Particle Solar Receiver Research Articles

Design, simulation and on-sun experiments of a modified sliding-bed particle solar receiver for coupling with tower concentrating system

A modified sliding-bed particle solar receiver was proposed to realize the coupling with upward concentrating system, which was a challenge for the previous designs. The newly added secondary reflection structure could not only adjust the optical path, but also preheated the particles flowing behind it. The overall principle of the receiver, the regulation mechanism of the particle layer thickness and the control and measurement method of the particle flowrate have all been described in detail. After the cold-state research on flow pattern, on-sun experiments based on a tower concentrating system were conducted to evaluate the receiver performance. Experimental results showed that the maximum outlet temperature of ∼860°C and single-pass temperature rise of ∼510°C were achieved. Under various DNI and time, the average outlet temperature ranging from ∼535 °C to 782 °C, and positive efficiency ranging from ∼51 % to 66 % were obtained. A concentrating-receiving coupled model was proposed to analyze the energy transfer process during the experiments, and to predict the receiver performance under higher incident power. Simulation results showed that the thermal loss rate could be reduced from 28.48 % to 13.22 % with 5 times magnification of the incident power, but the local overheating risk of the secondary reflective surface required attention.

Allothermally Heated Reactors for Solar-Powered Implementation of Sulphur-Based Thermochemical Cycles

Catalytic sulphur trioxide splitting is the highest-temperature (650-950oC), endothermic step of several sulphur-based thermochemical cycles targeted to production of hydrogen or solid sulphur. Concentrated solar power tower plants are an attractive renewable energy source to provide the necessary heat. Furthermore, the development of solar receivers capable of delivering solid or gaseous heat transfer fluids at these temperature ranges enable the implementation of such endothermic reactions in allothermally-heated reactors/heat exchangers placed away from the solar receiver. In this context, a 2-kW laboratory-scale shelland-tube reactor/heat exchanger to perform thermal sulphuric acid decomposition and catalytic sulphur trioxide splitting was in-house designed, built and tested with electrically heated bauxite particles, in the perspective of eventually coupling such a reactor with a centrifugal particle solar receiver. Thermal test runs demonstrated the in-principle feasibility of the concept. The temperatures reached were sufficient to ensure complete sulphuric acid evaporation. However, the ones in the SO3 splitting zone were of the order of 750°C, high enough to demonstrate SO3 splitting but not reaching the levels required for close-toequilibrium conversion of the Fe2O3 catalyst system used (~ 850oC). An improved version of the reactor is under construction incorporating design modifications based on lessons learned from the test campaigns, in the perspective of scaling up the process.

Two-Fluid and Discrete Element Modeling of a Parallel Plate Fluidized Bed Heat Exchanger for Concentrating Solar Power

Abstract A novel high-temperature particle solar receiver is developed using a light trapping planar cavity configuration. As particles fall through the cavity, the concentrated solar radiation warms the boundaries of the receiver and in turn heats the particles. Particles flow through the system, forming a fluidized bed at the lower section, leaving the system from the bottom at a constant flowrate. Air is introduced to the system as the fluidizing medium to improve particle heat transfer and mixing. A laboratory scale cavity receiver is built by collaborators at the Colorado School of Mines and their data are used for model validation. In this experimental setup, near IR quartz lamp is used to provide flux to the vertical wall of the heat exchanger. The system is modeled using the discrete element method and a continuum two-fluid method. The computational model matches the experimental system size and the particle size distribution is assumed monodisperse. A new continuum conduction model that accounts for the effects of solid concentration is implemented, and the heat flux boundary condition matches the experimental setup. Radiative heat transfer is estimated using a widely used correlation during the post-processing step to determine an overall heat transfer coefficient. The model is validated against testing data and achieves less than 30% discrepancy and a heat transfer coefficient greater than 1000 W/m2 K.

