The ugly side of solar panels

New research shows, albeit unintentional, that generating electricity with solar panels can also be a very bad idea. In some cases, producing electricity by solar panels releases more greenhouse gases than producing electricity by gas or even coal.

(Picture: Sungazer)

 

Producing electricity from solar cells reduces air pollutants and greenhouse gases by about 90 percent in comparison to using conventional fossil fuel technologies, claims a study called "Emissions from Photovoltaic Life Cycles", to be published this month in “Environmental Science & Technology”. Good news, it seems, until one reads the report itself. The researchers come up with a solid set of figures. However, they interpret them in a rather optimistic way. Some recalculations (skip this article if you get annoyed by numbers) produce striking conclusions.

Solar panels don’t come falling out of the sky – they have to be manufactured. Similar to computer chips, this is a dirty and energy-intensive process. First, raw materials have to be mined: quartz sand for silicon cells, metal ore for thin film cells. Next, these materials have to be treated, following different steps (in the case of silicon cells these are purification, crystallization and wafering). Finally, these upgraded materials have to be manufactured into solar cells, and assembled into modules. All these processes produce air pollution and heavy metal emissions, and they consume energy - which brings about more air pollution, heavy metal emissions and also greenhouse gases.

Energy mix

The ecological burden of energy use depends on the way electricity was generated. Therefore, the researchers bring into account 3 scenarios. One is based on the average European energy mix, another on the average American energy mix (which is about 45% more CO2-intensive) (Note: in this article, “CO2” stands for CO2-equivalents which means other greenhouse gases are included). A third scenario uses the figures of the recent “CrystalClear” European Commission project, which investigated the real energy mix used by 11 European and American silicon and PV module manufacturing factories. Since they use comparatively more gas and hydropower, this is the best case scenario. The researchers investigated 4 types of solar cells: multi-crystalline silicon (with an efficiency of 13%), mono-crystalline silicon (14%), ribbon silicon (11.5%), and thin-film cadmium telluride (9%).

"The optimistic conclusions of the researchers are based on a life expectancy of 30 years and solar insolation in the Mediterranean"

The scientists come up with figures concerning the amount of greenhouses gasses emitted per kilowatt-hour of electricity delivered by one square meter of solar cells. They do that for every type of cell and for the three different scenarios. Thin film solar cells get the best score with 20.5 grams of CO2 in the European energy mix and 25 grams of CO2 in the American energy mix. In spite of their lower efficiency, they are more eco-friendly because they need less material and no aluminium frame. In spite of their high efficiency, mono-crystalline silicon cells score worst, with 43 grams of CO2 in the EU, and 55 gram of CO2-equivalent in the US. All other types and scenarios fit between these two extremes.

Solar insolation

However, these conclusions are dependent on some assumptions, most importantly solar insolation (the amount of sunlight that the cells receive) and lifetime expectancy. For solar insolation, the researchers choose 1,700 kWh per m² per year, which is the average of sunlight in Southern Europe. For lifetime expectancy, they choose 30 years. From these variables, they calculate the total lifetime electricity generation of one square meter of solar cells. Next, they divide the amount of CO2 emitted for the production of one square meter of solar panels by this lifetime electricity generation – and that’s how they achieve their conclusions.

"Surprisingly, the key data of the calculation (the amount of CO2 emitted per square meter of solar panels) are nowhere to found in the report"

Surprisingly, the key data of the calculation (the amount of CO2 emitted per square meter of solar panels) are nowhere to found in the report. That’s remarkable, since these data are the most objective numbers available. Even so, they can be calculated by multiplying the obtained results (in gram CO2 emitted per kilowatt-hour of generated electricity) by the lifetime electricity generation. This calculation gives the amount of greenhouse gases emitted for the production of one square meter of solar panels, regardless of the assumptions on solar insolation and lifetime expectancy.

2 to 20 flights

Once calculated, it's not so suprising that the researchers choose not to write these figures down. In the best case scenario, one square meter of solar cells carries a burden of 75 kilograms of CO2. In the worst case scenario, that becomes 314 kilograms of CO2. With a solar insolation of 1,700 kWh/m²/yr an average household needs 8 to 10 square meters of solar panels, with a solar insolation of 900 kWh/m²/yr this becomes 16 to 20 square meters. Which means that the total CO2 debt of a solar installation is 600 to 3,140 kilograms of CO2 in sunny places, and 1,200 to 6,280 kilograms of CO2 in less sunny regions.  These numbers equate to 2 to 20 flights Brussels-Lissabon (up and down, per passenger) - source CO2 emissions Boeing 747.

