State-of-the-art energetic rating methods for buildings typically focus on the building itself and do not consider the interaction between the building with its infrastructural environment. However, in the context of the Swiss Energy Strategy 2050, buildings will consume more decentrally produced electricity, i.e. electricity which is produced in the local grid environment. Furthermore, more devices that may impose a higher stress on the local distribution grid (e.g., photovoltaics, EV charging stations)will be installed in buildings. These aspects are not considered so far by building rating methods.
The rating method for buildings proposed here is able to rate the “grid friendliness” of a building in alow-voltage distribution grid. If the building relieves the grid load (e.g. reduces the load on cablesand/or transformers), its grid friendliness is rated positive. On the contrary (e.g. higher voltage by means of strong feed-in of electric power), the grid friendliness is rated negative. The proposed method quantifies the impacts of different input parameters (e.g. istalled PV power, battery capacity, consumption of heat pump) on defined parameters of the grid (e.g. voltage limits, cable andtransformer loading). All impacts are then summarized in the so-called grid friendliness of the building.
The rating of a building requires information about the basic building characteristics, the load management method and the scenario. The building to be rated is compared with the average reference building in the specific grid. In order to consider the future development of the reference building, three scenarios (“today”, “2035” and “2050”) were established within the framework of this project. They comprise an increasing penetration of heat pumps, electric vehicles, PV systems, battery storages and more energy-efficient households. The energy management methods investigated within the project are “reference control”, “optimization of self-consumption” and “power optimization”. The energy management method influences the impact of the building on the local distribution grid.
The new rating method has been developed and tested at the example of two different grids (Hirzbrunnen and VEiN). All buildings (family houses and apartment buildings) were parameterised; standard consumption/production profiles for household electricity, heat pumps, electric vehicles and PV systems were established for each scenario and each energy management method. By means of building and grid simulations, sensitivity coefficients have been identified for each case. The sensititity coefficients quantify the impact of a variation in an input parameter on the grid friendliness of the building. A test building shows for both networks that only the so-called power optimization has a positive effect on the grid for all scenarios and that a battery has a positive effect on all the parameters examined.
The ratings carried out in the two grids are considered plausible. However, with these results, the overall validity of the proposed rating method cannot yet be finally judged. For this, more simulations in a variety of grids and subsequent statistical data analysis are required. This procedure is feasible, but requires a high effort, in particular for the generation of grid- and building data. For the two considered grids, the effort required for data generation and simulations was high. In a further step, the generalization and simplification oft he proposed method can be investigated, in order to develop an easy-to-use tool for architects, builders and distribution grid operators.
