large increases in imported gas will be needed to meet growing demand. Second, local, regional, and global environmental impacts associated with increased coal use will most likely require a transition to clean-coal power generation, possibly with sequestration of carbon dioxide. The costs and uncertainties associated with such a transition are daunting. It is also uncertain whether the American public is ready to embrace increasing nuclear power capacity, which would require siting and constructing many new reactor systems. Switching to Renewables The U.S. hydropower potential could be expanded using existing dams and impoundments but its growth has been hampered by reductions in capacity imposed by the Federal Energy Regulatory Commission (FERC), as a result of environmental concerns. Concentrating solar power (CSP) provides an option for increased base-load capacity in the Southwest where demand is growing. Solar and wind energy are likely to be deployed in increasing amounts but they are inherently intermittent and cannot provide 24-hour-a-day base load without megasized energy storage systems, which traditionally are costly to deploy. Biomass also can be used as a renewable fuel to provide electricity using existing technology, but

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its value to the United States as a feedstock for biofuels for transportation may be much higher, given the current goals of reducing U.S. demand for imported oil.

EGS, a viable option
Could U.S.-based geothermal energy provide a viable option for providing large amounts of generating capacity when it is needed? This is exactly the question being addressed in the paper. It is noticeable that geothermal energy is often ignored in national projections of evolving U.S. energy supply which could be a result of the widespread perception that the total geothermal resource is often associated with identified high-grade, hydrothermal systems that are too few and too limited in their distribution in the United States to make a long-term, major impact at a national level. This perception has led to undervaluing the long-term potential of geothermal energy by missing an opportunity to develop technologies for sustainable heat mining from large volumes of accessible hot rock anywhere in the United States. Many attributes of geothermal energy, namely its widespread distribution, baseload dispatchability without storage, small footprint, and low emissions, are desirable for reaching a sustainable energy future for the U.S. Expanding our energy supply portfolio to include more indigenous and renewable resources is a sound approach that will increase energy security in a manner that parallels the diversification ideals that have made America strong. Geothermal energy provides a robust, long-lasting option with attributes that would complement other important contributions from clean coal, nuclear, solar, wind, hydropower, and biomass.

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2
INTRODUCTION

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Overview of the Process
The term Enhanced Geothermal Systems (EGS), also known as Engineered Geothermal Systems (formerly hot dry rock geothermal), refers to a variety of engineering techniques used to artificially create hydrothermal resources (underground steam and hot water) that can be used to generate electricity. Traditional geothermal plants exploit naturally occurring hydrothermal reservoirs and are limited by the size and location of such natural reservoirs.EGS reduces these constraints by allowing for the creation of hydrothermal reservoirs in deep, hot geological formations, where energy production had not been economical due to a lack of fluid or permeability. EGS techniques can also extend the lifespan of naturally occurring hydrothermal resources. EGS concepts would recover thermal energy contained in subsurface rocks by creating or accessing a system of open, connected fractures through which water can be circulated down injection wells, heated by contact with the rocks, and returned to the surface in production wells to form a closed loop (Figure 1). The idea itself is a simple extrapolation that emulates naturally occurring hydrothermal circulation systems – those now producing electricity and heat for direct application commercially in some 71 countries worldwide.

Figure 1: Schematic of a conceptual two-well Enhanced Geothermal System in hot rock in a low-permeability crystalline basement formation
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Basic Concept
Step1: Injection Well An injection well is drilled into hot basement rock that has limited permeability and fluid content. All of this activity occurs considerably below water tables, and depths greater than 5000 feet. This particular type of geothermal reservoir represents an enormous potential energy source. Step 2: Injecting Water Water is injected at sufficient pressure to ensure fracturing, or open existing fractures within the developing reservoir and hot basement rock. Step 3: Hydro-fracture Pumping of water is continued to extend fractures and re-open old fractures some distance from the injection wellbore and throughout the developing reservoir and hot basement rock. This is a crucial step in the EGS process. Step 4: Production Well A production well is drilled with the intent to intersect the stimulated fracture system created in the previous step, and circulate water to extract the heat from the hot basement rock with improved permeability. Step 5: Increasing Extraction Volume Additional production wells are drilled to extract heat from large volumes of hot basement rock to meet power generation requirements. Now a previously unused but large energy resource is available for clean, geothermal power generation.

