Renewables

Geothermal Research Could Cut Drilling Costs

Issue 6 and Volume 102.

Geothermal Research Could Cut Drilling Costs

Sandia National Laboratories` Geo thermal Research Department is working to improve the economic feasibility of geothermal energy through experiments with Honeywell silicon-on-insulator electronics. The technology is being used to evaluate and design new electronic instrument systems operating at up to 600 F–more than 212 F hotter than systems presently available. The project is funded by the Department of Energy Office of Geothermal Technologies.

Electronics that can withstand high temperatures would be a cost saver for the geothermal industry. Currently, electronics and batteries used in geo thermal well applications must be encased in a Dewar flask of evacuated double-walled steel. Temperatures in geothermal wells can reach 660 F. Even with the protective flask, instruments generally can only be in a well for about 10 hours before they must be removed. “Every time one of these Dewared instruments is pulled out of the well during drilling, it costs $8,000 to $10,000, ultimately increasing the cost of geothermal energy,” said Randy Normann, project principal investigator.

The longest temperature run of Sandia electronics to date at 572 F has been 72 hours. The test was interrupted to cool the oven to add new experiments. The electronic devices have logged 2,500 hours at 482 F.

Normann anticipates that the use of high-temperature electronics could reduce the cost of geothermal logging tools by $4,500 each, or 20 percent of the total tool cost, by eliminating the Dewar. Additional testing and system development is still needed. p