Enhanced Geothermal Systems – the Future of Renewable Energy in the United States

Stephen J. Bell

Introduction

Humans have used geothermal energy for thousands of years. In the United States, the oldest known use of geothermal energy was when Native Americans flocked to hot springs, which were especially useful for cooking. Hot springs were considered so valuable and important that Native American tribes were located near every hot spring in the nation and deemed them neutral territory open to all. Compared to its alternatives, geothermal energy production is clean, renewable, safe for the environment, inexpensive, and has an incredibly high output capacity. Geothermal energy has a small market presence today because current geothermal energy plants have limited output due to the difficulty of drilling deep into the earth. These limitations, paired with the relative ease of alternative energy production means, have prevented the United States from tapping a renewable energy source that may be second only to the sun. While our domestic energy requirements are significant, geothermal energy technology is advancing at a rate that should allow the United States to produce large amounts [how large?] of safe, clean, and reliable environmentally friendly energy by the year 2030.

How Geothermal Energy Works

Geothermal energy production takes many forms and, in theory, is fairly simple. One only needs heat, water, and permeability (the ability for water to move through the ground) to produce geothermal energy. This simple recipe makes it clear why geothermal energy is so clean and environmentally friendly – geothermal plants’ only real emission is steam. The fact that geothermal energy production does not release greenhouse gases into the atmosphere also makes it an attractive global energy option in the face of climate change. Current geothermal energy production takes one of three forms: geothermal power plants, direct-piped hot water, or geothermal heat pumps.

Geothermal power plants are the world’s largest producers of geothermal energy and come in three forms. Dry steam power plants are the world’s oldest type of geothermal power plant and were first used in Italy in 1904. Dry steam power plants use nothing but steam to produce power and require builders to drill a hole deep into geothermal reservoirs that produce this steam. As the steam rises from the earth, it is funneled into a pipe connected to a turbine. The steam spins the turbine, which is connected to an electrical generator. The beauty of this system is that power is easily produced and no fuels or other chemicals are burnt in the process. The second form of geothermal power plant is the flash steam power plant, which relies on steam and water to produce power. Like dry steam power plants, flash steam power plants use a turbine and electrical generator. However, flash steam power plants pull incredibly hot water from the earth. This hot water is funneled into a low-pressure tank that causes some of the water to “flash” into steam, which spins the turbine and produces power. Excess water is then pumped into a secondary low-pressure tank to induce additional steam. Like dry steam power plants, these plants emit nothing more than steam into the air. The third form of power plant is the binary-cycle plant, which uses hot water to produce power. Binary-cycle plants require the addition of a secondary liquid to produce electricity. Binary-cycle plants are built like the other types of plant, but have a liquid storage tank immediately before the turbine. Most of the water that rises from reservoirs is hot but not boiling. Because of this, binary-cycle plants utilize liquids with boiling points lower than that of water to spin the turbine. As hot water flows into the second liquid, the second liquid turns to steam and spins the turbine. Excess water is then pumped back into the earth and the plant emits no harmful gases. [is steam harmful?]

Direct-piped hot water is used in a small number of locations for a limited number of uses and is not suited to produce large amounts of power. Most direct-piped systems are city or state projects that heat government property. For instance, cities will often run hot water pipes beneath roadways, parking lots, and sidewalks to prevent ice formation. Large governmental, educational, and residential buildings are often connected to a direct-piped heating system. Finally, direct-piped water is used to keep small bodies of water warm during the winter, warm greenhouses, and keep farmland a suitable temperature. If not for its limited availability, direct-piped water heating systems might be an excellent way for cities to “go green.” Installation costs may be high, [how high?] but the energy is completely renewable and requires no maintenance once constructed. For road heating especially, direct-piped water heating systems may prove very economical in the long-term.

The third and final form of geothermal energy production is the geothermal heat pump. Despite the range of temperatures we see from winter to summer, the earth’s temperature remains incredibly constant. Geothermal heat pumps use this steady temperature source to cool buildings in the summer and heat them in the winter. To accomplish this goal, pipes are laid underground in one of many formations and connected to an above-ground “heat-exchanger” (which is typically smaller than a traditional air-conditioning unit). Advances in geothermal heat pump technology allow for heating and cooling at one-quarter to one-half the price of traditional heating and cooling systems. The EPA claims that geothermal heat pumps reduce energy consumption and emissions 44% below normal air-source heat pumps and 72% below air-conditioning units. Geothermal heat pumps’ biggest drawback is that they cost much more than traditional heating and cooling systems. However, this sizeable installation cost is generally recouped by energy savings after five to ten years. [net present value?] Perhaps the most significant benefit of geothermal heat pumps is their longevity. Heat-exchangers have a twenty-five year life span and underground pipes have a fifty year life span. Compared to traditional heating and cooling options, geothermal heat pumps have an excellent cost/benefit ratio (especially for use in government and educational buildings that will stand for long periods of time). The American public is embracing geothermal heat pumps as time passes, and approximately fifty thousand new units are installed annually. [relative to new installation?] Geothermal heat pumps’ final benefit is that they can be built in conjunction with traditional heating and cooling systems. Thus, a building can use the earth’s temperature to provide heating or cooling and, if more power is needed, a back-up unit can activate and provide additional power.