Medium- and High-Entropy Rare Earth Hexaborides with Enhanced Solar Energy Absorption and Infrared Emissivity.

The development of a new generation of solid particle solar receivers (SPSRs) with high solar absorptivity (0.28-2.5 μm) and high infrared emissivity (1-22 μm) is crucial and has attracted much attention for the attainment of the goals of "peak carbon" and "carbon neutrality". To achieve the modulation of infrared emission and solar absorptivity, two types of medium- and high-entropy rare-earth hexaboride (ME/HEREB6) ceramics, (La0.25Sm0.25Ce0.25Eu0.25)B6 (MEREB6) and (La0.2Sm0.2Ce0.2Eu0.2Ba0.2)B6 (HEREB6), with severe lattice distortions were synthesized using a high-temperature solid-phase method. Compared to single-phase lanthanum hexaboride (LaB6), HEREB6 ceramics show an increase in solar absorptivity from 54.06% to 87.75% in the range of 0.28-2.5 μm and an increase in infrared emissivity from 76.19% to 89.96% in the 1-22 μm wavelength range. On the one hand, decreasing the free electron concentration and the plasma frequency reduces the reflection and ultimately increases the solar absorptivity. On the other hand, the lattice distortion induces changes in the B-B bond length, leading to significant changes in the Raman scattering spectrum, which affects the damping constant and ultimately increases the infrared emissivity. In conclusion, the multicomponent design can effectively improve the solar energy absorption and heat transfer capacity of ME/HEREB6, thus providing a new avenue for the development of solid particles.

Discrete Element Method Modelling of the Particle Flow in Centrifugal Solar Particle Receiver

The centrifugal solar particle receiver (CentRec) is a promising design compared to other particle receiver concepts because it allows for an active adjustment of particle residence time and particle outlet temperature by adjusting the rotational speed of the drum and particle mass flow rate. A Discrete Element Method (DEM) tool is utilized to model the particle flow in CentRec. However, the numerical modeling of the particle flow in large scale receiver is computationally infeasible because of excessive number of particles in the simulation. Thus, in this study, a scale down approach is developed and validated to be used to estimate the particle film characteristics in large scale receivers. The particle velocity profile and film thickness distribution are employed to compare different receiver sizes.

Numerical investigations of structural modification and particle geometric parameters on the heat transfer performance of falling particle solar receiver

Falling particle solar receiver (FPSR) has higher operation temperature, lower investment, higher pressure bearing capacity and more direct heat energy storage than those of traditional tube receiver. The FPSR is usually arranged with an opening aperture to avoid the loss of reflected solar radiation. Thus, they have not been widely employed in commercial plants due to the convective and radiative heat loss through the aperture. In this contribution, in order to reduce the heat loss through the aperture, we analyze the arrangement of the particle curtain and aperture, the effect of particle diameter on the deformation of particle curtain. The results show that the particles temperature of reaching bottom Tb and the maximum temperature Tmax is related to the particle diameter ds, and the difference between Tmax and Tb, ΔT, decreases with the increase of ds. Moreover, raising the distance between aperture and bottom surface can increase the particle temperature up to 63.6K. In addition, the particle diameter size will lead the deformation of particle curtain and furthermore lead to an ununiform temperature distribution of the particles. The numerical results show that ΔT of particles at the same height is up to 142.7K. Finally, we add the air nozzles at the aperture and found that increasing the temperature of the nozzle jet stream can effectively increase the particle temperature. This contribution can provide a guidance for the design of falling particle solar receivers.

