Some still question whether photovoltaic (PV) technology is good….whether it is a net benefit to the environment. What they are questioning, generally, is whether it takes more energy, or nearly as much energy to create the PV panels as they will produce over their lifetime. And as such, are they just an extension of fossil fuels or fossil fuel extenders?
What they are really talking about is the energy return on investment (EROI) or how much energy we can get out of the panels compared to the amount of energy it took to create the panels. Clearly, even if the panels only made a little more power than they create, it might not be worth doing.
Of course it takes energy to create photovoltaic panels. It takes energy to create most everything in our society. But once created, PV makes power. In this article I will present a number of reasons why PV is good even though it takes energy to create them.
Understanding how much energy it takes to create a PV panel is a knowable thing with a reasonable degree of confidence. The process of calculating this is known as life cycle analysis (LCA). An LCA can be done for anything that we produce. It is not an easy thing to do, but it can be done. We just have to decide the boundaries for the analysis. In other words, how far back do we go? Clearly we should look at the energy it takes to go from silica to silicon or silica or recycled glass to glass. We should look at the energy to recycle aluminum for the frames and so on for all the materials. This is all calculable once we establish the boundaries.
The aluminum for the frames is likely from recycled aluminum. Therefore, you don't need to take the calculation back to the mining of the bauxite ore. That was mined for the original use. However, you would count the energy to recycle and re-extrude the aluminum. You could even count the energy to collect the aluminum and truck it to the recycling center, etc. It is a tedious exercise but it is doable. And people have done it.
Very few people are LCA experts. But, there have been many LCAs completed for PV. Our National Renewable Energy Lab puts the energy payback for crystalline PV at around 3-5 years. This is not the solar industry marketing tool. This is our national scientists and universities. Many studies have shown similar results.
Of course there is no definitive EROI for PV. With LCA, we can never have an absolute answer, but that is far different than saying it is unknowable. And, we can and should continue to refine our analysis. We can argue about the details and assumptions in these LCAs and the result will change somewhat. But, most legitimate studies that I have seen indicate 5 years or less for panels that will make power for decades. This means PV creates 5 to 6 times the energy required for its manufacture.
We can always do more a more detailed analysis, but we are not doing this for many of the things in our society that we use every day for which there will never be an energy payback. In the case of PV, some cite the aluminum in the frames as a clear example of the significant energy it takes to make PV panels. However, there are many things that we make from aluminum every day and for which we are not expressing the same concern (e.g. the millions of aluminum cans that are used for beer and soda). Now, if the energy to recycle aluminum is a great concern, I would argue that we are better off to use the aluminum for PV than beer cans. It, of course, takes energy to make cars and still more energy to operate them. Still we produce and use cars by the hundreds of millions. What is the energy payback?
As a society, we choose how we use our fossil fuels. We could as easily choose to use wind power to create the solar panels and offset all of the fossil energy in the entire life-cycle of PV production with renewable energy. It’s our choice. There are issues of course with wind, and it takes energy to make and install wind turbines. But, once they are producing energy, they utilize much less fossil fuel.
Here is another way to look at it: Hypothetically, I could put a black painted drum in the sun to heat my water. But yes, the drum took energy to make, so did the paint. Where do we draw the line? Most people use a water heater that uses a fossil fuel or electricity which is generated by a mix of fuels including nuclear, oil, gas, coal, hydro, wind, etc. AND, the water heater tank still had to be made, just like my hypothetical drum. So which is greener my drum that uses the sun or the tank that uses fossil fuels. So, in this example, we can effectively zero out the embodied energy for the drum and tank and my drum still comes out ahead because from there on out, I use the sun, not the fossil fuels.
More tangibly, I use PV. These panels will make emission free power for 25 years. For me at my current rate that is about 90 megawatt-hours over the 25 years. It’s probable that it took much less than 90 MWH to produce the 15 PV panels. Think about how much electricity an average house uses every day, 365 days per year for 25 years. And then look at the small amount of material in my 15 solar panels. It’s hard to conceive of them not having a positive energy return on investment, even fully accounting for the life-cycle of the materials involved. Again, let’s let the data speak. Let’s get our best life cycle analysts to try to figure this out.
Additionally, while I am using these, I am reducing the power that has to be generated by dirty climate destroying power plants. Also, we can subtract from the equation the power plant emissions, fuel use, mining, transportation, etc. My PV panels should get credit for the otherwise dirty power and all its associated life-cycle costs that it offsets. Should we consider the energy it took to make the power plant…to make the steam or gas turbines…to mine the coal…. to process the nuclear fuel?
Additionally, there are inherent advantages to distributed generation that small-scale renewable such as PV provide, including environmental benefits, health benefits, grid reliability benefits. When summer temperatures spike, we currently ramp up our fossil fuel power plants to handle the peak. This creates more emissions and their associated health implications from the direct emissions. Solar, including distributed solar frequently produces more power at the same time our air conditioning load increases. Distributed generation also reduces losses due to transmitting power long distances. Those losses mean more fuel use. My PV system helps save that energy too.
Yes, nothing is perfect or perfectly clean. But we humans clearly are not ready to give up using energy. We haven’t begun to get serious about reducing fossil fuel use. There is much low hanging fruit. For example, how many people the Sunshine State heat their water in with solar? Pitifully few.
We are popping out PV panels by the millions now. There is certainly an economy of scale that reduces the embodied energy. For example, GE’s new PV plant will produce 400 megawatts of annual production capacity. At capacity, the new factory will produce enough panels per year to power 80,000 homes. First Solar is building a new plant that is capable of a total capacity approaching 700MW. And, panel production is getting more efficient, which further reduces the embedded or embodied energy - see Twin Creeks' new thin waffer process.
Beyond the numbers describing embodied energy or EROI or LCA, we have to consider the value of the less tangible benefits of PV. By using more solar and wind and hydro and other green power, we are transitioning our culture to renewable energy and reconnecting humans with our primary energy source, the sun, and moving us away from the fossil fuel era. Culture change is difficult, but with the growing deployment of PV, we are starting to move our culture.
Just as some people can point to studies that say humans are not contributing to climate change, that does not change the fact that there is overwhelming data that we are contributing and that most climate scientists believe this. Similarly, there are reportedly studies that show that PV is no good, yet many of our scientists and university professionals are demonstrating that PV is positive. Sure, we can choose not to believe our scientists, but frankly, who better to look to?
If there were only a billion people on the planet, this, along with many of the environmental problems would all be moot. But of course there's over 7 billion of us (or so the experts say) and most all of us are using energy. Frankly, we would be better off if we voluntarily stop making so many humans and get the population back in balance with the planet. In the mean time, PV and other renewable are better choices than fossil fuels.
Figuring out all the costs and benefits of PV is challenging. But ultimately, we are using our energy in this world for far worse things than PV, most of which never make emission free power for us for 25 years or more. In my analysis, PV still comes out ahead.
Scientific America - A life cycle analysis proves solar cells are cleaner than fossil fuel power generation.
Good Company - Life-Cycle Environmental Performance of Silicon Solar Panels
U.S. Dept of Energy - What is the energy payback for PV?
Kevin Carpenter , aka Treeguy, has worked as an environmental engineer in the private and public sectors for the past 22 years, focusing on environmental remediation and the cleanup of hazardous waste and brownfield sites. He is an enthusiast of solar energy including PV, SDHW and solar hot air. Outside of work he strives to live simply and sustainably in this ever more complex and disconnected world. He can be reached via Member email or comments to this blog.