OAK RIDGE, Tennessee, June 9 -- The U.S. Department of Energy's Oak Ridge National Laboratory issued the following news release: Oak Ridge National Laboratory researchers, in collaboration with Enginuity Power Systems, demonstrated that a micro combined heat and power prototype, or mCHP, with a piston engine can achieve an overall energy efficiency greater than 93%. Designed to replace a backup generator or traditional gas hot water heater, the mCHP switches between natural gas, hydrogen or bio  more