[en] After very high growth in the 1980s, geothermal electricity production has slowed in the mid- and late-1990s. While Japanese, Indonesian and Philippine geothermal growth has remained high as a consequence of supportive government policies, geothermal electricity production has been flat or reduced in much of Europe and North America. Low prices for coal and natural gas, combined with deregulation, means that in much of the world electricity from new fuel-burning electricity plants can be provided at half the cost of new geothermal electricity. Cost-cutting must be pursued, but is unlikely to close the price gap by itself. Geothermal production is widely perceived as being environmentally clean, but this is not unambiguously true, and requires reinjection to be fully realized. Strategies for monetizing the environmental advantages of geothermal, including the carbon tax, are discussed. (author)

[en] The main aim of this project is the preparation of a data base of geothermal properties for typical rocks of the Swiss Molasse Basin (depth interval 0 to 500 m) combined with a simple evaluation software tool. The project includes the integration of numerous laboratory measurements of thermal conductivity and heat capacity with additional data calculated from geophysical borehole logs. Within the study area, 380 additional data points were generated with sonic and density log data from exploration wells. This new data base characterises in detail the 6 main lithological rock types in the 3 Molasse groups 'OSM', 'OMM' and 'USM' within the Swiss Plateau Molasse. The statistical evaluation of all data illustrates the regional variation of the petrophysical and geothermal parameters. The software tool SwEWS allows the analysis of a specific depth profile defined by the user. Based on the input for the stratal model the programme calculates the geothermal parameters for each horizon together with a temperature profile. The results can be analysed in various tables and a graphic display. For further use the data can also be exported as an ASCII file. Based on this new information and with the aid of the evaluation software tool SwEWS the costs of planned geothermal installations can be optimised by more precise heat extraction simulations with existing software packages like COSOND, TRNSYS, EWS or WPcalc. (author)

[en] Despite considerable effort, the Central and Eastern European Countries (CEECs) still face serious environmental problems related to their heating sectors. This is mainly due to the fact that most CEECs continue to rely heavily on conventional and polluting energy sources such as lignite, coal and heavy fuel-oil. However, increasing awareness and interest in converting to renewable and non-traditional energy sources are emerging in the region, strongly encouraged by the international community. Within the CEECs, geothermal energy is considered to be one of the most promising local energy sources. Geothermal water is found in significant quantity underground in the CEECs aspiring to become an important future environmentally friendly energy source for heating purposes. In view of this, the Danish Environmental Protection Agency (DEPA) commissioned Kvistgaard Consult to prepare a strategic study of economic, environmental, technical and institutional potentials of geothermal energy systems in the CEECs. As part of the study, an international workshop was held. An important conclusion from the workshop as well as from the study, is that the CEECs possess highly promising environmental and technical potentials for further development of geothermal energy systems for heating purposes. The study recommends concrete action proposals to be considered by DEPA. Volume 1 is the main report presenting the results of the Geothermal Energy Systems Assessment Project (GESA). (BA)

[en] Scientists believe naturally radioactive rocks below the earth's surface could provide an inexhaustible and environmentally friendly power source. And Australia could be a geological hotbed should the concept get off the ground. Despite the scale, the concept itself is simple. The Earth's reserves of heat in naturally radioactive rocks could provide an effectively inexhaustible and environmentally friendly source of power. No greenhouse gas emissions, little water usage and minimal pollution. Natural hot springs are already used to make power in some parts of the world, such as Iceland, but creating artificial hot springs by drilling deep into granite -the hardest of rocks - is a much more ambitious concept. One cubic kilometre of hot granite at 250 deg C has the stored energy equivalent of 40 million barrels of oil. In a nutshell, water is pumped into the hot zone - some 3km to 5km down in Australian conditions - and spreads through a 'reservoir' of hot, cracked rocks. Once superheated, it returns to the surface as steam through a separate production well to spin turbines and generate electricity. The water can then be recaptured and reused, with test sites around the world recovering up to around 90 per cent

[en] This document provides information on the geothermal energy. It presents the different types of geothermal deposits (very low, low and medium energy geothermal energy), the french deposits and the heat production. The electric power production from the geothermal energy is also discussed with the example of Soultz-sous-Forets. The last part deals with the heat pumps. (A.L.B.)

[en] This paper describes a comparative study of the thermal behaviour of drilling fluids and the surrounding rock when air-water mixtures and conventional muds are used as drilling fluids in geothermal wells. The computations were performed with two numerical simulators: TEMLOPI/V.2, which is used to compute the transient temperature disturbance when mud is employed, and GEOMIST, which is used when air-water mixtures are employed as drilling fluid. Data from a well from the Las Tres Virgenes Mexican geothermal field are used in this analysis. The results of simulation include temperatures computed during circulation and shut-in, and the latter results are compared with temperatures logged during drilling stoppages. It was found that the thermal disturbance caused by circulation of an air-water mixture has a smaller thermal effect than the thermal disturbance caused by drilling muds

[en] Using slim holes (diameter and lt; 15 cm) for geothermal exploration and small-scale power production can produce significant cost savings compared to conventional rotary-drilling methods. In addition, data obtained from slim holes can be used to lower the risks and costs associated with the drilling and completion of large-diameter geothermal wells. As a prime contractor to the U.S. Department of Energy (DOE), Sandia National Laboratories has worked with industry since 1992 to develop and promote drilling, testing, and logging technology for slim holes. This paper describes the current status of work done both in-house and contracted to industry. It focuses on drilling technology, case histories of slimhole drilling projects, data collection and rig instrumentation, and high-temperature logging tools

[en] Build up of scale deposits on the walls of geothermal wells can occur rapidly due to the high dissolved solids content of geothermal fluids. Scale formation is a significant problem for both the well and for surface heat transfer equipment. Geothermal brines contain a wide variety if dissolved salts including carbonates, silicates, sulfates, and metal sulfides. One technology recently proposed for scale removal is the use of an ultrasonic device. In the present effort we apply cavitation in a more direct manner by the use of acoustically enhanced cavitating water jets which can be made to be much more efficient and aggressive than ultrasonic devices. Cavitating and self-resonating jet technologies have been proven to enhance the erosive power of liquid jets in a number of cutting, cleaning, and drilling applications. In this study we investigated two related technologies - one that employs cavitation and one that breaks the jet up into a series of slugs that produce water hammer type pressures upon impact. These technologies enable operation in both submerged and nonsubmerged conditions

[en] Geothermal steam, often reaching temperatures of 250 deg. to 300 deg. C, always was and is especially now one of the most economical sources of energy. The steam, extracted from wells reaching a depth of 500 m to 1500 m in most cases, is directly conveyed to turbines to produce electricity. However, for a number of reasons, the present development and exploitation of geothermal energy are limited to a few areas in the world, where the existence of high temperature fluids at relatively shallow depths has long been known because of the presence of thermal phenomena at the surface. (author)

[en] Paper generalizes the published data on application of geothermal heat on the basis of various procedures. Paper describes the present-day results of the efforts to develop the domestic geothermal power engineering and to design geothermal power plants. Paper presents the most essential lines of development of heat and power supply based on the geothermal resources available both in Russia and abroad