Calibration applied to a building thermal facility. Methods for data treatment and thermal model building

Resumen

A hybrid thermal facility, located in Biscay (Spain), supplies the domestic hot water (DHW) and the heating demand of 26 social housing units. The facility consists of a 68 [kW] heat pump (HP), connected to a very low enthalpy geothermal well, and a 120 [kW] gas boiler. A SCADA system, stores the data acquired from the measuring devices in different time intervals, format and unit system. A system thermal model is build, based on the technical information of the facility, with TRNSYS V17, a software for dynamic energy system simulation. Accordingly, additional data that is not obtained from the SCADA was generated with TRNSYS. This model simulates the energy performance of the facility along a year. This step is required for further rigorous studies of its energy performance. In order to achieve this aim, the model must be validated with a validation criterion such as the one indicated in the ASHRAE guideline, 14th standard. To start the validation, the information stored in SCADA has being analyzed. Therefore, data related to a period in summer (15 May-14 October) and in winter (15 October-14 May), were selected from the SCADA and the following data was used: resource consumption data (gas consumption in the boiler and electricity in the HP) and heat values in the circuits. Gas and electricity meters are record every 15 minutes in the SCADA, while heat values are stored every 24 hours. Later on, a graphical method has being used to compare the records in both databases. Accordingly, a gap appears between simulated and measured records. That indicates, precisely, the level of uncertainty in the model and, in order to reduce it, a calibration process has being applied. Consequently, the original gap between real data and model data has being reduced. Therefore, the performance of the model appears now closer to the real facility. Nevertheless, the calibration of the installation should be improved with much more expensive methods to achieve the final objective, of validating the installation according to standard 14th. Because of that, a proper model of the system is a strict requirement to achieve energy savings in buildings thermal systems.