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Performance and operational experience of a prototype binary geothermal power plant

Description: At the Raft River geothermal site in south central Idaho, the Idaho National Engineering Laboratory is investigating and demonstrating the production of electrical power from a moderate temperature (140/sup 0/ to 145/sup 0/C) geothermal resource. The initial production of electrical power at the Raft River site was accomplished with the Prototype Power Plant which was built to investigate and demonstrate the operation of binary power cycles where the energy in the geothermal fluid is transferred to a secondary working fluid. This plant serves as a test bed for testing pilot scale components, systems, and/or concepts that have the potential for enhancing the feasibility of power generation from moderate temperature geothermal resources. During the automatic run test the plant was able to produce a maximum of 59kW(e). Although the plant was not (and has not) operated at design turbine conditions, performance was predictable. During the automatic run test, the plant operation was stable and the facility was operated for 1357 hours producing electrical power approximately 87% of the time geothermal fluid was available for operation.
Date: January 1, 1981
Creator: Mines, G.L.
Partner: UNT Libraries Government Documents Department

Operation of Mammoth Pacific`s MP1-100 turbine with metastable, supersaturated expansions

Description: INEL`s Heat Cycle Research project continues to develop a technology base for increasing use of moderate-temperature hydrothermal resources to generate electrical power. One concept is the use of metastable, supersaturated turbine expansions. These expansions support a supersaturated working fluid vapor; at equilibrium conditions, liquid condensate would be present during the turbine expansion process. Studies suggest that if these expansions do not adversely affect the turbine performance, up to 8-10% more power could be produced from a given geothermal fluid. Determining the impact of these expansions on turbine performance is the focus of the project investigations being reported.
Date: January 1, 1996
Creator: Mines, G.L.
Partner: UNT Libraries Government Documents Department

Advanced binary geothermal power plants working fluid property determination and heat exchanger design

Description: The performance of binary geothermal power plants can be improved through the proper choice of a working fluid, and optimization of component designs and operating conditions. This paper reviews the investigations at the Idaho National Engineering Laboratory (INEL) which are examining binary cycle performance improvements for moderate temperature (350 to 400 F) resources with emphasis on how the improvements may be integrated into design of binary cycles. These investigations are examining performance improvements resulting from the supercritical vaporization of mixed hydrocarbon working fluids and achieving countercurrent integral condensation with these fluids, as well as the modification of the turbine inlet state points to achieve supersaturated turbine vapor expansions. For resources where the brine outlet temperature is restricted, the use of turbine exhaust recuperators is examined. The baseline plant used to determine improvements in plant performance (characterized by the increase in the net brine effectiveness, watt-hours per pound of brine) in these studies operates at conditions similar to the 45 MW Heber binary plant. Through the selection of the optimum working fluids and operating conditions, achieving countercurrent integral condensation, and allowing supersaturated vapor expansions in the turbine, the performance of the binary cycle (the net brine effectiveness) can be improved by 25 to 30% relative to the baseline plant. 15 refs., 7 figs.
Date: January 1, 1989
Creator: Bliem, C.J. & Mines, G.L.
Partner: UNT Libraries Government Documents Department

Relative performance of supercritical binary geothermal power cycles with in-tube condensors in different orientations

Description: The Heat Cycle Research Program, which is conducted for the Department of Energy, has as its objective the development of the technology for effecting the improved utilization of moderate temperature geothermal resources. The current testing involves the investigation of the performance of binary power cycles utilizing mixtures of non-adjacent hydrocarbons as the working fluids, with supercritical vaporization and in-tube condensation. The utilization of these concepts will improve the net geofluid effectiveness (net plant output per unit mass of geofluid) about 20% over that of a conventional binary power plant. The major prerequisite for this improvement is the achievement of integral, countercurrent condensation. Results are presented for testing of the performance of the condenser at different tube inclinations. The performance in the vertical orientation is better than in either the horizontal or inclined orientations. 7 refs., 8 figs.
Date: January 1, 1989
Creator: Bliem, C.J. & Mines, G.L.
Partner: UNT Libraries Government Documents Department

