Determining primary energy and CO2 reduction potentials of the German residential building stock through retrofit application of Building Automation Systems

Abstract

The 2015 climate summit in Paris has shown the dedication of countries all over the world to prevent “dangerous anthropogenic interference with the climate system”, [13]. The decision has been made, that exceeding the limit of a 2 degree Celsius increase in average world temperature compared to 1990 levels has to be avoided. Germany has been on the front of reducing its carbon footprint with its ’Energiewende’. The reduction of the energy consumption in the residential building sector plays a vital role in the country’s policies, as the residential building accounts for 26 % of the final energy consumption [42]. The goal of the TABULA project is to categorise the residential building stock, [47]. This research uses the TABULA project to determine the potential energy savings and corresponding CO2 emission reductions as a result of retrofit application of building automation systems in single family houses (SFH). Building automation systems (BAS), and in particular automatic regulating heating systems in residential homes could play a role. In this research a Modelica [60] based residential building model (RBM) has been developed to simulate the automatic regulation of a central heating system in SFHs. Two BAS scenarios are considered and applied to three Stand Alone Houses (SAHs). The imple- mentation of a time schedule thermostat that automatically reduces the set temperature when the residents are not occupying the building, and a self regulating thermostat valve that reduces the heat transmission in the room during manual ventilation over the windows. Implementing scenario 1 BAS for the SAHs would lead to an annual final energy reduction of 10 % for SAH 1, 11 % for SAH 2 and 14 % for SAH 3. The corresponding annual primary energy reduction on the German building stock level results to 58 PJ. This would lead to a reduction of the CO2 emissions by 3.1 Mt CO2 on yearly basis. The RBM has a dual functionality of assessing both the indoor climate conditions over the course of a year as well as the annual final energy consumption for space heating. Regulating the indoor set temperature requires a relatively high load during reheating periods compared to constant operation. The research shows the importance of a sufficient nominal load of the heating system to ensure the thermal comfort of the residents in winter. The annual final energy saving potential for scenario 2 BAS (self regulation thermostat valves) in SAH 3 is 4 %, under minimal ventilation conditions. However, the results of the RBM have shown that different ventilation rates could influence this result significantly. Further simulations with the RBM could extend the results here to all SFHs and determine their combined potential in the future.