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Process Optimization
In principle, conduction-dominated EGS systems in low-permeability sediments and basement rock are available all across the United States. The first step would be exploration to identify and characterize the best candidate sites for exploitation. Holes then would be drilled deep enough to encounter useful rock temperature to further verify and quantify the specific resource at relevant depths for exploitation. If low-permeability rock is encountered, it would be stimulated hydraulically to produce a large-volume reservoir for heat extraction and suitably connected to an injection production well system. If rock of sufficient natural permeability is encountered in a confined geometry, techniques similar to water-flooding or steamdrive employed for oil recovery might be used effectively for heat mining (Tester and Smith, 1977; Bodvarsson and Hanson, 1977). Other approaches for heat extraction employing down-hole heat exchangers or pumps, or alternating injection and production (huff-puff) methods, have also been proposed. The widespread application of EGS, however, will ultimately depend on advances in drilling technology. While oil and gas drilling techniques apply to geothermal drilling (both traditional and EGS), temperatures above 250°F that are necessary for geothermal reservoirs complicate the process. The high heat increases the probability of well failure due to collapse, mechanical malfunction, loss of telemetry, and casing failure. These limitations apply doubly to EGS wells, as EGS drilling requires drilling deeper, into harder and hotter rock than traditional geothermal plants.

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3
RESOURCE-BASE IN U.S

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What the facts say?
Given the costs and limited full-scale system research to date, EGS remains in its infancy, with only research and pilot projects existing around the world and no commercial-scale EGS plants to date. One MIT study projected that EGS could reach an installed capacity of 100,000 MW in the United States by 2050—for comparison the United States currently has roughly 319,000 MW of coal-fueled generating net summer capacity. Were the United States to realize a significant fraction of this potential, it would make EGS one of the most important renewable energy technologies. According to the U.S. Geologic Survey, the western United States has sufficient geological resources for over 517,800 MW of EGS capacities—roughly the equivalent of half the current total U.S. installed electric generating capacity from all energy sources. Nonetheless, the technologies needed to utilize this energy reserve are not yet commercially viable. According to the MIT report, realizing the theoretical potential of EGS will require consistent investment in research and development for up to 15 years before commercial viability and deployment are achieved. Figure 2 illustrates this by showing temperatures at a depth of 10 km. Figure 3 shows the heat flow of the conterminous United States where one easily sees that the western region of the country has higher heat flow than the eastern part. This fact leads to substantial regional differences in rock temperature as a function of depth.

Figure 2: Temperatures at a depth of 10km
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Figure 3: Heat Flow map of the conterminous United States

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Heat Content
Although the EGS resource base is huge, it is not evenly distributed. Temperatures of more than 150°C at depths of less than 6 km are more common in the active tectonic regions of the western conterminous United States, but by no means are confined to those areas. The highest temperature regions represent areas of favorable configurations of high heat flow, low thermal conductivity, plus favorable local situations. For example, there are high heat-flow areas in the eastern United States where the crustal radioactivity is high, such as the White Mountains in New Hampshire and northern Illinois. However, the thermal conductivity in these areas is also high, so the crustal temperatures are not as high as areas with the same heat flow and low thermal conductivity, such as coastal plain areas or a Cenozoic basin in Nevada. The most favorable resource areas (e.g., the Southern Rocky Mountains) have a high tectonic component of heat flow, high crustal radioactivity, areas of low thermal conductivity (as in young sedimentary basins), and other favorable circumstances such as young volcanic activity. There are also areas of low average gradient in both the eastern and western United States. In the tectonically active western United States, the areas of active or young subduction have generally low heat flow and low gradients. For example, areas in the western Sierra Nevada foothills and in the eastern part of the Great Valley of California are as cold as any area on the continent (Blackwell et al., 1991). The histogram in Figure 4 shows that there is a tremendous resource base of approximately 13 million EJ, between the depths of 3.5 to 7.5 km in the temperature range of 150°C to 250°C. Even if only 2% of the resource were to be developed, the thermal energy recovered would be 260,000 EJ. This amount is roughly 2,600 times the annual consumption of primary energy in the United States in 2006.

