Clearness-Index-Driven Assessment of Solar Energy Potential in Saudi Arabia's Empty Quarter: A Comparative Study with Abqaiq and Hail (2005–2024)

Clearness -Index-Driven A ssessment of Solar Energ y Potential in Saudi Arabia’s Empty Quarter : A Comparative Study with Abqaiq and Hail (󾙔󾙒󾙒󾙗‒󾙔󾙒󾙔󾙖) Author: Mohammed Almarri Affiliation: King Fahd University of Petroleum and Minerals Program: M.Sc. in Sustainability & Renewable Energ y Year: 󾙔󾙒󾙔󾙗 Abstract Saudi Arabia possesses some of the world’s highest-quality solar resources, particularly across its hyper-arid deserts. This study performs a 󾙔󾙒-year clearness - index-based assessment (󾙔󾙒󾙒󾙗‒󾙔󾙒󾙔󾙖) of solar energy potential in the Empty Quarter, using Sharurah (󾙓󾙙.󾙖󾙚°N, 󾙖󾙙.󾙓󾙔°E) as a representative southern site. Two additional locations—Abqaiq in the eastern oil region and Hail in the inland north—are used for climatic comparison. Using NASA POWER climatolog y, we derive monthly and annual global horizontal irradiation (H), compute extraterrestrial irradiation (H₀) from solar geometr y, and obtain the clearness index K_t = H/H₀. Sharurah (Empty Quarter) exhibits an annual H ≈ 󾙔󾙖󾙕󾙚 kWh/m²·yr and K_t ≈ 󾙒.󾙘󾙛󾙛, indicating extremely clear, beam-dominated desert skies. Hail also shows excellent resource with H ≈ 󾙔󾙔󾙘󾙔 kWh/m²·yr and K_t ≈ 󾙒.󾙘󾙛󾙔, while Abqaiq, affected by industrial/urban aerosols, has H ≈ 󾙔󾙓󾙛󾙖 kWh/m²·yr and K_t ≈ 󾙒.󾙘󾙘󾙓. A ssuming fixedtilt PV with tilt ≈ latitude, plane-of-array gain = 󾙓.󾙓󾙗, and performance ratio PR = 󾙒.󾙚󾙒, the Sharurah/Empty Quarter site delivers a specific PV yield of approximately 󾙔󾙔󾙖󾙕 kWh/kWp·yr, compared to ~󾙔󾙒󾙚󾙓 kWh/kWp·yr for Hail and ~󾙔󾙒󾙓󾙚 kWh/kWp·yr for Abqaiq. A land-use scenario in which 󾙗% of the Saudi portion of the Empty Quarter (~󾙔󾙓,󾙗󾙒󾙒 km²) is covered with PV at an installed density of 󾙘󾙒 MWp/km² yields an annual electricity generation of ≈ 󾙔󾙚󾙛󾙖 TWh/yr, equivalent to around 󾙚.󾙚‒󾙛.󾙘 times the current national electricity consumption (󾙕󾙒󾙔‒󾙕󾙔󾙙 TWh/yr). This corresponds to a continuous average power of ≈ 󾙕󾙕󾙒 GW, compared to a national average load of 󾙕󾙗‒󾙕󾙙 GW and peak summer load of 󾙛󾙒‒󾙛󾙗 GW. Using a CAPEX of 󾙕,󾙒󾙒󾙒 SAR/kWp and an internal electricity value of 󾙒.󾙔󾙔󾙗‒󾙒.󾙕󾙒󾙒 SAR/kWh, the simple payback period is ≈ 󾙖.󾙗‒󾙗.󾙛 years, while carbon payback occurs in less than one year. The analysis confirms the Empty Quarter, represented by Sharurah, as a globally significant strategic reser ve for mega-scale solar deployment, green hydrogen, and long-term decarbonisation. 󾙓. Introduction Saudi Arabia is undergoing a major transformation of its energ y system as part of Vision 󾙔󾙒󾙕󾙒 and long-term net-zero ambitions. National electricity consumption has grown steadily, reaching roughly 󾙕󾙒󾙔 TWh in 󾙔󾙒󾙔󾙓, about 󾙕󾙒󾙛‒󾙕󾙓󾙒 TWh in 󾙔󾙒󾙔󾙔, and ≈ 󾙕󾙔󾙙 TWh in 󾙔󾙒󾙔󾙕. Converting this energ y to average power gives: Hence, Saudi Arabia’s average national electrical demand is about 󾙕󾙗‒󾙕󾙙 GW. However, peak summer demand—driven mainly by air-conditioning—reaches 󾙛󾙒‒󾙛󾙗 GW in July‒August afternoon hours. This strong seasonality and daily peak coincide with maximum solar irradiance, making solar PV particularly well aligned with the countr y’s load profile. The Rubʿ al-Khali (Empty Quarter) is the largest contiguous sand desert on Earth, with approximately 󾙖󾙕󾙒,󾙒󾙒󾙒 km² inside Saudi borders. It is extremely sparsely populated, characterized by hyper-arid climate, low cloud cover, and high solar irradiance. This combination of excellent solar resource and vast available land makes the Empty Quarter a prime candidate for gigaand tera-scale solar deployment, especially linked to green hydrogen and potential electricity exports. To characterise the solar potential of the Empty Quarter in a scientifically robust way, this study uses Sharurah (󾙓󾙙.󾙖󾙚°N, 󾙖󾙙.󾙓󾙔°E) as a representative southern Empty Averageload = ≈ 8760h/yr 327TWh/yr 37.3GW Quarter site, and compares it with Abqaiq (eastern oil/ industrial region) and Hail (inland northern desert city). The analysis is based on clearness -index-driven modelling, which provides a compact way to e valuate sky conditions and diffuse fraction. 󾙓.󾙓 Objectives The main objectives of this work are: To quantify H, H₀, and K_t for Sharurah (Empty Quarter), Abqaiq, and Hail using 󾙔󾙒󾙒󾙗‒󾙔󾙒󾙔󾙖 NASA POWER climatology. To compare the solar resource quality among these three locations, with particular focus on Empty Quarter vs. Hail. To estimate PV specific yields under realistic fixed-tilt system assumptions. To evaluate a 󾙗% land-use scenario in the Empty Quarter and compare its output to national consumption, in both energ y (TWh) and power (GW). To estimate economic payback in SAR and CO₂ emission reductions, highlighting the role of the Empty Quarter in Saudi Arabia’s long-term energ y strateg y. 󾙔. Background 󾙔.󾙓 Solar Resource in the Arabian Peninsula Previous solar resource assessments have shown that large parts of Saudi Arabia achieve global horizontal irradiation above 󾙔󾙒󾙒󾙒 kWh/m²·yr, placing the Kingdom in the top tier of global solar regions. Many studies, howe ver, focus on populated or industrial areas such as Riyadh, Dhahran, or Abqaiq, while the Empty Quarter remains less explored, despite its enormous theoretical capacity. 󾙔.󾙔 Clearness Index The clearness index K_t is defined as: K = t H 0 H where: H is the global horizontal irradiation at the ground (kWh/m²·day or kWh/m²·yr) H₀ is the extraterrestrial irradiation on a horizontal plane at the top of the atmosphere Typical interpretation: K_t < 󾙒.󾙕󾙗: Cloudy conditions 󾙒.󾙕󾙗 < K_t < 󾙒.󾙘󾙒: Mixed/cloudy K_t > 󾙒.󾙘󾙒: Clear sky K_t > 󾙒.󾙘󾙗‒󾙒.󾙙󾙒: Ver y clear, desert-like conditions Thus, K_t is a key parameter for classifying the quality of the solar resource and for driving diffuse fraction models. 󾙔.󾙕 Diffuse Fraction and Clearness -Index-Driven Modelling Recent work proposes empirical correlations that express the diffuse fraction k_d = D/H (where D is diffuse irradiation) as a function of K_t. For high K_t, diffuse fraction is low and beam irradiance dominates. This has se veral implications: Tilted PV yields higher gains relative to horizontal Tracking or bifacial systems can benefit significantly from the strong beam component The performance of PV systems is more predictable In this project, the focus is on K_t itself, but the same data can later be used in Engineering Equation Solver (EES) to apply clearness-index-based diffuse fraction correlations. 