According to the researchers, producing the same amount of electricity by fossil fuel generates at least 10 times as much greenhouse gasses. Checking different sources, this claim is confirmed: 1 kilowatt-hour of electricity generated by fossil fuels indeed emits 10 times as much CO2 (around 450 grams of CO2 per kWh for gas and 850 for coal). Solar panels might be far from an ideal solution, but they are definitely a better choice compared to electricity generated by fossil fuels. At least if we follow the assumptions chosen by the researchers.

Northward 

 Logically, if we make the same calculations for a solar insolation of 900 kWh/m² (the yearly average in Western Europe and in the Northeast and Northwest USA), the results get worse. In the worst case scenario (US grid, mono-crystalline silicon), emissions rise to 104 gram CO2 per kilowatt-hour of solar generated electricity, which makes solar panels only 4 times cleaner than gas. Now let’s play a bit with the life expectancy.

If we combine this lower solar insolation with an expected lifetime of only 15 years, the worst case scenario becomes 207 grams of CO2 per kilowatt-hour – just 2 times better than gas. Agreed, this is the worst case scenario, and even in that case solar panels are still a better choice than fossil fuels. But it becomes quite hard to describe them as a “clean” source of fuel.

This map (click to enlarge) shows the amount of solar energy in hours, received each day on an optimally tilted surface during the worst month of the year. For a more detailed view of solar insolation (in kWh/m²/yr) see the links above.

 "A better strategy would be to use already available solar panels to produce more solar panels"

The life expectancy chosen by the researchers is, well, just an expectation. It’s true that most manufacturers give warranties of 20 to 25 years, so technologically speaking a life expectancy of 30 years is not implausible. However, there are other than technological reasons that may lead to a significantly lower life expectancy. The scientists note that the environmental score of solar panels will improve, because they are becoming more efficient each year. (They also become thinner, so less energy is needed to make them). Most likely they will also become cheaper.

Life expectancy

That means that in 15 to 20 years time, if the evolution in efficiency carries on the way it does now, a solar panel with an efficiency of 10 percent produced today will have to compete with cheaper solar panels that have efficiencies of about 20 percent. Moreover, and that’s a fact that the researchers are not taking into account, solar cells degrade in time. Typically, the warranty given by solar cell manufacturers covers just 80 percent of power output. All this means that it may make economic sense to substitute older panels with newer panels before they are 30 years old. Again, even in that case the ecological score will probably still be better than the one of fossil fuels, but the point is that the gap can become very small.

 For rooftop and ground-base installations, the eco-friendliness can be good or doubtful, depending on the solar insolation and the life expectancy. But if we consider solar panels mounted on gadgets like laptops or mobile phones, solar energy becomes a plainly bad idea.

If we take a life expectancy of 3 years (already quite optimistic for most gadgets) and a solar insolation of 900 kWh/m² (quite optimistic too, since these things are not lying on a roof), the result is 1,038 gram CO2 per kWh in the worst case scenario (high-efficient mono-crystalline cells produced in the US). That means that it is better for the environment to power a gadget with electricity generated by coal, rather than by a solar panel.

Now what?

 All this does not mean that PV solar energy should not be promoted. For one thing, it’s much better using silicon wafers to make energy generating equipment instead of energy guzzling equipment (like computers, mobile phones and car electronics). But some facts have to be faced.

First, solar cells are far from a zero emission technology. Two: solar panels can be a doubtful choice in less sunny regions. Three: solar panels mounted on gadgets are completely insane. Four: solar cells should be recycled. Five: some law or incentive should be introduced to guarantee a life expectancy of 30 years. And if possible, solar thermal power should have priority over solar PV power.

"All this does not mean that PV solar energy should not be promoted. But some facts have to be faced"

It should be realized that solar panels first raise the amount of greenhouse gasses before they help lowering them. If the world would embark on a giant deployment of solar energy, the first result would be massive amounts of extra greenhouse gasses, due to the production of the cells. 

Use solar panels to produce solar panels

A better strategy would be to use already available solar panels to produce more solar panels. The scientists calculated that the ecological burden of solar panels can be halved if 100 percent of energy in the factories would be delivered by solar energy.

I did not do the calculations for air pollution and heavy metals, but since these are mainly produced by energy use for production, the conclusions must be similar.

© Kris De Decker (edited by Vincent Grosjean)

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Update April 2015: How sustainable is PV solar power?

Solar photovoltaic (PV) systems and their manufacturing become more efficient over time, so you would expect that the situation has improved since 2008. However, things got worse. This is largely due to the relocation of manufacturing to China, where the electric grid is twice as carbon-intensive and 50% less energy efficient.

