The Energy Return of Solar PV [View all]

[GliderGuider]

This is a link to a blog post by Euan Mearns (with a very long comment thread), in which he discusses a days-old paper on the full-system ERoEI of PV panels when used in temperate climates.

The Energy Return of Solar PV

A new study by Ferroni and Hopkirk [1] estimates the ERoEI of temperate latitude solar photovoltaic (PV) systems to be 0.83. If correct, that means more energy is used to make the PV panels than will ever be recovered from them during their 25 year lifetime. A PV panel will produce more CO2 than if coal were simply used directly to make electricity. Worse than that, all the CO2 from PV production is in the atmosphere today, while burning coal to make electricity, the emissions would be spread over the 25 year period.

So what is ERoEI? It is simply the ratio of energy gathered to the amount of energy used to gather the energy (the energy invested): ERoEI = energy gathered / energy invested

Simple, isn’t it? Well it’s not quite so simple as it appears at first sight. For example, using PV to illustrate the point, the energy gathered will depend on latitude, the amount of sunshine, the orientation of the panels and also on the lifetime of the panels themselves. And how do you record or measure the energy invested? Do you simply measure the electricity used at the PV factory, or do you include the energy consumed by the workers and the miners who mined the silicon and the coal that is used to make the electricity? Ferroni and Hopkirk go into all of these details and come up with an ERoEI for temperate latitude solar PV of 0.83. At this level, solar PV is not an energy source but is an energy sink.

The related concept of net energy is defined as: Net Energy = ERoEI – 1 (where 1 is the energy invested)

Net energy is the surplus energy left over from our energy gathering activities that is used to power society – build hospitals, schools, aircraft carriers and to grow food. In the past the ERoEI of our primary energy sources – oil, gas and coal – was so high, probably over 50, that there was bucket loads of cheap energy left over to build all the infrastructure and to feed all the people that now inhabit The Earth. But with the net energy equation for solar PV looking like this:

0.83-1 = -0.17

….. Brussels we have a problem!

Mearns details Ferroni and Hopkirk's methodology, and has minor quibbles with parts of it. But overall he thinks they did a very respectable job. Their number compares appropriately to Prieto and Hall's earlier assessment of an ERoEI around 2. Mearns explains why their number is lower (mainly due to them examining temperate latitudes, if I understand it correctly.)

Yes, it's just one study. But if they are even close to right, there is no way that solar PV is a contender for the salvation of modern civilization. At best it's a niche player, at worst a harmful pipe dream.

Here is a link to a copy of the paper, for those who want a closer look:
https://collapseofindustrialcivilization.files.wordpress.com/2016/05/ferroni-y-hopkirk-2016-energy-return-on-energy-invested-eroei-for-photo.pdf