This study investigates the thermal performance of a proposed design for a particle-based thermal energy storage (PBTES) system. A small-scale TES bin was constructed using masonry materials and a multi-layered structure. The primary objectives were to quantify heat loss through the bin’s wall and to evaluate the thermal conductivity of the insulating material, calcium silicate (CS), at elevated temperatures. Heat transfer rates were measured and calculated using two methods, yielding a minimal discrepancy of 3% between the results. The thermal conductivity of the CS was determined to be 0.115 W/m·K, indicating its effectiveness as a thermal barrier. Additionally, the expansion joint (EJ) layer demonstrated the ability to recover its original thickness after cooling, confirming its utility in relieving stresses resulting from the thermal expansion of the inner layers. These findings support the scalability and efficiency of the proposed PBTES system design.

The direct particle heating receiver (DPHR) represents a critical component within particle-based central receiver tower (CRT) systems, facilitating direct exposure of solid particles to concentrated solar irradiance. Among DPHRs, the obstructed flow particle heating receiver (OF-PHR) emerges as a novel design under development at King Saud University (KSU), enabling particles to descend freely in a curtain-like manner through straight-shaped porous obstructions. This configuration effectively attenuates particle acceleration during descent, thereby prolonging their residence time within the irradiated zone. The innovative design of a porous OF-PHR significantly enhances particle heating by forming a well-dispersed and substantially thicker particle curtain. Within this curtain, micro-cavities are generated, which dramatically reduce radiation loss to the sky by facilitating multiple reflections, effectively trapping intercepted rays, and thereby maximizing solar absorptance. Achieving high solar absorptance offers substantial economic benefits by enabling the storage of thermal energy in low-cost, naturally abundant solid particles, such as silica sand, despite their inherently poor optical properties. This research studies the main aspects that influence the effective solar absorptance (ESA) of the direct porous OF-PHR. A high-flux module (HFM) was devised and constructed to experimentally assess ESA, comprising a particle-handling unit, a primary concentrator, and a secondary concentrator. Particle curtain ESA was scrutinized across various parameters, particle flow rate, and PHR structural geometry, represented by porous obstruction packing, perforation size, and arrangements. Experimental tests were conducted on white sand (WS). ESA was compared to that of another two PHR configurations: Bare, and free-fall PHRs. ESA measurements revealed a substantial enhancement in particle curtain absorptivity compared to the particle-packed bed. The WS curtain attained a peak ESA of 0.85, contrasting with the packed bed absorptance of 0.42.

This paper presents the design, construction, and preliminary testing of an innovative skip-hoist particle lift (PL) integrated with a multi-layered cylindrical thermal energy storage (TES) system for particle-based concentrated solar power (CSP) applications. The skip-hoist PL, constructed with stainless steel for high-temperature compatibility, was seamlessly integrated with two TES bins on a 22-m concrete tower. Preliminary testing at ambient temperature confirmed the system’s operational feasibility, paving the way for high-temperature testing and the proposed 1.3 MWe pre-commercial scale-up in Waad Al-Shamal, Saudi Arabia.

Using solid particulates as a heat transfer medium for concentrated solar power (CSP) systems has many advantages, positioning them as a superior option compared with conventional heat transfer media such as steam, oil, air, and molten salt. However, a critical imperative lies in the comprehensive evaluation of the properties of potential solid particulates intended for utilization under such extreme thermal conditions. This paper undertakes an exhaustive examination of both ambient and high-temperature thermophysical properties of four naturally occurring particulate materials, Riyadh white sand, Riyadh red sand, Saudi olivine sand, and US olivine sand, and one well-known engineered particulate material. The parameters under scrutiny encompass loose bulk density, tapped bulk density, real density, sintering temperature, and thermal conductivity. The results reveal that the theoretical density decreases with the increase in temperature. The bulk density of solid particulates depends strongly on the particulate size distribution, as well as on the compaction. The tapped bulk density was found to be larger than the loose density for all particulates, as expected. The sintering test proved that Riyadh white sand is sintered at the highest temperature and pressure, 1300 °C and 50 MPa, respectively. US olivine sand was solidified at 800 °C and melted at higher temperatures. This proves that US olivine sand is not suitable to be used as a thermal energy storage and heat transfer medium in high-temperature particle-based CSP systems. The experimental results of thermal diffusivity/conductivity reveal that, for all particulates, both properties decrease with the increase in temperature, and results up to 475.5 °C are reported.

