A review of solar collectors and thermal energy storage in solar thermal applications

Thermal applications are drawing increasing attention in the solar energy research field, due to their high performance in energy storage density and energy conversion efficiency. In these applications, solar collectors and thermal energy storage systems are the two core components. This paper focuses on the latest developments and advances in solar thermal applications, providing a review of solar collectors and thermal energy storage systems. Various types of solar collectors are reviewed and discussed, including both non-concentrating collectors (low temperature applications) and concentrating collectors (high temperature applications). These are studied in terms of optical optimisation, heat loss reduction, heat recuperation enhancement and different sun-tracking mechanisms. Various types of thermal energy storage systems are also reviewed and discussed, including sensible heat storage, latent heat storage, chemical storage and cascaded storage. They are studied in terms of design criteria, material selection and different heat transfer enhancement technologies. Last but not least, existing and future solar power stations are overviewed.Peer reviewe

Numerical investigations of heat transfer in phase change materials using non-equilibrium model

Phase change materials (PCMs) are drawing increasing attention of researchers nowadays, and they play a pivotal role in thermal energy storage (TES) used in renewable energy resources applications, since these renewable energy, such as solar energy, wind energy and tidal energy, are intermittent and not available at any time. However, most of PCMs suffer from low thermal conductivities prolonging the charging and discharging processes. Metal foams with relatively high thermal conductivities, are believed to be able to enhance heat transfer performance of PCMs for those applications. In this paper, a two-equation non-thermal equilibrium model has been employed to tackle the phase change heat transfer problem in PCMs composites embedded into metal foams. Numerical results show good agreement with experimental data, and indicate that a better heat transfer performance can be achieved by using the metal foams of smaller pore size and smaller porosity, and heat transfer performance of PCMs can be enhanced by up to 10 times by embedded metal foams into PCMs.Peer reviewe

New families of weighted sum formulas for multiple zeta values

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