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Taylor: Welcome to Transforming Energy: The NREL Podcast, brought to you by the U.S. Department of Energy’s National Renewable Energy Laboratory. We’re highlighting the latest in clean energy research and innovations happening at the lab. It’s Wednesday, November 15. I’m Taylor Mankle.  

Kerrin: And I’m Kerrin Jeromin. Today, we’re talking about solar innovations, we’re talking decarbonizing the transportation sector, and we’re talking improving wind turbine blades using AI.  

Taylor: Ooooo 

Kerrin: Lots of exciting research —let’s get into it!  

Taylor: Let’s do it! NREL researchers have found that the rapid adoption of zero-emission electric vehicles will move the nation close to an 80% or more drop in transportation greenhouse gas emissions by 2050 from what it was in 2019. Which is huge because transportation ranks as the largest source of greenhouse gas emissions in the United States and the fastest-growing source of emissions in other parts of the world.  

Kerrin: As you may already know, most vehicles today burn fossil fuels, which produce those greenhouse gases—or heat-trapping gases that contribute to the warming of our planet. But a zero-emission vehicle relies on alternate sources of power, such as batteries or hydrogen. NREL’s research published in Nature Communications, says that while there is no silver bullet, eliminating tailpipe emissions would be a major factor in reducing greenhouse gas emissions.  

Chris Hoehne: “I guess to ground it in some numbers, you know, the transportation sector is somewhere around a quarter, usually, of greenhouse gas emissions in the United States and about two-thirds of all of that is personal vehicle travel. So almost a third is like freight in that sector. But a large majority of transportation, you know, two-thirds of it is, is, you know, people driving their cars, so electrifying that, gets us close to, I would say, two thirds of the way there, basically.”  

Taylor: That was Chris Hoehne, a mobility systems research scientist at NREL and the lead author of the research paper. He and the other researchers ran thousands of computer simulations on the steps needed to decarbonize passenger and freight travel.  

Kerrin: Hoehne’s group analyzed 50 deep decarbonization scenarios by performing more than 2,000 simulations with a computer model called Transportation Energy & Mobility Pathway Options, or TEMPO. That’s a fun acronym and a really important tool!  

Taylor: We love the acronyms here. Absolutely, TEMPO is an all-inclusive transportation demand model that covers the entire country. It really allows researchers to forecast different scenarios in the transportation sector. Let’s break this down… imagine an orchestra—  

Kerrin: Okay, I like this. Let’s go with a music-themed acronym and tell me more about it. Let’s go.  

Taylor: Exactly, right right. So you got to stick with me here. So an orchestra has a percussion section, strings, brass instruments, all of it. The TEMPO tool acts as a conductor, who might call for more percussion or brass.  

Kerrin: Or cowbell?  

Taylor: Or cowbell. Only instead of music it’s things like adding in more EV charging stations, or details about the sociodemographics which can impact transportation choices of a population. It allows our researchers to play with the levels on this orchestral soundboard and hear what it sounds like with more stand-up bass and less woodwinds if you will.  

Kerrin: I got it! That’s an amazing metaphor, and I’m here for it. Thanks, maestro! So, TEMPO lets us try out different scenarios to see what could happen and how we could reach our goals of reducing emissions.  

Taylor: Yes! And in this case, it found a really lovely melody that can help us address the climate crisis and air quality issues through clean transportation solutions.  

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Kerrin: Okay, if our last story was about making huge changes in a large sector, this one is all about the small scale.  

Taylor: Hm, could we say micro scale?  

Kerrin: Absolutely, we’re getting down to the atomic size of chemical elements in this story. NREL researchers have found a way to get more efficiency out of solar cells by carefully designing the materials in the cell stack—or essentially the layers of materials within it. The research is part of an effort to make III-V solar cells more affordable.  

Taylor: III-V solar cells have record efficiency. This type of cell captures an enormous amount of sunlight to convert to energy. But they are costly to make and typically are only used in outer space applications.  

Kerrin: The III-V cells get their name from the periodic table of elements. As you might remember that one from high school.  

Taylor: Mm-hmm. Yeah, dust that one off.  

Kerrin: For sure. The table of elements is split into groups: Group III contains the elements Gallium and Indium while group V contains the elements Arsenic and Phosphorous, among others. Every III-V compound is a combination of at least one atom each from these groups, and sometimes multiple from either group. Still following here? So, one example of that is Gallium Arsenide.  

Taylor: Which is a very important thing in the takeaway to this story… bottom-line, III-V solar cells are good at what they do and as with many of our stories we’re focusing on how NREL researchers just made them even better.  

