It's hard to believe the words “clean” and “coal” could ever be uttered in the same breath. But a high-tech concept for low-emission coal power is increasingly gaining acceptance among industry executives and environmentalists alike. Like it or not, coal already accounts for 50 percent of America's electricity production, and yes, much of that comes from dirty old smog- and CO2-belching plants. The good news is that next-gen technology is on the horizon that could eventually make coal power emissions-free.