Meteorological inputs were obtained from the Meteonorm database embedded within PVsyst, which provides long-term hourly averages of Global Horizontal Irradiance (GHI), Diffuse Horizontal Irradiance (DHI), ambient temperature, wind speed, and relative humidity. These parameters are essential for accurately modeling PV performance, particularly in humid coastal climates where atmospheric moisture and cloud cover significantly influence beam radiation. According to Table 1 of the thesis, the Abbasabad site exhibits substantial seasonal variability, with higher humidity and cloudiness during spring and autumn, and relatively clearer skies during summer. These variations directly affect the incident irradiance and module operating temperature.

The PV system consists of three polycrystalline silicon modules rated at 270 W each, yielding a total installed capacity of 810 W. The electrical characteristics of the modules, extracted from Table 2, include:

I. Short-circuit current: 9.06 A II. Open-circuit voltage: 37.2 V III. Maximum power point voltage: 31.2 V IV. Maximum power point current: 8.25 A V. Module efficiency: 18.28% The inverter used in the system is an IMC grid-connected model with a nominal AC power of 1.8 kW, a maximum DC voltage of 500 V, and a conversion efficiency of 97.2% (Table 3). The system also includes a 25 A charge controller and two 150 Ah batteries, although the primary analysis focuses on grid-connected operation.

The PVsyst software was employed to simulate system performance under real climatic conditions. The modeling procedure included:

I. Importing Meteonorm climate data for Abbasabad II. Defining module and inverter specifications III. Configuring system topology (series/parallel arrangement) IV. Setting module tilt equal to the site’s latitude, as recommended for fixed-tilt systems V. Incorporating the horizon profile, Fig. 1, to account for shading from surrounding terrain and vegetation. VI. Running annual simulations to compute energy yield, system losses, and PR The software calculates array losses (thermal, ohmic, mismatch, and irradiance-related) and system losses (inverter losses, wiring losses, and AC losses). These outputs form the basis for evaluating system efficiency and identifying performance-limiting factors.

The primary performance indicators used in this study include:

I. Energy yield (kWh/kWp/day): Total useful energy delivered to the grid per unit of installed capacity. II. PR: A dimensionless metric representing the ratio of actual system output to the theoretical output under standard test conditions [9], [12].

III. Array and system losses: Quantification of energy losses due to temperature, shading, inverter inefficiency, and wiring.

According to the simulation results, the system exhibits array losses of 0.81 kWh/kWp/day and inverter losses of 0.17 kWh/kWp/day, resulting in a net useful output of 4.67 kWh/kWp/day and an annual PR of approximately 0.827.

The experimental site is located in Abbasabad, situated in the western part of Mazandaran Province, Iran. The region features a humid subtropical climate, dense vegetation, high annual precipitation, and significant seasonal variability in cloud cover. These environmental conditions influence the availability of direct beam radiation and contribute to fluctuations in PV module temperature and shading patterns. Meteorological data extracted from Meteonorm Table 1 indicate:

I. High humidity levels throughout the year II. Moderate wind speeds, particularly during spring and autumn III. Seasonal dust and pollen transport due to the surrounding forests IV. Variable solar irradiance, with peak values occurring in summer months These climatic factors make Abbasabad an ideal case study for evaluating PV performance in humid coastal environments.

The PV modules were installed with a fixed tilt angle equal to the site’s latitude, following standard recommendations for maximizing annual energy yield in fixed-tilt systems. According to Fig. 2 in the thesis, the optimal tilt angle ensures that the modules receive maximum annual irradiance while minimizing seasonal shading effects. The azimuth angle was set to true south (0° deviation), which is the optimal orientation for PV installations in the Northern Hemisphere.

A detailed solar path analysis was conducted using PVsyst’s sun-path diagram (Fig. 2). The analysis revealed:

I. High solar altitude during the summer months results in increased irradiance II. Lower solar elevation in winter, but with reduced module temperature and improved voltage output III. Potential partial shading during early morning and late afternoon due to surrounding vegetation

This analysis was essential for determining the effective irradiance at the module surface and quantifying shading-related losses.

