Polymer Photoelectrodes for Solar Fuel Production: Progress and Challenges

Converting solar energy to fuels has attracted substantial interest over the past decades because it has the potential to sustainably meet the increasing global energy demand. However, achieving this potential requires significant technological advances. Polymer photoelectrodes are composed of earth-abundant elements, e.g. carbon, nitrogen, oxygen, hydrogen, which promise to be more economically sustainable than their inorganic counterparts. Furthermore, the electronic structure of polymer photoelectrodes can be more easily tuned to fit the solar spectrum than inorganic counterparts, promising a feasible practical application. As a fast-moving area, in particular, over the past ten years, we have witnessed an explosion of reports on polymer materials, including photoelectrodes, cocatalysts, device architectures, and fundamental understanding experimentally and theoretically, all of which have been detailed in this review. Furthermore, the prospects of this field are discussed to highlight the future development of polymer photoelectrodes

Research of the Early Warning Analysis of Crop Diseases and Insect Pests

International audienceThe early warning technology of crop diseases and insect pests is a strong guarantee to respond to the increasingly dire situation of major pests and diseases and ensure national food security. At present, the method of the monitoring data collection about the information of diseases and insect pests mainly relies on a field visit carried out by the plant protection staff, sampling and analysis, which directly impacts on the accuracy of early warning analysis. Firstly, the research status of the early warning analysis technology of crop diseases and insect pests in the field of agricultural are investigated and studied thoroughly and deeply, and then the comparison and analysis of the mainstream technology for pest and disease warning and algorithms are done in detail. The final combination of the technology of the Internet of things, a better pest early warning solution of the facility agriculture is put forward in order to provide a useful reference for the study of the early warning of crop pests

Enhanced efficiency in Concentrated Parabolic Solar Collector (CPSC) with a porous absorber tube filled with metal nanoparticle suspension

In this study, effects of different nanoparticles and porosity of absorber tube on the performance of a Concentrating Parabolic Solar Collector (CPSC) were investigated. A section of porous-filled absorber tube was modeled as a semi-circular cavity under the solar radiation which is filled by nanofluids and the governing equations were solved by FlexPDE numerical software. The effect of four physical parameters, nanoparticles type, nanoparticles volume fraction (φ), Darcy number (Da) and Rayleigh number (Ra), on the Nusselt number (Nu) was discussed. It turns out that Cu nanoparticle is the most suitable one for such solar collectors, compared to the commonly used Fe3O4, Al2O3, TiO2. With the increased addition of Cu nanoparticles all the parameters φ, Da and Ra shows a significant increase against the Nu, indicates the enhanced heat transfer in such cases. As a result, low concentration of Cu nanoparticle suspension combined with porous matrix was supposed to be beneficial for the performance enhancement of concentrating parabolic solar collector. Keywords: Concentrating parabolic solar collector, Porous absorber tube, Nanofluid, Nusselt number, Finite Element Metho

Three-dimensional and two-phase nanofluid flow and heat transfer analysis over a stretching infinite solar plate

In this work, 3-D and two-phase nanofluid flow and heat transfer is modeled over a stretching infinite solar plate. The governing equations are presented based on previous studies. The infinite boundary condition and shortcoming of traditional analytical collocation method have been overcome in our study by changing the problem into a finite boundary problem with a new analytical method called optimal collocation method. The accuracy of results is examined by fourth order Runge-Kutta numerical method. Effect of some parameters, Prandtl number, Schmidt number, Brownian motion parameter, thermophoresis parameter, λ=b/a (ratio of the stretching rate along y- to x-directions), and power-law index on the velocities, temperature, and nanoparticles concentration functions are discussed. As an important outcome of our 3-D model analysis, it is found that increase in thermophoretic forces can enhance the thickness of both thermal and nanoparticle volume fraction boundary-layers

Concentrating PV/T Hybrid System for Simultaneous Electricity and Usable Heat Generation: A Review

Photovoltaic (PV) power generation is one of the attractive choices for efficient utilization of solar energy. Considering that the efficiency and cost of PV cells cannot be significantly improved in near future, a relatively cheap concentrator to replace part of the expensive solar cells could be used. The photovoltaic thermal hybrid system (PV/T), combining active cooling with thermal electricity and providing both electricity and usable heat, can enhance the total efficiency of the system with reduced cell area. The effect of nonuniform light distribution and the heat dissipation on the performance of concentrating PV/T was discussed. Total utilization of solar light by spectral beam splitting technology was also introduced. In the last part, we proposed an integrated compound parabolic collector (CPC) plate with low precision solar tracking, ensuring effective collection of solar light with a significantly lowered cost. With the combination of beam splitting of solar spectrum, use of film solar cell, and active liquid cooling, efficient and full spectrum conversion of solar light to electricity and heat, in a low cost way, might be realized. The paper may offer a general guide to those who are interested in the development of low cost concentrating PV/T hybrid system

Numerical heat transfer enhancement using different nanofluids flow through venturi and wavy tubes

In this study, the k-ε turbulence model with enhanced wall function using ANSYS commercial software is used for studying the effect of convergent/divergent sections on the heat transfer of nanofluids in two different cases. In first case, a venturi is modeled with different nanoparticles (SiO2, Al2O3 and CuO) and in second case, a wavy tube with different sinusoidal wall functions (sin(x/2), sin(x) and sin (2x)) is considered. Results of first case revealed that SiO2-water had the most surface Nusselt number among the other nanofluids and outcomes of second case confirmed that when the wave length is smaller (for sin (2x)) the temperatures near the walls increased and consequently the surface Nusselt number in peak areas are greater among other tested wall functions. Keywords: Nanofluid, Wavy tube, Venturi, Numerical modeling, Nussel