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Li H.,Hebei University of Technology | Zhang H.,Hebei University of Technology | Wang L.,Hebei University of Technology | Wang L.,Shanghai Solar Energy Research Center | And 5 more authors.
Journal of Materials Chemistry | Year: 2012

Herein we demonstrate an alternative route to make Eu 3+- exchanged zeolite L crystals (Eu 3+/ZL) highly luminescent by modification with silylated β-diketone. The modified crystals show strong red emission under UV-light irradiation due to the effective energy transfer from the grafted molecules to the Eu 3+ ions. The obtained materials were characterized with FT-IR, SEM, XRD and elemental analysis. FTIR and elemental analysis confirm that the amount of grafted molecules decreases with increasing size of the ZL crystals. Luminescence spectroscopy was used to study the luminescence properties of the modified Eu 3+/ZL crystals. The formation of europium(iii) diketonate complexes and energy transfer from TTA to Eu 3+ ions have been confirmed by luminescence spectroscopy. The Eu 3+ 5D 0 radiative (k r) probabilities and the 5D 0 quantum efficiency were estimated based on the emission spectra and lifetimes. The studies showed that the luminescence performances of the modified ZL crystals can be significantly affected by the crystal size, e.g., photoluminescence emission intensity, 5D 0 lifetime, 5D 0 radiative (k r) probabilities and the 5D 0 quantum efficiency (q) decreases as the size of the ZL crystals increases. © 2012 The Royal Society of Chemistry. Source

Zhang X.,University of Hull | Zhao X.,University of Hull | Shen J.,University of Hull | Xu J.,Shanghai Pacific Energy Center | Yu X.,Shanghai Solar Energy Research Center
Applied Energy | Year: 2014

Objective of the paper is to present an investigation into the dynamic performance of a novel solar photovoltaic/loop-heat-pipe (PV/LHP) heat pump system for potential use in space heating or hot water generation. The methods used include theoretical computer simulation, experimental verification, analysis and comparison. The fundamental equations governing the transient processes of solar transmission, heat transfer, fluid flow and photovoltaic (PV) power generation were appropriately integrated to address the energy balances occurring in different parts of the system, e.g., glazing cover, PV cells, fin sheet, loop heat pipe, heat pump cycle and water tank. A dedicated computer model was developed to resolve the above grouping equations and consequently predict the system's dynamic performance. An experimental rig was constructed and operated under the real weather conditions for over one week in Shanghai to evaluate the system living performance, which was undertaken by measurement of various operational parameters, e.g., solar radiation, photovoltaic power generation, temperatures and heat pump compressor consumption. On the basis of the first- (energetic) and second- (exergetic) thermodynamic laws, an overall evaluation approach was proposed and applied to conduct both quantitative and qualitative analysis of the PV/LHP module's efficiency, which involved use of the basic thermal performance coefficient (COPth) and the advanced performance coefficient (COPPV/T) of such a system. Moreover, a simple comparison between the PV/LHP heat-pump system and conventional solar/air energy systems was conducted. The research results indicated that under the testing outdoor conditions, the mean daily electrical, thermal and overall energetic and exergetic efficiencies of the PV/LHP module were 9.13%, 39.25%, 48.37% and 15.02% respectively, and the average values of COPth and COPPV/T were 5.51 and 8.71. The PV/LHP module was found to achieve 3-5% higher solar exergetic efficiency than standard PV systems and about 7% higher overall solar energetic efficiency than the independent solar collector. Compared to the conventional solar/air heat pump systems, the PV/LHP heat pump system could achieve a COP figure that is around 1.5-4 times that for the conventional systems. It is concluded that the computer model is able to achieve a reasonable accuracy in predicting the system's dynamic performance. The PV/LHP heat pump system is able to harvest significant amount of solar heat and electricity, thus enabling achieving enhanced solar thermal and electrical efficiencies. All these indicate a positive implication that the proposed system has potential to be developed into a high performance PV/T technology that can contribute to significant fossil fuel energy saving and carbon emission. © 2013 Elsevier Ltd. Source

Zhang X.,De Montfort University | Zhao X.,De Montfort University | Xu J.,Shanghai Pacific Energy Center | Yu X.,Shanghai Solar Energy Research Center
International Journal of Low-Carbon Technologies | Year: 2013

