1,721,018 research outputs found
Effect of solar collector type on the absorption system performance
No full textSolar energy has a great ability in cooling and air conditioning as the demand coincides with the availability of solar energy. In this study, different solar collector technologies such as Parabolic Trough Concentrator PTC and Linear Fresnel Collector LFC were used to power solar absorption system. The effect of using these different technologies on the thermal performance of the absorption cooling system was investigated. The PTC proved better performance compared to the Linear Fresnel Collector in terms of outlet fluid temperature, temperature rise and rate of energy gained. The result shows an enhancement in the outlet temperature, temperature rise and the rate of energy gained due to use the parabolic trough collector by about 47 °C, 6 °C and 161 kW, respectively. Also, the operating period due to using the parabolic tough collector is longer relative to the linear Fresnel collector. The result shows that an operating period of about 71.5 and 63. 75 h/week was satisfied for the PTC and LFC, respectively. This study was performed using TRNSYS program. © 2017 IEEE
Sulphur based thermochemical cycles: Development and assessment of key components of the process
No full textHycycleS was a cooperation of nine European partners and further non-European partners and aimed at the qualification and enhancement of materials and components for key steps of solar and nuclear powered thermochemical cycles for hydrogen generation from water. The focus of HycycleS was the decomposition of sulphuric acid (H2SO4) which is the central step of the sulphur-based family of those processes. Emphasis was put on materials and components for H2SO4 evaporation, decomposition, and sulphur dioxide separation. The suitability of materials and components was demonstrated by decomposing H2SO4 and separating its decomposition products in scalable prototypes. Silicon Carbide (SiC) turned out as the material of choice for the components facing the most corrosive environment of the process: the sulphuric acid evaporator and decomposer. Candidate catalysts for the high temperature reduction of sulphur trioxide have been screened and analysed. Cr-Fe mixed oxide (Fe 0.7Cr1.3O3) was the most promising material among the ones examined. Based on the use of the highlighted construction and catalyst materials prototype decomposers have been developed and tested. The successful fabrication and testing of a large size heat exchanger/reactor prototype composed of SiC plates shows promise with respect to its use for H2SO4 decomposition in the SI and HyS cycle. A solar specific decomposer prototype was developed, realised and successfully tested on sun in a solar furnace. A novel approach of using dense oxygen transport membranes, made from complex ceramics, for oxygen removal from the H 2SO4 decomposition product in order to shift the equilibrium in favour of increased decomposition was investigated. The membranes stability and suitability for carrying out this separation was investigated experimentally. Parallel to this, a conventional oxygen separator, a low-temperature wet scrubbing system, was investigated as well. Scale-up scenarios of components and of the process were addressed. Copyright © 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved
Annual simulation of the thermal performance of solar power plant for electricity production using TRNSYS
No full textThe process of generating electricity using solar energy took a great interest in the recent period for its contribution to the reduction of the fossil fuel consumption and the harmful emissions to the environment. The main task of this article is to simulate the thermal performance of a solar power plant for electricity production using a parabolic trough concentrator for accumulating the solar heat. The plant includes a stratified storage tank, steam generator, steam turbine and an electric generator. The simulation studies the effect of the design parameters of the solar field and the storage tank on the annual performance of a 1 MWe solar electric power plant. The simulation platform TRNSYS was used to model the solar power plant including the solar concentrator field, the storage tank, and the steam generator. The simulation predicts the instantaneous and annual heat energy collected by the solar concentrator and the heat energy rate supplied, extracted, and stored in the storage tank. It predicts also the rate and the quality of the steam produced. This analysis was applied to four sites in Egypt to study the effect of the solar radiation on the energy produced in those sites. © Copyright 2016 by ASME
Hydrogen Production by Solar Steam Reforming as a Fuel Decarbonization Route
No full textThis chapter describes the hydrogen production by solar-powered steam reforming. This process allows some upgrading of the reformed fuel (in terms of heat value and environmental impact) and significant reduction (40-50 %) in CO2 emission to the atmosphere, with respect to the conventional steam reforming process. Additionally, solar steam reforming is presented as an emission-free process: the only carbon-containing by-product stream is well suited for the application of CCS technologies, and the overall process can also be considered as a "fuel pre-combustion decarbonization route". Application of pressurized membrane reactors for low-temperature steam reforming improves the overall process efficiency and enhances the recovery of CO2 thanks to its relatively high partial pressure in the by-product stream. The application of SERP technology for in situ CO2 separation is discussed too. © Springer-Verlag London 2013
Robust Mesoporous CoMo/γ-Al2O3 Catalysts from Cyclodextrin-Based Supramolecular Assemblies for Hydrothermal Processing of Microalgae: Effect of the Preparation Method
No full textHydrothermal liquefaction (HTL) is a promising technology for the production of biocrude oil from microalgae. Although this catalyst-free technology is efficient under high-temperature and high-pressure conditions, the biocrude yield and quality can be further improved by using heterogeneous catalysts. The design of robust catalysts that preserve their performance under hydrothermal conditions will be therefore very important in the development of biorefinery technologies. In this work, we describe two different synthetic routes (i.e., impregnation and cyclodextrin-assisted one-pot colloidal approach), for the preparation in aqueous phase of six high surface area CoMo/γ-Al2O3 catalysts. Catalytic tests performed on the HTL of Nannochloropsis gaditana microalga indicate that solids prepared by the one-pot colloidal approach show higher hydrothermal stability and enhanced biocrude yield with respect to the catalyst-free test. The positive effect of the substitution of the block copolymer Tetronic T90R4 for Pluronic F127 in the preparation procedure was evidenced by diffuse reflectance UV-visible spectroscopy, X-ray diffraction, N2-adsorption-desorption, and H2-temperature-programmed reduction measurements and confirmed by the higher quality of the obtained biocrude, which exhibited lower oxygen content and higher-energy recovery equal to 62.5% of the initial biomass. © 2018 American Chemical Society
