%0 Journal Article
%K Energy saving
%K Simulation
%K Modelica
%K Active beams
%K HVAC systems
%K Low-energy
%A Alessandro Maccarini
%A Michael Wetter
%A Alireza Afshari
%A Goran Hultmark
%A Niels Bergsoe
%A Anders Vorre
%B Energy and Buildings
%D 2017
%P 234 - 247
%R 10.1016/j.enbuild.2016.10.051
%T Energy saving potential of a two-pipe system for simultaneous heating and cooling of office buildings
%V 134
%8 01/2017
%! Energy and Buildings
%X <p>This paper analyzes the performance of a novel two-pipe system that operates one water loop to simultaneously provide space heating and cooling with a water supply temperature of around 22 °C. To analyze the energy performance of the system, a simulation-based research was conducted. The two-pipe system was modelled using the equation-based Modelica modeling language in Dymola. A typical office building model was considered as the case study. Simulations were run for two construction sets of the building envelope and two conditions related to inter-zone air flows. To calculate energy savings, a conventional four-pipe system was modelled and used for comparison. The conventional system presented two separated water loops for heating and cooling with supply temperatures of 45 °C and 14 °C, respectively. Simulation results showed that the two-pipe system was able to use less energy than the four-pipe system thanks to three effects: useful heat transfer from warm to cold zones, higher free cooling potential and higher efficiency of the heat pump. In particular, the two-pipe system used approximately between 12% and 18% less total annual primary energy than the four-pipe system, depending on the simulation case considered.</p>