Direct Heat Applications Research Articles

The industrial exploitation of geothermal resources in Europe

The uses of geothermal energy for industrial purposes can be divided into those associated with electrical power generation and those exploited for direct heat applications. Generally, this division is based on the temperature and deliverability of the available resources. In Europe, each category is related to specific geological conditions. Only four European countries are currently using geothermal resources for power generation: Italy (504 MWe), Turkey (20 MWe), Portugal (Azores, 3 MWe) and Greece (Milos, 2 MWe). All these projects are in areas of major tectonic activity. A variety of geochemical and geotechnical factors influence the nature and size of the resources. Direct use geothermal schemes in Europe are based on a very wide range of geological environments and use temperatures from 15°C upwards. The geological setting of these developments is generally simpler. There is scope for greater development once an improved understanding is gained of the characteristics of fractured formations. This aspect is also central to the Hot Dry Rock problem, and in presenting some results from this work, emphasis is placed on the need to understand stress anisotropy and in situ fluid pressures, and to interpret borehole observations throughout Europe in terms of fracture distributions and connectivity at depths of 4–6 km.

Developments in Geothermal Resources, 1983-1988

Hydrothermal resources, one of the several types of geothermal resources, are being actively developed on a worldwide basis. Other types of geothermal energy--geopressured, hot dry rock, and magma--remain uneconomic but show considerable promise for the future. Technical problems and low energy prices inhibit the development of each of the 4 geothermal types. Geothermal energy is used both for generation of electricity and for direct-heat applications. Use of geothermal energy is desirable because it is an environmentally clean, utility-compatible source of energy that directly displaces the need for more nuclear plants and frees petroleum for other important uses. Current worldwide hydrothermal generating capacity is about 5,457 electrical megawatts (MWe) in 18 countries, with the United States accounting for 2,609 MWe of the total. Current worldwide direct uses of hydrothermal energy amount to about 10,000 thermal megawatts (MWt). Geothermal development in the United States currently is depressed due to comparatively low energy costs and a temporary excess in electrical generating capacity. Because of these factors as well as lack of adequate technology, only a small portion of the known hydrothermal resource base can be used economically today.

Plant design and safety concept of the HTR-module

The new KWU/Interatom concept of a modular High Temperature Reactor is characterized by the fact that several standardized nuclear heat production units, each having a power output up to 200 MW(th), are connected into parallel to obtain a power plant of any desired output for the production of process steam and electricity for the application in district heating and for the direct application of process heat. The safety concept of the modular reactor is such that the reactor plant shall stay in a predictable state and shall not release an excessive amount of fission products into the environment even for hypothetical accidents.

State‐of‐the‐art geophysical exploration for geothermal resources

At the present stage of development, use of geothermal energy saves about 77 million barrels of oil per year worldwide that would otherwise be required for electrical power generation and direct heat applications. More than a dozen countries are involved in development of geothermal resources. Currently, only the moderate‐ and high‐temperature hydrothermal convective type of geothermal system can be economically used for generating electric power. Lower‐temperature resources of several types are being tapped for space heating and industrial processing. Geophysics plays important roles both in exploration for geothermal systems and in delineating, evaluating, and monitoring production from them. The thermal methods, which detect anomalous temperatures directly, and the electrical methods are probably the most useful and widely used in terms of siting drilling targets, but gravity, magnetics, seismic methods, and geophysical well logging all have important application. Advances in geophysical methods are needed to improve cost effectiveness and to enhance solutions of geologic problems. There is no wholly satisfactory electrical system from the standpoint of resolution of subsurface resistivity configuration at the required scale, depth of penetration, portability of equipment, and survey cost. The resolution of microseismic and microearthquake techniques needs improvement, and the reflection seismic technique needs substantial improvement to be cost effective in many hard‐rock environments. Well‐logging tools need to be developed and calibrated for use in corrosive wells at temperatures exceeding 200°C. Well‐log interpretation techniques need to be developed for the hard‐rock environment. Borehole geophysical techniques and geotomography are just beginning to be applied and show promise with future development.

