NZEB, ground-water heat pump, desuperheater, monitoring, Passive House
Two new, residential, and high performance buildings were constructed according to Passive House standard in Innsbruck, Austria (with cold winters and mild summers). The two multi-family houses consist of 26 apartments - 16 in the north and 10 in the south building. The goal of the project was to achieve net zero energy building (NZEB) standard, which was defined in this project as the annual balance between the electricity consumed for heating and ventilation (excluding household appliances), and the electricity produced by renewable sources. Thus, a heat pump, solar thermal collectors, photovoltaics (PV) and ventilation units were installed. The two stage ground water source heat pump with a power of 58 kW (at W10/W35) includes desuperheater. The available roof space of the north building was covered by a solar thermal system with 74 m2 and PV with 52.5 m2 (8.5 kWp). An additional PV system of 99.8 m2 (16 kWp) was placed in the roof of the south building. The ventilation units were centralized (three in total) including heat recovery. In combination with floor heating and a heat exchanger in each flat for domestic hot water (DHW), a four pipe distribution system was used to minimize the distribution losses; two pipes for the DHW (flow temperature of 52°C) and two pipes for the space heating (with flow temperature of 35°C). Therefore, stratification was obtained in the 6000 liter storage to improve energy performance, since the heat pump can operate at a low sink temperature for supplying space heating. A detailed monitoring system was installed consisting of 58 temperature sensors, 12 humidity sensors, 2 pressure sensors, 37 signals (e.g. controllers, valves, pumps, etc.), 22 heat meters, 7 electricity meters, and 2 volume flow meters. The main focus was the energy performance of the HVAC systems. The thermal comfort of the south building was monitored, too. The operation of a monitoring system has started in November 2015. In this paper, results of monitoring of three heating seasons are highlighted and discussed. The energy performance of the technical system and each subsystem is presented in detail. The performance of the heat pump with respect to the two compressors and the desuperheater is in the focus. Supplementary to the monitoring data, simulations were performed aiming to optimize the system, and support the monitoring results. In addition, the importance of quality assurance control e.g. with monitoring is highlighted. The present study enhances the discussion about evaluation of NZEBs with a monitoring example from central Europe, and contributes to improve the knowledge with respect to the use of desuperheater in a heat pump via a comprehensive analysis.