Figure 4: Histograms of heat content in EJ, as function of depth for 1 km slices
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4
ECONOMICS

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Potential Cost of Development
To evaluate the potential cost of developing geothermal resources, a number of factors must be considered. These include the cost of:  Drilling  Capital equipment  Other related costs Cost of Drilling It is estimated that the cost of drilling the wells necessary to operate a lower-grade EGS project can account for 60 percent of total capital investments, if not more (MIT 2006). Estimating drilling costs in the United States in general is made more difficult because in recent years, there have been fewer than 100 geothermal wells drilled per year in the United States and very few of them are deeper than 2,800 m (9,000 ft), which provides no direct measure of well costs for deeper EGS targets for the long term” (MIT 2006). Also, the following factors are just a few of the parameters necessary to make a reasonable estimate of drilling costs alone:     Drill-site specifics Stimulation approaches Well diameters and depths Well production interval lengths and diameters

Ongoing comparisons of geothermal well costs to wells drilled by the oil and gas industry make such estimations more reasonable. As geothermal wells increase in depth, more casing strings, which provide necessary stability to wells, are required. It is estimated that a 1.5 km deep EGS well will require 4 casing strings and cost approximately $2.3 million to complete (MIT 2006). By comparison, a 10 km deep EGS well will require 6 casing strings and cost approximately $20 million to complete. Capital Costs The inclusion of capital costs is imperative when analyzing potential costs of the EGS potential, including an approximation of capital reimbursement and interest charges. The California Energy Commission (CEC) estimated in 2006 that capital costs account for approximately 65 percent of the total cost of geothermal power.

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When considering the cost of a conversion plant that generates electricity from geothermal energy, it has been estimated that such costs can range from $2,300 per kW for resources at around 100°C to $1,500 per kW for resources at around 400°C. Other Related Costs Other costs, such as operation and maintenance (O&M), may not make as large an impact on the overall cost of an EGS operation. However, this is not to say such costs are insignificant. One source estimated that maintenance costs for hydrothermal systems could be double that of fossil fuel power plants due to such factors as corrosion of the well casing (EPRI 2011). As EGS operations can reach much deeper depths, requiring more well casings to accommodate deeper wells, it is plausible that O&M costs for EGS to exceed those estimations. Based on estimates from the CEC, approximately 35 percent of the total cost of EGS is comprised mostly of:  Fuel (i.e. water, in the case of geothermal energy)  Parasitic pumping loads  Labor and access charges  Variable costs Such factors are essential to the general operation and maintenance of sustaining production in the power plant.

Levelized Cost of Electricity
The experimental nature of EGS technology makes it difficult to evaluate the costs of a commercial scale EGS power plant. Initial estimates suggest that with current technology, the capital costs of an EGS plant would be roughly twice that of a traditional geothermal plant. While the capital costs of an EGS plant currently exceed those of a traditional fossil fuel power plant, one must look at the actual cost of generating electricity. Unlike a coal or natural gas plant, EGS facilities do not need to purchase fuel to generate electricity. This difference can be accounted for through a levelized cost analysis. Estimates of the cost of EGS vary and are uncertain because the cost of reservoir creation varies greatly depending on the geological formations at each EGS site. Using current drilling technology at an ideal site (marked by high temperatures at shallow depths and easily drillable geology), would allow for electricity generation at an estimated levelized cost of 17.5 to 29.5 cents per kilowatt-hour (kWh). At less suitable, yet still technically feasible locations (that require deeper drilling, often through hard granite formations), EGS could generate electricity at a cost of as much as 74.7 cents per kWh. EGS costs are especially difficult to calculate given that current EGS plants are small pilot facilities designed for research, not power production. Subsequent commercial-scale plants are expected to achieve economies of scale. As such, the
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costs of currently operating plants provide limited insight into the costs of a commercial-scale EGS facility. Cost reductions seen for similar technologies used in the oil and gas industry in the past indicate the potential for significant cost reductions for EGS. With time, as EGS nears commercialization, EGS is projected to competitively produce electricity at 3.6 to 9.2 cents per kWh. Advancements in wind power, solar power, and EGS all require up-front costs for technological development and initial implementation. But as noted above, EGS has the benefit of effective, cost-efficient infrastructure that is already in place. Concerning the cost of energy itself, here is the price-per-kilowatt hour for each of these renewables according to the U.S Department of Energy estimated for 2009: Geothermal: $.06-$.10 per kilowatt hour. EGS: Presently undetermined. MIT estimates that after initial development, energy from EGS will be comparable in price to energy from popular nonrenewable resources. Wind: $.04-$.07 per kilowatt hour. Solar: $.21-$.081 Figure 5 shows the levelized cost estimated for new power plants to be brought on line in 2016, as some technologies require long lead times and may not be able to come online before 2016 unless construction had already commenced (EIA 2010). In the graph, “CCS” refers to “carbon control and sequestration,” “NG” refers to “natural gas-fired plants” and “CC” refers to “combined cycle.” Factors considered when conducting this calculation include (EIA 2010):  Overnight capital costs  Fuel costs  Fixed and variable O&M costs  Financing costs  Assumed utilization rate for each plant type