Research and development of geothermal resources in greece: present status and future prospects

Geothermal energy in Greece is attracting attention as a potentially important contributor to the national energy sources. The geological structure of this country is such that favourable conditions exist for geothermal resources. Hydrothermal systems have already been identified on the islands of Milos and Nisyros (Aegean Sea). Results of preliminary production tests in the five existing geothermal wells on Milos can guarantee the operation of geothermal electric condensing units to a total capacity of about 24 MW. The first exploratory wildcat well, drilled on Nisyros (caldera area) to a depth of 1816 m, confirmed the existence of a very high temperature deep reservoir. Integrated interpretation of prospectings carried out in the areas of second priority order (Lesbos, Loutraki-Sousaki, Platystomon, Aedipsos, Poros, etc.) is now under way, aimed at discovering other economically exploitable geothermal fields. The northern part of Greece, where the active tectonics of Macedonia (Strymon Valley and Langadas-Volvi zone) has favoured the existence of medium to low enthalpy geothermal systems, which can be exploited for direct heat applications. By the end of 1984 the first Greek geothermal power plant of 1.5 - 4 MW will be installed on Milos, and by the end of 1986 a 4 – 5 MW pilot plant could be installed on Nisyros, providing the second well proves productive. The maximum geothermal electric potential of Milos has been estimated at 100–200 MW. Therefore the electric energy produced could be transmitted economically from Milos to a significant number of islands in the Aegean Sea and to the mainland by means of a system of a.c. submarine cables by 1992. The availability of local geothermal sources on the islands of the Aegean Sea could thus represent appreciable savings in imported oil.

Investment in Geothermal Direct Heat Applications

An assessment of eight geothermal direct-heat projects for which confident cost and production data exists indicates that low-temperature geothermal resource can, in certain instances, provide an inexpensive, reliable source of direct-heat energy. The analysis examines the retrofit investment decision separately for private firm and local government investors. It compares the economics of geothermal and conventional energy supplies, and explores the sensitivity of these comparative results to changes in the underlying assumptions. Investors are warned that geothermal direct-heat applications projects have not been uniformly successful. Three of the eight projects do not appear to be economical when compared to conventional alternatives even though all eight are the most advanced of 22 demonstration projects originallly funded by DOE. 6 references, 1 figure, 6 tables.

Geothermal prospecting with Shallo‐Temp surveys

The Shallo‐Temp® survey is an inexpensive and rapid “first look” geophysical technique that is useful in planning the more traditional and costly reconnaissance drilling geothermal exploration programs. The technique is based on making many soil temperature measurements at 2-m depths over a given exploration area and correcting these measurements for the effects of elevation and surface geologic and meteorologic conditions. Corrections for surface conditions are made with an “annual wave correction model.” The output from the model is the normally expected 2-m temperature for the given site at the date for which input data were provided. The difference between the measured and computed 2-m temperature data represents effects of geothermal heat flow. A Shallo‐Temp residual map is compared both to a 2-m temperature map for a specific date (September, 1977) and to a mean annual 2-m temperature map for the Coso known geothermal resource area producing the same anomaly pattern in each case. Additional case history studies at Upsal Hogback in Nevada, and Animus Valley in New Mexico provide evidence to support the applicability of the Shallo‐Temp technique throughout the Basin and Range Province. The technique developed is not designed to replace reconnaissance drilling but rather help focus standard reconnaissance programs. The two potentially most reliable applications of the technique are in extending trends where standard reconnaissance holes have been drilled or filling in detail between widely spaced holes, and in surveying for near‐surface anomalies that might be developed for direct heating applications. ®Registered trademark of LeSchack Associates, Ltd.

Roasting, smoking and dieting in response to birth: Malay confinement in cross-cultural perspective

According to humoral medical theory, food and body states may be classified as ‘hot’ or ‘cold’. During periods of physical vulnerability, behavioral and dietary precautions may be invoked for therapeutic and prophylactic purposes following the humoral medical principle of the treatment of opposites. Childbirth in particular affects humoral balance, and in confinement precautions are observed to replace heat lost during parturition and to protect the mother against cold and wind. Women in Asia and Latin America especially share several postpartum precautions, including physical confinement, restrictions on bathing, the prescription of hot and proscription of cold foods; for many women these precautions are supplemented with the direct application of heat, including by ‘mother roasting’, steaming. or smoking. The postpartum precautions, as detailed for Malay women, provide a framework for the management of birth and the ritual and social assumption of motherhood.

