Synergistic photon-use in semi-transparent photovoltaic-photosynthesis systems for agrivoltaics

Agrivoltaic systems integrate photovoltaic energy systems with agricultural practices on shared land. Installation of overhead photovoltaic devices can benefit crops in certain situations, for example by creating partial shade in high light environments, improving water-use efficiency due to microclimate effects, and protecting crops from extreme weather events. Nevertheless, integrating solar cells in agricultural systems imposes a fundamental constraint on biological productivity due to the partitioning of incident sunlight between either electricity generation or plants. Semi‑transparent photovoltaics present a promising technology for integrating solar energy production into agriculture and other multi‑use solar landscapes. However, current approaches to assessing the biological productivity of semi-transparent agrivoltaic systems are relatively slow as they typically rely on crop yields and therefore require full cropping cycles before results can be obtained.

Here, we present a lab‑scale experimental framework for combined measurements of photosynthesis and electric power generation on plant leaves positioned beneath a semi‑transparent photovoltaic panel. We present the results of simultaneous measurements of electricity generation and photosynthesis using four different semi‑transparent photovoltaic devices and two plant species exposed to a range of light intensities. To facilitate the interpretation of our combined measurements across photovoltaic devices and plant species, we developed a new metric termed Photon‑use Equivalent Ratio (PER). The PER conceptually resembles the Land Equivalent Ratio (LER) and expresses the combined photovoltaic-photosynthesis output of leaves underneath semi-transparent solar panels, relative to stand-alone non-transparent solar cells and stand-alone leaves. Notably, our results show that certain device-species combinations achieve synergistic photon use, with PER > 1.

Our experimental approach may guide innovation of semi-transparent photovoltaic devices towards synergy in electricity generation and photosynthesis. In a broader context, our finding that certain device-species combinations achieve synergistic photon use challenges the assumption that solar panels and crops fundamentally compete for light.