Imergy Power Systems’ headquarters in an office park in one of Silicon Valley’s less glamorous precincts is the type of place where the future used to be invented. There are no Beats headphones-wearing 20-somethings on scooters. No foosball tables, rooftop beer garden or ironically named conference rooms.No birdhouses. Just a sea of drab, blue-gray cubicles. The median employee age appears to be around that of the typical software engineer who files an age-discrimination lawsuit. There are scientists wearing white lab coats. Some have white hair. The chief executive is 61 – that’s 120 in Silicon Valley years.