1. Introduction
The world’s growing population and economy are driving a surge in energy demand [
1]. This necessitates innovative solutions to ensure future energy sustainability. As concerns about finite conventional energy sources grow, renewable energy is gaining attention [
2]. Solar energy is a sought-after form of renewable energy due to its reliability, environmental benefits, and security. The global photovoltaic capacity has expanded dramatically from 1288 MW in 2000 to 1,177,000 MW in 2022, solidifying solar energy’s position as a leading force in the green energy revolution [
3].
Solar modules effectively harness the consistent radiation from the sun, making solar energy a promising option for a sustainable future [
4]. The modules employ solar cells to convert sunlight into electrical energy, leveraging the photovoltaic effect to generate power. This process involves the absorption of solar radiation by the solar cells, which then excites electrons to produce a direct current (DC) electrical output [
5]. The amount of energy that the PV module can generate primarily depends on the connected load. Without a load, the module’s internal resistance increases, resulting in negligible current flow. When connected to a load, the internal resistance decreases, enabling current flow and power generation. Although photo-generated current is directly proportional to solar irradiance, the PV current curve does not always match the irradiance curve due to the influence of the connected load. The load determines the amount of current released by the PV module [
6]. Solar photovoltaic (PV) modules are designed to operate optimally under standard test conditions (STC): 25 °C temperature, 1000 W/m
2 solar irradiance, and 1.5 air mass [
7].
The performance of PV modules in actual outdoor environments frequently differs from that observed in controlled laboratory settings. This discrepancy arises because outdoor conditions involve a dynamic combination of factors—including solar radiation, temperature, humidity, wind, and operating voltage—that cannot be precisely duplicated in the predetermined sequences used during certification or qualification testing [
8,
9]. Evaluating PV system performance in real-world outdoor environments is essential to optimize power efficiency, maintain grid stability, and ensure power system safety [
10]. Moreover, accurately predicting PV power generation is critical, particularly under adverse weather conditions, to guaranteeing the stability and reliability of the power system [
11].
The International Energy Agency (IEA) Photovoltaic Power Systems Programme Task 2 has established parameters for evaluating PV performance, as defined by the International Electrotechnical Commission (IEC) 61724 [
12]. These parameters include array final, reference yield, final yield, array capture losses, system losses, inverter efficiency, system efficiency, module efficiency, performance ratio (PR), and capacity utilization factor (CUF) [
13]. PR is the most widely used parameter, as it represents the cumulative impact of various factors on rated output, including inverter inefficiency, cell temperature, and module performance [
14,
15].
Several researchers have used the IEC 61724 parameters to evaluate the efficiency of solar PV systems. For instance, Malvoni et al. [
16] examined the performance and degradation of a 1 MW PV system in a tropical semi-arid climate in India using four years’ worth of monitored data. Their study found a reference yield of 4.64 h/day, a final yield of 6.23 h/day, a system efficiency of 11%, a CUF of 19.33%, and a PR of 74.73%. Similarly, the effect of solar irradiance, wind speed, and module temperature on the performance of PV systems in a hot and humid tropical environment in Ghana was examined by Abdul-Ganiyu et al. [
17]. The results revealed an annual total output energy of 194.79 kWh/m
2 for the PV module, a PR of 79.2%, and a CUF of 13.4%. A comprehensive study by Kumar, Chandel, and Kumar [
18] investigated the performance of a 10 kWp solar PV array in the diverse climates of five Andaman and Nicobar Islands. The research assessed the array’s behavior based on available solar resources. The findings revealed a yearly average CUF ranging from 13.73% to 14.61% and a PR ranging from 64.70% to 64.93%.
Due to the lack of research on large-scale PV systems in Algeria, Dahbi, Aoun, and Sellam [
19] examined the performance of a 6 MW grid-connected PV plant in southern Algeria. Their study found an annual average PR of 74.68%, a system efficiency of 11.39%, and a CUF of 21.44%. It also revealed a correlation between increasing ambient temperature or solar irradiation and a decrease in the performance ratio.