The Next Step: Enhanced Geothermal Systems

According to the Department of Energy, current geothermal energy production only lets us reach the “low hanging fruit” of the earth’s heat supply. A new wave of technology – enhanced geothermal systems – will allow the United States to produce enough geothermal energy to provide at least 10% (and potentially 100%) of the nation’s energy needs. Unlike current geothermal energy production, which is only available in certain areas, enhanced geothermal systems can be built nearly everywhere in the world, making them a viable “green” energy option for every country in the world.

Enhanced geothermal systems go beyond tapping reservoirs and, in fact, will produce power by tapping into magma and other deep, hot layers of the earth. Enhanced geothermal systems may be considered a type of deep-earth fracking. Companies will drill deep into the earth (scientists estimate that drilling depths may exceed 6.2 miles at some sites) to fracture hot rock. Water will then be pumped through the hot rock and, after turning to steam, will rise to the surface and spin power-producing turbines. Any excess water will be pumped back into the hot rock, resulting in a closed-loop power plant that has near-zero harmful emissions. Like traditional geothermal energy production, these plants’ main emission is steam. The United States’ push for nationwide enhanced geothermal systems is fueled in part by an MIT study claiming that 2% of the heat trapped beneath the continental United States could provide more than twenty-six hundred times our annual domestic energy needs. Contrary to traditional geothermal energy plants, every state has the potential to tap this heat source. Given the fact that enhanced geothermal systems have almost no detrimental environmental effects and are renewable, this statistic is truly profound. There exists a means for the United States to become entirely energy-independent, reduce or eliminate harmful emissions that contribute to climate change, transition away from energy sources that pollute, and lower energy costs. Enhanced geothermal systems also have the ability to shift the global energy system towards cleaner, more reliable energy.

One of the biggest obstacles impeding the growth of current geothermal energy production is that geothermal power plants require earth permeability (the ability for water to move through the earth) to operate. It is for this reason that current geothermal power plants are located near geysers and are more frequent in certain states. Permeability at these sites is limited and thus energy output is as well. By employing fracking at incredible depths, enhanced geothermal systems will allow companies to operate plants anywhere in the nation. At medium depths, fracking will drastically increase the amount of heat that can be tapped. As drilling depths increase, however, fracking will be needed less due to the increased permeability of “hot rock” beds near the earth’s core.

As with all potential energy production technologies, cost is an issue. Construction costs of enhanced geothermal systems are significant and increase with drilling depth. Plants reaching depths of six miles or more are estimated to rack up at least thirty million dollars in drilling expenses alone. [doesn’t sound like much – how much installation cost per GW? Compare to other means – graphic?] When added to the cost of infrastructure, an enhanced geothermal system may be incredibly expensive. Because current drilling technology will not allow us to tap the amazing “2%” – and because other energy production technologies are established – the necessary profit margin (and resulting incentive to innovate) to shift companies away from oil and other energy sources is not there. Technological advances, particularly in drilling, should significantly reduce construction costs, make enhanced geothermal systems much more affordable, and increase potential geothermal energy companies’ bottom lines. According to the enhanced geothermal systems research team at MIT, “we have found a strong positive correlation between the early deployment of new EGS facilities and the significant decline in the levelized cost of delivered electricity. This finding reflects not only the economies from new techniques and access to higher-value resources, but also the inevitable changes in availability and increased cost of conventional energy sources. For example . . . in the case of coal-fired [how does natural fracking change this?] electricity, increased bus-bar costs are predicted as result of three effects occurring over time: (i) fuel cost increases, (ii) higher capital costs of new facilities to satisfy higher efficiency and environmental quality goals, including capture and sequestration of CO2, and (iii) retirement of a significant number of low-cost units in theexisting fleet due to their age or failure to comply with stiffer environmental standards. In the case ofnuclear facilities, we anticipate a shortfall in nuclear supplies through the forecast period, reflecting retirement of the existing power reactors and difficulties in siting and developing new facilities. Without corresponding base-load replacements to meet existing and increased demand, the energy security of the United States will be compromised. It would seem prudent to invest now in developing a portfolio of options that could meet this need. To sum up, based on our technical and economic analysis, a reasonable investment in R&D and a proactive level of deployment in the next 10 years could make EGS a major player in supplying 10% of U.S. base-load electricity by 2050. Further, the analysis shows that the development of new EGSresources will not be limited by the size and location of the resource in the United States, and it will occur at a critical time when grid stabilization with both replacement and new base-load power will be needed. Adding the EGS option to the U.S. portfolio will reduce growth in natural gas consumption and slow the need for adding expensive natural gas facilities to handle imported liquefied natural gas (LNG).” [already study is obsolete!] Thus, the key to implementing enhanced geothermal systems on a nationwide (and hopefully planet-wide) scale is to incentivize technological development to the point that it costs energy companies more to use other forms of energy production than to use enhanced geothermal systems.