Figure 5: Estimated Levelized Cost of New Generation Power
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5
Emission Reduction Potential

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Summary of Regulations
In the United States, the environmental impact of any type of power project is subject to many forms of regulation. All of the following laws and regulations play a role before any geothermal development project can be brought to fruition (Kagel et al., 2005):  Clean Air Act  National Environmental Policy Act  National Pollutant Discharge Elimination System Permitting Program  Safe Drinking Water Act  Resource Conservation and Recovery Act  Toxic Substance Control Act  Noise Control Act  Endangered Species Act  Archaeological Resources Protection Act  Hazardous Waste and Materials Regulations  Occupational Health and Safety Act  Indian Religious Freedom Act

Potential Environmental Impacts
There are several potential environmental impacts from any geothermal power development. These include:  Gaseous emissions  Water pollution  Solids emissions  Noise pollution  Land use  Land subsidence  Induced seismicity  Induced landslides  Water use  Disturbance of natural hydrothermal manifestations  Disturbance of wildlife habitat and vegetation  Altering natural vistas  Catastrophic events. Despite this long list, current and near-term geothermal energy technologies generally present much lower overall environmental impact than do conventional fossil-fueled and nuclear power plants. For example, the power plant is located above the geothermal energy resource eliminating the need (a) to physically mine the energy source (the “fuel”) in the conventional sense and, in the process, to disturb the Earth’s surface, and (b) to process the fuel and then use additional energy to transport the fuel over great distances while incurring additional
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environmental impacts. Furthermore, the geothermal energy conversion equipment is relatively compact, making the overall footprint of the entire system small. With geothermal energy, there are no atmospheric discharges of nitrogen oxides or particulate matter, and no need to dispose of radioactive waste materials.

Summary of Environmental Benefits
EGS, like traditional geothermal energy, constitutes a source of electricity that is almost entirely free of greenhouse gas (GHG) emissions. Only small traces of carbon dioxide and other GHGs might be released from geological formations during the drilling phase of an EGS plant’s life. The greatest environmental benefit of EGS comes from its ability to satisfy baseload electricity demand. Unlike intermittent renewable energy technologies, such as wind and solar power, EGS could provide a consistent electricity supply similar to carbon-intensive coal-fired power plants. Replacing the generation from a typical 500 MW coal-fired power plant with electricity from geothermal plants would avoid about 3 million metric tons of CO2 emissions per year (roughly 0.1 percent of total U.S. CO2 emissions from electricity generation). Table below shows a comparison of typical geothermal plants with other types of power plants (Kagel et al., 2005). The data indicate that geothermal plants are far more environmentally benign than the other conventional plants. It should be noted that the NOX at The Geysers comes from the combustion process used to abate H2S in some of the plants; most geothermal steam plants do not rely on combustion for H2S abatement and therefore emit no NOx at all. Plant Type Coal-Fired Oil- Fired Gas- Fired Hydrothermal- flashsteam, liquid dominated Hydrothermal- The Geysers dry steam field Hydrothermalclosed-loop binary EPA average, all U.S plants CO2 kg/MWh 994 758 550 27.2 40.3 0 631.6 SO2 kg/MWh 4.71 5.44 0.0998 0.1588 0.000098 0 2.734 NOX kg/MWh 1.955 1.814 1.343 0 0.000458 0 1.343 Particulates kg/MWh 1.012 N.A. 0.0635 0 Negligible Negligible N.A