Numerical investigation of flow and heat transfer characteristics in a fluidized bed solar particle receiver

Numerical investigation of flow and heat transfer characteristics in a fluidized bed solar particle receiver

Performance assessment of a system to provide steady high temperature air via solar thermal suspension flow technology with storage and combustion back-up

The imperative for economically viable sources of high-temperature heat without contributing to net carbon emissions has become a pressing global concern, particularly in the context of industrial chemical processes. Solar thermal heat generation emerges as a pivotal solution in addressing this formidable challenge. By concentrating sunlight to achieve high temperatures, solar thermal technology can provide the intense heat required for various industrial applications, including chemical processes, without relying on fossil fuels. This not only helps reduce greenhouse gas emissions but also enhances energy efficiency and sustainability in energy-intensive industries. However, the full integration of solar thermal systems into energy-intensive industrial processes necessitates continued advancements of new technologies to achieve temperatures in the order of 1000 °C. In this paper, the performance of a high temperature concentrating solar thermal plant based on a 50MWth suspension flow solar particle receiver sub-system integrated with sensible thermal storage and combustion backup is analyzed, to supply steady output of reheated air to a downstream thermochemical process. The analysis is performed with transient mathematical models of the receiver and packed bed thermal storage sub-systems considering solar resource variability, written in a Simulink environment, to estimate useful annual thermal gain, thermal efficiency, solar share and levelized cost of solar heat, for a range of parameters including particle mass loading, air mass flow rate, thermal storage capacity and solar multiple. The time-dependent temperature fields of the receiver and thermal losses, together with their influence on the performance of the combined system are reported for each condition with a transient input solar resource spanning over a whole year. New insights are provided of the relative tradeoffs between these parameters on the overall system performance, solar share and levelized cost of solar energy. Also reported is the sensitivity of the levelized cost to different system combinations sized to provide a solar share of up to 75 % of the yearly process thermal demand, along with the influence of the specific costs of the system components varied in the range of ± 60 %.

The performance evaluation of the free-falling particle solar receiver with a novel zigzag mass-flow controlled particle release pattern

A free-falling particle receiver is a promising technology to be used in concentrating solar power plants. In this study, an optical-thermal coupled model is established by combining a Monte Carlo ray-tracing method with a finite volume method to simulate the energy transfer processes in a solar power tower system employing a cavity receiver. Using the developed model, a novel particle release pattern, zigzag mass-flow controlled pattern, is proposed and compared with three other patterns, straight-line, zigzag, and mass-flow controlled patterns. First, the effects of the amplitude of the zigzag particle release slots on the receiver performance are analyzed. Then, the variations of the solar energy entering the receiver at different times on the vernal equinox is studied. Moreover, a new particle release pattern, zigzag mass-flow controlled pattern, is proposed and evaluated. The results demonstrated that the thermal performance of the zigzag mass-flow controlled particle release pattern was found to be superior to the other three patterns, allowing an increase in the thermal efficiency of 2.90 %. This allows for achieving effective thermal performance improvements while employing cost-effective designs in the free-falling particle receiver.

Numerical study of aeration flow angle on powder flow and thermal behaviors in fluidized bed particle solar receivers

The particle flow and thermal characteristics in fluidized bed particle solar receivers with different aeration flow angles were numerically investigated by employing the Eulerian-Eulerian two-fluid model. The filtered drag correlation was utilized to characterize the interaction between SiC particles of Geldart-A classification and gas. The model underwent validation using experimental data from the literature, confirming that the simulated solid holdup and local heat transfer rate agreed well with the experimental measurements. Simulation results show that the particle volume fraction was higher along the walls in the bottom section. In both +45° and + 60°, the particles returned to the aeration flow region. The aeration had a relatively small impact on the particle distribution at the center, whereas the other two regions (x / D = 0.5 and 0.95) exhibited a significant decrease in particle volume fraction at the height of aeration injection. For different aeration injection structures, the equilibrium temperature rise reached approximately 51% of the difference between the wall and inlet temperatures. The temperature rise of particles in FBPSR was attributed to the direct heat transfer from the heating wall to particles and he return of hot particles.

