Comparative study of various CESI optimization criteria and proposition of a globalevaluation approach

This study compares various optimization criteria for a solar domestic hot water system (SDHWS). First of all, we present the various parameters used to evaluate a SDHWS. We consider the energetic, exergetic, environmentaland financial analysis. Various optimization criteria of a standard solar hot water system are then proposed. The optimized solutions are compared with a standard hot water system. The most suitable criteria take into account both energetic and financial evaluations.The most powerful solutions tend to increase the collector area (increasing the solar fraction during the mid-season) and reduce the tank volume (decreasing the thermal losses and financial cost).Some of the usual evaluation criteria for SDHWs cannotbe used as optimization criteria because they do not consider the auxiliary heater, resulting in inaccurate indications of the systems performance. Therefore, it seemed important to propose a new evaluation method which integrates the financial savings (LCS), energetic savings (primary) and CO2 emission savings (environmental)with regard to a referenced solution based on a radar diagram. This mode of representation is particularly interesting when various auxiliary heaters are compared.