Cost-Effective Energy Balancing of Thermal Systems Based on Temperature Measurements Only
Abstract
Usually, thermal systems, especially small solar thermal systems, are not energetically balanced for financial reasons. To overcome this problem, low cost but accurate measuring equipment is required. This paper describes a method to determine the volume flow rate in a pipe and hence the thermal energy transfer through a hydraulic circuit, with the exclusive use of low-cost temperature sensors. Evaluations based on experimentally measured data show, that the method is able to calculate a volume flow rate in a range of 130 and 900 l/h with a deviation of less than ±10% compared to values measured by conventional flow meters or heat meters respectively. The calculated volume flow rate is subsequently used to perform an energy balance of a thermal system. Hereby the heat input and output of the hydraulic circuits into and out of the central hot water store is considered to perform this energy balance. The accuracy of the calculation of the heat quantities varies depending on the type of circuit, e.g. if it is a circuit for space heating or domestic hot water preparation. However, the results on a monthly basis consistently show a deviation of less than ±9% compared to the results of conventional heat meters.