Calibrated simulation of a NZEB: The Solar Decathlon China 2018 SCUTxPoliTo Prototype

Calibrated simulation of a NZEB: The Solar Decathlon China 2018 SCUTxPoliTo Prototype. The aim of this work was to test a fast way to calibrate a Building Energy Model able to perform a dynamic simulation of the behaviour of a single-family house. In particular, the case study was the SCUTxPoliTo prototype and the calibration was done with the scope of refining and enhancing the reliability of the model of the house during the contest conditions and for further energy planning, optimization and last days modification. The performed Calibration relies on the computer aided optimization. The first step was to set up a data collection campaign to monitor the behaviour of the prototype, considering the envelope, the energy systems and the outdoor weather [1]. All of these data will be used for comparison to assess the precision of the BEM [2]. To make the simulation match the real behaviour, a list of parameters have been selected and ranked using a sensitivity analysis procedure. After picking up only the most influential parameters, those have been variated among a pre-selected threshold following a hybrid optimization method (GPSPSOCCHJ) [3]. The main innovation lies in the use of a mathematical based optimization method to maximize the effectiveness of the Calibration, reducing the chance of human errors and allowing to search a wider hyperspace of solutions within a reasonable computational cost. Moreover, the sensitivity analysis, based on the Morris method, has been modified to match the Campolongo [4] optimized pattern search method to highly reduce the possibility of superposition in the variation of Calibration parameters, using at its best the hyper cube generated by the parameters matching [5]. The validity of the study has been proved by both the comparison with ASHRAE 14 guidelines (the BEM is considered fully calibrated) and the real operation [6]. To this last regard, during the SDC18 competition the reliability of the model helped the team to optimize properly the prototype and create a daily energy planning procedure to match energy production and consumption, giving a considerable help to the final score. Due to the superposition of Building phase and part of measurements campaign the calibration has been divided into two different steps: the first to be performed on the envelope, the second on the systems. The former focus on the air tightness, thermal transmittance and glazing characteristic, the latter on set points, real efficiency and schedule of the HVAC system. The results showed how the air infiltrations were underestimated, that the thermal transmittance of the main insulant was set to a higher value than the operational one and other minor change in the selected parameters. For what it may concern the systems, the main tuning regarded the set point of the HVAC (due to an error in the placing of the thermostats of the VRVs) and on the schedule of the ventilation system.