Solar Panels Might Not Help CO2 Reduction Any Time Soon

by Emil Morhardt

The main considerations in whether and where to install photovoltaic (PV) panels are how much sun there is, and how much the panels cost. Right? Not necessarily. Engineers at Arizona State University have just published a paper pointing out that if a goal of installing photovoltaics is to decrease greenhouse gas emissions, it would be prudent to consider the emissions from manufacturing—which vary significantly by panel type—how long they stay in the atmosphere, and whether or not the installation is competing with other renewable energy sources rather than with fossil fuel burning. Because of the greenhouse gases associated with manufacturing, all panel installations increase greenhouse effects in the short term, although the initial two-year effect is to reduce them owing to sulfur and nitrogen oxides released from power plants during manufacture.

In their lifecycle modeling, Ravikumar et al. (2014) concluded that in California and Wyoming it takes at least six years to get to the point that the panels are reducing the greenhouse effect, and it might take as long as eleven years in Wyoming and twelve years in California. This five-to-six-year difference has to do with the choice or technology and the primary energy source where the panels are installed. Chinese polycrystalline panels use more energy to refine the panel components than do the cadmium telluride panels made in Malaysia; China gets most of its energy from coal, whereas Malaysia gets about half of its energy from the less-polluting natural gas, and ten percent of it from hydroelectricity; and installations in California are competing with the equally-renewable hydroelectric energy which makes up a significant part of the electricity on the grid; Wyoming is more dependent on coal. In all cases however, the model calculates that the sooner photovoltaics are deployed, the better.

This blog summary greatly simplifies a complex and insightful lifecycle modeling effort that seems to me to serve as a good introduction to the process for the uninitiated. I’d recommend reading the whole paper.

Ravikumar, D.T., Seager, T., Chester, M., Fraser, M.P., 2014. Intertemporal Cumulative Radiative Forcing Effects of Photovoltaic Deployments. Environmental Science & Technology  Abstract and a figure at:

4 thoughts on “Solar Panels Might Not Help CO2 Reduction Any Time Soon

  1. This is a good summary, Emil! Thanks for reading the paper carefully and appreciating the complications.

    There were two take-home points for us:
    1. Although solar photovoltaic (PV) policies are often motivated by CO2 reduction goals, the electricity used in the manufacture of the panels is a huge factor in CO2 effectiveness. That means that the success of California greenhouse gas policies is determined by Chinese electricity technologies! And,
    2. Although we usually think the best place to put PV panels are in the sunniest locations, from a CO2 perspective, it might be better to put the panels in locations that have less sun, but use more coal. That way, the electricity that IS produced will displace dirty coal, rather than cleaner sources.


    • Thomas,

      Thanks very much for your comments. Just the points I was ineptly trying to get at. With a well-mixed global atmosphere it doesn’t matter much where the CO2 is produced, and what you want to do is keep it from being produced there by providing plenty of non-fossil energy locally.


  2. Pingback: Energy Vulture covered our work on rare plants and solar! | Kara A. Moore

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