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The installation of EGS would likely be expanded under a national climate or energy policy. Unfortunately, projections of renewable energy innovation under climate policies typically do not include predictions about EGS growth, given the experimental nature of the technology. These same projections, however, expect traditional geothermal to grow under a climate policy. The overlap of the two geothermal technologies means that innovations in traditional geothermal should bolster the prospects of EGS as well. According to a panel of experts convened by MIT in 2006, EGS could reach an installed capacity of 100,000 MW by 2050—roughly a third of todays installed coal capacity. Abandoned or unproductive domestic oil fields could be adapted to EGS. The unproductive oil fields of Texas, for example, not only have already drilled bore holes, but also have verified thermal and geological information. Retooling these fields to produce hot water, instead of oil, could greatly expand the installed capacity of EGS once it reaches commercial deployment.

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6
Current Developments & Going Forward

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EGS Worldwide
EGS remains in the research and development stage. Experimentation with EGS first began in the 1970s with a series of pilot projects at Fenton Hill, New Mexico. While the projects did not operate on a commercial scale, they did demonstrate the feasibility of the geologic engineering and drilling techniques needed to artificially create hydrothermal reservoirs. Since then, experimental EGS plants and pilot projects have been undertaken around the world. Realizing the full potential of EGS will take some time, and the International Energy Agency (IEA) believes that substantially higher research, development, and demonstration (RD&D) efforts are needed to ensure EGS becomes commercially viable by 2030. In the United States, there has been growing interest in EGS. In 2009, the American Recovery and Reinvestment Act included $80 million for research and development of EGS technologies. The U.S. Department of Energy’s (DOE) Geothermal Technologies Program oversees on-going research and development related to EGS with the goal of improving the performance and lowering the cost of EGS technologies. The Geothermal Technologies Program partners with national laboratories, universities, and the private sector on EGS component technology research and development projects and EGS system demonstration projects. Two prominent EGS-related research projects are wastewater injection at The Geysers in California (the oldest geothermal field in the United States and largest geothermal venture in the world) and Desert Peak in Nevada, where EGS capacity will be added to an existing geothermal field. Finally, the Bureau of Land Management leases land in eleven Western states for continued geothermal resource development. The European Union has long been involved in the efforts to research and develop enhanced geothermal systems technologies. France and Germany have operational EGS demonstration projects (1.5 to 2.5 MW), while Iceland and Switzerland are members of the International Partnership for Geothermal Technology (IPGT). The United States and Australia are also members of the IPGT, which is working to identify effective methodologies and practices for EGS development. The Soultz Project in France The Soultz project is part of a larger European Union objective to ensure a reliable energy supply based on Renewable Energy Sources. Since 1987 several national HDR research programs have been integrated into one European program at Soultzsous-Forets, France. The partners include Italy, France, Switzerland, Germany and the UK. The research has been done by national teams with funding from their mother countries. An interested group of private companies has also participated in the project since 1992. In 1998 they formed the European Economic Interest Group (EEIG) to play a more active role in the work. In April 2001 the EEIG took over direction, co-ordination and management from the original European Commission (EC). The goal is to develop techniques to circulate water in a closed loop system
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between two or more boreholes through a constructed fracture system. The system is designed to provide a surface area of several square kilometers to transfer heat. A test was carried out in 1997 that showed it was possible to circulate 25 l/s (liters per second) between two wells at a depth of 3000-3500 meters and with well separation of about 450 meters. The test lasted for four months and showed low resistance to flow and zero water loss. But, temperatures were not high enough for electrical power generation. The funding agencies wanted temperatures to be reached for electricity generation, which they felt was around 200 degrees Celsius. One of the wells was deepened to 5000 meters. In 1998/9, 202 degree Celsius was reached at 5000 meters. The present and future stages of the project, involves drilling two more 5000 meter wells. Then, fracture the intervening rock and achieve water flow between wells at rates of up to 100 l/s. If this is successful a pilot plant will be built with four 1.5 megawatt generating units. Eventually an industrial plant with more wells will be constructed with a capacity of 20-25 megawatts. Table below shows different EGS projects worldwide and their certain characteristics.
Project Soultz Landau Aardwarmte Den Haag Paralana (Phase 1) Cooper Basin Bend, Oregon Ogachi United Downs, Redruth Eden Project Type R&D Commercial Commercial Commercial Commercial Demonstration R&D Commercial Commercial Country France (EU) Germany (EU) Netherlands (EU) Australia Australia United States Japan United Kingdom United Kingdom Size (MW) 1.5 3 6 7–30 250– 500 NA NA 10 3 Depth (km) 4.2 3.3 2.0 4.1 4.3 2-3 Status Operational Operational Operational 2012; wells tested 2010. Heating 4,000 homes in central city. Drilling Drilling Permitting (Mar 2010)

