Growing Plants—And Providing Solar Energy

IRA FLATOW: We end this hour with one of my favorite topics– the intersection between technology and agriculture. Now, you all know that food is one of our basic needs. And I don’t have to tell you that as the population of the world grows, we’re going to need a lot more of it while working with the same amount of space that we’ve got. That is a real challenge. And this is where my new favorite concept comes into play– agrivoltaics. This is a farming setup that mixes water, energy, and plant growth all in one space.

Well, let me tell you what I mean. Solar panels collect energy from the sun’s rays, and underneath these panels is where plants grow. So this setup takes less water than the traditional way of farming, all in all, making this a more sustainable way to grow food and create energy. That’s why I am so psyched to learn more about this. Joining me to talk about the promise of agrivoltaics is Dr. Chad Higgins, associate professor of biological and ecological engineering at Oregon State University in Corvallis. Welcome to Science Friday.

CHAD HIGGINS: Thanks. Happy to be here.

IRA FLATOW: Nice to have you. All right, let’s get into this. Let’s start with just how this setup works. To most people, it would seem a little backwards that plants do well grown under solar panels.

CHAD HIGGINS: Right, the reaction from a lot of people is, wouldn’t there be not enough sun?

IRA FLATOW: Right.

CHAD HIGGINS: And in certain circumstances, they would be correct. Your intuition is right there. But where it gets interesting is that plants actually don’t need full sun. And we can design rays such that we only take the sun that the plants don’t use or don’t want or don’t need.

IRA FLATOW: Huh. So what do the plants do with the extra sun normally when they have it?

CHAD HIGGINS: So what do you do when you get too hot?

IRA FLATOW: You sweat.

CHAD HIGGINS: You start sweating, right. Plants do the same. So they have to keep their temperature at a certain rate, a certain level, just so they can do their thing with photosynthesis. So when they get too much sun, they get too hot. So they take more water, and they sweat out that water. This is why when you take that excess energy away and you keep them in a more comfortable zone, they use less water.

IRA FLATOW: Wow, that really makes sense. So they’re not sweating away the unneeded water and you’re not wasting water in irrigation. Now is there a special kind of crop that works best with this setup?

CHAD HIGGINS: There’s many crops that could do quite well. And there’s a variety of studies by myself and my colleagues in Arizona, Ohio, Massachusetts, where they’ve shown that certain varieties of peppers, tomatoes do really well. We’ve shown that potatoes do really well, beans as well. Some of the ones that don’t do quite well tend to be the ones that are like corn that can take a lot of sun and produce a lot. So yeah, there’s some that work really well and some that might not be the best choice.

IRA FLATOW: Because that brings me to the question when I talk about this with people, the first question they say is, how do you actually harvest the plants? How are you going to get a tractor under those solar panels?

CHAD HIGGINS: So my response to that is, you’ve only seen sun prioritizing solar rays. You haven’t seen one that’s built for dual use. And it’s really pretty easy technically. There’s a couple of ways you can do it. One is you can raise up the panels so you drive the tractors underneath. That’s the knee jerk design reaction. It’s also the most expensive way to do it. The second way is you can space out the panels wide enough so that it’s wider than your typical equipments you go between. And the one that we’re investigating a lot lately is articulated panels so that they actually tilt vertical up and out of the way. You make your tractor pass, and then they tilt back, facing the sun.

IRA FLATOW: Wow, OK. How much of America’s farmland would you have to change to an agrivoltaics system for us to really see the benefits of this method?

CHAD HIGGINS: Yeah, 1% to 3% would get us to most of the sustainable energy targets, as lined out by the Green New Deal proposal and other renewable targets that have been laid out.

IRA FLATOW: Now I understand that at Oregon State, you run an experimental agrivoltaics site. What are the challenges with this type of system that you need to solve to make this work? Because I can’t wait to see this.

CHAD HIGGINS: Well, your question you asked was really a real pertinent one, is, what’s the crop? So this Earth that we live on is wonderful and varied, but that makes designing systems to work everywhere really challenging. So what we’re trying to get at is understanding the physics, the biology, the chemistry that go on behind the scenes so that we can, for a place in our climates, design an array and crop combination that works together really, really well.

IRA FLATOW: Well, my question then is, do you think it’s going to take convincing farmers to buy into this setup?

CHAD HIGGINS: The beauty of this is that, number one, if done well, it is a profitable endeavor, meaning that the farmer would make substantially more money per acre than they would just growing crops. So there is, I believe free market forces will help push the sustainable technology forward. And the other thing is we don’t have to convince everybody. It’s only 1% to 3% of the farmland. That’s 1 in 100, 1 in 30.

IRA FLATOW: This is Science Friday from WNYC Studios. Wow, and are there any federal or state tax incentives like I got when I put my solar panels on my roof?

CHAD HIGGINS: Same, and I can’t speak to every state, but here, there’s tax incentive programs and rebates for solar. Those tend to change year by year. And your listeners would probably want to check with their local bylaws and tax laws and so on. But pretty much in the vast majority of states, there’s some incentive for the solar beyond just the money that you would make from selling electricity as a crop.

IRA FLATOW: Well, my next question is, I don’t have a farm. I have a backyard garden. Will it be possible for me to go into Lowe’s or a big box store and buy a setup for my own garden? And looking forward, if enough people do this, could you get that 1% to 3% of the population, instead of just the farmers?

CHAD HIGGINS: I’ll have to do that calculation. I actually haven’t done that calculation yet, but I can get back to you on that, Ira. I don’t know if you can buy one yet, but I know of at least five startup companies that are working to design that kind of setup for home enthusiasts. And in your garden, those of you who are master gardeners, you might think of things like co-planting and using overstory and understory crops. It’s a very similar idea, what the overstory is to solar panels.

IRA FLATOW: And tell me about where you see this going. Can you lay out a plan or a schedule for adopting agrivoltaics? What’s it going to take?

CHAD HIGGINS: There’s a couple of things that it takes. The one thing that the technical limitation right now has to do with the larger power grid that we have in our nation. As an example, a farmer comes to me, a grower comes to me and says, hey, Chad, I really want to try this on an acre and see if it works for me. And if it works and I make the money that your calculations show, I’ll expand it out.

And the first thing I have to do is, I say, OK, where’s your farm? And I look and I see where’s the closest substation to them. And if that substation is too far away from their farm, more than a couple of miles, then I have to say, it’s probably not worth it because you would have to put in a whole bunch of power infrastructure to get to the substation.

The next thing I do is I have to look at the substation because some of them are full. The pipes are full. You can’t put more power through them. So even if a substation is there, you might not be able to send power to it. So that’s the big technical limitation, is having our American family farmers have access to the grid in a way that they would need to. And that hopefully will be built out in some of the infrastructure deals that are going on.

IRA FLATOW: Chad, we have run out of time. I’m really looking forward to this idea. And you’re making some progress, and farmers around the country are making progress with this. Thank you for taking the time to be with us today.

CHAD HIGGINS: Thanks, Ira. It was a pleasure to be here.

IRA FLATOW: Dr. Chad Higgins, associate professor of biological and ecological engineering at Oregon State University in Corvallis.

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