The Giant Space Wheel (of Seveneves) is so much more attractive than space elevator. That is a large mass on geostationary orbit having smaller pods rotating at the end of ropes. Those pods can be lowered to atmosphere and synchronized with earth rotation. Elevator pod comes down and can stay down maybe couple of hours and then jerked back to heavens. All energy comes from the sun - collected at the center station. Safe because pods can be quickly reeled back to space and stay out of atmosphere until conditions are optimal.