The energy produced from renewable sources, particularly wind and solar require back-up sources to accommodate the minimum base load to support the unpredictability of the aforementioned.
.. Casts a bit of a pall onto the whole issue
Really why? Green tech is in its infancy, but has already advanced much more quickly than its detractors predicted. It will continue to advance for three reasons:
1. Most people prefer clean air over dirty air.
2. The cost of producing green energy is steadily dropping.
3. Technical problems of storage are being tackled in a multitude of ingenious ways.
4. Green tech offers a stable solution to producing energy, unlike the wildly fluctuating prices in commodities like oil, and the uncertainty of oil fields that are primarily controlled by unstable undemocratic regimes.
Note, this has nothing to do with global warming. It is all about superior tech replacing old tech, in much the same way that coal and oil replaced traditional fuels.