󾙕. Methodolog y 󾙕.󾙓 Study Locations Three sites in Saudi Arabia were selected for this comprehensive analysis: Site Latitude (°N) Longitude (°E) Description Sharurah (Empty Quarter) 󾙓󾙙.󾙖󾙚 󾙖󾙙.󾙓󾙔 Hyper-arid southern Empty Quarter Abqaiq 󾙔󾙗.󾙗󾙘 󾙖󾙛.󾙕󾙛 Eastern oil/ industrial region Hail 󾙔󾙙.󾙗󾙔 󾙖󾙓.󾙘󾙛 Inland northern desert city Sharurah represents the southern sector of the Empty Quarter, characterized by extensive sand dunes, low population, and strong solar resource. This location ser ves as the primar y focus for assessing the Empty Quarter’s potential, while Abqaiq and Hail provide important comparative baselines for understanding regional variations in solar resource quality. 󾙕.󾙔 NASA POWER Climatology (󾙔󾙒󾙒󾙗‒󾙔󾙒󾙔󾙖) For each site, monthly and annual climatolog y data (Januar y 󾙔󾙒󾙒󾙗‒December 󾙔󾙒󾙔󾙖) were obtained from the NASA POWER project in CSV format. The following parameters were used: ALLSKY_SFC_SW_DWN → H (kWh/m²·day): Global horizontal solar irradiation ALLSKY_KT → K_t (dimensionless): All-sky clearness index Monthly values for H (󾙓󾙔 months) and an annual average (ANN) are provided. For this analysis: 󾙓. Monthly H (kWh/m²·day) was multiplied by the number of days in each month to obtain monthly sums (kWh/m²·month). 󾙔. These were summed over all months to obtain annual H (kWh/m²·yr). 󾙕. H₀ was computed from standard solar geometr y rather than taken from the file, using site latitude, declination, and eccentricity correction, at a representative day in each month. 󾙖. Annual K_t was then calculated as: where the summation is over the 󾙓󾙔 months. 󾙕.󾙕 PV System and Yield Model To relate the solar resource to PV output, a simple but realistic model is employed: Fixed-tilt PV arrays, with tilt angle ≈ local latitude Plane-of-array (POA) gain factor = 󾙓.󾙓󾙗 (ratio of annual POA irradiation to annual horizontal irradiation in these clear desert climates) Performance ratio (PR) = 󾙒.󾙚󾙒, accounting for inverter, temperature, wiring, mismatch, soiling (assuming reasonable maintenance), and downtime Then the specific yield per installed kWp is: This is computed for Sharurah (Empty Quarter), Abqaiq, and Hail. 󾙕.󾙖 Economic Model (SAR Currency) To assess financial performance in local terms: Capital cost (CAPEX): 󾙚󾙒󾙒 USD/kWp ⇒ 󾙚󾙒󾙒 × 󾙕.󾙙󾙗 = 󾙕󾙒󾙒󾙒 SAR/kWp Internal value of electricity / avoided fuel cost : 󾙒.󾙒󾙘‒󾙒.󾙒󾙚 USD/kWh ≈ 󾙒.󾙔󾙔󾙗‒󾙒.󾙕󾙒󾙒 SAR/kWh Annual savings per kWp: Simple payback period (years): K = t,annual H ∑m0,m H ∑mm Y ≈ PV H × annual 1.15 × 0.80 [kWh/kWp\cdotpyr] S = annual Y ⋅ PV valueperkWh [SAR/kWp\cdotpyr] Payback = S annual 3000SAR/kWp 󾙕.󾙗 Land-Use Scenario in the Empty Quarter The Saudi portion of the Empty Quarter is estimated at ≈ 󾙖󾙕󾙒,󾙒󾙒󾙒 km². A hypothetical but illustrative scenario of 󾙗% land coverage with PV gives: A ssuming installed capacity density: total installed PV capacity is: The total annual generation is: which is converted to TWh/yr and compared against national electricity consumption. 󾙖. Results 󾙖.󾙓 Annual Solar Resource Metrics Based on the NASA POWER climatolog y and computed H₀, the annual results are presented in the following table: Site H (kWh/m²·yr) H₀ (kWh/m²·yr) K_t (annual) Sharurah (Empty Quarter) 󾙔󾙖󾙕󾙚.