3. Result and discussion
3.1 Technical analysis
In order to examine the performance of different PV cell technologies, five PV module types that differing in
efficiency and size are investigated for rooftop mounting. The row spacing between the modules were varied
between 0.5 m and 2.5 m while the tilt angles from the horizontal were varied from 20 to 60 degrees. As shown in
Figure 3, the 0.5 m row spacing, regardless of PV types and the tilt angles, yielded low energy per module area. This
is mainly due to the partial shading caused by the self-shading of PV module row over the other.
The results also indicate that there is no significant energy output variation for a given PV module when the row
spacing increases from 1.5 m to 2.5m, because of a negligible effect caused by the self-shading of the modules. The
results also revealed that the optimal tilt angle lies between 30 and 40 degrees for the year round operation of the PV
systems. Nevertheless, considering snow and dust deposition, the PV module should tend to incline 2-5 degrees
more than the optimum value. Furthermore, the m-si based PV system offered the best energy yield, while the a-si
PV system produce the lowest energy output, which is the direct reflection the higher efficiency of the m-si module.