In a thermal runaway, a battery releases energy in the form of heat, increasing the temperature of the battery and causing further damage.

CNN: STORY HIGHLIGHTS

Recycling energy falls under the category of combined heat and power, which generates and uses both electricity and thermal heat-a technology that is now eligible to receive 10 percent investment tax credits from the U.S. government.

FORBES: Recycling Wasted Heat and Power Could Clear the Air

Then there is one of the oldest ways of getting power out from the sun: solar "thermal" installations, which absorb the sun's energy, transforming it into heat so it can boil water and run a turbine.

FORBES: The Sunshine Economy