Extractable Geothermal Energy in Benue Area, Nigeria: ABSTRACT

An episodic mobile belt underlies the zone of geothermal springs in the Benue area of Nigeria. The close resemblance between the transverse gravity profiles for the Benue depression and profiles of the central Red Sea depression may indicate a similar origin for the depression. The Benue depression is an expression of a spreading ridge generated from a RRR triple junction which was active in the Early Cretaceous. Separation in the Benue trough ceased in the Late Cretaceous, and the spreading ridge is now defunct and at least partly obscured. In Neogene time, there was predominance of igneous activity in the Cameroon-Adamawa volcanic zone which has many attributes of an embryonic spreading ridge. Many of the Neogene alkaline volcanics in the Benue depression and on the Jos plateau trend northwest-southeast, roughly perpendicular to both the Benue depression and the Cameroon-Adamawa volcanic zone, and may mark the sites of future transform faults. It is postulated that the geothermal springs in the Benue area are surface expressions of a convective hydrothermal system associated with an embryonic spreading ridge or hot spot. It is also suggested that extraction of energy from this convective hydrothermal system, either for direct heat application or for conversion to electricity in the Benue area, is feasible. End_of_Article - Last_Page 898------------

Eastern Geothermal Resources: Should We Pursue Them?

A geothermal resource that consists of hot water at moderate temperatures (below 125 degrees C) underlies many areas in the central and eastern United States. Programs funded by the Department of Energy have revealed that this resource is definable and economically competitive with conventional fuels for use in direct heat applications. The resource, therefore, has the potential for reducing our dependence on the imported oil used for space heating. However, front-end costs and risks to explore, drill, test, and evaluate the magnitude of the resource have inhibited development. The question is, therefore, how much federal stimulation will be needed to convince private capital to exploit this widespread low-quality energy source.

Morphological Changes in Adult Tenebrio molitor (Coleoptera: Tenebrionidae) Resulting from Radiofrequency or Heat Treatment of Larvae or Pupae1

Exposure of Tenebrio molitor L., pupae or larvae over 60 days old to 39 megahertz radiofrequency (RF) electric fields resulted in abnormalities in adult cephalic and thoracic appendages. Larval mortality and the appearance of abnormal adult appendages increased in direct proportion with an increase of the RF energy level applied. Similar morphological changes in adult T. molitor were produced by the direct application of heat to the larval appendages. Morphological changes in adult appendages are probably the result of heat injury to the histoblasts during the period of larval growth.

Functional Activity of the Apocrine Sweat Gland in the Goat

1. Functional activity of the apocrine sweat glands in the hairy skin of the goat was investigated. 2. Adrenaline and noradrenaline were always effective in eliciting local sweating, but isopropylnoradrenaline, ephedrine, acetylcholine, mecholyl, carbaminoylcholine, pilocarpine, nicotine, tetramethylammonium, and histamine were usually ineffective. 3. The exposure of the animal body to heat resulted in a spontaneous sweating on the general hairy skin surface, which was blocked by dihydroergotamine in relatively low concentrations and also by atropine in relatively high concetrations. This sweating was abolished or markedly reduced by sympathectomy. 4. Direct application of radiant heat to a restricted skin area induced a localized sweating which was highly resistant to dihydroergotamine, atropine and procaine. 5. The innervation of the goat apocrine glands was discussed. We wish to express our thanks to Professor Masao Wada for his advice and guidance throughout this work and also for performing sympathectomy for us.

A New Type of Radiant Tubular Heater

Abstract The advantages of applying direct radiant heat to both sides of heating coils in tubular furnaces, as compared to the more customary direct application of radiant heat from one side only, is discussed. The operation, construction, and application of a novel radiant-type burner is described which embodies many desirable features. Use of the burner in tubular heaters is discussed and operating data are presented.

The Sun Motor

INDIA, South America, and other countries interested in the employment of sun power for mechanical purposes, have watched with great attention the result of recent experiments in France, conducted by M. Tellier, whose plan of actuating motive engines by the direct application of solar heat has been supposed to be more advantageous than the plan adopted by the writer of increasing the intensity of the solar rays by a series of reflecting mirrors. The published statements that “the heat-absorbing surface” of the French apparatus presents an area of 215 square feet to the action of the sun's rays, and that “the work done has been only 43,360 foot pounds per hour,” furnish data proving that Tellier's invention possesses no practical value.