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Published on April 3rd, 2013 | by Stanford University


Global Solar Photovoltaic Industry Is Likely Now A Net Energy Producer

April 3rd, 2013 by  

The rapid growth of the solar power industry over the past decade may have exacerbated the global warming situation it was meant to soothe, simply because most of the energy used to manufacture the millions of solar panels came from burning fossil fuels. That irony, according to Stanford University researchers, is coming to an end.

For the first time since the boom started, the electricity generated by all the world’s installed solar photovoltaic (PV) panels last year probably surpassed the amount of energy going into fabricating more modules, according to Michael Dale, a postdoctoral fellow at Stanford’s Global Climate & Energy Project (GCEP). With continued technological advances, the global PV industry is poised to pay off its debt of energy as early as 2015, and no later than 2020.

“This analysis shows that the industry is making positive strides,” said Dale, who developed a novel way of assessing the industry’s progress globally in a study published in the current edition of Environmental Science & Technology. “Despite its fantastically fast growth rate, PV is producing – or just about to start producing – a net energy benefit to society.”

The achievement is largely due to steadily declining energy inputs required to manufacture and install PV systems, according to co-author Sally Benson, GCEP’s director. The new study, Benson said, indicates that the amount of energy going into the industry should continue to decline, while the issue remains an important focus of research.

“GCEP is focused on developing game-changing energy technologies that can be deployed broadly. If we can continue to drive down the energy inputs, we will derive greater benefits from PV,” she said. “Developing new technologies with lower energy requirements will allow us to grow the industry at a faster rate.”

The energy used to produce solar panels is intense. The first step in producing the silicon at the heart of most panels is to melt silica rock at 3,000 degrees Fahrenheit using electricity, commonly from coal-fired power plants.

As investment and technological development have risen sharply with the number of installed panels, the energetic costs of new PV modules have declined. Thinner silicon wafers are now used to make solar cells, less highly refined materials are now used as the silicon feed stock, and less of the costly material is lost in the manufacturing process. Increasingly, the efficiency of solar cells using thin-film technologies that rely on earth-abundant materials such as copper, zinc, tin, and carbon have the potential for even greater improvements.

To be considered a success – or simply a positive energy technology – PV panels must ultimately pay back all the energy that went into them, said Dale. The PV industry ran an energy deficit from 2000 to now, consuming 75 percent more energy than it produced just five years ago. The researchers the industry to pay off this energy debt as early as 2015, thanks to declining energy inputs, more durable panels and more efficient conversion of sunlight into electricity.

Strategic implications

If current rapid growth rates persist, by 2020 about 10 percent of the world’s electricity could be produced by PV systems. At today’s energy payback rate, producing and installing the new PV modules would consume around 9 percent of global electricity. However, if the energy intensity of PV systems continues to drop at its current learning rate, then by 2020 steady growth of the industry would consume less than 2 percent of global power supplies.

This may not happen if special attention is not given to reducing energy inputs. The PV industry’s energetic costs can differ significantly from its financial costs. For example, installation and the components outside the solar cells, like wiring and inverters, as well as soft costs like permitting, account for a third of the financial cost of a system, but only 13 percent of the energy inputs. The industry is focused primarily on reducing financial costs.

The PV industry can continue to reduce the energetic costs of producing panels in different ways, such as using fewer materials or switching to producing panels that have lower energy costs than technologies based on silicon. The study’s data covers the various silicon-based technologies as well as newer ones using cadmium telluride and copper indium gallium selenide as semiconductors. Together, these types of PV panels account for 99 percent of installed panels.

The energy payback time can also be reduced by installing PV panels in locations with high quality solar resources, like the desert Southwest in the United States and the Middle East. “At the moment, Germany makes up about 40 percent of the installed market, but sunshine in Germany isn’t that great,” Dale said. “So from a system perspective, it may be better to deploy PV systems where there is more sunshine.”

This accounting of energetic costs and benefits, say the researchers, should be applied to any new energy-producing technology, as well as to energy conservation strategies that have large upfront energetic costs, such as retrofitting buildings. GCEP researchers have begun applying the analysis to energy storage and wind power.

By Mark Golden, Precourt Institute for Energy

This article was originally published in the Stanford Report.

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About the Author

-- Mark Golden works in communications for Stanford University, writing on the university's broad range of energy research. Coverage spans more than 200 faculty members, as well as dozens of independent labs and academic departments from fundamental sciences to law.

