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• 1. [Image] Downhole Heat Exchanger for Shallow Geothermal Systems: Performance, Economics and Applicability

  	Heat exchangers located within the wellbore of shallow geothermal resources are presently being used at several locations in the U.S. These heat exchangers are referred to as downhole heat exchangers. ...
  	Citation × Citation Citation Abstract Copy Title: Downhole Heat Exchanger for Shallow Geothermal Systems: Performance, Economics and Applicability Author: Reistad, G. M. Heat exchangers located within the wellbore of shallow geothermal resources are presently being used at several locations in the U.S. These heat exchangers are referred to as downhole heat exchangers. Such installations can have thermal energy output capacities as high as 1 MW for space heating with source water temperature of 90 to 100°C. This work reports on the performance and economics of downhole heat exchangers relative to the alternative geothermal system which pumps the fluid out of the ground and uses heat exchangers located at the earth's surface. Results indicate that the downhole heat exchange systems for capacity requirements less than about 500 to 100 kW are in general more desirable than the surface heat exchange systems for low capacity (less than about 500 to 1000 kW) requirements and shallow geothermal resources. For higher capacities the surface heat exchange systems become more economical. Furthermore, for large depths, the high capacities available from the surface systems are required in order to make the geothermal energy competitive with other sources Title: Downhole Heat Exchanger for Shallow Geothermal Systems: Performance, Economics and Applicability Author: Reistad, G. M. Heat exchangers located within the wellbore of shallow geothermal resources are presently being used at several locations in the U.S. These heat exchangers are referred to as downhole heat exchangers. Such installations can have thermal energy output capacities as high as 1 MW for space heating with source water temperature of 90 to 100°C. This work reports on the performance and economics of downhole heat exchangers relative to the alternative geothermal system which pumps the fluid out of the ground and uses heat exchangers located at the earth's surface. Results indicate that the downhole heat exchange systems for capacity requirements less than about 500 to 100 kW are in general more desirable than the surface heat exchange systems for low capacity (less than about 500 to 1000 kW) requirements and shallow geothermal resources. For higher capacities the surface heat exchange systems become more economical. Furthermore, for large depths, the high capacities available from the surface systems are required in order to make the geothermal energy competitive with other sources Close

• 2. [Image] Subsurface investigations at the Roosevelt KGRA, Utah. Final report

  	An investigation of the geothermal reservoir in the Roosevelt Hot Springs Known Geothermal Resource Area in Utah was carried out. The objective of this effort was to develop predictions for well production ...
  	Citation × Citation Citation Abstract Copy Title: Subsurface investigations at the Roosevelt KGRA, Utah. Final report Author: Butz, J. Year: 1979 An investigation of the geothermal reservoir in the Roosevelt Hot Springs Known Geothermal Resource Area in Utah was carried out. The objective of this effort was to develop predictions for well production capacities, based on data taken during field tests and through use of a computer model. In turn, the production information could then be used in design optimization and economic analyses for development of the resource under study. Flow tests of a geothermal well, Utah State 14-2, were conducted. Data consisting of pressure and temperature logs as a function of depth were obtained. Maximum recorded temperature was 503/sup 0/F (262/sup 0/C) and maximum pressure, 954 psia (6.58MPa) as measured under flow conditions. Tests were run at rates up to 580,000 lb/hr (73.3 kg/sec) total flow. The information gathered during the testing was reduced and compared to results of a predictive computer model. Reservoir conditions in the Roosevelt Hot Springs KGRA are such that two-phase flow exists in the wellbore and, in some cases, also in the reservoir itself. The computer model employed in the analysis reflects current efforts to improve the state-of-the-art in the prediction of two-phase pressure drops in vertical systems. Predictions at flowrates of up to 300,000 lb/hr (38 kg/sec) matched quite well with test data, while modeling at higher flowrates (to maximum tested) showed progressively greater deviation from test data. Cause of the observed degradation is postulated to be the movement of the flash horizon into the reservoir, due to drawdown at high flowrates; DOE/ET/28389-1 Title: Subsurface investigations at the Roosevelt KGRA, Utah. Final report Author: Butz, J. Year: 1979 An investigation of the geothermal reservoir in the Roosevelt Hot Springs Known Geothermal Resource Area in Utah was carried out. The objective of this effort was to develop predictions for well production capacities, based on data taken during field tests and through use of a computer model. In turn, the production information could then be used in design optimization and economic analyses for development of the resource under study. Flow tests of a geothermal well, Utah State 14-2, were conducted. Data consisting of pressure and temperature logs as a function of depth were obtained. Maximum recorded temperature was 503/sup 0/F (262/sup 0/C) and maximum pressure, 954 psia (6.58MPa) as measured under flow conditions. Tests were run at rates up to 580,000 lb/hr (73.3 kg/sec) total flow. The information gathered during the testing was reduced and compared to results of a predictive computer model. Reservoir conditions in the Roosevelt Hot Springs KGRA are such that two-phase flow exists in the wellbore and, in some cases, also in the reservoir itself. The computer model employed in the analysis reflects current efforts to improve the state-of-the-art in the prediction of two-phase pressure drops in vertical systems. Predictions at flowrates of up to 300,000 lb/hr (38 kg/sec) matched quite well with test data, while modeling at higher flowrates (to maximum tested) showed progressively greater deviation from test data. Cause of the observed degradation is postulated to be the movement of the flash horizon into the reservoir, due to drawdown at high flowrates; DOE/ET/28389-1 Close