Understanding particles flow behavior is of paramount importance in designing obstructed flow particle heating receivers (OF-PHR), and one of the important metrics is opacity of the particle curtain. In this work, the opacity is defined geometrically, i.e., ratio of area covered by the particles to the total area of the curtain. Particle curtain opacity of an OF-PHR having a single row obstruction was measured. The obstructions tested were perforated plates with two different holes-arrangements, i.e., parallel and staggered. Plate thickness, hole diameter, and pitch were measured to be 1.38, 2.84, and 4.29 mm, respectively, with angles of 60° between three adjacent holes. Two different fall distances (release point) above the obstruction were tested: 30 mm and 60 mm. The tilt angle and mass flow rate used were fixed, i.e., 0° and 1.91 kg/(s∙m), respectively. The opacity was measured across a region for every 20 mm below the obstruction (0-20, 20-40, 40-60, and 60-80 mm); the opacity encompassing the whole region (0-80 mm; overall opacity) was also measured. It was found that the fall distance affects the opacity a little, i.e., doubling the distance from 30 to 60 mm only increased the opacity by 14.4% (relative change) at most. Parallel and staggered hole arrangement resulted in very close values of particle curtain opacity. Finally, it is concluded that to ensure opacity values to remain equal or greater than 85% throughout PHRs with multiple rows downstream, spacing between the perforate plate should be no greater than 40 mm.

Stand-alone solar cooling technologies are under development and cannot compete economically with conventional cooling systems. Integration of particle-based concentrating solar power (PBCSP) systems with thermally driven cooling systems can provide an advantage over stand-alone solar cooling systems by providing low-cost, eco-friendly electricity and cooling energy. Consequently, this research proposes to investigate and identify the best configuration for the integrated system deployment to provide electricity and cooling energy in Tabuk province in Saudi Arabia and evaluate the levelized cost of electricity (LCOE) for the particle-based concentrating solar power and the levelized cost of cooling (LCOC) for the thermally driven cooling systems. Tower height and receiver dimensions of the particle-based concentrating solar power are found by performing techno-economic optimization in SolarPILOTTM and SAMTM. The performance of the particle-based concentrating solar power block and the thermally driven cooling systems is evaluated by simulating the thermodynamic model in EESTM. These models are validated by the manufacturers' datasheets. Cost models are defined to be used in the economic analysis. The exhaust gas double-effect absorption chiller (EGDEAC) is selected as the thermally driven cooling system. The result of thermodynamic performance analysis shows the particle-based concentrating solar power has an annual electricity production of 191 TWh from solar energy alone, with the power block exhaust having an average flow rate of 386 Mg/h and an average yearly exhaust temperature of 378 degrees C. On the other hand, the exhaust gas double-effect absorption chiller produces an annual cooling energy of 97,461,948 TR-h with an average COP of 1.456. The economic results demonstrate that the proposed system achieves a levelized cost of electricity, and levelized cost of cooling of 6.08 cent/kWh and 3.77 cent/TR-h, respectively. When this levelized cost of cooling is compared with the conventional mechanical vapor compression (MVC) cooling system, the result shows that the exhaust gas double-effect absorption chiller is competitive and has one-third of the levelized cost of cooling of mechanical vapor compression. The sensitivity analysis was also made on related influencing factors for the levelized cost of cooling. The analysis shows that the levelized cost of cooling of exhaust gas double-effect absorption chiller is sensitive to the amount of the output cooling energy and the total system cost.

