Multi-criteria optimization of an integrated energy system with thermoelectric generator,parabolic trough solar collector and electrolysis for hydrogen production

In this research paper, a newly energy system consisting of parabolic trough solar collectors (PTSC) field, a thermoelectric generator (TEG), a Rankine cycle and a proton exchange membrane (PEM) is proposed. The integration is performed by establishing a TEG instead of the condenser as power generation and cooling unit thereafter surplus power output of the TEG is transferred to the PEM electrolyzer for hydrogen production. The integrated renewable energy system is comprehensively modeled and influence of the effective parameters is investigated on exergy and economic indicators through the parametric study to better understand the system performance. Engineering equation solver (EES) as a potential engineering tool is used to simulate the system and obtain the desired results. In order to optimize the system, a developed multi-objective genetic algorithm MATLAB code is applied to determine the optimum operating conditions of the system. Obtained results demonstrate that at optimum working condition from exergy viewpoint, exergy efficiency and total cost are 12.76% and 61.69 $/GJ, respectively. Multi-objective optimization results further show that the final optimal point which is well-balanced between exergy efficiency and total cost, has the maximum exergy efficiency of 13.29% and total cost of 63.96 $/GJ, respectively. The corresponding values for exergy efficiency and total cost are 10.01% and 60.21 $/GJ for optimum working condition from economic standpoint. Furthermore, hydrogen production at well-balanced operating condition would be 2.28 kg/h. Eventually, the results indicate that establishing the TEG unit instead of the condenser is a promising method to optimize the performance of the system and reduce total cost.     

Synthesis of hexagonal cobalt hydroxide and cobalt oxide nanorings as promising materials for oxygen evolution and supercapacitive processes

Preparing the low-cost nanomaterials for electrocatalytic processes is still a big challenge. Mesoporous cobalt hydroxide and cobalt oxide nanoparticles were prepared through simple soft chemistry as high-performance materials for durable electrocatalyst for OER and supercapacitive applications. The synthesis method is used to prepare nanoring particles in neither emulsion nor template-directed method. The final nanoparticles display mesoporous hexagonal nanoring morphology. The physio-chemical properties of the as-synthesized nanoparticles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and nitrogen adsorption-desorption techniques. The TEM characterizations prove that NPs retain the topotactical relationship in their structure during the conversion process. The BET measurements prove the mesoporous nature of the nanorings, having good specific surface area and pore volume. Finally, the electrochemical performance toward water splitting and supercapacitor applications were investigated by electrochemical impedance spectroscopy (EIS), linear sweep voltammetry (LSV), and cyclic voltammetry (CV) techniques. The Co₃O₄ NPs exhibits better catalytic properties than Co(OH)₂ NPs when applied as electrocatalyst in an alkaline medium for water splitting and supercapacitor measurements. The enhanced electrocatalytic performance attributed to the mesoporous structure along with high pore volume, which provides more active boundary sites for the electrochemical process, resulted in the enhanced exchange of the intermediates and more efficient electron transfer. This synthetic methodology, with the advantages of inexpensive/non-complicated experimental setup and high electrochemical performance, could shed light on the development of non-expensive electrocatalysts for clean energy production and storage.     

Lead removal from groundwater by granular mixtures of pumice,perlite and lime using permeable reactive barriers

Permeable Reactive Barrier (PRB) is an in situ technology for remediation of contaminated groundwater. This article presents results of studies on three granular mixtures were used for remediation of lead (Pb²⁺) contaminated groundwater using PRBs. The mixtures were composed of pumice, perlite and lime in different proportions. Several column experiments were conducted for evaluation of performance of the mixtures for lead removal. The experiments were carried out for over 50 days to evaluate the long‐term performance of the PRBs. It was found out that pumice‐perlite mixture with a weight proportion of 1 : 1 and pumice‐lime‐perlite mixture with a weight proportion of 2 : 2 : 1 can be used as effective reactive media for lead removal. The removal efficiency of the proposed mixtures was 99.9%. The permeability of the reactive media was relatively constant over 53 days continuous experiments and the results demonstrated that the mentioned mixtures have acceptable performance to maintain hydraulic conductivity of PRBs.     

Effect of footing shape and load eccentricity on behavior of geosynthetic reinforced sand bed

This paper presents the results from a laboratory modeling tests and numerical studies carried out on circular and square footings assuming the same plan area that rests on geosynthetic reinforced sand bed. The effects of the depth of the first and second layers of reinforcement, number of reinforcement layers on bearing capacity of the footings in central and eccentral loadings are investigated. The results indicated that in unreinforced condition, the ultimate bearing capacity is almost equal for both of the footings; but with reinforcing and increasing the number of reinforcement layers the ultimate bearing capacity of circular footing increased in a higher rate compared to square footing in both central and eccentrial loadings. The beneficial effect of a geosynthetic inclusion is largely dependent on the shape of footings. Also, by increasing the number of reinforcement layers, the tilt of circular footing decreased more than square footing. The SR (settlement reduction) of the reinforced condition shows that settlement at ultimate bearing capacity is heavily dependent on load eccentricity and is not significantly different from that for the unreinforced one. Also, close match between the experimental and numerical load-settlement curves and trend lines shown that the modeling approach utilized in this study can be reasonably adapted for reinforced soil applications.     

Case study of a driven pile foundation in diatomaceous soil. II: Pile installation,dynamic analysis,and pore pressure generation

This paper presents the results from a case study highlighting the difficulties of pile driving in diatomaceous soils.In the companion(first)paper to this article,results of an extensive laboratory and in situ testing program were presented while the results from pile driving and further analysis of field observations were presented herein.Unexpected high pile rebound(HPR)was observed during driving of a closed-end pipe pile,with refusal occurring at a depth of less than 5 m.Subsequent open-ended piles were thus driven.Piezometer and case pile wave analysis program(CAPWAP)data were collected during driving of both closed-and open-end piles.Piezometer data indicated that negative pore water pressures(PWPs)were generated while the closed-ended pile exhibited high rebound.Results from in situ tests indicated change in material stiffness and strong dilative tendencies near the depth of refusal.A hypothesis for observed behavior was proposed that considers the soil beneath the pile as a medium with an effectively infinite bulk modulus.     

Stochastic analysis of natural gas consumption in residential and commercial buildings

Consumer consumption characteristic is an important asset for safe design and management of gas distribution networks. Different characteristics of natural gas consumption in residential and commercial buildings are studied from statistical and stochastic points of view. The technique is applied during 2008 and 2009 to a densely populated district in Tehran, Iran, with relatively large number of buildings (67,655 residential and 13,286 commercial buildings). There are different trends in the histograms of gas consumption, but there is a general trend in diagrams of probability index (the probability of gas consumption exceeding a specific value) and their regressions. The most frequent amount of gas consumption for all 45-day periods is 100 m³ as compared with the annual average of 320 m³ for residential buildings. The latter reduces to 80 m³ for the averaged periodic consumption per unit in a building. Also it seems that the most frequent amount of periodic gas consumption of residential buildings is about 31% of their respective annual average during the warm months of the year, and 150% during the cold months. Periodic consumptions less than 1500 m³ and average consumptions less than 1400 m³ are more probable in residential buildings, which are larger than that of commercial ones, but this trend reverses at higher consumption values. If actual consumption is normalized by the average consumption, the number of units in the building or the floor area, the probability index of commercial buildings is generally higher than residential ones. The binomial distribution is analytically used to predict the probability of average gas consumption exceeding 320 and 2000 m³ in two example cases of 500 and 1000 buildings.