Investigation of the Influence of Instantaneous Water Heaters on the Efficiency of (Regenerative) Central Heating Systems in the Simulation Environment TRNSYS
Abstract
The use of central instantaneous water heaters enables the use of buffer storage systems for domestic hot water provision. No hygiene requirements need to be observed for buffer storages, so a larger temperature stratification with lower temperatures at the bottom is permissible than for potable water storage tanks. This leads to energy benefits, as the efficiency of temperature-sensitive heat generators such as solar thermal and heat pump systems can be increased by lowering the mean storage temperature. This study examines the influence of instantaneous water heaters on the efficiency of three different (partially) regenerative central heating systems. They are considered large-scale systems and must comply with the relevant regulations in Germany. The results are compared with a reference system with a focus on the CO2 emissions during operation and the associated energy costs. For this purpose, a parameter variability study is conducted using the TRNSYS simulation environment. Instantaneous water heaters with different performance levels, the influence of a return flow distribution using various mechanisms at different actuating times and the influence of the tapping and circulation load were investigated. Furthermore, the storage setpoint temperature was minimized for each combination option.