The outdoor performance of the 7.8 kWp grid-connected rooftop PV system for residential areas under the feed-in-tariff scheme was investigated by Anang et al. [
20] between 2018 and 2019. Their findings demonstrated that the PV system efficiently met household electricity demands, with a satisfactory PR and annual CUF ranging from 13% to 16%. A performance analysis of a 19.2 kWp grid-connected photovoltaic power system was presented by Santos et al. [
21]. The system was monitored from March to September 2021, delivering 18,197.15 kWh to the power grid. The average reference, array, and final yields were 5.45 kWh/kWp, 4.33 kWh/kW, and 4.26 kWh/kW, respectively. The PR and CUF were 81.85% and 18.05%, respectively, highlighting the good performance of PV systems in Northeast Brazil.
Due to the lack of knowledge regarding the performance and reliability of off-grid PV systems, Wassie and Ahlgren [
22] evaluated a 375 kW off-grid PV mini-grid system installed in a remote town in Ethiopia using real-time monitored data. This study revealed a significant discrepancy between actual and estimated electricity generation, with the mini-grid producing 1182 kWh/day, 46.6% less than the estimated 2214 kWh/day. This shortfall was due to capture and system losses. The key performance metrics were as follows: module efficiency 9.85%, PR 42%, CUF 13%, and overall system efficiency 8.76%. However, the system struggled to meet the town’s daily energy demands, resulting in occasional power shedding due to insufficient PV energy output. A similar study was conducted by Supapo, Lozano, and Querikiol [
23] on a rooftop solar PV system on an off-grid island in the Philippines. Utilizing PVSyst and HOMER Pro software, the researchers assessed the system’s performance and economic viability. Simulation results showed an annual mean PR of 57.10% and a CUF of 18.96%, demonstrating the system’s capacity to meet the entire electrical load demand of the island’s residents. This study highlights the reliability and effectiveness of solar PV systems in providing sustainable energy solutions.
Further emphasizing the potential of rooftop PV systems, Gulkowski and Krawczak [
24] examined the annual energy output of a 9.6 kW rooftop PV system in Poland over three years. Their findings revealed an annual energy production exceeding 1000 kWh/kW, attributed to favorable conditions such as low temperatures, abundant sunlight, and summer rainfall, which kept the PV modules clean. Notably, the system achieved an average PR of 85% during the analyzed period, highlighting its high efficiency and reliability. These studies demonstrate the importance of assessing PV system performance under diverse environmental conditions using the IEC 61724 standard, which is based on grid-connected PV systems with relatively consistent load (baseload) and high energy consumption. The standard gives limited attention to off-grid PV systems with inconsistent and lower energy consumption. This results in a lack of knowledge about the performance, reliability, and efficiency of off-grid PV systems. Addressing this gap is crucial to optimize and advance off-grid PV systems.
To address this gap, this study investigates the impact of ambient weather conditions and energy usage patterns on the performance of an off-grid building-integrated photovoltaic (BIPV) system. BIPV systems integrate solar power into building design, replacing traditional elements and utilizing the building envelope, eliminating dedicated PV plant space [
25]. A two-month on-site data collection campaign was conducted, gathering comprehensive meteorological and electrical data to evaluate the system’s performance. The primary contribution of this study is to emphasize the need for specialized performance evaluation parameters for off-grid PV systems, as they are not effectively covered in the current IEC 61724 standard.
This paper is organized into five sections:
Section 2 provides a detailed description of the site and PV system under investigation.
Section 3 outlines the materials and methods employed in the study. The results and a discussion of the results are then presented in
Section 4, where the findings are analyzed and interpreted. Finally,
Section 5 concludes the paper by summarizing the key findings, highlighting the main implications, and providing recommendations for future research directions.