Air Receiver Research Articles

Functionally-graded foams for volumetric solar receivers

The open volumetric receiver, one of the most important components of a Concentrated Solar Power (CSP) plant, is made up by a ceramic foam on which the concentrated solar radiation impinges. Ceramic foams are employed in volumetric solar receivers because of their high specific surfaces and their operating temperatures higher than those of metal foams. Thermo- fluid-dynamics in the graded ceramic foam of a volumetric solar air receiver for concentrated solar power is investigated numerically. Variable porosities and Pores Per Inch (PPI), according to different power laws, are accounted for. Governing equations are written with the Volume Averaging Technique (VAT) and are solved with the commercial software Comsol Multiphysics. The effects of different porosity and PPI laws, on the fluid velocity, pressure drop and temperatures, under different thermo-fluid-dynamic conditions, are highlighted.

A novel active volumetric rotating disks solar receiver for concentrated solar power generation

• The complete analysis is composed by a CFD model and its experimental validation. • The experimental results fits with CFD model results. • Thermal performance shows promising results compared to the state of the art. • Next steps in the receiver development will be its upscaling. A new active, first of its kind, volumetric receiver prototype is used in this study to obtain the conclusions about its thermal performance. The rotating disks cooling, was studied first, numerically, using a CFD software and second, experimentally, using a laboratory-scale prototype. This study evaluates the convective heat transfer from rotating disks to a transverse air crossflow. The thermal energy exchange on the disk surfaces allows us to calculate the heat transfer coefficient from disk surface temperature and the thermal performance of the receiver prototype and local Nusselt number through the receiver depth are also a key point in the research. The influence of rotational speed and air mass flow on the heat transfer coefficient is also studied. Differences between numerical and experimental results show high concordance, with a relative error below 15% in the worst point. The thermal performance shown by the lab-scale receiver is promising for the further development of the active Open Volumetric Air Receivers (OVAR) technology. The obtained thermal efficiency results show an improvement of around 10% at 900 °C when compared to the current state of the art of volumetric receivers.

FAILURE ANALYSIS OF ROTARY SCREW COMPRESSOR AND ITS MODIFICATIONS

Abstract -- Screw Compressor is one type of air compressor in the main utility at the DSLNG LNG Plant. This Screw Compressor is used as instrument water (clean, oil-free, and dry air) produced by the Air Compressor Package (Tag No. 065-C-1001 A / B / C), which is dried by the Air Dryer Package (065-V-1001A / B) until it reaches a dew point of -40 degrees Celsius before being accommodated in the Instrument Air Receiver (065-D-1002). Water instruments are needed to operate instrumentation equipment such as actuated valves, control valves, and others.This research was conducted to analyze the failure of rotary screw compressors and their modifications. The failure occurred in the lube oil (lubricating oil), which was contaminated by water from the surrounding wet air. This failure analysis is done with a fishbone diagram and plans to overcome the problem by modifying the breather system. Analysis of this failure by looking for the water content into the lubricating oil. Know the results of the analysis of the increase in the vibration value of the bearing screw elements and check the effect of corrosion in the lubrication system using a borescope. In addition, taking corrective action (repair) so that there are no recurring problems by making modifications to the Breather System on the gear casing

A study on transmission coil parameters of wireless power transfer for electric vehicles

Electric vehicles (EVs) are becoming more popular as people become more concerned about global issues, such as fossil fuel depletion and global warming, which cause severe climate change. Wired charging infrastructure is inefficient because it requires the construction of one charging station for each electric vehicle. As a result, wireless power transfer via magnetic coupling, which is small, compact, and may be placed underground, is a promising technology for the future of charging electric vehicles. One of the disadvantages of wireless power transfer is that efficiency drops rapidly as air gaps grow larger, and it is particularly sensitive to other electrical characteristics such receiver unit capacitance. The purpose of this paper is to investigate the coil parameter, more specifically the outer diameter of wireless power transfer coil effects on the wireless power transfer efficiency at various air gaps and receiver capacitance values for EV applications. The simulations show that a larger outer diameter coil has a better power transfer efficiency at larger air gaps and a more stable range.