Particles are a leading contender for next-generation, concentrating solar power technologies, and the design of the particle receiver is critical to minimize the levelized cost of electricity. Falling particle receivers (FPRs) are a viable receiver concept, but many new designs feature complex particle obstructions that include dense discrete phase flows. This creates additional challenges for modeling as particle-to-particle interactions (i.e., collisions) and particle drag become more complex. To improve upon existing modeling strategies, a CFD-DEM simulation capability was created by coupling two independent codes: Sierra/Fuego and LAMMPS. A suitable receiver model was then defined using a traditional continuum-based model for the air and a granular model for the particle curtain. A sensitivity study was executed using this model to determine the relevance of different granular model inputs on important quantities of interest in obstructed flow FPRs: the particle velocity and curtain opacity. The study showed that the granular model inputs had little effect on the particle velocity magnitude and curtain opacity after an obstruction.

One of the main components of particle-based power tower (PBPT) systems is the particle heating receiver (PHR), through which solid particles are heated by concentrated sunlight. An obstructed-flow PHR (OF-PHR) developed by King Saud University is a type of PHR that has inverted V-shaped obstructions made of Inconel meshes, called chevrons, allowing for a longer time of sunlight exposure on the particles; hence, overcoming one of the limitations of free-fall PHRs. Two problems have been observed with this OF-PHR: (1) a considerable amount of the falling particles bounces forward and leaves the chevrons region; (2) it has a high packing density of chevrons that results in a very low falling particle velocity, which can lead to chevrons overheating. The present research attempts to resolve these issues and improve the PHR performance by understanding deeply the falling-particles behavior of OF-PHRs. The effects of (i) vertical spacing of chevrons and (ii) porosity of chevron meshes, (iii) PHR tilt angle, (iv) particle mass flow rate, and (v) type of particulate material were studied, at room temperature, concerning the following metrics: (1) particle velocity, (2) particle retention, and (3) particle curtain opacity. It was found that the particle velocity profile was nearly identical throughout the OF-PHR, which means that the obstructions successfully limited the particle falling speed. As for the PHR tilt angles, values below 10° were not sufficient to effectively retain the particles flowing through the chevron meshes since many particles bounced and left the PHR (low particle retention). Chevron's vertical spacing showed the most significant effect on particle opacity, with 30 mm spacing resulting in opacity values greater than 94 %. Two types of particulate material were tested, olivine sand and CARBOBEAD; the particle curtain opacity values using these materials were found to be comparable. By having high particle retention, sufficiently low particle falling speed, and high particle curtain opacity, the number of falling particles “controlled” by the obstructions (chevrons) is high; hence, a high number of particles has increased residence time, which will lead to higher PHR outlet temperatures. Moreover, high particle opacity ensures that most of the sunlight strikes the particles instead of the back side of the PHR and the obstructions (chevrons), ensuring optimal absorption of the solar energy and protecting the PHR construction from overheating/damage.

Researchers from all around the world have been paying close attention to particle-based power tower technologies. On the King Saud University campus in the Kingdom of Saudi Arabia, the first integrated gas turbine–solar particle heating hybrid system has been realized. In this study, two different types of experiments were carried out to examine how susceptible prospective liner materials for thermal energy storage tanks were to erosion. An accelerated direct-impact test with high particulate temperature was the first experiment. A low-velocity mass-flow test was the second experiment, and it closely mimicked the flow circumstances in a real thermal energy storage tank. The tests were conducted on bare insulating fire bricks (IFBs) and IFBs coated with Tuffcrete 47, Matrigun 25 ACX, and Tuffcrete 60 M. The latter three lining materials were high-temperature-resilient materials made by Allied Mineral Products Inc. (AMP) (Columbus, OH, USA). The results showed that although IFBs coated with AMP materials worked well in this test, the accelerated direct-impact test significantly reduced the bulk of the bare IFB. As a result, lining substances must be added to the surface of IFBs to increase their strength and protection because they cannot be used in situations where particles directly impact their surface. On the other hand, the findings of the 60 h cold-particle mass-flow test revealed that the IFBs were not significantly eroded. Additionally, it was discovered that the degree of erosion on the samples of bare IFB was unaffected by the height of the particle bed.