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How to Get Your Apartment Off the Grid

The typical solar PV power installation requires access to a private roof, and a big budget. However, wouldn't it be possible to get around these obstacles by installing small solar panels on window sills and balconies, connected to a low-voltage direct current (DC) distribution network? To put this theory to the test, I decided to power Low-tech Magazine's home office in Spain with solar energy, and write my articles off the grid.

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Also:

• "Toward a just and sustainable solar energy industry", A Silicon Valley Toxics Coalition White Paper (January 14, 2009) (pdf, 1.2 mb). An overview of the toxic chemicals used for the production of solar panels.
• "You’re heartsick about global warming, so you’ve just paid $25,000 to put a solar system on the roof of your home. How do you respond to news that it was manufactured with a chemical that is 17,000 times stronger than carbon dioxide as a cause of global warming?"

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Low-tech Magazine makes the jump from web to paper. The first result is a 710-page perfect-bound paperback which is printed on demand and contains 37 of the most recent articles from the website (2012 to 2018). A second volume, collecting articles published between 2007 and 2011, will appear later this year.

Read more: Low-tech Magazine: The Printed Website. 

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Comments

[Crashley]

(101)

I find this discussion very interesting. To my knowledge, NO ONE in the media mentions that it takes lots of energy to produce solar panels, or even attempts to say how long they must produce energy to break even.

I think it still makes sense to manufacture, use, and improve them as eventually the energy to produce them could come from PV and other renewable sources. I was surprised to see how long this discussion has been going on. Good work.

PS: I've been in the satellite business for almost 35 years and PV and batteries are the only way to go for a 15+ year lifetime. Talk about off the grid.

[Crashley]

(102)

A 12kW triple junction GaAs solar array in space produces about 1.5 GWh in 15 years. How many Wh do you think it took to produce it? (I don't know) Obviously it does not offset any terrestrial energy production since there is no other way to get power to the satellite

I realize this is not really relevant to the discussion, but I am curious.

By the way, the "scorecard" site did not seem to address how many Wh it takes to produce a W of solar panel output. Or maybe I missed it.

[Jamey Johnston]

(103)

Seem like there is a scholarly / engineering disagreement, hmm?

https://energy.stanford.edu/news/PV-industry-likely-net-energy-producer

[pam]

(104)

know-it-all rants by Devry tech grads like dana are really impressive...

[Slowburn]

(105)

Photo-voltaic is the wrong way to harvest solar energy. Use solar water heaters to drive absorption heat pumps, and Stirling cycle engines. Expand the ammonia through modified water cool ICE so that as well as generating the mechanical energy you get to keep the cool for food preservation, air-conditioning, & and water harvesting. This also give inherent energy storage as you do not release the anhydrous Ammonia to the engine until you need the power whether to directly drive a machinery or generate electricity.
Don't forget to harvest the waste heat from the heat pump's condenser.

[Wouter Carrette]

(106)

Did anyone even figure in the transportation CO2 footprint?
As most panels are produced in China, they still need to be moved to the rooftops in Europe/the US. How about that?

[Peter]

(107)

I think producing and using solar power systems, the positives far outweigh the negatives. Sure it will cost some to produce, but with the climate in such a fragile state as it is, ignoring the issue is not the answer. There seems to be so many misconceptions about solar, and you have to wonder where the rumours of this energy system get started, and whom it benefits in the long run? My bet is that for those who are invested in other energy systems would love to spread these negative issues around. Here is a helpful little article that I co-wrote about with an electrical contractor, that discuss the 7 top questions, and we were hoping to dispel the misconceptions in a casual way around solar power -
https://east-westelectric.com/the-top-7-questions-when-it-comes-to-solar-panels/

[Abacus]

(108)

Ok so we need to consider the amount of CO2 emission in total to produce 1 square meter of Solar Panel from scratch. Take that number to calculate the total CO2 cost over the life span of 20-30 years. Then compare that with the total amount of CO2 produced by Coal/Gas in the period of 20-30 years. WHERE do you account for the amount of CO2 cost to produce the entire infrastructure to support the entire Coal/Gas Industry ? It does not take a math genius to figure out what is wrong

[ZMacZ]

(109)

Hold ur horses.

It's comparing to regular fossil fuel production.

There's a few parts missing:

-carbon footprint into producing the materials to use fossil
fuels, like boats to move the oil, refineries, gas stations,
moving of oil products to gas stations etc. THAT has a big
fat carbon footprint as well.

-the lifespan of solar panel isn't 20 years or even 25,
the lifespan is until it stop producing electricity
altogether, which in my modest opinion is well in the 100
years range, until the last cell drops out.

