At issue are the vagaries of nature. The wind can never blow with the same steadiness that factory-combusted coal provides, and the sun’s rays, while ever present, are all too often blocked from reaching the panels we’ve built to gather them by clouds. Each moment of shade, no matter its length, is translated by solar panels into a dip in the electricity they produce. Every shift in the wind’s speed becomes an uneven rise and fall of available electrical current.
