Increasing solar panel output with blue-green roofs in water-circular and nature inclusive urban development

With an increasing demand for climate resiliency, water sensitivity, nature inclusiveness and energy efficiency in dense urban environments, the call for layered and multifunctional use of rooftops is rising. Vegetated roofs combined with Photo-Voltaic (PV) installations are an example of multifunctional and more effective use of available space, and well-irrigated systems could have an enhanced cooling effect. This research investigated a blue-green capillary irrigated solar roof with grey (shower-) water suppletion, with a constructed wetroof for grey water purification. Two full-scale commercial PV systems on twin rental apartment blocks in Amsterdam were analyzed, on a blue-green roof (BGR) versus a bitumen roof (BiR). The energy output, PV panel temperature, relative humidity and air temperature under the panels were monitored during 5 warmer months (June–October 2022). On average, a solar panel on the BGR is expected to produce 4.4% more energy than a solar panel on the BiR at similar irradiation. A clear difference in panel temperature on the roofs is only seen when the surface temperature of the roofs differs by at least 4.64 °C. Otherwise, other factors such as wind or albedo have probably more influence on the PV panel temperature and thus on PV power output.