Abstract
Combining green roofs with solar modules can protect plants and produce energy in cities. Growing crops in this system is called rooftop agrivoltaics (RAV) and can complement current urban agriculture efforts. We evaluated a group of five leafy green crops (arugula, kale, lettuce, spinach, and Swiss chard) under different solar modules over 2 years at two locations. Data measurements were taken for fresh and dry weight (FW and DW, respectively), stomatal conductance (SC), plant size at harvest (PSH), and microclimate data. Treatments included a polycrystalline opaque silicon module, a cadmium telluride (CdTe) frameless opaque module, a 40% semitransparent CdTe module, and a full sun control. Four of the five leafy greens produced higher FW and DW under the 40% semitransparent modules compared with other treatments and the full sun control, except spinach. Most species also produced larger PSH under the photovoltaic (PV) module treatments compared with the full sun control. Leafy greens under the module treatments resulted in lower SC; however, lettuce and Swiss chard grown under the semitransparent module treatment produced higher SC compared with all other treatments. This research shows that incorporating photovoltaics on rooftop gardens influences the yield and SC of select leafy green crops. Although FW and DW mostly decreased under the deep shade treatments (opaque module, frameless module, and bifacial module) SC decreased, possibly due to less solar radiation on the leafy greens, reducing water use. Understanding the growth characteristics and growing environment of high-value crops like leafy greens will increase understanding of what food crops are suitable for RAV systems.