Jeff Bezos took to 60 Minutes to announce Prime Air, a drone-based 30-minute delivery system for densely populated areas that comes with its own video design-fiction illustrating how it might work. The vision is an exciting one, but the designfic elides some important questions like the regulatory framework under which thousands (millions?) of drones might share the sky as businesses compete to do airborne delivery; whether that framework would be sufficient to actually maintain public safety (hello midair drone collision over a busy highway with attendant plummeting shrapnel into the path of speeding cars!); and what the energy and carbon footprint of drones would be, especially with comparison to conventional delivery logistics.
On the last point, I'm somewhat optimistic. One big problem with renewables is storing excess power generated during peak periods (tidal inflows/outflows, high wind events, strong sun), and having fleets of independent, battery-powered systems handy presents a solution: use their batteries as storage for this excess capacity. So if you imagine networks of drone-depots topped with solar arrays and/or windmills (or near to tidal generators on the coast), these could use drone batteries to both store energy for the drones, and as a storage medium to draw upon for internal power usage (pick-and-pull robots, etc) during the troughs in renewable output.