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Abstract not provided.

This paper describes an 'Annex', or task, that is part of the International Energy Agency's Geothermal Implementing Agreement. Annex 7 is aimed at improving the state of the art in geothermal drilling, and has three subtasks: an international database on drilling cost and performance, a 'best practices' drilling handbook, and collaborative testing among participating countries. Drilling is an essential and expensive part of geothermal exploration, production, and maintenance. High temperature, corrosive fluids, and hard, fractured formations increase the cost of drilling, logging, and completing geothermal wells, compared to oil and gas. Cost reductions are critical because drilling and completing the production and injection well field can account for approximately half the capital cost for a geothermal power project. Geothermal drilling cost reduction can take many forms, e.g., faster drilling rates, increased bit or tool life, less trouble (twist-offs, stuck pipe, etc.), higher per-well production through multilaterals, and others. Annex 7 addresses all aspects of geothermal well construction, including developing a detailed understanding of worldwide geothermal drilling costs, understanding geothermal drilling practices and how they vary across the globe, and development of improved drilling technology. Objectives for Annex 7 include: (1) Quantitatively understand geothermal drilling costs and performance from around the world and identify ways to improve costs, performance, and productivity. (2) Identify and develop new and improved technologies for significantly reducing the cost of geothermal well construction. (3) Inform the international geothermal community about these drilling technologies. (4) Provide a vehicle for international cooperation, collaborative field tests, and data sharing toward the development and demonstration of improved geothermal drilling technology.

Solar Two was a collaborative, cost-shared project between eleven US industry and utility partners and the U. S. Department of Energy to validate molten-salt power tower technology. The Solar Two plant, located east of Barstow, CA, was comprised of 1926 heliostats, a receiver, a thermal storage system and a steam generation system. Molten nitrate salt was used as the heat transfer fluid and storage media. The steam generator powered a 10 MWe, conventional Rankine cycle turbine. Solar Two operated from June 1996 to April 1999. The major objective of the test and evaluation phase of the project was to validate the technical characteristics of a molten salt power tower. This paper describes the significant results from the test and evaluation activities.