Take your pick. I have the answer in a word, paragraph, or 4 minute video.
Alex Epstein at Prager University provides us the answer on 10/20/15: Can We Rely on Wind and Solar Energy.
Short answer is no.
Medium answer is wind and solar are weak and unreliable. Technical terms are dilute and intermittent. That makes them both extremely unreliable and extremely expensive. Oh, that also means that backup power must be available, which will obviously be fossil fuels.
For the four and a half minute answer, check out: