Economic Studies, Sperry Low Temperature Geothermal Conversion System - Phase I and Phase II, Final Report, Volume VI
At the time that the analyses contained in this volume were performed, the avoided energy costs of California's regulated electric utilities were at historic highs and were projected to continue to increase at double-digit annual rates. Since that time, oil prices have slipped, the general rate of inflation has abated, domestic electric power consumption has fallen short of expectations, and a host of other economic elements have shifted in directions which have resulted in substantial reductions in current California avoided energy costs. The question of whether these changes are merely short-term aberrations or represent a fundamental shift in the long-term energy supply and demand balance is beyond the scope of this report. Although the present depressed avoided electric energy prices are not consistent with the projections on which this report's analyses are based, a fact which results in significant discrepancies between the absolute financial returns predicted and those achievable under current circumstances, the comparative results of the study remain valid. The basic thrust of the studies represented in this report was to compare the overall economics of the Gravity Head system with that of optimized conventional binary generating plants. The study is site-specific to the East Mesa geothermal reservoir. It begins with an analysis of optimum individual well production based on the known characteristics of the reservoir. The limiting factors at East Mesa are reservoir drawdown and maximum practical brine pump impeller setting depth. The individual-well production limit is achieved when brine pressure at the pump inlet is reduced to the point at which CO{sub 2} starts to come out of solution, and fouling and impeller cavitation become imminent. The optimum pumping rate was found to be 1300 gpm (at 360 F density) and required that the Gravity Head pump impeller be set 2,033 feet below grade. The required conventional plant pump setting was 1,887 feet below grade, a depth which is probably at the practical limit for shaft-driven conventional pumps. Using the 1300 gpm, 360 F resource as a starting point, detailed cost estimates and performance calculations were made for the Gravity Head and various conventional alternative well-head systems. The most cost effective of the conventional alternatives was found to be a 700 psi cycle using R114 as the working fluid (actually optimized at 682 psi). That system produced 3,805 kW busbar net vs. 4,995 kW busbar net for the Gravity Head unit. Since both the Gravity Head and conventional binary plant cost estimates for commercially mature units came out roughly equal, it was obvious that the Gravity Head system would produce more attractive financial returns--it became a question of degree. The study is in two parts. In Part I, emphasis is placed on the economic sensitivities of the compared systems to variations in capital cost, O&M cost, avoided energy inflation rates, and brine cost. In Part II, a somewhat more rigorous attempt is made to derive the actual economic performance of the systems under more realistic circumstances with contingencies, cost penalties, and multiple-unit developments added.
- Research Organization:
- Sperry Research Center, Sudbury, MA
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC03-78ET27125; AC03-79-ET27131
- OSTI ID:
- 891604
- Report Number(s):
- SRC-CR-83-43; TRN: US200622%%522
- Country of Publication:
- United States
- Language:
- English
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