1  Database

1.1 Introduction

GBuildings is a GIS database, containing layers of information for the characterization of the territory from an energy perspective:

  • Building stock characterization
  • Endogenous resources and energy harvesting / conversion / storage potential
  • Meteorological conditions

This tool was developed within IPESE and initiated by Luc Girardin. The development of such framework allowing generation, cross-checking and aggregation of energy data at various spatial scales was motivated by several reasons:

  • Building energy data are dispersed in various existing files and databases;
  • Real measurement and physical parameters of urban energy systems are sparse;
  • Energy standards and building typification are well known but at building-level;
  • From the energy transition perspective, there is a need for a building-level to a district-level aggregation.

The structure of the software can be seen in Figure 1.1. It comprises a database, a python repository, and a file repository for the external data. An SQL database is divided into three schemes (numbers 1, 2, 3). Those schemes are constructed by collecting external data stored on a drive (4). Each database is related to a folder on the drive containing the input layers. Python methods are used to treat each input layer accordingly (5).

Figure 1.1: Description of the GBuildings framework.

GBuildings workflow..

As can be seen, Python is used to manipulate the database (read and update), through SQL requests, translated by SQLalchemy package.

1.2 Description of the layers

1.2.1 Aggregated

This layer is used to centralise and merge raw data from diffuse information. It starts with data available at the national scale (mandatory) and, if available, uses local data from the area of interest (cities or cantons often have data of their own).  Figure 1.2 sums up the minimum set of input layers used to construct a data set. In detail:

  • The RegBL is the Swiss federal register of housing and buildings. It catalogues information on buildings, housings and streets. The interest is in the buildings’ information, referenced by street addresses and linked to a Universally Unique Identifier (UUID), named EGID.
  • Cadaster refers to swissBuildings3D, a federal data set that describes buildings geometries in three dimensions, with a high degree of detail. It is constructed based on aerial photo-strips (“swissBUILDINGS3D 2.0. Federal Office of Topography Swisstopo” n.d.).
  • Sonnendach is a project conducted in Switzerland to build a “solar cadaster”. The data set references every roof and facade in Switzerland and estimates the solar potential and useful surface for each of them (Daniel Klauser 2016).
  • SIA 2024 and SIA 380/1 are standards. SIA 2024 is the standard for Space usage data for energy and building facilities (Brüttisellen-Zurich 2021), and SIA 380/1 is the standard for Heat requirements for heating (Brüttisellen-Zurich 2016). These two standards categorise buildings according to their usage: housing (collective or individual), administrative, school, etc., and define typical characteristics for each type of building. A surface normalises the data; the ERA for SIA 380/1 and the net floor area for SIA 2024.

Additionally, GBuildings uses meteorological data (external temperatures and solar irradiance) from Meteonorm (J. Remund 2003).

Figure 1.2: Input layers for the aggregated scheme (geographic and others). RegBL is the Swiss national register of housing and buildings. SwissBuildings3D is the national mapping of buildings, in 3 dimensions. Sonnendach is a national database that evaluates the solar potential for roofs and facades.

The following describes the tables and their fields.

buildings
Fields id_building id_building3D ID_class_380/1 ratio_380/1 standard_2024 transformer day_of_use_d capita_cap temperature_interior_C flow_fresh_air power_gain_intern_W_m2 flow_hotwater annual_simultaneity gas_grid area_facade_m2 area_footprint_m2 solar_gain_factor electrical_energy_kWh/y Geometry
Comments Building ID created in QBuildings UUID from 3D layer Building classes from SIA 380/1 Share of agglomerated EGID in the final building, by area SIA 2024 standard ID of the transformer to which the building is associated Number of days use for hotwater, from SIA 2024 Number of habitants, from standard of cap/m2 From SIA 380/1 Ventilation flow, from SIA 380/1 – From SIA 380/1 and SIA 385, in l/cap/d and l/m2 – True if connected to the gas grid Area of the facade, from envelope computation Area of the footprint, from envelope computation From SIA 2024 Electrical demand, from SIA 2024 Geometry object for GIS database, from envelope computation
buildings_RegBL
Fields egid id_building period class area_era_m2 area_net_floor_m2 is_hotwater_system source_heating source_hotwater Geometry
Comments EGID identifier from RegBL ID created in QBuildings Period of construction Class for buildings characterisation, adapted from RegBL classes Computed from footprint area and number of floor if not available – True if hot water is needed Energy carrier for heating (oil, gas, …) Energy carrier for hot water production (oil, gas, …) Geometry object, point corresponding to EGID
roofs
Fields id_roof egid id_building id_building3D roof_solar_area mean_annual_irradiance roof_annual_irradiance tilt azimuth Geometry
Comments UUID from Sonnendach EGID identifier ID created in QBuildings UUID from 3D Useful roof area In kWh/m2/y Total irradiance on the roof, in kWh/y In degree Orientation, in degree Geometry object, polygons
facades
Fields id_facade egid id_building id_building3D facade_solar_area mean_annual_irradiance facade_annual_irradiance azimuth Geometry
Comments UUID from Sonnenfassade EGID identifier ID created in QBuildings UUID from 3D Useful facade area In kWh/m2/y Total irradiance on the facade, in kWh/y Orientation, in degree Geometry object, lines
transformers
Fields id P_load Q_load id_HV id_EHV Geometry
Comments Transformer ID created in QBuildings Active power, in kW Reactive power, in kW ID of the High Voltage transformer to which it is linked ID of the Extra High Voltage transformer to which it is linked Geometry object, polygon

