A Solar Central Hot Water System with Auxiliary Absorption Heat Transformer

Abstract

All-glass evacuated collector tube is a widely used facility to supply313–318K hot water by solar energy. However, this relatively cheap solar system needs major improvements to meet the actual demands: i) to provide standard 328–333K domestic hot water supply, and ii) to supply required hot water steadily even in night or bad weather. An auxiliary absorption heat transformer is combined with the evacuated collector tube using solar energy as the primary energy source. Owing to the considerations for environmental protection, lithium bromide/water is used as the working fluid in the absorption heat transformer. The unsteady low-temperature hot water from the evacuated collector tube flows to the absorption heat transformer, which finally provides 328–333K water. The thermodynamic properties of the new solar central hot water system, such as COP, ECOP, circulation ratio, etc., are analyzed and simulated. Exergy analysis is also applied to the solar system to evaluate non-dimensional exergy loss of each component. Analysis reveals that optimal COP and the temperature of the supply water are subject to several key system parameters and variations of working conditions. These results help to improve the solar central hot water system to provide steady outputs that can satisfy the 328–333K domestic hot water supply standard.