Greenhouse performance results for roof installed photovoltaics

The installation of PV panels on the greenhouse's roof reduces solar radiation that passes through roof glazing and falls to the plants inside the greenhouse, affecting their lighting and therefore crop growing. In this paper, performance results of energy production and plant growing from installed PV panels on greenhouse roof, are presented. The results are obtained from a cultivation period of lettuce crop inside two greenhouses, one with fixed roof installed photovoltaics and another unit without photovoltaics. Regarding electrical output, PV panels produced 50.83 kWhm−2 for the characteristic cultivation period of Feb-Mar-Apr, creating also a 20% greenhouse shading. Plant growing results under shading effect were satisfactory, as they were at same level with those of reference greenhouse without PV covered roof. Extending the results for three PV installation modes to 1 ha greenhouse, theoretical results were calculated. The considered PV installation modes are the fixed one, with panels placed on south facing greenhouse roof and two sun tracking modes, with PV panels in rows and axis on east-west and north-south direction. The calculations showed that sun tracking PV panels produce more electricity than fixed mode and can result to solar control of the interior space of the greenhouse.