California Energy Commission 

Public Interest Energy Research Program Report, Project 2.1 Abstract

The Hetch Hetchy Water and Power Division of the San Francisco Public Utilities Commission (Hetch Hetchy/SFPUC) commissioned a study in 2004 to provide a portfolio of well-characterized geothermal resources within California and western Nevada that could supply additional power to the California market.

This study summarizes potential improvements to 45 existing geothermal facilities in California. The improvements are of two general types: improvements in resource supply (pertaining primarily to the wellfield and gathering system) and improvements in surface facilities (pertaining primarily to the plants). The information is presented as matrices of geothermal projects and the potential improvements that may apply to each. The report attempts to resolve inconsistencies in reported plant capacities by distinguishing between original capacity, electromechanical capacity, 2005 capacity (which takes into account resource limitations), and actual annual average power. The total electro-mechanical capacity of the geothermal plants in California is about 2,650 MW-gross, and the 2005 capacity is about 1,850 MW-gross (1,600 MW-net). The difference between the electro-mechanical capacity and the 2005 capacity (about 800 MW) represents the increase in power output that could be achieved if adequate resource supply were available. The difference between the most-likely resource capacity and the electromechanical capacity of existing plants shows the amount of incremental power output that could be achieved by a combination of plant improvements and construction of new plants in already producing fields. Most of the latter type of incremental potential (about 1,400 MW) is in the Salton Sea Field. Despite a surplus of electro-mechanical capacity in some areas of The Geysers, there is still potential for additional plant capacity in The Geysers (probably in the range of 100 to 150 MW). To establish baseline conditions for cost-benefit analysis, this report presents information on capital costs for new geothermal plants and on the operation and maintenance (O&M) cost of existing facilities. As of 2005, the capital cost for new geothermal facilities in California is likely to be in the range of $2,900 to $3,500 per kW installed, including both drilling costs and plant construction. O&M costs are in the range of 1.8 to 2.5 ¢/kWh. This O&M estimate includes labor and benefits, services and supplies, property taxes, royalties and lease payments, insurance, workovers, and site-based administrative costs; depreciation and interest costs are excluded.

Download the full report to learn more.