If you are interested in the question of whether it makes sense to try to eliminate fossil fuels from the electricity production system, you are undoubtedly frustrated, as I am, by the astounding absence of critical thinking coming from almost everybody who writes about this subject.  There just seems to be such an incredible hunger to believe that this can work that literally nobody is willing to raise, let alone address, the very serious issues of feasibility and cost.  I have made my own humble efforts to throw something into the void by writing a series of posts that principally address the cost side of the problem.  See, for example, here and here.  

Now there is a serious contribution to the feasibility side of the problem, in the form of a recent (March 23) article from the publication Renewable and Sustainable Energy Reviews, titled "Burden of proof: A comprehensive review of the feasibility of 100% renewable-electricity systems."   The authors are a group led by B.P. Heard of the University of South Australia in Adelaide.  I don't know anything about most of the authors; but the fact that Tom Wigley of UCAR is one of them would indicate that you could not fairly call these people "climate deniers," or even "skeptics."  Hat tip to Kenneth Richard at NoTricksZone for the pointer to this article.

Heard, et al., have undertaken a comprehensive effort to identify every study since 2006 that has made a claim that "a 100% renewable energy system is achievable."  From that universe, they have then narrowed the field to some 24 that "have forecast regional, national or global energy requirements at sufficient detail to be considered potentially credible."  And then they do a deep analysis of each of the 24 on four fundamental feasibility criteria:

1. Realistic projection of future demand.  The issue here is that many of the studies in question project leveling off or declining of demand over the 21st century, somehow not realizing that world population is almost certain to increase by several billion during that period, and that electricity is going to come to large areas that don't currently have it, like Africa.  (Some of the studies in question, particularly ones done by environmental groups like WWF, project global energy demand declining by something like 90% by 2050!);
2. Realistic simulation of the matching of supply to demand so as to maintain near 100% reliability of the system.  Here the problem is that electricity supply must be matched very closely to demand on literally a minute-by-minute basis.  Therefore, studies that only consider or simulate the matching of supply and demand on a daily, or even hourly, basis are just kidding themselves;
3. Realistic simulation of how much additional transmission capacity would be needed; and
4. Realistic handling of what are referred to as "ancillary services."  The two big ones are voltage control (an electric grid operates with near-constant voltage -- not such an easy thing to achieve with wind and solar inputs ramping up and down by orders of magnitude over the course of minutes), and frequency control (alternating current systems have current that changes direction on a set frequency, generally 50 or 60 times per second -- again, not such an easy thing to keep regular when wind and solar production surge in and out).

And the results:

Based on our criteria, none of the 100% renewable-electricity studies we examined provided a convincing demonstration of feasibility. Of the 24 studies we assessed, . . . [f]our scenarios . . . did not meet a single feasibility criterion. Eight of the 24 scenarios did not do any form of integrated simulation to verify the reliability of the proposed renewable electricity system. Twelve of the 24 relied on unrealistic energy-demand scenarios, either by assuming unrealistic reductions in total primary energy and/or by making assumptions of extreme increases in electrification. Only four of the studies articulated the necessary transmission requirements for the system to operate, and only two scenarios, from the same authors [8], partially addressed how ancillary services might be maintained in modified electricity-supply systems. No studies addressed the distribution-level infrastructure that would be required to accommodate increased embedded generation, leaving a gap in the evidence relating to ancillary services and overall system reliability.    

To put it another way, 24 out of 24 studies that rose to the level of "potentially credible" all proved without exception to be exercises in self-delusion.  Who here is surprised?

The authors are notably critical -- and in my view appropriately so -- of trendy Stanford prof Mark Jacobson, the guy who provides the supposed studies that give Jerry Brown the idea that he can "save the planet" by forcing Californians to get all of their power from wind and solar.  Here are Heard, et al., on Jacobson:

The absence of whole-system simulations from nine of the reviewed studies suggests that many authors and organizations have either not grasped or not tackled explicitly the challenge of ensuring reliable supply from variable sources. . . .  Jacobson et al. [24,113,116] also proposed supply systems without doing simulations, instead referencing other studies to assert that system reliability is possible [8,117,118]. Jacobson et al. [24,113,116] did not apply simulation processes to their own, different proposed systems, nor did they address the uncertainties, challenges and limitations articulated in their supporting references or related critiques . . . .   

Well, good luck with your hallucinations, California!

And here are a couple of more tidbits from the "Conclusions" section:

For the developing world, important progress in human development would be threatened under scenarios applying unrealistic assumptions regarding the scale of energy demand, assumptions that lack historical precedent and fall outside all mainstream forecasts. Other outcomes in sustainability, social justice and social cohesion will also be threatened by pursuing maximal exploitation of high-impact sources like hydro-electricity and biomass, plus expanded transmission networks. The unsubstantiated premise that renewable energy systems alone can solve challenge of climate change risks a repeat of the failure of decades past. The climate change problem is so severe that we cannot afford to eliminate a priori any carbon-free technologies.  

Yes, these guys actually believe that the "climate change problem" is "severe."  But at least they are able to maintain a modicum of critical thinking when seeking to address the "problem."

And finally this:

Our sobering results show that a 100% renewable electricity supply would, at the very least, demand a reinvention of the entire electricity supply-and-demand system to enable renewable supplies to approach the reliability of current systems. This would move humanity away from known, understood and operationally successful systems into uncertain futures with many dependencies for success and unanswered challenges in basic feasibility. 

And with all of that, they never get to the question of cost.  Anyway, believe me, I'm glad to welcome anyone willing to do critical thinking on this subject as an ally.