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Focuses on a study which investigated the influence of domestic hot water (DHW) load profiles with a constant total yearly heat demand for a solar combisystem. Realistic load profiles for DHW; Definition of the fraction energy savings; Relations of the thermosyphon loop; Distribution of the solar energy gain.

To reach the goal of decarbonizing energy systems, newly constructed buildings must adhere to higher efficiency standards. In new residential developments, this results in a higher share and significance of the energy demand for domestic hot water preparation. In order to generate realistic load profiles for domestic hot water preparation, which can help with dimensioning district heating systems, four substation types were modeled in TRNSYS. Two instantaneous and two storage systems were considered for single family and multi family houses. 11 fictitious buildings were defined, for which the systems were dimensioned. Yearly simulations were conducted, using DHWcalc draw-off profiles as input. The impact of domestic hot water preparation system design on energy balances, return temperatures and simultaneity factors was investigated. Distribution heat losses amount to approximately the same energy demand as the useful energy demand for domestic hot water. In single family houses, storage heat losses also account for a significant energy demand, but in larger multi family houses the storage heat losses are negligible. The yearly weighted average return temperatures of the investigated buildings vary from 25 to 54 °C. Instantaneous DHW preparation result in 8–9 K lower return temperatures for the district heating system than storage systems. An important influencing factor on the return temperature is the relation of energy used by the circulation system to the useful energy demand, resulting in lower return temperatures in more densely inhabited buildings. Load duration curves for superposed profiles were calculated and compared to literature values. The results show, that DHWcalc draw-off profiles provide a suitable basis with realistic simultaneity for district heating load profiles. It is shown, that the time interval for which simultaneity factors are calculated must always be considered. Also, the importance of the underlying probability distributions for draw-off profiles was shown by comparing different approaches. • Dynamic simulations of different DHW preparation systems in TRNSYS. • Generation of DH load profiles for DHW for instantaneous and storage systems. • Instantaneous DHW systems yield lower return temperatures than storage systems. • Simultaneity factors were calculated for different systems and time scales. • Time scale and probability distributions for DHW draw-offs influence peak loads. [ABSTRACT FROM AUTHOR]

Heat load profiles of new residential developments in rural, sub-urban, and urban context were generated by means of a generic model and dynamic simulations. The combined effect of district building density, building energy efficiency standard, and hot water preparation system on the heat load is discussed in detail. Hundred residential districts representing medium sized developments were defined by varying the distribution of building types. Therefore, a simplified building typology of 13 fictitious buildings was developed. The presented methodology allows to quickly estimate the total heat demand of new residential developments based on the plot ratio and buildings' energy efficiency standard only. The investigations reveal that the building density as well as the hot water preparation system have a significant impact on the yearly district heating return temperatures. Instantaneous domestic hot water preparation results in up to 14 K lower annual average district heating return temperatures. However, the building density also has a significant influence on the return temperature, resulting in important differences between urban and rural districts. • Heat load profiles of rural, sub-urban, and urban districts were generated. • The German energy efficiency standards for new buildings were considered. • The impact of building systems engineering on the return temperature was assessed. • Instantaneous DHW preparation achieves significant lower DH return temperatures. • Districts of plot ratio greater than 0.3 show beneficial linear heat densities. [ABSTRACT FROM AUTHOR]