Your roof garden can be a solar farm

Long territory Among cats, weather vanes, and occasional violinists, the roofs of solar panels are getting thicker and thicker. The roof of a home or business is an ideal place to place them, because the sunlight there is less obstructed by shadows, and the roof is usually an unused space-adding panels to the existing structure is more environmentally friendly than clearing new land for a solar farm good.

But even the panel-covered roof may not be fully utilized as it should be.A new scientific field called rooftop agricultural photovoltaic asks: if we return Plant crops under them? These are not ordinary green roofs, usually small gardens, but working farms. These panels will provide shade for plants—in effect increasing their yield—as well as shade for buildings, while reducing cooling costs and generating clean energy for the structure.Estimated urban population More than twice By 2050. As people continue to migrate to the metropolis, rooftop agricultural photovoltaic power generation can not only feed people, but also make urban life more pleasant.

The roof is actually a very challenging place for plants to grow. There, the plants are exposed to the constant bombardment of strong wind and sunlight because there are no trees around to provide shelter. (Therefore, hardy succulents are the plants of choice for green roofs.) Yes, plants need light, but not so much. “Plants will eventually enter what we call photorespiration mode, in this mode, because of too bright and sunlight, they can not effectively photosynthesize,” Colorado State University horticulturist Jennifer Busello who is studying rooftop agricultural photovoltaics (Jennifer Bousselot) said. “They started trying to absorb oxygen and break it down instead of carbon dioxide, so they wasted energy.”

Photography: Thomas Hickey

In contrast, think about how the forest works: all plants, except the tallest trees, receive a certain degree of shade. For the plants closest to the forest floor, the light is diffuse, reflecting off the surfaces around them. The tall trees around them also make them less affected by wind and temperature fluctuations than when growing in the open air.

The idea of ​​agrivoltaics is to replicate this forest environment for crops.In Colorado, scientists have been experimenting with terrestrial agricultural photovoltaic gardens and found these plants Tend to get bigger In the shadows. This may be a physiological response that needs to absorb more light, which is very useful for leafy crops such as lettuce because it can increase yield.Pepper plants also produce Triple the fruit In agricultural photovoltaic systems, such as in full sunlight. As a bonus, shaded plants need about half of the water because less sunlight is caused to evaporate.

The same concept applies to roofs: solar panels will provide shade, make plants happier and reduce thirst. Bousselot found that under the roof slab, it is cool in summer and warm in winter, and the roof slab acts as a windbreak.These plants do not have to be food crops to benefit the surrounding landscape-for example, adding native plants to rooftop agricultural photovoltaic power generation will Local pollinator. Scientists are also playing with design Translucent solar panelsIn theory, this is more effective for species that require less sunlight than the open air, but it is not completely shaded.

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