SAN FRANCISCO — Geothermal energy — tapping into heat deep underground and using it to produce power — is sometimes described as a forgotten renewable. It languishes in the shadows of better-known sources like wind and the sun, and in 2011 it accounted for less than 1 percent of electric power worldwide, according to last year’s World Energy Outlook.

Yet the geothermal industry is growing, if slowly, and proponents hope that new technologies — including tie-ins with drilling for oil and natural gas — will bring further gains. Last year, the amount of electric power capacity available from geothermal resources grew about 4 percent to 5 percent globally, according to a report released in April by the Geothermal Energy Association, which is based in Washington. The United States remains the world’s leader in the use of geothermal energy for electric power, followed by the Philippines, Indonesia and Mexico, according to the report.

Large projects are planned for Indonesia and East Africa, and some Central and South American countries, such as Chile, are also showing interest. These fast-growing regions are hungry for new electricity sources, and international development banks are helping to finance the projects. (The lower-population New Zealand and Iceland are ranked sixth and seventh in total geothermal use.)

“If you’re wildcatting for geothermal, Africa really is one of those parts of the world where we seem to be going to,” said Maria Richards, coordinator of the geothermal laboratory at Southern Methodist University in Dallas.