Legge elettorale e referendum: l'esito non cancella i dubbi sulla coerenza del quesito e sulla costituzionalità della normativa di risulta
No full textLow temperature methane steam reforming: Catalytic activity and coke deposition study
No full textLow temperature steam reforming combined with hydrogen-selective membrane offers significant advantages in terms of energy conservation, reduction of GHG emissions and low cost operation. In this study, Ni supported on La/CeO 2-ZrO2 is evaluated under steam reforming at temperature <550 °C. The catalyst is highly active in steam reforming of methane and water gas shift reaction. Stability test at simulated biogas steam reforming was conducted and the catalyst showed extremely stable performance for long time on stream (90 h) and very low amount of carbonaceous deposits, as determined by TPO and TPH. The above characteristics demonstrate that this catalyst is a potential candidate for use in membrane reactors operating at low temperature for the one-step production of pure hydrogen. Copyright © 2013, AIDIC Servizi S.r.l
Thermal fluids for CSP systems: Alkaline nitrates/nitrites thermodynamics modelling method
No full textMolten salt (MS) mixtures are used for the transport (HTF-heat transfer fluid) and storage of heat (HSM-heat storage material) in Concentration Solar Plants (CSP). In general, alkaline and earth-alkaline nitrate/nitrite mixtures are employed. Along with its upper stability temperature, the melting point (liquidus point) of a MS mixture is one of the main parameters which defines its usefulness as a HTF and HSM medium. As a result, we would like to develop a predictive model which will allow us to forecast freezing points for different MS mixture compositions; thus circumventing the need to determine experimentally the phase diagram for each MS mixture. To model ternary/quaternary phase diagram, parameters for the binary subsystems are to be determined, which is the purpose of the concerned work. In a binary system with components A and B, in phase equilibrium conditions (e.g. liquid and solid) the chemical potentials (partial molar Gibbs energy) for each component in each phase are equal. For an ideal solution it is possible to calculate the mixing (A+B) Gibbs energy:ΔG = ΔH - TΔS = RT(xAlnxA + xBlnxB) In case of non-ideal solid/liquid mixtures, such as the nitrates/nitrites compositions investigated in this work, the actual value will differ from the ideal one by an amount defined as the "mixing" (mix) Gibbs free energy. If the resulting mixtures is assumed, as indicated in the previous literature, to follow a "regular solution" model, where all the non-ideality is considered included in the enthalpy of mixing value and considering, for instance, the A component: ΔG0=(ΔHA-TΔSA)+(ΔHmixAL-TΔSmixAL)-(ΔHmixAS-TΔSmixAS) where the molar partial amounts can be calculated from the total value by the Gibbs Duhem equation: (ΔHmixAL=ΔHmix-XBLdΔHmixdXBL)L;(ΔHmixAS=ΔHmix-XBSdΔHmixdXBS)S and, in general, it is possible to express the mixing enthalpy for solids and liquids as a function of the mol fraction: ΔHLmix=XALXBL(a1+b1XAL+c1XALXBL),ΔHSmix=XASXBS(a2+b2XAS+c2XASXBS) From the latter expressions it can be possible to modelize the phase diagram of a binary mixtures by using the a,b and c couples of parameters. To calculate those coefficients a method commonly employed in literature is to measure the mixing enthalpies, or to use one reported of the enthalpy of mixing (for instance for the liquid state) and calculate the other one using the phase diagram points. A direct ΔHmix (in solid or liquid phase) measurement can be difficult to carry out using common DSC equipment generally present in research laboratories. In fact, such determinations can be, in principle, performed, but the obtained data will be affected by large experimental errors. On the other hand, it is possible to obtain values with great precision regarding the algebraic sum of mixing enthalpies and the phase diagram trend. For this reason, only the phase diagrams are proposed to be used to calculate a, b, c parameters, and, subsequently, the total (liquid-solid algebraic sum) enthalpy of mixing will be employed to verify their validity. At this aim, a C++ code was assessed and used. Three binary mixtures were considered by combining NaNO3, KNO3 and NaNO2. © 2016 Author(s)
Co-generation and innovative heat storage systems in small-medium CSP plants for distributed energy production
No full textCSP technologies can be applied for distributed energy production, on small-medium plants (on the 1 MW scale), to satisfy the needs of local communities, buildings and districts. In this perspective, reliable, low-cost, and flexible small/medium multi-generative CSP plants should be developed. Four pilot plants have been built in four Mediterranean countries (Cyprus, Egypt, Jordan, and Italy) to demonstrate the approach. In this paper, the plant built in Italy is presented, with specific innovations applied in the linear Fresnel collector design and the Thermal Energy Storage (TES) system, based on a single the use of molten salts but specifically tailored for small scale plants. © 2017 Author(s)
Conceptual study of the coupling of a biorefinery process for hydrothermal liquefaction of microalgae with a concentrating solar power plant
No full textA conceptual analysis of the coupling of a concentrating solar power plant with a chemical process for hydrothermal liquefaction (HTL) of microalgae to biocrude was performed. The two plants were considered coupled by molten salt recirculation that granted energetic supply to the chemical process. Preliminary estimations have been done considering a solar field constituted by 3 linear parabolic solar collectors rows, each 200 m long, using a ternary molten salts mixture as heat transfer fluid, and a chemical plant sized to process 10 kT/y of microalgae. Under adopted conditions, we have estimated a minimum selling prize of the biocrude that is similar to that achieved in non-solar HTL processes. © 2017 Author(s)
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