Forschungsprojekt - SLIM Semizentrale Lüftung und intelligentes Betriebsmonitoring; Teilbericht 2: Semizentrale Kompakteinheiten und modellprojektübergreifende Themen

Abstract

Sub-report 2 documents the work on implementing semi-centralized ventilation in the demonstration projects. It describes the development of the semi-central ventilation units as well as cross-project topics that form the basis for the demonstration projects. Since these topics serve as "support functions" for the demonstration projects, they are not directly related to one another; thus, sub-report 2 should be understood as a list and documentation of relevant topics. The report describes the design of the semi-centralized ventilation units by the HVAC equipment manufacturer HOWATHERM and the fan manufacturer ebm-papst. The semicentralized ventilation units (SZE) contain all components required to supply a zone, preinstalled: fan, silencer, dampers, filter (exhaust air), airflow measurement, sensors, and communication interface. The components are adapted to the specific requirements of the demonstration buildings, tested, and optimized. A key focus of the development is on optimizing fan efficiency and operating points, as well as on developing solutions with low installation heights. Extensive measurement systems are installed in the demonstration projects to analyse the operational behaviour of the semi-centralized ventilation system under real-world conditions. The adaptation of the HOWAMonitor monitoring software to the demonstration projects, as well as the weekly evaluation programmed by the University of Kassel, are documented. The total annualized cost method according to VDI 2067 is used to evaluate the economy of semi-centralized ventilation. The application of this method to the demonstration projects is described, and the procedure for analysing the sensitivity of various parameters to economic efficiency is explained. To quantify the fan power savings of semi-centralized ventilation for a specific project at an early planning stage, the sL-Tool (semi-centralized ventilation tool) is developed - a calculation tool that calculates the fan power requirement for three ventilation systems: constant air volume system (KVS), variabel air volume system with dampers (VSR), and semi-centralized ventilation (sL). When calculating pressure losses in the sL-Tool, the pressure losses of shut-off fans must be taken into account in certain configurations. To quantify these, ebm-papst conducted corresponding measurements on selected fans. Based on this, the University of Kassel developed an initial proposal for a calculation approach. Unlike CO2 sensors, VOC sensors can also detect pollution from building materials and furniture. The developed "VC-method" demonstrates a way to utilize VOC values via CO2 values. The VOC values can thus be interpreted as equivalent CO2 values and used for demand-based airflow control. Evaluating measurement data from the demonstration project Auefeldschule, CO2 values significantly below the outdoor air concentration were observed in the classrooms when the ventilation system was shut off. The timeline of the measurement data suggested that CO2 is absorbed by concrete components as part of a carbonation process. This effect is demonstrated through laboratory measurements using a fiber-cement ceiling panel. The approximate magnitude of CO2 absorption is quantified, and its relevance for demand-based airflow control is illustrated. A "minimum branch control approach" is being investigated as a method to further optimize semi-centralized ventilation, thereby reducing the number of semi-centralized fans. However, a metrological analysis at the HVAC test facility of the Department of Building Services Engineering at the University of Kassel makes it clear that omitting the semi-central fan in the minimum branch is only possible in specific system configurations. To introduce the concept of semi-centralized ventilation to a broad professional audience and communicate the results of the research project, numerous publications and events were organized during the project period. Key findings of the project are presented and summarized in the practical guide "Praxisleitfaden Semizentrale Lüftung". Additionally, the content of the research project is being integrated into the curriculum at the University of Kassel.