Solar energy has the potential to provide most of the electricity needed by mankind sustainably into the indefinite future. Concentrated Solar Power (CSP) has conventionally been considered more applicable than photovoltaic (PV) for baseload power since thermal storage is far cheaper than battery storage. However, the solar fields for CSP are relatively expensive. On the other hand, PV plants without storage deliver electric power at a much lower cost than CSP plants of comparable capacity without storage. Integrating both technologies is an attractive approach towards solar baseload power with affordable levelized cost of energy (LCOE). This study, which investigates the two cities of Saudi Arabia, consists of simulation and optimization in three main parts: The first part is a simulation of the CSP parabolic trough (CSP-PT) standalone plant and integrating the output parameters with an economic model to calculate the LCOE. The second part is the simulation of combined CSP-PT with PV, with a design strategy of utilizing all PV power for daytime use, and supplementing the PV output with thermal power as needed to maintain baseload operation in the daytime. The third part is the simulation of combined CSP-PT with a design strategy of providing all or nearly all daytime power with PV, with the utilization of excess energy from PV to supply heat to the thermal storage system. The results show that for a target capacity factor of 79%, the CSP plant alone requires a solar multiple of 6 in Riyadh and 3.5 in Tabuk. For both locations, the introduction of the hybrid concept substantially reduced the solar multiple. In Riyadh, the solar multiple ranged from 2.9 to 3 with the PV portion of the plant having a nameplate capacity equal to that of the CSP portion and 1.95 for a case with the PV nameplate capacity 60% greater than the CSP portion. For these same cases in Tabuk, the solar multiples were 1.78–1.85 and 1.6 simultaneously. Generally, hybridization is of greater benefit in Riyadh than in Tabuk owing to the greater fraction of solar resource in the form of diffuse sunlight which can be collected by the PV plant but not by the CSP plant. The LCOE was reduced by hybridization in both locations, but again the benefit was greater for Riyadh. Clearly, from a technological perspective, it is important to study the hybridization for an individual city based on its weather data as the incorporation of PV into CSP plant designs should be considered for all locations in order to reduce the cost to provide baseload power from solar energy, and the application of the hybridization concept can extend the applicability of CSP technology to regions with less direct sunlight than would be economically feasible with CSP alone.

In this research, the main objective was to develop, design, and construct an economical Thermal Energy Storage (TES) system for storing heated solid particles used as a heat transfer medium in Concentrating Solar Power (CSP) with a total cost not exceeding ${\$}$5/kWh and 1% maximum heat loss of the overall system energy per day as per sunshot initiative of US department of energy. The TES is to be used for storing heated solid particles in a 1.3MWe CSP system designed for construction at Waad Al-Shamal, Saudi Arabia. Initially, the TES was made by high-density fire brick (HFB), insulation fire brick (IFB), perlite concrete (PC), expansion joint (EJ), and reinforced concrete (RC). It was discovered that (PC) has to be mixed with refractory cement. This mixture increased the PC’s layer cost, so the design changed by eliminating the (PC) layer and only using IFB in terms of insulation. The theoretical results of the new case showed that the optimum thickness of IFB should be 0.414m}, and the cost of the system’s materials was ${\$}$2.352/kWh. The system was further modified to reduce the cost. This modification was done by replacing IFB with Calcium Silicate (Ca 2 SiO 4 ). These modifications showed that the new optimum insulation thickness is 0.325m and the total cost of the system was ${\$}$2.304/kWh which is lower than the previous case.