The 30-foot hull of an experimental mini-sub is helping to show how the U.S. may be able to redeploy the mountain of coal that power plants are no longer burning.

Researchers at the Oak Ridge National Laboratory in Tennessee used carbon fibers to build the submersible for the U.S. Navy with a 3-D printer, demonstrating the promise of new manufacturing techniques that are faster, cheaper and more flexible. But it also offers inspiration to scientists looking to turn America’s vast reserves of coal into advanced materials, including carbon fibers now made using petroleum-based polymers.

The search for alternative uses has intensified as utilities switch to cleaner options for generating electricity, like natural gas, wind turbines and solar panels. While no one expects the research to revive all the coal-mining jobs that disappeared in recent years, experts say new sources of demand are emerging for the carbon-rich rock, from battery electrodes to car parts to building materials.

“Our slogan is ‘No molecule left behind,’” said Edgar Lara-Curzio, who is researching alternative uses for coal at Oak Ridge. “Coal for power generation is going to continue to decrease. Here is a chance for us to pay back all these coal communities that have sacrificed for so many years to give us cheap electricity.”

Even after years of decline, the vast majority of America’s coal is still used for electricity generation. However, the fossil fuel accounts for just 30 percent of the power mix today, down from about half a decade ago. Since 2008, U.S. coal production has plunged 40 percent, to 728 million tons last year, according to the Energy Information Administration. With less demand and more industry automation, the number of miners fell 40 percent to about 50,000.

Perhaps the greatest potential for coal now is in carbon fiber already widely used in aircraft and high-cost luxury items, said Eric Eddings, a scientist at the University of Utah in Salt Lake City. The strong, stiff and ultralightweight fibers of nearly pure carbon could be used to replace heavier materials including aluminum and steel in a growing range of products. Japanese giant Mitsubishi Chemical Holdings Corp. has for decades used coal to create carbon fiber, which is used in everything from satellites to golf clubs.