Electrical energy generated by photovoltaic modules mounted inside the roof of a north-south oriented greenhouse

摘要

Four amorphous-silicon photovoltaic (PV) modules were arranged in an arch formation at the northern end of the Gothic-arch style roof of a north-south oriented greenhouse. Two were attached to the inner surface of the east roof with tilt angles of 20p (PV1) and 28p (PV2). The other two were attached to the inner surface of the west roof with tilt angles of 20p (PV3) and 28p (PV4). Each module (832 mm x 412 mm) was lightweight (0.42 kg) and flexible with rated power of 24 W and the efficiency of 7%. The total area of PV1-PV4 was 1.7 m2, which corresponded to 1.5% of the roof area. During seven months, PV1-PV4 generated 71.6 MJ in total. Modules with lower tilt angle generated more energy. West-roof mounted modules generated more energy than was generated by east-roof mounted modules because the greenhouse was oriented 7.03p from true north-south. Yearly generated energy was calculated by assuming cloudless skies. The PV3 unit generated the maximum energy of 119.4 MJ y-1. These results show that the low tilt-angle module generates more electrical energy when it is mounted inside the roof of a north-south oriented greenhouse.