One important key element of solar irradiation is Direct Normal Irradiance (DNI). This indicator of solar irradiation is the direct irradiance received on an area perpendicular to the sun over the total solar spectrum. DNI is calculated over cloudless conditions and it is measured on site by receptors. It is used to calculate the solar power potential of an area. The precise definition that is used to avoid confusion is this: “Direct irradiance is the quotient of the radiant flux on a given plane receiver surface received from a small solid angle centered on the sun’s disk to the area of that surface. If the plane is perpendicular to the axis of the solid angle, direct normal solar irradiance is received.” ISO 9488:1999 (https://www.iso.org/).

It is measured in kilowatt-hours per square meter per day and usually provided as an average per year.

Diffused Horizontal Irradiance (DHI) is the amount of diffused solar radiation that reaches a surface indirectly in the form of scattered molecules and particles measured per unit area. It is basically energy that does not come from the beam of the sun. It also is measured on site by blocking the projected area of the sun from the receptors surface. It can be measured either directly by the appropriate instruments (pyrometers) or indirectly by the relationship between GHI and DHI (see Equation (1)). This is radiation is represented by the horizontal line as shown in the Figure 3.

Global Horizontal Irradiance (GHI) is the total amount of radiation that is received by a surface that is horizontal to the ground. It is the solar energy that enters the earth’s atmosphere before it is diffused by articles in the atmosphere. It is the sum of DNI, ground reflected radiation and the diffused radiation or else named Diffuse Horizontal Irradiance [12] . It is measured through specialized instruments or calculated by the equation:

GHI = DHI + DNI ∗ cos θ z , with θz: solar zenith angle (1)

A solar map is a map containing information on the amount of sunlight received by a solar cell, a field, a piece of land, or other larger area (Figure 4).

Solar radiation is determined by the topography of the area. It may have additional economic data to help make decisions on future development of an area, but the essential elements of a solar map are Topographic, and Climatic data. That means Slope, Aspect, Shadow, and Orientation (relative to the movement of the sun) are all factors of determining the exposure to the sun in each part of a larger area [13] [14] . For the data to be communicated effectively it has to be served in a front end and back end platform [15] . There are two models of deciphering insolation: the point model and the area model [16] . The point model is considered more accurate for specific small areas, while the area model is used for having the possibility to calculate insolation for an area of choice on demand, from the model generated for the large area.

The area is characterized by its year-round temperate climate, with average summer temperatures reaching up to 31˚C (88˚F). According to the Red Sea Project Fact Sheet, this region is envisioned as an exquisite luxury resort destination established across 50 untouched natural islands in a lagoon that stretches along 200 km (125 miles) of stunning coastline [8] .

The area of interest for this research has approximately 85,000 people living on the coasts of the Red Sea. It belongs to the Tabouk Governorate, Saudi Arabia, which has a total population of 455,450 inhabitants (World Population Review).

Environmentally, it is surrounded by desert. Two monsoons define the climate of the Red Sea area. Those monsoons are the result of temperature differences between water surface and land. There are very few rainfalls during the year, averaging 100 mm (4 in) per year appearing locally as short showers [15] . The average air temperature reaches 39˚C (102˚F) (Figure 6). The average surface water temperature is about 28˚C (82˚F) and the average water temperature is 22˚C (72˚F).

The Red Sea project is located on the coast between Umluj city and Al-Wajh city. The altitude of the area is in the range of less than 300 feet as shown in Figure 11. The area is surrounded by the al-Hijaz Mountains. Following maps show the 3D view, altitude, aspect, hillshade, and slope of the study area (Figure 7, Figure 8, Figure 9, Figure 10, Figure 11).

The data used in this study is based on almost four years (Table 1) of solar resource measurements (GHI, DHI and DNI), three main data sources will be used to acquire solar data for the study area from KACARE (King Abdullah City for Atomic and Renewable Energy) metrology network (Figure 13).

・ Umluj solar station (site 1),

・ Al-Wajh solar station (site 2),

・ Duba solar station (site 3).

We also used data derived from satellite provided by NASA via their Power data access viewer portal (https://power.larc.nasa.gov/data-access-viewer/). GHI data are extracted and downloaded from this portal covers from January 2000 to March 2018 with a resolution of 1 degree × 1 degree.

Table 1 shows the data of average monthly Global Horizontal Irradiance, average monthly Direct Normal Irradiance and average monthly Global Horizontal Irradiance collected for the period 2013-2017 gathered by the three stations (Umluj, Al-Wajh and Duba).

As shown in Figure 14, GHI average corresponds to the below trend equation

y = 4.1308 x + 5896.8 (2)

this equation shows that is a very slight increment along the time period of the data.

As shown in Figure 15, DNI mobile average corresponds to the below slope equation:

y = − 7.8179 x + 6444.6 (3)

this equation shows that is a slight decrement along the time period of the data.

As shown in Figure 16, DHI average corresponds to the below trend equation

y = 6.1121 x + 1732.8 (4)

this equation shows that is a steady increment along the time period of the data.

As shown in Figure 17, GHI average corresponds to the trend equation

y = 4.7295 x + 5919.3 (5)

that is a very slight increment along the time period of the data. It also closely corresponds to the same GHI average from station 1.

As shown in Figure 18, DNI average corresponds to the trend equation

y = − 8.5064 x + 6857.3 (6)

that is a slight decrement along the time period of the data. It also closely corresponds to the same DNI average from station 1.

Interpretation: as shown in Figure 19, DHI average corresponds to the trend equation

y = 5.2022 x + 1605.7 (7)

that is a steady increment along the time period of the data. It also closely corresponds to the same DHI average from station #1.

As shown in Figure 20, GHI average corresponds to the trend equation

y = − 0.7648 x + 6057.7 (8)

that remains steady along the time period of the data.

As shown in Figure 21, DNI average corresponds to the trend equation

y = − 11.889 x + 7230.2 (9)

that is a steady decrement along the time period of the data.

As shown in Figure 22, DHI average corresponds to the trend equation

y = 4.8305 x + 1478.7 (10)

that is a slight increment along the time period of the data.

According to the measurements gathered from the three ground stations et and according to graphs (from Figure 14 to Figure 22), the highest monthly average of GHI and DNI are observed in July with almost 8 KwH/m².

With regard to the trends of the different measures, it can be said that it is difficult to pronounce on the trend of the evolution of the different measured parameters since the period of measurements is rather short.

For this reason, we used NASA-provided satellite data covering a period of about 17 years. These data relate to GHI measures. We have indeed used these data to compare them with the data collected by ground measurement stations and to reveal the trend of GHI.

The figure below (Figure 23), shows GHI measured by Al-Wajh ground station and measures derived from satellites. The measurements are in good agreement, however we calculated the rBias between the two sets of measurements, and we can observe that the rBias between data has an average of 3% with a maximum of 18% (see Figure 24).

Rhe trend of GHI measurements has been made on satellite-collected measurements because they cover a period of about 17 years. Contrary to the figures on which there is a slight increase in the GHI values for the two stations of Umluj and Al-Wajh (Figure 14 and Figure 17), the general trend is rather downward as shown in Figure (Figure 25).

Tables 2-4 summarize the data limits and averages from data sources by measurement stations.

The yield in the study area for DNI & GHI considerably, as designated in Table 5, ranges from 6000 to 7000 Wh/m². It indicates to be significant amount. This affirms to the results from the previous study mentioned in this research [17] .

Table 5 shows the total average of all indices of total records. Reference to Equation (1), Azimuth angle can be calculated as shown in the table.