State building authority confirms: District heating connection conditions can also be met during periods of low consumption
Operators of water heating systems are familiar with the problem: consumption peaks in the morning, after which circulation is the main consumer for many hours. However, it destroys the temperature stratification in the buffer cylinder - it is too cool at the top and too warm at the bottom for optimum operation. Despite the low consumption, recharging is unavoidable in order to ensure hygienic hot water preparation; however, recharging takes place at a very high return temperature to the heat source. This reduces the efficiency of boilers and combined heat and power plants and, in the case of district heating, it is often not possible to comply with the connection conditions.
The influence of hot water circulation is particularly pronounced in hotels or sports facilities. Or, for example, in the accommodation of an educational institution that Dieter Herrmann from the Heidelberg State Building Authority is responsible for. As deputy head of the technology department, he struggled for years with the problem that the district heating return there was often above the required 50 °C.
Effect of the eXergy machine confirmed in comparison
Today, his problem has been solved. For around a year now, a prototype of the „eXergy machine“ (eXm) from varmeco and BMS has been ensuring optimum temperature stratification in the buffer storage tank at the educational facility. A comparison shows how effectively the device works, as there are two almost identical accommodations in the educational facility. Both draw their energy for heating water from district heating; the system in one building works with the eXergy machine, while the system in the neighboring building remains unchanged.
Proven higher temperature spread and fewer charging cycles
Herrmann explains the effect: „The powerful heat pump of the eXergy machine restores the desired temperature stratification in the buffer cylinder, even in pure circulation mode. As a result, we always have high temperatures at the top of the storage tank for hygienic hot water preparation and a sufficiently low temperature at the bottom to serve the district heating station with a return temperature well below 50 °C.“
Return temperature to the district heating station is maintained at all times
The comparison of the buildings shows: The eXergy machine almost halves the number of recharges on working days and reduces the return temperature from an average of 51 °C to approx. 33 °C. At the same time, the eXm raises the flow temperature for providing hot water by around 7K. Herrmann is satisfied: „The eXergie machine works so well that it even compensates for the excessively high return temperature of the neighboring building. This means we can finally comply with the district heating provider's connection conditions at all times, even at weekends when most of the educational institution's visitors are at home.“
