“…Secondly, increasing tilt angle means more oblique glass surface area, thus increases the loss of thermal energy from the glass cover. Thirdly, in summer season, when the tilt angle decreases, the incident angle of the sun rays approach to the perpendicular angle to the horizontal plane, especially at the noon, thus the productivity increases [17][18]. But the reduction of tilt angle lower than a specific limit, may be some drops will fall into the basin which leads to productivity reduction.…”