1.0 – 1.1 CO2 experiments 4.5 Fundraising 3–4 Fundraising

EGS Development in the US
Current EGS field research in the United States is based at three sites on the margins of operating hydrothermal systems: Coso, Desert Peak, and Glass Mountain/ Geysers-Clear Lake.

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The Coso project was designed to test the ability to fracture low-permeability, hightemperature rocks on the edge of the Coso geothermal area. The project has characterized the resource, tested thermal stimulation of a low permeability well of opportunity, and done baseline studies in preparation for a major hydraulic fracture stimulation in a deep high-temperature well. The Desert Peak project has targeted one well not connected with the Desert Peak geothermal system for stimulation to form an EGS. Political and environmental permitting issues have led to the cancellation of the Glass Mountain project, which targeted low-permeability, high-temperature rocks outside a known hydrothermal system. The industry partner has moved the project to its operating plant in an area in The Geysers with low-permeability, high noncondensable gas, and acidic steam. The new project scope would target stimulation of low-permeability rock on the fringe of the production area to improve steam quality and recharge the reservoir while mining heat.

Obstacles to Further Development EGS
Need for Technology Research, Development, and Demonstration (RD&D) A lack of RD&D constrains the deployment of EGS power plants. Most technologies used in EGS, such as drilling and geologic imagery techniques, are not yet adapted for specific use in EGS development. High-Risk Exploration Phase The exploratory phases of a geothermal project are marked by not only high capital costs but also a 75 percent chance of failure, when high fluid temperatures and flow rates are not located. The combination of high risk and high capital costs can make financing geothermal projects difficult and expensive. Knowledge of Geothermal Geology The ability to artificially create geothermal reservoirs consistently is greatly limited due to a lack of understanding of how geothermal reservoirs occur in nature. Researching the geological characteristics of natural geothermal resources is essential to adapting stimulation and drilling techniques in such a way that drives down the costs of EGS development. Geographic Distribution and Transmission Despite the siting flexibility of EGS technologies, the most promising EGS sites often occur great distances from regions of large electricity consumption, or load centers. The need to install adequate transmission capacity can deter investment in geothermal projects.
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Policy Options to Help Promote EGS
Price on Carbon A price on carbon would raise the cost of electricity produced from fossil fuels relative to the cost of electricity from renewable sources, such as EGS, and other lower-carbon technologies. A price on carbon would increase both deployment of mature low-carbon technologies and R&D investments in less mature technologies. Clean Energy Standard A clean energy standard is a policy that requires electric utilities to provide a certain percentage of electricity from designated low carbon dioxide-emitting sources. At present, 31 U.S. states and the District of Columbia have adopted clean energy standards and clean energy standard has been proposed at the federal level. Clean energy standards encourage investment in new renewable generation and can guarantee a market for this generation. Research, Development and Demonstration Rapidly moving along the EGS technological “learning curve” requires sustained funding of further research efforts in the form of pilot plants and basic research in geology, drilling techniques and other associated EGS technologies. Streamline Government Leasing and Permitting Procedures Quickly deploying EGS will require federal agencies to more efficiently process applications for the development of EGS plants on public lands. Accelerating the speed of siting, leasing and permitting decisions will help make already risky EGS projects more attractive to investors. Development of New Transmission Infrastructure Improving transmission corridors to areas with geothermal reservoirs would facilitate investment in geothermal energy. Policies to build new transmission to areas with significant renewable energy resources are already proposed for accessing the wind-rich regions of the central plains and the extensive solar resources of the desert southwest. Such policies could also promote expanded transmission to reach the geothermal fields of the West.

