Abstract
Instead of constructing conventional greenhouses, existing fixed-tilt agrivoltaic racking can be converted to passive greenhouses with transparent plastic covering. The potential of this approach has not been tested experimentally, and there are two competing processes (soil temperatures beneath agrivoltaics are 2.6°C lower than control crops because of shading), but cold-frame and greenhouse temperature are higher than ambient because of the greenhouse effect, which enables extension of the growing season in northern latitudes. To fill this knowledge gap, this study explores the adaptation of an agrivoltaics rack into a plastic-covered greenhouse. Four thermal environments were monitored from late October through December in Ontario’s agricultural belt: air temperature under plastic-covered racks and control as well as root zone temperature (RZT) under plastic-covered racks and uncovered controls. The results showed that converting agrivoltaic racks into passive greenhouses increased average RZT relative to uncovered control during late autumn and early winter in Canada. From October to December, the under-rack RZT was 3.4°C warmer than the control, while the under-rack air was 5.4°C warmer. The highest temperature difference was observed in October and November, when the under-rack RZT was ~5.7°C and 4.2°C warmer than the control, respectively. Passive plastic enclosures alone are insufficient for deep-winter agriculture but can still contribute to crop season extension (16 days observed). These results suggest that agrivoltaic racks can be adapted into protected cultivation structures for northern-latitude agriculture, reducing the cost between 30-429% % compared to commercial hoop houses.