Commentary: The Life Cycle of Renewables
Today sustainability commentator Bob Brecha tackles a thorny question: how much energy does it take to make wind turbines and solar panels.
Here’s a scary thought: What if all the effort being put into new wind turbines and solar panels is a waste of time and money because they don’t create as much energy as it takes to build and install them. And because of that, maybe they don’t help reduce greenhouse gas emissions either.
I get asked questions about this less often than I once did, but every once in a while questions about the overall energy or environmental footprint of wind and solar technologies even show up in professional journals and from contributors to reasonable blogs. As a scientist who is always willing to question ideas, I want to take these things seriously. For me, tough questions like these are part of how science is done. We turn every question on its head and examine it from all perspectives, poking and probing at an issue to see how far we can push our conclusions, and where our ideas and theories start to show cracks. That is science.
Critical, well-posed questions are important for the advance of science and technology. The statement that, “it takes more energy to manufacture a solar panel than it will ever generate” is fa one that can be examined by analyzing data – it’s not just a matter of opinion.
Engineers use something called a “life cycle analysis” to delve into questions like these, and it’s not that easy to figure out. There is a long chain of inputs to making a solar panel. There’s direct energy used in manufacturing, energy needed to transport panels to the installation site, and then you have to go all the way back to energy needed to build the factory that mines the minerals that go into the photovoltaic cells. In fact, the best example of life cycle analysis is probably the old Mother Goose rhyme, “This is the house that Jack built …”
But the point is, procedures can be well-defined and codified so that engineers and scientists anywhere can reproduce results or make modifications. The results are reported and checked, and the data are made available to others if needed. Science is an open process, and that characteristic is fundamental to not only its success, but also to the trust in scientists that citizens have typically had.
So now I’ve been holding you in suspense, because I haven’t answered the question I started with – do solar panels and wind turbines “pay off” in terms of the energy produced compared to the input energy for manufacturing? Not surprisingly, as time goes on manufacturing gets more efficient. Currently the energy cost of a solar panel is such that it takes about a year or so of operation to break even – maybe a little longer in place with less sun. And even considering the whole life cycle of processes, the overall greenhouse gas emissions for solar photovoltaic electricity are about 95% less than from natural gas – a good deal for energy use and for the climate.
We can look at wind turbines, or any other technology, in the same way. Over its lifetime, the greenhouse gas emissions from a wind turbine are even lower than for solar photovoltaic electricity, and it takes less than a year to gain back the energy used to make and install the turbine. That means the return on your energy investment is something like 30 or 40 to one – not bad for any kind of investment.
I’ve been concentrating here on a specific kind of question having to do with solar panels and wind turbines. But I think of this in broader terms, especially in these days of alternative facts and a confusion of voices promoting skepticism of any form of expert knowledge. It’s not that we should always blindly follow experts. However, there are many intelligent people who spend a great deal of time honestly thinking about how to analyze and solve problems. Critical thinking is important, but so is the ability to recognize when others may have deeper experience and knowledge than we do on some issues.
Bob Brecha is a professor of Physics and Renewable and Clean Energy at the University of Dayton, and Research Director at UD's Hanley Sustainability Institute. Follow him on Twitter: @BobBrecha