Overview of recent activities in the Heat Cycle Research Program

Description: The Heat Cycle Research Program, which is being conducted for the Department of Energy, has as its objective the development of the technology for effecting the improved utilization of moderate temperature geothermal resources. To meet this objective, the program has as one of its goals to improve the performance of geothermal binary cycles to levels approaching the practicable thermodynamic maximum. In pursuit of this goal, tests are being conducted at the Heat Cycle Research Facility located at the DOE Geothermal Test Facility, East Mesa, California. The current testing involves the investigation of binary power cycle performance utilizing mixtures of non-adjacent hydrocarbons as the working fluids, with supercritical vaporization and in-tube condensation of the working fluid. In addition to the present test program, preparations are being made to investigate the binary cycle performance improvements which can be achieved by allowing supersaturated vapor expansions in the turbine. These efforts are anticipated to verify that through the utilization of these advanced power cycle concepts and allowing the supersaturated turbine expansions, improvements of up to 28% in the net geofluid effectiveness (net watt hours plant output per pound of geofluid) over conventional binary power plants can be achieved. Results presented for the recent testing, including those tests examining the performance of the countercurrent condenser at different tube inclinations, support the assumptions used in projected performance improvements. 3 refs., 9 figs.
Date: January 1, 1987
Creator: Bliem, C.J. & Mines, G.L.
Partner: UNT Libraries Government Documents Department

Thermal and hydraulic performance of a sieve-tray direct-contact heat exchanger

Description: Experiments investigating the thermal and hydraulic performance of a sieve tray direct contact heat exchanger (DCHX) were conducted using a 275/sup 0/ geothermal fluid as an energy source and different hydrocarbons as working fluids. The baseline performance tests with the direct contact unit were conducted with isobutane. The thermal performance of the unit met or exceeded the design goals for individual tray thermal efficiencies and pinch points. Hydraulically the column operated near recommended design fluid velocities. Following the completion of these tests, the DCHX was operated with different mixtures of hydrocarbon working fluids. Different combinations of the isobutane/hexane family were tested followed by a series with propane/isopentane fluids. The testing conducted with the direct contact unit showed that the sieve tray column is a very efficient heat exchange device although some degradation in boiling tray efficiency and column throughput were noted when mixtures were used.
Date: January 1, 1983
Creator: Mines, G.L. & Wiggins, D.J.
Partner: UNT Libraries Government Documents Department

Advanced Binary Geothermal Power Plancts Working Fluid Property Determination and Heat Exchanger Design

Description: The performance of binary geothermal power plants can be improved through the proper choice of a working fluid, and optimization of component designs and operating conditions. This paper reviews the investigations at the Idaho National Engineering Laboratory (INEL) which are examining binary cycle performance improvements: for moderate temperature (350 to 400 F) resources with emphasis on how the improvements may be integrated into design of binary cycles. These investigations are examining performance improvements resulting from the supercritical vaporization of mixed hydrocarbon working fluids and achieving countercurrent integral condensation with these fluids, as well as the modification of the turbine inlet state points to achieve supersaturated turbine vapor expansions. For resources where the brine outlet temperature is restricted, the use of turbine exhaust recuperators is examined. The baseline plant used to determine improvements in plant performance (characterized by the increase in the net brine effectiveness, watt-hours per pound of brine) in these studies operates at conditions similar to the 45 MW Heber binary plant. Through the selection of the optimum working fluids and operating conditions, achieving countercurrent integral condensation, and allowing supersaturated vapor expansions in the turbine, the performance of the binary cycle (the net brine effectiveness) can be improved by 25 to 30% relative to the baseline plant. The design of these supercritical Rankine-cycle (Binary) power plants for geothermal resources requires information about the potential working fluids used in the cycle. In addition, methods to design the various components, (e.g., heat exchangers, pumps, turbines) are needed. This paper limits its view of component design methods to the heat exchangers in binary power plants. The design of pumps and, turbines for these working fluids presents no new problems to the turbine manufacturer. However, additional work is proceeding at the Heat Cycle Research Facility to explore metastable expansions within turbines. This work, ...
Date: March 21, 1989
Creator: Bliem, C.J. & Mines, G.L.
Partner: UNT Libraries Government Documents Department