Modification of high temperature radiation absorption properties of solid particles with surface coating

The coatings with different thermodynamic and optical properties can adjust and improve the overall performance of solid particles in solid particle solar receivers (SPSRs). In this work, the manganese iron black (PBK26) coating is prepared by water bath method and comprehensive performance of the coating is found to be the best when Fe/Mn molar ratio in PBK26 is 4:1. The high temperature radiation absorption performances of different solid particles coated by PBK26 are investigated. The results show that the spectral absorptivity of particles can be greatly improved by coating. The average spectral absorptivity of quartz sand, bauxite and mullite increases by 25.9%, 20.8% and 16.2%, respectively. However, the coated quartz sand appears coating shedding phenomenon at high temperatures, and the coating on bauxite is not complete. Only the coated mullite shows excellent coating effect and thermal stability. After long-period high temperature thermal stability experiments at 900 °C and cyclic thermal stability experiments of 30 cycles, the maximum mass loss of coated mullite is less than 0.4% and the spectral absorptivity is almost unchanged. In the wear resistance experiments the surface debris of the coated mullite increases. And there is a mass loss of 8.244% with a coating thickness loss of 27% and a spectral absorptivity decrease of 3.88% after 10 h of wear at 900 rpm. The results imply good high temperature thermal stability and acceptable wear resistance of PBK26 coated mullite, which provide an option for high temperature radiation improvement of solid particles.

Techno-economic assessment from a transient simulation of a concentrated solar thermal plant to deliver high-temperature industrial process heat

The need for new technologies to provide economically viable sources of high-temperature heat without any net CO2 emissions for industrial chemical processes has become a global priority. Concentrated solar thermal heat generation can play an important role in meeting this challenge. We report a detailed bottom-up techno-economic analysis of a concentrated solar thermal plant to deliver process heat at a temperature of 1100 °C at the scale anticipated for a commercial demonstrator. The system consists of a 50 MWth solar concentration subsystem with heliostats and a tower, a novel solar expanding-vortex particle receiver (SEVR) and a packed bed storage system, together with a combustion back-up to allow continuous operation. The system was optimized to determine the minimum levelized cost of heat (LCOH) from a detailed transient model of the complete system. Significantly, the system with the maximum efficiency for the receiver or storage alone does not deliver the best annual energetic performance, highlighting the need to understand the detailed interplay between the two systems to optimize overall performance. While this system is not yet optimized for the lowest cost of industrial heat, the sensitivity analysis provides important insight as to how to move toward this optimum. This system yields the lowest values of LCOH for the solar component of between 37 and 39 USD/GJ for a corresponding annual solar share (SSann) of 28% and 53% of the total heat demand of the industrial process, respectively. However, importantly, this solar share can be almost doubled for only a 5% increase in LCOH.

Experimental and simulation study of Mn–Fe particles in a controllable-flow particle solar receiver for high-temperature thermochemical energy storage

CSP systems hold tremendous potential for large-scale and long-duration energy storage. However, their extensive adoption has been impeded by cost constraints. To overcome this hurdle, the development of the next generation CSP systems, focusing on high-temperature heat absorption and storage, is paramount for reducing the LCOE. The integration of TCES technologies shows promise in bolstering energy storage density, stability at high temperatures, and decreasing the LCOE. This study investigates the performance of Mn–Fe particles in a controllable-flow particle receiver operating at high temperatures. Experimental data demonstrate that the particles reach a maximum temperature of 1041.8 °C, resulting in an outstanding outlet particle thermochemical reaction conversion rate of 96.35%. Critical parameters influencing receiver performance were also examined meticulously. It was observed that increased incident flux density significantly enhanced receiver efficiency of 88%. Moreover, effective management of local overheating through the integration of TCES proved indispensable. The outlet particle temperature differential was merely 9.53 °C, and the sudden fluctuations in incident flux led to a limited temperature rise of 4.84 °C, attributing to intensified reaction enthalpy and reaction rate. By optimizing operational stability, continuous operation of CSP systems under high temperatures can be achieved, maximizing efficiency and allowing for greater system flexibility.