For a typical solar panel 260 Wp, that would be (@6 solar
hours per diem) 6x365x100x260x50% (WP x average efficiency over 100 years) roughly 28.5 MWh, until the last cell dies and gives up it's yield. (this is very conservative, since the more modern solar panels do even less than 1% reduction each year, making their lifespan even greater than 100 years).

And then, ofc, using solar power (nothing but), to produce
solar power, which will be the way to the future.

In all, the 'conclusion' of such a report leave salot to be
desired, and should also be done by actual scientists, not
'hired' 'scientists' who have used half a brain to come up
with some calculation, that does NOT reflect ALL variables
involved, and also assumes that the solar panels will simply
'die' after a mere 20 or 25 years.

So, nope, MY conclusion is still, solar panels are well
worth the effort, and over time will power the world,
in it's entirety.

I also foresee the synthesis of fossil fuels,
by means of high atmosphere CO2 harvesting,
but that's another story.

[ZMacZ]

(110)

One more thing, when solar panels reach EOL, they can be harvested for the same materials that is required for the production of new cells. And that certainly generates a brand new re-use factor.

The breakdown of most solar cells is due to local high energy in the cells themselves, both from UV and electrons, causing electron migration. However, electron migration does not cause any chemical change, and only breaks down connections within the cells themselves.
Knowing that there's only 2 substances in the degraded solar cells, they only need separating and 'reformatting' back into whole cells.

Ofc, there's a price to it, and yet this is much lower than
production from raw materials. So, no, solar panels still better.

[Ian]

(111)

https://www.forbes.com/sites/michaelshellenberger/2018/05/23/if-solar-panels-are-so-clean-why-do-they-produce-so-much-toxic-waste/
Old but still current nh3
70 million tons on the docks waiting to be taken away

[Burt Sidefish]

(112)

hey Kriss, if you are still reading these comments
as I understand it, a big source of the emissions for silicon cells is in refining the silicon from silica, which oversimplified looks like this: SiO + C -> Si + CO2
which can't be shunted with solar power, although the process is also energy intensive...which is why onsite solar probably isn't common, needs a big and steady power supply that a solar based grid can supply but onsite cannot.

I have a dream of hydrogen refined silicon using a solar concentrator but I don't know how I could achieve it, I being just some internet armchair warrior.
I hope we find a way to continue living.

[Greg]

(113)

OK, so somebody worked out the carbon footprint of producing the solar panels that generate electricity, and it's still somewhere between marginally & much better than burning coal.

Now lets compare like-for-like: What's the carbon footprint of constructing a coal power plant? (hint: there's a lot of concrete in there). What's the carbon footprint of building & running a coal mine? and trucking the coal to the power plant? PV solar still wins by a big margin.

Now lets get to the much more important question: Why are we still debating this?

[Antonio Lambe]

(114)

Thank you for a VERY topical article with many well-informed comments (and some quite misinformed and even boorish ones).
But the piece is >10-years-old and, as the author anticipated, the technology has since improved. Might an updated version be possible?

[kris de decker]

(115)

@ Antonio

There is an updated version from 2015: https://www.lowtechmagazine.com/2015/04/how-sustainable-is-pv-solar-power.html

[Martha Kennedy]

(116)

Well it's now 2020 and we just moved to Colorado. And solar is BIG BIG here. I'd just like to ask what are all these people going to do when the gas and oil run out??? Cause make no mistake it will. But hey guess that'll be our kids problems huh? Along with land that has been gashed open to ha e it's minerals ripped out causing deforestation, flash flood risks.Then toi can go into all the health conditions miners are prone too. As for my household we will be checking into solar soon

[Kin Rocker]

(117)

This is completely stupid.

"Next, they divide the amount of CO2 emitted for the production of one square meter of solar panels by this lifetime electricity generation – and that’s how they achieve their conclusions."

In other words, the authors calculate a CO2 footprint of solar panels based on the assumption that we don't use renewables for generation. Let me turn that around and assume we use only renewables, in which case the CO2 footprint becomes zero. Not the same can be said about fossil fuels.

Let's call out this lack of logic, please.

[kris de decker]

(118)

Author here. Can't believe that this topic is still so controversial, 12 years after the article was published.

I am still standing behind this article, and if you read the update article from 2015, you see that this original post was not critical enough: we now produce solar panels in China, which increases their CO2-footprint and energy use, and we install them mostly in regions with not much sun, which decreases their energy production.

Finally, I am not against solar panels. In fact, both my office and my new website (https://solar.lowtechmagazine.com) run on solar power. Solar PV power is not a black and white issue. We should discuss both the good and the bad -- or ugly -- sides.