Abstract
Solar photovoltaic (PV) systems are one of the best options to solve the electricity shortage in Iraq because the country has high solar radiation almost all the year. In this paper, many different rooftop PV systems were designed for a college building in Baghdad and tested by using SketchUp and PVsyst programs. The SketchUp software was used to make a 3D model of the building and to study the shading effect from nearby objects, while PVsyst was used to simulate the system performance and electrical output. The work included two types of solar panels (Monocrystalline and HJT), with both fixed and seasonal tilt angles, and two installation directions (portrait and landscape). The effect of the distance between the rows of panels was also studied. To make the results more close to the real case, losses like dust, aging of the panels, and system shutdown time were added in the simulation. The results showed that HJT panels gave higher energy production and better performance ratio compared with the monocrystalline ones. Also, using seasonal tilt increased the yearly energy by around 5%. Increasing the distance between panel rows helped to reduce shading and improve system efficiency, but it also reduced the total number of panels on the roof. In general, this work proved that the correct design of tilt angle, orientation, and spacing can improve the technical performance of rooftop PV systems under Baghdad climate, and using 3D modeling helps to get more realistic results.

Key words: PV system, PVsyst, SketchUp, shading, HJT modules, performance ratio.