This article presented a theoretical analysis of the heat transfer limits associated with a gravitational loop heat pipe (LHP), which involves the utilization of an innovative liquid feeding/distributing and vapour/liquid-separating structure. The mathematical equations governing the heat transport capacity were applied to simulate several commonly known heat transfer limits of the pipe, namely, viscous, sonic, entrainment, capillary, boiling and liquid filling mass limits. This will allow the determination of the actual figure of the limitation and analyses of the factors effecting the limits, including the loop operational temperature, wick type, evaporator diameter/length, evaporator inclination angle, vapour column diameter in the three-way fitting, liquid filling mass and evaporator-to-condenser height difference. During the study, the heat-transfer limits associated with the three-way fitting for liquid feeding/distribution and vapour/liquid separation were given particular attention. The results derived from the analytical model indicated that the compound screen mesh wick can achieve better thermal performance over the sintered powder and open rectangular groove wicks. It was also found that the heat transport capacity of such LHP operation is positively proportional to the operational temperature, evaporator diameter, evaporator inclination angle, vapour column diameter within the three-way fitting, liquid filling mass and evaporator-to-condenser height difference, and in a reciprocal order to the evaporator length. With the specified loop configuration and operational conditions, the LHP can achieve a high heat transport capacity of around 900 W. Overall, the work presented in this article provided an approach to determine the heat transfer limitations for such a specific LHP operation that will be of practical use for the associated system design and performance evaluation. © The Author 2012. Published by Oxford University Press. All rights reserved. Source

Nian B.,University of Shanghai for Science and Technology | Nian B.,Shanghai Solar Energy Research Center | Fu Z.,University of Shanghai for Science and Technology | Wang L.,University of Shanghai for Science and Technology | Cao X.,University of Shanghai for Science and Technology
2010 6th International Conference on Wireless Communications, Networking and Mobile Computing, WiCOM 2010 | Year: 2010

Image acquisition devices which can get infrared image of solar modules is designed by using the principles of the semiconductor's electroluminescence, andimage processing is applied to the detection system which can detect the defects automatically including black pieces, fragmentation, broken grid, crack and so on. At first the defects of the infrared image are classified and then the defects' types and locations are marked out after filtering, single-chip division, gray-scale transformation, binary, feature description and extraction, finally the results are feeded back to the database. This method increases the defects' types (such as invisible crack) which the manual testing is difficult to identify, it also can eliminate human errors which manual testing may produce possibly and can reduce labor costs, defects' rates, futher it can improve the detection's efficiency and productivity of production line. © 2010 IEEE. Source

Zhang X.,De Montfort University | Zhao X.,De Montfort University | Smith S.,De Montfort University | Xu J.,Shanghai Pacific Energy Center | Yu X.,Shanghai Solar Energy Research Center
Renewable and Sustainable Energy Reviews | Year: 2012

In this paper, the global market potential of solar thermal, photovoltaic (PV) and combined photovoltaic/thermal (PV/T) technologies in current time and near future was discussed. The concept of the PV/T and the theory behind the PV/T operation were briefly introduced, and standards for evaluating technical, economic and environmental performance of the PV/T systems were addressed. A comprehensive literature review into R&D works and practical application of the PV/T technology was illustrated and the review results were critically analysed in terms of PV/T type and research methodology used. The major features, current status, research focuses and existing difficulties/barriers related to the various types of PV/T were identified. The research methods, including theoretical analyses and computer simulation, experimental and combined experimental/theoretical investigation, demonstration and feasibility study, as well as economic and environmental analyses, applied into the PV/T technology were individually discussed, and the achievement and problems remaining in each research method category were described. Finally, opportunities for further work to carry on PV/T study were identified. The review research indicated that air/water-based PV/T systems are the commonly used technologies but their thermal removal effectiveness is lower. Refrigerant/heat-pipe-based PV/Ts, although still in research/laboratory stage, could achieve much higher solar conversion efficiencies over the air/water-based systems. However, these systems were found a few technical challenges in practice which require further resolutions. The review research suggested that further works could be undertaken to (1) develop new feasible, economic and energy efficient PV/T systems; (2) optimise the structural/geometrical configurations of the existing PV/T systems; (3) study long term dynamic performance of the PV/T systems; (4) demonstrate the PV/T systems in real buildings and conduct the feasibility study; and (5) carry on advanced economic and environmental analyses. This review research helps finding the questions remaining in PV/T technology, identify new research topics/directions to further improve the performance of the PV/T, remove the barriers in PV/T practical application, establish the standards/regulations related to PV/T design and installation, and promote its market penetration throughout the world. © 2011 Elsevier Ltd. All rights reserved. Source

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