Arguments
Sabin 33 #5 - Is solar energy worse for the climate than burning fossil fuels?
Posted on 3 December 2024 by BaerbelW
On November 1, 2024 we announced the publication of 33 rebuttals based on the report "Rebutting 33 False Claims About Solar, Wind, and Electric Vehicles" written by Matthew Eisenson, Jacob Elkin, Andy Fitch, Matthew Ard, Kaya Sittinger & Samuel Lavine and published by the Sabin Center for Climate Change Law at Columbia Law School in 2024. Below is the blog post version of rebuttal #5 based on Sabin's report.
There is overwhelming evidence that the lifecycle emissions1 of solar energy are far lower than those of all fossil fuel sources, including natural gas2. On average, it takes only three years after installation for a solar panel to offset emissions from its production and transportation. Modern solar panels have a functional lifecycle of 30–35 years, allowing more than enough time to achieve carbon neutrality and generate new emissions-free energy3.
A National Renewable Energy Laboratory (NREL) report released in 2021 examined “approximately 3,000 published life cycle assessment studies on utility-scale electricity generation from wind, solar photovoltaics, concentrating solar power, biopower, geothermal, ocean energy, hydropower, nuclear, natural gas, and coal technologies, as well as lithium-ion battery, pumped storage hydropower, and hydrogen storage technologies.” The report found widespread agreement that all modes of solar power have total lifecycle emissions significantly below those of all fossil fuels. The report found specifically that the total lifecycle emissions for solar photovoltaic (PV) and concentrating solar power (CSP) panels were 43 and 28 grams of CO2-eq/KWh (carbon dioxide-equivalents per kilowatt-hour), respectively. Coal, by contrast, generated lifecycle emissions of 1,001 grams of CO2-eq/KWh, and natural gas generated lifecycle emissions of 486 grams of CO2-eq/KWh.
Figure 1: Total lifecycle emissions for different energy sources. Source: NREL.
To be fair, there are some outlier studies. For example, one study examined a worst-case scenario in which the coal-powered manufacture of inefficiently sized solar PV cells may contribute to greater lifecycle emissions than the cleanest and most efficient fossil fuel plants (Torres & Petrakopoulou 2022). However, the conclusion that solar is worse for the climate than fossil fuels is not backed up by NREL’s more extensive survey.
In addition to having smaller greenhouse gas emissions, solar power likewise outperforms fossil fuels in minimizing direct heat emissions. A 2019 Stanford publication notes that, for solar PV and CSP, net heat emissions are in fact negative, because these technologies “reduce sunlight to the surface by converting it to electricity,” ultimately cooling “the ground or a building below the PV panels.”4 The study found that rooftop and utility-scale solar PV have heat emissions equivalent to negative 2.2 g-CO2e/kWh-electricity, compared to the positive heat emissions associated with natural gas, nuclear, coal, and biomass.
Figure 3: The 100-year CO2e emissions impact associated with different energy sources’ heat emissions, measured in g-CO2e/kWh-electricity. Source: M.Z. Jacobson (reproduced and adapted with permission)
Looking at academic scholarship from outside of the United States, a 2022 analysis from India’s Hirwal Education Trust’s College of Computer Science and Information Technology describes the global impact of solar panel heat emissions as "relatively small".5
Footnotes:
[1] Lifecycle emissions for energy technologies encompass emissions associated with the operation of an energy facility, such as combustion of fossil fuels. Lifecycle emissions also encompass upstream emissions associated with resource extraction, manufacturing, and construction of a facility, along with downstream emissions associated with decommissioning of a facility. And: Nat’l Renewable Energy Laboratory, Life Cycle Greenhouse Gas Emissions from Electricity Generation: Update (Sept. 2021) (Table 1). NREL calculates emissions intensity using grams of carbon dioxide equivalent per kilowatt-hour.
[2] Steffen Schlömer et al., 2014: Annex III: Technology-specific Cost and Performance Parameters, Climate Change 2014: Mitigation of Climate Change 1329, 1335 (2014); Carbon Footprint of Solar Panel Manufacturing, Cool Effect (June 1, 2021)
[3] What Is End-of-Life Management for Photovoltaics?, U.S. Dep’t of Energy Solar Energy Tech. Office (last visited March 25, 2024).
[4] Mark Z. Jacobson, Evaluation of Nuclear Power as a Proposed Solution to Global Warming, Air Pollution, and Energy Security, Dec. 22, 2019.
[5] Sudesh Nagu Kadam et. al, Solar Panel Heat Emission and Its Environmental Impact, 2 Int’l J. Advanced Rsch. Sci. Commc’n Tech. 3 (Dec. 2022), 113, 116.
Skeptical Science sincerely appreciates Sabin Center's generosity in collaborating with us to make this information available as widely as possible.
This is a very important summary of information and extremely useful, but I think certain points need more emphasis or examination: First I think it ought to be emphasized that the co2 advantage of solar pvs and the other renewable tech is based on current average use of fossil energy to make them, a part of their current embodied footprint. If these energy sources become renewable, say PVs, then the advantage grows. In fact, all renewable equipment makers should be using their own or others' renewable equipment to make more of them- a zero carbon bootstrap. To make this bootstrap complete the renewables makers need to iron out fossil fuel use down their whole supply chain.
Second, the statement below from the last reference posted above needs examination: "in addition to having smaller greenhouse gas emissions, solar power likewise outperforms fossil fuels in minimizing direct heat emissions. A 2019 Stanford publication notes that, for solar PV and CSP, net heat emissions are in fact negative, because these technologies “reduce sunlight to the surface by converting it to electricity,” ultimately cooling “the ground or a building below the PV panels.”4 The study found that rooftop and utility-scale solar PV have heat emissions equivalent to negative 2.2 g-CO2e/kWh-electricity, compared to the positive heat emissions associated with natural gas, nuclear, coal, and biomass."
This statement is true in certain circumstances and not in others. In the case of PVs in the desert in Arizona, the blackness of the collectors absorbs more sunlight than the desert would absorb. It isn't as reflective as snow, but the difference is significant. Of the absorbed sunlight today's PVs convert about 20% to electricity. The other 80% heats the PVs and is either radiated to the sky and ground or convected to the air. This could lead to a net addition to solar input to the climate energy balance at such a site. If the PVs replace grass or trees, the reflectivity issue more or less goes away but so does the latter's co2 trapping. This is however still in favor of PVs with respect to carbon balance, as another of your posts makes clear. In the case of PVs on buildings, the provided shade lowers air conditioning loads which is a clear advantage along with generating carbon free energy, and the reflectivity for most roofs is low. If the roof is highly reflective before PVs are installed, a part of the advantage is lost.
I think the last of your linked references is wrong in part. There we find:
"Use solar panels with reflective coatings. These coatings can help to reflect sunlight away from the panels, reducing
heat absorption.
Plant vegetation around solar panels. Vegetation can help to shade the panels and keep them cool." The first point, unless it means use selective surface coatings that reflect IR solar wavelengths the the PV can't convert to electricity, makes no sense. The second makes no sense. If the vegetation shades the panels the panels lose access to sunlight. For maximum benefit the panels need unrestricted access to sunlight.
Thank you for your thoughtful and productive critique, walschuler.
Sabin is actively maintaining this collection and we are delighted to help with that. We'll pass along your comments and work with Sabin to address them.
Published research literature will provide our improvements; if you have relevant references please do post them in this comment thread. As is said of software, with enough eyeballs all bugs are shallow. :-)