Significance of Transient Exergy Terms in a New Tray Design Solar Desalination Device

Abstract

An investigation of the transient exergy property term, exergy storage, for a new desalination tray design was performed. It was illustrated that exergy destruction rates provide a means of comparing alternative energy solutions and a measure of their sustainability. To satisfy these objectives one needs accurate calculation of exergy destruction rates. It was confirmed that neglecting the exergy storage term is not a valid approximation for the hourly and daily averaged values of the second law analysis. For a solar desalination system neglecting the exergy storage terms introduced a maximum difference in the exergy destruction rate of 7.4% and a difference of 7.3% in the daily average. In the solar desalination process with energy recovery the second law performance is greater than that for the reverse osmosis (RO) process, the chief competitor, when the exergy storage terms are correctly included in the analysis. The results demonstrate that for variable energy sources such as renewable energy systems, the second law analysis provides a measure of the sustainability of competing system and that the exergy storage terms should be included in the analysis.