Economic impact of corrosion and scaling problems in geothermal energy systems
Corrosion and scaling problems have a significant impact on geothermal plant economics. A power plant must amortize the capital investment over a 20-year period and achieve satisfactory operating efficiency to achieve financial success. Corrosion and scale incrustations have been encountered in all geothermal plants, and to various degrees, adversely affected plant life times and power output. Using published data this report analyzes known geothermal corrosion and scaling phenomena for significant cost impacts on plant design and operation. It has been necessary to speculate about causes and mechanisms in order to estimate impacts on conceptual geothermal plants. Silica is highly soluble in hot geothermal water and solubility decreases as water is cooled in a geothermal power plant. Calculations indicate as much as 30,000 tons/year could pass through a 100 MWe water cycle plant. The major cost impact will be on the reinjection well system where costs of 1 to 10 mills/kwhr of power produced could accrue to waste handling alone. On the other hand, steam cycle geothermal plants have a definite advantage in that significant silica problems will probably only occur in hot dry rock concepts, where steam above 250 C is produced. Calculation methods are given for estimating the required size and cost impact of a silica filtration plant and for sizing scrubbers. The choice of materials is significantly affected by the pH of the geothermal water, temperature, chloride, and H{sub s} contents. Plant concepts which attempt to handle acid waters above 180 C will be forced to use expensive corrosion resistant alloys or develop specialized materials. On the other hand, handling steam up to 500 C, and pH 9 water up to 180 C appears feasible using nominal cost steels, typical of today's geothermal plants. A number of factors affecting plant or component availability have been identified. The most significant is a corrosion fatigue problem in geothermal turbines at the Geyser's geothermal plant which is presently reducing plant output by about 10%. This is equivalent to over $3 million per year in increased oil consumption to replace the power. In the course of assessing the cost implications of corrosion and scaling problems, a number of areas of technological uncertainty were identified which should be considered in R and D planning in support of geothermal energy. Materials development with both laboratory and field testing will be necessary. The economic analysis on which this report is based was done in support of an AEC Division of Applied Technology program to assess the factors affecting geothermal plant economics. The results of this report are to be used to develop computer models of overall plant economics, of which corrosion and scaling problems are only a part. The translation of the economic analysis to the report which appears here, was done on AEC Special Studies Funds.
- Research Organization:
- Battelle Pacific Northwest Labs., Richland, Wash. (US)
- Sponsoring Organization:
- Not Available (US)
- DOE Contract Number:
- AT(45-1)-1830
- OSTI ID:
- 5122645
- Report Number(s):
- BNWL-1866; TRN: US200508%%62
- Resource Relation:
- Other Information: PBD: 1 Jan 1975
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
15 GEOTHERMAL ENERGY
29 ENERGY PLANNING
POLICY AND ECONOMY
CALCULATION METHODS
CORROSION FATIGUE
ECONOMIC ANALYSIS
ECONOMIC IMPACT
GEOTHERMAL ENERGY
SCRUBBERS
SILICA
ALUMINIUM ALLOYS
CORROSION
CALCIUM CARBONATES
DEPOSITION
CARBON STEELS
COPPER ALLOYS
GEOTHERMAL POWER PLANTS
SCALING
GEYSERS GEOTHERMAL FIELD
NICKEL ALLOYS
SILICON OXIDES
STAINLESS STEELS
TITANIUM
ZIRCONIUM
CORROSION RESISTANT ALLOYS
CORROSIVE EFFECTS
EQUIPMENT
GEOTHERMAL FLUIDS
INJECTION WELLS
TURBINES
ALKALINE EARTH METAL COMPOUNDS
CALCIUM COMPOUNDS
CARBON COMPOUNDS
CHALCOGENIDES
CHEMICAL REACTIONS
CHROMIUM ALLOYS
ELEMENTS
GEOTHERMAL FIELDS
IRON BASE ALLOYS
OXYGEN COMPOUNDS
SILICON COMPOUNDS
GEOTHERMAL LEGACY
150903* - Geothermal Engineering- Corrosion
Scaling & Materials Development