Thermoeconomic optimization of a novel high-efficiency combined-cycle hybridization with a solar power tower system

Today, the international community is obligated to utilize renewable energy due to accelerated energy consumption on the one hand and the necessity of environmental pollution reduction, on the other hand. Meanwhile, the Solar Power Tower (SPT) is at significantly optimum conditions for integration with conventional fossil power plants due to reaching temperatures of up to 1200 °C and a high-power generation capacity. The present paper demonstrates the optimal layout of the new hybrid-cycle power generation section with SPT. The Heliostat field was optimized as a transient optical model at all hours of the year by considering the city of Seville as a case study using the System Advisor Model (SAM). Subsequently, the cycle’s thermo-economic model was developed using Engineering Equation Solver (EES) to minimize the Levelized Cost Of Electricity (LCOE). In the following, four fluids of n-Butane, R245fa, n-Pentane, and R123 were utilized for the final analysis as a downstream fluid. Through this process, the appropriate operating fluid was selected. The study results demonstrate an increase in the efficiency of the novel proposed cycle layout compared to a solar power tower power plant with standard pressurized air-fluid; moreover, it reduced fuel consumption, CO2 emission, and LCOE. The maximum efficiency and the minimum LCOE were53.25% and 61.8 $/MWh, respectively. The n-Pentane fluid was recognized as the most appropriate fluid for the downstream cycle. Due to the optimization of solar parts, the number of heliostat field mirrors were 889, with a total area of 131,525 m2 and a central tower height of 105.87 m. The novel presented cycle layout solves a portion of the pressurized air receiver limitations, enabling access to higher efficiency and lower LCOE with the real payback time (RPBT) of 3.876 years, the annual solar share of 23.1%, and reduction of CO2 production by 33,426 ton/year. Consequently, this study’s proposed cycle layout signifies a promising future for using SPT with high efficiency and better environmental and economic conditions.

Influence of the geographical parameters on the performance of hybrid solar gas turbine

This study aims to investigate the influence of the geographical and climate parameters on the performance of the hybrid solar gas turbine with a pressurized air receiver. A number of sites located in South America (Chile, Bolivia, and Peru) and North Africa (Algeria and Libya) are considered. The geometric design parameters of the solar receiver and the tower are calculated using an in-house code. The layout and the optical performance of the heliostat field are carried out using SolarPILOT software. The simulation of the complete hybrid solar gas turbine is carried out using TRNSYS software. A 50 MWe hybrid solar gas turbine is chosen in this study. Results show that a hybrid solar gas turbine installed in North Africa performs better than that installed in South America. This is mainly due to the optical performance of the heliostat field, which are better in North Africa are than in South America. The highest annual optical efficiency of a solar field is observed at Bechar (Algeria) 56.8% while the lowest annual efficiency is observed at Antofagasta (Chile) 48.1%. The solar-to-electric efficiency at Atacama Desert is lower than in the Sahara Desert. Indeed, in Atacama region, the solar-to-electric efficiency varies from 17% at Antofagasta to about 18% in Arequipa while it is above 19% at Sabha and Bechar.

A solar micro gas turbine system combined with steam injection and ORC bottoming cycle

Micro gas turbine (MGT) is an important section in solar-driven power systems, as it can improve system efficiency and provide unique flexibility to meet quickly changing demands. Herein, a solar micro gas turbine (MGT) combined with steam injection and organic Rankine cycle (ORC) is proposed to improve efficiency and flexibility. A steam receiver that produces the steam injected into the MGT is placed around the air receiver aperture to increase the receiver intercept efficiency. A thermodynamic model including a heliostat field, a solar receiver, an MGT and an ORC is developed to investigate the performance of the proposed system, where each sub-model is validated with experimental/referenced data for the subsequence optimization of design and operating parameters. For a 100 kW MGT driven by a solar heliostat field, the simulation results show that the optimized aperture diameter of the air receiver is 1.1 m. On four typical days of a year, i.e. the spring equinox, the summer solstice, the autumn equinox, and the winter solstice, the average optical efficiency of the heliostat field is 0.672, 0.754, 0.672 and 0.597, respectively. Fuel consumption of the MGT during the four days is reduced by 14.8%, 24.6%, 22.4% and 3.7%, respectively. The solar energy share can reach up to 86.0% with a system power efficiency of 19.9% at 12:30 of the autumn equinox. By adding steam injection and ORC, the power output can be increased by 8.29 kW and 30.37 kW, respectively, bringing an increase of the total power output by 37.7% and improving the system efficiency and flexibility. The proposed system can benefit the distributed energy systems especially for remote areas or islands as a flexible option.

