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?

Julian Cribb replies

30 10 2014

Dr Julian Cribb

If you haven’t read it yet or viewed the video, I recently posted an item about Dr Julian Cribb’s recent (October 2013) presentation to the Wheatbelt NRM Annual General Meeting.  It’s difficult when running a blog such as this to give someone you don’t know the right of reply, but this time Julian has taken the time to leave a reply, and as a mark of respect to him and in fairness to all opinions, I’ve decided to post it here as a proper article rather than see it lost in the thousands of comments which pepper this site.  I’m glad Julian has done this, and I fully understand his point about the difficulty of solving the world’s problem in a 30 minute talk; I haven’t managed it myself yet either!

Anyhow, some of you frequent readers might like to enter into a conversation with Julian, if he so desires here…. I personally cannot see how Julian’s assertion that ” it is going to take another 100 years or so to get the population (smoothly) back to 4-5 billion” can ever happen…  this particular subject is one I’m passionate about, so let’s hear it from you…

I also thought I had given Julian some credit for thinking about the issues we face when I wrote “I have come across more and more ‘experts’ who appear to be very well informed on the state of the multifaceted predicaments we face”.  Maybe a bit ambiguous, but…….

Over to Julian.


I think you are unfair Mike. It’s not possible to solve all the world’s problems in a 30 min talk, especially one that is specifically directed at a farming audience. But give me some credit for thinking about them, at least. As to population, read my book: the women of the world are already solving it – reducing their fertility in all regions globally. However it is going to take another 100 years or so to get the population (smoothly) back to 4-5 billion. The simple reason – that never seems to occur to rich western people who scream about population – is that part of the upward pressure is due to them living longer lives, not just to birth rates. If you want to control it, you are not only going to have to enforce family planning at gunpoint – but also impose euthanasia on the over-50s. See how much popular support you get for that.

Of course I know about the energy cliff and have heard Ian Dunlop speak wisely on the issue, as regards oil especially. But there are innumerable forms of energy available. You may have noticed my observation that the entire world’s transport fuel could be produced from an area of algae farms about a tenth the size of the Pilbara. That’s just one option. So I don’t buy the ” ‘We’ll all be rooned’ said Hanrahan” philosophy. There are viable options, especially for those who don’t simply give up.

If you want to know what I really think, here it is: humanity has the brains and the technical skills to carry us through the population and demand ‘hump’ and into a measured decline to a sustainable number. But we don’t have the governments, the economic structures or the educated society needed to achieve it.

Worst case is the Schnellnhuber scenario, or about 9-10 billion dead and a billion survivors, mainly in north Russia and Canada, by the end of the present century as a result of climate, resource and religious wars, famines, migratory conflict and disease. That’s also pretty much the CSIS worst case scenario too. Both presuppose limited use of nuclear weapons.

Personally I think there will be a few big wake-up calls well before we get to that. Like Bob Rich I think we’ll see a couple of megacities fall over, right on our iPhones. Mass killing, cannibalism, suicide, explosive emigration. If that doesn’t wake people up, then Homo don’t deserve the ‘sapiens’.

So rather than just grumble from your armchair, Hanrahan, lets start hearing some practical solutions.