Long territory cats, weather vanes, and the occasional miser, the roofs are increasingly thick with solar panels. Rooftops of homes or businesses are ideal places to place them because the sunlight there is less obscured by shadows and roofs are generally unused space — better for the environment to add additional features. panels into an existing structure rather than clearing new land for a solar farm.
But even roofs that are covered with panels may not be as well utilized as they could be. A new area of science called rooftop farming asks the question: What if we also Cultivate them? These are not ordinary green roofs, but usually small gardens, but working farms. The panels will provide shade for the plants – actually boosting their productivity – as well as for the building, while reducing cooling costs and generating clean energy for the structure. The urban population is projected to be more than double by 2050. As people continue to migrate into cities, rooftop electricity can both feed people and make city life more bearable.
A roof is actually a rather difficult place for plants to grow. Up there, a plant is suffering from strong winds and constant bombardment from sunlight because there aren’t any trees around for shelter. (Accordingly, the hardy cactus is the preferred plant for green roofs.) Yes, it needs light, but not much. “Plants will go into what we call photorespiration mode, where it’s too bright and sunny for them to photosynthesize effectively,” said Jennifer Bousselot, a rooftop agronomist. “They start trying to take oxygen and break it down, instead of carbon dioxide, and so they waste energy.”
.jpg)
In contrast, think about how a forest works: All plants, with the exception of the tallest trees, receive some amount of shade. For the trees closest to the forest floor, the light is diffused, bouncing off the surfaces around them. The surrounding tall trees also make them less exposed to wind and temperature changes than if they were grown outdoors.
The idea of agrivoltaics is to recreate this forest environment for plants. In Colorado, scientists experimented with electric terrestrial gardens and found that the plants tend to grow larger in the shade. It can be a physiological response to the need to absorb more light and it is great for leafy plants like lettuce because it increases their production. Pepper trees too, produce three times more fruit in shallow power systems as in full sun. In addition, shade plants need half as much water as other plants because there is less sunlight to evaporate.
The same concept would work on a roof: Solar panels would provide shade that would make the trees happier and less thirsty. Bousselot has found that under roof shingles, it is cooler in summer and warmer in winter, and the panels act as windbreaks. Plants would not be food crops to benefit the surrounding landscape — adding native plants to a rooftop farm, for example, would provide flowers for local pollinators. Scientists are also experimenting with designs for semi-transparent solar panels, should theoretically work better for species that need less sunlight than outdoors, but not full shade.