Kerrin: Exactly. So, here comes some difficult words—are you ready?  

Taylor: I’m ready. 

Kerrin: Prepare yourself for this. 

Taylor: I’m ready.  

Kerrin: Okay, so, through both computational and experimental studies, those are not the hard words, by the way, NREL scientists grew a gallium arsenide heterojunction solar cell using dynamic hydride vapor phase epitaxy.  

Taylor: Well said, Kerrin! 

Kerrin: Thank you very much. Those are not my words, I took that directly from this story which you can read in full on nrel dot gov. This resulted in a certified efficiency of 27%, the highest efficiency ever reported for a single-junction gallium arsenide cell grown using this technique.  

Taylor: Hmm, and this goes beyond III-V cells! This research provides a roadmap to improving other types of solar cells, like silicon or perovskite cells.  

Kerrin: Small scale but mighty improvements!  

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Taylor: You know Kerrin, you can’t spell airfoil without AI.  

Kerrin: Uh, that- that’s correct. Yeah that’s right; it’s in there.  

Taylor:. Our next story is about improving the design of airfoils, like aircraft wings or wind turbine blades, by using artificial intelligence, or, as I said: AI. Building and testing airfoil designs has traditionally been expensive and time consuming, which makes it complicated when policy regulations are changing, customer demands are shifting, and the technology is constantly innovating.  

Kerrin: NREL computational science researchers are working to reduce cost and time while providing high-fidelity insights. By providing more accurate inputs and using AI, we need fewer iterations to get the best airfoil design!  

Taylor: In this instance, the AI comes from a neural network, which is a computer system modeled on the human brain. These networks perform well on human-oriented tasks such as natural language processing to decision making. In this particular scenario, they may potentially help identify optimized airfoil shapes. The neural network is invertible, meaning it can understand the relationship going both ways.  

 Kerrin: So the AI gets the relationship between airfoil shapes and their aerodynamic and structural properties from both sides.  

 Taylor: Wild.  

 Kerrin: An airfoil designer could specify a structural property and get information on the shape, or specify the shape and get info on the structural property. Bidirectional, as it’s called.  

 Taylor: Exactly. This method could be a real game-changer for creating better airfoil design, which in turn means more efficient wind blades, leading to more renewable energy.  

 Kerrin: And we love that.  

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 Kerrin: Alright, Taylor, how about we end this episode with a quick note about some NREL employees giving back? 

 Taylor: Yes, please, Kerrin! Let’s do it! 

 Kerrin: Ok well, Veterans Day was observed last week. NREL employs a lot of veterans, and we want to shine a light on them.  

 Taylor: No doubt. Our Veterans Employee Resource Group at NREL provides a platform for our veterans, current members of the military reserve, and supporters. The group has networking opportunities for NREL’s veterans and members of the military reserve and volunteers in our local community.  

 Kerrin: You love a fun fact I know you do.  

 Taylor: Oh, yeah.  

 Kerrin: Here’s one for you: One of their most recent volunteer efforts was at NREL. In honor of Veterans Day, the group partnered with Volunteers of America and hosted an event where volunteers spent their lunch hour making 300 sandwiches for those in the community who are struggling. 300 sandwiches going out to people in need.  

 Taylor: We love to hear that. Thank you to our Vets for their service and for their ongoing work at the lab. As Thanksgiving approaches, I’m reminded that at NREL we’re also a community. And it’s important to take time to give back.  

 Kerrin: Absolutely. No matter who you are, where you are, please, give back if you can. Ending that on a very inspiring note, Taylor, thank you for that. Okay listeners, that’s all we have for you this week, thanks so much for joining us. If you want to learn more about this podcast or provide episode suggestions, or praise for Taylor and I, we’ll take it! You can email us at podcast@nrel.gov.  

 Taylor: And be sure to give us a positive review on your favorite podcasting app. Thanks again and we’ll be back in two weeks with more news from the lab.  

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Kerrin: This episode was adapted from NREL articles from October and November 2023 authored by Wayne Hicks and Justin Daugherty. Special thanks to Nataleah Small. Our theme music is written and performed by Ted Vaca and episode music by Chuck Kurnik, Jim Riley, and Mark Sanseverino of Drift BC. This podcast is produced by NREL’s Communications Office and recorded at the National Renewable Energy Laboratory in Colorado. We express our gratitude and acknowledge that the land we are on is the traditional and ancestral homelands of the Arapaho, Cheyenne, and Ute peoples. We recognize and pay respect to the Indigenous peoples from our past, present, and future, and are grateful to those who have been and continue to be stewards of this land.  

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