Conventional versus storage domestic solar hot water systems: A comparative performance study

This paper presents an experimental comparative performance study between a storage solar domestic hot water system and a conventional one. The storage system differs from the conventional one by integrating the collector and storage tank into one piece of equipment. The investigated storage collector consists of six 80-mm-outside diameter copper tubes connected in series to act as an absorber and a storage tank. Tests under different flow patterns are conducted to simulate different patterns of hot water consumption. The overall heat loss coefficient, useful heat gain, instantaneous efficiency, efficiency factor, heat removal factor and the temperature distribution along the pipe are determined using modified equations derived for the storage collector from the basic derivation of Hottel–Bliss–Whillier. A comparison between the experimental and theoretical results for the storage collector showed good agreements and that between the two systems showed the superiority of the storage system.