1. Introduction
In the last few decades, there has been a trend toward using clean energy sources in the world. Those intermittent energy sources are environmentally friendly and economical throughout the years. Developing countries, in particular, are inclined to utilize such resources to meet their energy demand. KSA is one of the highest energy-producing countries in the Middle East, with approximately 63 GW, most of which depends on oil [
1,
2,
3,
4]. This fact is considered a serious challenge for the electricity sector in the kingdom. Consequently, officials and specialists are keen to look for alternatives to address this problem adequately. Therefore, the National Renewable Energy Program in Saudi Arabia has been established to develop and maximize the utilization of renewable energy resources and to become one of the main sources rather than depending entirely on oil.
Solar energy resources are considered the breakthrough that can highly overcome such power generation problems in most Middle East countries. Therefore, KSA is going toward increasing the use of solar energy to reduce the dependence on oil in producing energy. The average radiation in KSA ranges between 5 and 7 kWh/m
2 [
1,
2,
4,
5,
6,
7,
8]. This amount of solar radiation is relatively high compared to the neighboring countries [
1,
9,
10,
11]. To make the use of this free and clean energy possible, the KSA government issued legislation and laws that facilitate and assist the new installations and designs of solar energy systems on the roofs of residential and commercial buildings.
Designing a PV system requires knowledge about the solar radiation theory and its calculation. The determination of the peak sun hours, which refer to the amount of energy received by the panels or, in other words, how much energy is received during the day in a specific area, is one of the most important pieces of information needed to design a PV system [
3,
4]. Peak power or the kilowatt peak (kWp) of the power demand has to be calculated before determining the number of panels that have to be accommodated with the roof capacity [
12].
Several research studies in the literature discussed the general assessment of solar radiation resources in Saudi Arabia and the vision of the kingdom for the upcoming decade. Network design, implementation, and data quality assurance are described in [
1]. In addition, the authors analyze the first year of broadband solar resource measurements from a new monitoring network in Saudi Arabia developed by the King Abdullah City for Atomic and Renewable Energy (K.A.CARE). The analysis used 12 months (October 2013–September 2014) of data from 30 stations distributed across the country based on one-minute measurements of global horizontal irradiance (GHI), diffuse horizontal irradiance (DHI), direct normal irradiance (DNI), and related meteorological parameters. In [
4], the authors provide a maiden attempt to investigate how much sustainability substance is in the 2030 Vision of Saudi Arabia. The Sustainable Society Index (SSI) has been employed to examine the 2030 Vision and understand the Kingdom’s commitment to building resilient, inclusive, and sustainable societies. The Vision and National Transformation Program (NTP) texts were matched against five broad measures and 22 submeasures. Both the 2030 Vision and the NTP align with the SSI measures in some respect. The goals and objectives reflect the aspirations and context of Saudi Arabia. The carbon emission is expected to be zero in 2060 in KSA, so it is expected to be reduced by 60% in 2030 [
5]. Several projects are carried out throughout the country, and different studies are presented to introduce the system regulations and policies. According to [
6,
7,
8,
9,
10], certain policies that promote the renewable energy sector and regulate the relations with electricity and grid connection sectors are subsidized in KSA. The net metering and feed-in tariff policies are employed to exchange the surplus energy with the electricity network in KSA.
For rooftop PV systems, net-metering was tested in 2017 and found to be the most suitable policy for small-scale PV systems. The applicability of using feed-in tariff (FiT) policy in KSA is reviewed in [
11], in comparison with that implemented in USA and Germany. It is concluded that KSA has the ability to adopt and use this technique.
Specific case studies in KSA have also been discussed in the literature to achieve the vision of the kingdom in the sector of solar energy. The authors in [
12] examine the best tilt angle for a solar panel to maximize the collected amount of solar irradiation. A daily global and diffuse solar radiation measured on a horizontal surface is considered in this research. The optimal angle for each month allows capturing the most solar energy for the Madinah site, KSA. The authors concluded that the annual optimal tilt angle is almost equal to the location’s latitude. In [
13], a comprehensive analysis is presented in order to improve the solar energy performance of residential buildings in KSA by optimizing the building envelope elements. The elements included in energy cost and energy energy-saving analysis include the wall insulation, roof insulation, window area, window glazing, window shading, and thermal mass.
Figure 1 illustrates the anticipated progress towards increasing the energy produced by renewable energy resources. Overall, the targeted capacity by 2030 would cover 58.7 GW as stated by the kingdom vision [
1,
2,
3]. The plan set an initial step of producing 9.5 GW of electrical energy, followed by producing 27 GW in the next five years. By maintaining efforts, the plan is expected to be realized, as previously presented, utilizing solar, wind, and CSP energy.
When installing the PV system over buildings’ roofs, one of the significant factors that should be considered is the sun path. The more solar panels exposed to the direct sun, the more energy is harvested. Each location in the world has a specific sun path and unique tilt, azimuth, and elevation angles [
12].
Figure 2 represents the most significant angles that play an important role in PV system design.
The desired tilt angle varies according to the case study under test. The designers should ensure that the solar panels face the sunlight perpendicularly, as much as possible, since the solar panels produce the highest power when they face the sun directly. During the winter semester, the solar panels face the sun at a sharp angle. Therefore, the energy produced by the PV system is low compared to the energy produced during the summer semester. In the winter semester case, the operator should ensure harvesting large amounts of solar energy by choosing proper orientation angles. The optimum tilt angle in KSA is approximately equal to the site’s latitude under test [
13,
14]. In addition, the elevation angle significantly affects the proper method of installing the panels with the most suitable spacing between rows. This must be determined to avoid the possibility of energy reduction that panels cause for each other.
