Is Solar Worth It? EROI explained...

Just as I was getting on a plane to return from SolarCon 2023, an interesting thread popped up on Twitter.

It was about ‘agrovoltaics’- in this case, solar panes installed in an orchard where they produce energy while shading apple trees from hail, frost and heavy rain.

I triggered a response when I commented:

“That is a beautiful example of solar deployment”

And got:

“See any solar panel solar panel factories off the grid? Nope. You don’t. Because you’re a dope.”

I won’t do a blow by blow of the conversation but to summarize what our angry engineer was trying to say is something along the lines of solar panels not being ‘renewable’ because there are no solar panel factories that are powered exclusively by solar panels. And, more interestingly, that the Energy Return On Investment (EROI) for solar is so low that it is not economically viable.

The gist being that (he thinks) it takes more energy to manufacture PV systems than those systems can then produce.

Which would be a really good place to start when asking about various energy sources and processes. I mean, if you put in 100 and only get back 90- there’s no point… Right?

The first thing I’d like to point out is this-

There are stages along the energy lifecycle that are distinctly different. Consider:

- fuel has to be found, drilled, pumped, refined, and transported to a facility/machine. This is where EROI tends to focus.

- the conversion machine has to be built. There is an effort/expense in building that machine.

- the conversion processes often require power which means there is an expense in actual conversion of the fuel to power.

- the distribution of the power has expense as well (building transmission lines, transformers, breakers, etc.)

In the case of EROI for fuels, the basic equation is the amount of energy in the fuel delivered to the door of the conversion facility divided by the amount of energy it took to find, drill, pump, refine, and deliver said fuel.

Incredibly, the EROI of solar would be near infinite if it were compared exactly the same way- the amount of energy delivered to the solar panel on a rooftop is divided by the amount of energy it took to get it delivered there which is zero because sunlight just shows up without our intervention.

As a side note, the old evaluations of EROI were often funded by finance companies before nuclear and solar were a thing and then later by the nuclear industry. It should come as no surprise that most of these reports show that nuclear power has the absolute highest EROI where solar is shown as dead last. No conflicts there…

Anyways, when our angry engineer provided me this point I took a look. What I found was enlightening.

Turns out PV system technology has improved over the decades and has an EROI that is competitive with fuels.

This idea of his that it takes more to make a PV system than it can produce is flat out wrong. It seems that some calculations show on a total energy in versus energy produced is a payback period of 2-3 years.

So a PV system pays for the energy it took to create it within 2-3 years, one question is how long does it take from fuels derived power and nuclear power?

More important- once all those plants are at the point where they paid for themselves on this energy in/energy out concept- what does the equation look like then?

Solar power is delivered free.

Fuels, including nuclear, still have an extensive process just to get the fuel to the facility.

I don’t know what you guys might think, but it seems to me that all this solar power landing on our rooftops every day, for free, is a pretty incredible gift that we could (should?) be taking advantage of…

The energy economics of solar power just makes sense from that perspective. But there’s more.

I am not a big time fan of the ‘global warming’ stuff. I have my opinions, but that ‘discussion’ has devolved into a mud-slinging contest with just too much unnecessary drama…

To me, it is worse than discussing politics. There’s no win for anyone, just arguments.

That said, I do care a lot about the air we breathe. If you’ve ever been to a smog ridden city, you’ll know exactly what I am talking about.

SMOG is no joke. Many health issues can be directly associated with poor air quality, and we’ve known it for decades. In fact, as long as I can personally remember- major cities have had emissions testing for cars.

To me, emissions from a conversion process to generate power has a place in the discussion. It is important to factor in the waste/byproduct of a process when trying to figure out which one might make the best sense.

In that regard, I really like nuclear power but- there is a lot of consternation about how to deal with the radioactive waste it produces.

Solar, it seems, produces little or no emissions as a process. Despite the legacy oil’s best attempts to suggest solar panels can’t be recycled, at least the ‘waste’ is all contained in the panel rather than spread throughout the local atmosphere like fuels emissions that also cannot be recycled.

Bottom line, from a EROI standpoint solar panels are similar to fuels but have significantly better emissions characteristics.

Don’t take my word for it, scope out the abstract and especially the highlights sections of:

“The energy return on energy investment (EROI) of photovoltaics: Methodology and comparisons with fossil fuel life cycles“

https://www.sciencedirect.com/science/article/abs/pii/S0301421512002133

Back to angry engineer guy…

He smugly asked me yesterday morning:

“So, having given you a brief period to intellectually digest the information I have provided, and that you, if I remember correctly, claim to have worked in the nuclear industry - if all is 5x5 - do you now see the error in your ways?”

I replied with a few tweets explaining what I found in the EROI discussions above and provided links.

I gave him 24 hours (similar to what he gave me) and since there was no reply, I asked…

“So, having given you a brief period to intellectually digest the information…”

We’ll see what comes up, but I’m not holding my breath.

Thanks for sticking with me this long. Solar is viable, reliable, and in many cases affordable. Especially with the IRA tax incentives. If you are considering rooftop solar for your home I think you might want to check out my upcoming book Tucson Solar Insider Desk Guide for Buying Solar” - click here.

Be Good!

Curtis