  • Typo:
    “The researchers the industry to pay off this energy debt as early as 2015”

    should be:
    “The researchers expect the industry to pay off this energy debt as early as 2015″

  • Otis11

    A few things everyone is overlooking:

    Yes, last year was the first year that solar panels generated more power than was consumed in their construction, but the biggest factor in that is because we are in a period of exponential growth for solar cells. If it takes 4 years for a solar panel to pay back the electricity it took to make it, but we made 30% of the global supply of panels last year, of course we’re going to be in an energy deficit! That’s basic mathematics and is in no way a reflection of the technology! (This actually happens in drilling for oil too… but it’s all proprietary so we don’t generally hear about the numbers)

    Secondly, the vast majority of our solar panels are less than 5 years old! Given it takes ~4 years for energy pay back, we wouldn’t expect it to be a net energy gain until right around now… And actually even a little later given that the growth is not linear and the average of these panels is less than 2.5 years old.

    Third, what this says is we have created more electricity with our PV cells than we consumed in making them… and they still have 20+ years left to make more power!

    The video did get these right, but as they only mentioned it in a single sentence about 3/4 the way through and they weren’t mentioned in the article, thought I’d bring it up.

    • Bob_Wallace

      ” last year was the first year that solar panels generated more power than was consumed (in annual panel manufacturing)”

      I agree, this is a meaningless statistic.

      We could have reached that point in the second year of panel manufacturing by simply not manufacturing any panels in year two.

      • Otis11

        Yeah, what this actually tells me is that we’re not ramping up production fast enough. We should just be re-investing all of the generation in making more generation capacity until we have enough… or at least until we get close so that we can scale down in a controllable manner…

    • Completely agree. Unfort., this was one story I didn’t see until after it was published. I probably would have declined if I had. Or would have added a big preface. At least the message was a “net positive,” and that’s probably all that most readers will take out of it.

      • Otis11

        Well, honestly I thought it was an interesting article. What I got from it – Solar panels as a whole have already paid for themselves. While individual panels may still be in the paying back stage, as a whole it’s all all free electricity now. (well, free from an energy perspective, there’s still some R&D costs to recoup, but that shouldn’t take long)

        • Not really. Unfortunately, most of the energy used to PRODUCE solar panels (and much of the energy used to produce wind turbines) came from soot-belching, coal-fired power plants in China, and most of the energy REPLACED by these devices would have been produced in clean power plants with state-of-the-art “scrubbers” in North America, Europe & Australia.

          So, Chinese workers get emphysema, American workers get to collect unemployment, and American & European environmentalists get to feel self-righteous. What a deal.

          • Bob_Wallace

            China is cleaning their grid. And they are using wind and solar along with hydro to do that cleaning.

  • beernotwar

    Is this a fair analysis? If we weren’t using fossil fuels to create solar energy generation capacity, wouldn’t a similar amount of fossil fuel be burned to create some other kind of generation capacity? How many coal, nuclear or natural gas plants haven’t been constructed because of new solar capacity? The amount of fossil fuels that would have been burned to construct those plants needs to be subtracted from the energy used to create the solar capacity.

    • good call. this was definitely not my favorite story/study of the month.

    • No, it wouldn’t. Fossil fuels and nuclear require far less energy (and money) than solar to create the same amount of generation capacity.

      In fact, it’s even worse than that, because of the intermittent availability of solar power. Solar and wind power can replace some of the fuel used by coal and natural gas power plants, but they can’t actually replace much generation capacity. Maybe it can replace a little bit of capacity in places where air conditioning load means that peak demand occurs during the daytime in mid-summer, which tends to coincide with better solar output, but most solar and wind capacity have to be backed up with additional fossil fuel generation capacity, as well (typically natural gas).

      • Bob_Wallace

        Wrong, Dave.

        New wind and new solar are less expensive than new nuclear and new coal. And that is even before we add in the external costs of coal.

        Wind will be able to replace more than 30% of US capacity and solar more that 5% before any additional changes to the grid are needed. In fact, due to the amount of NG capacity installed recently, the total amount of wind and solar may be well higher than 50% of total generation.

        Germany is looking like they won’t need additional storage until they are more than 80% wind and solar.

  • Speller

    Interesting article. But please spell check your headline. You are missing an ‘n’.

  • The energy cost of solar does not matter at all, if solar power is used for manufacturing new solar panels. Silicon refinery should be able to adjust its output according sun and wind.

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