Collaboration in Civic Spheres

State seeks bids on more probes for geothermal energy

by Henry Apfel May 25th, 2012

The State of Washington’s Department of Natural Resources is seeking bidders for drilling exploratory geothermal boreholes in Skamania and Klickitat counties at up to five of six targeted sites that have passed environmental muster: Swift Creek, Northwood and Wind River in Skamania County; and Laurel, Outlet Creek, and Box Canyon Quarry in Klickitat County. (Coordinates table; map.) Each borehole would be six inches in diameter and reach a depth of 700 feet, although the drilling would not require construction of new roads or other major infrastructure alterations. Their purpose would be to determine the extent of geothermal energy at the sites, rather than to generate power. The winning bid will likely be selected the week of June 4th, and drilling of the new probes is scheduled to begin as soon as the first or second week of July, said DNR Procurement Coordinator Melanie Williams.

Regional public utility districts and private energy companies produce energy in Washington, but the state regulates the industry and in the case of geothermal, helps take stock of resource potential. Higher-temperature sites are the most preferable. Following is a mapped visualization of geothermal energy exploration to date in Washington, created by Public Data Ferret.

View Larger Map
Double click (repeatedly, if desired) to zoom in and out. Click and drag to move the map. Data is from the American Association of State Geologists.

Fewer of the sites have been approved for harvesting of geothermal energy. These are shown via a map of current permits issued to drill geothermal boreholes in Washington; it was created using DNR’s interactive mapping tool. (Green dots represent sites with active permits; blue dots indicate expired permits).

No current projections are available for the percentage of Washington’s future energy demands that could be produced via geothermal sources, but according to a 2009 working paper from Washington State University and DNR, the region may be viable for producing at least a modicum of geothermal from low to medium temperature sources, for space heating and possibly electricity.

Development of many such wells would probably involve use of Organic Rankine Cycle methods, using heat to generate steam which then drives a turbine or simply conducts heat through an area. The process differs from typical steam power by its use of an organic liquid that evaporates at a lower temperature than water, so that steam can be generated even when the heat source is below 212 degrees Fahrenheit.

However, according to Jeff Bowman, a Geothermal Geologist at DNR’s Division of Geology & Earth Resources, Washington has significant obstacles to large-scale geothermal energy production for several reasons. Many of the areas that contain the greatest geothermal resources are in National Parks, Wilderness areas, and other protected regions. Additionally, a high degree of surface water pollution west of the Cascades makes it difficult to notice or analyze surface evidence. Ground-source heat pumps, used to help heat buildings by exchanging thermal energy with the ground or groundwater, are being used more frequently. The Snohomish County Public Utilities District is seeking geothermal energy sources for power production, but has suffered setbacks.

Although Washington is relatively poor in known high-temperature resources, low to mid-temperature geothermal wells can still be used to heat buildings, dry produce, and potentially generate some power. DNR is researching some of the details, with a $1.25 million U.S. Department of Energy grant. But in order to fully map geothermal resources in Washington, millions of dollars would have to be spent and extremely sophisticated techniques and tools would have to be deployed, Bowman added.

Overall, the state ranks fairly high nationally in low-carbon energy – due mainly to abundant hydropower. But Washington Initiative 937, approved in 2006, explicitly mandates that utilities must reach aggressive future goals for integrating renewable energy sources – not including hydropower – into the mix.

In 2005, the United States as a whole generated approximately 15,000 gigawatt-hours from geothermal sources; this accounted for about 25% of all non-hydroelectric renewable power generation in the United States at the time, according to a United States Geological Survey report. A watt-hour is the amount of energy required to light a one-watt bulb for an hour; a gigawatt-hour is exactly one billion watt-hours; consequently 15,000 gigawatt-hours is the amount of energy required to light fifteen thousand billion one-watt bulbs for one hour.

The USGS report concluded that full exploitation of discovered resources could expand production by approximately 6,500 megawatt-hours throughout numerous states, particularly in the western part of the country. A megawatt-hour is one million watt-hours. By using statistical modelling, the average amount of power that could be harnessed from currently undiscovered geothermal resources is 30,033 megawatt-hours. Enhanced geothermal resources would entail active alteration of a particular site, but could expand production by an average of 517,800 megawatt-hours.

Other states have already begun to investigate exploitation of geothermal power. Idaho’s Raft River Project is one work in progress. It has been estimated the project could generate up to 15.6 megawatts per square mile. By comparison, the two coal-fired boilers of the Centralia Power Plant had a combined output capacity of about 1340mW total from a relatively limited area; the plant consists of several buildings and a series of cooling ponds.

RELATED: Additional information on Washington State geothermal resources, DNR.

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