󾙖 󾙕󾙖󾙛󾙒.󾙖 󾙒.󾙘󾙛󾙛 Hail 󾙔󾙔󾙘󾙓.󾙙 󾙕󾙔󾙙󾙒.󾙓 󾙒.󾙘󾙛󾙔 Abqaiq 󾙔󾙓󾙛󾙕.󾙛 󾙕󾙕󾙔󾙒.󾙔 󾙒.󾙘󾙘󾙓 Key obser vations: Sharurah (Empty Quarter) has the highest annual H of the three sites and the highest K_t, almost 󾙒.󾙙󾙒, confirming an extremely clear desert atmosphere. Hail also has excellent resource and high K_t , but both H and K_t are slightly lower than Sharurah. A = PV 0.05 × 430, 000 ≈ 21, 500km2 D = PV 60MWp/km2 C = installed A ⋅ PV D = PV 21, 500 × 60 ≈ 1, 290GWp E = annual C ⋅ installed Y [kWh/yr] PV Abqaiq shows lower H and K_t, consistent with higher aerosol load and partial cloudiness near industrial regions. Thus, Sharurah clearly emerges as the best of the three sites, both in terms of total solar energy and atmospheric clarity. Figure 󾙓: Solar Resource Comparison (H, H₀, and K_t) The above figure illustrates the comparative analysis of global horizontal irradiation (H), extraterrestrial irradiation (H₀), and clearness index (K_t) across the three study locations. Sharurah demonstrates superior performance in all three metrics, confirming its status as the optimal site for solar energ y development in the region. 󾙖.󾙔 PV Specific Yield Using the formula: we obtain the following specific yields: Sharurah (Empty Quarter): $ $ Hail: $ $ Abqaiq: $ $ Y = PV H × annual 1.15 × 0.80 Y ≈ PV,Sharurah 2438.4 × 1.15 × 0.80 ≈ 2243kWh/kWp\cdotpyr Y ≈ PV,Hail 2261.7 × 1.15 × 0.80 ≈ 2081kWh/kWp\cdotpyr Y ≈ PV,Abqaiq 2193.9 × 1.15 × 0.80 ≈ 2018kWh/kWp\cdotpyr Site PV Yield (kWh/kWp·yr) Sharurah (Empty Quarter) 󾙔󾙔󾙖󾙕 Hail 󾙔󾙒󾙚󾙓 Abqaiq 󾙔󾙒󾙓󾙚 This means Sharurah delivers ~󾙚% more energy per kWp than Hail and ~󾙓󾙓% more than Abqaiq, which has important implications for LCOE and payback . Figure 󾙔: PV Specific Yield Comparison The figure above demonstrates the significant advantage of Sharurah in terms of PV system output. The 󾙚% improvement over Hail and 󾙓󾙓% improvement over Abqaiq translate directly into faster payback periods and superior long-term economic returns for solar projects in the Empty Quarter. 󾙖.󾙕 National Load, Peak Demand, and Grid Integration Saudi Arabia’s total electricity consumption of 󾙕󾙒󾙔‒󾙕󾙔󾙙 TWh/yr corresponds to an average load of 󾙕󾙗‒󾙕󾙙 GW. In summer, peak demand reaches 󾙛󾙒‒󾙛󾙗 GW, mainly due to air conditioning. References [󾙓] NASA POWER Project . (󾙔󾙒󾙔󾙖). “Prediction of Worldwide Energy Resources.” NASA POWER Agroclimatolog y. Retrie ved from https://power.larc.nasa.gov/ [󾙔] Paulescu, M., Paulescu, E., Gravila, P., & Badescu, V. (󾙔󾙒󾙔󾙕). “Weather Modeling and Forecasting of PV Systems Operation.” Springer. [󾙕] Zell, E., Gasim, S., Wilcox , S., Katamoura, S., Soteris, K., Perez, R., & Renne, D. (󾙔󾙒󾙓󾙗). “A ssessment of Solar Radiation Resources in Saudi Arabia.” Solar Energy, 󾙓󾙓󾙛, 󾙖󾙔󾙔‒ 󾙖󾙕󾙚. [󾙖] Saudi Electricity Company (SEC). (󾙔󾙒󾙔󾙖). “National Electricity Consumption and Peak Demand Data.” SEC Annual Report. [󾙗] Vision 󾙔󾙒󾙕󾙒. (󾙔󾙒󾙔󾙖). “Saudi Arabia’s Long-term Energy Strategy and Renewable Energy Goals.” Retrieved from https://www.vision󾙔󾙒󾙕󾙒.gov.sa/ Document Prepared By: Mohammed Almarri Institution: King Fahd University of Petroleum and Minerals (KFUPM) Date: November 󾙔󾙔, 󾙔󾙒󾙔󾙗 Status: Final Research Report