Friday, 1 September 2017

These solar panels... are they going to last?

Ugo Bardi writes about the energy return on photovoltaics. Citing an article from Bhandari et al. that looked at 231 studies on ​how much energy comes out of photovoltaics​, and how much energy went into producing them, he comes up with an average return of 11-12 for southern Europe. ​This sounds worthwhile.

(From Dale and Benson)
​This graph paints a slightly different picture. It plots the number of years it takes for panels to generate the energy it took to make them against the growth rate of solar production. The payback got at least three times better in ten years, and the growth also increased three times. This means that, so far, more energy has gone into making solar panels than has come out of them. Hopefully, the growth will stop at some point, and the line will swing into the green as panel production stops growing while the installed panels keep generating. That depends on economics. 

Older estimates were that panels would still generate 80% rated power after 20 years, but according to Engineering. com, panels produced after 2000 will still be producing over 90%, losing only half a percent per year. So technically the panels will still be generating.

Economics is about resources. Somewhere human time is factored into ​it. We consider this resource very precious. ​I remember large scale road building projects in the UK that would decimate forest, destroy habitat and create pollution ​just to take a couple of minutes off people's car journeys. There is an economic pressure to reduce the amount of human time needed for tasks.

Another view is that human time is infinite, and the natural resources are limited. The classical economic view looks at productivity and considers environment assets to be externalities and essentially deems them infinite.  

​Hopefully growth of solar panels will go down, and they will become net energy contributors, but there is a powerful economic mechanism supporting production. If growth increases and we start throwing away the old panels, then that line may stay permanently in the wrong part of the graph, and photovoltaics will have just helped in our longer mission of depleting the world's resources.

The only redeeming feature is that they work very well in space, so we can take them with us when leave the planet! 

Bhandari, K. P.,  Collier, J. M., Ellingson, R. J. and Apul, D. S. (2015). Energy Payback Time (EPBT) and Energy Return on Energy Invested (EROI) of Solar Photovoltaic Systems: A Systematic Review and Meta-Analysis. Renewable and Sustainable Energy Reviews​,​ 47(July): 133–41. doi:10.1016/j.rser.2015.02.057.