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Impact of Ground Heat Source Addition on Main Performance Parameters of Solar Chimney Power Plants: A Numerical Study
Full text linkAbstract: Solar energy systems can be an alternative to fossil fuels and are vital for a sustainable environment. It is promising that solar chimney power plants (SCPPs), which are among the solar energy systems, provide 24-hour power output (PO) and can work integrated with other systems. This study is based on the Manzanares pilot plant (MPP) and demonstrates satisfactory performance with an additional heat source to be integrated into the ground of the system during hours when solar radiation is weak. The performance of the system at different source temperatures is compared with the reference case, with the model verified using the RNG k-ε turbulence model through a 3D CFD study. In fact, it is seen that the PO of the system, which yields a PO of around 10 kW at 200 W/m2 solar radiation in the reference case, exceeds 80 kW with a source temperature of 200°C. From the results, it can be noticed that the system can also output power in the evening hours when there is no sun. With an additional heat source of 200°C during non-sunlit hours, the system gives more than 75 kW PO. This PO is 50% more than the maximum PO of 50 kW in the reference case
Diameter-Dependent Shape Memory Effect and Superelasticity in Ni-Mn-Ga Alloy Micro-fibers
Full text linkAbstract: The functional properties of shape memory alloys (SMAs) may be affected by the material size and thus is important for designing micron-sized devices. Here the diameter-dependent size effect was demonstrated in Ni-Mn-Ga fibers with diameters of 15, 41, 53 and 70μm. The effect of fiber diameter on the shape memory effect (SME) and superelasticity (SE) was systematically studied. The results showed that all Ni-Mn-Ga fibers exhibited good stress assisted thermal cycles and SE, both diameter-dependent. For stress assisted thermal cycles, the temperature hysteresis of martensite transformation (MT) and sensitivity of MT temperature vs stress increased with increasing fiber diameter. While for SE, the stress hysteresis, temperature dependence of critical stress and energy dissipation capacity decreased with increasing fiber diameter. Thermodynamic analysis revealed that the diameter-dependent effect may be attributed to the different heat exchange and frictional work dissipation capacities related to the specific surface areas that affected the thermal- or stress-induced MT processes. Such diameter dependence in Ni-Mn-Ga micro-fibers needs to be considered for the design and application in micro-sized devices
Synthesis of Microporous Cobalt Silicate using Organic Template Derived from 2,6-Dimethylpiperidinium Cations: A Potential Precursor for the Preparation of Double Perovskite Cobalt Materials
Full text linkAbstract: Synthesis of a microporous cobalt silicate was achieved by using 6,10-dimethyl-5-azoniaspiro[4, 5] decane bromide as structure directing agent. And physicochemical characterization was carried out using XRD, SEM, HTEM, TGA, FT-IR, BET-N2, ICP-OES and EDS. ETS-10 like structure framework was present as a competitive phase. Calcination of the cobalt silicate at 500 oC leads to a new structure. The possibility of this material be cobalt oxide was excluded since Bragg reflections at 2θ = 19.2º; 30.3º; 36.9º; 43.7º; 59.2º were absent (JCPDS#80-1538). Both the indexation of the XRD data for the calcined material which has resulted in a tetragonal unit cell (a = b = 10.39 Å and c = 12.21 Å, α = β = γ = 90°, V= 1317.4 Å3) and HTEM data indicated the cobalt silicate can be used as a precursor for the preparation of double perovskite cobalt materials
Enhancing the Catalysis for Electrochemical Water Splitting using Tri-metallic Phosphide Surface
Full text linkAbstract: Hydrogen has been considered as one of the sustainable energy carriers and displays great potential for the ever-increasing energy and environmental demands. Electrochemical water splitting has been recognized as a clean and effective method to product hydrogen in future. Transitionally, the catalysts for water splitting are noble metal base materials but suffer from high cost and low reserves. Thus, developing cost-effective electrocatalysts is significantly important for the hydrogen generation. Here, we report a tri-metallic phosphide of NiCoFe-P as an effective electrocatalyst for both HER and OER, which can be prepared by a facile gas-phase reaction. Compared with monometallic or bimetallic phosphides, the tri-metallic NiCoFe-P exhibits outstanding activity. Specially, it obtains an OER current density of 10 mA cm-2 at an overpotential of 248 mV. Additionally, the NiCoFe-P catalyst shows remarkable stabilities even at a large current density of 50 mA cm-2. Moreover, a practical electrode of carbon paper supported NiCoFe-P only requires an overpotential of 267 mV to obtain an HER current density of 10 mA cm-2, and overpotentials of 235 mV and 296 mV for the OER current densities of 50 mA cm-2 and 100 mA cm-2, respectively. After a severe durability test of 5000 cycles of linear scan voltammetry, the carbon paper supported catalyst show no degradation. The remarkable catalytic performance should be due to the unique nanostructure and the synergism effect among the hetero-atoms
Microwave Absorption Performance of One-dimensional Mixed Metal Oxide Nanocomposite
Full text linkAbstract: Microwave-absorbing materials have received numerous attentions in terms of their key roles in the fields of stealth technology and controlling electromagnetic radiation pollution. In this paper, we aim to develop one-dimensional CoFe2O4-TiO2 mixed metal oxide nanocomposite via combination of sol-gel method and electrospinning technique. and investigate its microwave absorbing capability. The phase evolution from precursor fiber to final product and corresponding micromorphology are characterized, and microwave absorption performance for different CoFe2O4-TiO2 composite fibers are investigated with a vector network analyzer in 2-18 GHz. The prepared CoFe2O4-TiO2 mixed metal oxide composite fibers exhibit excellent microwave absorbing ability. The low reflection loss can reach -32.8 dB, and the maximum effective bandwidth is up to 6 GHz (12-18 GHz) at the thickness of 4 mm. The results further reveal that the lightweight mixed metal oxide composite fiber is promising for applications in electromagnetic attenuation and other related research fields