Thermo-structural analysis of a honeycomb-type volumetric absorber for concentrated solar power applications

PurposeVolumetric air receivers experience high thermal stress as a consequence of the intense radiation flux they are exposed to when used for heat and/or power generation. This study aims to propose a proper design that is required for the absorber and its holder to ensure efficient heat transfer between the fluid and solid phases and to avoid system failure due to thermal stress.Design/methodology/approachThe design and modeling processes are applied to both the absorber and its holder. A multi-channel explicit geometry design and a discrete model is applied to the absorber to investigate the conjugate heat transfer and thermo-mechanical stress levels present in the steady-state condition. The discrete model is used to calibrate the initial state of the continuum model that is then used to investigate the transient operating states representing cloud-passing events.FindingsThe steady-state results constitute promising findings for operating the system at the desired airflow temperature of 700°C. In addition, we identified regions with high temperatures and high-stress values. Furthermore, the transient state model is capable of capturing the heat transfer and fluid dynamics phenomena, allowing the boundaries to be checked under normal operating conditions.Originality/valueThermal stress analysis of the absorber and the steady/transient-state thermal analysis of the absorber/holder were conducted. Steady-state heat transfer in the explicit model was used to calibrate the initial steady-state of the continuum model.

Open volumetric air receiver: An innovative application and a major challenge

AbstractThe open volumetric air receiver (OVAR) based systems can be used for metals processing operation, such as, the heat treatment of aluminum. Some important aspects, related to the technology adaptation, are (a) the selection of receiver design, (b) the integration of an application, based on hot air, with an OVAR, and (c) mitigation of dust deposition in the porous absorber of an OVAR. Therefore, the presented aspects are (a) literature review on the porous absorbers for OVARs, (b) literature review on solar furnace, and an innovative OVAR‐based solar convective furnace (SCF) for the heat treatment of aluminum, and (c) mechanism of transport and deposition of dust in an absorber pore. These reveal that (a) the design improvements are required, to enhance the thermal efficiency of OVARs, for an input power to air mass flow rate ratio exceeding 900 kJ/kg, (b) the SCF system, based on OVAR, is plausible, and (c) the dust deposition in an absorber pore may be mitigated. The findings will be useful for deployment and operation of the OVAR based systems in arid deserts.This article is categorized under: Solar Heating and Cooling > Science and Materials

Fugitive dust emission control study for a developed smart dry fog system

Air pollution due to dust emission is continuously increasing day by day in mining and allied industrial areas. Mining operations contribute a substantial amount of dust emission at the crushing, screening, and bulk material handling in loading areas. The ambient suspended dust particles create a severe nuisance to workers and local dwellers. For effective controlling of positive dust emission, an innovative automated dry fog dust suppression system (DFDSS) has been developed using hybrid nozzles, sensors, actuators, controllers, screw compressors, air receivers, pumps, motors, and water arrangement with filtration facility. The DFDSS was installed in a crushing and screening plant of an iron ore mine in India. Performance study indicted fugitive dust emission concentration values ranged from 354 to 7040 μg m−3, which was reduced to 91–300 μg m−3 after installation of DFDSS. The reduced values were within the permissible limit of 1200 μg m−3 at a distance of 25 ± 2 m in the predominant downwind direction. The installed DFDSS added a meager addition of moisture content of 0.032% in the handling iron ore material, which was below the acceptable limit of 0.1%. The DFDSS precisely regulated fugitive dust emission from various mining activities without affecting the minerals processing performance. Thus, the DFDSS can be implemented effectively in different mining and allied industries where there is a dust emission problem.

Numerical analysis of a hybrid tubular and cavity air receiver for solar thermal applications

PurposeThis paper aims to deal with characterisation of the thermal performance of a hybrid tubular and cavity solar thermal receiver.Design/methodology/approachThe coupled optical-flow-thermal analysis is carried out on the proposed receiver design. Modelling is performed in two and three dimensions for estimating heat loss by natural convection for an upward-facing cavity. Heat loss obtained in two dimensions by solving coupled continuity, momentum and energy equation inside the cavity domain is compared with the loss obtained using an established Nusselt number correlation for realistic receiver performance prediction.FindingsIt is found that radiation emission from a heated cavity wall to the ambient is the dominant mode of heat loss from the receiver. The findings recommend that fluid flow path must be designed adjacent to the surface exposed to irradiation of concentrated flux to limit conduction heat loss.Research limitations/implicationsOn-sun experimental tests need to be performed to validate the numerical study.Practical implicationsNumerical analysis of receivers provides guidelines for effective and efficient solar thermal receiver design.Social implicationsPressurised air receivers designed from this method can be integrated with Brayton cycles using air or supercritical carbon-dioxide to run a turbine generating electricity using a solar heat source.Originality/valueThe present paper proposes a novel method for coupling the flux map from ray-tracing analysis and using it as a heat flux boundary condition for performing coupled flow and heat transfer analysis. This is achieved using affine transformation implemented using extrusion coupling tool from COMSOL Multiphysics software package. Cavity surface natural convection heat transfer coefficient is obtained locally based on the surface temperature distribution.