1.2.2 Processed

This layer computes the energy signature of the building, that is, its heating and cooling energy needs and the hot water energy need. The computation is based on a characterisation of the building envelope according to the building class (Residential, Industrial, etc.) and period (<1919, 1919-1930, etc.). This characterisation has been done on a building sample from Geneva in Girardin (2012). The thermal coefficients have been calculated using known heat demands and surfaces and crossed with temperature data. The data from the buildings tables and the RegBL are grouped, and the corresponding thermal coefficient for each building is identified so that the heating demand can be computed (using hourly temperature data). The SIA data’s ventilation losses, hot water demand, and waste production are also computed with the combined data. Finally, the solar gains are computed using hourly meteorological data over a year.

It is relevant to highlight that the Sonnendach and Sonnenfassade data have a shadow model.

The obtained tables for that layer are described hereafter.

buildings
Fields id_building x y z egid id_class ratio status transformer gas_grid capita_cap area_era_m2 area_net_floor_m2 area_roof_solar_m2 area_facade_m2 thermal_transmittance_signature_kW_m2_K thermal_specific_capacity_Wh_m2_K temperature_interior_C temperature_heating_supply_C temperature_heating_return_C temperature_cooling_supply_C temperature_cooling_return_C is_hotwater_system source_heating source_hotwater energy_heating_signature_kWh_y energy_cooling_signature_kWh_y energy_hotwater_signature_kWh_y energy_el_kWh_y geometry
Comments Building ID created in QBuildings x coordinate in EPSG:2056 y coordinate in EPSG:2056 z coordinate in EPSG:2056 Federal identifier Building classes from SIA 380/1 Share of agglomerated EGID in the final building, by area SIA 2024 standard Transformer to which the building is associated True if connected to the gas grid Number of habitants, from standard of cap/m2 Energy reference area Area of the floor Roof area available for solar installations Area of the facade, from envelope computation U heating coefficient of the building Inertia of the building against thermal fluctuations Demand temperature – – – – True if hot water is needed Energy carrier for heating (oil, gas, …) Energy carrier for hot water production (oil, gas, …) Yearly SH demand Yearly cooling demand Yearly DHW demand Electrical demand, from SIA 2024 Geometry object for GIS database, from envelope computation
roofs
Fields id_roof egid id_building area_roof_solar_m2 mean_annual_irr_kWh_m2_y roof_annual_irr_kWh_y tilt azimuth Unnamed Geometry
Comments UUID from Sonnendach EGID identifier ID created in QBuildings Useful roof area In kWh/m2/y Total irradiance on the roof, in kWh/y In degree Orientation, in degree - Geometry object, polygons
facades
Fields id_facade egid id_building area_facade_solar_m2 mean_annual_irr_kWh_m2_y facade_annual_irr_kWh_y azimuth Geometry
Comments UUID from Sonnenfassade EGID identifier ID created in QBuildings Useful facade area In kWh/m2/y Total irradiance on the roof, in kWh/y Orientation, in degree Geometry object, lines
transformers
Fields id P_load Q_load id_HV id_EHV Geometry
Comments Transformer ID created in QBuildings Active power, in kW Reactive power, in kW ID of the High Voltage transformer to which it is linked ID of the Extra High Voltage transformer to which it is linked Geometry object, polygon

1.2.3 Smoothed

The data aggregation from various layers and the computation of new data may have created some extreme values. The data set is smoothed so that the outliers are removed.