The system consists of three polycrystalline silicon modules rated at 270 W each. The electrical characteristics (Table 2) include:

I. Pmax: 270 W II. Voc: 37.2 V III. Isc: 9.06 A IV. Vmp: 31.2 V V. Imp: 8.25 A VI. Module efficiency: 18.28% The inverter used is an IMC grid-connected model with specifications (Table 3):

I. Nominal AC power: 1.8 kW II. Maximum DC voltage: 500 V III. Maximum module voltage: 200 V IV. AC output voltage: 200 V V. Frequency: 50 Hz VI. Inverter efficiency: 97.2% These specifications were directly imported into PVsyst to ensure accurate simulation of electrical behavior.

The horizon profile for the site Fig. 4 was incorporated into PVsyst to account for shading from nearby trees, buildings, and terrain. The horizon line shows:

I. Moderate shading during early morning hours II. Minimal shading during midday III. Increased shading during late afternoon due to forest density This step is critical because shading significantly reduces the effective irradiance and can cause mismatch losses within the PV array.

The simulation process consisted of the following steps:

I. Importing Meteonorm climate data for Abbasabad II. Defining module and inverter parameters III. Configuring the system layout (series/parallel arrangement) IV. Setting tilt and azimuth angles V. Importing the horizon profile VI. Running annual simulations to compute:

− Global incident energy − Effective irradiance on the array − Array losses (thermal, ohmic, mismatch, irradiance) − System losses (inverter, wiring, AC losses) − Monthly and annual energy yield − PR

The simulation results indicated:

I. Array losses: 0.81 kWh/kWp/day II. Inverter losses: 0.17 kWh/kWp/day III. Useful AC energy delivered: 4.67 kWh/kWp/day IV. Annual PR: ~0.827 These values demonstrate that despite the humid climate and shading effects, the system maintains acceptable performance.

According to the PVsyst simulation results Table 4, the system delivers an average of 4.67 kWh/kWp/day of useful AC energy to the grid. Monthly variations in energy production closely follow the seasonal distribution of solar irradiance:

I. The highest production occurs during June–August, when solar altitude is higher, and cloud cover is lower. II. Lowest production is observed in December–January, primarily due to shorter daylight hours and increased atmospheric moisture.

Fig. 2 of the thesis illustrates the monthly dispersion of energy yield, showing a clear correlation between irradiance availability and system output. Despite the humid climate, the system maintains stable performance year-round, demonstrating the suitability of polycrystalline modules for coastal environments.

The annual PR of the system is approximately 0.827, which is consistent with PR values reported for similar climates in Southeast Asia and coastal Turkey (typically 0.78–0.85). The relatively high PR indicates:

I. Effective system design II. Low mismatch and wiring losses III. High inverter efficiency (97.2%) IV. Moderate thermal losses due to the region’s mild temperatures Fig. 3 of the thesis shows monthly PR values, with the highest PR occurring in winter months. This trend aligns with global findings that lower module temperatures improve voltage output and reduce thermal derating.

The PVsyst loss diagram (Fig. 4) provides a detailed breakdown of energy losses from incident irradiance to

Key findings include:

The climatic characteristics of Abbasabad significantly influence system performance:

I. Humidity and cloud cover: High humidity reduces beam radiation and increases diffuse irradiance, lowering the effective irradiance on the module surface. This effect is most pronounced in spring and autumn [13], [14].

II. Temperature: Moderate winter temperatures improve module efficiency, resulting in higher PR values despite lower irradiance.

III. Wind speed: Seasonal winds help cool the modules, reducing thermal losses during warm months.

IV. Dust and biological particles: Pollen and forest-generated particulates can reduce the module surface's transmittance, though the impact is less severe than in arid regions.

These findings align with global studies showing that humid coastal climates exhibit lower irradiance but benefit from reduced thermal losses.

When compared with similar PV installations worldwide:

I. The annual PR of 0.827 is higher than typical values reported for tropical humid regions (0.75–0.80). II. The energy yield of 4.67 kWh/kWp/day is comparable to coastal installations in Turkey and Brazil.

III. Loss patterns closely resemble those reported in studies from Malaysia and Thailand, where diffuse radiation dominates.