Stevenson, now 75, describes himself as “a lifelong conservationist.” In the driveway of his Lewes, Delaware, home sits the hybrid vehicle he often drives to a nearby beach. Solar panels glint atop the roof, which Stevenson custom-designed in 2013 to be at the “optimum angle” to soak up the sun. A framed newspaper article about one of his cross-country bike rides hangs on the wall...