Floating Solar Panels Raised Pond Greenhouse Gas Emissions 26.8% in Cornell Study

A field experiment at Cornell's Experimental Pond Facility in New York covered 70% of three ponds with floating solar panels. Daily greenhouse gas emissions rose 26.8% in carbon dioxide equivalent, driven by a 57.2% increase in bubbling methane from sediment. The panels reduced diffusive CO2 and methane by slowing gas exchange with the air, but that reduction was fully offset by the methane bubbles. The study, published in Environmental Science & Technology Letters, estimates the water-use emissions at 2.61 g CO2e per kilowatt-hour, adding 4.0% to 6.5% to life-cycle estimates of floating solar. The authors note that 70% coverage is at the high end of existing installations, so the values may be on the upper end. A separate study on a German lake found a 73% reduction in surface sunlight and 23% reduction in near-surface wind under a floating array. Both studies suggest that coverage limits, panel height and angle, and aeration equipment can reduce impacts on water bodies. For anyone evaluating floating solar siting, these findings show that surface cover changes water physics and greenhouse gas dynamics, so site-specific assessment matters.