Impact of different internal convection control strategies in a non-evacuated CPC collector performance
Impact of different internal convection control strategies in a non-evacuated CPC collector performance
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DOI：
10.1016/j.solener.2012.01.016
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发表时间：
2012-05
期刊：
影响因子：
6.7
通讯作者：
P. Horta;J. Henriques;M. Collares-Pereira
中科院分区：
文献类型：
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作者：
P. Horta;J. Henriques;M. Collares-Pereira
在过去十年中，在太阳能集热器材料中观察到的技术进步，即更好的光谱选择性吸收涂层和超透明玻璃盖，有助于性能改进，并转化为更高的工作温度范围和更高的效率值。虽然真空管集热器（ETC）的使用在太阳能的热转换中变得越来越普遍，但非真空太阳能集热器在制造、可靠性和/或成本水平方面仍然具有优势，这使得它们对于大范围的应用（特别是在高达80°C的温度范围内）具有吸引力和竞争力。然而，与ETC相比，这些优点并没有阻止这些收集器的主要缺点：由于内部对流导致的热损失，这阻止了它们在高达150°C的工作温度范围内的一般使用。绝缘、双层玻璃或选择性涂层可用于非真空集热器，以减少热损失。为了防止这些太阳能集热器中的内部对流损失，已经研究了不同的控制策略，例如在集热器腔内采用不同的惰性气体，降低吸收器或盖表面上的空气流速的物理屏障，或者使用集中。在本文中，采用这种内部对流控制策略的CPC收集器的评估。所提出的每一种策略进行评估，在所得到的收集器的光学和热特性参数和每年的收集器产量。为此，开发了一种集成工具，允许CPC收集器的设计，光学和热特性。所获得的结果提供了有价值的指导方针，任何人都希望实现这些策略中的任何一个新的收集器设计。
Over the last decade the technological advances observed in solar collector materials, namely better spectrally selective absorber coatings and ultra clear glass covers, contribute to performance improvements and translate into higher operational temperature ranges with higher efficiency values. While the use of Evacuated Tube Collectors (ETCs) is becoming widespread in the thermal conversion of solar energy, non-evacuated solar collectors still hold advantages at manufacturing, reliability and/or cost levels, making them interesting and competitive for a large range of applications, in particularly, in temperature ranges up to 80°C. However, these advantages have not prevented the major drawback of these collectors when compared to ETCs: thermal losses due to internal convection which prevent their general use in the range of operating temperatures up to 150°C. Insulation, double glazing or selective coatings can be used in non-evacuated collectors to reduce heat losses. To prevent internal convection losses in these solar collectors, different control strategies have been studied, such as the adoption of different inert gases within the collector cavity, physical barriers reducing air flow velocities over the absorber or cover surfaces or the use of concentration. In the present article, an assessment of adopting such internal convection control strategies in a CPC collector is presented. Each of the presented strategies is assessed in terms of the resulting collector optical and thermal characterization parameters and yearly collector yield. For this purpose, an integrated tool allowing the design, optical and thermal characterization of CPC collectors was developed. The results obtained provide valuable guidelines for anyone wishing to implement any of these strategies in a new collector design.