Micro-encapsulated phase change material (MPCM) slurries: characterization and building applications

© 2017 Micro-encapsulated Phase Change Material (MPCM) slurries, acting as the heat transfer fluids or thermal storage mediums, have gained applications in various building thermal energy systems, significantly enhancing their energy efficiency and operational performance. This paper presents a review of research on MPCM slurries and their building applications. The research collects information on the currently available MPCM particles and shells, studies of the physical, structural and thermal stability, and rheological properties of MPCM slurries, and identification/determination of the critical parameters and dimensionless numbers relating to the MPCM slurries’ heat transfer. The research suggests possible approaches for enhancing the heat transfer between a MPCM slurry and its surroundings, while several controversial phenomena and potential causes were also investigated. Furthermore, the research presents mathematical correlations established between different thermal and physical parameters relating to the MPCM slurries, and introduces a number of practical applications of the MPCM slurries in building thermal energy systems. Based on such extensive review and analyses, the research will help in identifying the current status, potential problems in existence, and future directions in research, development and practical application of MPCM slurries. It will also promote the development and application of cost-effective and energy-efficient PCM materials and thus contribute to achieving the UK and international targets in energy saving and carbon emission reductions in the building sector and beyond

Experimental investigation of the energy performance of a novel Micro-encapsulated Phase Change Material (MPCM) slurry based PV/T system

© 2015 Elsevier Ltd. As a follow-on work of the authors' theoretical study, the paper presented an experimental investigation into the energy performance of a novel PV/T thermal and power system employing the Micro-encapsulated Phase Change Material (MPCM) slurry as the working fluid. A prototype PV/T module of 800mm×1600mm×50mm was designed and constructed based on the previous modelling recommendation. The performance of the PV/T module and associated thermal and power system were tested under various solar radiations, slurry Reynolds numbers and MPCM concentrations. It was found that (1) increasing solar radiation led to the increased PV/T module temperature, decreased solar thermal and electrical efficiencies and reduced slurry pressure drop; (2) increasing the slurry Reynolds number led to the increased solar thermal and electrical efficiencies, decreased module temperature, and increased pressure drop; and (3) increasing the MPCM concentration led to the reduced module temperature and increased pressure drop. The experimental results were used to examine the accuracy of the established computer model, giving a derivation scale ranging from 1.1% to 6.1% which is an acceptable error level for general engineering simulation. The recommended operational conditions of the PV/T system were (1) MPCM slurry weight concentration of 10%, (2) slurry Reynolds number of 3000, and (3) solar radiation of 500-700W/m 2 ; at which the system could achieve the net overall solar efficiencies of 80.8-83.9%. To summarise, the MPCM slurry based PV/T thermal and power system is superior to conventional air-sourced heat pump systems (ASHP) and solar assisted heat pump systems (ISAHP), and has the potential to help reduce fossil fuel consumption and carbon emission to the environment

Optical Design of Linear Fresnel Reflector Solar Concentrators

AbstractUsing ray track technology and geometrical analysis, this paper has presented novel design method which can be applied to mirror elements of equal width and varying width, varying height of absorbers of linear Fresnel Reflector Solar Concentrators(LFRSC) whose mirror elements are north-south direction. This paper also discussed the efficiency of mirror elements, it calculated the efficiency every 5°from 30°to 150°and the conclusions gave some parameters with reference value

Experimental investigation of a solar driven direct-expansion heat pump system employing the novel PV/micro-channels-evaporator modules

© 2016 Elsevier Ltd This paper aims to investigate a solar driven direct-expansion heat pump system employing the novel PV/micro-channels-evaporator modules, in terms of its solar thermal, electrical and overall efficiency, as well as coefficient of performance (COP), at the real-time operational condition. This work was undertaken through a dedicated system design, construction, field-testing and performance analysis. It was found that the novel PV/micro-channel-evaporator modules could achieve an average thermal, electrical and overall efficiency of 56.6%, 15.4% and 69.7% respectively at the specified operational condition, while average COP of the system reached 4.7. The innovative feature of the system lied in the structure of the evaporator that was made of the parallel-laid micro-channels. Such a structure created the reduced interior cross-sectional area and thus increased vapor flow velocity within the channels, while the high vapor velocity generated a higher shear stress exerted upon the liquid-vapor interface, leading to the reduced liquid film thickness, increased refrigerant evaporation rate, and increased electrical and heat outputs. The research has provided the fundamental data and experience for developing a highly efficient and practically feasible solar heat pump system applicable to the cold climatic conditions, thus contributing to significant fossil fuel saving and carbon reduction in the global extent

Active Solar Thermal Facades (ASTFs): From concept, application to research questions

© 2015 Elsevier Ltd. All rights reserved. The aim of the paper is to report a comprehensive review into a recently emerging building integrated solar thermal technology, namely, Active Solar Thermal Facades (ASTFs), in terms of concept, classification, standard, performance evaluation, application, as well as research questions. This involves the combined effort of literature review, analysis, extraction, integration, critics, prediction and conclusion. It is indicated that the ASTFs are sort of building envelope elements incorporating the solar collecting devices, thus enabling the dual functions, e.g., space shielding and solar energy collection, to be performed. Based on the function of the building envelopes, the ASTF systems can be generally classified as wall-, window-, balcony-and roof-based types; while the ASTFs could also be classified by the thermal collection typologies, transparency, application, and heat-transfer medium. Currently, existing building and solar collector standards are brought together to evaluate the performance of the ASTFs. The research questions relating to the ASTFs are numerous, but the major points lie in: (1) whole structure and individual components layout, sizing and optimisation; (2) theoretical analysis; (3) experimental measurement; and (4) energy saving, economic and environmental performance assessment. Based on the analysis of the identified research questions, achievements made on each question, and outstanding problems remaining with the ASTFs, further development opportunities on this topic are suggested: (1) development of an integrated database/software enabling both architecture design and engineering performance simulation; (2) real-time measurement of the ASTFs integrated buildings on a long-term scheme; (3) economic and environmental performance assessment and social acceptance analysis; (4) dissemination, marketing and exploitation strategies study. This study helps in identifying the current status, potential problems in existence, future directions in research, development and practical application of the ASTFs technologies in buildings. It will also promote development of renewable energy technology and thus contribute to achieving the UK and international targets in energy saving, renewable energy utilization, and carbon emission reduction in building sector