Author: L. S. ForcellaPublisher:
ISBN:
Category : Geothermal resources
Languages : en
Pages : 0
Book Description
Low temperature geothermal fluid is defined in OAR Chapter 690, Division 65 as any ground water used for its thermal characteristics that is encountered in a well with a bottom hole temperature less than 250°F (121°C). As such, low temperature geothermal resources are considered part of Oregon's ground water resources and are managed by the Oregon Water Resources Department (WRD). Use of ground water for its thermal properties is considered a beneficial use. With current interest in renewable resources and improved technology in heat extraction, the thermal value of ground water at all temperatures has increased dramatically adding to the complexity of ground water management. Higher than normal terrestrial heat flow in the Cascade Mountains, the Basin and Range, Columbia Plateau, Oregon Plateaus and the Snake River Plain Provinces give Oregon outstanding potential for use of geothermal resources. Geothermal energy in Oregon potentially is capable of displacing seven million barrels of fuel oil annually, comprising 27 trillion Btus/year (903 MWe) of electrical energy and 66 trillion Btus/year (2208 MWt) of thermal energy. This is equivalent to the energy produced by six Boardman coal-fired plants (Geothermal Task Force, 1980). In a report for the Pacific Northwest Utilities Conference Committee and the Oregon Energy Facility Siting Council by the Oregon Department of Energy (ODOE), these figures have been updated to 6236 MW of total electrical and thermal power or 12 Boardman coal-fired plants (Brown, 1982). Geothermal resources most commonly are confined to intensely faulted areas where hydrogeologic conditions are favorable for deeply circulated thermal water to rise to land surface. Klamath Falls, Lakeview and Vale are examples of population centers built around active hydrothermal discharge areas. The direct use of geothermal energy for space and process heating in Klamath Falls is the largest application of its kind in the United States. Other areas with potential are the urban areas near the Cascade Mountains such as Portland, Salem, Eugene, Springfield, Oakridge and Hood River, or those of the Oregon Plateau such as Bend, Prineville, Madras and Burns. Other population centers near hydrothermai anomalies are The Dalles, Ontario and La Grande and many rural areas of southeastern Oregon. All these areas have the potential to implement district heating plans that could supply the locale with heat and/or electrical energy. Figure 1 and Table 1 show the geological provinces of the state and the estimated heat available for different areas as determined by the U.S. Geological Survey (USGS) (Reed, 1982). The hotter the ground water, the more attractive it is for development of geothermal resources. However, all ground water contains stored heat. The specific heat of a substance is that quantity of heat required to increase the temperature of a unit weight of that substance 1°C. Water, the standard substance for defining that quantity of heat, has a specific heat of 1.0. With only a few exceptions, water has the highest specific heat of all compounds. Because of this, all aquifers are prime reservoirs of the earth's stored heat energy. Current technology in heat pumps enables heat to be extracted economically, in some areas, from water as low as 40°F (4°C). Some designs of heat exchangers allow heat to be extracted with no withdrawal of water. Earth heat extraction via ground water resources may one day become the dominant method of space heating in the United States. In other applications, binary generators are making electrical generation possible from water as cool as 180°F (82°C). District heating systems have the potential to supply thermal and electrical energy to many customers with significant savings compared to conventional sources of heat and electricity. With ground water now commonly used as a heat source, the diversity of ground water use is compounded. This emphasizes the public policy issue of adequate protection and management for future generations.
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