The Ultra-Efficient Farm of the Future Is in the Sky
Sourced from Wired
Five stories off the ground at Colorado State University, a highly unlikely garden grows under a long row of rooftop solar panels. It’s late October at 9 am, when the temperature is 30 degrees Fahrenheit and the wind is cutting. Not long before my arrival, researchers had pulled the last frost-intolerant crops out of the substrate underneath the panels, a total of 600 pounds for the season. In their place, cool-season foods like leafy greens—arugula, lettuce, kale, swiss chard—still grow, shaded from the intense sunlight up here.
This is no ordinary green roof, but a sprawling, sensor-laden outdoor laboratory overseen by horticulturalist Jennifer Bousselot. The idea behind rooftop agrivoltaics is to emulate a forest on top of a building. Just as the shade of towering trees protects the undergrowth from sun-stress, so too can solar panels encourage the growth of plants—the overall goal being to grow more food for ballooning urban populations, all while saving water, generating clean energy, and making buildings more energy efficient.
“When you stop and think about what we’re going to need as a society—our building blocks—it’s going to be food, energy, and water, just like it always has been,” says Bousselot. With rooftop agrivoltaics, “you can produce, especially in a primarily unused space, two of those things and conserve the third.”
And dramatically so: Early data is showing that rooftop agrivoltaics use a third as much water as full-sun rooftop agriculture does; because the crops are shaded, less water evaporates away. (Sensors under the panels here measure air temperature as well as the temperature and moisture content of the soil.) Even when water does evaporate, it’s actually a significant benefit for the solar panels overhead, which get less efficient the hotter they get. Basically, the plants and soil are “sweating” water vapor into the panels, cooling them and keeping them from overheating. Such a rooftop system can get even more efficient if it’s deliberately capturing rainwater, for instance in tanks to be drained outside of the rainy season.
From the Living Architecture Monitor
