How Solar PV Can NOT Power A Carbon-Free Energy Revolution, In 4 Charts

30 10 2014

Once again, the internet proves how nobody understands NETT ENERGY.  A friend pointed me to this article titled “How Solar PV Can Power A Carbon-Free Energy Revolution, In 4 Charts” which I quickly glanced at (I’m busy making cheese right now!) and thought ‘is this for real?’  I then emailed the link to our resident professor, Dave Kimble who cobbled a response together that I will attempt to parse here correctly…….

Dave first pointed out that the “Inputs and outputs for a whole industry” ‘chart’ is not a chart at all, it is a diagram.  it is also not a chart resulting from calculations.  It has the right shape, but its timeframe is all wrong.

inputs~outputs-for-PVsIt should actually look more like this:

real-inputs~outputs-for-PVsThe article also states “the EPBT for PV systems in regions with high amounts of sunlight (high solar insolation), such as the U.S. Southwest, is now under one year.” EPBT stands for Energy Pay Back Time.  I’d missed that one, and when Dave pointed it out to me, I was gobsmacked……  because such a short energy return implies an ERoEI of 25:1, when in fact Pedro Prieto and Charles Hall recently calculated that it was more like 2.5:1, but what’s one order of magnitude among friends….?

.To me it makes absolute sense that as the ERoEI of the fossil fuels used to make PVs drops, the ERoEI of PVs should also drop……  there is no free lunch here, this is the energy trap we are looking at…..

Then Dave pointed out that the ERoEI is critical to how long the EPBT actually is.  Here is a chart from his own website:

“If the industry grows faster than a critical amount” says Dave, “then the fossil energy subsidy grows bigger and bigger:  The limit is given by (ERoEI/Lifetime)*100 % per year, so if the ERoEI is 25, you can grow at 100%, but if it is 2.5 you can only grow the industry at 10% – anything above that can never be energy positive.”

The article then states:

They projected that “the payback year has a 50 percent likelihood of occurring between 2012 and 2015.” In other words, there’s a good chance the cumulative solar energy generated by every PV system in use as of today equals the cumulative electricity consumed in producing those system to date.

This is “largely due to steadily declining energy inputs required to manufacture and install PV systems.”

How can there be steadily declining energy inputs when all the ore grades for the materials involved are getting worse, and the ERoEI of the fossil fuels is going down too, and may not be available within 10 years?  As usual, it’s what you leave out of the EI part of ERoEI that matters, and I doubt Pedro would have left anything out, because he’s run solar farms in Spain, and knows full well what goes IN to make them work…..  For instance, the article gloats over the fact that the cost of PVs has dropped 99% over the past 25 years (from $10/W to $1/W now), but that’s mostly because robots are now making them instead of people.  How much energy went into build the robots and the factories where they are being built?  ALL made with low ERoEI fossil fuels?  And their numbers must grow to keep up with production growth too…..

Can you tell I’m still sceptical?