Experimental Study of the Convective Heat Transfer and Local Thermal Equilibrium in Ceramic Foam

Foam materials have been widely used in various industrial applications, where higher and higher heat and mass transfer performances are pursued. However, the mechanism of many factors on the heat transfer performances is still unclear. The main purpose of this article is to investigate how the porous properties, porosity, cell size and the sample thickness affect the volumetric convective heat transfer. In this study, the single-blow method is used to determine the volumetric heat transfer coefficient of ceramics foam in the temperature range from 283 K to 323 K. In particular, sensitivity analysis of the foam porosity, cell size, velocity and the sample thickness on the volumetric heat transfer coefficient within the ceramics foam were all conducted. The results indicate that the sample thickness has a significant effect on the volumetric heat transfer coefficient which decreases with the sample thickness. In addition, the local thermal equilibrium phenomenon is verified and its influence on the volumetric heat transfer coefficient discussed. Based on the experimental data, a new correlation is proposed that includes sample thickness, porosity, superficial velocity and fluid properties. This study is crucial to the theory of the convective heat transfer inside the porous media, and can be used to guide the design and optimization of volumetric solar air receivers, compact heat exchangers, heat sinks, heat regenerators, packed bed reactors and so on.

Thermo-economic optimization of an air driven supercritical CO2 Brayton power cycle for concentrating solar power plant with packed bed thermal energy storage

This work presents an innovative indirect supercritical CO2 – air driven concentrated solar power plant with a packed bed thermal energy storage. High supercritical CO2 turbine inlet temperature can be achieved, avoiding the temperature limitations set by the use of solar molten salts as primary heat transfer fluid. The packed bed thermal energy storage enables the decoupling between solar irradiation collection and electricity production, and it grants operational flexibility while enhancing the plant capacity factor. A quasi steady state thermo-economic model of the integrated concentrating solar power plant has been developed. The thermo-economic performance of the proposed plant design has been evaluated via multi-objective optimizations and sensitivity analyses. Results show that a Levelized Cost of Electricity of 100 $/MWhe and a capacity factor higher than 50% can be achieved already at a 10 MWe nominal size. Such limited plant size bounds the capital investment and leads to more bankable and easily installable plants. Results also show that larger plants benefit from economy of scale, with a 65 $/MWhe cost identified for a 50 MWe plant. The receiver efficiency is found to be the most influential assumption. A 20% decrease of receiver efficiency would lead to an increase of more than 15% of the Levelized Cost of Electricity. These results show the potential of indirect supercritical CO2 – air driven concentrated solar power plant and highlight the importance of further air receiver development. More validations and verification tests are needed to ensure the system operation during long lifetime.

On the dust deposition and its effects on heat transfer in absorber pores of an open volumetric air receiver

The deposition of dust in the absorber pores of an open volumetric air receiver (OVAR) offers a significant challenge in arid deserts. In this paper, to address this problem, two aspects are investigated, (i) the transport of an isolated dust particle in a straight, circular absorber pore, for a steady, thermally-hydraulically developing, laminar flow, and (ii) the consequences on heat transfer due to dust particles accumulation, in a straight, circular, absorber pore. The first problem is investigated with a semi-analytical approach and the second problem makes use of computational fluid dynamics simulations. The finding shows (a) a heat flux may be beneficial, for mitigating the dust deposition in a, straight, circular, clean absorber pore, (b) dust deposition in a straight, circular, absorber pore is detrimental to heat transfer, which may lead to its failure, (c) the thermal development length will be reduced for the dust deposited pore in comparison to a clean pore. The findings reveal a way of mitigating dust deposition in a clean pore, and the need for a cleaning strategy of dust deposited absorber pore, for sustainable operation of an open volumetric air receiver.

