Five decades ago, an idea sprouted into an event that grew into a movement, which April 22, on its 50th anniversary, we recognize as Earth Day – a global day of awareness and a celebration of principle, responsibility, and sustainability.   The National Renewable Energy Laboratory (NREL), originally the Solar Energy Research Institute (SERI), has always enjoyed strong ties to Earth Day.    NREL’s second laboratory director, Denis Hayes, played a key role in its creation, coordinating the...