Thermodynamic Performance Analysis of a Low-Cost,Recycled and Energy-Efficient Solar Air Heater with Waste Beverage Cans:An Experimental Research

Solar air heaters are at the centre of interest owing to their widespread use for various purposes.In the study,thermal performance analysis of a solar air heater that can be easily produced from daily waste materials is done.The system has a low-cost structure with both waste material use and a simple design.The proposed system is tested under different climatic conditions,and the energetic and the exergetic performance figures are obtained for the first time in literature.It is observed from the experimental tests that the results are stable and coherent as well as in good accordance with the similar attempts in literature with some cost reductions and performance improvements.Thermodynamic performance analyses indicate that the maximum energy efficiency of the system is about 21%,whereas the exergy efficiency is 1.8%.The energetic and exergetic outputs of the system are also determined to be 27 W and 3 W,respectively,which is promising.

Superionic Conductivity in Ceria‑Based Heterostructure Composites for Low‑Temperature Solid Oxide Fuel Cells

Ceria-based heterostructure composite(CHC)has become a new stream to develop advanced low-temperature(300–600°C)solid oxide fuel cells(LTSOFCs)with excellent power outputs at 1000 mW cm−2 level.The state-ofthe-art ceria–carbonate or ceria–semiconductor heterostructure composites have made the CHC systems significantly contribute to both fundamental and applied science researches of LTSOFCs;however,a deep scientific understanding to achieve excellent fuel cell performance and high superionic conduction is still missing,which may hinder its wide application and commercialization.This review aims to establish a new fundamental strategy for superionic conduction of the CHC materials and relevant LTSOFCs.This involves energy band and built-in-field assisting superionic conduction,highlighting coupling effect among the ionic transfer,band structure and alignment impact.Furthermore,theories of ceria–carbonate,e.g.,space charge and multi-ion conduction,as well as new scientific understanding are discussed and presented for functional CHC materials.

Predicted Oil Recovery Scaling-Law Using Stochastic Gradient Boosting Regression Model

In the process of oil recovery,experiments are usually carried out on core samples to evaluate the recovery of oil,so the numerical data are fitted into a non-dimensional equation called scaling-law.This will be essential for determining the behavior of actual reservoirs.The global non-dimensional time-scale is a parameter for predicting a realistic behavior in the oil field from laboratory data.This non-dimensional universal time parameter depends on a set of primary parameters that inherit the properties of the reservoir fluids and rocks and the injection velocity,which dynamics of the process.One of the practical machine learning(ML)techniques for regression/classification problems is gradient boosting(GB)regression.The GB produces a prediction model as an ensemble of weak prediction models that can be done at each iteration by matching a least-squares base-learner with the current pseudoresiduals.Using a randomization process increases the execution speed and accuracy of GB.Hence in this study,we developed a stochastic regression model of gradient boosting(SGB)to forecast oil recovery.Different nondimensional time-scales have been used to generate data to be used with machine learning techniques.The SGB method has been found to be the best machine learning technique for predicting the non-dimensional time-scale,which depends on oil/rock properties.

Semiconductor Electrochemistry for Clean Energy Conversion and Storage

Semiconductors and the associated methodologies applied to electrochemistry have recently grown as an emerging field in energy materials and technologies.For example,semiconductor membranes and heterostructure fuel cells are new technological trend,which differ from the traditional fuel cell electrochemistry principle employing three basic functional components:anode,electrolyte,and cathode.The electrolyte is key to the device performance by providing an ionic charge flow pathway between the anode and cathode while preventing electron passage.In contrast,semiconductors and derived heterostructures with electron(hole)conducting materials have demonstrated to be much better ionic conductors than the conventional ionic electrolytes.The energy band structure and alignment,band bending and built-in electric field are all important elements in this context to realize the necessary fuel cell functionalities.This review further extends to semiconductor-based electrochemical energy conversion and storage,describing their fundamentals and working principles,with the intention of advancing the understanding of the roles of semiconductors and energy bands in electrochemical devices for energy conversion and storage,as well as applications to meet emerging demands widely involved in energy applications,such as photocatalysis/water splitting devices,batteries and solar cells.This review provides new ideas and new solutions to problems beyond the conventional electrochemistry and presents new interdisciplinary approaches to develop clean energy conversion and storage technologies.

Osmotic Pressure of Water in Nafion~

Mechanical failure modes leading to cracks or breeches in proton exchange membrane fuel cells are driven by mechanical forces associated with swelling from water uptake and shrinkage from dehumidifi- cation. To determine the magnitude of compressive mechanical stress imposed by water swelling in a proton exchange fuel-cell membrane, the osmotic pressure of water in a perfluorosulfonic acid ionomer （Nation N 117） membrane was measured using a hydrostatic piston-cylinder device with an in-situ hydrophilic frit. Experiments indicate that hydrostatic stresses greater than 103.5 MPa are created in a membrane when swollen with water at 23℃ suggesting that pressure from water swelling can distort Nafion N 117-based structures as the osmotic pressure is of the same order of magnitude as the flow stress of Nation N 117.