How a wall thermosyphon can enhance the energy savings in a prefabricated house in Italy

Energy saving in buildings is one of most important issue for European countries. The energy consumption rate devoted to building is about the 40% with respect the total European energy consumption. Although in the last years many studies have been carried out in order to reach the zero-consumption house by means of passive solar heating, ventilation or thermal insulation, the energy rate due to passive solar heating could be further enhanced. This paper proposes a method to increase the energy rate coming from the solar opaque elements by using a two phase loop thermosyphon to connect the internal and the outside façade of prefabricated house wall. The evaporator zone is located on the outside side of the wall and it is irradiated by the sunlight while the condenser zone is placed on the internal side of the wall and releases heat to the domestic environment. The temperature differences between the internal and outside wall facades are lower than 30 K) and the heat fluxes at the evaporator changes during the time range from 2 to 7 x 104 W/m2 K. The thermosyphon has been preliminary designed and implanted into a wall for a prefabricated house in Italy. A thermal model of building with the wall enhanced by the wall thermosyphon has been used to evaluate the impact of this solution in terms of energy saving and thermal comfort in a real prefabricated low consumption house. The transient behavior of the building has been simulated day by day during the winter period by using the EnergyPlusTM software. This solution enhances the thermal comfort of the building by keeping the indoor temperature close to the thermal comfort standard for the most of the day. The annual heating energy demand saving rate is higher than 23% in the case of a low consumption building. These rates reach the maximum of 38.8% in the case of a house