Legal Aspects of Enhanced Geothermal Systems

President Obama memorialized the United States’ interest in enhanced geothermal systems technology when he passed the American Recovery and Reinvestment Act of 2009 (“Act”). During the course of the legislation, Director of Energy Steven Chu stated that “[w]e have an ambitious agenda to put millions of people to work by investing in clean-energy technology like solar and geothermal energy. These technologies represent two pieces of a broad energy portfolio that will help us aggressively fight climate change and renew our position as a global leader in clean energy jobs.”President Obama [Congress?] granted three-hundred and fifty million dollars of federal funds towards research and development, construction, and modification of enhanced geothermal systems. This funding is specifically aimed at locating ideal drilling sites, developing efficient and affordable drilling technologies, and studying the effects of deep-earth fracking. Much of this funding goes to Sandia National Laboratories, which is tasked with drilling technology advancement. “[B]ecause drilling and well completion can account for more than half of the capital cost for a geothermal power project”, Sandia National Laboratories uses its federal funding to develop faster drills, increase drills’ useful life, and increase per-well energy output.[what’s happened here?]

The United States also passed 42 U.S.C. § 17194, titled “Enhanced geothermal systems research and development.” Section 17194(b)(1) requires the government to“support a program of research, development, demonstration, and commercial application of the technologies and knowledge necessary for enhanced geothermal systems to advance to a state of commercial readiness.” The goal of this legislation is to determine sites best-suited to commercial enhanced geothermal systems plants. Four or more plant sites must be identified, studied, mapped, and tested for output capacity. A Department of Energy site located at the Desert Peak thermal field in Nevada was listed in the statute as a candidate for one of the four required sites. The Desert Peak project illustrates the broad range of parties collaborating to produce inexpensive power from an enhanced geothermal systems plant. These parties include the Department of Energy, the University of Utah, the U.S. Geological Survey, ORMAT Nevada, Inc., and GeothermEx, Inc. While the Desert Peak site focuses primarily on deep-earth fracking, Section 17194(b)(2)(A)(i) requires other sites that “represent a different class of subsurface geologic environments” to address drilling technology and other technological deficits that plague enhanced geothermal systems.

On the international level, the United States joined the International Energy Agency’s Implementing Agreement for a Co-Operative Programme on Geothermal Energy Research and Technology (“Agreement”). Members to the Agreement include France, Italy, the European Union, Germany, New Zealand, Spain, Norway, Mexico, the Republic of Korea, Japan, Iceland, Switzerland, and Australia. Each country participates in one of the Agreement’s “Annex” research assignments. Annex III deals with development of enhanced geothermal systems and its marketability on a global scale. Annex III is divided into five Tasks, of which the United States leads two. Task A involves standardized economic modeling of enhanced geothermal systems that takes “in to consideration the local incentives, local labour and other environmental requirements and conditions.” The United States, through the Idaho National Engineering and Environmental Laboratory, leads Task B, which aims to modify and/or invent technology to increase the feasibility of enhanced geothermal systems. Task B’s focus is on deep-earth fracking.Switzerland leads Task C, titled Data Acquisition and Processing, which“involves the collection of information necessary for the realization of a commercial EGS energy producing plant at each stage of reservoir characterization, design and development, and of construction and operation.” Australia leads task D, which is aimed at developing earth-evaluation techniques that allow companies to identify land best-suited to deep-earth drilling. Task E is headed by the United States, through the University of Utah, and studies reservoir performance. [where does this stand?]

While there exist domestic and international legal agreements promoting enhanced geothermal systems development and implementation, the United States should offer additional incentives for power companies to switch to this type of energy production. Enhanced geothermal systems sounds too good to be true – it is clean, emits no greenhouse gases, does not contribute to climate change or global warming, and is arguably safe. A significant increase in federal funds for enhanced geothermal systems research and development, coupled with existing private funding, should help push the energy industry towards this amazing form of energy production. Fortunately, private funding for enhanced geothermal systems is becoming easier to obtain as time passes, especially from corporations like Google. [didn’t Google recently withdraw?] At the 2008 National Clean Energy Summit, Google’s Director of Climate and Energy Initiatives Dan Reicher stated that enhanced geothermal systems will likely be the “killer app” of the clean energy movement.

Environmental Impacts of Enhanced Geothermal Systems