United Press International: Add another requirement to the clean-energy checklist: low water usage. Two Virginia Tech researchers released a study this week examining the water-use requirements for 11 different energy sources, ranking them in terms of efficiency. One of the most important aspects of the study was to raise awareness of the role water plays in energy production, said Rachelle Hill, a recent Virginia Tech graduate who co-authored the study. "We need to do more research and really …