AS_03_2020

tecnica 91 Automazione e Strumentazione Aprile 2020 CONTROLLO Building 25 , located in the university campus ‘Leonardo’ . This academic building is composed by 14 classrooms over 4 floors. A centralized thermal network composed by different thermal devi- ces guarantees the control over each room temperature, humidity and CO2 levels. Each room is equipped with an air recirculation system and a fan coil system . The fan coil system is dedicated to the room temperature control, while the air recirculation system is dedicated to the humidity and CO2 control. 2.1 Thermal network The analysed building is overall subjected to a massive distur- bance coming from the intensive people occupancy profile. In fact, the people flow highly affects many variables related to the people comfort requirements, such as the air temperature, humi- dity and CO2 levels. For this reason, a specific complex thermal network has been deployed to correctly compensate any disturbance and guarantee a cor- rect user comfort. However, although the overall thermal network has been sized according to the expected distur- bances caused by the impact of people occupancy, the control architecture reflects a classic strategy that does not consider people occupancy impact. For this reason, advanced control strategies able to effectively integrate the people occupancy disturbance are presented in this paper, resulting in higher user comfort levels and lower energy consumption. A simplified block diagram structure describing the overall thermal generation network has been obtained by studying the building data sheets and is presented in υ figure 1 . The presented thermal network is meant to feed three different circuits. The fan coils circuit is fed with a controlled tempera- ture water in order to provide the desired temperature in each room of the building by controlling the fan speed of its fan coil devices. The radiators circuit is meant to fed the classic radia- tors installed to sustain the heating action of the fan coils during winter. Finally, the air treating circuit is dedicated to the air quality control – both in terms of humidity and CO2 levels – of each room through the action of the two air handling units. 2.2 Performance analysis Different performance indexes have been defined so to describe the building control performances currently obtai- ned over the analyzed building. Such performance indexes have been computed over March 2019 and over 13 monitored rooms considering the data collected during the active time of the building, i.e. between 7 a.m. to 7 p.m. The results are presented in υ Table 1 . For both the room temperature and the room CO2 levels, four indexes have been defined. First, the average value is defined for both the temperature and the CO2 levels as Tav and CO2 av respectively. Second, the frequency by which an excessive level of the monitored value is registered is defined as Freq overheat,av and Freq HighCO2,av . Third, the average of such excess is defined as T Overheat,av and CO2 HighCO2,av . Finally, the maximum level of the monitored value is defined as max(T) and max(CO2). Multiple conclusions can be drawn from such performance indexes. Some rooms – for example D25 and D33 – have registered an elevated average temperature over the analyzed month. An elevated frequency of overheating has been registered over all the monitored rooms, with some peaks that are dangerously close to 100%. The rooms associated with a higher overheating frequency are cor- related with the rooms associated to a higher average temperature. Some rooms have reached an excessively high value of maximum temperature reached. Three rooms – D11, D22 and D26 – have shown a complete failure of the CO2 monitoring system, since it was not possible to record any mea- surement related to the CO2 level con- trol. The corresponding indexes have Figure 1 - Building thermal network block diagram Table 1 - Building control performance indexes