English

English

One-Dimensional Zonal Model for the Unsteady Heat Transfer Analysis in an Open Volumetric Air Receiver

Abstract The open volumetric air receiver (OVAR)-based central solar thermal systems provide air at a temperature > 1000 K. Such a receiver is comprised of porous absorbers, which are exposed to a high heat-flux > 800 Suns (1 Sun = 1 kW/m2). A reliable assessment of heat transfer in an OVAR is necessary to operate such a receiver under transient conditions. Based on a literature review, the need for developing a comprehensive, unsteady, heat transfer model is realized. In this paper, a seven-equations based, one-dimensional, zonal model is deduced. This includes heat transfer in porous absorber, primary-air, return-air, receiver casing, and their detailed interaction. The zonal model is validated with an inhouse experiment showing its predictive capability, for unsteady and steady conditions, within the reported uncertainty of ±7%. The validated model is used for investigating the effect of operating conditions and absorber geometry on the thermal performance of an absorber. Some of the salient observations are (a) the maximum absorber porosity of 70–90% may be preferred for non-volumetric and volumetric-heating conditions, (b) the minimum air-return ratio should be 0.7, and (c) the smallest gap to absorber-length ratio of 0.2 should suffice. Finally, suggestions are provided for extending the model.

A novel approach for modelling fluid flow and heat transfer in an Open Volumetric Air Receiver using ANSYS-FLUENT

Open volumetric air receiver (OVAR) has great potential as a source of process heat for metals processing operations. The two major components of OVAR are the porous absorbers and the return air flow chamber (RAFC). Heat exchange between the “cooler” return air and the hot curved absorber surface in RAFC is critical as it prevents overheating of absorbers. Unfortunately, modeling of air flow in the RAFC is conspicuous by its absence. Calculations were performed in ANSYS-FLUENT using the local thermal non-equilibrium model for heat transfer in the porous absorber. Three dimensional flow and heat transfer simulations were carried out in the RAFC. Unfortunately, ANSYS decoupled heat exchange between the absorbers and return air by splitting the curved absorber surface into real and imaginary surfaces. Decoupling also meant that heat flux had to be specified separately on the absorber and the RAFC, which was a challenge since only the total input solar flux is known. Hence the major contribution of this paper has been to incorporate two innovations in the simulation methodology. One, to couple the absorber and RAFC thermally by mapping the temperature of the real surface to the imaginary surface. Two, the flux used for heating air in the absorber was calculated iteratively. Limited simulations suggest that in laboratory experiments, relatively inexpensive circumferential (Joule) heating of absorbers can reasonably mimic heating of absorbers by concentrated solar radiation.

Novel hybridization of solar central receiver system with combined cycle power plant

This paper presents a novel hybridization of a solar central receiver system via an open volumetric air receiver with a combined cycle. The exhaust gases from a gas turbine before entering a heat recovery steam generator are heated up by the solar heat in a volumetric receiver working as a supplementary firing, in contrast to the solarized gas turbine where the solar heat is introduced into an open or closed Brayton cycle. This hybridization does not require significant modifications in the gas power block. In this study the thermodynamic and economic issues are investigated and complemented with an optimization to demonstrate its technical feasibility. The obtained results reveal noticeable enhancements in solar energy conversion and power plant performance, where the net solar energy ratio may reach up to 23.5% and the overall efficiency about 64.4%. Assessment of the levelized cost of energy led to an estimated value of 0.0335 $/kWh which could be further reduced through an optimization which when the environmental issue is considered becomes more competitive. Furthermore, there is an important fuel saving of 7.07 Million $ and less pollutant emission about 0.33 Million ton over 30 years of operating service.

Experimental study on the influence of input solar flux, air flow rate, and absorber parameters on honeycomb ceramic air receiver performance

Honeycomb ceramic absorbers are considered to be one of the most practical options for the air receiver of a solar central receiver plant. To explore the influence of the average input solar heat flux, air flow rate, and absorber geometric parameters on the honeycomb ceramic air receiver performance, six samples were tested under different conditions and the outlet air temperature, thermal efficiency, and anti-interference characteristics of the receivers were determined. The investigation showed that as the input solar flux or air flow rate increased, the change in the outlet air temperature and thermal efficiency had opposite trends. The sample with the shortest length, thinnest wall, and highest porosity had the best performance. Among the three absorber geometry parameters, the porosity was the dominant factor affecting the receiver outlet temperature and thermal efficiency.

Simulation-Based Training in Fire Prevention and Fire-Fighting of Scavenge Air Receivers Fires

Abstract This article presents topics concerning fire hazards during the use of low-speed diesel engines in marine vehicles. The causes and effects of fires in the spaces of scavenge air receivers in marine diesel engines are presented. Methods to prevent and fight these fires are shown, including the operating procedures required from ship engine room operators. The possibility of training personnel to apply the abovementioned procedures during operation using simulations of a Kongsberg MC-90 IVship engine room is presented. Simulations were conducted which included a fire in a scavenge air receiver occurring during the operation of a MAN B&W 5L90MC main engine, with loads corresponding to 50% and 100% of the machine’s recommended setting.