Moving HDR technology toward commercialization

Conventional geothermal resources are currently being developed in many parts of the world where naturally occurring steam or hot water can be extracted from the earth. These hydrothermal resources, however, provide access to only a small fraction of the energy contained within the crust of the earth. In most regions, the heat of the earth is contained in hot rock at depth. The total amount of energy available in the form of hot dry rock (HDR) is extremely large. Estimates place the magnitude of the accessible HDR resource base worldwide at greater than 10 million quads (Armstead and Tester 1987) (1 quad equals 15 quadrillion Btu, or the energy content of about 180 million barrels of oil). For the past two decades, the Hot Dry Rock Program sponsored by the United States Department of Energy at the Los Alamos National Laboratory has been directed toward the development of methods to extract the vast amounts of energy which exist in HDR. The stated Level 1 Department of Energy objective for the Hot Dry Rock (HDR) Heat Mining Geothermal Energy Development Program is to {hor ellipsis} provide the technology to enable industrial hot dry rock projects to generate power at 5--8c/kWh by 1997.'' (USDOE 1989) Fundamental to this objective is the ultimate goal of bringing HDR technology to commercial fruition. Indeed, all of the work done in this exciting research and development area will be for naught if we fail to move as rapidly as possible toward the utilization of this abundant and clean energy resource as one of the important elements in the future energy supply of the world. The purpose of this paper is to outline a path toward the commercialization of HDR heat mining technology, to discuss the potential obstacles in such a path, to propose techniques for overcoming those obstacles, and finally, to present a picture of what a commercial HDR facility may look like near the beginning of the next century. 14 refs., 3 figs., 2 tabs

The history of HDR research and development

An energy source rivaling the sun exists in the form of the heat emanating from the interior of the earth. Although limited quantities of this geothermal energy are produced today by bringing natural hot fluids to the surface, most of the earth`s heat is trapped in hot dry rock (HDR). The application of hydraulic fracturing technology to tap this vast HDR resource was pioneered by Los Alamos National Laboratory beginning in 1970. Since that time, engineered geothermal reservoirs have been constructed and operated at numerous locations around the world. Major work at the US HDR facility at Fenton Hill, NM, and at the British HDR site in Cornwall, UK, has been completed, but advanced HDR field work continues at two sites on the island of Honshu in Japan and at Soultz in northeastern France. In addition, plans are currently being completed for the construction of an HDR system on the continent of Australia. Over the past three decades the worldwide research and development effort has taken HDR from its early conceptual stage to its present state as a demonstrated technology that is on the verge of becoming commercially feasible. Extended flow tests in the United States, Japan, and Europe have proven that sustained operation of HDR reservoirs is possible. In support of these field tests, an international body of scientists and engineers have pursued a variety of innovative approaches for assessing HDR resources, constructing and characterizing engineered geothermal reservoirs, and operating HDR systems. Taken together, these developments form a strong base upon which to build the practical HDR systems that will provide clean energy for the world in the 21st century

Hot dry rock in the United States: Putting a unique technology to practical use

Hot dry rock (HDR) geothermal energy technology is unique in many aspects. HDR resources are much more widely distributed than hydrothermal resources, the production temperatures of fluids extracted from fully-engineered HDR reservoirs can be selected at will, and other important characteristics of HDR reservoirs can be controlled and even deliberately varied over time. Because HDR reservoirs can be rapidly discharged and recharged, a wide variety of operating scenarios can be envisioned that are not normally feasible for hydrothermal systems. Flow testing over the past few years has shown that HDR systems can be operated in a routine, automated manner that should make them rapidly adaptable to industrial applications. An industry-led HDR project now being formulated will lead to the development and operation of a practical facility to produce and market energy from an HDR resource by the turn of the century

Vacuum deposition of high-quality metal films on porous substrates

A composite mandrel has been developed consisting of a core of low density polymethylpentene foam overcoated with a thin layer of film forming polymer. The surface tension and viscosity of the coating solution are important parameters in obtaining a polymer film which forms a continuous, smooth skin over the core without penetrating into the foam matrix. Water soluble film formers with surface tensions in the range of 45 dynes/cm and minimum viscosities of a few hundred centipoises have been found most satisfactory for coating polymethylpentene foam. By means of this technique, continuous polymer films with thicknesses of 10 to 20 ..mu..m have been formed on the surface of machined polymethylpentene foam blanks. Aluminum has been vacuum deposited onto these composite mandrels to produce metal films which appear smooth and generally defect free even at 10,000 times magnification

Neurophysiology

Contains reports on one research project.National Science FoundationOffner Electronics, IncorporatedTeagle FoundationBell Telephone Laboratories, Incorporate

Neurophysiology

Contains reports on three research projects.Bell Telephone Laboratories, IncorporatedTeagle FoundationNational Science FoundationOffner Electronics, Incorporate

Neurophysiology

Contains reports on four research projects.Bell Telephone Laboratories, IncorporatedThe Teagle Foundation, IncorporatedNational Science Foundatio

Neurophysiology

Contains research objectives and reports on four research projects.Bell Telephone Laboratories, IncorporatedNational Institutes of HealthNational Science FoundationTeagle Foundation, Incorporate

Hot Dry Rock geothermal energy moving towards practical applications

The thermal energy present in hot rock at depth is a vast resource which has so far been tapped only in those unusual locations where natural fluids exist to transport that energy to the surface. For the past twenty years work has been underway at the Los Alamos National Laboratory to develop the technology to access and recovery the heat present in rock which is hot but contains no natural mobile fluid. The world`s first plant capable of sustained production of geothermal energy from HDR was completed in 1991. This facility combined an artificial geothermal reservoir of sufficient size and high enough temperature to deliver large amounts of useful energy with a surface plant built to power industry standards and capable of sustained, routine operation. During the past two years, extended testing at Fenton Hill has demonstrated that energy can be extracted from HDR on a continuous basis. Thermal energy was produced continuously at a rate of about 4 MW in two test phases lasting 112 and 55 days, respectively, and intermittently for a period of 7 1/2 months between the continuous test segments. Temperature measurements at the surface and at depth indicated no decline in the average discharge temperature of water from the reservoir over the span of the test. In fact, tracer testing indicated that access of the circulating water to the hot reservoir rock improved as the test proceeded