Figure 3 illustrates the relationship between elevation angle and spacing between rows in the PV system.
Several studies consider the performance of rooftop solar panels by assessing different design and simulation methodologies. The effect of rooftop obstacles and shadow can be determined using photovoltaic software to identify the azimuth and tilt angles [
15]. One study assesses the impact of a building’s shading and analyzes the available rooftop area using hillshade analysis [
16]. The study estimates the potential of a rooftop system when shaded area is excluded. PV systems in rooftops and facades and a shadow algorithm are developed in [
17]. It is concluded that although facades receive lower solar radiation, they have a substantial impact on potential urban PV systems once they are utilized. Mangiante et al. in [
18] carried out a comparison between rooftop solar arrays in terms of neighborhood orientation and tree shadows. These obstacles affect the solar energy potential. The height and age of the trees are found to have an effect as well.
Other research studies are conducted to investigate the available areas on the surface of the urban cities [
19,
20,
21,
22,
23]. In [
19], a review systematically presents the studies that consider estimating the rooftop area of the cities and the potential deployment of rooftop PV systems. A technical and geographical assessment of the rooftop area in urban cities using novel methodology is presented in [
20]. A hierarchical methodology is employed for the estimation process, which encompasses three phases of estimation: physical, geographical, and technical potentials. Geometry calculations and irradiation analysis for tilted rooftop surfaces are performed in [
21], including the use of image processing for shadow estimation algorithms in different sun positions. It has been found that in large urban cities, the appropriate analysis method needs three-dimensional data of the studied location.
Many articles focus on solar capacity assessment in rooftop systems in terms of sizing, installation angles, and the efficiency of photovoltaic systems [
24,
25,
26,
27,
28]. The complete design of a grid-connected PV system is presented in [
24,
28]. Performance investigation and rooftop analysis are carried out in [
26,
27,
28,
29,
30,
31,
32]. In [
26], a financial and technical feasibility study is performed, which is applicable for only certain geographical locations and weather conditions. For evaluating system performance, the authors in [
25] provide a photovoltaic plant design that operates with a seasonal tilt angle according to plant location. The tilt angle is set to be the same as the corresponding latitudinal value of the location to obtain the highest solar radiation. In [
29], the rooftop area is assessed using the optimal tilt angle, and 60% of the area is found to be suitable for photovoltaic system implementation.
The research study in this paper aims to fill the gap by providing a comprehensive solar analysis to investigate the feasibility of establishing an on-grid PV system of 330 KW in KSA, exactly in Jeddah city, and introduce the proper building approach. The project is designed to feed the needs of the Ministry of Electricity building, which is a governmental complex with high energy-consuming appliances. The design aims to find the proper way to distribute the solar panels on the roof of the Ministry buildings. This task has been achieved by manipulating the tilt angle until obtaining the desired angle which enables the working staff to accommodate the available area with targeted production, considering that the shading must be avoided and reduced as much as possible.
The rest of the paper is organized as follows:
Section 2 describes the design methodology of the PV system under test; two different scenarios are suggested in this section. The energy production for both scenarios is presented and compared. Panel orientation is discussed in
Section 3, in which different orientation angles are defined and presented. The single-line diagram of the entire system is also presented in this section. PVsol simulator is used to estimate the performance ratio of this study. The size of the PV system for the second scenario is introduced in
Section 4. Finally, the number of needed PV panels and inverters and the appropriate approach of connections are discussed in this section, prior to the conclusion in
Section 5.
3. System Configuration
The connection diagram between the panels and the inverters is shown in
Figure 8. The panels are connected in four main groups: 2 × 17, 6 × 17, 2 × 15, and 7 × 17. Each group has a specific number of strings, in which panels are connected in series.
Table 2 gives details about the selected tilt and elevation angles, the distances between the PV panels, and the total roof areas for all scenarios.
Table 3 shows solar irradiance in kWh/m
2 at different inclination angles.
In this section, the size of the PV system for the second scenario, which has been selected, is introduced. The number of needed PV panels and inverters and the appropriate approach of connections are discussed.
The required PV panels that met a demand of 300 kW are decided to be 790 modules of 380 W each. In addition, six inverters are needed to integrate the PV system with the grid [
30,
31]. The method of connecting the PV models with the inverters in the form of strings is shown in
Figure 9. More details about the required system parameters and quantities are also shown in
Table 4.
The single-line diagram (SLD), shown in
Figure 10, was drawn and sized according to the Ministry of Electricity standards of grid integration for the distribution system of low and medium voltages. Moving in detail to the SLD, the number of the connected solar panels is 790 panels distributed in an area of 2118 m
2. In addition, there are six inverters with a capacity of 50 kW each. The appropriate connection between these panels and inverters is to establish three groups of series panels, 15, 16, and 17, each group connected with one of the inverters’ MPPTs. This distribution is determined by the inverters’ voltage limits, which keep the voltage up to 950 volts.
Moreover, the SLD represents the sizing of cables and their cross-sectional areas (CSAs) that connect the panels with the inverters. PV cables and AC cables that connect inverters with the grid are also presented in this diagram. Their cross-sectional areas are 6 mm2 and 35 mm2, respectively. From the main bus bar to the grid, cables of 185 mm2 are used. A molded case circuit breaker (MCCB), with 122 A capacity, is connected between every inverter and the main bus bar. The main circuit breaker, which is established between the main bus bar and the low voltage grid, has a capacity of 500 A.