[Popular Mechanics] The whine of the power plant sounds like a jet engine as refrigerant blasts through the turbine at 1000 mph. Though the equipment is compact, the din fills the vast hangar, and mechanical engineer Gwen Holdmann has to shout to be heard: “What you see here is very Alaskan. It’s not painted. It’s not pretty. But it’s real.” I place my hand on the steel door capping the plant’s evaporator; it’s warm to the touch, filled with Alaska’s most promising new energy source-plain water.