Modeling of a Novel Low-Exergy System for Office Buildings with Modelica

This paper aims to investigate the thermal behavior of a novel low-exergy system for
office buildings. The main characteristic of the system is its ability to provide
simultaneous heating and cooling by operating one water circuit. Inlet water
temperature of about 22 °C is delivered to all the thermal zones in the building, no
matter whether a single zone needs heating or cooling. This approach clearly differs
from conventional systems where simultaneous heating and cooling is provided by
two separated water circuits.
A detailed model of the novel system was developed with Dymola, a modeling and
simulation environment based on the Modelica programming language. The system
was tested on two single office rooms. In order to evaluate potential energy savings,
the energy performance of the novel system was compared with the one of a
conventional system for three typical weeks during winter, spring and summer.
Simulation results showed that the novel system was able to maintain comfortable
levels of indoor air temperature in both rooms for all the three typical weeks. In
addition, the novel system used approximately 35% and 7% less energy than the
conventional system, respectively for the typical winter and spring week. No energy
savings occurred during the summer week.