A Review of Radiative Heat Transfer in Fixed-Bed Particle Solar Receivers

A highly efficient receiver is required because re-radiation loss increases dramatically with increased working temperature. Among a large number of receivers, the fixed-bed Particle Solar Receiver (PSR) represents a new pathway to high temperature with maximum overall thermal efficiency. The incoming solar radiation can penetrate deeper into the fixed-bed PSR filled with semi-transparent quartz and ceramic particles (spheres or Raschig rings), resulting in an increased volumetric effect. Reports show that an optimized PSR can realize overall receiver efficiency of around 92% at outlet temperatures above 1000 K, and achieve the annual temperature above 1000 K over 65% annual operating hours integrated with a concentrated solar power (CSP) system. To fully understand radiative heat transfer characteristics and provide deep insight into thermal efficiency, radiation energy is classified as incident solar radiation and radiative heat exchange in two parts. The transfer mechanism, the solution method and the progress of the investigation for each section are summarized and discussed in detail. Then, challenges and future directions, including an innovative design method, an improved experimental approach and an effective simulation method are proposed to put forward this receiver to be a preferred substitute in advanced, high-temperature power cycles.

Performance modeling of quartz tube for gravity-driven solid particle solar receiver

The interest in high-temperature solar receivers is increasing due to more and more applications in industrial fields. The solid particle is a promising heat transfer fluid for high-temperature receivers owing to the advantages of direct absorption, low cost, and high allowable temperature (∼1300 °C). The re-radiation losses of solid particles inevitably increase with the higher operating temperature. The quartz tube with a spectral selective transmissivity may be used for reducing re-radiation losses. This paper proposed a mathematical model to describe the heat transfer behaviors of the gravity-driven solid particle solar receiver with a quartz tube covered. The wavelength-dependent radiative properties of the quartz tube and particles were approximated by a gray band method. On-sun tests based on a linear-focused solar furnace were conducted, and test results verified the proposed model. Analysis results show that a reduction in β from 3676m−1 to 1000m−1 can boost the volume absorption effect and increase the solar-to-thermal efficiency from 0.54 to 0.64. A double-layered quartz tube design provides the best thermal performance by increasing the greenhouse effect of the quartz tube from −0.02∼0.08 to 0.41. The analysis results could be used for the optimal design and operation of the gravity-driven solid particle solar receiver.

The Performance Evaluation of the Free-Falling Particle Solar Receiver with a Novel Zigzag Mass-Flow Controlled Particle Release Pattern

The Performance Evaluation of the Free-Falling Particle Solar Receiver with a Novel Zigzag Mass-Flow Controlled Particle Release Pattern

Physical property design of multi-component particle systems as heat transfer medium for directly irradiated solar receiver

• New particle candidates considered as the HTM for directly irradiated SPSRs. • The different particles mixed to form novel multi-component particle systems. • The absorption property increases with the addition of dark colored materials. • Thermal performance of particle systems enhanced in a falling quartz tube SPSR. In directly irradiated solid particle solar receivers (SPSRs), the performance of the heat transfer and thermal energy storage medium is a hot research topic. Herein, the thermophysical properties, thermal stability, surface morphology, element compositions and absorptivities of 16 kinds of candidate particles are studied and evaluated. Considering that the performance of homogenous particles as heat transfer medium (HTM) is not ideal, a novel concept of multi-component mixed particle systems with different mass ratios is proposed for the first time. To explore the effect of the particle systems on the receiver performance, a quartz tube falling receiver numerical model is applied. The results indicate that the absorption performance of the particle systems have increased with the addition of dark colored materials, but this effect becomes less obvious with the amount of additive, especially for quartz sand-silicon carbide particle systems. A quartz sand-silicon carbide particle system with a mass ratio of 7:3 may be the optimal choice for high receiver outlet temperature and low mass flow rate. Compared to that of pure silicon carbide particles, this system can achieve a 64.47% reduction in the material cost with only a 4.11% reduction in receiver thermal efficiency. This work provides ideas for the design of multi-component particle systems, which may open a significant development for next-generation concentrated solar power station.