Supersaturated Turbine Expansions for Binary Geothermal Power Plants

Description: The Heat Cycle Research project is developing the technology base that will permit a much greater utilization of the moderate-temperature, liquid-dominated geothermal resources, particularly for the generation of electrical power. The emphasis in the project has been the improvement of the performance of binary power cycles. The investigations have been examining concepts projected to improve the brine utilization by 20% relative to a ''Heber-type'' binary plant; these investigations are nearing completion. preparations are currently underway in the project to conduct field investigations of the condensation behavior of supersaturated turbine expansions. These investigations will evaluate whether the projected additional 8% to 10% improvement in brine utilization can be realized by allowing these expansions. Future program efforts will focus on the problems associated with heat rejection and on the transfer of the technology being developed to industry.
Date: March 24, 1992
Creator: Bliem, C.J. & Mines, G.L.
Partner: UNT Libraries Government Documents Department

Advanced binary geothermal power plants: Limits of performance

Description: The Heat Cycle Research Program is investigating potential improvements to power cycles utilizing moderate temperature geothermal resources to produce electrical power. Investigations have specifically examined Rankine cycle binary power systems. Binary Rankine cycles are more efficient than the flash steam cycles at moderate resource temperature, achieving a higher net brine effectiveness. At resource conditions similar to those at the Heber binary plant, it has been shown that mixtures of saturated hydrocarbons (alkanes) or halogenated hydrocarbons operating in a supercritical Rankine cycle gave improved performance over Rankine cycles with the pure working fluids executing single or dual boiling cycles or supercritical cycles. Recently, other types of cycles have been proposed for binary geothermal service. This report explores the feasible limits on efficiency of a plant given practical limits on equipment performance and discusses the methods used in these advanced concept plants to achieve the maximum possible efficiency. (Here feasible is intended to mean reasonably achievable and not cost-effective.) No direct economic analysis has been made because of the sensitivity of economic results to site specific input. The limit of performance of three advanced plants were considered in this report. The performance predictions were taken from the developers of each concept. The advanced plants considered appear to be approaching the feasible limit of performance. Ultimately, the plant designer must weigh the advantages and disadvantages of the the different cycles to find the best plant for a given service. In addition, this report presents a standard of comparison of the work which has been done in the Heat Cycle Research Program and in the industrial sector by Exergy, Inc. and Polythermal Technologies. 18 refs., 16 figs., 1 tab.
Date: January 1, 1991
Creator: Bliem, C.J. & Mines, G.L.
Partner: UNT Libraries Government Documents Department

Overview of the Heat Cycle Research project

Description: The Heat Cycle Research project is developing the technology base that will permit a much greater utilization of the moderate- temperature, liquid-dominated geothermal resources, particularly for the generation of electrical power. The emphasis in the project has been the improvement of the performance of binary power cycles. The investigations have been examining concepts projected to improve the brine utilization by 20% relative to a Heber-type'' binary plant; these investigations are nearing completion. Preparations are currently underway in the project to conduct field investigations of the condensation behavior of supersaturated turbine expansions. These investigations will evaluate whether the projected additional 8% to 10% improvement in brine utilization can be realized by allowing these expansions. Analytical studies of an ideal'' cycle's performance have shown that the concepts under project investigation, are approaching the practical limits of performance. Future program efforts will focus on the problems associated with heat rejection and on the transfer of the technology being developed to industry. 10 refs., 6 figs.
Date: January 1, 1991
Creator: Bliem, C.J. & Mines, G.L.
Partner: UNT Libraries Government Documents Department

Thermal and hydraulic performance tests of a sieve-tray direct-contact heat exchanger vaporizing pure and mixed-hydrocarbon Rankine-cycle working fluids

