The building sector accounts for almost 1/3 of the global final energy consumption, which is mainly made up of heating and cooling, as well as domestic hot water heating, lighting and household appliances. Due to global warming, the energy demand in buildings for heating will decrease, while that for cooling will increase in future (V. Ciancio et al., Sustainable Cities and Society 60, 102213 (2020)). Energy-saving ventilative cooling strategies like e.g. night cooling or hybrid ventilation in mixed-mode buildings therefore will be favourable compared to conventional heating, ventilation and air conditioning (HVAC) systems (L.L. Gomis et al., Energy and Buildings 231, 110597 (2021)).

Our research focuses on evaluating the effectiveness of automated, window-integrated ventilation systems compared to conventional ventilation and air conditioning systems for thermal control during summertime. We use two floors of an office building as a real laboratory for this purpose. Extensive data is collected via KNX sensors installed in the building. The study evaluates scenarios with manual and controlled natural window ventilation, decentralised window-integrated mechanical systems with heat recovery and combinations of all of them. The accuracy of the KNX sensors is checked with the help of laboratory measuring devices.

By connecting to a robust database, we capture detailed environmental metrics including temperature, humidity and CO2 levels, and other parameters such as user presence. Statistical and AI-supported analyses are used to determine the comfort level, user acceptance, energy requirements, CO2 emissions and economic costs for different scenarios. The results are compared with established building performance simulation tools such as EnergyPlus or IDA ICE.

Through detailed analyses and simulations, including user behaviour and the influence of user-specific conditions, our comprehensive approach will provide a better understanding on the optimal dimensioning, configuration and operation of natural, mechanical and hybrid window-integrated ventilation systems, improving operational efficiency in terms of cycles and running times. The study emphasises the need for sensor-based parameter recording to improve the accuracy of demand forecasts and thus support the efficient and sustainable use of energy resources and provides actionable recommendations for optimizing summer thermal control through automated, window-integrated solutions.

Das zentrale Ziel eines Home-Energy-Management-System (HEMS) besteht darin, den Ladevorgang von Elektrofahrzeugen sowie den Betrieb von Wärmepumpen und Heizstäben (Power-to-Heat) in Kombination mit elektrischen und thermischen Speichern zeitlich zu flexibilisieren. Auf der einen Seite ermöglicht die Flexibilisierung durch ein HEMS einen kostenoptimierten Betrieb durch die Erhöhung des Eigenverbrauchs der Photovoltaikanlage (PV-Anlage) sowie von dynamischen Stromtarifen. Auf der anderen Seite besteht die Notwendigkeit flexible Verbraucher, sogenannte „steuerbare Verbrauchseinrichtungen“ (SteuVE), und zukünftig PV-Anlagen durch ein HEMS in das Stromnetz zu integrieren. Jedoch gibt es derzeit keine umfassende Marktübersicht beziehungsweise Markttransparenz.

Municipal utilities (so-called Stadtwerke) play a crucial role in terms of the decentral Energiewende in Germany. The national way to accomplish the energy transition with a massive expansion of renewables requires local actors to participate actively. Thus, we developed a decarbonization strategy to supply a 12.000+ municipality CO2-neutral till 2035. This considered that the influence of the municipal utility is limited to its own electricity and natural gas grid as well as municipal buildings and vehicles.

Our study focused on the optimal expansion of sustainable energy generation coupled with short- and long-term storage options and transformation of consumption (mobility, power-to-heat, power-to-gas) of the existing local distribution grids. We aimed for a high autarky respecting long-term economic efficiency and high self-consumption of renewables. Natural gas should be replaced by alternatives as far as economically possible.

Energy consumption was determined and separated into domestic, commercial, and industrial and together with hourly generation profiles from existing renewables used to remodel the known annual consumption. Likewise, the hourly generation profiles from existing renewables were considered. The resulting degree of self-sufficiency (e.g., physical autarky) and annual share of renewable energy (accounting self-consumption) was calculated.

From this status quo, we developed future scenarios to answer the following questions:

·         What impact will the transformation to power-to-heat and electromobility have on the electricity demand up to 2035?

·         How do the parameters self-consumption and self-sufficiency behave for the respective expansion of the technologies PV systems, wind turbines and battery storages?

·         What is the techno-economic optimal combination of PV systems, wind energy systems and battery storage and what is the potential for hydrogen?

·         In what way does the injection of biogas and hydrogen affect the electricity and natural gas grids?

Based on the load and generation profiles, we have adjusted the type and scope of the technologies used. Thereby, the local conditions were again considered to only implement feasible concepts. A techno-economic analysis was carried out to plan an optimal transformation.