Impact of Crops on the Microclimate and PV System Performance

Faced by land constraints, Singapore needs to look for viable options to bolster renewable energy consumption whilst trying to prop up local food production. Agrivoltaics is seen as a feasible method where hydroponic farming is integrated underneath solar photovoltaics (PV) systems on a common land. This study aims to investigate the impact crops have on the microclimate and whether it contributes to enhanced PV performance. Situated in the SIT@Dover campus in Singapore, the agrivoltaics setup consists of two identical plots, Plot A and Plot B. Each plot consists of twenty solar panels, erected at a height of 2.5m. Beneath the panels contain two hydroponics growth tables, each capable of housing 180 pots of crops. A HOBO External Temperature/RH Sensor Data Loggers were installed 30 cm above each of the growth tables to record data at 5 min logging intervals. A HOBO U30 USB Weather Station Data Logger records meteorological data at intervals of 5 min. Plot A (control) was intentionally left without crops while Plot B was sowed with 90 Brassica oleracea var. sabellica pots (50% capacity). The Brassica oleracea var. sabellica was left to grow in the hydroponics system and harvested on the 32nd day of the crop cycle. Microclimate and energy yield data from the 31st day of the crop cycle were analysed. The 12-h mean temperature from 0700hrs to 1900hrs revealed that the Brassica oleracea var. sabellica on Plot B reduced the temperature above it by 0.97°C as compared to Plot A. The 12-h mean relative humidity tabulated for Plot A and B was 67.45% and 72.30% respectively. During overhead conditions from 1100 hrs to 1300 hrs, Plot B saw the microclimate temperature lowered by 1.33°C as compared to Plot A while the relative humidity elevated by 6.81% as compared to Plot A. The increase in relative humidity is attributed to the transpiration experienced by the Brassica oleracea var. sabellica during photosynthesis which shows that plants have the potential to induce cooler microclimatic conditions. The solar PV on Plot B generated 4.36% lesser energy yield as compared to Plot A. The difference is attributed to uneven irradiance captured by the plots due to building shading caused by the morning sun. Cooler microclimate temperature on Plot B does not contribute to improved PV performance primarily due to the large gap between the growth tables and the underside of the solar panels which encourages sufficient convection to take place.