Question-and-Answer Resource for the Building Energy Modeling Community
 | 1 | initial version |
I think you are comparing apples with oranges. The top-model is a bi-directional district heating and cooling system with heat pumps and chillers in each building; whereas the bottom-model has only a central chiller and heater. Also, the top-level model is not designed for 70 to 85C water temperatures, but rather a water temperature in the distribution pipes that is near ambient. See for example the paper below and its references for how these systems are designed and operated:
Felix Bünning, Michael Wetter, Marcus Fuchs and Dirk Müller. Bidirectional low temperature district energy systems with agent-based control: Performance comparison and operation optimization. Applied Energy, Vol. 209, p. 502-515. 2017. https://doi.org/10.1016/j.apenergy.2017.10.072
Also available as LBNL Technical Report LBNL-2001090. http://simulationresearch.lbl.gov/wetter/download/LBNL-2001090.pdf
In addition, you should check the model implementations (and their info section) for the assumptions made in these models, as the models are done for conceptual analysis, and not for detailed simulation as you would need if you want to validate a model, possibly against measured data?