• 3. [Image] Advanced Design and Economic Considerations for Commercial Geothermal Power Plants at Heber and Niland, California. Final Report

  	Two separate studies, involving advanced design and economic considerations for commercial geothermal power plants using liquid-dominated hydrothermal resources, are presented. In the first study, the ...
  	Citation × Citation Citation Abstract Copy Title: Advanced Design and Economic Considerations for Commercial Geothermal Power Plants at Heber and Niland, California. Final Report Author: Bechtel Corporation Year: 1977 Two separate studies, involving advanced design and economic considerations for commercial geothermal power plants using liquid-dominated hydrothermal resources, are presented. In the first study, the effects on design, capital cost, and bus bar electric energy production cost caused by an anticipated decline in available geothermal fluid temperature over the lifetime of power plants are described. A two-stage, flashed-steam energy conversion process was used for the conceptual design of the power plants, which operate from the moderate-temperature, low-salinity reservoir at Heber, California. Plants with net capacities of 50, 100, and 200 MWe (net) were investigated. The results show that it is important to include provision for geothermal fluid temperature decline in the design of power plants to prevent loss of electric energy production capability and to reduce bus bar electric energy costs. In the second study, the technical, economic, and environmental effects of adding regeneration to a 50 MWe (net) power plant employing the multistage-flash/binary process are described. Regeneration is potentially attractive because it recovers waste heat from the turbine exhaust and uses it in the power cycle. However, the pressure drop caused by the introduction of the regenerator decreases the turbine expansion and thus decreases system performance. An innovative approach was taken in the design of the regenerator, which minimized the expected performance degradation of the turbine. The result was that the performance, capital cost, and bus bar electric energy production cost are nearly the same for the processes with and without regeneration. On the other hand, the addition of regeneration has the environmental benefits of substantially reducing heat rejection to the atmosphere and cooling tower makeup and blowdown water requirements. It also increases the temperature of the brine returned to the field for reinjection Title: Advanced Design and Economic Considerations for Commercial Geothermal Power Plants at Heber and Niland, California. Final Report Author: Bechtel Corporation Year: 1977 Two separate studies, involving advanced design and economic considerations for commercial geothermal power plants using liquid-dominated hydrothermal resources, are presented. In the first study, the effects on design, capital cost, and bus bar electric energy production cost caused by an anticipated decline in available geothermal fluid temperature over the lifetime of power plants are described. A two-stage, flashed-steam energy conversion process was used for the conceptual design of the power plants, which operate from the moderate-temperature, low-salinity reservoir at Heber, California. Plants with net capacities of 50, 100, and 200 MWe (net) were investigated. The results show that it is important to include provision for geothermal fluid temperature decline in the design of power plants to prevent loss of electric energy production capability and to reduce bus bar electric energy costs. In the second study, the technical, economic, and environmental effects of adding regeneration to a 50 MWe (net) power plant employing the multistage-flash/binary process are described. Regeneration is potentially attractive because it recovers waste heat from the turbine exhaust and uses it in the power cycle. However, the pressure drop caused by the introduction of the regenerator decreases the turbine expansion and thus decreases system performance. An innovative approach was taken in the design of the regenerator, which minimized the expected performance degradation of the turbine. The result was that the performance, capital cost, and bus bar electric energy production cost are nearly the same for the processes with and without regeneration. On the other hand, the addition of regeneration has the environmental benefits of substantially reducing heat rejection to the atmosphere and cooling tower makeup and blowdown water requirements. It also increases the temperature of the brine returned to the field for reinjection Close