Step-by-step methodology of developing a solar reactor for emission-free generation of hydrogen

Özalp, Nesrin; Shilapuram, Vidyasagar

doi:10.1016/j.ijhydene.2010.02.032

Cited by 19 publications

(16 citation statements)

References 52 publications

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“…Radiation from the sun reaching the earth's surface has low flux density of the order of a few hundred watts per square meter. However, once concentrated, it can be used to provide high-temperature process heat necessary for electricity production via solar thermal [2] or for solar thermochemical processing to produce metals [3], syngas [4,5], or hydrogen [6][7][8]. Such high-temperature processes require maintaining a semiconstant temperature for stable efficiency.…”

Section: Introductionmentioning

confidence: 99%

Numerical and Optical Analysis of Solar Power Level Adaptable Solar Reactor

Usman

Özalp

2014

Heat Transfer Engineering

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Solar energy is an abundant renewable energy resource that can be used to provide high process heat necessary to run thermochemical processes for production of various solar fuels and commodities. In a solar reactor, sunlight is concentrated into a receiver through a small opening called the aperture. However, obtaining and maintaining semiconstant high temperatures inside a solar reactor is a challenge. This is because the incident solar radiation can fluctuate depending on the position of the sun and the weather conditions. For fixed aperture size reactors, changes in incident solar flux directly affect the temperature inside the reactor. This paper presents a novel solar reactor with variable aperture mechanism that is designed and manufactured at our lab. Radiation heat transfer analysis of this reactor concept is studied via Monte Carlo (MC) ray tracing. MC ray tracing module is coupled to a steady-state one-dimensional energy equation solver. Energy equation is solved for the wall and gas, accounting for the absorption, emission, and convection. Incoming direct flux values for a typical day are obtained from National Renewable Energy Lab database. Resultsshow that for a perfectly insulated reactor, the average temperature of the working fluid may be kept appreciably constant throughout the day if aperture diameter is varied between 3 cm and 1.5 cm for incoming fluxes starting with 400 W/m 2 at 05:12 a.m., reaching peak value of 981 W/m 2 at noon, and eventually receiving 400 W/m 2 at 6:58 p.m., which can make the solar reactor run about 13 hr continuously at 1500 K semiconstant temperature.

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Section: Introductionmentioning

confidence: 99%

Numerical and Optical Analysis of Solar Power Level Adaptable Solar Reactor

Usman

Özalp

2014

Heat Transfer Engineering

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“…The solution of this equation indicated that the maximum efficiency for the reactor at an operating temperature of about 1200 K will be reached if r opt is 7.2 cm. As for the reactor volume, the methodology given by Ozalp and Shilapuram [20] was followed and reactor geometry was chosen within the range of all hydrogen producing solar reactors described in that reference. From these two results, it was decided that the goal for both geometries is to have equal volumes in the range of 2e3 L, and aperture radii of 7.2 cm.…”

Section: Design Methodologymentioning

confidence: 99%

Effect of reactor geometry on the temperature distribution of hydrogen producing solar reactors

Costandy

Ghazal

Mohamed

et al. 2012

International Journal of Hydrogen Energy

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“…Iterations were made based on CFD simulation results. The first design achieved a cyclone of required characteristics at the required swirling effect, included 6 inlet jets for the main flow [15]. Simulations to identify the best location and the position of these jet ports and natural gas velocity resulted with a gas velocity of 45 deg angle and 6 m/s.…”

Section: Design Of the Solar Cyclone Reactormentioning

confidence: 99%

Computational Fluid Dynamics and Particle Image Velocimetry Characterization of a Solar Cyclone Reactor

Özalp

Chien²,

Morrison

2013

Journal of Solar Energy Engineering

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Solar thermal cracking of methane produces two valuable products, hydrogen gas and solid carbon, both of which can be used as a fuel and as a commodity. During the course of this two-phase phenomenon, carbon particles tend to deposit on the solar reactor window, wall, and exit. When they accumulate at the reactor exit, the agglomeration of these particles completely blocks the exit. This problem has been the major issue preventing solar cracking reactors from running continuously. To address this problem, a cyclone solar reactor was designed to enhance the residence time and allow carbon particles to rotate in the reactor instead of moving towards the exit inlarge particle groups together. A prototype reactor was manufactured to test the concept, to better understand and explain the flow dynamics inside the solar cyclone reactor and to analyze the flow via particle image velocimetry (PIV). Advanced measurement and computational techniques were applied to build the prototype reactor. Computational fluid dynamics (CFD) analysis employing discrete phase model (DPM) was used to predict the particle transport phenomenadel (DPM), whereas PIV was applied for the experimental part of the work. To understand the flow evolution along the vortex line, several images in the axial direction along the vortex line were captured. The results showed that when the main flow was increased by 25%, the axial velocity components became larger. It was also observed that the vertical vortices along the vortex line showed stronger interaction with outward fluid in the core region. This implied that the horizontal twisting motion dominated the region due to the main flow, which could trap the particles in the reactor for a longer time. Furthermore, when the main flow was increased by 50%, the flow displayed a cyclone-dominated structure. During the velocity evolution along the vortex line, more vortices emerged between the wall region and core region, implying that the energy was transferred from order to disorder. In summary, by appropriate selection of parameters, the concept of an aero-shielded solar cyclone reactor can be an attractive option to overcome the problem of carbon particle deposition at the reactor walls and exit.

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Step-by-step methodology of developing a solar reactor for emission-free generation of hydrogen

Cited by 19 publications

References 52 publications

Numerical and Optical Analysis of Solar Power Level Adaptable Solar Reactor

Numerical and Optical Analysis of Solar Power Level Adaptable Solar Reactor

Effect of reactor geometry on the temperature distribution of hydrogen producing solar reactors

Computational Fluid Dynamics and Particle Image Velocimetry Characterization of a Solar Cyclone Reactor

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