Description: Experiments investigating a sieve-tray direct-contact heat exchanger were conducted at the Raft River Geothermal Test Site in southeastern Idaho using the 60-kW Mobile Heat Cycle Research Facility operating in the thermal loop mode (without a turbine). Isobutane, propane, and several hydrocarbon mixtures were heated and boiled in the direct-contact column, which is approx. 12 in. in diameter and 19-1/2 ft. high, using the energy from a 280/sup 0/F geothermal resource. Using pure fluids, isobutane or propane, the column operated much as intended, with 17 trays used for preheating and one or two accomplishing the boiling. For the pure fluids, individual tray efficiencies were found to be 70% or higher for preheating, and close to 100% for boiling; column pinch points were projected to be well under 1/sup 0/F with some runs reaching values as low as approx. 0.02/sup 0/F. Maximum geofluid throughputs for the isobutane tests corresponded roughly to the terminal rise velocity of a 1/32 in. working fluid droplet in geofluid. Boiling was found to occur in as many as 12 trays for the mixtures having the highest concentrations of the minor component, with overall efficiencies in the boiling section estimated on the order of 25 or 30%. Preheating tray efficiencies appeared to be fairly independent of working fluid, with pinch points ranging from as low as approx. 0.03/sup 0/F for a 0.95 isobutane/0.05 hexane mixture to approx. 2.3/sup 0/F for a 0.85 isobutane/0.05 hexane mixture. Column operation was noticeably less stable for the mixtures than for the pure fluids, with maximum throughputs dropping to as low as 40 to 50% of those for the pure fluids.
Date: August 1, 1983
Creator: Mines, G.L.; Demuth, O.J. & Wiggins, D.J.
Partner: UNT Libraries Government Documents Department

Geothermal heat cycle research: Supercritical cycle with horizontal counterflow condenser

Description: The Heat Cycle Research Program, which is being conducted for the Department of Energy, has as its objective the development of the technology for effecting the improved utilization of moderate temperature geothermal resources. To meet this objective, the program has as one of its goals to improve the performance of geothermal binary cycles to levels approaching the practicable thermodynamic maximum. In pursuit of this goal, tests are being conducted at the Heat Cycle Research Facility located at the DOE Geothermal Test Facility, East Mesa, California. The current testing involves the investigation of binary power cycle performance utilizing mixtures of non-adjacent hydrocarbons as the working fluids, with supercritical vaporization and in-tube condensation of the working fluid. In addition to the present test program, preparations are being made to investigate the binary cycle performance improvements which can be achieved by allowing supersaturated vapor expansions in the turbine. These efforts are anticipated to verify that through the utilization of these advanced power cycle concepts and allowing the supersaturated turbine expansions, improvements of up to 28% in the net geofluid effectiveness (net watt hours plant output per pound of geofluid) over conventional binary power plants can be achieved. Results are presented for the recent testing including those tests examining the performance of the countercurrent condenser at different tube inclinations. Performance of the heaters and the condenser in a vertical orientation can be predicted well with existing methods and data. The condenser in its near horizontal orientation performs slightly worse than in its vertical orientation. Some problems have been encountered in predicting the performance in the horizontal orientation. There is no evidence of departure from integral condensation in either orientation.
Date: January 1, 1987
Creator: Mines, G.L.; Swank, W.D. & Bliem, C.J.
Partner: UNT Libraries Government Documents Department

Parametric Sensitivity Study of Operating and Design Variables in Wellbore Heat Exchangers

Description: This report documents the results of an extensive sensitivity study conducted by the Idaho National Engineering and Environmental Laboratory. This study investigated the effects of various operating and design parameters on wellbore heat exchanger performance to determine conditions for optimal thermal energy extraction and evaluate the potential for using a wellbore heat exchanger model for power generation. Variables studied included operational parameters such as circulation rates, wellbore geometries and working fluid properties, and regional properties including basal heat flux and formation rock type. Energy extraction is strongly affected by fluid residence time, heat transfer contact area, and formation thermal properties. Water appears to be the most appropriate working fluid. Aside from minimal tubing insulation, tubing properties are second order effects. On the basis of the sensitivity study, a best case model was simulated and the results compared against existing low-temperature power generation plants. Even assuming ideal work conversion to electric power, a wellbore heat exchange model cannot generate 200 kW (682.4e+3 BTU/h) at the onset of pseudosteady state. Using realistic conversion efficiency, the method is unlikely to generate 50 kW (170.6e+3 BTU/h).
Date: May 1, 2004
Creator: Nalla, G.; Shook, G.M.; Mines, G.L. & Bloomfield, K.K.
Partner: UNT Libraries Government Documents Department

