Several large geothermal resource mapping projects are heading toward conclusion so that finally, the power source can be more accurately considered in siting new electricity transmission lines for renewable power development.

Given the Obama administration's investment focus on new transmission line development, the result of the mapping efforts should be a relatively rapid increase in the number and size of commercial-scale geothermal projects.

The states of California and Nevada, along with the Western Governors Association, are moving rapidly to improve the mapping of geothermal resources in their regions, in part to facilitate the approval and construction of several new transmission lines in the West. And over the next few months, the U.S. Geological Survey (USGS) expects to unveil the data supporting its new assessment of mid-and high-temperature geothermal resources, which was released in summary form last fall.

These efforts are expected to lead to four or five new transmission lines in the West, with construction on at least one to begin as early as next year, reckons John McCaull, the western states representative for the Geothermal Energy Association, in Sonoma, CA.

One key resource mapping effort near completion is that of the joint Western Governors Association-U.S. DOE Western Renewable Energy Zones Initiative (WREZ), for which the technical committee is expected to identify final zones in late April, having considered the environmental impact of multiple zones in over a dozen western U.S. and Mexican states, as well as Canadian provinces.

By this fall, the WREZ then expects to complete a conceptual transmission line report, which would lead to discussions with line developers. An important aspect of the WREZ mapping is that all temperature range geothermal resources are being considered, including low-temperature enhanced geothermal system (EGS) sources, McCaull notes. WREZ also is mapping wind and solar resource sites as part of its renewable focus mandate.

Similarly, California's Renewable Energy Transmission Initiative (RETI) is completing a state-wide survey of geothermal resources with an overlay of best-option transmission corridors minimizing environmental impact. Elsewhere in California, the California Geothermal Energy Collaborative is developing high-resolution three-dimensional geothermal mapping, and expects to release its first area map by the end of this year, including high-, medium- and low-temperature sources, says William Glassley, the executive director of the group, in Santa Fe. "Transmission line locations are an integral part of what we are doing," he says.

In Nevada, a program similar to RETI is underway, focusing on northern and central regions of the state, says McCaull. Like California, Nevada primarily has considered proven, or higher-temperature resources for mapping.

Both states are expected to complete their surveys by late April, about six months ahead of the WREZ effort in terms of overlaying potential transmission lines, McCaull notes.

The USGS may begin releasing data from its new geothermal survey this spring, including both mid- and high-temperature resources. The prior survey included only high-temperature resources, says Colin Williams, a geothermal researcher in the Menlo Park, CA, agency office. Some low-temperature resources, like those in Alaska and other northern states — where a high differential between surface water and subsurface water temperatures exists — also will be included in the survey, he notes,

As a result of these cumulative efforts, four potential corridors have emerged as contenders for renewable power transmission in the West, McCaull suggests. These projects include:

  • Sunrise Powerlink, from the Imperial Valley to San Diego; this corridor has already received California approval.

  • Green Path, from the Imperial Valley to Las Vegas.

  • A North-South Nevada line to Las Vegas. Nevada Energy is already in the planning stages for a $30 million transmission line in Churchill County, which would serve both Vulcan and Ormat geothermal projects.

  • Northern California, potentially linking Oregon and Nevada to the San Francisco Bay area, serving not only geothermal but also wind and solar generators.

Apart from these four likely corridors, Vulcan Power of Bend, Ore., also is moving forcefully with its plan for a transmission line from northwest Nevada to Las Vegas and Los Angeles. The company's G3 power line project is being touted as a means of delivering a "green gigawatt" of energy, and likely can expect the support of Senate Majority Leader Harry Reid (D-NV), who has recently announced a proposed bill to build transmission lines for the delivery of renewable energy to urban areas. Reid has suggested a consolidation of transmission line authority among the two-hundred-plus government agencies now involved to a single federal agency.

New geothermal plants are being considered along each of these renewable power transmission corridors under development. As city, county and regional utilities seek to increase their renewable energy source portfolios, geothermal projects will likely provide an increasing volume of power, along with wind and solar.