Effect of Turning Angles on the Inflow Characteristics in a Waterjet Propulsion Pump
Full text linkAbstract: To study the influence of turning maneuvering navigation angle on the inflow characteristics of water jet propulsion pumps, numerical simulations were conducted on mixed flow water jet propulsion pumps under straight and left and right 15 °/30 ° turning navigation states. By comparing the hydraulic performance differences of water jet propulsion pumps under five navigation states, the intrinsic relationship between turning angle and pump inflow morphology was elucidated, and the evolution mechanism of pump inflow morphology under straight navigation and turning conditions was emphasized, and conduct quantitative analysis on the inflow quality. The research results of this article provide a theoretical basis for selecting appropriate operating angles for ships under turning maneuvers
Vibro-Acoustic Analysis of an Underwater Cylindrical Shell with Internal Structures and a Comparison with Experiment
Full text linkAbstract: In this work, the low-frequency vibration response and full-band acoustic radiation characteristics of an underwater reinforced cylindrical shell with internal structures are studied by combining the FEM with SEA. The stiffened cylindrical shell contains internal structures such as the F-shape plates and the support valve frames. The exciting sources have two different exciting forces corresponding to two experimental conditions. In the low-frequency band, the FEM was employed, and in the medium and high-frequency bands, the SEA was used. A comparison of the numerical results and the experiment shows that they agree well. The FEM and SEA give better results at [1,1k] Hz and [1k,10k] Hz, respectively. Due to mesh quality limitations, the FEM is not favorable for medium and high-frequency calculations. The SEA focuses on the structural mean power flow but cannot obtain position-specific vibrational responses. The results show that the internal excitation source mainly causes the structural vibration and sound radiation and are closely related to the free vibration characteristics of the structure. In addition, with the increase in frequency, the circumferential sound pressure level of the underwater structure has more substantial directivity
Comparative Performance Analysis of Solar Tracking System Types at Different Latitudes
Full text linkThe increase of solar radiation collected by solar energy convertors is a major challenge in design process of photovoltaic or solar-thermal applications. A valuable approach refers to the use of solar tracking systems that support a large range of tracking performance according to their types, solar tracking algorithm or implementation location. The paper focuses on a comparative study, under the assumption of direct solar radiation only, of solar energy receiving share achieved by four tracking system types and various tracking algorithms used at different latitudes from the northern hemisphere. The simulation results showed a close connection of the tracking system type with the latitude, as well as high performance in collecting the solar energy of dual-axis and single-axis diurnal type tracking with optimized unequal steps
History of Solar Car Technology and its Future Especially in Power Electronics
Full text linkThis paper describes the history and evolution of technologies related to the whole electrical system of solar car [1]. The components are the solar cell, maximum power point tracker, boost converter, motor& Inverter and battery. In a solar car, it is difficult to arrange the solar cells on a flat vehicle surface, and solar cells with different incident angles and temperature is different in each cell. This is a problem when many solar cells with different characteristics are connected in series, and the improvement method will be described in detail. Next, we will explain the development of a boost converter using a GaN power device that can improve the overall running efficiency. We will also discuss the technological advances in motors & inverters and batteries over the last 30 years. The evolution of solar cars is largely due to the evolution of semiconductors, including solar cells, and material technologies, but at the same time, we will explain examples of these technologies being first demonstrated in solar car race and then socially implemente
Recent Advances in the Reutilization of Granite Waste in Various Fields
Full text linkQuarrying and processing of granite produce large amounts of waste residues. Besides being a loss of resources, improper disposal of these wastes results in pollution of the soil, water and air around the dumpsites. The main components of granite waste are quartz, feldspars and a small amount of biotite. Due to its hard and dense texture, high strength, corrosion resistance and wear resistance, granite waste may be recycled into building materials, composite materials and fine ceramics, effectively improving their mechanical properties and durability. By using the flotation process, high value-added products such as potash feldspar and albite may be retrieved from granite waste. Also, granite waste has the potential for application in soil remediation and sewage treatment. This review presents recent advances in granite waste reutilization, and points out the problems associated with its use, and the related countermeasures, indicating the scale of high value-added reutilization of granite waste