Summary of investigations of the use of modified turbine inlet conditions in a binary power plant

Description: Investigators at the Idaho National Engineering and Environmental Laboratory (INEEL) are developing technologies that will enhance the feasibility of generating electrical power from a hydrothermal resource. One of the concepts investigated is the use of modified inlet conditions in geothermal binary power plant turbines to increase the power generation. An inlet condition of interest allows the expanding vapor to enter the two-phase region, a mode of operation typically avoided because of concern that condensate would form and damage the turbine, degrading performance. INEEL investigators postulated that initially a supersaturated vapor would be supported, and that no turbine damage would occur. This paper summarizes the investigation of these expansions that began with testing of their condensation behavior, and culminated with the incorporation of these expansions into the operation of several commercial binary plant turbines.
Date: September 24, 2000
Creator: Mines, G. L.
Partner: UNT Libraries Government Documents Department

Evaluation of the Impact of Off-Design Operation on an Air-Cooled Binary Power Plant

Description: Geothermal power plants are designed and constructed to provide a rated power output at specific resource and ambient conditions. Due to both diurnal and seasonal changes in the ambient air temperature, as well as a decline in resource productivity over time, plants seldom operate at these ''design'' conditions. This paper examines the impact of ''off- design'' operation of an air-cooled binary geothermal power plant. An available energy analysis is used to evaluate operation at these conditions. This evaluation identifies those portions of the power cycle that are most sensitive to changing resource and ambient conditions, as well as where improvements in cycle component or system performance would have the largest impact in increasing power output.
Date: June 17, 2002
Creator: Mines, G.L.
Partner: UNT Libraries Government Documents Department

Vaporization at supercritical pressures and counterflow condensing of pure and mixed-hydrocarbon working fluids for geothermal power plants

Description: The Heat Cycle Research Program has as its objective the development of the technology for effecting improved utilization of moderate temperature geothermal resources. Current testing involves supercritical vaporization and counterflow in-tube condensing in an organic Rankine cycle. Results of the experiments are given for both pure and mixed-hydrocarbon working fluids. The heater and condenser behavior predicted by the Heat Transfer Research, Inc. computer codes used for correlation of the data was in excellent agreement with experimental results. A special series of tests, conducted with propane and up to approximately 40% isopentane concentration indicated that a close approach to ''integral'' condensation was occurring in the vertically-oriented condenser.
Date: January 1, 1986
Creator: Bliem, C.J.; Demuth, O.J.; Mines, G.L. & Swank, W.D.
Partner: UNT Libraries Government Documents Department

Overview of recent supercritical binary geothermal cycle experiments from the Heat Cycle Research Program

Description: The Heat Cycle Research Program, which is being conducted for the Department of Energy, has as its objective the development of the technology for effecting improved utilization of moderate temperature geothermal resources. Testing at the Heat Cycle Research Facility located at the DOE Geothermal Test Facility East Mesa, California involves supercritical vaporization and counterflow in-tube condensing in an organic Rankine cycle. Results of the experiments are given for both pure and mixed-hydrocarbon working fluids. The heater and condenser behavior predicted by the Heat Transfer Research, Inc. computer codes used for correlation of the data was in excellent agreement with experimental results. A special series of tests, conducted with propane and up to approximately 40% isopentane concentration, indicated that a close approach to ''integral'' condensation was occurring in the vertically-oriented condenser. Preliminary results of tests in which the turbine expansion ''passed through the two-phase region'' did not indicate efficiency degradation assignable to these metastable expansion processes.
Date: January 1, 1986
Creator: Demuth, O.J.; Bliem, C.J.; Mines, G.L. & Swank, W.D.
Partner: UNT Libraries Government Documents Department

