Solar and wind power continue to grab the majority of headlines in the ongoing coverage of the growth of renewable power. Now, at least one other alternative-energy source has been quietly rising—literally and figuratively—in global use and awareness.

According to the Geothermal Energy Association (GEA), both the number of countries producing geothermal power and the total worldwide geothermal-power capacity under development are growing. At its Global Geothermal Showcase and Forum in Washington, D.C., on May 21, the GEA released a report that tracked the rise of geothermal power since 2005.

“The Geothermal Energy: International Market Update” report notes that 24 countries have 10,715 MW of online capacity generating 67,245 gigawatt-hours (GWh). This represents a 20 percent increase over the last five years. The report projects the online capacity to nearly double to 18,500 megawatts (MW) by 2015.

It also rates the top geothermal producing countries in the world. The United States, at 530 MW, tops the list, ahead of Indonesia, Iceland, New Zealand and Turkey, in that order.

The number of countries with projects under development also grew like a billowing cloud of runaway steam. The report notes that there were 46 countries considering geothermal-power development in 2007. In 2010, that number grew to 70, an increase of just more than 50 percent. Europe and Africa represent the two regions with the greatest increase in the number of projects under development.

The GEA study also notes that a previous report in 2009 had identified 39 countries that had the potential to meet 100 percent of their electricity needs through domestic geothermal resources. Since then, 25 countries have begun to tap the resource.

The report attributes the rise of geothermal power to new technology that allows development of lower temperature resources, and it calls for national and international policy and financial investment to support the industry’s continued growth.