• Karn Sinha

Is Solar Energy really as eco-friendly as we think?

Solar energy is the most eco-friendly form of electricity. Its generation is emissions-free and it's inexpensive.

But if something sounds too good to be true, there's got to be a catch, right?

The biggest source of emissions is the manufacturing process and that the solar panels themselves will constitute over double the tonnage of all of today's global plastic waste.

Well, that all sounds like solar energy is not as green as a lot of us might think. Is that really true?

Let’s take a look at three big criticisms solar energy faces.

First, let's examine solar energy's impact on the climate. Solar panels produce electricity without creating emissions. This sounds great but it's also not the whole story. Mining and processing raw materials, transporting them, manufacturing, and assembly use a considerable amount of energy. Since our economies, currently, still run largely on fossil fuels, this amounts to significant greenhouse gas emissions.

But the question is: How much? And how much is that compared to other sources of energy?

Well, to answer that, there's a thing called "Lifecycle assessment."

In the context of electricity generation, the service that's being provided is the generation of a kilowatt-hour. The role of lifecycle assessment is to do as comprehensive and complete an accounting of, for instance, the greenhouse gas emissions that are emitted that are attributable to that kilowatt-hour.

On average, solar energy emits around 40g of CO2-equivalent per kilowatt-hour it produces. Which is much lower compared to fossil fuels like natural gas at 486g. Or coal at 1001g. But then again sun power does emit a little bit more CO2 than wind power (43g vs 16g). What do we make of that?

"It shouldn't really be a choice at this point of life cycle greenhouse gas emissions between different renewables. They all provide significant benefit when displacing conventional."

What's more is that solar energy has been becoming more efficient over time, which could further push down lifecycle emissions. In the future, there might even be completely new solar technologies, like Perovskite modules. These promise to use less energy in production and to convert even more sunlight into electricity. And then, there's a kind of snowball effect. The more solar gets deployed, the cleaner it will become to produce even more.  So, yes. Strictly speaking, solar energy isn't completely emissions-free. But it is already one of the climate-friendliest energy sources we have.

Second, let's take a look at what actually goes into making all these panels. The production of solar cells required many chemical substances. For example, the process of refining the silicon produces silicon tetrachloride. It can be recycled and then reused. But it's not clear whether manufacturers always do recycle. If it ends up in the water, it can have devastating effects on the environment and people's health. Similarly, Hydrofluoric acid, which is needed to clean the solar wafers during production, is a highly corrosive acid that needs to be handled very carefully.

"We have a lot of hazardous chemicals of concern that are used to make solar panels." says Sheila Davis of the Silicon Valley Toxics Coalition. She developed the Solar Scorecard that ranks manufacturers by their sustainability. "We don't want to solve the climate problem at the expense of other important environmental issues like hazardous waste issues or resource issues or chemical issues that are toxic issues. That's pretty much the problem with solar. So, it is green but it's only green in one phase. We want to make sure it's green throughout its lifecycle.”

Another problem is that depending on the type of solar cell, and manufacturer, hazardous materials like lead, cadmium, or arsenic can end up in the modules. But increasingly, there are alternatives. "One of the key components of finding safer alternatives is being able to perform what they call an alternative chemical assessment. And luckily, right now we have the capacity to do this. Maybe 10 years ago, we might not, but now we have, you know, artificial intelligence, we have machine learning, we have Internet of Things. All these computer enabling technologies that allow us to find alternatives, safer alternatives, much cheaper."

The chemicals needed to make solar cells are problematic. There really needs to be pressure on the industry to come up with alternatives – and make the switch once they find them.

Finally, let's take a look at where all these panels go to die. Solar panels last around 30 years, often even longer. But at some point, they reach the end of their life. As of now, the waste heap of discarded panels is still relatively low, about 250,000 metric tons. But by 2050, it's expected to grow up to 78 million metric tons. That would be more than 200 Empire State Buildings of old solar panels.

"Well, you know, now we can see that it's going to be a problem that, of course, in the next 10 years or 15 years is going to be a major crisis." adds Davis

Where old panels would pile onto the mountains of e-waste we're already struggling to deal with. The good news is that solar panels are recyclable, and it's already being done, mainly in the EU. The government in the US has made it compulsory for manufacturers to make sure their used panels get recycled. Facilities like this one already recover a good chunk of the materials. But there's also some bad news. The recovered silicon, for example, isn't of high purity, which means we can't really use it to make new solar panels. Instead, it goes into other stuff like shoe soles.

And then there's another problem. "The cost of recycling is relatively high, and that's partially at least because there's not yet that many modules to recycle.” This means in places without legislation – like the USA or China –it's still cheaper to throw old modules into landfills, including all the valuable materials they're made with.

Recycling needs to become profitable or we might have a real problem on our hands. "There would be many, many, many solar panels that are landfilled. I can't imagine that!"  Yun Luo is the CEO of ROSI Solar, a French startup that's come up with a new recycling process. It focuses on recovering the most valuable materials at high purity. "Actually, the economic return of the glass is not that high. So we try to integrate also how much value that has to be recycled. So silicon and silver together, it's about three percent of the total weight only. It has even more than 70 percent of the economic value."

With their recycling method, the company says, these materials could be recovered at a profit – and then go back into making more solar panels. They're currently working on opening their first plant at the end of 2022.

"In principle, if we can really establish a circular economy, we will not need to redo or remanufacture all these raw materials."

So the good news is that solar panels can be recycled. The bad news is that lots of them aren't and solar power is not entirely green. But that doesn’t mean we should shun it as the benefits far outweigh the cons. Instead, we should openly address its problems and figure out how we can fix them.

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