Geothermal heat cycle research supercritical cycle with counterflow condenser in different orientations

Description: The Heat Cycle Research Program, which is conducted for the Department of Energy, has as its objective the development of the technology for effecting the improved utilization of moderate temperature geothermal resources. The current testing involves the investigation of binary power cycle performance utilizing mixtures of non-adjacent hydrocarbons as the working fluids, with supercritical vaporization and in-tube condensation of the working fluid. The utilization of these concepts verified here will improve the net geofluid effectiveness (net watt hours plant output per pound of geofluid) about 20% over that of a conventional binary power plant. The major effect in this improvement is the ability to achieve integral, countercurrent condensation. Results are presented for the recent testing including those tests examining the performance of the countercurrent condenser at different tube inclinations and comparison with new design-base computer programs. 9 refs., 9 figs.
Date: January 1, 1988
Creator: Bliem, C.J. & Mines, G.L.
Partner: UNT Libraries Government Documents Department

Supercritical binary geothermal cycle experiments with mixed-hydrocarbon working fluids and a vertical, in-tube, counterflow condenser

Description: The objective is improved utilization of moderate temperature geothermal resources. Current testing involves supercritical vaporization and counterflow in-tube condensing in an organic Rankine cycle. This report presents a description of the test facility and results from a part of the program in which the condenser was oriented in a vertical attitude. Results of the experiments for the supercritical heaters and the countercurrent, vertical, in-tube condenser are given for both pure and mixed-hydrocarbon working fluids. The heater and condenser behavior predicted by the Heat Transfer Research, Inc. computer codes used for correlation of the data was in excellent agreement with experimental results. A special series of tests, conducted with propane and up to approximately 40% isopentane concentration, indicated that a close approach to ''integral'' condensation was occurring in the vertically-oriented condenser.
Date: December 1, 1985
Creator: Demuth, O.J.; Bliem, C.J.; Mines, G.L. & Swank, W.D.
Partner: UNT Libraries Government Documents Department

Design Considerations for Artificial Lifting of Enhanced Geothermal System Fluids

Description: This work evaluates the effect of production well pumping requirements on power generation. The amount of work that can be extracted from a geothermal fluid and the rate at which this work is converted to power increase as the reservoir temperature increases. Artificial lifting is an important issue in this process. The results presented are based on a configuration comprising one production well and one injection well, representing an enhanced geothermal system. The effects of the hydraulic conductivity of the geothermal reservoir, the flow rate, and the size of the production casing are considered in the study. Besides submersible pumps, the possibility of using lineshaft pumps is also discussed.
Date: July 1, 2005
Creator: Xie, Xina; Bloomfield, K. K.; Mines, G. L. & Shook, G. M.
Partner: UNT Libraries Government Documents Department

Simple strategies for minimization of cooling water usage in binary power plants

Description: The geothermal resources which could be used for the production of electrical power in the United States are located for the most part in the semi-arid western regions of the country. The availability of ground or surface water in the quantity or quality desired for a conventional wet'' heat rejections system represents a barrier to the development of these resources with the binary cycle technology. This paper investigates some simple strategies to minimize the cooling water usage of binary power plants. The cooling water usage is reduced by increasing the thermal efficiency of the plant. Three methods of accomplishing this are considered here: increasing the average source temperature, by increasing the geofluid outlet temperature; decreasing pinch points on the heat rejection heat exchangers, increasing their size; and using internal recuperation within the cycle. In addition to the impact on water usage, the impact on cost-of-electricity is determined. The paper shows that some of these strategies can reduce the cooling water requirements 20 to 30% over that for a plant similar to the Heber Binary Plant, with a net reduction in the cost-of-electricity of about 15%. 13 refs., 4 figs., 3 tabs.
Date: January 1, 1989
Creator: Bliem, C.J. & Mines, G.L. (EG and G Idaho, Inc., Idaho Falls, ID (USA))
Partner: UNT Libraries Government Documents Department