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7
Conclusion

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Geothermal energy from EGS represents a large, indigenous resource that can provide base-load electric power and heat at a level that can have a major impact on the United States, while incurring minimal environmental impacts. With a reasonable investment in R&D, EGS could provide 100 GWe or more of costcompetitive generating capacity in the next 50 years. Further, EGS provides a secure source of power for the long term that would help protect America against economic instabilities resulting from fuel price fluctuations or supply disruptions. Most of the key technical requirements to make EGS work economically over a wide area of the country are in effect, with remaining goals easily within reach. This achievement could provide performance verification at a commercial scale within a 10- to 15-year period nationwide. In spite of its enormous potential, the geothermal option for the United States has been largely ignored. In the short term, R&D funding levels and government policies and incentives has not favored growth of U.S. geothermal capacity from conventional, high-grade hydrothermal resources. Because of limited R&D support of EGS in the United States, field testing and supporting applied geo-science and engineering research has been lacking for more than a decade. Because of this lack of support, EGS technology development and demonstration recently has advanced only outside the United States with accompanying limited technology transfer. This has led to the perception that insurmountable technical problems or limitations exist for EGS. The paper signifies the progress has been achieved in recent tests carried out at Soultz, France, under European Union (EU) sponsorship; and in Australia, under largely private sponsorship. Such progress leads us to be optimistic about achieving commercial viability in the United States in a next phase of testing, if a national-scale program is supported properly.

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REFERENCES
1. “Tester, J., et al. 2006, The Future of Geothermal Energy: Impact of Enhanced Geothermal Systems (EGS) on the United States in the 21st Century, Massachusetts Institute of Technology. http://www1.eere.energy.gov/geothermal/pdfs/future_geo_energy.pdf 2. U.S. Department of Energy. 2008. “The Basics of Enhanced Geothermal Systems”, Accessed 22 August 2012. http://www1.eere.energy.gov/geothermal/pdfs/egs_basics.pdf 3. Williams, E., et al. 2007, A Convenient Guide to Climate Change Policy and Technology. http://www.nicholas.duke.edu/ccpp/convenientguide/cg_pdfs/ClimateBook.pdf 4. U.S. Energy Information Administration (EIA), 2011. 5. Williams, C., et al. 2008, Assessment of Moderate-and High-Temperature Geothermal Resources of the United States, United States Geological Survey. http://pubs.usgs.gov/fs/2008/3082/pdf/fs2008-3082.pdf 6. U.S. Department of Energy’s Geothermal Technologies Program’s webpage: “How an Enhanced Geothermal System Works” http://www1.eere.energy.gov/geothermal/egs_animation.html 7. U.S. Department of Energy (DOE). 2008, An Evaluation of Enhanced Geothermal Systems Technology. http://www1.eere.energy.gov/geothermal/pdfs/evaluation_egs_tech_2008.pdf 8. DOE, Geothermal Tomorrow 2008. http://www.nrel.gov/docs/fy08osti/43504.pdf 9. Pushing the Envelope of Geothermal Power to Prepare for the Next Generation Brooks Proctor, http://www.indiana.edu/~sierra/papers/2005/proctor.html 10. Geothermal Energy, The Economics of West Virginia’s EGS Potential http://www.marshall.edu/cber/research/GeothermalWhitePaper.pdf

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