Numerical and experimental investigation on thermal performances of quartz tube gravity-driven solid particle solar receiver based on linear-focused solar furnace

This paper reported a novel quartz tube gravity-driven SPSR. A test platform of the receiver with a drop length of 4 m based on a linear-focused solar furnace was built. The optical performances of the linear-focused solar furnace were measured by a direct method. Solid particles were heated to a temperature of 156∼308°C after a single pass with an averaged irradiance of 14.9∼21.7kW/m2. A three-dimensional mathematical model with the wavelength dependent radiative properties integrated is built and discretized in OpenFOAM, which is later verified by experimental results. Lastly, the influences of several pertinent parameters on thermal performances of the receiver are studied using the proposed model. It was observed that the green-house effect of the quartz tube could reduce the radiative heat losses by a percentage from 2.1% to 9.4%. Wind speed surrounding the quartz tube has a positive effect on the green-house effect since high wind speed is helpful to decrease the outer surface temperature of the tube. An optimal thermal efficiency of 57.2% was obtained when heating particles from 27 °C to 800 °C by circulating particles for four times. The proposed model could be used for the design and optimal operation of the quartz tube gravity-driven SPSR.

Numerical simulation on gas-solid flow characteristics in a high-density countercurrent fluidized bed particle solar receiver

The application of solid particles in the next-generation concentrated solar power station could reduce the Levelized Cost of Energy further. As a key energy conversion device, existing particle solar receivers still have different shortcomings. The high-density countercurrent fluidized bed (CCFB) particle solar receiver may provide a promising technical solution because of its feasibility and its thermal transportation characteristics. However, the hydrodynamics of the CCFB particle solar receiver is very difficult to investigate through experimental methods. In this study, a computational particles fluid dynamics model is established to investigate the gas–solid flow characteristics in the CCFB particle solar receiver, which is validated by the experimental solid mass flow rate obtained from a cold mold CCFB particle solar receiver. The solid holdup distribution, axial particle velocity and characteristics of bubbles are obtained accordingly. The results show that the present model can capture the entire process from bubble formation to bursting. Meanwhile, the solid holdup distribution and axial particle distribution are related to the upward bubbles, both of which present an asymmetrical distribution for the bubble existing region. However, the holdup distributions present a symmetrical distribution similar to the packed bed for the non-bubble region. The results could make up for the deficiency of the experiments effectively and reveal the high-density gas–solid countercurrent flow mechanism comprehensively.

Dynamic simulation and parametric influence analysis on thermal performance of a quartz tube solid particle receiver in solar tower power plants

Due to a higher operating temperature (≥800 °C), Solar Particle Receiver (SPR) which uses particles as the working medium is considered as one of best candidates to improve the thermoelectric conversion efficiency of concentrating solar power plants. In this paper, a quartz tube solid particle receiver model is fully developed by using the discretized lumped parameter method, in which the calculation process of particle temperature and thermal loss is clearly given. In order to improve the manipulation level of particle receiver during the operation, the dynamic characteristics of the quartz tube particle receiver are comprehensively studied by the disturbance test of selected input parameters. Besides, in order to grasp the influence rule of key parameters on the thermal performance of particle receiver, the key parameters’ sensitivity analysis is also deeply studied. The results show that the particle outlet temperature can reach as high as 810 °C under a relatively small value of solar flux 600 kW/m2, but the receiver efficiency is only about 75%; Besides, the receiver efficiency shows a variation tendency that it rises first falls afterwards with the increase of incident solar flux. The validity of proposed model is verified by a heating experimental system with a single quartz tube, and the relative error is not more than 7.9%. The research results are beneficial for understanding the dynamic characteristics and designing the particle receiver.